Resin-Socketed Termination of Offshore Wire Ropes · Resin-Socketed Termination of Offshore Wire...

OFFSHORE TECHNOLOGYREPORT - OTO 2000 069

Resin-Socketed Terminationof Offshore Wire Ropes

Date of Issue: September 2000 Project number 3596

This report is made available by the Health and Safety Executive aspart of a series of reports of work which has been supported by fundsprovided by the Executive. Neither the Executive, nor thecontractors concerned assume any liability for the reports nor do theynecessarily reflect the views or policy of the Executive.

Resin-Socketed Termination of Offshore Wire Ropes

Prepared by

Health and Safety Laboratory

Summary

There have been a number of incidents in recent years involving the failure of resin-socketed wire ropeterminations (commonly known as resin cappings) on cables which were being used for mooringfloating offshore installations. Subsequent investigation by HSE’s Offshore Safety Division (OSD)involved the making up of factory assembled samples, under controlled conditions, which failed at loadsof up to 50% below the specified breaking load limit for the ropes. These samples were made up bytwo different manufacturers who utilised their normal procedures and site personnel. Since tetheredoffshore installations are becoming more prevalent, OSD are concerned about the integrity ofresin-terminated sockets, particularly as regards the procedures used in their production and wherethese are made up in the hazardous offshore environment.

Objectives

This project is intended to identify the main parameters that affect the integrity of a resin-socketedterminations for 76 mm diameter stranded mooring rope which is typically used for this type ofapplication (this is the diameter of the ropes that failed) and additionally to investigate whether sizeeffects have a significant influence on the integrity of rope terminations. Parameters to be investigatedwere:

w poor brush configuration;w no release agent on the socket;w Poor or inadequate cleaning of the rope brush;w poor or inadequate resin mixing techniques;w poor or inadequate resin pouring techniques;w accelerated curing times when using accelerator packs at low temperatures;w size effects by comparison of 76 mm, 52 mm and 32 mm diameter rope terminations.

Primary outputs for the project are the production of a guide to making good terminations and toprovide guidance on acceptance and rejections criteria for the inspection of the process of making resinterminations.

Main Findings

1 HSL have had no difficulty in producing good wire rope terminations on 76 mm stranded wirerope provided the long established procedure for doing so were followed. The procedure usedby HSL has been set out and illustrated in this report and a general procedure, highlightinggood and poor practice, is included as Annex 1.

2 The most important factor in ensuring a satisfactory wire rope termination was found to be thecleaning of the wire rope brush. The rope dressing must be fully removed, particularly close tothe root of the brush at its narrow end. The use of steam cleaning is recommended as a finalstage in the cleaning process to remove any residual solvent or cleaning agent.

3 Adherence to the procedure is particularly important at low temperatures (below 10OC) andwhen accelerators are added to reduce curing times for the resin. The resin mix under theseconditions becomes thicker at low temperatures and it becomes more difficult to ensure that asatisfactory resin mix reaches into small spaces at the root of the brush. The making of wirerope terminations in low temperature conditions should be avoided if possible.

4 Unsatisfactory cleaning of the brushed wires consistently caused termination failures at loadsbelow the minimum breaking load for the 76 mm diameter rope. At 52 mm and 32 mm rope

HEALTH AND SAFETY LABORATORYAn agency of the Health and Safety Executive

diameters, failures still occurred but the risk of the termination failing before the rope itself waslower. It is considered that the most likely cause of this difference was the thicker ropedressing used on the larger diameter ropes, although size effects cannot be ruled out. At thesmaller rope sizes, low temperatures increased the likelihood of termination failure.

5 Poor brush, lack of release agent, poor resin mixing and poor pouring techniques did notproduce termination failures when introduced as single faults or in combination at roomtemperatures. A poor brush can, however, make cleaning of the brush more difficult and,because of this, we consider it an important step in the procedure. It is also important to followthe procedure for mixing and pouring the resin, particularly at low temperatures when the resinbecomes thicker, making penetration to the root of the brush more difficult. No evidence wasfound to substantiate the theory that the use of release agent affected the ability of the resincone to bed into the cast sockets and it is concluded that this step could be safely omitted fromthe procedure for terminating wire ropes with cast sockets.

6 In 5 cases from a total of 23 tests, the 76 mm diameter rope broke at a load below themanufacturer’s minimum breaking load (MBL). In all 5 cases, the applied load was in excessof 97% of the minimum breaking load and was held for up to 3 minutes 20 seconds before therope broke. Tests on the 76 mm were also characterised by loud cracks during the loading ofthe rope at loads below the MBL. These were individual wire breaks, which did not occur withthe same frequency in tests with the lower diameter ropes. The pattern of failure initiallyappeared to indicate that the 1770 grade rope was losing strength with time but it was alsoconsidered that the ratio of sample length to diameter was low (33 although greater than 30, theminimum value specified in BS 301: Part 1: 1987) and that the MBL was 98% of the actualbreaking load, giving a relatively low margin. It is therefore possible that the MBL for thisrope had been set at a level which is very close to the actual breaking load and that the MBLmay fall within the range of actual breaking loads from a series of breaking load tests.


14Tests at low temperature, brush not cleaned5.3

13Brush not cleaned5.2

13The combination of bad resin mixture, poor pouring techniques and no releaseagent

5.1

13TESTS AT SMALLER SCALE5.

12Brush not cleaned, no release agent4.8

12Bad resin mixture, poor pouring and no release agent4.7

11Low temperatures4.6

10Poor pouring techniques4.5

10Bad resin mix4.4

8No release agent in the socket4.3

7Brush not cleaned4.2

6Poor brush preparation4.1

6THE TEST PROGRAMME AND RESULTS FOR 76MM WIRE ROPES4.

6Dismantling the clamps and servings3.6

5Mixing and pouring the resin3.5

4Positioning and aligning the brush and socket3.4

4Preparing and cleaning the brush3.3

3Preparing the rope and socket3.2

2Equipment list3.1

2PROCEDURE USED FOR MAKING GOOD ROPE TERMINATIONS3.

1THE WORK PROGRAMME2.

1INTRODUCTION1.

Page

Contents


19REFERENCES

18CONCLUSIONS8.

17DISCUSSION7.

15APPARENT DETERIORATION IN STRENGTH OF THE 76MM 1770GRADE GALVANISED WIRE ROPE

6.


1. INTRODUCTION

There have been a number of incidents in recent years involving the failure of resin-socketed wire ropeterminations (commonly known as resin cappings) on cables which were being used for mooringfloating offshore installations. Subsequent investigation by HSE’s Offshore Safety Division (OSD)involved the making up of factory assembled samples, under controlled conditions, which failed at loadsof up to 50% below the specified breaking load limit for the ropes. These samples were made up bytwo different manufacturers who utilised their normal procedures and site personnel. Since tetheredoffshore installations are becoming more prevalent, OSD are concerned about the integrity ofresin-terminated sockets, particularly as regards the procedures used in their production and wherethese are made up in the hazardous offshore environment.

This project is intended to identify the main parameters that affect the integrity of resin-socketedterminations for 76 mm diameter stranded mooring rope typically used in this type of application (thisis the diameter of the ropes that failed) and additionally to investigate whether size effects have asignificant influence on the integrity of rope terminations. Parameters to be investigated were:

w poor brush configuration;

w no release agent on the socket;

w poor or inadequate cleaning of the rope brush;

w poor or inadequate resin mixing techniques;

w poor or inadequate resin pouring techniques;

w accelerated curing times when using accelerator packs at low temperatures;

w size effects by comparison of 76 mm, 52 mm and 32 mm diameter rope terminations.

Primary outputs for the project are the production of a guide to making good terminations and toprovide guidance on acceptance and rejection criteria for the inspection of the process of making resinterminations.

2. THE WORK PROGRAMME

The initial programme envisaged the production of five 76 rope samples for each the followingparameters for poor rope capping techniques

w poor brush configuration

w no release agent

w poor cleaning of the brush

w poor resin mix

w poor pouring techniques

w low temperatures/accelerated curing


1

In addition, five good 76 mm cappings would be made up as controls for comparison. To investigatesize effects, five 52 mm samples and five 32 mm samples would be made up with the details of thesetests being agreed when the 76 mm sample tests were complete. In total, 45 tests were planned, 35 with76 mm rope samples and 5 each of the smaller sizes.

One end of each sample was made up as a “good” end. This end was cast to fit split cones in the fixedend of HSL’s 4000 kN tensile test machine, which was to be used to test the samples. The other end ofthe sample was made up with one of the defects listed above. Except for tests done at deliberately lowtemperatures, cappings were prepared indoors, using rope samples, sockets and materials which hadbeen stored indoors. As a result, all these items could be expected to have experienced ambienttemperatures between 15OC and 22OC.

As the test programme developed, it became clear that some of the defects did not weaken the cappingsufficiently for it to fail at a load below the minimum breaking load of the rope (or the 4000 kNcapacity of the test machine, see next paragraph). As a result, it was agreed that, in these cases, onlythree tests per defect type would be carried out. This would allow the investigation of somecombinations of defects to determine if those combinations led to weakening of the capping.

A further variation was that the 76 mm rope, which had been expected to have a minimum breakingload below the 4000 kN (408 tons) capacity of the test machine, had a stated minimum breaking load of420 tons (4120 kN). This difference was not considered to be significant for the purpose of these testsand it was agreed that survival of a rope sample with a 4000 kN load held for a period of 10 minuteswas sufficient to test the resin cappings. In some tests, the rope itself failed at this load. Thisunexpected finding is discussed later in the report.

3. PROCEDURE USED FOR MAKING GOOD ROPE TERMINATIONS

This section of the report details the procedures used by HSL for making good resin-socketedterminations for wire ropes. It is based on procedures used over many years for producing wire ropetest samples within HSL’s engineering workshop. Cordon (1995) describes the development of resincappings for the UK mining industry, when much of HSL’s work was carried out. All of the samplesmade over the years have been subjected to tensile testing, fatigue testing or impact testing and in allcases the wire rope has failed rather than the rope termination. It should be stressed, however, that thecapping process is normally carried out indoors and at temperatures no lower than 15OC. This may notbe possible in some offshore applications and, again, this is dealt with later in the report.

3.1 Equipment list

The following is a list of equipment and materials needed in order to produce a resin-socketedtermination of a wire rope:

Wire ropeWire rope socketRope socket rig and fittingsRope cutter/slitting discSteel tube for rope strandsSteel tube for rope wiresSplit sleeve for centralising rope in socketTirfor/winch (for big ropes only)Serving mallet/machineReel of soft iron serving wire (diameter of wire to match rope size)Socket alignment tool


2

Plastic sheetRubber “O” ringHigh pressure steam cleaner with water soluble detergentWirelock resin kit/s - volume to match conical bore of rope socket, including silicone grease, stirrer andplasticineWorkshop hand tools including prybars, and tubes to fit strands and wiresStandard workshop protective clothing

3.2 Preparing the rope and socket

Uncoil new rope from drum.

Identify and mark the cutting point.

Support the rope horizontally between two rope clamps or similar so that the cutting point is midwaybetween the vices and the rope does not sag. Remove any excess rope dressing from the part of therope to be served.

Using the serving mallet, apply two soft iron servings, one at each side of the cutting point, as shown inFigure 1. The length of these two servings must be at least equal to the rope diameter. The gapbetween the two servings must be just wide enough to allow the rope to be cut without disturbing thetwo servings.

Apply one long serving at the side of the rope to be brushed. The length of this serving must be at least3 times the rope diameter and must be applied at a distance equal to the length of the rope socketbasket, minus, half the rope diameter, measured from the cutting point. Prior to this serving, shortlengths of plasticine must be applied in the valleys between the strands, Figure 2, over a distance ofapproximately the rope diameter and half the diameter from the end of this serving nearest to the cuttingpoint. This will seal the spaces/cavities between the strands underneath the serving which will help toeliminate possible resin leakage during the pouring process. Temporary rope clamps can be fitted ateach side of the cutting point prior to cutting. These are normally used if single stranded serving wireis used.

Place the rope on the ground on “vee” block supports at each side of the cutting point. Cut the ropesquarely using a slitting disc or similar equipment, as shown in Figure 3. Flame cutting must not beused as this is likely to affect the mechanical properties of the steel wires.

Remove rope clamps.

Examine the rope socket to ensure the interior of the socket is clean and free of dirt etc. Roughness ofthe inside surface is not important provided that there are no obstructions to prevent the resin cone frombedding into the socket when a load is applied to the termination. If the socket has been usedpreviously then any resin adhering to the socket wall should be removed. The taper bore of the socketmust be concentric within the socket and, in particular, the wall thickness should be the same all aroundthe socket periphery. Physical damage or non-concentricity of the socket can lead to failure of thetermination under load. Such sockets must never be used.

Secure the socket in position on the rope rig, Figure 4. The rope rig serves as a secure brushing benchand helps to eliminate the manual handling of heavy rope sockets. It also provides accurate axialalignment between rope and socket and it can be elevated and locked vertically to enable the casting tobe carried out correctly.


3

Apply a light smearing of silicon release agent, supplied with the resin kit, to the inside of the ropesocket bore.

Apply plastic covering over the portion of rope to be threaded through socket. Secure it with maskingtape, Figure 5. This will prevent contamination of the socket bore when the rope is threaded throughthe socket.

Push the “O” ring onto rope over plastic covering and slide it on the rope so that it will be clear of thebrushing. This “O” ring will later be used as a seal at the socket neck.

Thread the served end of the rope through the socket so that the end to be brushed is clear of the socket.Fasten the rope to the rope rig using the clamps provided, Figure 6. Ensure that the end clamp ispositioned exactly at the point on the rope to which the wires will be unlayed.

3.3 Preparing and cleaning the brush

Adjust the rig to desired position for brushing. Brushing is best carried out with the rig set at an anglemost convenient to the ropeman.

Remove and discard the short serving on the end of the rope.

Using the large steel tube, unwind and open out each rope strand, in turn, to form a basic brush as inFigure 7. A flat blade is used to prise out each strand from the cluster before the tube is pushed onover the strand. Great care must be taken when carrying out this operation as the strands are springywhen they are bent back and any slippage or accidental release of tube is a potential hazard to personsstanding nearby.

Starting with the IWRC, and using the small steel tube, gently ease out of lay and unwind eachindividual wire, in turn, to form a complete brush. As the wires are opened out they should be brushedwith paraffin to remove and/or loosen the rope dressing, Figure 8. Each wire must be unwound downto the serving whilst still retaining its helical shape. Do not attempt to straighten the wires. Do notrepeatedly bend wires to achieve correct position as this can seriously weaken them. Over bending,nicking, and twisting of the wires must be avoided as this could later cause fatigue failure of the wiresduring service. The finished brush, Figure 9, must be as concentric as possible and the wires must beas evenly distributed as possible.

Adjust the rope rig so that the brush is pointing downwards to allow the cleaning fluids to drain away.Cleaning fluid must not be allowed to penetrate down into the rope underneath the long serving.

Using the high pressure steam cleaner, Figure 10, thoroughly clean the brush using the detergent spray.Finally clean the brush with pure water to rinse off the degreasing agent or detergent. Allow the cleanbrush to drip dry whilst it is still pointing downwards, Figure 11.

Carry out a visual check of the brush to ensure that the wires are clean and that no lubricant or dressingis present on the brushed wires. Check that the rope dressing is visible under the serving, Figure 12.

3.4 Positioning and aligning the brush and socket

Measure and mark on the serving a distance of half the rope diameter measured from the inner end ofthe long serving, Figure 13. Discard the plastic sheet covering which was previously placed over rope.


4

Position the socket in the rope rig, using socket spacers if needed, to align the socket with the ropeclamps.

Undo the clamps on the rope rig and pull the brush into the socket so that the small end of the socket isin line with the marking on the serving. Ensure that the ends of the brushed wires protrudeapproximately 3 mm above the end of the big end of the socket. If all three servings have beenpositioned accurately, everything should fit correctly, Figure 14. The objective is to achieve a length ofhalf the rope diameter inside the socket neck. This will ensure proper support of the wires at the root ofthe brush and help to protect them from fatigue damage. It is important to minimise the rotation of thesocket to prevent the silicon from inside the socket being scraped off onto the freshly cleaned wires.

Using the split sleeve, Figure 15, align the rope so that it is concentric inside the socket neck. Furtheraxial alignment of the rope will be given by the seating clamp positions on the rope rig when the rope isreclamped.

Reclamp the rope on the rig ensuring all the clamps are tight. Remove the socket alignment tool.

Slide the “O” ring into position so that it fills the annular gap between the rope and the socket neck,Figure 16.

Seal the neck of the socket by applying plasticine over the top of the “O” ring, Figure 17.

Adjust the rope rig so that the rope socket is vertical, Figure 18.

3.5 Mixing and pouring the resin

Detailed information on the use of the resin kits can be found in the Wirelock Technical Data Manualand in the information leaflet which accompanies each kit.

Consider the temperatures of the rope, socket and resin kit. Are they the same or is any of these likelyto be at a temperature below 10OC. Ideally, all components should be above this temperature, if notthen the use of accelerator packs may need to be considered. The easiest way to use these is to ensurethat all components are at the same temperature and to follow the resin kit suppliers instructions. Ifthere is any doubt as to the component temperatures, then they should be measured.

Examine the resin kit to be used, Figure 19. Each kit consists of two containers one with liquid resinand one with powder together with a stirrer, silicon grease release agent and plasticine. These aresupplied in an outer container which is used for mixing. Booster packs are available separately and aresized to match to the volume of the resin kits. Check that the resin kit is not out of date. Out of datekits must be discarded. Check that the colour of the powder is off-white and the resin is free flowing.Kits can be added together to give the required volume. Always use the full container contents, neveruse part container contents.

Wear eye protection and a dust mask for mixing the resin. Mix the liquid resin and powder in thecontainer supplied with the resin kit. Stir for approximately 2 minutes whilst checking the viscosityand colour of the mixture. For temperatures between 2OC and - 8OC one booster pack must be addedand between 2OC and - 3OC two booster packs must be added.

Pour the mixture into the socket immediately, ensuring that the mixture is poured at one position only,as in Figure 20. Any movement is likely to introduce unwanted air into the mixture inside the socket.Fill the socket up until the level of the fluid is flush with the end of the socket. Finally, using a straightpiece of wire of similar tool, broddle the mixture inside the socket basket to remove any trapped air,


5

Figure 21. The socket may be topped up as necessary as the resin settles. Any leakages must bestopped immediately by simply applying further plasticine around the socket neck as necessary. Atroom temperature, gelling will normally take place in approximately 15 to 20 minutes. The mixturewill be fully set after approximately 1 hour. At low temperatures the gelling and setting may take muchlonger and full setting can take as long as 2 hours even when booster kits are used.

When the resin has hardened, using a sharp instrument, carry out a scratch test by scoring the set resinin the end of the socket, Figure 22. This should leave a shallow scratch mark indicating the resin isfully set. The final colour of the resin is likely to be either bluish green, Figure 23, or sandy brown,Figure 24, depending on the temperatures reached during curing. A sandy colour indicates a hottercure than the bluish green colour.

3.6 Dismantling the clamps and servings

Remove the plasticine and “O” ring from the socket neck. Examine the completed socket terminationfor any defects.

Unwind the long serving wire and cut it off as close as possible to the end of the socket neck, Figure 25.

Remove the plasticine from between the rope strands and scrape off any leakage resin compound.

Finally relubricate the rope with rope dressing taking care to seal the neck of the socket.

Remove the complete socket termination from the rope rig.

Because the rope samples will be tested within a few days of being made, bedding in of the sockets witha pre-load is not necessary.

One output of this project is a general procedure for making good resin terminations for stranded wireropes. This is included at Annex 1.

4. THE TEST PROGRAMME AND RESULTS FOR 76 MM WIRE ROPES

A full table of results for the project is included at Annex 2. Extracts from this table have been used toillustrate the effects of specific parameters on the strength of wire rope terminations. Details of therope and other materials and equipment used in the tests are included at Annex 3.

4.1 Poor brush preparation

In order to form a good brush, it is necessary to remove the serving from the end of the rope and toseparate out the individual wires so that the resin, which will form the termination, will penetrate intothe spaces between the wires in order to form a solid resin cone. It is also recommended that the wiresshould not be bent, twisted or straightened to avoid deformed wires which may later break in fatigueduring service. For the purpose of this project, a poor brush is taken to be one where the wires are notfully separated out, as shown in Figure 26. It should be noted that a poor brush is also more difficult toclean, particularly at the root of the brush where the wires of individual strands are still bunchedtogether.

Three tests were carried out on 76 mm rope with a bad brush, as detailed in Table 1. In all 3 tests thesocket survived the maximum machine load of 4000 kN for a period of 10 minutes. Individual wirebreaks were heard in each of the tests, both the tests with good samples and with bad brush. Thepossible significance of these is discussed in Section 6.


6

Table 1 Tests with bad brush

4,000Bad brush13-05-9876-054,000Bad brush12-05-9876-044,000Bad brush11-05-9876-034,000Good17-04-9876-024,000Good06-04-9876-01

Test load (kN)Socket conditionDateTest No

In the first column of this and other Tables in this report, the test number is preceded by the ropediameter in millimetres. Good tests refer to samples made to the normal procedure and are included ascontrols for comparison.

It was concluded that bad brushing of the rope alone was not sufficient to reduce the strength of thetermination below that of the rope itself.

4.2 Brush not cleaned

These tests were initially carried out on the 76 mm rope and, in this Section of the report, only thesetests are considered. The rope dressing on the 76 mm rope was thick and heavy, as illustrated in Figure9 and some rope dressing was necessarily removed during brushing of the rope end. Large lumps of thedressing were removed using a brush and cold paraffin but the remaining rope dressing was stillsubstantial. The rope was terminated using the normal procedures with the dressing remaining asshown in Figure 9. The test results are shown in Table 2.

All the terminations with the brush not cleaned failed at loads significantly below the 4120 kNminimum breaking load (MBL) of the rope. The range of failure loads was very wide, the lowest being1543 kN, the highest 3513 kN and the mean of 5 tests being 2590 kN or 63% of the minimum breakingload of the rope.

Table 2 Tests on 76 mm rope with brush not cleaned

4,000Good28-09-9876-20(failed3,083Brush not cleaned15-07-9876-11(failed)2,162Brush not cleaned23-06-9876-09(failed)3,513Brush not cleaned22-06-9876-08(failed)2,691Brush not cleaned08-06-9876-07(failed)1,543Brush not cleaned05-06-9876-06

4,000Good17-04-9876-024,000Good06-04-9876-01


All the failures were of a similar nature and the following features were noted and are illustrated inFigures 27 to 30.

a) the resin in the socket neck had crumbled and fragmented;

b) there were numerous broken wires within the socket which appeared to be mainly concentratedaround the edges of the resin cone, ie, they were mainly the outer wires of the brush;


7

c) the wide end of the resin cone was still intact and the wires had pulled out of the resin as therope pulled out of the socket;

d) the sides of the resin cone had largely survived and broken wires were still embedded in theresin;

e) the central core of the resin cone and the narrow end of the cone had crumbled and werepresumed to form the dust and debris within the remainder of the resin cone.

It is considered that the presence of the rope dressing acts to degrade the strength of the resin throughbeing an extra component in the mixture. Failure of the resin to bond on the wires and the reduction infriction between the wires and the resin caused by the lubricating effect of the rope dressing may alsoallow relative movement when the load is applied, breaking down the resin as the load increases.Acting together, these factors make the narrow end of the resin cone weaker such that it cannotwithstand the normal compression forces being developed as the tensile load increases. The wires in thenarrow part of the cone will then be able to straighten and the tensile loads will transfer to the wider,back end of the cone. The wires then pull out of the wider end of the cone.

Bradon and Chaplin (to be published) have carried out finite element modelling of resin-socketed wirerope termination in tension. The model was validated against strain gauge measurements made duringthe testing of a good 76 mm rope sample in these tests. Bradon and Chaplin’s main finding is the back(wider) half of the resin cone in not subjected to compression forces when the cone is pulled into thetapered socket by tensile forces in the rope. Without this compression, the wires in the back of thesocket are held only by the bond between the wires and the resin and the friction forces between thewires and the uncompressed resin. Once the resin at the narrow part of the cone fails, the wires simplypull out of the wider part of the resin cone.

It is notable that, when good cones were examined after these tests, there was no evidence of resincrumbling at the narrow end of cones, see Figure 31, for example. The crumbling of resin is onlyassociated with a failure to properly clean the wire brush. Figures 32 and 33 are photographs of 2cones from terminations which failed in service in the off-shore industry. The terminations were onpendant ropes from a crane on the Santa Fe Monitor and failed in service on 30 June 1994. It can beseen that the loss of resin from the centre and narrower end of the resin cone is very similar, if lessextensive, than that seen in the HSL tests. The difference is one of degree only, in that the cleaning ofour samples was likely to have been poorer than that of the incident samples.

It follows from the observations that, when the brush is not adequately cleaned, the presence of the ropedressing, particularly at the narrow end of the cone, causes a reduction in the compressive strength ofthe resin such that it fails at applied tensile loads below the minimum breaking load of the rope. Oncethe load reaches a level at which the resin fails, the remaining part of the cone is not in sufficientcompression for the wires to be retained within the cone.

There are issues here which may merit further investigation including

a) the type of rope dressing and variations in its effect in the resin;

b) scaling issues, such as the effect of the volume of resin relative to wire surface area.

These are probably better addressed initially by small sample tests. Some work in this area has beendone with 52 mm and 32 mm wire ropes as part of this project.

4.3 No release agent in the socket


8

Release agent, supplied in the resin kits, is normally applied to the inside surface of sockets in order toreduce the risk of the resin cone bonding to the socket before the cone has been bedded in and to makethe cone easier to knock out if the socket is to be reused. With mining sockets, which have a machinedinner surface, this risk is well known and release agent is generally used. With cast sockets, as used inthe offshore industry, the inside surface of the socket is much rougher and more likely to becontaminated by dirt and or grease, making the risk of chemical bonding by the resin much lower. Toinvestigate whether release agent was effective when used on cast sockets, the tests in Table 3 wereconducted.

The rope samples were loaded as normal for these tests ie the load was increased linearly at a rate of800 kN/minute over a period of 5 minutes and then held at the peak load for a period of 10 minutes.There were no socket or capping failures and no significant difference between the tests with andwithout release agent. The rope sample in test 76-25 broke at a load below its minimum breaking load.The reasons for this are dealt with separately in Section 6.

Table 3 Tests without release agents

4000(rope broken)No release agent27-11-9876-254,000Good27-11-9876-244,000No release agent18-09-9876-174,000No release agent14-09-9876-154,000No release agent13-08-9876-144,000Good17-04-9876-024,000Good06-04-9876-01


To get information on the movement of the terminations within the socket, socket draw was measuredafter each of the tests where the 76 mm rope sample survived the test. For comparison, draw wasmeasured at the split cone end of each sample. Socket draw is defined as the mean movement of theresin capping relative to the socket during the test. Measurements were made to the nearest millimetre.In two tests, one within and one without release agent, socket draw was measured at 1000 kN intervalsas the load was applied. It was clear that socket draw was progressive and that there was no significantdifference between the tests.

Measurements at the split-cone end of the samples had a mean (of 15 measurements) of 12.1 mm with astandard deviation of 1.5 mm. 20 measurements at the socket end had a mean of 12.9 mm with astandard deviation of 3.7 mm. Draw on the 4 sockets without release agent was 16, 13, 12 and 9 mm,that is, not significantly different from the tests where release agent was used. The greater spread ofsocket draw measures when compared with draw on the machined split cones is thought to be due to theroughness of the surface of the sockets and the less controlled shape of the inside of the cast socketscompared with the machined surfaces of the split cones.


9

4.4 Bad resin mix

These tests were carried out at room temperature. The resin kit manufacturer recommends that thepowder and resin be mixed using a stirrer for a period of 2 minutes. For the purposes of these tests, abad mix was produced by stirring 2 or 3 times, sufficient to ensure that the powder was wetted by theresin but leaving a clearly inhomogeneous mixture of resin and powder. The mixture was pourednormally into the socket and the socket broddled using a stiff wire in order eliminate air pockets so faras possible. Table 4 shows the results of the tests. It was clear that poor resin mix alone would notcause the terminations to fail if they were prepared at room temperature.

Table 4 Tests with a bad resin mixture

4,000Poor resin mix21-07-9876-134,000Poor resin mix21-07-9876-124,000Poor resin mix09-07-9876-104,000Good17-04-9876-024,000Good06-04-9876-01


This conclusion is qualified because later tests carried out at low temperatures showed that the resinmix is much thicker as it nears the lower limits of its accepted temperature range. As a result, it is lesslikely that the pouring process and the movement of the mixture through the wires in the brush wouldaid mixing, as it may have done at room temperature where the resin mix is very thin.

4.5 Poor pouring techniques

It is normally recommended that the resin mix be poured slowly and steadily into one place in order toallow the mixture to spread through the socket cone whilst reducing the risk of trapping air. When thepouring is complete the resin is then broddled, using a vertical wire to encourage any trapped air tomove to the surface. For the purpose of these tests the resin was mixed normally but then pouredunevenly over the upper surface of the brush. Broddling was not carried out. Test results are shown inTable 5.

Table 5 Tests with poor pouring techniques

4,000Good28-05-9876-204,000Bad pouring23-05-9876-194,000Bad pouring18-09-9876-18

4000(rope broke)Bad pouring14-09-9876-164,000Good17-04-9876-024,000Good06-04-9876-01


It is clear that, at room temperature, poor pouring techniques alone would not cause the terminations tofail. Again this conclusion is qualified because later tests showed that the resin mix is much thicker asit nears the lower limits of its accepted temperature range. As a result, it is more likely that poorpouring techniques and no broddling would result in air spaces within the cone. However, there is nodirect evidence of this occurring in these tests.


10

4.6 Low temperatures

The original test programme called for low temperature tests on 76 mm rope samples. In order toachieve this, it was decided to pre-soak the brushed rope, the socket and the resin pack in a coldchamber in order to reduce their temperature. A target temperature of 3OC was chosen and it wasdecided to use 1 accelerator (or booster) pack. The starting temperature was therefore close to thelower temperature limit for a resin kit with 1 accelerator pack.

Once the sample had reached the target temperature, the socket was fitted with an insulating jacket andremoved from the cold chamber. It was necessary to do this because there was insufficient height in thecold chamber to hold the sample vertical for pouring of the resin. The external temperature of thesocket was monitored using a calibrated temperature probe. A typical experimental record is set outbelow.

10100Replaced in cold chamber995Resin set (resin brown)

7.570Resin gelled (resin blue)4.510Pour resin30Remove from cold chamber

Socket Temperature (OC)Time(mins)Action

It was clear that the normal setting time of the resin (20 minutes) was increased to well in excess of anhour. Once the socket warmed up to a temperature of 8 or 9OC, however, the centre of the resin surfacestarted to turn from blue to brown and the resin then cured rapidly. It is considered that the resin curedas a result of the increase in socket temperature and of the heat generated by its own reaction.

It was noted from these tests that the resin mix was considerably stiffer than the mix at roomtemperatures and that air bubbles took much longer to rise out of the poured resin. This suggests thatproper mixing of the resin and good pouring techniques may be more important for sockets made at lowtemperatures.

The rope samples were returned to the chamber and left for a period of 24 hours before testing. Thetemperature of the cold chamber was maintained between 3OC and 4OC. The time taken to remove thesample from the cold chamber and install it in the test machine was typically 50 minutes when thesocket temperature was typically 6OC. The tensile load was ramped from 0 to 4000 kN over a periodof 5 minutes after which the load was held for 10 minutes. After the tests, measured sockettemperatures were between 7OC and 8OC. The results are shown in Table 6.

Table 6 Low temperature tests with 76 mm wire rope.

4,000(rope broke)Low temperature15-01-9976-294,000(rope broke)Low temperature13-01-9976-28

4,000Low temperature12-01-9976-274,000Good28-09-9876-20


The low temperature cappings survived intact, despite the delayed curing of the resin. It appeared that,once the resin reached a temperature where curing could begin, it cured quickly as a result of the heatgenerated by its own reaction.

4.7 Bad resin mixture, poor pouring and no release agent.


11

Because of the lack of effect of some of the parameters on the strength of the resin terminations, it wasdecided to carry out tests with combinations of faults introduced during the capping process. Thesetests were therefore carried out with the resin poorly mixed, using poor pouring techniques and withoutrelease agent. The results are shown in Table 7.

It is clear that this combination of faults did not result in resin termination failures at room temperature.

Table 7 Tests with a combination of bad resin mix, bad pouring techniques and norelease agent

4,000Bad mix, bad pour norelease agent

26-01-9976-31

4,000Bad mix, bad pour norelease agent

21-01-9976-30

4,000 (rope broke)Bad mix, bad pour norelease agent

04-01-9976-264,000Good28-05-9876-20


4.8 Brush not cleaned, no release agent

The earlier findings that lack of release agent had no effect on the strength of the terminations was notexpected by HSL, although later contact with industry representatives suggests that this was known tothem. The combination of brush not cleaned and no release agent was therefore tested to determinewhether the lack of release agent would further reduce the breaking load of ropes with the brush notcleaned. The results are shown in Table 8, together with earlier results for tests with the brush notcleaned.

Table 8 Test results for brush not cleaned, no release agent

3,651 (Failed)Brush not cleaned, norelease agent

06-11-9876-23


22-10-9876-22


22-10-9876-214,000Good28-07-9876-20

3,083 (Failed)Brush not cleaned15-07-9876-112,162 (Failed)Brush not cleaned26-06-9876-093,873 (Failed)Brush not cleaned22-06-9876-082,691 (Failed)Brush not cleaned12-06-9876-071,543 (Failed)Brush not cleaned08-06-9876-06


The results suggest that the lack of release agent either had a beneficial effect, increasing the meanfailure load from 2590 kN to 3240kN or, more likely, that the range of failure loads is too wide for anydifference to be evident between tests with and without release agent.

5. TESTS AT SMALLER SCALE


12

Although the main thrust of this work was to look at the termination of 76 mm wire rope, the initialprogramme included a comparison of tests with rope terminations at 3 sizes: 76 mm, 52 mm and 32mm. At the conclusion of the tests on the 76 mm rope it was agreed that tests would be carried at the 3sizes under two conditions:-

a) the combination of bad resin mixture, poor pouring technique and no release agent;

b) brush not cleaned;

c) low temperatures tests, brush not cleaned on 32 mm rope.

5.1 The combination of bad resin mixture, poor pouring techniques and no release agent.

Table 9 shows the test results.

The smaller, 32 mm and 52 mm ropes were tested to destruction using a ramped increased load from 0to MBL over a period of 5 minutes. The 76 mm rope was tested to 4000 kN, where the load was heldfor 10 minutes.

The results show no termination failures in these tests. A feature of this comparison in that wires wereheard to break in all cones before the rope failed or the test was completed. It was notable that, withthe two smaller sized ropes, this only occurred at loads in excess of the rated minimum breaking load(MBL). For the 76 mm rope, broken wires were heard consistently at loads in excess of 3800 kNcompared to the (MBL) of 4120.

Table 9 Results of tests at 3 rope sizes with a contamination of bad mix, bad pourand no release agent.

790 (rope broke)71502-07-9952-37790 (rope broke)71501-07-9952-361,910(rope broke)1,70709-06-9952-351,940(rope broke)1,70718-05-9952-34

4,0004,12026-01-9976-314,0004,12021-01-9976-30

4,000 (rope broke)4,12004-01-9976-26

Test load (kN)Minimum breaking load ofrope (kN)

DateTest No

5.2 Brush not cleaned

Test results are shown in Table 10. It is immediately clear that, as size decreases the terminations areless likely to fail. All five samples at 76 mm size failed, plus 3 more at that size, reported in Section4.8, where the brush was not cleaned and release agent not used. At 52 mm size, 3 of 4 terminationsfailed. At 32 mm size only 1 of 4 terminations failed. There is a clear size effect here which gives agreater risk of termination failure for larger sized resin cappings.


13

Table 10 Results of tests at 3 rope sizes with brush not cleaned.

755 (rope broke)71512-11-9932-43775 (rope broke)71519-07-9932-42794 (rope broke)71519-07-9932-39

661 (failed)71514-07-9932-38989 (failed)1,70718-10-9952-41

1,027 (failed)1,70718-10-9952-401,380 (failed)1,70718-05-9952-34

1,917 (rope broke)1,70717-05-9952-333,083 (failed)4,12015-07-9876-112,162 (failed)4,12023-06-9876-093,513 (failed)4,12022-06-9876-082,691 (failed)4,12008-06-9876-071,543 (failed)4,12005-06-9876-06

Test load (kN)Minimum breaking load ofrope (kN)

DateTest No

5.3 Tests at low temperature, brush not cleaned

Five tests were carried out on samples using 32 mm diameter rope in which the combination of lowtemperature and brush not cleaned was examined. The results are shown in Table 11. The survival of3 from 4 samples at this size with the brush not cleaned but at normal temperatures was unexpectedand the addition of low temperatures, which may be more typical of a rope terminations made on anoffshore installation, was considered worthwhile. At this size, it was possible to pre-soak and constructthe termination entirely within the cold chamber and this was done. The rope, socket and resin kit werepre-soaked for a minimum of 24 hours at the target temperature and were left in the cold chamber for aminimum of 24 hours at the target temperature and were left in the cold chamber for a minimum of 24hours before the test was carried out. Two tests were carried out at 8OC, without accelerator, two testsat 3OC with one accelerator pack and one test at 3OC with one accelerator pack but with the brushcleaned. The latter test was a control.

The resin mix for the 3OC tests was very stiff, increasing the time needed to complete the pour. Theresin tended to fall intermittently rather than as a smooth stream. It was clear that great care is neededat these temperatures to ensure that the socket is completely filled with resin. The resin tookapproximately 2 hours to set after which it satisfactorily passed a scratch test. This is a very longsetting time for resin cappings, well beyond what we would recommend. Cordon (1999) suggests that,if curing times are long, then there is also a tendency for the silica sand in the resin to settle out, givinga transparent zone at the top of the socket. This could make the resin cone weaker at the root of thebrush if there is a high sand to resin mix. The set resin was blue-green, noticeably different from theusual sandy-brown colour at room temperature.

The resin mix for the 8OC tests was thinner than for the 3OC tests and it was able to be poured almostnormally. The resin took approximately 1 hour to set after which it passed the scratch test. Again, theset resin was blue-green in colour.


14

Table 11 Low temperature tests with brush not cleaned

485 (Failed)Brush not cleaned, lowtemperature 8OC

20.12.9932 - 48

715 (Failed)Brush not cleaned lowtemperature 8OC

20.12.9932 - 47

775 (Ropebroke)

Brush not cleaned lowtemperature 3OC

16.12.9932 - 46

670 (Failed)Brush not cleaned lowtemperature 3OC

16.12.9932 - 45

745 (Failed)Brush not cleaned, lowtemperature 3OC

15.12.9932 - 44

Test load(kN)

Socket conditionDateTest No

The minimum breaking load for the 32 mm rope is 715 kN. Only the rope in test 32-46 (lowtemperature only) broke in the middle of the test sample as would be expected if the termination did notfail. The wires in the socket of test 32-48 pulled out and was typical of other low load failures with thebrush not cleaned. The resin at the root of the brush was crushed and powdery and appeared to havefailed as a result compression and the pulling of the wires through the socket when the capping failed.

The remaining 3 failures, tests 32 - 44, 32 - 45 and 32 - 47 had 2 or 3 wire rope strands broken insidethe socket and the inner wire rope core plus 1 or 2 other strands broken outside the socket. In eachcase, the ends of the wires had pulled into the surface of the resin at the wide end of the socket andthere was evidence of powdery resin deposits inside the root of the brush. It was concluded that, inthese 3 tests, the strength of the resin had been reduced sufficiently by the low temperatures and therope dressing for the resin at the root of the brush for to crumble at the test loads. This would allowsome of the wires/strands to move within the resin cone and allow the forces to be redistributed,probably unevenly, between the wires and strands. As a result, wires and strands failed in tensionwithin the brush at loads below their normal breaking load. It should be noted that, of four 32 mm ropesamples which broke, 775 kN was the lowest failure load. Although tests 32 - 44 (745 kN) and 32 - 47(715 kN) are at or above the minimum breaking load for the rope of 715 kN, they are still considered tobe termination failures.

6. APPARENT DETERIORATION IN STRENGTH OF THE 76 mm 1770GRADE GALVANISED WIRE ROPE

The 76 mm, 6 x 36 IWRC rope, constructed of 1770 grade galvanised wire, had a minimum breakingload of 4120 kN (420 t). It was manufactured on 12/07/97 and tested on the same date to have anactual breaking load of 4208 kN (429 t).

A total of 23 tests were carried out with 76 mm rope samples in which the resin termination did not fail.Although the upper limit of the test machine, 4000 kN, was below the minimum breaking load for therope 4120 kN, the rope failed in 5 of the tests during the period when the rope was held at 4000 kN.The sequence was as follows:


15

sample survived21-01-2000



rope broke (1 min 45 sec)15-01-99

rope broke (1 min)13-01-99


rope broke on reaching maximum load04-01-99

rope broke (1 min)27-11-98

5 tests, samples survived27-11-98to18-09-98

rope broke (after 3 mins 20 secs at 4000 kN)14-09-98

10 tests, samples survived 14-09-98to60-04-98

ResultTest Date

Although the tests were not equivalent to a normal destructive test to determine actual breaking load,the failures below minimum breaking load were unexpected. The sequence of rope failures alsosuggests that rope failures became more likely as time progressed. Only 1 failure was observed in 16tests during the first 14 months of the life of the rope, whereas 4(5) failures were observed in the testsafter that period. The final sample, tested 12 months after the previous test, did not fail, suggesting thatthe rope had not deteriorated since January 1999.

A further feature of the tests with the 76 mm wire rope was that wires could be heard to break as therope sample neared the maximum load. These wire breaks occurred in all the tests where the ropetermination survived. On rope samples which survived the 4000 kN test load for 10 minutes there werebetween 2 and 8 distinct wire rope breaks with a mean of 5 for 17 tests. Of the ropes which broke,there were between 2 and 10 distinct breaks with a mean of 6. Wire breaks occurred at loads as low as3100 kN, although the vast majority were above 3700 kN.

A comparison with the other sizes of rope showed 2 wire breaks below MBL in two tests with 52 mmwire rope and 2 wire breaks below MBL in 5 tests with 32 mm wire rope. The main difference in therope samples are that the sample length to diameter ratio is smaller for the larger ropes:

80 for the 32 mm rope;40 for the 52 mm rope; and33 for the 76 mm rope;

and that the MBL for the 76 mm rope was closer to the breaking load:

97% for the 32 mm rope as stated by Bridon but near to 92% according to the testsreported here.

88% for the 52 mm rope; and98% for the 76 mm rope;


16

As a result, it is considered that the risk of wire breaks below the MBL was considerably higher for the76 mm rope samples than for the smaller samples and that this may have influenced the risk of the ropesamples failing below the minimum breaking load for the rope. Had the minimum breaking load for the76 mm rope been lower, say 4000 kN and therefore 95% of the actual breaking load of 4120 kN thennone of the samples would have broken below 4000 kN and the number of wire breaks would have beensignificantly lower. It is also possible that higher breaking loads would have been recorded if the loadhad continued to rise above 4000 kN rather than being held for a period at that level.

We therefore conclude that the 76 mm rope failures may have been influenced by either the lowerlength to diameter ratio of these samples or by the apparent lower margin between the MBL and theactual breaking load of this rope compared to the other rope sizes we tested.

Although there is evidence that the rope had lost strength over time these other factors make such aconclusion less clear cut than it otherwise might be.

7. DISCUSSION

In considering the conclusions to be drawn from the tests carried out, it is necessary to remember thatthe strength of a well made termination significantly exceeds that of the rope itself. The “faults” beingtested may, therefore, reduce the strength of the termination but not enough to reduce its strength belowthat of the rope. Nevertheless, the faults put into the termination by HSL are considered to be worstcase and, therefore, unlikely to be repeated by operators trained to follow the correct procedures.Several of the faults tested in the procedure did not reduce the strength of the terminations below that ofthe rope. We have considered carefully whether these steps are necessary and these considerations areset out below.

Cleaning of the rope is clearly the most important step in the procedure and poor cleaning consistentlyproduced termination failures below the minimum breaking load of the rope. We also believe that poorbrush configuration may contribute to poor cleaning. In particular, failure to adequately open out thewires in the bottom third of the brush will make it difficult for the resin to penetrate the space betweenthe wires. It is also possible that the presence of rope dressing may adulterate the resin mixture,resulting in set resin with a lower compressive strength. In the bottom third of the cone, there is a highvolume of wire to resin and the resin is easier to break down because of this. Although poor brushconfiguration alone did not cause termination failures, a poor brush will make it more difficult to cleanthe brush, particularly close to the root of the brush. We therefore consider that a satisfactory brush isimportant to ensuring a good termination.

Use of release agent on the inner surface of cast sockets did not appear to affect the strength of thetermination. Measurements of socket draw (movement of the resin capping within the socket) showedno difference in tests with and without release agent and lack of release agent appeared to have noeffect on the ability of the capping to pull into the socket under load. HSL believe that the resin conedoes not bond to the inside surface of cast sockets as it does to the machined and clean inner surface ofsockets used in the mining industry. If the offshore industry wishes to discontinue any use of releaseagent in cast sockets, HSL would have no technical reason to oppose this on the basis of these tests.

At room temperatures, it is clear that the thin, watery resin mix can penetrate easily into the brush andwe believe that there is also some self-mixing as the resin mixture passes through the wires of thebrush. Poor mixing and pouring techniques can therefore be tolerated at room temperatures but it isinevitable that there is some weakening of the terminations. At lower temperatures, where the additionof accelerator packs is necessary, the resin mix is much thicker and, although the HSL work did notfully investigate low temperature cases, it is believed that poor pouring and mixing techniques wouldhave a more significant effect at low temperatures. There is some evidence that low temperature curing


17

decreases the strength of terminations where the brush has not been satisfactorily cleaned. HSL believethis is associated with the thicker resin mix and the difficulty in ensuring that it penetrates the smallerspaces between wires in the bottom third of the brush. It is considered, therefore, that satisfactorymixing and pouring techniques, including removal of air spaces, are essential steps in the production ofgood terminations.

HSL found that smaller diameter terminations were less likely to fail when the rope brush was notadequately cleaned. It is considered, however, that is more likely to be a result of the thicker, heavierrope dressing used on the thicker ropes than a genuine size effect.

Although this work was not intended to address the fatigue life of resin-socketed terminations, it isrecognised that some of the faults introduced into resin capping could have an effect on fatigue life.Terminations made to the procedure set out in Annex 1 should avoid problems which are known toreduce fatigue life.

8. CONCLUSIONS

1 HSL has had no difficulty in producing good wire rope terminations on 76 mm galvanisedstranded wire rope provided the long established procedure for doing so were followed. Theprocedure used by HSL has been set out and illustrated in this report and a general procedure,highlighting good and poor practice, is included as an Annex.

2 The most important factor in ensuring a satisfactory wire rope termination was found to be thecleaning of the wire rope brush. The rope dressing must be fully removed, particularly close tothe root of the brush at its narrow end. The use of steam cleaning is recommended as a finalstage in the cleaning process to remove any residual solvent or cleaning agent.

3 Adherence to the procedure is particularly important at low temperatures (below 10OC) andwhen accelerators are added to reduce curing times for the resin. The resin mix under theseconditions becomes thicker at low temperatures and it becomes more difficult to ensure that asatisfactory resin mix reaches into small spaces at the root of the brush. The making of wirerope terminations in low temperature conditions should be avoided if possible.

4 Unsatisfactory cleaning of the brushed wires consistently caused termination failures at loadsbelow the minimum breaking load for the 76 mm diameter rope.At 52 mm and 32 mm rope diameters failures still occurred but the risk of the terminationfailing before the rope itself was lower. It is considered that the most likely cause of thisdifference was the thicker rope dressing used on the larger diameter ropes although size effectscannot be ruled out. At the smaller rope sizes, low temperatures increased the likelihood oftermination failure.

5 Poor brush, lack of release agent, poor resin mixing and poor pouring techniques did notproduce termination failures when introduced as single faults or in combination at roomtemperatures. A poor brush can, however, make cleaning of the brush more difficult and,because of this, we consider it an important step in the procedure. It is also important to followthe procedure for mixing and pouring the resin, particularly at low temperatures when the resinbecomes thicker, making penetration to the root of the brush more difficult. No evidence wasfound to substantiate the theory that the use of release agent affected the ability of the resincone to bed into the cast sockets and it is concluded that this step could be safely omitted fromthe procedure for terminating wire ropes with cast sockets.


18

6 In 5 cases from a total of 23 tests, the 76 mm diameter rope broke at a load below themanufacturer’s minimum breaking load (MBL). The applied load was in excess of 97% of theminimum breaking load and was held for up to 3 minutes 20 seconds before the rope broke.Tests on the 76 mm were also characterised by loud cracks during the loading of the rope atloads below the MBL. These were individual wire breaks, which did not occur with the samefrequency in tests with the lower diameter ropes. The pattern of failure initially appeared toindicate that the 1770 grade rope was losing strength with time but it was also considered thatthe ratio of sample length to diameter was low (33 although greater than 30, the minimumvalue specified in BS 301: Part 1: 1987) and that the MBL was 98% of the actual breakingload, giving a relatively low margin. It is therefore possible that the MBL for this rope hadbeen set at a level which is very close to the actual breaking load and that the MBL may fallwithin the range of actual breaking loads from a series of breaking load tests.

REFERENCES

BS 302: Part 1: 1987, Stranded wire ropes: Specification for general requirements.

Brandon J E and Chaplin C R (to be published), Analysis of a resin socket termination for a wire rope

Cordon C H H, 1995, The development of resin cappings for wire ropes in mines, part 1: the history ofthe development of resin cappings in the UK, Mining Technology, 77, no.883, 1995, pp 90-96.

Cordon C H H, 1999, the development of resin cappings for wire ropes in mines, part 2: service trialson friction-winder ropes, Transactions of the Institution of Mining and Metallurgy, Section A, MiningIndustry, 108, January-April 1999, pp A37-A51.

Wirelock Technical Data Manual, 1996, The Crosby Group Inc and Millfield Enterprises(Manufacturing) Ltd.


19

List of Figures

27BR0001.TIFSandy brown if resin sets at room temperaturesFigure 24

26BR0001.TIFBlue green if resin sets at low temperaturesFigure 23

28BR0003.TIFThe scratch testFigure 22

24BR0003.TIFBroddlingFigure 21

23BR0001.TIFPouring the resinFigure 20

The resin kitFigure 19

Rope rig vertical, ready for pouring the resinFigure 18

18BR0039.TIFSealing with plasticineFigure 17

17BR0011.TIFPositioning the ‘O’ ringFigure 16

16BR0015.TIFUse of split sleeve to centralise socketFigure 15

15BR0002.TIFWires should protrude 3 mm from socketFigure 14

1BRA0001.TIFPosition of serving within the socketFigure 13

Checking for rope dressingFigure 12

14BR0005.TIFDrip drying the brushFigure 11

13BR0008.TIFCleaning the brushFigure 10

9805-048/4The uncleaned, finished brushFigure 9

Brushing with paraffin to loosen rope dressingFigure 8

7BR10017.TIFa) Strands being opened outb) Strands opened out

Figure 7

Rope with end clamp fixed in placeFigure 6

Rope covered in plastic sheetFigure 5

Socket secured to rope rigFigure 4

4BR0005.TIFRope being cutFigure 3

3BR10026.TIFRope being servedFigure 2

2BR1002.TIFDiagram showing arrangement of servings priorto cutting

Figure 1


20

Incident cappingFigure 33

Incident cappingFigure 32

98 07-150/1Good capping after 4000 kN load test and afterremoval from socket

Figure 31

98 07-150/11Wires pulled out of wide end of cappingFigure 30

98 06-081/31Debris from a pulled out cappingFigure 29

98 06-056/7A pulled out cappingFigure 28

980 7-100/13Narrow end of a failed cappingFigure 27

9BR10005.TIFA poor brushFigure 26

29BR0004.TIFCut off the serving wireFigure 25


21

2BR1002.tifFigure 1 - Diagram showing arrangement of

servings prior to cutting

3BR10026.tif

Figure 2 - Rope being served.

CROWN COPYRIGHT HEALTH AND SAFETY LABORATORY An agency of the Health and Safety Executive

4BR10005.tif

Figure 3 - Rope being cut.

Figure 4 - Socket secured on rope rig.


Figure 5 - Rope covered in plastic sheet.

Figure 6 - Rope with end clamp fixed in place.


7BR10001.tifFigure 7 - Strands being opened out.

Figure 8 - Brushing with paraffin to loosen rope dressing.


9805-048/4

Figure 9 - The uncleaned, finished brush.

13BR0008.tif

Figure 10 - Cleaning the brush.


14BR0005.tif

Figure 11 - Drip drying the brush.

9805-048/7

Figure 12 - Checking for rope dressing.


1BRA0001.tif

Figure 13 - Position of serving within the socket.

15BR0002.tif

Figure 14 - Wires should protrude 3mm from socket.


16BR0015.tif

Figure 15 - Use of split sleeve to centralise socket.

17BR0011.tif

Figure 16 - Positioning the ‘O’ ring


18BR0039.tif

Figure 17 - Sealing with plasticine

Figure 18 - Rope rig vertical, ready for pouring the resin.


0002-079/9

Figure 19 - The resin kit.

23BR0001.tif

Figure 20 - Pouring the resin.


24BR0003.tif

Figure 21 - Broddling.

28BR0003.tif

Figure 22 - The scratch test.


26BR0001.tif

Figure 23 - Blue green if resin sets at low temperatures.

27BR0001.tif

Figure 24 - Sandy brown if resin sets at room temperature.


29BR0004.tif

Figure 25 - Cut off the serving wire.

9BR10005.tif

Figure 26 - A poor bush.


9807-150/13

Figure 27 - Narrow end of failed capping.

9806-056/7

Figure 28 - A pulled out capping.


9806-081/31

Figure 29 - Debris from a pulled out capping.

9807-150/11

Figure 30 - Wires pulled out of wide end of capping.


9807-150/1

Figure 31 - Good capping after 4000 kN load testand after removal from socket.

0001-074/1 0001-074/4

Figure 32 - Incident capping. Figure 33 - Incident capping


ANNEX 1

GENERAL PROCEDURE FOR MAKING GOOD RESIN-SOCKETED ROPETERMINATIONS ON STRANDED ROPE

This procedure should be able to be followed by a semi-skilled operator given suitable training and whohas demonstrated competence in this area.

1 Equipment list

The following is a list of equipment and materials needed in order produce a resin-socketed terminationof a wire rope:

Wire ropeWire rope socketRope socket rig and fittingsRope cutter/slitting discSteel tube for rope strandsSteel tube for rope wiresSplit sleeve for centralising rope in socketTirfor/winch (for big ropes only)Serving mallet/machineReel of soft iron serving wire (diameter of wire to match rope size)Socket alignment toolPlastic sheetRubber “O” ringHigh pressure steam cleaner with water soluble detergentWirelock resin kit/s - volume to match conical bore of rope socket, including silicone grease, stirrer andplasticineWorkshop hand tools including prybars, and tubes to fit strands and wiresStandard workshop protective clothing

2 Preparing the rope and socket

Uncoil new rope from drum.

Identify and mark the cutting point.

Support the rope horizontally between two rope clamps or similar so that the cutting point is midwaybetween the vices and the rope does not sag. Remove any excess rope dressing from the part of therope to be served.

Using the serving mallet, apply two soft iron servings, one at each side of the cutting point, as shown inFigure 1. The length of these two servings must be at least equal to the rope diameter. The gapbetween the two servings must be just wide enough to allow the rope to be cut without disturbing thetwo servings.

Apply one long serving at the side of the rope to be brushed. The length of this serving must be at least3 times the rope diameter and must be applied at a distance equal to the length of the rope socketbasket, minus, half the rope diameter, measured from the cutting point. Prior to this serving, shortlengths of plasticine must be applied in the valleys between the strands, Figure 2, over a distance ofapproximately the rope diameter and half the diameter from the end of this serving nearest to the cutting


point. This will seal the spaces/cavities between the strands underneath the serving which will help toeliminate possible resin leakage during the pouring process.

Temporary rope clamps can be fitted at each side of the cutting point prior to cutting. These arenormally used if single stranded serving wire is used.

Place the rope on the ground on “vee” block supports at each side of the cutting point. Cut the ropesquarely using a slitting disc or similar equipment, as shown in Figure 3. Flame curring must not beused as this is likely to affect the mechanical properties of the steel wires.

Remove rope clamps

Examine the rope socket to ensure the interior of the socket is clean and free of dirt etc. Roughness ofthe inside surface is not important provided that there are no obstructions to prevent the resin cone frombedding into the socket when a load is applied to the termination. If the socket has been usedpreviously then any resin adhering to the socket wall should be removed. The taper bore of the socketmust be concentric within the socket and, in particular, the wall thickness should be the same all aroundthe socket periphery. Physical damage or non-concentricity of the socket can lead to failure of thetermination under load. Such sockets must never be used.

Secure the socket in position on the rope rig, Figure 4. The rope rig serves as a secure brushing benchand helps to eliminate the manual handling of heavy rope sockets. It also provides accurate axiaalignment between rope and socket and it can be elevated and locked vertically to enable the casting tobe carried out correctly. If a purpose made rope rig is not available, a reliable method of accuratelyaligning the rope with the socket must be developed and used. This alignment must be maintainedduring the casting process. If this is not done, the load in the rope and in the socket will not be axial,the wires will be unevenly loaded and failure of the termination may result.

Apply a light smearing of silicon compound, supplied with the resin kit, to the inside of the rope socketbore. This will help the resin cone to bed into the socket when a load is applied, a process which isessential for the termination to develop its full strength, and will also help the removal of the resin coneif the socket is to be reused.

Apply plastic covering over the portion of rope to be threaded through socket. Secure it with maskingtape, Figure 5. This will prevent contamination of the socket bore when the rope is threaded throughthe socket.

Push the “O” ring onto rope over plastic covering and slide it on the rope so that it will be clear of thebrushing. This “O” ring will later be used as a seal at the socket neck.

Thread the served end of the rope through the socket so that the end to be brushed is clear of the socket.Fasten the rope to the rope rig using the clamps provided, Figure 6. Ensure that the end clamp ispositioned exactly at the point on the rope to which the wires will be unlayed.

3 Preparing and cleaning the brush

Adjust the rig to the desired position for brushing. Brushing is best carried out with the rig set at anangle most convenient to the ropeman.

Remove and discard the short serving on the end of the rope.


Using the large steel tube, unwind and open out each rope strand, in turn, to form a basic brush as inFigure 7. A flat blade is used to prise out each strand from the cluster before the tube is pushed onover the strand. Great care must be taken when carrying out this operation as the strands are springywhen they are bent back and any slippage or accidental release of tube is a potential hazard to personsstanding nearby.

Starting with the inner wire rope core, and using the small steel tube, gently ease out of lay and unwindeach individual wire, in turn, to form a complete brush. As the wires are opened out they should bebrushed with paraffin to remove and/or loosen the rope dressing, Figure 8. Each wire must beunwound down to the serving whilst still retaining its helical shape. Do not attempt to straighten thewires. Do not repeatedly bend wires to achieve correct position as this can seriously weaken them.Over bending, nicking, and twisting of the wires must be avoided as this could later cause fatiguefailure of the wires during service. The finished brush, Figure 9, must be as concentric as possible andthe wires must be as evenly distributed as possible.

Adjust the rope rig so that the brush is pointing downwards to allow the cleaning fluids to drain away.Cleaning fluid must not be allowed to penetrate down into the rope underneath the long serving.

Using the high pressure steam cleaner, Figure 10, thoroughly clean the brush using the detergent spray.Finally clean the brush with pure water to rinse off the degreasing agent or detergent. Allow the cleanbrush to drip dry whilst it is still pointing downwards, Figure 11.

Carry out a visual check of the brush to ensure that the wires are clean and that no lubricant or dressingis present on the brushed wires. Check that the rope dressing is visible under the serving, Figure 12.

4 Positioning and aligning the brush and socket

Measure and mark on the serving a distance of half the rope diameter measured from the inner end ofthe long serving, Figure 13. Discard the plastic covering which was previously placed over rope.

Position the socket in the rope rig, using socket spacers if needed, to align the socket with the ropeclamps.

Undo the clamps on the rope rig and pull the brush into the socket so that the small end of the socket isin line with the marking on the serving. Ensure that the ends of the brushed wires protrudeapproximately 3 mm above the end of the big end of the socket. If all three servings have beenpositioned accurately, everything should fit correctly, Figure 14. The objective is to achieve a length ofhalf the rope diameter inside the socket neck. This will ensure proper support of the wires at the root ofthe brush and help to protect them for fatigue damage. It is important to minimise the rotation of thesocket to prevent the silicon from inside the socket being scraped off onto the freshly cleaned wires.

Using the split sleeve, Figure 15, align the rope so that it is concentric inside the socket neck. Furtheraxial alignment of the rope will be given by the seating clamp positions on the rope rig when the rope isreclamped.

Reclamp the rope on the rig ensuring all the clamps are tight. Remove the socket alignment tool.

Slide the “O” ring into position so that it fills the annular gap between the rope and the socket neck,Figure 16.

Seal the neck of the socket by applying plasticine over the top of the “O” ring, Figure 17.


Adjust the rope rig so that the rope socket is vertical, Figure 18.

5 Mixing and pouring the resin

Detailed information on the use of the resin kits can be found in the Wirelock Technical Data Manualand in the information leaflet which accompanies each kit.

Consider the temperatures of the rope, socket and resin kit. Are they the same or is any of these likelyto be at a temperature below 10OC. Ideally, all components should be above this temperature, if notthen the use of accelerator packs may need to be considered. The easiest way to use these is to ensurethat all components are at the same temperature and to follow the resin kit suppliers instructions. Ifthere is any doubt as to the component temperatures, then they should be measured. If low temperaturecasting of the resin is unavoidable, it is particularly important that the root of the brush has beenproperly cleaned and that the procedures for mixing, stirring and pouring the resin are closely followed.It may be possible to use a warmed socket on a cold rope and some users have produced successfulcappings using this technique. In this case it is important to warm the socket only to room temperatureand not beyond. Storing the socket for a period in a warm area is better than heating it artificially. Useof a warmed socket reduces the need for accelerator (booster) packs.

Examine the resin kit to be used, Figure 19. Each kit consists of two containers one with liquid resinand one with powder together with a stirrer, silicon grease release agent and plasticine. These aresupplied in an outer container which is used for mixing. Booster packs are available separately and aresized to match to the volume of the resin kits. Check that the resin kit is not out of date. Out of datekits must be discarded. Check that the colour of the powder is off-white and the resin is free flowing.Kits can be added together to give the required volume. Always use the full container contents, neveruse part container contents.

Wear eye protection and a dust mask for mixing the resin. Mix the liquid resin and powder in thecontainer supplied with the resin kit. Stir for approximately 2 minutes whilst checking the viscosityand colour of the mixture. For temperatures between 2OC and 8OC one booster pack must be added andbetween 2OC and - 3OC two booster packs must be added.

Pour the mixture into the socket immediately, ensuring that the mixture is poured at one position only,as in Figure 20. Any movement is likely to introduce unwanted air into the mixture inside the socket.Fill the socket up until the level of the fluid is flush with the end of the socket. Finally, using a straightpiece of wire of similar tool, broddle the mixture inside the socket basket to remove any trapped air,Figure 21. The socket may be topped up as necessary as the resin settles. Any leakages must bestopped immediately by simply applying further plasticine around the socket neck as necessary. Atroom temperature, gelling will normally take place in approximately 15 to 20 minutes. The mixturewill be fully set after approximately 1 hour. At low temperatures the gelling and setting may take muchlonger and full setting can take as long as 2 hours even when booster kits are used.

When the resin has hardened, using a sharp instrument, carry out a scratch test by scoring the set resinin the end of the socket, Figure 22. This should leave a shallow scratch mark indicating the resin isfully set. The final colour of the resin is likely to be either bluish green, Figure 23, or sandy brown,Figure 24, depending on the temperatures reached during curing. A sandy colour indicates a hottercure than the bluish green colour.


6.1 Dismantling the clamps and servings

Remove the plasticine and “O” ring from the socket neck. Examine the completed socket terminationfor any defects.

Unwind the long serving wire and cut it off as close as possible to the end of the socket neck, Figure 25.

Remove the plasticine from between the rope strands and scrape off any leaked resin compound.

Finally relubricate the rope with rope dressing taking care to seal the neck of the socket.

Remove the complete socket termination from the rope rig.

When the rope is put into use, it is advisable to ensure that the resin cone has bedded into the socket.Unless the cone pulls into the socket by a few millimetres, the resin cone may not be subjected to thecompressive forces which give the termination its strength. The use of release agent will help the coneto bed into the socket.


ANNEX 2

PROJECT R31068, RESIN-SOCKETED TERMINATION OF OFF-SHORE WIRE

ROPES: SUMMARY OF TEST RESULTS

1,380Brush not cleaned17 May 199952-331,917(rope broke)Brush not cleaned14 May 199952-32

4,000Bad mix, bad pour &no release agent

26 Jan 199976-31

4,000Bad mix, bad pour &no release agent

21 Jan 199976-304,000(rope broke)Poor temperature15 Jan 199976-294,000(rope broke)Poor temperature13 Jan 199976-28

4,000Poor temperature12 Jan 199976-27

4,000(rope broke)Bad mix, bad pour &no release agent

04-01-9976-264,000(rope broke)No release agent27-11-9876-25

4,000Good, instrumented27-11-9876-24

3,651 (failed)Brush not cleaned norelease agent

06-11-9876-23


22-10-9876-22


22-10-9876-214,000Good28-09-9876-204,000Bad pouring23-09-9876-194,000Bad pouring18-09-9876-184,000No release agent18-09-9876-17

4,000 (rope broke)Bad pouring14-09-9876-164,000No release agent14-09-9876-154,000No release agent13-08-9876-144,000Poor resin mix21-07-9876-134,000Poor resin mix21-07-9876-12

3,083 (failed)Brush not cleaned15-07-9876-114,000Poor resin mix09-07-9876-10

2,162 (failed)Brush not cleaned23-06-9876-093,513 (failed)Brush not cleaned22-06-9876-082,691 (failed)Brush not cleaned08-06-9876-071,543 (failed)Brush not cleaned05-06-9876-06

4,000Bad brush13-05-9876-054,000Bad brush12-05-9876-044,000Bad brush11-05-9876-034,000Good17-04-9876-024,000Good06-04-9876-01

Test load (kN)*Socket conditionDateTest No


GoodJan 200076-49

485(failed)Brush cleaned Lowtemperature 8OC

Dec 199932-48

715(failed)Brush not cleaned Lowtemperature 8OC

Dec 199932-47

775(rope broke)Brush not cleaned Lowtemperature 3OC

Dec 199932-46


Dec 199932-45


Dec 199932-44755(rope broke)Brush not cleaned12 Nov 199932-43775(rope broke)Brush not cleaned19 Oct 199932-42

989Brush not cleaned18 Oct 199952-411,027Brush not cleaned18 Oct 199952-40

794(rope broke)Brush not cleaned19 July 199932-39661Brush not cleaned14 July 199932-38

788(rope broke)Bad mix, bad pour &no release agent

2 July 199932-37

787(rope broke)Bad mix, bad pour &no release agent

1 July 199932-36


9 June 199952-35


18 May 199952-34

*4000 kN = 408 tons


ANNEX 3

SPECIFICATIONS FOR MATERIALS AND EQUIPMENT USED

1 Wire Ropes

The wire ropes conformed to the following specifications:

� 76 mm 6 x 36 IWRC 1770 GAL RHO ZL200006 MBL 420.0tDate of manufacture: 12/07/97 Actual breaking load: 429.0tActual diameter: 76.78 mm



Breaking load tests were carried out on the date of manufacture in all cases. Tests were to ISO3108 using a testing machine calibrated to BS EN 100002-2.

2 Sockets

The sockets used in the tests were groved open spelter sockets with the followingspecifications:

� for use with 76 mm rope, 3 - 3.1/8 inch rope diameter sockets made from cast alloysteel;

� for use with 52 mm rope, 2 - 2.1/8 inch rope diameter sockets made from cast alloysteel;

� for use with 32 mm rope, 1.1/4 - 1.3/8 inch rope diameter sockets made from forgedsteel.

Sockets were reused as necessary for the tests. Resin cappings were removed by heating thesocket then pressing out the capping using a compressive test machine. The inner surface ofthe used sockets was then cleaned using a wire brush.


3 Sample Lengths

Sample lengths were as follows

� 76 mm samples - rope length between resin cappings was 2560 mm, actual ropediameter was 76.78 mm giving a length to diameter ratio of 33.3;

� 52 mm samples - rope length between resin cappings was 2135 mm and measureddiameter was 52.78 mm giving a length to diameter ratio of 40.5;

� 32 mm samples - rope length between resin cappings was 2620 mm and measureddiameter was 32.82 mm giving a length to diameter ratio of 80.

All the samples therefore complied with the minimum length criterion of 30 x diameterspecified in BS 301: Part 1: 1987.

4 Resin

Resin packs were Wirelock Rope Capping Kits. This was unsaturated polyester resin,dissolved in styrene and containing low levels of inhibitors to prevent prematurepolymerisation. Various sizes of the kits were purchased to suit the volume of resin cappingsbeing produced. Whole kits were always used. Low temperature accelerator (booster) packswere also supplied.

5 Test Machine

The tensile test machine was an Avery 4000 kN 74N8 rope test machine serial number E55372with RDP servo control. The machine is calibrated to BSEN100002-2: 1992. The machine iscalibrated to class 1, i.e. Accuracy is ± 1% of indicated value. The 76 mm rope samples wereloaded linearly at a rate of 800 kN/minute over a period of 5 minutes and then held at the peakload for a period of 10 minutes. Smaller diameter ropes were loaded linearly at a rateconsistent with reaching the MBL after a period of 5 minutes.

6 Rope Cleaning Agents

Ropes were cleaned using cold paraffin and a brush followed by use of a Karcher steamcleaner with Karcher RM87 detergent suitable for intensive cleaning applications and suitablefor removing oil and grease. Any residue was removed using clean steam.


Resin-Socketed Termination of Offshore Wire Ropes · Resin-Socketed Termination of Offshore Wire...

Documents

Transcript of Resin-Socketed Termination of Offshore Wire Ropes · Resin-Socketed Termination of Offshore Wire...