LUBRICATION TURBINE

7/28/2019 LUBRICATION TURBINE

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INDUSTRY DEFINED PROBLEM/PROJECT (IDP)STATEMENT FORM

STUDENT PARTICULARS

FIRSTNAME 1.GOHEL PRAJAPATI

LAST NAME SANJAY C. DHAVAL B.MOBILENO.

1. 9687150092

2. 9033224970

EMAIL [email protected]

COLLEGENAME GOVERNMENT ENGINEERING COLLEGE,BHAVNAGAR

ADDRESS

VIDHYANAGAR,BHAVNAGAR-364002.

BRANCH MECHANICAL ENGINEERING

SEMESTER 7 TH YEAR 2011

TEAMNAME SANJAY,DHAVAL

SIGNATUREOFSTUDENT

INDUSTRY PARTICULARS

---------------INDUSTRY COORDINATOR---------------NAME MOHIT B. PATEL

CONTACTADDRESS

C-3464,PATEL PARK,OPP.AYODHYANAGARI,KALVIBID,BHAVNAGAR

MOBILE NO. 7567883107EMAIL [email protected]

---------------INDUSTRY---------------

2 nd Floor, ACPC Building, L. D. College of Engineering Campus, Navrangpura,

Ahmedabad,(Gujarat)India-380015.Phone:91-79-

26300699,Email:[email protected] M:9909959336
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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NAME EXCEL CROP CARE LTD

ADDRESS

6/2,RUVAPARI ROAD,BHAVNAGAR

CONTACT

NO.

OFFIC

E

MOBI

LE7567883107

NAME OF INDUSTRIALESTATE BHAVNAGAR

COMPANY LOGO

INDUSTRY DEFINED PROBLEM STATEMENT FORM

TITLE OF PROBLEM/PROJECT

Problem associate with effect of lubrication on the failure of bearing in turbine and blower.

DISCIPLINARY | INTER-DISCIPLINARY DISCIPLINE

INDUSTRIAL DEFINE PROBLEM (IDP)Title of problem:

Problem associate with effect of lubrication on the failure of bearing in turbine and blower.

Problem indentificatoin

In EXCEL CROP CARE LTD, there are three turbinesinstalled which are


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one of capacity of 17.35 mw/hr,

two of capacity of 16.45 mw/hr,

three of capacity of 5.40 mw/hr,

To generate the power of 58.00 mw/hr capacity.

The turbine is the set of a generator, a gear boxand a rotor.

A barring mechanism is provided between the gearbox and generator to rotate the shaft at the shutdown time.

Bearing description: Bearings are a importantcomponent in major industries. Bearing problems canresult in costly downtime, equipment damage andbreakdowns. In addition, large industrial bearingsrepresent a significant capital investment.

This is especially true in industrial applications,where operating conditions tend to be harsh, loads areheavy, and contamination from dirt and scale arecommon.


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Barring gear mechanism :

It is the mechanism provided to rotate the turbinegenerator shaft at a very low speed after unit stoppages.

Once the unit is "tripped" (i.e., the steam inlet valve isclosed), the turbine coasts down towards standstill. Whenit stops completely, there is a tendency for the turbineshaft to deflect or bend if allowed to remain in oneposition too long. This is because the heat inside theturbine casing tends to concentrate in the top half of thecasing, making the top half portion of the shaft hotterthan the bottom half.

The shaft therefore could wrap or bend by millionths of inches.

This small shaft deflection, only detectable by eccentricitymeters, would be enough to cause damaging vibrations tothe entire steam turbine generator unit when it is


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.

BLOWER:

In the blower ,which is run by the motor, is not working.Because the bearing which is mounted in the shaft, isdamaged. The bearing is almost cracked and the hot airis remain in the formulation plant, so it is harmful to theworkers which are worked in the plant.


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Blower description:

Blower having a impeller inside. outside it has a

casing to protect the entire mechanism.

The hot air is coming in the blower through the heavypipe which is at the mounted on top of the plant, theimpeller is forced this hot sir into the atmosphere. Theblower should be designed with high degree of reabilitywith minimum maintenance and constructed should be

suitable to resources of the employer.

Literature review


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filled). The main disadvantage of using grease is itslimited life.

Mechanical work on the grease deteriorates its structureand in cases of high temperature, oxidation takes place (T

> 120 C) (Ito, et al.'). Severe lubricant starvation occurs,causing bearing failures. This implies that the service lifeof the bearing may be determined by the life of thegrease. In that case the bearings may need to be re-lubricated occasionally; i.e., filled with fresh grease. Thebearing manufacturers have specified the re-lubricationintervals in their catalogues.

These re-lubrication intervals are calculated from the lifeof the grease. Unfortunately, there is no absolute valuefor this. Even if bearings are running under very well-controlled conditions, such as in a laboratory situation,there is the usual significant spread in life. The re-lubrication interval is defined as the LOl of grease life; i.e.,the time at which 1% of a population of bearings isexpected to have failed

The challenge in grease research is threefold primarily.The first challenge is to develop greases that will givelonger life and/or are able to operate under more severeconditions (extreme low and high temperature andspeed). The second challenge is the development of predictive tools, such as numerical models or expertsystems.

The third challenge is to design bearing systems thatwould increase grease life by, for example, optimizing thegrease flow. All these aspects require a fundamental

understanding of the lubrication mechanisms of lubricatinggreases.

The research efforts in grease lubrication have so far beenrelatively small. The global business for grease does notallow for large research programs. The bearing industryhas a particular interest in understanding greaselubrication, though. More than 90% of all rolling elementbearings are greased and sealed for life, effectively

making grease a bearing component similar to rollingelements and seals. In addition, the internal design of the


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(Forster, et al.8). The effectiveness of these forcesdepends on how these fibers contact each other.

The thickener fibers vary in length from about 1 to 100pm and have a length to diameter ratio of 10 to 100

where this ratio has been correlated with the consistencyof the grease for a given concentration of thickener(Scarlett11). It is not obvious how to visualize thestructure of grease. In general, wet samples cannot beused in a scanning electron microscope.the

Since grease contains 80-90% oil, one may argue thatthe thickener structure may collapse if the oil is washedout and that such a picture may be misleading. Othervisualization techniques have been used as well such as afreeze-fracture technique (Magnin and Piau11'; Shuff andClarke"), where a replica is made of a frozen greasesample, which can be observed in the SEM. Also, atomicforce microscopy (AFM) has been used (Hurley andCann12). Shin, et al.13 visualized the grease flow in ashear field with an optical microscope in phase contrastmode. They observed very long fibers ranging from 50 to100 ??, which are much longer than those observed with

the SEM.An environmental SEM may be used but the low contrastbetween soap and base oil makes visualization difficult.Salomonsson, et al.H have visualized the grease structureusing the cryo-TEM technique and visualized naphtheniclithium grease and paraffinic lithium grease by increasingthe contrast between soap and oil through, e.g., replacinglithium by lithium/cesium soap.

Additives

The role of additives in grease has not been exploredin much detail. At high temperatures, theantioxidant additives will have the greatest effect.These additives are continuously consumed duringbearing operation and, according to van denKommer15, totally consumed after 50% of greaselife. Extreme pressure/anti-wear (EP/AW) additives

are generally applied for low speed and/or high load.The effect on grease life that these additives have is


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not well understood. According to Gow16 some 90%of all lubricant additives destroy the thickenerstructure of grease since they are often basedon surface -active materials and this leads to what iscommonly called the mayonnaise effect (softeningand discoloring). He also mentions that of theremaining 10%, some 90% do not work. He ascribesthis to the fact that the thickener material is almostalways very polar (metallic soaps) and that the (alsopolar) EP additives will adhere to the soap structurerather than to the metal surface (Gow17). This is incontradiction to the results found by McClintock18who tested a number of greases on lubricant life andfound an increase in life. A very promisingdevelopment is the use of bismuth as an EP/AWadditive because it is nontoxic and shows verygoodperformance (Rohr1").Kaperick20 shows in an evaluation of the "TimkenOK Load Test," in which identical EP additives give adifferent response to EP action for differentformulated greases and ascribes this to a possibleimpact of mobility towards the surface through

chemical interactions or attractive forces. If Gow isright then it is likely that the impact of EP additiveson grease performance may be measurable throughthe mechanical and thermal aging of grease. Thisdirect impact may be primarily on consistency andbleeding rate.

Non-Newtonian Rheology

A lubricating oil shows non-Newtonian behavior at high shear

rates and pressure. Due to the thickener structure and itsinteraction with the base oil, grease shows this behavioralready at very low shear rates and ambient pressure.Measurements from low to high shear rates can be found inPavlov and Vinogradov21 .

The solid-like behavior, or resistance to flow (or leakage), istraditionally characterized through the consistency orpenetration, measured using a cone penetrometer (ISO 2137,

ASTM D217), which is translated into an NLGl consistencynumber. An alternative is to measure the yield strength on a
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rheometer, by means of the computerized evaluation of yieldvalue (CEY; Gow22) or through the "cross-over stress"(Couronn, et al.23; Couronn and Vergne24). A correlationbetween yield stress and penetration/consistency can be foundin Couronn et al.25. Generally, this is only determined atroom temperature.It is clear that the grease will be severely worked in thebearing. This applies to the grease that is being churnedbetween the rolling elements but also applies to the fractionthat passed the EHL contacts where shear rates are OQO6 S1).This causes a rapid change in rheological properties of thegrease during the initial phase of bearing operation. It istherefore relevant to measure the rheology after working the

grease. This can be done in a rheometer itself, in a greaseworker", or in a Shell roll tester27. The change in consistencyloss is quantified by measuring the mechanical stability of thegrease before and after working the grease.

The yield stress strongly depends on temperature.Measurements for different types of grease can be found inKaris, et al.28 or Czarny29. Karis shows that the yield strengthof a lithium grease may drop from 500 Pa at 20 C to 100 Pa at

60C.As shown by Forster and Kolfenbach30, greases showviscoelastic behavior. There are a number of models proposedfor low and high shear rates. The best known are the powerlaw, Rhee-Eyring, Bingham and Herschel-Bulkley models. Adefinition of these models can be found in Yousif31. Thesemodels assume solid or very high viscous behavior at low shearrates and viscous (with possible shear thinning) at higher shearrates. An example can be seen in Figure 2. In addition to thisnonlinear shear stress-shear rate behavior, grease isthixotropic, meaning that the measured stress also depends ontime. Paszkowski32 defined thixotropy as an isothermaldecrease in structural (apparent) viscosity during shearing (atboth constant and variable shear rates) followed by an increasein the viscosity and the re-solidification of the substance onceshearing ends. Pavlov and Vinogradov2' show creep-likebehavior at very low shear (1O0 s ,) until the yield strength

has been reached. As shown by Hurley and Cann33, greaserheology approaches that of the base oil at high shear rates.


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They also show that mechanical work changes the rheologicalbehavior significantly. The grease thickener structure is thuscontinuously degrading and is transformed irom a Binghamplastic or Herschel-Bulkely materia! towards a more viscousmaterial (Mrieux, et al.34).

LUBRICATION MECHANISMS:Lubricating ConditionsThere is noconsensus on the lubrication mechanisms in grease lubrication.There is an overall agreement though that grease-lubricatedbearings are generally running under starved lubricationconditions. This has been shown by Poon in 1972 on a discmachine (Poon35) and by Wilson in 19793" in full bearings.Wilson measured the film thickness in cylindrical andspherical roller bearings and showed that the lubricant film

initially exceeds the value in case of fully flooded oil lubricationby 20-25%. However, already after a few hours the filmthickness has decreased below this value. At this point thebearing runs under starved lubrication conditions.

Barz37 measured the film thickness in a cylindrical thrustbearing as a function of bearing speed. His measurementsshow that the film thickness is relatively large at low speed butdecreases with speed up to a speed where the film stays

constant. Wikstrm and Jacobson38 measured the electricalcapacity over the bearing contacts (using a method developedby Heemskerk, et al.w) in a grease lubricated spherical rollerbearing and showed that metal-to-nietal contact occurs veryregularly, meaning that the films are very thin, certainlysmaller than the values that could be expected assuming fullyflooded conditions.

As a rule of thumb approximately 30% of the free volume of the bearing should be initially filled with grease. It will be clearthat this is much more than required to provide the bearingwith a (fully flooded) lubricant film. In the beginning, excessivegrease churning, or grease flow, takes place, which isresponsible for the high temperature peak caused by thechurning component of the friction torque. The initially thicklubricant films in the beginning indicate that at least during thisinitial bearing operation thickener enters the contact.

Single contact measurements by Astrm, et. al.40, Williamson,et al.41, and Kaneta, et al.42* using a scoop to ensure fullyflooded conditions, have shown that the film thickness is
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indeed higher than the fully flooded oil film thickness. Theoptical setup also made it possible to show that greasethickener lumps were entering the contact. The literature doesnot reveal if Ulis is really restricted to the initial phase of bearing operation. It might be that this i

DISCUSSION AND CONCLUSION

The various hypotheses on the mechanisms of greaselubrication, all based on observations/measurements, indicatethat there may be no unique mechanism. As an example, atlow temperatures oxidation and evaporation will not give asignificant contribution to "grease aging." At high temperaturesoxidation will dominate. Some metals catalyze oxidation (brasscages!). This may be one explanation why there is noconsensus on the mechanism. It is certain that initial fillingplays a major role. Too much grease leads to excessivechurning, high temperatures, and severe grease degradation. If the bearing is properly filled, two phases can be distinguished;i.e., a churning phase where excessive grease will be pushed tothe shoulders of the bearing onto the seals/ covers. This

process is determined by the flow properties of the grease(rheology). Prediction of flow is very complex due to thenonlinear grease rheology and the two/three phases involved(thickener, oil, air).

The remaining grease inside the bearing will be overrolled,where the thickener structure will be broken down, releasingoil, and where the thickener material could form a thin layer(Cann and Spikes45; Cann, et al.46) or a high viscous layer(Scarlett9). After this phase the "bleeding" phase takes place.This phase is characterized by starvation. The lubricant filmthickness is initially larger than calculated using the base oilviscosity. Side flow reduces the film thickness. Electricalresistance measurements in full bearings confirm theoccurrence of starvation. The grease reservoir may be formedby grease under the cage (Scarlett9) and/or on the bearing

shoulders (Cann, et al.49). However, there are also hypothesesthat the bearing simply runs on the initial layer throughout its


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life-time and will not be replenished at all Scarlett9. Scarlett9states that the grease on the shoulders plays a major role inproviding a long grease life. He ascribes its role to provide anexcellent sealing. Such sealing may indeed prevent side flowand reduce starvation. This would also explain why Lansdownand Gupta12 found an increase in oil content of grease close tothe raceway. At least for line contact bearings it has beenclearly proven that grease located under the cage bars isbleeding oil (Mas and Magnin55). It is not clear, though, towhat extent this bleeding contributes really. The 100 h thatScarlett mentions is very short.

Prediction of film thickness in grease lubricated bearings is verycomplex. The film is a result of feed and loss mechanisms

where bleeding, or grease creep flow, is the feed mechanismand where side flow (starvation), oxidation, polymerization,and evaporation are the loss mechanisms (Figure 4, Wikstrmand Jacobson38). Side flow may be hindered by the excellentsealing from grease located on the shoulders of the bearing.For some bearing types an additional loss mechanism is formedby pumping, which takes place due to the tangentialcomponent of the centrifugal forces on roller and rings (vanZoelen, et al.65 ; van Zoelen, et al.69).

At low shear rates grease creeps, so it may be that grease veryslowly flows into the track.

An additional complexity is the dynamic behavior of greaselubrication. The grease lubricated bearing shows an inherent"self-healing" mechanism where replenishment may happen dueto film breakdown resulting in metal-tometal contact, local heatdevelopment, and release of grease into the raceways (Mas andMagnin55; Cann and Lubrecht73; Lugt, et al.74). This means thatthe life of the grease in bearings cannot easily be predicted basedon film thickness calculations only. Ultimately, knowledge onmulti-phase flow, nonlinear rheology, EHL theory, and chemistryneed to be combined to develop predictive models for greaselubrication in rolling bearings .

Objectives: A typical oil system consists of an oilreservoir, pump, piping and filter. A cooler may also be


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required. This system sensor an adequate supply of oilfor both cooling and lubrication.

Contaminants and moisture are removed from thebearing by the flushing action of the oil, and filters trap

contaminants.

It is relatively easy to direct lubricant tomultiple bearings in the deterioration.

increasing lubricant life and system efficiency. maintenance will be reduced.In large units, lube oil cools the bearing by carrying

off heat to the oil coolers. Lube oil in some turbines alsoacts as a hydraulic fluid to operate the governor speed-control system.

METHODOLOGY: there are mainly two type of lubricatoin oil pump system is required.

1. Main oil pump,

2. Auxiliary oil pump, Than iInn turbine due to the carelessness of the operators,failure of the lubrication system of that turbine occurs, sothe friction between the journals bearing and shaftoccures. Therefore the failure of jurnal bearing occurs.

Proper maintenance is must needed. Failure tofollow installation instructions and to maintain proper

lubrication can result in equipment failure. To investigate the problems, the engineer must have indepth knowledge about basic of lubrication systemsand design of bearing Your lubrication supplier and bearing supplier should have themost current data and be able torecommend the proper lubricant for the application. As inselecting the proper bearing for the application, the


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conditions to which the lubricant will be subjected must beconsidered. How grease waiting for future use is treated and stored will bea key factor in the life expectancy of

equipment. Lubricants should be stored in moisture- andtemperature-controlled environments, free of dustand chemical exposure. Contamination entering grease will likely happen duringtransfer from one point to another. Failure toexercise care in this process will nullify the attention givenpreviously. There are a number of ways toproperly refill grease guns. Using a scoop or paddle from a

container is the oldest technique. It involvesspooning grease from a storage container and tamping it intothe grease gun to remove air bubbles. Thismethod is most likely to introduce contaminants into the grease,especially when performed in the field. It isnot a recommended method except in the most dire of circumstances.Using tube refills is the most common method of refilling a

grease gun. It involves removing the empty tubeand installing a new, compatible tube of grease into the greasegun. Take care to clean dirt and old greasefrom the canister and handle assembly before installing aclean, new tube of grease. Perform this task in asclean and dry an environment as possible.When refilling from a storage container using mechanical or hydraulic pumps, grease is pumpedmechanically from the storage container directly into theportable grease gun. When care is taken to cleanoff the port on the grease gun and delivery hook up from thepump, this is the fastest and safest method of grease transfer. Assuring that the correct grease is introduced into bearingsmay involve coding systems. Labels, numbers,tags, or color-coding on bearing housings that indicate whattype of grease is being used can be very helpful


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REFERENCES:

The text book of Power plant engineering by arora-domkundwar. The text book of Fluid power engineering by R.K bansalwww.google.com

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