LIGHT AND MEDIUM MERCHANT MILL

LIGHT AND MEDIUM MERCHANT MILLDESCRIPTION :

The Light & Medium Merchant Mill of VSP has been envisaged to produce :

i) 710,000 Tons per year of Light & Medium Merchant Mill Products.

ii) 246,000 Tons per year of Billets for sale.

iii) 885,000 Tons per year of Billets for Wire Rod Mill.

At 3.0 MT stage.

Entire mill has been laid out at an elevation of +5 metre except the charging grids and its associated roller table which are located in the cross bays at + 0.00 level. The material is lifted up to the elevated floor on A-C & C-D bays have their discharge sides situated on C-D bay. The C-D bay i.e. the Mill bay. Which stretches about 960 metre long houses the combined Billet and Bar Mill with its inline roller hearth furnace, cooling beds, collecting beds and cold shears. The finishing facilities viz. bundling and piling installations are laid out across the cold shear delivery roller table and span both C-D & D-E bay.

Area-wise integrated operational description is given below:

Charging, Furnace & Discharging Areas:

The feed material for the mill is continuous cast blooms of 250mm*320mm size having a nominal bloom length of 6.3 metre. Cold blooms are charged on to the charging grid by magnet crane according to the rolling sequence list. This charging rhythm of blooms depends upon the contracted rolling modes. Each walking beam furnace has defined track numbers and charging or ;discharging of blooms from charging grids and furnaces respectively will be according to the rolling mode i.e. each bloom destined for its defined track number will be discharge from charging grid in the sequential order. Normally furnace.1 is intended to feed hot blooms for production of billets and depositing on to billet cooling bed while furnace.2 is intended to feed hot blooms for onward transmission to Bar Mill. This implies that the cold blooms are to be charged in charging grid in a definite pattern to suit the particular rolling mode adopted and particular grid can be operated for discharging of blooms on to roller table upon ON light flashing and the light will go OFF when preselected number of blooms have been discharged. In order to identify and check the correct charging pattern the first bloom of a changed heat number is given a colour marking.

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Rectangular blooms will be placed on the charging grids (3nos.) in flat position (dimension 320mm flat) by means of magnet crane. The cranes are capable of loading 3 blooms at a time and will form a gapless bloom groups of max. 6 blooms each. Each grid is capable of receiving maximum of 6 groups which are appropriately spaced apart for the folding dogs to restore the upright position and engage. Two bloom groups can be moved by the forward and rear dogs and blooms are discharged on to roller tables (Item 2) one by one in the sequential manner as mentioned earlier. The respective grid will go OFF when the preselected number of blooms have been discharged on to roller table. When the blooms have passed the roller table section in front of another grid, the light for that grid will be ON permitting that grid to discharge blooms. Blooms are discharged on roller table and conveyed to the elevator (Item 4). Defective blooms, if any, on its travel to the elevator will be detected manually by operator and positioned in front of defective bloom grids (Item 1a) and will be pushed out off the roller table. The roller table (Item 2) transports the blooms normally under sequence control to their respective destined elevators 1 or 2. The blooms are pushed off the roller table by lever type push off on to a ramp from where they are picked up by carrier links of elevators and pulled up. The carry off device downstream pick up the bloom and places it on furnace approach roller table (Item 5). The furnace approach roller table working on sequential control, positions the blooms while on motion on various sections of this roller table by means of light barrier. Since the walking beam system are to be uniformly loaded, different bloom lengths will be classified in two categories and positioned in front of furnaces automatically. The bloom on its passage is stopped and its actual weight is recorded. The material tracking computer system takes over the actual weight, checks with references weight and then sets the bloom free for further transport. Downstream, detection is made about upright or horizontal position of bloom and if it is found to be upright, the bloom is tilted, set into horizontal position and then released for transport to its destined furnace track depending upon the rolling mode adopted. As soon as the blooms are positioned correctly and the walking beam furnaces are ready to receive the blooms, the blooms are pushed inside the furnace by furnace pusher (Item 10). As mentioned earlier each furnace is loaded in two rows and each row is meant for its defined destination. (Two furnaces have four tracks and materials are discharged by discharging units (4 nos.) as per the discharging pattern envisaged for the particular rolling mode.) At the delivery side of the furnace, actual position of blooms arriving is detected by means of a sensor and its actual position is given out as a coded series of pulses referred to the theoretical position.

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When the furnace walking beam system has completed its horizontal movement, the sensor has given out the actual position of bloom. This information is utilized by the corresponding discharging machine (the mobile beam of the machine has already reached to the discharging line) to complete its remaining stroke and to lift the material off the furnace and place it on delivery roller table (Item 12) provided the respective roller table section is free. If it is already occupied, the discharging machine is held in waiting position and subsequently deposits the bloom as soon as the respective roller table sections are free. If the discharged hot blooms are found to be defective the blooms are conveyed along the roller table in the reversed direction and are pushed over defective bloom grid by bloom pusher. Reject blooms are picked up by crane in layers of three and deposited on to transfer car (Item 301). The transfer car transfers the reject blooms in the cross bay R-Q.

BREAKDOWN MILL AREA :

Hot bloom travels forward over the roller table under sequence control and is freed from scale on the move by the descaler unit and is finally positioned over the roller table section having tilter unit. The tilting (under manual control) is done to make the bloom upright. The upright bloom now enters the first stand of Billet Mill. As soon as the tail end of this bloom clears Stand No.1 (Photo cell disilluminated), the upstream tilter is again ready to receive the next bloom under sequence control.

There are seven stands (four horizontal and three vertical) in the breakdown mill. IN five box passes and one each of diamond and square passes the blooms are reduced to 125mm sware of 33m length (referred to nominal bloom length of 6.3m) with a finishing speed of 1.3 to 1.6 m/sec depending upon the bloom discharge temperature of 1100C-1200C. The draw-in speed of bloom varies from 0.256 m/sec to 0.315 m/sec depending up on the discharge bloom temperature. A four crank shear installed behind the mill stands is designed to crop both ends and to cut fixed billed length between 5.0 and 12.2 m or to perform optimum yield dividing. Billets meant for bar mill are only cropped at the front and back ends. When cutting fixed lengths, rest ends upto 1.5 m are guided into a scrap bucket (recoil roller table section open). Rest ends above 1.5 m are transported (recoil roller table section closed) to a location where they are diverted into a short length disposal cradle. Detection of a rest and below or above 1.5 m is automatically done before rest end cut is performed.

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Whenever a bloom meant for bar mill enters BDM, checks are made whether the pendulum shear at the entry of bar mill is in the process of performing an emergency out of the proceeding bloom in the very strand for which the new bloom is being rolled in BDM. It if is so, the new bloom being rolled at BDM must be out into pieces of 5 m lengthy by the 4-Crank shear. Those pieces are then deposited into the short length disposal cradle as described earlier.

If optimum yield cutting is performed, for example, for billets for Wire Rod Mill, the total finishing length will be detected by computed calculation and decision made as to which length is to be cut to get three equal pieces with one minimum crop cut at each end. Computer calculation of the first billet length is made on the basis of bloom weight, already stored in the first billet in conjunction with the reduction in the BDM stands, permits to assess the billet length with substantial accuracy. However, the exact billet length measured by the measuring roll on the four-crank shear is used to calculate the corrective factor. This factor is also a parameter to calculate the exact discharging cycle for the succeeding BM blooms.

BILLET MILL COOLING BED AREA :

Billets meant for Billet Mill cooling beds are stamped on the move on the head ends and are transferred to cooling beds on the move by means of discharge drums in the form of feeder screws which after one full revolution, push the billets running on cooling bed roller tables side-wise to a brake-plate, where at comes to rest after a short braking distance. There are disappearing/ end stops to limit the bracking distances. In order to ensure proper discharge of billets on the move, proper discharge of billets on the move, proper gap is created between billets by giving a lead of max 20% to the run out roller table to that of exist stand V7 of the break-down mill. The two cooling beds can be charged in one or two rows depending upon the cut lengths. Normally the cooling beds are fed in alternating order. Lengths cut from first billet are transferred to cooling bed-II and are alternately cross-transferred by the rear and forward drum (2-row charging condition). Cut lengths from next billet are diverted to cooling bed I and alternately across transferred by the rear and forward drum (2-row charging condition). However, in case of single row charging condition the two cross transfer drums of each cooling bed are jointly operated.

The cooling beds are designed as turnover type beds and consist of stationary and moving rakes with notches. In order to ensure that the billets remain straight during the cooling process, the moving rakes turn the billets twice through 90 about their longitudinal axis in each stroke, thus moving them to two stationary rake notch pitches.

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This movement will always ensure a vacant supporting notch between any two billets, thus ensuring proper cooling. Pawl type transfers disposing down stream the cooling beds take the cooled billets to form layers. When these layers arrive in the lending position, they are picked up by magnet cranes and stored in Billet storage yard for further processing them through billet inspection and condition line, if so required, for sale/ wire rod mill billets. Otherwise stored billets can be sent directly to wire rod mill bay through transfers.

ROLLER HEARTH FURNACE AREA :

Billets meant for Marchant Bar Mill are cropped at the front and rear end and generally have a length of approximately 31.6 m. These billets are transported with a speed of 2 m/sec to the inline two strand roller hearth furnace. Billets, arriving in succession, enter the reheating furnace, designed for two strand feeding via a switch arranged in front of furnace. Each of the strand has roller table lines which are divided into three groups. Each of these rollers are water cooled, overhung type and are separately driven. Billets arriving in succession are diverted to strand 1 and 2 in alternating order by the switch. Billets normally arrive at a surface temperature of 1100C at the furnace and are heated and sacked to a discharge temperature of 1150C /1130C depending upon double strand, single strand rolling respectively. The billets enter the first stand of the bar mill at the normal entry temperature of 1100C. To achieve the discharge temperature a device will calculate the residence time of the billets inside the furnace depending upon the inlet temperature of billets. The billet will oscilate inside the furnace to achieve this residence time.

All billets leaving the furnace are detected by photocells arranged at the furnace discharge and causes automatic speed reduction of the furnace roller table to suit the mill entry speed of about 0.1-0.5 m/sec plus a lead as pre-selected. As soon as the tail end of the billet running on strand-1 or strand-2 of mill clears the furnace roller table groups (3 groups as previously described). They are successively made speed synchronized again with furnace approach roller table to receive the next billet.

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BAR MILL AREA :

The billet head now approaches the 1st groove at a predetermined speed. If, however, entry does not take place (rulls are not gripping) the top roll of the pinch roll (Item-44) which is located between inline roller hearth furnished and first stand will be shifted over the billet and lowered down on to the billet and bottom pinch roll is made to rotate at about 0.6 m/sec. The entering process is assisted due to frictional engagement between pinch rolls and billet. After billet entry, the top pinch roll is again lifted and shifted to other stand to assist the next entering process, if called for. This lifting, shifting and lowering of top pinch roll is manually controlled from pulpit CP 5 for better adaptation. The pinch roll is also used in case of mill trouble. In case of mill trouble it feeds the remainder portion of billet to the pendulum shear for size reduction into scrap pieces or transports back to the furnace depending upon whether the residual billet is long or short. The billet, entering the Merchant Mill, normally needs no head and crop cut by pendulum shear because the four crank shear in Billet Mill has already performed this job. However, the decision is left to the operator in CP 5. The continuous multi-line mill comprises an eight-stand roughing train, two five-stand intermediate trains and two four-stand finishing trains. This mill arrangement permits to roll smaller size section in two-strands such as rebars, rounds, squares, flats and angles. In case of single-strand rolling it is also possible to prepare in parallel with the rolling process, the complete second intermediate and finishing mill for a new product size.

Two box passes followed by a diamond groove series are provided in general in the roughing train for double strand rolling to get the necessary high total reduction. In case of single-strand rolling the two box passes are followed by a uniform diamond square series because of the lower total reduction involved and because it is necessary specifically for section rolling to produce larger size starting squares for the larger finishing sizes. In both cases this series is followed by a diamond-square and/ or oval-square series which in the finishing trains changes over into an oval-round series for production of rounds. The finishing speed will be maximum 20 m/sec. Starting from stand V19 I/II of the two finishing mills, loopers are provided between the stands so that twist-free rolling not only will be possible due to the V-H stand arrangement but also rolling in the absence of tension to thereby obtain rolled products of good surface qualities and tolerance.

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Each of the stands is provided with separate drive. Regulating range from the main drives and gear ratios have been selected, so that the maximum rolling speed in each stand and upstream the intermediate mills and snap shears for emergency cuts only ahead of the finishing mills. Since this mill design provided for a maximum of nine passes only to be run after the last cropping out ahead of the respective intermediate mill, no further cropping has to be done on the upstream side of the finishing trains.

The function of the rotating shears beyond the last stands of the finishing mills is to crop head end of the material leaving at rolling speed as for as required, and/or to cut it into multiples of specified sales lengths. In addition, test pieces can be cut on these shears which will be directed to Express Laboratory via a conveyor. Space has been provided for defectoscope and section size measuring instrument (future) to be arranged between the last stand and the cooling stretch behind each finishing train. They permit to inspect and check plain rounds, squares and flats etc.

Roll changes in the roughing mill area will be affected by means of special change rigs installed near the operating side of mill. In the intermediate and finishing mill areas, complete stands will be changed by means of high speed change rigs and the roll changing operation will be done in separate stand preparation areas, one for horizontal stands and the other for vertical stands.

Cooling Stretch Area :

The finished bar row enters the cooling stretches. There are two cooling stretches each installed just downstream the last stand of the finishing mill. The purpose of the cooling stretches is to cool down the rebars to such an extent so as to produce desired mechanical properties. It also serves to control the scale formation.

The rear leaving the last stand of the finishing mill passes through a cooling stretch. The cooling efficiency of this installation is such that a surface layer of the bar is quenched treatment is stopped when a determined thickness of martensite has been formed under the skin. When the rebar leaves the cooling stretch, a temperature gradient is established in the cross-sections of the bar causing heat to flow from centre to the surface which results in self tempering of the martensite.

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Finally during slow cooling of the rebar on the cooling bed, the austentic core transforms into ferrite and pearliet or into bainite, firelight and pearlite the unequivocal relationship linking the mechanical properties to the tempering temperature is the key to the control of tempcore process. To achieve the required mechanical properties, it is sufficient to maintain the tempering temperature within a pre-determined range. The obvious control variable are the length of the quenching line and the cooling water flow rate at suitable number of cooling pipes whose diameters are chosen as a function of product diameter. A strippers fitted at the end of cooling pipes to make sure that the material leaves the stretch in dry condition. The cooling stretch is also used cool plain rounds to reduce secondary scaling. Section can also be cooled for better straightness effect on cooling bed. However, to do so the cooling stretch is converted by replacing cooling pipes by cooling troughs. Normally the cooling stretches are positioned with their centerline in alignment with passline. For those products which need not pass through cooling stretches, the cooling stretches, mounted on transfer car are shifted so that roller cable arranged paralled to each cooling stretch is positioned in the base line.

Disposed down stream are pinch roll units which guarantee the correct bar speed during the cooling process. These pinch rolls are speed synchronized with the exist stands of finishing mill I & II so that bar speed remains same when ;the bare tail has left exit stand of finishing mill. They also give to enter the material into the rotary shear.

The rotary shear serves to divided the roller stone and to cut one head and crop pieces/ test pieces. The shear is fitted with a scrap deflector which diverts the crop pieces. The shear is fitted with a scrap deflector which diverts the crop pieces/ test pieces into a scrap bucket/ conveyor via a crop chute and switch arrangement.

Depending upon the programme i.e. whether the shear is to perform front end cropping with succeeding dividing cut without front end cropping, the deflector unit will be accordingly connected or disconnected from the shear gear unit. The shear with speed dependent time relays. Cut lengths preset manually or by means of a computer controlled length preset arrangement for optimization. However the maximum possible cut length is governed by the length of cooling bed with appropriate safety distances.

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BAR MILL & COOLING BED AREA :

Disposed downstream of shear is pivotable approach roller table and swinging device respectively. These two operate in proper sequence and permit to feed both cooling bed simultaneously when rolling in two strands or two cooling beds in alternating order from either of the finishing train when rolling single strand. The bar now runs with its rolling speed over the run-in-trough mounted over the swinging device to its destined cooling bed. These run-in-troughs perform the function of separating the bar stop by stop, cross transferring the bars across the rolling line, breaking the bar either by single slide or dual slide and finally bringing them at rest with bar head on a flue line. They are then picked up by the moving rake system of cooling bed. Initiation of separating ledge, brake slide 1,2 are automatically controlled depending upon various parameter viz. speed, cross transfer time of bars from zone to zone etc. The choice of dual slide or single slide braking is dependent upon the rolling speed of bar. Generally dual slide braking is adopted where high rolling speed of 14 m/sec 20 m/sec are involved. The cooling beds can be double charged (double covering) or single charged (single covering). This means that under double covering materials will be loaded in both primary and secondary notches whereas under single covering the materials will be loaded in primary notches only. Double covering is practicable only for specific sections and upto the maximum load capacity of the rakes whereas in all other cases single covering will be adopted. However, under single covering, some sections whose width are wider than primary notch, will also cover partly or wholly the secondary notches.

The moving bar often having been brought to a stand still position over brake slide 2 as previously described is now lifted by the moving system of rake of the rake type cooling area. In case of double covering the brake slide 2 occupies alternately lift out position and eject position in sequential manner and the moving rake system always picks up the bar from lift out position of brake slide 2 and places them over the primary notch of fixed rake system. The alternate bars while on eject position of brake slide 2 will always slide down by itself and be deposited on the secondary notch of the fixed rake system. In this way both the primary and secondary notches will be covered and bars will advance towards the discharge side of cooling bed.

In case of single covering the bars are always brought to lift out position of brake slide 2 and lifted by moving rate and deposited on primary notches only.

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To obtain the minimum cooling bed discharge temperature of about 80C for sections to be straightened and of about 150C for sections which require no additional straightening, a cooling and width of about 11.1 m each has been provided between run-in discharge roller table centers.

The first part of the cooling bed area comprises a straightening plate grid which provides additional support to the hot material to produce more straightening effect by ensuring slow and uniform cooling. Disposed on the cold side of the rake type cooling area is an aligning device which consists of a continuously operating driven and idling rollers provided with rake notch profile (secondary and primary notches). These rollers are provided with brake shoes which move up under the action of pull rod system thereby lifting the bar up. There are proximity switches each for secondary and primary notches. This device permits to position the bar noses on a flush line. This is due to the inevitable positional differences between individual bars as they are braked down. The aligning of bar noses will keep the material losses to a minimum due to subsequent cropping on cold shear. For double covering each bar is independently aligned by preselecting the proper switches so as to reach the same target position. At the terminal end of rake type cooling area, are number of axial fans having speed regulation which increases the cooling efficiency by assisting heat dissipation from the bars in the convection range.

The bars having been aligned have new reached the end of cooling bed. These bars are to be transferred to the run out roller table (Item 86). The transfer facilities comprises two independently operating chain transfer 1 & 2 (Item 84 85). Chain transfer 1 (Item 84) receives one bar or two bars (depending upon single row/ double row covering) from moving rake one each of its stroke. Corresponding to each stroke of moving rake, the transfer will perform a stem movement. This will be repeated until a layer of pre determined width has been built up. If one or several notches will remain vacant due to a gap in cooling ed the respective collecting steps will have to be omitted, unless of course the required gap is to be maintained. Bar spacing and number of bars in each group will be governed by the straightener programme for material in need of straightening and by the maximum number of bars the cold shear can accommodate for material which need no straightening. These requirements are preselected in the cooling bed control pulpita and the entire operation of bar collecting in batches and transferring on run out roller table are under automatic function. The complete batch thus formed is then transferred into receiving position of chain transfer 1 and are picked up by discharge chain 2.

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Chain transfer 2 is lifting and lowering type having a carriage. The carriage lifts the material off the chain transfer 1 and moved it towards roller table and then lowers to deposit the batch. In case of roller table being occupied the batch can be held in delay storage by chain transfer-2 until the roller table has been run empty and ready to receive the material. The collecting of/ operating stroke of transfer chain 1 & 2 (Item 84 & 85) will be so monitered in case of batch transfer to roller table which needs straightening (single row covering of cooling bed) that the bars will be pulled apart depending upon the pitch of straightening roll profile and the first bar of each batch will always be positioned on the roller table in alignment with the pas centraline of spur roll, pinch roll and straightening roll. Materials which need no straightening will be collected in packs of maximum acceptable width without any spacing between individual sections and carried to the run out roller table and the conditions viz. spur roll up, entry pinch roll set down, straightening machine in pass line, roller table (Item 96) below the roller table the bar heads of the batch pass through straightener as per specified draw in speed. Pinch roll set will be opened and the straightener and roller tables are jointly accelerated to the specified straightening speed. When rolling materials which need no straightening, the straightener unit is shifted out of the rolling line and the gap created is filled by a gap bridging roller table. The entire pack of material deposited on cooling bed run out roller table will be transported to the roller tables downstream the straightener. The storage of cooling bed run out roller table provides signal for continuation of discharge process by chain type discharging device (Item 85).

COLLECTING BED AREA :

The straightened batch of bars or unstraightened pack of bars now approach a stop of roller table (Item 94) in order to put them on a flush line. Roller table (Item 94) stoppage is accomplished by the detection of material heads by a light barrier . There are four disappearing stops (Item 95) on each of the two run out roller table (Item 94). The selection of the particular top will be decided by the length of products being handled as well as least duration time of packs/ batches on roller table (Item 94) so that roller table (Item 94) can be made free to receive the next pack/ batch from cooling bed run out roller table (Item 86).

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The material pack or batch have now been brought to a stand-still against raised stopper (Item 95) and will be transported to the cold shear approach roller table (Item 99) across the collecting bed. These equipment basically align group of batches which have been straightened or packs not straightened against a raised/ lowered stopper and then make suitable shear layers according to the knife profile of cold shear.

The standstill material lying on roller table (Item 94) will be lifted automatically by the chain lifting system of chain type discharging device (Item 96) and then chain accelerated consistant with different type of sections resting on chains. After a certain travel when pack/ batch has moved past the roller table (Item 94) area, the chain is lowered to its aid position (aligning position). This releases the signal for roller table system to receive a new layer. The chain continues to move with its mid position and is brought to a rest when the material resting on it are in aligned position against the raised stopper (Item 97). At this point depending upon operating modes (whether forming a shear layer by separating a compacted aligned pack which has not been straightened) the control function of lowering of stopper (Item 97) and discharge chain (Item 96) and transport and compensating steps of chain type collecting and transfer device (Item 98) are so coordinated that the shear layer of suitable width with preset gap as per cold shear knife profile is formed over (Item 98). It is expected that a shear layer formed out of straightened batch will always contain multiple of batch. In otherwords one complete straightened layer will always be transferred at all times over the chain system.

Once the formation of shear layer has been completed the chain system (Item 98) will transfer the shear layer on to cold shear approach roller table (Item 99) and deposit the layer on it. Once deposited, formation of a next shear layer can be started. The deposited shear layer will now advance towards cold shear. On its way the layer will be intercepted by dia-appearing stop to bring the head ends into a flush line. The layer is now ready for cutting into predetermined sales lengths.

COLD SHEAR AREA :

There are two cold shear each on one line. Rebars and rounds from 10 to 20 diameter and square from 12 to 20 mm and flats will be sheared by flat knives whereas all other sections will be sheared by profiled knives. Desired finished lengths between 5 m & 12 m/ or maximum 24 m will be set by means of two electrically traversable gauge carriages which are attached to a grider type gauge.

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Precise cut lengths adjustment with digital display can be effected from control stand. Tail ends less than 5 m length which cannot be transported by roller table will either be cut into scrap pieces by the cold shear or in case they lie between the bar layers, they will be manually removed and discarded into a cardle near the cole shear. Al tail ends longer than 3 m will be transported along with sheared bunch and will be segregated by short bar removal system located downstream the cold shear.

FINISHING AREA :

The disposition of finishing facilities and underlength separation system downstream the cold shear are such that under normal automatic operation cold shear-1 or line-1 will normally cut bar from 5 12 m lengths for bundling and piling installation 1 and cold shear 2 or line 2 lengths 5-24 m maximum for bundling and piling installation 2. However, in case of breakdown, shear line 1 can continue cutting 5 25 m lengths depending upon the preselected sales length. These lengths will be diverted to bundling facilities 2. Layers with under lengths over 12 m will be ejected either into collecting pockets arranged on the opposite side of roller table (Item 104) or transported to bundling installation proper.

The two roller tables (Item 104 & 112) at back of cold shear 1 & 2 respectively convey the cut shear layers to its destined place i.e. either bundling 1 and piling 1 installation or piling 2 and bundling 2 installation depending upon preselected mode of operation. If any of these layers contain short length, it will be detected by operator at cold shear local desk and a signal is given for this layer to stop at its appropriate destination. Upon stoppage the layer will be transferred to short bar ejection system. After separation of short bars the layers will be again recycled on its normal flow path.

The roller table at the back of cold shear 1 (Item 104) has number of disappearing stops and an end stop at the terminal end of roller table. Depending upon the destination of layer and its length and degree of occupation, the respective stops will be operated (up or down) in conjunction with light barriers. The layers will be accordingly positioned in front of piling facility 1 and will be transported to the piling installation by a system of chain transfer. It must be however noted that at any time either the piling facilities or the bundling facilities are working.

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In case of shear layers coming from cold shear 2 for piling facility 2, respective layers are positioned are positioned on roller table (Item 112) by the action of preselected disappearing stops and then transferred to pilling facilities 2 directly without being lowered to roller table (Item 104) by a system of chain transfer (Item 114, 115, 116). However, layers coming from shear line 2 and meant for bundling facility 2 are lowered on roller table (Item 104) and further transferred to bundling facility 2.

If the rolling programme calls for bundling installation to function, the shear layers will have to be positioned in front of bundling facilities in such a way that the flushed bar and always remain in line with the location of bar counter. This is achieved in bundling facility 2 by flushing all bar ends against the fixed stop at the terminal end of roller table (104) so that bar heads will pass over counting wheels located downstream. The same is achieved in bundling facility 1 by making use of the rear gauge plate of shear gauge (Item 103) as a stop. The gauze plate is positioned and lowered in accordance with the length of shear layer and the layer is stopped against this gauge plate so that rear bar ends are always in flush line with the bar counter wheel disposed downstream the bundling facility 1. The piling facilities installed in this mill is capable of handling equal and unequal angles, channels, flats 50x8 and over and square 36 mm and over. The bundling facilities installed will handle round 12 to 40 mm diameter rebars 10 -25 m diameter, squares 12 x 38mm flats 30 m to 65 x 12 and T-Sections 50 x 50 x 6.

BUNDLING AREA :

The shear layer meant for bundling facilities transferred to the 1st chain system of bundling facilities. The bundling facilities essentially consists of three chain conveyor system, bar counter system, bundle holder, lowering arms, roller stands, bundle former etc. Shear layer are conveyed weighing 4.5 to 10 tons. The second conveyor system has a higher speed than 1st conveyor system, thereby spreading the bar for ease of counting by counter wheels. These spreaded shear layer is then taken over by the 3rd conveyor system and is transferred to the terminal end of conveyor. As the bar layer reaches the terminal end of conveyor 3, the speed reduced to the extent which is compatible with the counter wheel speed. Each bundling facilities has both types of counter wheel system (BBS and KNTC) suspended in a slewing bracket operated by hydraulic cylinders. The desired counter system as per the product handled are brought on the bar line and the bars are allowed to move over the counter wheels. A photo cell system counts the bar as they pass, under the photo cell beam and when the preselected number of bars have been counted the counter wheel as well as conveyor 3 stops.

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The preselected number of bar depends upon product being handled, its length and desired bundle weight. The counted bars have fallen on a bundle holder which gradually moves down to accommodate the bundle. The loose bundle along with bundle holder now moves down and the loose bundle along with bundle holder now moves down and the loose bundle is taken over by the lowering arm which carries the loss bundle to the roller stand. The loose bundle is now compacted by the bundle former into a tight bundle and binding machines run across the bundle and makes suitable number of wire ties depending upon the preselected programme. The binding machine essentially consists of wire feeding device, twisting unit with wire cutting device, clamping device and a wire guide track with cylinders for opening and closing. Wire is fed through a wire magazine and the entire machine run parallel to the binding object both for bundled and piles product and when positioned correctly as per programme, will a so move across the binding object and do the wire tying as explained above. The bundle now moves over roller table (Item 122) and is transported to weighing system (Item 124). The weighers are in turn connected to a label embosser, Pre-embossed labels are inserted on to this label embosser which embosses besides the actual weight, various other date viz. section of bundle, quality, heat number, pack number and length etc. Finished label will be attached to the respective bundle by operating personnel. The bundle is now transported to walking beam discharge devices and loading grid (Item 125). The pack/ bundles are lifted off the roller table by the walking beam and placed on the adjacent loading grid. The two halves of (Item 125) can be operated separately and jointly. The packs/ bundles are then picked up by means of finishing bay cranes.

PILING AREA :

Products that need piling will normally go to piling facilities. The shear layer for pliable products will be lifted by the lifting tables of chain system 116/117 and deposited on shear layer approach chain. This chain system carries the layer (each section of the layer spaced according to the shear knife profile) into an area where aligning ledges and part of shear layer approach chain system are lifted to a proper inclination for alignment of shear layer (gaps between the sections closed). Following this, the ledges go down and the aligned shear layer is moved by the chain system into a pack layer forming area. The shear layer stops against a fixed stopper. In this area pack layer widths are divided depending upto the product handled. In other words the entire aligned layer is subdivided and separated into a number of pack layers. In case of flats (higher size only), square (higher size only) and channels the pack layer width will be always the same for each successive pack, whereas for equal angles and unequal angles all odd pack layer widths will be same and all even pack layer widths will be smaller than odd layer packs.

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There are devices to set this pack layer width. When this device has been set for the particular sections being handled it will create a gap through which the required number of aligned se

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Tds its terminal and where they are lowered one by one on to pack layer feed chain. The feed chain transports the pack layer and position the layer with respect to adjustable aligning stopper position into pick up area of layer turnover magnets. The layer is lifted up by a lifting device and following this the magnets of layer turn over device is energized and the turnover device starts. The decision whether to us lifting table depends upon the packs to be turned or not to be turned in order to produce a nested arrangement on the piling table.

The magnet of the layer turnover device has two positions for layer pick up. Position 1 (swivel angle 120) is for pick up of pack layer from above the feed chain for layers not to be turned where-as position 2 (swivel angle 180) is for pick up of pack layer from below the feed chain for layers to be turned. However, the position for transfer of layer on to piling table will always remain the same. This device picks up packs, layer after layer as per preset programme of piling sequence and deposits them one by one on the piling table. The piling table designed specifically to accommodate packs of unequal angles also (inclined packet) moves down step by step (Programme dependent) in accordance with sections packed. When predetermined number of layers have been piled and the pack is complete the piling table is lowered into its bottom extreme position and is deposited on transport carriages of the pack and discharging device. The pack is now transported and as soon as the pack has cleared piling table, the table is again raised to its top position for its top position for continuation of formation of next packs. The complete pack, resting on carriages of discharging device moves and is deposited on roller table (Item -122) in front of fixed compacting rollers. The complete pack is now subjected to compacting by a system of horizontal and vertical compactors to bring the pack into a shape suitable for binding. The process of binding the packs by binding machine and its subsequent handling in weigher and loading grids is same as that described under bundling description.

-:: 17 ::-

EXISTING SYSTEM

Elevator System :

The blooms from the bloom yard are to be elevated to a height of +5 m because the blooms in the yard are placed at ground level.

To elevate the bloom the following operations are done :-

1) Blooms are rolled on to the roller table section in front of the elevator.

2) The lever type pusher serve to kick blooms lying on roller table to depositing ramps from where they are picked up by the elevator (the blooms are elevated by chain drive, rotated by a shaft which is connected to a motor).

3) There is a transfer mechanism which performs the operations like transferring the bloom on another roller table present at 5 m level.

LEVER TYPE PUSHER IN FRONT OF ELEVATOR

Functional Description :

The lever type pushers serve to kick blooms lying on the roller table sections in front of the elevators from the roller table to depositing ramps from where they are picked up by the elevator.

Provision must be made for the furnaces to be run empty in backward direction when a trouble situation occurs.

It is for this purpose that just like other equipment in four of the furnaces the lever type pusher must be reversible which means they must be capable of pushing the blooms from the depositing ramps to the roller table.

Design & Operation :

Each pusher substantially consists of 2 pusher arms moving in guide ways and at their forward end carrying 1 push off dog each while each rear end is hinged to a rocker lever. The 2 rocker levers are rigidly inter connected by means of a shaft. The push off system is driven by 2 pneumatic cylinders each cylinder acting on 1 of the levers.

-:: 18 ::-

PNEUMATIC CYLINDERS

Technical Data :

Cylinder Specifications

i)Piston dia

=250 mm

ii)Piston rod dia=70 mm

iii)Stroke length

=1000 mm

Extension rate =200 mm/sec.

Pressure Pmin=5 bar

Pmax=6 bar

Pneumatic System :Different components of pneumatic system are :-

1) Pneumatic Cylinder

2) Fitter

3) Regulator

4) Lubricant

5) Direction control valves (D.C. valves)

Pneumatic Cylinder :

There are three types of Pneumatic Cylinders:-

1) Single

2) Double

3) Through rod.

The cylinder present in lever type pusher is a double acting one.

The theoretical force available is :-

F=0.7854(D2 d2) x P double acting cylinder

D=Bore diameter d=piston rod

Filters :

The air filter will remove the dust and moisture and gives out pure air for working of cylinder.

In lever type pusher the filters are generally :

Liver Filters:- Because of the possibility of cooling occurring during the passage of air through the distribution rains, it is preferable to install individual smaller filters as near as possible to actual point of use of the air rather than a single large filter adjacent to the our receiver.

-:: 19 ::-

Regulator:- The regulator is used to regulate the quantity of air to be passed into the cylinder (1 c) of definite pressure and temperature.

Lubricant :- The lubricator is used to mix oil with compressed air so that while passing through D.C. Value, free moments of the valve can be attained.

Direction Control Valve :- The D.C. Valves used are way two position type. Its working is as follows :-

1) For 1st position the cylinder rod is compressed.

2) For 2nd position it expands.

It control the direction of air flow.

Working of Pneumatic System :-

Step 1) :- Air from the compressor house (which is present separately from LMMM) is passed through the FLRC filter, lubricant, regulator) and thus passes through D.C. Valve.

Step 2) :- The D.C. Valves when operated will be compress (or) expand the cylinder for the desired operation.

Working of Cylinders in LTP :-

When ever the piston is compressed, the lever moves back, causing the ramps on the abschie beam to drag the bloom on to the rails. Then the chain will elevate the bloom with the help of drops fixed to it.

(The Abschiehearm will slide on the ablege with the help of roller bearings)

PROBLEMS OF LTP (PENUMATIC CYLINDER)

Major Problem :- Initially when the cylinders are operated, the dogs carry the bloom up to rails, during its process its pressure is being reduced and the bloom stayed in its way for some moment ( ~ 1-2 sec). The system pressure predefined cope up to its pressure and finishes the rest of its journey (up to rails). Hence with this force the blooms passes on and hit the rails with greater impact force. Thus will cause rails to break.

-:: 20 ::-

Note :-To compensate this problem lubrication is being done, on the platform where the bloom moves. So that functional force herewith the contact surface is reduced and smooth running can be attained. But still the problem exists because of less friction force, and the rails break again.

MINOR PROBLEMS

Failure of Valves & FLR Circuit Purity of Air :-

Even though the air is filtered but still it contain small amounts of moisture and dust. As this air is being used the dust and moisture will cause failure to all of the components i.e., filters, lubricator, regulator, D.C. Valve and Cylinders.

DESCRIPTION :

1) The contaminated air when passed through filters causes clogging.

2) It then causes the lubricator and regulator to fail.

3) When (FLR) are not working properly then the air (dust + moisture) will cause the D.C. Valve and cylinders to fail.

4) The seals of the cylinders are continuously worn out due to this reason.

PROBLEMS OF ANALYSIS OF LTPSl. No.ProblemsEffectCaused Due to

1.Jerking movement of dogs- Failure of rails

- Failure of dogs (ramps)

- Failure of roller bearing.- Pressure drops (varieties)

(irregular moment of piston)

- The dog movement is not simultaneous.

- Speed cannot be controlled.

2.Clogging of filters regulator & lubricator system- replacement of filter, L, R (are being done) - Contaminated air during its flow from compressor house.

3Damage of seals & D.C. Valves- Replacement of Seals & Valves- do -

4Difficult to know the problem where it really lies.- Time taken process in knowing the problem- As the FLR circuit is before the process it is much difficult to know the problem.

5The rails are being damaged

(In present situation even though greece being applied but still the rails are failed)- Frequent welding of rail is being done)- The friction between the contact surface is reduced. Hence the force is sufficient to hit the rails by the bloom, causing the rails to break.

-:: 21 ::-

PROPOSED SYSTEM

CONVERSION OF PNEUMATIC SYSTEM INTO HYDRAULIC

Benefits of Hydraulics over Pneumatics

S. No.HydraulicsS. No.Pneumatics

1.Smooth running can be done in Hydraulic system1This process works roughly

2.Gradually force is applied2Force will be applied suddenly

3.Fluctuations at load can be hold 3.Variation of load cannot bare

4.Speed can be controlled4.Variation of load can not bare

5.Even though, any part is in failure, there is no damage to the entire system5.If any part fails, the entire system will damage.

HYDRAULIC SYSTEM

Hydraulic Circuits :-

Standards for representing hydraulic power system components have been developed to show symbolically the function and method of operation of each component. Symbols that represent hydraulic components are simple to draw and show the connection, flow paths, and functions of the hardware they represent.

-:: 22 ::-

Consider the circuit diagram :-

Oil from the tank is pump out by the piston pump. The pump used is an axial flow pump, piston pump generate the flow of hydraulic fluid by the reciprocating motion of piston within cylinder holes.

Axial piston pumps are available with cylinder blocks that usually contain five to nine pistons. The sequential discharge of the multiple piston produces a relatively continuous flow from the pump.

Hydraulic Hoses :Are classed according to the pressure rating, the steel or fiber reinforcement the number of braids (or) spiral plies and the material used for the cover. Hose sizes are designated by the nominal inside diameter of the hose, expressed in fractions of inches, for high pressure generally 5AE 100R2A are preferred.

Pressure relief valve :-The function of pressure regulating valves is to protect the components within the hydraulic circuit from damage from excessive pressure. These valves are usually caused safety relief valves. The most basic type is a poppet held against a core seat by a spring force when the pressure force on the end of poppet exceeds the spring force the poppet is lifted off the seat and fluid can escape back to reservoir.

Directional Control Valves :-D.C. Valves regulate the rate of flow that is permitted to operate individual hydraulic actuators. The D.C. Valve for the system may be four way, 3 position valve. The directional control valve is nothing more than a unit with which one can change the direction of movement or of operation of a pressure fluid.

This means that, by operating such a valve, we can direct the flow, e.g. from a pump, to one or other side of an actuator and thus introduce the required rotary, swivel, or linear movement, reverse it or, where there is provision in the valve for it, bring to a standstill. There are, therefore, at lest two switching positions. One is to direct the pressure fluid from the pump to the actuator and to return the fluid displaced by the actuator to the tank. In the second position this process is carried out in reverse, the pump flow being directed to the opposite side of the user and the fluid displaced from the other side being returned to tank.

In order to bring the motor to a standstill it is necessary to have a third position in the valve, which interrupts the pump flow to the actuator.

-:: 23 ::-Check Valves :-It permit free flow in one direction. They are constructed of a ball, flopper (or) poppet held lightly against a seat by a small spring force. Their only purpose is to prohibit flow reversals within the circuit.

Throttle (or) flow control valves:-A valve that can be in crementally moved axially to slowly open the flow path between two hydraulic lines is called a flow control valve.

Pressure Switch :-It is gauzed to the required pressure limits. If the pressure varies from the limits the flow is controlled automatically, by operating the solenoid connection of locating and unloading valves.

Coolant and Filters:-A well designed reservoir also will cool the oil. In many applications that cooling is insufficient in those cases an oil cooler must be used. Cooler usually are classified as either water cooled (or) air cooled. Air cooled coolers are similar to automotive radiatory dirt is one of the greatest enemies of hydraulic systems. As a consequence, filters are used to remove dirt particles otherwise the direct would cause wear of precision components and might even clog some very small passages. In all cases manufacturing and equipment operating procedures which minimize dirt ingestion should be followed.

Reserviour :-All hydraulic systems need a reservoir to store the oil and to provide a source of oil for the pumps suction line. A reservoir on a stationary hydraulic application should hold enough oil so that oil returning to the reservoir would have a residence time of a few minutes before it is reused. This promotes oil cooling and the release of entrained air.

Accumulator :-A component frequently used in hydraulic circuits is the hydraulic accumulator. It can perform various functions.

1) As a pressure fluid reserve In hydraulic systems where the operating cycle requires large flows to be available for short periods.

Here the accumulator helps to avoid the necessity of using a large pump requiring a high drive power capacity to suit the intermittent large flow requirement. The pump need only be large enough to recharge the accumulator during idling.

2) As emergency unit That is, as an energy source during brief pump failure, so that a work cycle already commenced can be completed, or to implement a safety cycle.

-:: 24 ::-

3) As leakage oil reserve for the maintenance of pressure to compensate leakage losses and to maintain pressure over a long period, e.g. for clamping and holding operations.

4) As anti-vibration device either for the prevention of pressure knocks, unpleasant operating noise resulting from system vibrations, or to claim pulsating flow from a pump.

5) To custom pressure surges during operating cycles, e.g. when using pressure switches or measuring instruments.

6) As fluid energy source for independent operation of auxiliary or pilot circuits when the pump flow is required to perform the main operation movements.

CHARGING SIDE EQUIPMENT

Design of System

Schematic drawings :-MEC/1/A-27681

27688

Hydraulic System I

The system serves charging side equipment at walking beam furnace and consists of following units :

a) Tanks Unit

- Tank of approx. 3000 litre capacity

- Return live duplex filter having degree of filtration as 20 micron

- Oil cooler shell and tube of capacity 56 KW.

b) Pump Station

- 7 axial piston type pumps (5 working and 2 as stand by)

Each with a flow capacity of 150 1 pm at 120 bar with motors of 45 KW at 1500 rpw motor.

c) Accumulator Stands

- 2 accumulator stands, one with two and other with bladder type accumulators of 32 litre capacity.

d) Valve stand # 3 for bloom pushes for following operations drawing No. HEC/1/A 27688.

1)Bloom pusher I- Forward - Stop - Reverse

2) Bloom Pusher II-Forward - Stop - Reverse

-:: 25 ::-

DESCRIPTION OF THE DIFFERENT UNITS

Hydraulic System :

Tank Unit-The Oil tanks, as well as its accessories such as return line filters and heat exchanged have been designed in accordance with the total pump package capacity and motor output.

The tank (1 B) is designed for holding the 4 or 5 fold capacity circulating in the pump in order to obtain a relatively long life time of the operating fluid.

Cleaning opening permit easy access to the tank inside

The oil level is optically and electrically controlled by means of level gauze (58) and level switch (60) respectively :

-Contact 1 give Oil level high signal

-When oil level falls down below normal level, contact 2 give Oil level low signal

Should this warning not be observed and the oil level keep on falling all the pump motors are switched off by the contact No.3. The switch off operated by the latter contact takes place for safety reasons when the oil level is still higher than the highest point of the suction connection so that the pumps are prevented from sucking in air.

The oil returns to the oil tank via the return line duplex filter (one operating the other as stand by) where it is filtered degree of filtration of the filter is 20 micron. Differential pressure switch is provided across filter to give filter choke signal, if filter choke resulting in increase of pressure differential.

The dissipated energy occurring in the hydraulic system is converted into heat which reaches the oil tank via the heated oil. An appropriate cooler is fitted in the return line in order to prevent the oil returning to the pump from becoming warmer than 50C in water inlet line to cooler, a temp regulating valve is provide which regulating water flow through cooler depending upon tanks oil temperature.

Breathers mounted on top of the tank secure sufficient ventilation of the tank. The temperature in the tank is indicted by thermometers attached to the tank.

A thermostat has been provided in tank to give oil temp high signal when temperature exceeds set temp of 65C.

-:: 26 ::-

Pump Station :

The pump deliver oil through the non return valve into the common pressure pipeline of the system. One solenoid operated unloading cum relief valve is provided which unloads or loads pump depending upon oil demand by the system cylinders. During unloading condition, pump delivery is by passed to tank at low pressure.

When pump motor is switched on, the pump starts in unloaded condition. After a set time in time relay 0.5 2 seconds, the solenoid of venting relief valve gets energized, the pump gets loaded and fluid goes to system.

During normal operation, pumps loading (or) unloading are controlled by pressure switches. Depending upon the setting, when the system pressure exceeds maximum set pressure of pressure switch. The corresponding pump gets unloaded due to de-energisation of solenoid of venting relief valve.

When system pressure goes down below minimum set pressure of pressure switch, the pumps gets loaded due to energisation of solenoid of renting relief valve.

If a particular pump remains in unloaded condition for more than 15 minutes, the associated pump motor will be cut out. When system pressure falls down, the pump motor will restart and pump loading takes place as happens during initial start up.

The pressure switches arranged in the hydraulic station are not all set for the same pressure so that the pumps operated with in a pressure switching range between 95 and 120 bar. In order to ensure uniformity of the pressure and of the delivery volume the pressure switches are set differently to suit the operating.

Conditions concerned as, there are seven selector switches in panel each with six positions for selecting pressure switches.

Pressure Switch

Operating Range

1 From 95 to 120 bar

2 From 100 to 120 bar

3 From 105 to 120 bar

4 From 110 to 120 bar

5 From 110 to 120 bar

6 From 110 to 120 bar

-:: 27 ::-

The valves indicated above must, however, be corrected on the basis of the pressure conditions concerned.

The stand by pressure switches shall be set to range so to 90 bar for Low Pressure signal in the system limit switches are provided at valves in suction line to pumps.

Pumps motors can be started if and when :

1) Associated pump suction valves are open

2) Main suction valve at tank is open

3) Shut off valve in line from main tank to spent oil, station is closed.

4) Oil level is above lowest level.

Accumulator Stands :

The rubber bladder in accumulators is prefilled with nitrogen to a pressure of 70 bar.

A safety block is provided for each accumulator which his tested in the shops of the makers in accordance with the regulations of Techmisher under wachungesere in and lead sealed. The lead seal must most not be removed in any case because an acute danger of overloading exist.

A pressure gauze is provided for each station which directly indicates the pressure.

A charging and testing device (109) is supplied for all accumulators.

The no. of valve stands and no of control circuit in each valve stands are given point. The valve stands are of manifold design where in different component of a control circuit are mounted on a steel manifold block, there by reducing no. of pipe joint which is called for a conventional piped up type valve stands sourcer of leakage gets reduced and look wise, the valve stand looks compact.

For the recommend hydraulic system the following design aspects may be applied.

Technical data of pneumatic system is :

Stroke length

=1000 mm

Piston dia

=250 mm

Piston rod dia=70 mm

Pressure

=5 bar

-:: 28 ::-

Expected Hydraulic System parameter are :

1) Stroke length=1000 mm

2) Piston rod dia=70 mm

3) Pressure

=100 bar

4) Considering the force in pneumatic is twice than its original piston dia will be obtained by equating the forces in both the systems.

F O R C E =PRESSURE X AREA

FPneumatic

=FHydraulic

2[(/4 (2502 702)]x 5=[(/4 (D2 702)] x 100

D

=105 mm

Let D be adjusted to 100 mm

1) Stress in cast iron = 280 (As the system pressure is 100 bar cast iron covers can be used.)

Thickness t = P.D= 100x100 = 17.8 ~ 20 mm

2x5 2 x 280

Actual Thickness

t=Pw.D x F + C

2 x 5m

TakingF = 1.2C = 1

t = 22.42~ 25 mm

Thickness lies between (20 25 mm)

2) Maximum Hoop stress

S=D2 2t + 2t2 x P

2t (D t)

=1002 2 x 25 + 2 x 252 x 100

2 x 25 (100 25)

=298 ~ 300 bar

S=300 x 105 N/m2-:: 29 ::-

Strength of Cylinders

The diameter : thickness ratio of the cylinder tube is greater than 16 : 1, the stress produced in the wall material due to internal pressure can be determined by

S=P.D

2t

Where S=Hoop stress

P=Internal Pressure

D=Internal Diameter of tube

t=Wall thickness

This can be rendered in the form of

t=Pw D x F + C

2 SmWhere Pw =Design working pressure

Sm=Maximum permissible material stress

F=Design factor of safety

C=An additional thickness allowance for corrosion.

For thick walled homogenous tubes the stress is no longer uniformly distributed through the tube walls, when the max hoop stress is given more accurately by

S=D2 2t + 2t2 x P

2t (D t)

Typical values for maximum permissible material stress being:

Cast Iron

-280 bar

High duty cast iron

-420 550 bar

Cast steel

-840 bar

Cast aluminum alloy-550 bar

Cast brass

-420 bar

Cast bronze

-420 bar

The strength of low carbon mild steel is substantially increased by cold working, with a potential ultimate tensile strength of the order of 6300 bar (40 tons/ in2) after cold drawing and deep polishing.

-:: 30 ::-

Honing :Honing is a normal minimum finish for drawn cylinder tubes, not only to give a smooth and more uniform finish but to produce a more favorable surface pattern than that resulting from drawing.

End Covers : End covers are usually but not invariably made from the same material as the cylinder to be the main variation is in the method at fitting the end caps.

Pistons : Materials used for pistons include cast iron or steel, brass, bronze and aluminum alloy, also sintered iron and steel. The most common method of attaching the piston to the piston rod is to machine a shoulder on the rod with a threaded end. The piston then locates on the shoulder and is held in place by a nut. For heavier duties, the piston may be welded to the rod, and for lighter duties simply located by circlips.

PROBLEMS RECOVERED BY HYDRAULIC IN LEVER TYPE PUSHER

1) Major Problem :

Jerking of Clogs

As the Hydraulic system contains higher pressure and gives smooth movement. There is no problem of jerking of clog.

2) Minor Problem :

As the coolant and filter are situated at the end of the process. Its failure (clogging) will not effect the process.

3) Damage of Seals and D.C. Valves :

If we maintain clean oil, by continuous rating of oil purity, the damage of seals and D.C. Valves may be reduced to larger extent.

4) Difficulty to know the problem where it really lies :

By closing different shut off valves and noting the pressure by pressure gauzes, we can say where the problem is.

-:: 31 ::-

RECOMMENDED HYDRAULIC SYSTEM:

a) Consider (A B) line

Initially when the shut off valve opened oil is sucked by the pump and the oil flow starts up. The below of the pump and hose pipe connection are meant for the vibration damping. The oil than passes through check valve and goes on up to D.C. Valves and make it operated. The accumulator acts as a reservoir for the fluid flow in case of flow variations. The pressure switch is adjusted to maximum and minimum pressure required. It is switch off if at all the pressure changes from these valves. The filter and coolant are placed at the end of the circuit where they clean the used oil in the process.

b) Consider (C D) line from fig.

The loading and unloading valve is meant for supply of fluid to the system when ever necessary. If at all the valve is in on position the fluid in the line breaks and makes the system to work and when it is in off position the fluid is short cutted to flow to the tank. There is a pressure relief valve in this line. If the valve does not work properly the pressure relief valve stops the system by continuous flow of oil to tank.