CnW maintenance manual-232-382 PDF

CHAPTER 7 – AIR BRAKE SYSTEM Page 1 of 151 CHAPTER 7 AIR BRAKE SYSTEM 701. CLASSIFICATION OF AIR BRAKE SYSTEM On the basis of type of release, air brake system is cl...

CHAPTER 7 – AIR BRAKE SYSTEM Page 1 of 151 CHAPTER 7 AIR BRAKE SYSTEM 701. CLASSIFICATION OF AIR BRAKE SYSTEM On the basis of type of release, air brake system is classified as:  Direct release air brake system  Graduated release air brake system Both Direct and Graduated release are further available in two forms viz.  Single pipe and  Twin pipe The diagram shown in fig. 7.1 illustrates the schematic layout of air brake equipment on the under frame of freight stock. As shown in figure, the single pipe graduated release air brake system consists of following components:- i) Distributor valve ii) Common pipe bracket with control reservoir. iii) Auxiliary reservoir.100 Litres & 75 Liters iv) Three way centrifugal dirt collector. v) Isolating cock. vi) Brake cylinder 355mm diameter & 300 mm diameter. vii) Cut off angle cock (32mm size on either ends of brake pipe & feed pipe). viii) Air brake hose coupling (32mm for brake pipe / 32 mm from feed pipe). ix) Brake pipe/feed pipe (32mm dia). x) Branch pipes from BP to brake equipment (20mm bore). xi) Guard emergency brake valve. xii) Pressure gauges for BP xiii) Quick Coupling. Recently, Bogie mounted Brake System (BMBS) has also been introduced for freight stock. The details of BMBS for freight stocks are given in Para 729 of this chapter 702. PRINCIPLE OF OPERATION OF SINGLE PIPE GRADUATED RELEASE AIR BRAKE SYSTEM Some of the Air Brake goods stock on IR is fitted with single pipe graduated release air brake system. In single pipe, brake pipes of all wagons are connected. Also all the cut off angle cocks are kept open except the front cut off angle cocks of BP of leading loco and rear end cut off angle cock of BP of last vehicle. Isolating cocks on all wagons are also kept in open condition. Auxiliary reservoir is charged through distributor valve at 5.0 kg/cm2. WAGON MAINTENANCE MANUAL  Page 2 of 151 Fig. 7.1 GRADUATED RELEASE SINGLE PIPE AIR BRAKE SYSTEM CHAPTER 7 – AIR BRAKE SYSTEM Page 3 of 151 A. Charging stage Fig. 7.2 CHARGING During this stage, brake pipe is charged to 5kg/cm2 pressure which in turn charges control reservoir and auxiliary reservoir to 5 kg/cm2 pressure via distributor valve. At this stage, brake cylinder gets vented to atmosphere through passage in Distributor valve. B. Application Stage Fig. 7.3 APPLICATION WAGON MAINTENANCE MANUAL  Page 4 of 151 For application of brakes, the pressure in brake pipe has to be dropped. This is done by venting air from driver‟s brake valve. Reduction in brake pipe pressure positions the distributor valve in such a way that the control reservoir gets disconnected from brake pipe and auxiliary reservoir gets connected to brake cylinder. This results in increase in air pressure in brake cylinder resulting in application of brakes. The magnitude of braking force is proportional to reduction in brake pipe pressure Note: 1. Brake Application takes places when Brake pipe pressure is dropped. 2. The drop of pressure may be a) Intentional and b) Accidental. C) Release stage Fig. 7.4 RELEASE For releasing brakes, the brake pipe is again charged to 5 kg/cm2 pressure by compressor through driver‟s brake valve. This action positions distributor valve in such a away that auxiliary reservoir gets isolated from brake cylinder and brake cylinder is vented to atmosphere through distributor valve and thus brakes are released 702A. PRINCIPLE OF OPERATION OF TWIN PIPE GRADUATED RELEASE AIR BRAKE SYSTEM Some of the Air Brake goods stock on IR is fitted with Twin pipe graduated release air brake system. In Twin pipe, brake pipes and feed pipes of all wagons are connected. Also all the cut off angle cocks are kept open except the front cut off angle cocks of BP/ FP of leading loco and rear end cut off angle cock of BP and FP of last vehicle. Isolating cocks on all wagons are also kept in open condition. Auxiliary reservoir is charged to 6.0 Kg/cm2 through the feed pipe. A. Charging stage During this stage, brake pipe is charged to 5 kg/cm2 pressure and feed pipe is charged to 6 kg/cm2 pressure which in turn charges control reservoir and auxiliary reservoir to 6 kg/cm2 pressure. At this stage, brake cylinder gets vented to atmosphere through passage in Distributor valve. CHAPTER 7 – AIR BRAKE SYSTEM Page 5 of 151 B. Application Stage For application of brakes, the pressure in brake pipe has to be dropped. This is done by venting air from driver‟s brake valve. Reduction in brake pipe pressure positions the distributor valve in such a way that the control reservoir gets disconnected from brake pipe and auxiliary reservoir gets connected to brake cylinder. This results in increase in air pressure in brake cylinder resulting in application of brakes. The magnitude of braking force is proportional to reduction in brake pipe pressure Note: 1. Brake Application takes places when Brake pipe pressure is dropped. 2. The drop of pressure may be a) Intentional and b) Accidental. C. Release stage For releasing brakes, the brake pipe is again charged to 5 kg/cm2 pressure by compressor through driver‟s brake valve. This action positions distributor valve in such a way that auxiliary reservoir gets isolated from brake cylinder and brake cylinder is vented to atmosphere through distributor valve and thus brakes are released. Do‟s and Don‟ts for Twin Pipe working of Freight Trains Do‟s: 1. Do ensure that the all twin pipe Wagons are operated in CC rakes only. 2. Do ensure that loco provided for twin pipe rake is having its twin pipe in working condition. 3. Do ensure availability of spare pool of twin pipe wagon & brake van, for replacement, if required. 4. Do ensure availability of spare feed pipe in loco. 5. Do ensure that brake van provided for twin pipe working is having twin pipe system. 6. Do ensure BP coupling heads are marked with „BP‟ and painted in green. 7. Do ensure FP coupling heads are marked with „FP‟ and painted in white. 8. Do ensure that BP & FP hose couplings at the rear end of the train are placed on their respective hose coupling supports. 9. Do ensure that pressure gauges for BP and FP are provided in the brake van. 10. Do ensure that brake pipe/feed pipe angle cocks are not closed under any circumstance, either for isolation of wagons or for any purpose whatsoever, except for carrying out shunting operation, after which the angel cocks should again be opened to ensure continuity of brake pipe and feed pipe. 11. Do ensure that the isolating cock of feed pipe of all the wagons in the open position. The handle of cock shall be vertically down when open and at horizontal when closed. 12. Do ensure that gauge in guards compartment show pressure not less than 5.8 kg/cm2 in feed pipe after the system is fully charged. 13. Do ensure that feed pipe hose coupling are connected to form a continuous passage from locomotive to last vehicle. 14. Do ensure that feed pipe Cut off angle cocks, except at the rear of train, are kept open. 15. Do ensure availability of the quick coupling for attaching and detaching the pressure gauges for BP/FP in brake van. WAGON MAINTENANCE MANUAL  Page 6 of 151 16. Do ensure that the leakage in brake system is less than 0.25kg/cm2 per minute. 17. Do close BP/FP angle cocks of adjacent wagons to uncouple hose couplings. DON‟Ts 1. Do not allow single pipe coupling. 2. Do not allow a feed pipe to be connected to the brake pipe anywhere in the train or vice versa. 3. Do not allow a feed pipe hose coupling at rear end to dangle. 4. Do not allow train to leave with leakage higher than specified. 5. Do not allow train to leave with feed pipe pressure in loco and brake van less than specified. UNCOMMON ITEMS FOR TWIN PIPE AIR BRAKE SYSTEM Items Description & dimensions Nos./ Ref. Drg. Wagon 1. AIR BRAKE HOSE COUPLING (F.P.) 2 WD-81027-S-01 2. ISOLATING COCK 1 WD-83062-S-04 3. CHECK VALVE 1 WD-83062-S-03 4. PIPE 20 N.B. 1 5. PIPE 20 N.B. 1 Respected different 6. PIPE 20 N.B. 1 drawings of different wagons. 7. PIPE 32 N.B. (F.P.) 1 8. PIPE 32 N.B. (F.P.) 1 MARKING OF TWIN PIPE AIR BRAKE FITTED WAGONS For easy identification of these wagons, „Twin Pipe‟ written in black letters on yellow background and encircled in white band shall be marked on side panel, one side in English and other side in Hindi as specified in RDSO drawings. NOTE: For further details please refer Annexure XIX of G-97 ammandment No. 3 of Jan. 2010 for “General guidelines for operation and examination of Twin Pipe Air Brake system of complete train” and RDSO repot No. MP. Guide No. 11 (Rev. -01) “Procedure for checking of Diesel/Electric locomotive Hauled Air Braked Trains (Fitted with twin pipe air brake system)” AIR BRAKE SUB ASSEMBLIES 703. COMMON PIPE BRACKET Common pipe bracket is permanently mounted on the under frame of a vehicle. The distributor valve along with the intermediate piece (sandwich) which houses the isolating cock is mounted on one face of the common pipe bracket. The control reservoir is mounted on the other face of the Common pipe bracket. CHAPTER 7 – AIR BRAKE SYSTEM Page 7 of 151 The Common pipe bracket has been evolved with the purpose of making it suitable for use with any make of distributor valve adopted on Indian Railways. Common pipe bracket is a sturdy casting with internal air passages, matching the intermediate piece mounting face with accurately profiled air cavities and flanged ports leading to the appropriate ports of the distributor valve. Branch pipes to the brake pipe and brake cylinders are fitted on the appropriate ports on the common pipe bracket. The advantage of fitting a common pipe bracket is to remove the distributor valve for repair or replacement without disturbing the pipe connections. 704. INTERMEDIATE PIECE (SANDWICH PIECE) Intermediate piece serves the purpose of blanking all the other ports on the common pipe bracket front face other than required for a particular make of distributor valve. Each type of distributor valve is mounted on the common pipe bracket with its own intermediate piece (sandwich). Intermediate piece is mounted on the common pipe bracket face with a common gasket and the distributor valve is fastened to the intermediate piece. Isolating cock for distributor valve, which is housed in the intermediate piece is for isolating the distributor valve in case of malfunctioning or for disconnecting the brake pipe pressure. Isolating cock on intermediate piece has a built in venting arrangement. 705. BRAKE PIPE HOSES Fig. 8.5 In order to connect two successive wagons, the brake pipes (BP) & Feed Pipe (FP) installed on the underframe are fitted with flexible hoses. The hoses are named as BP/FP hose. 706. BRAKE PIPE COUPLING To connect subsequent wagons, the hoses of BP are screwed to coupling and hose nipple by means of stainless steel `Bend it‟ type clips. The coupling is specially designed in the form of palm end and hence also known as palm end coupling. For easy identification the couplings are engraved with letter BP and coupling heads are painted green Note: Design, controlling dimensions, material and specification of components shall conform to the latest revision of RDSO drg. No. SK-73547 for BP, WD-81027-S-01 for FP and appendix F of 02 ABR 02 of RDSO specification. The air brake hose couplings are provided in the brake pipe line throughout the train for connecting the brake pipe of adjacent wagons to form the complete rake. Each Air Brake Hose coupling consists of a specially manufactured rubber hose clamped over a WAGON MAINTENANCE MANUAL  Page 8 of 151 nipple on one end and a coupling head on the other end. Rubber sealing washers are provided on the outlet port of the coupling head. Since a joint is formed at the coupling head, leakage may take place, through it. Therefore it is necessary to subject the hose coupling of brake pipe to leakage test. A. TOOLS AND EQUIPMENTS a) Test stand (Fig. 7.6) Test stand for testing of the hose coupling consists of the following main equipment 1) Supply of compressed air at – 10 Kg/cm2 2) Isolating cock – 1a and 1b 3) Exhaust cock – 1c 4) Main reservoir 5) Pressure gauge  6a for main reservoir  6b for flexible hose 6) Flexible hose - for connecting hose coupling for immersing in to water. 7) Water tub with safety cage – for checking leakage from hose coupling. 8) Dummy coupling head. b) TEST PROCEDURE For testing the hose coupling the steps given below should be followed: i. Use a dummy coupling head to block the outlet port of the hose coupling. ii. Connect to hose coupling under test to the end of flexible hose. iii. Open isolating cock 1(a) iv. Adjust pressure regulator (2) so that pressure gauge (6a) shows 10Kg./cm2 air pressure. v. Immerse the hose coupling assembly completely in the tub of water. vi. Open isolating cock (1b) and see that (6b) shows 10 Kg/cm2 pressure. vii. Observe leakage, if any from all parts of the hose coupling. viii. Close the isolating cock 1(b). ix. Disconnect the hose coupling from test bed. x. If the leakage is observed through the coupling head, replace the gasket and test again. xi. If leakage persists even after change of gasket the coupling head is unserviceable and complete assembly shall be rejected. However if leakage occurs at the hose nipple or coupling end hose joint the clamp should be attended/replaced to make the assembly leak proof. c) SAFETY PRECAUTIONS  Specified tools and fixtures should be used for connecting and disconnecting the hose coupling with the air supply.  While testing the hose coupling before charging it to 10kg/cm2 pressure, the tube should be covered and locked with a protective cage. CHAPTER 7 – AIR BRAKE SYSTEM Page 9 of 151  Exhaust the pressure from the hose coupling under test, before lifting the safety cage and uncoupling it.  After testing, the hose assembly shall be stored in a dry and clean space. The inlet and outlet port must be plugged with protective cap to prevent entry of dust and foreign particles inside the hose coupling. 1 ¼ “ BSB SOCKET TO COUPLE HOSE NIPPLE END COUPLING (10 KG/CM2 CAL) HIGH PRESSURE FLEXIBLE HOSE CHARGING PRESSURE GAUGE 1c Fig.7.6 TESTING OF HOSE COUPLING EXHAUST COCK 6b ISOLATING COCK 1b MR RESERVOIR 6a MAIN PRESSURE REDUCER 2 ISOLATING COCK 1a WAGON MAINTENANCE MANUAL  Page 10 of 151 707. CUT OFF ANGLE COCK Fig. 7.7 Cut off angle cocks are provided on the air brake system to facilitate coupling and uncoupling of air hoses (i.e. brake pipe). When the handle of the cut off angle cock is placed in closed position it cuts off the passage of compressed air, there by facilitating coupling and uncoupling action. If coupling action has to be performed on a given rake, ensure that the cut off angle cock provided at the end of the brake pipes are closed. By doing this the compressed air gets cut off and does not enter into the brake pipe air hose. The air hoses without compressed air can thus easily be coupled without any jerk. Similarly during uncoupling the cut off angle cocks of subsequent wagons should be closed. By doing so the air present in the brake pipe air hose gets leaked through the vent provided in the body of the cut off angle cock. Finally the air hoses get emptied and thus can be easily uncoupled without any jerk. The cut off angle cock consists of two parts viz. cap and body which are secured together by bolts. The cap and the body together hold firmly the steel ball inside it, which is seated on rubber seat. The ball has a special profile with the provision of a groove at the bottom portion for venting the air to the atmosphere. On the top surface of the body a bore is provided for placing the stem, to which a self locking type handle is fixed. When the handle is placed parallel to the cut off angle cock the inlet port of the cut off angle cock body is connected to the outlet port, through the hole provided in steel ball. Thus air can easily pass through the cock. This position of the handle is known as open position. When the handle is placed perpendicular to the cock body the steel ball gets rotated and the spherical and groove portion of the ball presses against the sealing ring at inlet and outlet port, there by closing the passage of inlet air and venting the outlet air through the vent hole. This position of the handle is known as closed position. With the stem one leaf spring is provided which presses the operating handle downwards. By virtue of this, handle gets seated in deep grooves at ON/OFF position resulting in a mechanical lock. CHAPTER 7 – AIR BRAKE SYSTEM Page 11 of 151 Under normal working conditions, the handle of all cut off angle cock of BP are kept open except the rear end angle cock (BP). This facilitates in charging the complete air brake system with compressed air supplied by the compressor housed in the locomotive. Cut off angle cock fitted on the brake pipe is painted green. Note: The dimension and tolerances of cut off angle cock shall be as indicated in latest revision of RDSO drawing nos. WD-88123-S-01 and WD-88123-S-02. Since a number of manufacturers exist for air brake equipment and component, refer to concerned original manufacturer‟s maintenance manual for part no. and description of spares. A. OVERHAULING OF CUT OFF ANGLE COCK These angle cocks are of ball-type ensuring better sealing against leakage and facilitate ease of operation. During overhauling, it is dismantled for cleaning, replacement of parts and checking for effective functioning. The cut-off angle cock is to be completely dismantled and overhauled during POH or when there is some specific trouble. a) TOOLS & EQUIPMENT The following tools and fixtures are required for overhauling (I) Single end spanner. 1) A/F 17 for M10 nut pivot screw. 2) A/F 10 for M6 nut. (II) Screw driver 12”/300 mm long. (III) Vice. (IV) Light hammer. b) PROCEDURE Dismantling  Hold the cut – off angle cock in vice.  Unscrew the lock nut from the stem.  Take out the handle assembly (The handle assembly need not be dismantled further unless it is necessary to change the plate spring i.e. if it is found, heavily rusted, pitting crack or the spring is permanent set).  Unscrew the four hexagonal bolts and spring washers.  Detach cap from the body.  Remove „O‟ ring and ball seat from the cap.  Turn the stem in such a way that the ball can be pulled from the stem.  Slightly hammer the stem at its top and take out the stem through the bore of the body.  Remove the ball seat from the body. c) Cleaning of Parts  Clean out side portion of the body and cap with wire brush. WAGON MAINTENANCE MANUAL  Page 12 of 151  Direct a jet of air to remove the dust.  Clean all metallic parts with kerosene oil and wipe dry. d) Replacement of Parts  Replace all rubber parts.  Replace spring-washer, nut & bolts in case they are excessively corroded or defective.  Replace handle spring if it is found heavily rusted, is having pitting crack or is permanently set (Dismantle the handle assembly, and fit a new spring along with a snap head rivet).  Replace stainless steel ball if found with scratch marks on the outer surface or dented. e) Assembly  Insert the two „O‟ rings in their respective grooves on the stem.  Keeping the threaded end of the stem first, insert the stem into the body through the bore of the body.  Place one ball seat in its groove inside the body.  Position the ball after correctly aligning its venting slot in the bore of the body.  Place the second ball seat and „O‟ ring in their respective positions on the cap.  Secure the body and cap by Hex. Hd. Bolt (M6) and spring washer (for M6).  Place the handle assembly on the stem and secure it with Hex. Hd. Nut (M10).  During assembly apply a light coat of shell MP2 or equivalent grease on the external surface of the threads and the ball. B. TESTING OF CUT–OFF ANGLE COCK a) TOOLS AND EQUIPMENT i. Test Bench ii. Compressor to build pressure more than 10 kg/cm2. iii. Single ended spanner as per IS 2027 a) Across face 17 (for M10 lock nut) - 1 No. b) Across Face 13 (for M8 studs) 2 No. iv. Screw Driver –300mm, 1 No. v. 1 ¼ “ BSP dummy Plug with seal. vi. Dummy plug for angle cock. CHAPTER 7 – AIR BRAKE SYSTEM Page 13 of 151 b) TEST PROCEDURE Following test procedure should be adopted step by step for performing the leakage test. i. Mount the angle cock on the base of the test bench (Part No. 7 of the figure of the test bench). ii. Move the handle to the closed position. iii. See that cock (1e) and (1c) are in closed position. iv. Now open cock 1(a) and 1(b) till MR indicates a pressure of 10 Kg/Cm2. v. If necessary, adjust pressure regulator (2) to maintain the pressure at 10 kg/Cm2. vi. Open cock (1c) and check the leakage with soap solution. There should not be any leakage. vii. Check pressure drop in gauge (6b) there should not be any leakage from flange joints, vent and outlet port of the angle cock. viii. Close cock (1c) and tighten the dummy plug and seal the outlet of the angle cock. ix. Move the handle to the open position. Open cock 1c. x. Check for leakage from body and cap joint, vent and all over the stem periphery using soap water. No leakage is permissible. xi. Move the handle to closed position and notice a short blast of air through the vent. xii. Close cock 1c then Open cock (1d) and exhaust the pressure to zero. xiii. Remove the angle cock. xiv. Report results of the test. c) SAFETY PRECAUTIONS  Specified tools and fixtures should be used for assembly and disassembly operations.  The small metal parts like leaf spring, nut, bolts, washers, screws etc should be kept in a safe place and replaced in case found defective.  Inlet and outlet port of the tested angle cock should be plugged with protection cap to prevent entry of dust and moisture inside the cut off angle cock.  Ball should be handled carefully to avoid any damage on its surface.  Threaded portion of body and cap should not be damaged at the time of dismantling. WAGON MAINTENANCE MANUAL  Page 14 of 151 708. BRAKE CYLINDER (Note: Anti-rattler ring shall be provided on brake cylinder for passenger stock) Fig. 7.8 BRAKE CYLINDER On every wagon fitted with air brake system one brake cylinder is provided for actuating the brake rigging for the application and release of brakes. During application stage the brake cylinder receives pneumatic pressure from the auxiliary reservoir after being regulated by the distributor valve. There after the brake cylinder develops mechanical brake power by outward movement of its piston assembly. To transmit this power to the brake shoe, the push rod of piston assembly is connected to the brake shoe through a system of levers to amplify and transmit the brake power. During release action of brakes the compression spring provided in the brake cylinder brings back the rigging to its original position. The cylinder body is made out of sheet metal or cast iron and carries the mounting bracket, air inlet connection, ribs and flange. To the cylinder body, a dome cover is fitted with the help of bolts and nuts. The dome cover encloses the spring and the passage for the piston trunk, which is connected to the piston by screws. The piston is of cast iron having a groove in which piston packing is seated. Piston packing of rubber material which is of oil and abrasion resistant and unaffected by climatic changes. It is snap fit to the piston head and has self lubricating characteristic which ensures adequate lubrication over a long service period and extends seal life considerably The piston packing also seals the air- flow from the pressure side to the other side and is guided by the wear ring. The wear ring prevents the friction between cylinder body and the piston head. The piston sub assembly incorporates a push rod, which can articulate and take minor variations in alignment during fitment/operation. Note: The dimension and tolerances of brake cylinder shall conform to the latest revision of RDSO drawing number WD-92051–S 06, WD-92051-S-07, WD-92051-S- 08, WD-92057-S-09, WD 92051 –S-09, WD 94048-s-01, WD 92051 –S-11, WD 92051 –S-12, WD 92051 –S-13, WD 92051 –S-14 and WD 92051 –S-15. CHAPTER 7 – AIR BRAKE SYSTEM Page 15 of 151 A. OVERHAULING OF BRAKE CYLINDER Brake cylinder has to be thoroughly overhauled for efficient and reliable trouble free performance during its prolonged service life. The complete overhauling of the brake cylinder is to be carried out during POH or when there is some specific trouble. a) TOOLS & EQUIPMENT Sr. No. Description 1. Torque Wrench 0-3 Kg range 2. Double End Spanner 24x27 mm across face (For M16) 3. Double End Spanner across face 13x14 (For M12) 4. Socket Wrench 19 mm (For M12) 5. Screw Driver 12" (300 mm) 6. Special fixture (Screw press/ Pneumatic) 7. Gauge for examining bore of the cylinder b) Dismantling of Brake Cylinder Before dismantling the dome cover insert a rounded head pin of 12x25 long and secure one of the hole in the piston trunk for the purpose of safety to prevent dome cover working out of the piston rod due to the cylinder return spring force while opening the dome cover with the help of a special fixture clamp the dome cover.  Unscrew the Hex. Hd. nut and take out the spring washer on the dome cover.  Turn the handle of the fixture to release the clamp and withdraw the holding clamp of the fixture till the return spring inside the cylinder is fully expanded and free.  Remove the dome cover and take out the return spring.  Remove the bush on the rod and brake cylinder.  Remove the piston rod sub-assembly, piston ring packing, wear ring and slide out the anti rattler ring from the piston rod.  Unscrew the CSK, head screw and separate the piston, pin, piston trunk & piston rod assembly.  Unscrew the brake cylinder plug at the rear end. c) Cleaning of Parts  Blow a jet of air to clean the dust on the external surface.  Clean the metallic parts using wire brush and kerosene oil.  Clean the internal parts with nylon bristle brush.  Clean piston packing, wear ring and rubber parts with soap water solution. WAGON MAINTENANCE MANUAL  Page 16 of 151 d) Replacement of Parts  Replace return spring in case of crack, kinks or permanent set.  Replace the brake cylinder body if found with deep marks, heavily corroded, or the bore is worn uneven or having ovality.  Replace all rubber parts.  If piston trunk is worn excessively it should be replaced.  Replace piston and piston rod for damages, bent etc.  Replace dome cover for damage, damaged hole etc. e) Inspection and Repairs of the Parts Examine visually that the internal surface is free from scratches, rust.  Brake cylinder bore to be checked for ovalness with proper gauge.  Check the characteristics of the return spring.  Piston trunk to be checked for wear and tear.  Pin, piston rod should be checked for wear.  Dome cover shall be checked for excessive wear and if worn build up with welding and thereafter re-bore to the required size.  Gauge bush bore of the piston rod, replace it if worn. f) Testing Of Brake Cylinder Body for Leakage Before assembly, put dummy plate on the dome side and subject the brake cylinder for hydraulic pressure of 10 kg/cm2 for 5 minutes. No leakage is permitted. g) Assembly of Brake Cylinder Assemble piston rod, pin, and piston trunk on piston, tighten CSK screws to piston trunk and piston.  Slide anti-rattler ring from the piston front side.  Assemble piston return spring on the piston head and insert the dome cover over the piston trunk.  Insert  12 x 25 mm long head pin into the hole provided in the extended portion of the trunk.  Smear the piston head & inside the cylinder body with MP 2 grease or equivalent.  Ease the packing into the cylinder with a wooden spatula with a round nose and round edge to avoid damage to the piston packing.  Push the piston assembly approximately to the central position of the cylinder.  With the help of special fixture, bring down the dome cover on to the cylinder body and fasten the 8 Hex. HD bolt, nut and spring washer with required torque.  Take out the  12x25 long pin from the piston trunk hole.  Fit back the plug at the rear of the cylinder.  Fit the new piston packing and wear ring. CHAPTER 7 – AIR BRAKE SYSTEM Page 17 of 151 B. TESTING OF BRAKE CYLINDER a) BRAKE CYLINDER TEST BENCH (Fig. 7.9) Test bench consists of the following main parts i. 3 nos. of isolating cocks ii. Isolating cock with 1mm choke iii. Pressure reducing valve Fig. 7.9 TEST BENCH FOR BRAKE CYLINDER iv. 2 Nos. Pressure gauges v. Pipe line filter vi. Brake cylinder pressure mounting base with safety guard vii. Air reservoir viii. b) TOOLS REQUIRED DURING TESTING i. Torque wrench range (2-3 kgM capacity) – One number. ii. Double ended spanner (M16) across face 24x27 – One number. iii. Socket wrench (M12) across face 19 – One Number. iv. Double ended spanner (M8) across face 13x14 – One number. v. Screw Driver – 300mm – One number. After the overhauling of the brake cylinder, it is mounted on the test bench and tested. It should be operated a few times on the test bench to ease the piston. Each brake cylinder after its maintenance and overhaul shall be subjected to the following tests on the test bench. Arrangement as shown in Fig. 7.9 is used for testing. WAGON MAINTENANCE MANUAL  Page 18 of 151 c) STRENGTH TEST Follow the procedure as given below. i. Place the brake cylinder on base (4) and connect the line to brake cylinder. Brake cylinder stroke should be free. ii. Close the safety guard, close the cock (Ic). iii. Open cock (1b) and let reservoir pressure reach 10 Kg/cm2. Check the pressure in MR gauge (3a). iv. Open cock (2) till the pressure reaches 6 Kg/cm2 in pressure gauge (3b). v. Close the cock (2) and wait for 2 minutes. vi. Open cock (1c). The above test should be done with the safety guard. d) PRESSURE TIGHTNESS TEST Follow the following procedure. Mount the cylinder on the test stand and tighten the mounting bolts & nuts. i. Set the brake cylinder stroke at 85 + 10 mm. ii. Open cock (2) and let the pressure gauge (3b) reaches 0.8 Kg/cm2. iii. Close the cock (2) and wait for 1 minute till the pressure stablise in gauge (3b). iv. Check for the pressure drop which should not be more than 0.1 Kg/cm2 in 10 minutes. v. Open cock (1 c) vi. Repeat the test at 130 + 10 mm piston stroke and 3.8 Kg/cm2pressure. Close cock (2) open cock (1c). Remove the brake cylinder. If pressure is not correct or leakage rate is higher, dismantle the brake cylinder and examine piston packing wear ring for proper fitment. Examine plug for leakage. Reassemble the components and retest. e) PAINTING The exterior of the brake cylinder shall be painted with black enamel paint. f) STORING Assembled or dismantled brake cylinder should be stored in such a way to prevent the following.  Flange surface should be prevented from damages.  Inlet and outlet port should be plugged with protective cap to prevent the entry of dust and moisture inside the brake cylinder. g) PRECAUTIONS DURING TESTING  Safety Guard should be used during the strength test.  Assembled or dismantled brake cylinder should be stored in such a way to prevent the following: i. Flange surface should be prevented from damage. CHAPTER 7 – AIR BRAKE SYSTEM Page 19 of 151 ii. Inlet port should be plugged with a protective cap to prevent the entry of dust and moisture inside the brake cylinder.  Avoid damage to piston packing by dull or sharp edged thin bladed tool.  Fit 12 dia, 25 mm long round headed pin on the hole provided in the extended portion of trunk surface before loosening the cover bolts.  Excessive lubrication of the cylinder must be avoided.  Specified tools and fixtures should be used for handling, mounting and removing the brake cylinder from the test bench.  The small metal parts like springs, washer, screws, nuts, bolts, washers should be kept in a safe place and replaced in case found defective. 709. DIRT COLLECTOR A. FUNCTION OF DIRT COLLECTOR Dirt Collector is placed in the brake pipe line at a point from where a branch is taken off to the distributor valve. As the name indicates the purpose of the dirt collector is to protect the distributor valve and the auxiliary reservoir by trapping dust and other foreign matters from the compressed air before it enters into the distributor valve and the auxiliary reservoir. This action is achieved by centrifugal action. Hence it is also known as centrifugal dirt collector. The dirt collector ensures inter vehicular full flow of dirt free compressed air to the auxiliary reservoir and the distributor valve through the branch pipes. When the air enters into the body of the dirt collector tangentially through port `A‟ it passes down through inverted case in a spiral path. Due to the velocity of air flow, dirt particles get flung outwards. There after they slide down & collect at the bottom. B. SALIENT FEATURES OF DIRT COLLECTOR The air entering into the dirt collector from the brakepipe is guided through suitably shaped passage in dirt collector body to produce centrifugal flow. The air is then filtered through additional filter assembly before it is passed to outlet on branch pipe side to provide dust proof air to the distributor valve /auxiliary reservoir after arresting fine dust particles. The dirt contained in the air descends down and gets deposited in the dirt chamber. However, fine particles are also arrested in the filter assembly. The dust particles accumulated in the dirt chamber are removed by opening the drain plug. Rubber gasket is provided between the cover and housing to prevent leakage. Similarly leather washer is provided between the housing and the drain plug to prevent leakage. Note: The dimensions and tolerance of dirt collector shall be as indicated in latest revision of RDSO drawing number WD-92051-S-03, WD-92051-S-04 and WD- 92051-S-05. The dirt collector is to be completely dismantled and overhauled once in 5 years or after 8 lakhs kilometers whichever is earlier or when there is some specific trouble. WAGON MAINTENANCE MANUAL  Page 20 of 151 C. TOOLS AND FIXTURES The following tools and fixtures are required for overhauling: a) Spanner 19 x 22mm b) Vice. c) Screw Driver D. PROCEDURE FOR MAINTENANCE I. Disassembly Hold the dirt collector in vice.  Loosen drain plug and remove it completely from housing.  Remove top cover and seal by loosening four hexagonal nuts and removing hexagonal bolts.  Remove filter from body. II. Cleaning of Parts  Clean all metallic parts using brush and kerosene oil.  Clean filter with soap water.  Check all parts for any damage. III. Replacement of Parts  Replace sealing ring and gasket.  Replace filter.  Check spring washer and replace in case defective or excessively corroded. IV. Assembly  Assemble body after smearing grease.  Locate filter in position and assemble top cover with new gasket.  Fix hexagonal bolts/nuts along with the spring washer.  Fix new sealing ring to the bottom and assemble drain plug. E. TESTING OF DIRT COLLECTOR Centrifugal Dirt Collector is provided at the junction of the main pipe and branch pipe in brake pipes. There are three purposes for providing the dirt collector. i. To ensure inter-vehicular full flow of brake pipe lines. ii. For branching and feeding to the distributor valve. iii. To remove dust and scale particles from the air prior to entering the distributor valve and the air reservoir. As Dirt collector is subjected to high air pressure it has to be tested for the leakage and strength. Testing of dirt collector is needed after its overhauling. There may be various causes due to which overhauling and subsequent testing of the dirt collector is required. CHAPTER 7 – AIR BRAKE SYSTEM Page 21 of 151 F. TOOLS AND EQUIPMENT  Test Bench (Fig. 7.10)  Compressor, capable of building air pressure up to 10 kg/sq. cm.  Double ended spanner (Across Face 19x22) – One No.  Dummy flange for dirt collector – 2 nos. G. TEST PROCEDURE Each dirt collector after overhauling and maintenance should be subjected to pressure test as below: i. Mount the dirt collector on base of the test bench. ii. Keep cocks ( 1f), (1c) and 1(e) closed. iii. Open cock (1a) and (1b). iv. Charge the reservoir (5) to 10 kg/cm2. v. Close two openings on the dirt collector using dummy flanges. vi. Open cock (1e), check the pressure at (6c). It should be equal to 10 kg/sq. cm. vii. If not develop pressure up to 10 kg/cm2 by adjusting pressure regulator(2). viii. Close cock ( 1e) ix. Check for leak over the body and joints with the help of soap solution, no leak is permitted. x. Also check for pressure drop in gauge 6(c)- for 3 minutes xi. Pressure in the gauge 6c should be maintained. xii. Reduce the pressure in the main reservoir (5) to 5 kg/cm2 by opening cock (1f) and adjusting the pressure regulator (2). xiii. Close cock (1f) as soon as pressure reaches upto 5 kg/cm2. xiv. Remove the dummy flange from the outlet port (which feeds to the distributor valve). xv. Check for free flow of air from the outlet port. (If air is not flowing freely it means that the filter is choked). xvi. The pressure will soon exhaust through the outlet port. xvii. Remove the dirt collector from the test stand. xviii. Report Results. H. SAFETY PRECAUTIONS a) The assembled dirt collector should be stored in such a way to prevent the following: b) Flange surface should be prevented from damage. c) Inlet and outlet port should be plugged with protective caps to prevent the entry of moisture and dirt inside the dirt collector. WAGON MAINTENANCE MANUAL  Page 22 of 151 d) Specified tools and fixtures should be used for handling, mounting and removing the dirt collector from the test bench. e) The small metal parts like screws, nuts, bolts, washers etc. should be kept in a safe place and replaced in case found defective, PRESSURE REGULATOR 5a MR PRESSURE. I.C. OIL SEPARATOR GAUGE I.C. AIR 1a 2 1b RESERVOIR 3 40 LITRE PR. GAUGE 4 5b BASE FOR AC I.C. 6 1c 1d 5c I.C. 2 PR. GAUGE 7 1e I.C. – ISOLATING COCK 1f I.C. I.C. BASE FOR IC/DC/CV/GVV Fig. 7.10 TEST BENCH FOR ANGLE COCK & DIRT COLLECTOR CHAPTER 7 – AIR BRAKE SYSTEM Page 23 of 151 710. AUXILIARY RESERVOIR A. FUNCTION Auxiliary reservoir is actually a pressure vessel and its function is to feed dry compressed air to the brake cylinder for application of brakes. B. SALIENT FEATURES The auxiliary reservoir is a cylindrical vessel made of sheet metal. On both the ends of the reservoir, flanges are provided for pipe connection. One end of the auxiliary reservoir is connected to the brake pipe through the distributor valve. Auxiliary reservoir is charged through the brake pipe. The auxiliary reservoir is charged to 5kg/cm2 pressure, charging from the brake pipe through Distributor valve. At the bottom of the auxiliary reservoir, drain plug (or drain cock) is provided for draining out the condensate/moisture. Note: The dimension & tolerances of the auxiliary reservoir shall be as indicated in latest revision of RDSO drawing WD-92051-S-01 for 100 lit. Capacity and RDSO drawing number WD-92051-S-02 for 75 lit. capacity. The auxiliary reservoir is to be completely dismantled and overhauled during POH or if there is some specific trouble. C. TOOLS AND EQUIPMENT a) Spanner A/F 19x22. b) Light hammer D. PROCEDURE FOR MAINTENANCE DISMANTLING  Unscrew the drain plug or drain cock.  Drain the water accumulated in the tank. CLEANING OF PARTS  Examine the outer surface for any pitting scales or rusting.  Clean the exterior of the auxiliary reservoir with a wire brush.  Pour kerosene oil in to the auxiliary reservoir and roll few times and drain the oil.  Dry the interior of the reservoir with a jet of air.  Rinse the reservoir with RUSTO-LINE and then with ESSO-RUST 392 or equivalent.  Clean the drain plug with a wire brush.  Auxiliary reservoir shall be painted on the exterior with two coats of zinc chromium primer and two coats of black enamel. REPLACEMENT OF PARTS  Replace the plug washer.  Replace the plug if threads are rusted or damaged.  Replace the reservoir having deep cuts on surface. WAGON MAINTENANCE MANUAL  Page 24 of 151 ASSEMBLY Assemble the drain plug with washer by screwing it back into its position. E. TESTING OF AUXILIARY RESERVOIR Air Pressure Test  Block one side passage of the auxiliary reservoir with dummy flange.  Admit air pressure from the other side passage at 10 Kg/cm2.  Check the leakage at the weld seams, with soap water solution.  No leakage is permitted. Hydraulic Test  With a hydraulic pump, apply a pressure of 16 Kg./cm2 from one flange end after blocking the opposite end.  Hold the pressure for 5 minutes.  Check for the leakage on the external surface of the reservoir by gently tapping on the weld seams with a light hammer.  No leakage is permitted.  Drain out the water completely and allow the reservoir to dry, by directing a jet of air. F. SAFETY PRECAUTIONS  Specified tools and fixtures should be used for assembly and dismantling operations.  Rubber / leather components should be stored in a safe place away from heat, alcohol & acids. All metal parts like washers should be kept in a safe place. 711. GUARD'S EMERGENCY BRAKE VALVE Guard's emergency brake valve is provided in the guard„s compartment. This valve provides a facility to the guard to initiate brake application in case of any emergency. Guard‟s emergency brake valve is connected to the brake pipe. This valve is actually placed in the guard‟s compartment so that in case of an emergency, the guard of the train can communicate to the driver of the train by operating the valve provided in the brake van. When the handle of the guard‟s emergency brake valve is placed parallel to the pipe, the air from the brake pipe is exhausted to the atmosphere. However, to restrict the excessive drop of air pressure in the brake pipe, a choke of 5mm is provided in this valve. This drop in pressure in the brake pipe can also be observed in the air flow meter provided in the locomotive cabin and finally the driver applies the brakes for stopping the train. The handle of the guard‟s emergency brake valve has to be reset manually to normal position before the brake pipe pressure is to be recharged. A. SALIENT FEATURES The guard‟s emergency brake valve consists of a housing in which a ball is housed. The ball has a through hole similar to the isolating cock. To the ball a handle is fixed at the top. By operating the handle the ball can be rotated along the vertical axis. When the hole in the ball gets aligned with the inlet and the exhaust port the compressed air can pass through the valve. However, for restricting the flow of air a CHAPTER 7 – AIR BRAKE SYSTEM Page 25 of 151 choke of 5 mm is fitted in the exhaust port for controlling the rate of BP exhaust. In order to have leak proof assembly two rubber seats are also provided in the guard‟s emergency brake valve Note: The general design and controlling dimension of guard‟s emergency valve shall conform to the latest revision of RDSO drawing no SK-73549. The guard's emergency brake valve should be completely dismantled and overhauled during POH or when there is some specific trouble. B. TOOLS AND FIXTURES FOR MAINTENANCE The following tools and fixtures are required for overhauling  Spanner A/F 19/22.  Special spanner for removing thread plug.  Spanner for removing gland.  Light hammer  Vice. C. PROCEDURE FOR MAINTENANC a) DISMANTLING  Hold the valve in the vice.  Unscrew the nut on the stem and remove the nut and the spring washer.  Remove the handle.  Unscrew the gland and pull out the stem from the body.  Remove the two gland packing on the stems.  Unscrew the threaded plug from the body using a special spanner.  Remove the „O‟ ring and the ball seat from the body.  Remove the ball and the second ball seat from the body. b) CLEANING OF PARTS  Direct a jet of air on the valve body to remove the dust & dirt.  Clean the external parts of the valve with wire brush.  All metal parts shall be washed with kerosene oil and wiped dry.  Rubber parts shall be washed with soap water solution.  Steel ball shall be handled carefully to avoid scratch marks or dent. c) REPLACEMENT OF PARTS  Replace all the rubber parts such as gland packing and „O‟ ring.  If spindle thread is corroded or damaged, the spindle shall be replaced with a new one.  If threads on the threaded plug are damaged or corroded badly, the plug shall be replaced with a new one.  If ball of the valve has dent or scratch marks it should be replaced with a new one. WAGON MAINTENANCE MANUAL  Page 26 of 151 d) ASSEMBLY  Place seat ring in its position in the bore of the body on one side.  Apply grease lightly on the ball.  Fit „O‟ rings on the spindle.  Insert the ball in the bore of the body in such a way that the ball sits on the seat ring and the groove seat for spindle is in top position.  Insert the spindle with „O‟ rings such that the spindle enters in to the groove.  Screw the gland in to the body.  Insert the second seat ring through the bore of the housing.  Fit „O‟ ring on the threaded plug. With a special tool screw the threaded plug.  Screw the threaded plug along with the „O‟ ring into the housing till the ball seat touches the ball.  The handle shall be put on the spindle and tightened with spring washer and nut. D. TESTING OF GUARD‟S EMERGENCY BRAKE VALVE  After overhauling, fix the valve to the test bench.  Put the handle of the valve in off position (close position).  Charge the inlet port with a pressure of 10Kg./cm2.  Check for leakage on the spindle portion and on the exhaust port with soap water solution.  No leakage is permitted.  Operate guard‟s emergency brake valve, by putting the handle in open position. Air should escape through the vent of the valve. E. QUICK COUPLING ARRANGEMENT For fitment of gauge an arrangement for quick coupling is provided. The figure shows the arrangement. The quick coupling when assembled with and without plug shall be leak-proof when tested upto 10 kg/cm2 air pressure. Details of part nos are as under; 1. Plug 8. Valve 2. Locking nut 9. Valve Seat 3. Locking Ring 10. Valve 4. Spring 11. Lower Body 5. Body Top 12. Spring 6. Locking Bush 13. Spring 7. Seal 14. Ball 3.5  CHAPTER 7 – AIR BRAKE SYSTEM Page 27 of 151 712. SLACK ADJUSTER A. SALIENT FEATURES Slack adjuster (also known as brake regulator) is a device provided in the brake rigging for automatic adjustment of clearance/slack between brake blocks and wheel. It is fitted into the brake rigging as a part of mechanical pull rod. The slack adjuster is double acting and rapid working i.e. it quickly adjusts too large or too small clearance to a predetermined value known as `A‟ dimension. The slack adjuster maintains this `A‟ dimension throughout its operation. The slack adjuster, type IRSA-600 & IRSA - 750 used on wagons is composed of the following parts  Adjuster spindle with screw thread of quick pitch (non self locking)  Traction unit containing adjuster nut, adjuster tube and adjuster ear etc.  Leader nut unit containing leader nut and barrel etc.  Control rod with head. The out standing features of slack adjuster IRSA-600 & IRSA - 750 are: (I) Fully Automatic Once initially set, no manual adjustment is further necessary at any time during its operation. (II) Double-Acting The brake shoe clearance is adjusted to its correct value both ways, either when it has become too large (owing to wear of the brake shoes and wheels) or when it has become too small (e.g. owing to renewal of `worn out brake blocks‟). (III) Rapid Working Correct brake shoe clearance is automatically restored after one or two applications of the brake. Verification If resistance occurs early in the brake application, caused by heavy brake rigging, e.g. an ice coating on the brake shoes, etc., in such cases the IRSA does not pay out slack immediately, but indexes the amount of slack to be paid out. If the slack really is too small, the IRSA will pay out this indexed slack at the next brake application. Thus false pay-out will not occur. True Slack Adjuster The slack adjuster adjusts incorrect slack only, thus giving the brake its best possible pre-adjusted limit of piston strokes, ensuring a smooth and efficient braking force at all times. Shock Resistant Train shocks will not cause false take-up or pay-out of slack. When brakes are released, the moving parts of the slack adjuster are securely locked. WAGON MAINTENANCE MANUAL  Page 28 of 151 Fig. 7.11 SLACK ADJUSTER CHAPTER 7 – AIR BRAKE SYSTEM Page 29 of 151 B. WORKING PRINCIPLE OF SLACK ADJUSTER In slack adjuster the ‟A‟ dimension is the controlling feature. `A` dimension is the distance measured between the control rod head and the barrel when the brakes are fully released. In other words „A‟ dimension corresponds to the correct slack when brakes are fully released. For wagons it defers wagon to wagon and „e‟ dimension which is the limit of length that adjuster will adjust is 555 – 575 mm other then higher axle load wagons („A‟ and „e‟ dimension should be maintained under all working conditions). For effective operation, slack adjuster has to operate under three different conditions, i.e. with:-  Correct slack  Too large slack  Too small slack. a) CORRECT SLACK If slack is correct then under normal released position, control rod head is at a distance „A „ from barrel end which corresponds to the correct slack (Refer fig. 1). For light brake application: During the first part of brake application, adjuster ear traverses distance `A‟. With correct slack, the brake shoes start applying against the wheel at the same time when control rod head touches the end of the barrel. (Refer fig. 2). Because of the braking action the left sleeve in traction sleeve is drawn against adjuster nut, against the force of barrel spring. This action compresses the clutch spring and clutch C is disengaged. For full brake application the brake is more heavily applied. During this action all parts of the brake rigging will be submitted to proportionate stress and will develop elasticity. As a result the ear end will travel an additional distance `e‟ corresponding to elasticity/full brake force (Refer Fig. 3). However the barrel is held back against the control rod head. Thus traction unit is drawn longitudinally through the barrel thereby compressing the barrel spring. Also it tries to take leader nut unit along in the movement. This action releases clutch B. The movement of adjuster spindle through leader nut causes leader nut to rotate on the spindle. For releasing the brakes (Refer Fig. 4)- When pressure in the brake cylinder decreases, the brake cylinder piston and the brake rigging moves back. The traction unit then moves to the left through barrel. As still the clutch spring is compressed the clutch C will remain in open position. The leader nut now gets locked by clutch B and will again begin to rotate on the thread. This time the rotation is in opposite direction, as spindle moves to left. However clutch B is not able to stop this rotation because entire barrel and barrel spring is free to rotate as long as clutch C is held open. Thus barrel and barrel spring rotate with leader nut and during this rotation, barrel spring extends and keeps the end of barrel in contact with control rod head. WAGON MAINTENANCE MANUAL  Page 30 of 151 Fig.1 Fig. 2 Fig. 3 Fig. 4 As long as clutch C is open adjuster nut is kept firmly locked in place on adjuster spindle. Any cycles of brake will cause a correspondingly idle rotation of leader nut unit back and forth on spindle thread. The idling of leader nut prevents all movements from influencing the adjustment. Thus adjustment is governed only by the amount of slack present in the brake rigging. For full brake release, the effective pressure in brake cylinder gets totally released. Also as braking stress disappears, clutch spring locks clutch C. As a result further rotation of barrel and leader nut gets stopped. If the slack is correct, the locking of clutch C takes place at the same moment as distance `e‟ is consumed. Adjuster nut is CHAPTER 7 – AIR BRAKE SYSTEM Page 31 of 151 then momentarily arrested and adjuster ear, adjuster tube and traction sleeve continues to move to left so that sleeve pushes against adjuster nut and locks it. Thereupon whole assembly moves to left until brake is fully released and distance A is restored. (Refer Fig. 1) Even in emergency application no adjustment takes place. The only difference is that the idle movement of leader nut back and forth will be somewhat longer. This is due to greater deflection of brake rigging under heavier stresses and longer piston travel. b) TOO LARGE SLACK In released position there is no difference from release position with correct slack (Refer Fig. 5). Now during first stage of brake application as the brake cylinder piston is pushed out the force is transmitted through the horizontal lever to pull the adjuster ear to the right until a distance „A‟ is traversed. At this point the end of the barrel touches control rod head. When this happens, barrel is arrested and also momentarily adjuster spindle with adjuster nut and leader nut is arrested. The left-hand seat in traction sleeve is then immediately drawn against adjuster nut thereby locking it in place on adjuster spindle (Refer fig. 6). For full brake application as slack is too large, brake shoes not yet contacted the wheel. Thus adjuster ear is drawn further to right to a distance `l‟ (Refer Fig. 7) pulling adjuster tube, traction sleeve, adjuster nut and adjuster spindle under compression of barrel spring against control rod head. Leader nut is being retained by spring and ball bearing in leader nut unit now starts rotating as adjuster spindle is drawn through it. When brake shoes starts contacting the wheels braking stress starts developing as a result clutch spring is compressed and clutch C is disengaged. For releasing the brake (Refer Fig. 8) take up action. When brake release starts there is an idle rotation of leader nut unit together with barrel and barrel spring in opposite direction as brake rigging moves back and braking stress decreases. As braking stress disappears and clutch C locks stopping further rotation of barrel and leader nut. The movement of adjuster spindle to the left stops. Adjuster ear, adjuster tube and traction sleeve continue to the left, adjuster nut is also being pushed along to the left by take up spring acting on ball bearing. This movement of adjuster nut to left over the spindle (under rotation on the spindle threads) continues until adjuster nut abuts the sleeve of spring in leader nut unit, which is held stationary by barrel. This permits the right hand seat of traction sleeve to engage adjuster nut and lock it in place on adjuster spindle. After this whole assembly moves as a unit to left. Barrel then moves away from control rod head until brake is fully released and distance A restored. Thus adjustment `l‟ that has taken place by adjuster nut is displaced on adjuster spindle, corresponds exactly to excess of slack that was present in brake rigging. WAGON MAINTENANCE MANUAL  Page 32 of 151 Fig. 5 Fig. 6 Fig. 7 Fig. 8 c) TOO SMALL SLACK For released position there is no difference from released position with correct slack. During first stage of brake application (all parts move together to right until) shoes touches the wheels. When this happens, end of barrel has not yet touched the control rod head. There is a distance „m‟ between end of barrel and control rod head corresponding to deficiency in slack. The left hand side of traction sleeve is drawn against adjuster nut locking it in place on adjuster spindle. (Refer fig. 9). CHAPTER 7 – AIR BRAKE SYSTEM Page 33 of 151 During full brake application, braking stress builds up and clutch spring is compressed there by clutch C is disengaged. The force of barrel spring now moves barrel, leader nut, barrel spring to the right to contact the control rod head. Due to this displacement the spring in leader nut unit is compressed and the distance `m‟ at the end of barrel is transferred to interior of leader nut unit (Refer Fig. 10). For releasing the brake after usual idle movement of leader nut back and forth, braking stress disappear and clutch spring lock the clutch C. The rotation of barrel and leader nut stops and adjuster spindle is held back momentarily, and right hand seat in traction sleeve engages adjuster nut. There upon the whole assembly moves to the left to a distance corresponding to still deficient slack, thus the end of barrel moves away only the distance A-m. The distance `m‟ is still indexed in leader nut unit (Refer Fig. 11). During next brake application (Refer Fig. 12) at first stage all parts move together to the right, until further movement of adjuster spindle is stopped by brake shoes contacting the wheel. The end of barrel then very nearly touches control rod head. Barrel is held back on adjuster spindle by the still locked clutch C. Now during second stage of brake application i.e. payout (Refer fig. 13) adjuster ear, adjuster tube and traction sleeve continue their movement to the right. Now the compressed pay out spring expands and pushes adjuster nut on adjuster spindle under rotation on ball bearing so as to follow receding movement of traction sleeve. When distance „m‟ is traversed, sleeve of spring in leader nut unit, stop in barrel, and pushing on adjuster nut is ceased. The left hand seat in traction sleeve engages and locks the nut and the brake action is continued. Thus the effective length of slack adjuster is increased exactly by distance `m‟ corresponding to the deficiency of slack. C. OVERHAULING OF SLACK ADJUSTER a) TOOLS & EQUIPMENT The following tools and fixture are required for overhauling of slack adjuster; (i) Jacking tool – for mass repair / overhauling of Slack Adjuster pneumatically operated fixture is used. (ii) Special Spanner (iii) Straight Nose plier (external) (spring type)18 mm to 25 mm- external (iv) Bend nose plier (internal) 25-30mm –internal (v) Screw driver (vi) Pipe vice & simple 6” vice (vii) Open end spanner 11-13 mm. (viii) Hand punches (ix) Kerosene oil bath (x) Air jet gun (xi) Slack Adjuster test bench WAGON MAINTENANCE MANUAL  Page 34 of 151 Fig. 9 Fig. 10 Fig. 11 Fig.12 Fig.13 b) PROCEDURE FOR MAINTENANCE The slack adjuster shall be overhauled at the time of POH of rolling stock.While dismantling or assembling it is essential to use special tools. Each component of slack adjuster shall be examined. Worn out part shall be checked according to the limits. For details, refer RDSO Technical pamphlet no. G-92 (September-98). CHAPTER 7 – AIR BRAKE SYSTEM Page 35 of 151 I. The minimum desired characteristic of each spring should be taken as under [Ref: RDSO Technical pamphlet No. G-92 (September - 98)]: Sr. Desc. Of spring Part Spring length Corrosp. Min. compressed permissible force No. No. 1. Barrel spring 21 475 mm 143 Kg. 2. Pay out spring 11 100 mm 58 Kg. 3. Take out spring 37 21.5 mm 22 Kg. 4. Clutch spring 39 38 mm 300 Kg. Any spring, which does not conform to the above characteristic, should not be used. In addition any of the springs is badly rusted or having compressed coil turns should not be used. II. The following parts must be replaced during POH of the slack adjuster [Ref: RDSO Technical pamphlet No. G-92 (September - 98)];  Spring dowel sleeve part No. (18)  Lock washer part No. (27)  Seal ring part No. (2)  Seal ring part No. (43)  Rubber gasket part No. (4)  Spring dowel sleeve part No. (25)  Dog pin part No. (6)  Tab washer part No. (34) D. LUBRICATION After cleaning and inspection all parts of slack adjuster should be coated with semi-fluid grease SERVOGEM-RR3 or BALMEROL multi grease LL3 before undertaking re-assembly. E. SAFETY PRECAUTIONS The following safety precautions should be observed during overhauling of slack adjuster. i. The place of overhauling must be clean and free from dust. ii. Ensure that no foreign matter/particle remain inside the sub-assemblies during re-assembly. iii. All rubber gasket, seal ring, washers must be replaced during overhaul. iv. Specified tools and fixtures to be used for disassembly and assembly operations. WAGON MAINTENANCE MANUAL  Page 36 of 151 F. TESTING OF SLACK ADJUSTER After overhauling, the testing of slack adjuster is carried out in a test rack (Fig. 7.11) for :- i) Take up test & ii) Pay out test a) Attach the adjuster ear to the free end of the cylinder lever of the test rack b) Screw the test rack spindle into the Slack Adjuster until the entire length of thread is covered by spindle sleeve and attach the free end of the spindle to the test rack. I. Take up or Pay-in test  Let down the control rod, so that the fork of the rod clasps the adjuster tube of the Slack Adjuster  Apply and release the brake a few times letting the slack adjuster take up until the correct piston stroke is obtained (until the indicator is within + 5 mm tolerance field of the scale). Note: The Slack Adjuster takes up 100 mm per braking. Dimension A1 will be 98 {+1} mm. {- 4} 2 Fig. 7.12 CHAPTER 7 – AIR BRAKE SYSTEM Page 37 of 151 II. Pay-out test  Turn up control rod and make two brake applications letting the slack adjuster pay out. Note : The slack adjuster pays out max. 30 mm per braking  Repeat the above pay in and pay-out tests a couple of times.  In case the slack adjuster does not accomplish the above mentioned tests satisfactorily, dismantle it and check that the parts are placed correctly.  The slack adjuster must then be tested once more in the test rack in accordance with the above instruction.  After the test is finished, remove the spindle from the slack adjuster.  Remove the slack adjuster from the test rack and unscrew adjuster ear 28. Give adjuster spindle 23 a final thorough inspection making sure that the threads are liberally greased, and screw it into the Slack Adjuster until its end protrudes from Adjuster tube 41. Put the safety collar 24 and secure it with the spring dowel sleeve. Make sure that the spring dowel sleeve pin fits tightly and that its ends do not protrude above the surface of the collar. Should there be any burrs on the collar, smooth off with a fine file and wipe clean. Then screw the adjuster spindle 23 back into the Slack Adjuster enough to make room for the adjuster ear 28. Slide control rod head 26 with control rod 44 on to adjuster tube 41. Place lock washer 27 on threaded portion of adjuster ear 28 and screw ear into threaded end of adjuster tube 41. Note : Hold adjuster tube firmly with a pipe wrench. Secure lock washer.27. Install the Slack Adjuster in the brake rigging. III. Testing of slack adjuster in brake rigging with hand brake In case a test rack is not available in the work shop, a test of function of the slack adjuster ought to be carried out after the slack adjuster is installed in the brake rigging and the correct piston stroke is obtained as follows:-  Place an iron object e.g. a hammer between the brake block and the wheel tread. Make two brake applications after the second application the correct piston stroke should be obtained.  Remove the iron object. Make two brake applications. After the first application the piston stroke is too long, but after the second application the correct piston stroke is recorded by the slack adjuster. G. PAINTING The slack adjuster is given a coat of anticorrosive paint, excluding the adjuster tube 41. Note : The unthreaded portion of the adjuster spindle 23 should not have a thick coating. H. PROCEDURE FOR BRAKE RIGGING SETTING AND MEASUREMENT OF “A” AND “e” DIMENSIONS The procedure to be adopted for operating brake rigging setting and measuring „A‟ and „e‟ dimension is listed below:- WAGON MAINTENANCE MANUAL  Page 38 of 151 (I) For „A‟ dimension (i) Ensure the air brake is in fully released condition and all the brake rigging gears are in proper condition. (ii) Apply brake three to four times to ease the rigging, by dropping and re- charging the air pressure in the brake pipe (iii) Ensure once again that brake rigging is in fully released condition. If „A‟ dimension is not correct (iv) Remove pin securing the control rod in U bracket. (v) Detach control rod and rotate it to adjust the gap between barrel end face & control rod head as specified in note above. Secure the control rod in U bracket. (vi) Apply brakes two to three times. (vii) Check the „A‟ dimension using the gauge. (viii) Recheck dimension „A‟ with brakes fully released after every brake release. (ix) Lock the control rod head firmly with check nut and tooth lock washer. (x) Secure pin with split pin. (II) For „e‟ dimension (i) If slack is in excess beyond the capacity of slack adjuster (`e' dimension 555 – 575 mm other then higher axle load wagon) there won't be any slack take up provision in the slack adjuster and slack adjuster will only act as strut/pull rod. This is because of brake shoes and wheel wear reaching their condemning limit/near condemning limit. In such cases the `e' dimension can be restored by adjusting link provided on the bogie frame head stock. (ii) Measure „e‟ dimension i.e. distance between protection tube end and mark on adjuster spindle using measuring stick after two or three brake application. It should be set to nearly to its maximum limit i.e. 555 – 575 mm other then higher axle load wagon. I. SAFETY PRECAUTIONS i. Always use wedge between wheel and rail before application and release operations for setting and measuring A and e dimension to prevent rolling of wagon ii. Ensure no part of the worker‟s body is in touch with moving brake rigging gears during application and releasing of brakes. iii. Do not touch or hold slack adjuster barrel while it is in motion. iv. Before setting any dimension ensure wear of brake shoe does not exceed to its minimum permissible worn limit (i.e. thickness of the shoe should not be less then 20mm). v. There won't be any slack take up provision in the slack adjuster and slack adjuster will only act as strut/pull rod. This is because of brake shoes and wheel wear reaching their condemning limit/near condemning limit. In such cases the `e' dimension can be restored by adjusting link provided on the bogie frame head stock. vi. Measure „e‟ dimension i.e. distance between protection tube end and mark on CHAPTER 7 – AIR BRAKE SYSTEM Page 39 of 151 adjuster spindle using measuring stick after two or three brake application. It should be set to nearly to its maximum limit i.e. 555 – 575 mm other then higher axle load wagon. 713. DISTRIBUTOR VALVE Distributor valve is the most important functional component of the air brake system and is also sometimes referred to as the heart of the air brake system. The function of the distributor valve is to distribute compressed air received from brake pipe to auxiliary reservoir and control reservoir. In addition to this it also senses drop and rise in brake pipe pressure for brake application and release respectively. It is connected to brake pipe through branch pipe. Various other components connected to the distributor valve are auxiliary reservoir, brake cylinders and control reservoir. MANUFACTURERS OF DISTRIBUTOR VALVE Two designs of distributor valves are in use on wagons. These are: i) C3W Type distributor valve ii) KE type distributor valve. Various companies presently manufacturing distributor valves are listed below: Type Manufacturers C3W Type Distributor Valve. 1. Greysham and Co. Delhi 2. Faiveley Transport India. Hosur 3. Stone India Ltd. Calcutta. 4. Greysham international Pvt. Ltd. Noida, U.P. KE Type Distributor Valve Escorts Ltd. Faridabad Knorr- Bremse Faridabad A decision has already been taken that new wagons manufactured henceforth will only be fitted either with C3W or KE type distributor valve. Hence the chapter covers description and maintenance of these two types of distributor valves only. 714. C3W DISTRIBUTOR VALVE The C3W Distributor Valve (Fig. 7.14) consists of the following main subassemblies: i. Main body ii. Quick Service valve iii. Main valve iv. Limiting device v. Double release valve vi. Auxiliary reservoir check valve vii. Cut off valve viii. Application choke ix. Release choke. WAGON MAINTENANCE MANUAL  Page 40 of 151 A. FUNCTION OF DISTRIBUTOR VALVE For application and release of brakes the brake pipe pressure has to be reduced and increased respectively with the help of driver's brake valve. During these operations the distributor valve mainly performs the following function. (i) Charges the air brake system to regime pressure during normal running condition. (ii) Helps in graduated brake application, when pressure in brake pipe is reduced in steps. (iii) Helps in graduated brake release, when pressure in brake pipe is increased in steps. (iv) Quickly propagates reduction of pressure in brake pipe throughout the length of the train by arranging additional air pressure reduction locally inside the distributor valve. (v) Limits maximum brake cylinder pressure for full service application/ emergency application. (vi) Controls the time for brake application and brake release depending on service conditions (vii) Facilitates complete discharge of air from the air brake system manually with the help of operating lever. (viii) Protects overcharging of control reservoir when the brake pipe pressure is quickly increased for releasing the brakes. B. WORKING OF C3W DISTRIBUTOR VALVE The distributor valve distributes the compressed air received from brake pipe to charge control reservoir through cut off valve and auxiliary reservoir through auxiliary reservoir check valve. After charging control reservoir and auxiliary reservoir, when brake pipe pressure is reduced by driver's brake valve, pressure differential acts across the large diaphragm of hollow stem assembly. As a result, the hollow stem gets lifted, opening the check valve of main valve. This action allows auxiliary reservoir pressure to enter into brake cylinder via limiting device for brake application. Main valve together with the limiting device limits brake cylinder pressure to rise to a maximum pressure of 3.8 + 0.1 Kg/cm2. As the brake cylinder pressure increases it starts acting on top of upper diaphragm of main valve. This results in downward movement of the main valve along with check valve till it reaches lap position. At this stage the check valve of main valve gets closed, stopping further rise of brake cylinder pressure. CHAPTER 7 – AIR BRAKE SYSTEM Page 41 of 151 Fig. 7.13 C3W DISTRIBUTOR VALVE WAGON MAINTENANCE MANUAL  Page 42 of 151 In this position, no further pressure can enter or exit from the brake cylinder. Every time brake pipe pressure is reduced gradually in steps, this phenomenon gets repeated thereby increasing the brake cylinder pressure finally to 3.8 + 0.1 Kg/cm2. For releasing the brakes, brake pipe pressure is increased by drivers brake valve and the hollow stem assembly of main valve is brought to normal position by neutralizing the pressure differential across main valve large diaphragm. At this stage hollow stem gives way at its top to exhaust the brake cylinder pressure to atmosphere. However, if brake pipe pressure cannot be increased then for releasing the brakes the pressure of control reservoir acting on large diaphragm of main valve has to be reduced. This can be achieved by tilting the release lever of double release valve. Tilting action opens the control reservoir release check valve thereby allowing control reservoir pressure to vent out & simultaneously hollow stem is pulled down which gives passage to brake cylinder pressure to exhaust to atmosphere resulting in brake release. C. DESCRIPTION OF VARIOUS COMPONENTS AND SUB-ASSEMBLIES (a) MAIN VALVE The main valve is housed in the main body. The various parts alongwith part numbers (as per manufacturer‟s catalogue) are shown in Fig. 7.14. Fig. 7.14 MAIN VALVE CHAPTER 7 – AIR BRAKE SYSTEM Page 43 of 151 Fig. 7.15 SECTIONAL VIEW OF MAIN VALVE The main valve consists of two diaphragms i.e. large and small. The top face of the large diaphragm, which is situated at the lower position of the stem assembly, is subjected to brake pipe pressure where as the bottom face is subjected to control reservoir pressure. The small diaphragm is situated at the upper position of the stem. The top face of small diaphragm is subjected to brake cylinder pressure and bottom face to atmosphere. At the top of hollow stem the check valve is situated which controls connection of auxiliary reservoir and brake cylinder. The main valve is also some times referred to as three pressure valve. Fig. 7.14 shows various parts of the main valve. The function of main valve is to supply requisite amount of pressure into the brake cylinder when BP pressure is reduced. Also it provides passage for brake cylinder pressure to exhaust to atmosphere, when brake pipe pressure is raised. (b) CUT OFF VALVE The cut off valve is housed in the main body and it consists of the following items:  Solex jet  Valve retainer.  Diaphragm.  Diaphragm follower.  Internal circlips.  Springs.  Pusher pin.  Jet valve assembly  Valve assembly  Diaphragm clamp  'O' rings.  Body  Guides etc. WAGON MAINTENANCE MANUAL  Page 44 of 151 Fig. 7.16 CUT OFF VALVE CHAPTER 7 – AIR BRAKE SYSTEM Page 45 of 151 The cut off valve has two diaphragms, upper and lower. The top face of lower diaphragm is subjected to control reservoir pressure and the bottom face to the brake pipe pressure. The bottom face of upper diaphragm is subjected to brake cylinder pressure, and the top face is subjected to atmosphere and compressed spring pressure. The cut off valve connects the brake pipe to control reservoir during charging and cuts off the connection with control reservoir when brake pipe pressure is dropped for application of brakes. This valve also provides a way to BP pressure from its chamber to auxiliary reservoir check valve. (c) AUXILIARY RESERVOIR CHECK VALVE The auxiliary reservoir check valve is housed in the main body. It consists of the following items.  Cap  Valve assembly  Spring  'O' ring Fig. 7.17 CHECK VALVE Auxiliary Reservoir Check Valve helps in charging the auxiliary reservoir. In addition to charging it also checks back flow of auxiliary reservoir pressure when brake pipe pressure is dropped for application of brakes. (d) QUICK SERVICE VALVE The quick service valve is housed in the main body and consists of the following items :  Diaphragm  Diaphragm clamp WAGON MAINTENANCE MANUAL  Page 46 of 151  Retainer  Seal Washer  'O' rings  Springs  Seal  Cup  Valve assembly  Internal circlip  Socket etc. Fig. 7.18 QUICK SERVICE VALVE CHAPTER 7 – AIR BRAKE SYSTEM Page 47 of 151 Fig. 7.19 SECTIONAL VIEW OF QUICK SERVICE VALVE The quick service valve has two diaphragms i.e. upper and lower. The top face of upper diaphragm is subjected to control reservoir pressure and bottom face to brake pipe pressure. Where as at lower diaphragm, the bottom face is subjected to brake pipe pressure when brakes are applied. The function of quick service valve is to create an initial pressure drop in brake pipe pressure by allowing a sudden entry of brake pipe pressure into the large volume bulb at the start of brake application. This ensures rapid propagation of pressure reduction in brake pipe through out the length of train. (e) LIMITING DEVICE The limiting device is housed in the main body and consists of the following items.  Diaphragm.  Diaphragm clamp.  Diaphragm follower.  Cap.  Valve retainer.  Inshot valve assembly.  Adjusting nut.  Check Nut.  Bush with cover.  „O‟ rings. WAGON MAINTENANCE MANUAL  Page 48 of 151 Fig. 7.20 LIMITING DEVICE CHAPTER 7 – AIR BRAKE SYSTEM Page 49 of 151 The limiting device has one diaphragm. The bottom face of the diaphragm is subjected to brake cylinder pressure during applied brake condition and top face is under pressure of compressed spring and atmosphere. The function of limiting device is to restrict the maximum brake cylinder pressure to 3.8 + 0.1 Kg/cm2 irrespective of the drop in brake pipe pressure or auxiliary reservoir pressure. (f) DOUBLE RELEASE VALVE The double release valve is housed in the bottom cover and it consists of the following items.  Tilt  Pin  Spring  Swivel Rod  Spring valve seat  Washer  Circlip  Cap  Split pin  Choke  Control reservoir release check valve  Auxiliary reservoir release check valve Fig. 7.21 DOUBLE RELEASE VALVE WAGON MAINTENANCE MANUAL  Page 50 of 151 The function of double release valve is to release the brakes manually when a single brief pull is given to the lever. However with a continuous pull to the release lever it also vents auxiliary reservoir pressure. D. DIFFERENT STAGES IN OPERATION OF C3W DISTRIBUTOR VALVE For effective functioning of the air brake system, the distributor valve has to operate effectively during : a) Charging stage b) Application stage and c) Release stage (a) CHARGING STAGE During charging stage the compressed air flows from the brake pipe and enters into the brake pipe chamber of the main valve, cut off valve and quick service valve. Due to this pressure the various valves get activated and perform as under. Main Valve: Due to brake pipe pressure act