Maintenance & Repair of LPG Pumps

1. Maintenance & Repair ofLPG Pumps • LGLD2E • LGLD3E

2. LGLD2E & LGLD3E • These pumps are used extensively in stationary bulk plant operations and on bobtails for delivery of LPG products.

3. Features • Replaceable casing liner and end discs protect the pump body from wear. • Built-in pressure relief valve protects the pump from excessive pressures. • Bearing lockcollars precisely position the rotor and shaft between the end discs to prevent end thrust wear. • Ductile iron construction provides thermal shock resistance.

4. CHARACTERISTICS OF LP GAS AND SYSTEM DESIGN Butane, propane and anhydrous ammonia are gases in their natural state; they are compressed into a liquid for transport and storage. When liquefied, propane and ammonia are always at their boiling point at normal temperatures, the slightest drop in pressure, or addition of heat, will cause them to boil and give off vapor or gas. This characteristic is critical when considering the transfer of liquefied gases from one tank to another. The MOST critical design area for ensuring optimum pump performance is the piping from the storage tank to the pump inlet.

5. CHARACTERISTICS OF LP GAS AND SYSTEM DESIGN As a general rule, a pressure gauge placed on the inlet of the pump should not drop more than 2 psi when the pump is started. If total restrictions to flow from storage tank to the pump inlet result in a pressure loss of more than 2 psi, then the result will be loss of capacity because of an increased amount of vapor entering the pump.

6. INSTALLATION GUIDELINES • Place the pump below the bottom level of the supply tank. • Place the pump as near to the supply tank as possible (ideally right below it). • Use inlet piping the next size diameter larger than the pump inlet. • Use the absolute minimum number of elbows, valves and connections possible … avoiding excessive restrictive fittings like globe valves. • Avoid loops in the piping, which allow pockets to accumulate.

7. INSTALLATION GUIDELINES cont. • Slope the piping from the lowest point at the pump inlet back upwards toward the supply tank so that vapor in pipes will draft back up toward the tank and not into the pump.. • Select an excess flow valve with minimal restriction characteristics. • Use an inlet strainer with minimal pressure drop. Locate it as far away from the pump inlet as possible. • Use a flexible connector away from the immediate areas of the pump suction port to minimize piping stress.

8. INSTALLATION GUIDELINES cont.2 • Use an external bypass valve in the discharge line, which returns flow back to the supply tank. • A vapor return line will allow the tank being emptied to maintain sufficient vapor pressure (to keep the liquefied gas in a liquid form), even when more than 2 1/2 percent of the tank’s volume is being removed each minute.

9. Repair Kits Available from Blackmer or an authorized Blackmer distributor. The kit contains repair parts most often needed to repair the LGL2E.

10. Repair Kits cont. It is a good idea to have at least one repair kit for each model size available at each plant to facilitate needed repairs.

11. Maintenance • Before work is started on a pump, it must be drained and the gas pressure relieved. • Tools necessary to repairpump.

12. Bearing Cover Removal • Remove the bearing cover and wipe off the excess grease. • The bearings are located by two piece locking collars that position the rotor in the casing (to prevent end thrust wear). It is necessary to remove the locknut and lockwasher from each end of the shaft before each head can be removed. • With a felt tip pen, mark the tang and lockout groove that was engaged, indicating where they were aligned to facilitate reassembly (if you are going to reuse the same lockcollar).

13. Locknut Removal Locate the lockwasher tang that is staked into one of the locknut slots. Using a small blade screwdriver and hammer, slightly tap the screwdriver to get it started under the tang.

14. Locknut Removal cont. Pry up the staked lockwasher tang.

15. Locknut Removal cont.2 Locate the small stake screwdriver into one of the locknut slots and tap it with hammer to loosen the locknut. Remove the locknut and washer

16. Removing the Head • Remove the head capscrews • Use two (2) large screwdrivers to pry the head loose from the casing.

17. Removing the Head cont. Slide the head assembly off the rotor/shaft and use care not to gouge the shaft or drop the bearing.

18. Removing the Head cont. The stationary seat of the seal and its O-ring will come off the shaft as part of the head assembly.

19. Removing the Seal To remove the stationary seat, remove the bearing and use a screwdriver to push the stationary seat out of its cavity. A slight tap with a hammer may be necessary to get it started.

20. Removing the Seal cont. The pump head resting on its bearing boss with the stationary seat and O-ring removed. It is a good idea at this point to check the shaft for any burrs or roughness that could cut the mechanical seal O-rings when removed. Use a piece of emery cloth to smooth down the shaft.

21. Removing the Seal cont.2 The rotating seal faces and seal jackets may require a light pry to disengage the jacket tangs from their rotor slots. Use two (2) small screwdrivers.

22. Removing the Seal cont.3 • Carefully remove the carbon rotating face. If it is mishandled or dropped, it will chip or break and cannot be reused. • Remove the seal jacket. • It is important to keep all parts of the seal clean if you are planning on reusing them.

23. Removing the Seal cont.4 Wipe the shaft and inspect for pits under the seal face O-ring which might act as leak paths.

24. Removing the End Disc Remove the end disc. Be careful not to scratch or gouge the shaft.

25. Removing the Vanes Slide out the three (3) uppermost vanes (that contact the liner) and inspect the edges of the vanes for gouges, ridges and tears. If the vanes are damaged, it is advisable to remove the rotor and inspect the liner for damage.

26. Removing the Rotor & Shaft To remove the rotor/shaft assembly, it is necessary to remove the opposite bearing cover and lockcollar. Use a felt tip pen to mark the tang and locknut groove (indicating where they were aligned to facilitate reassembly) if the parts are to be reused.

27. Removing the Rotor & Shaftcont. Hold the bottom vanes in the vane slot with your hand to prevent the push rods from jamming the rotor while it is being removed.

28. Removing the Rotor & Shaftcont.2 Rotor/shaft assembly, vane, and push rod removed. Note: the liner is positioned in the pump casing with a key which lines up with a keyway in both the liner and casing. The liner can, in most cases, be removed by simply sliding it out by hand.

29. Removing the Liner If the liner cannot be removed by hand, remove the opposite head and seal assembly. Using a piece of hard wood or a brass drift, and hammer, tap the liner around its outer edge to drive it out of the casing.

30. Removing the Liner cont. The liner and key removed. To remove the outboard head, repeat the same procedure as outlined for the inboard head.

31. Removing the Relief Valve Parts from the built-in safety relief valve removed. Remove and inspect the safety relief valve whenever the pump is repaired.

32. Disassembled Pump • The pump disassembled with all parts laid out. • The parts can now be inspected to determine what needs to be replaced.

33. Inspecting the Seals If a seal has been leaking, the entire seal should be replaced. Seal leakage will normally appear at the drain holes under the bearing housing on the pump head. However, if the leakage is coming between the pump heads and the casing, this type of leakage is caused by a damaged head O-ring and must be replaced.

34. Inspecting the Seals cont. • Should you replace a seal that has not been leaking? It depends on the condition of the parts. You may have damaged the seal when you took the pump apart, or it may have been in service long enough to have used most of its wear life. It may also depend on whether you have to reuse the seal as a temporary until you can get a new one.

35. Inspecting the Seals cont.2 • If either seal face is grooved scratched or marred, it should be replaced. • If the O-rings are cut, swollen, hardened or flattened, they should be replaced. • If you have the proper instruments, measure the lip on the carbon and if this lip is worn down within .010” of the shoulder, it should be replaced. • If in doubt, replace the entire seal.

36. Why do Seals Fail? • Forgetting to disengage the PTO: • Truck goes down the road with the pump running at high speeds and overheating occurs. • Result – damage to seal components. • Wrong lubrication: • Chemical reaction may cause O-ring deterioration. • Using a high pressure grease gun: • Grease forces through the bearings and into the seals may result in seal failure. • Running pump dry for extended periods: • Supply tank runs dry without anyone noticing. • Forgetting to open an inlet valve to the pump. • Result – excessive heat causes O-rings to leach (harden) and lose their sealing properties, and the seal gradually breaks down.

37. Why do Seals Fail? cont. • External shocks: • Pump or seal may have been dropped; chipping or breaking the carbon. • Abrasive particles: • Particles imbedded in the carbon causes well defined wear grooves in the stationary seat. • Cavitation: • Improper inlet conditions or recirculation through the pump’s safety valve causes the liquid to boil and form vapor, damaging the seals. • Re-using a deteriorated O-ring. • Cutting an O-ring during installation. • Rolling the O-ring (twisting it) onto the shaft. • Pinching an O-ring (partially flattening it).

38. Inspecting the Vanes • Replace vanes which show excessive or uneven wear: • Examine the leading edge. • Examine the ends. • Examine the backside. • Examine the wearplate area

39. Inspecting the Vanes cont. Vane wear and push rod penetrations are usually caused by excessive vapor entering the pump (called cavitation).

40. Inspecting the Vanes cont.2 • Cavitation and push rod penetration is a result of recirculation through the built-in relief valve on the pump, or improper inlet conditions. • Recirculation through the pumps’ built-in relief valve can be caused by: • Lack of separation bypass valve. • A malfunctioning bypass valve. • The bypass valve is set too high in relation to the pumps' built in relief valve.

41. Inspecting the Vanes cont.3 • Improper inlet conditions: • Inadequate pipe size. • Too long a line. • Too many elbows, tees, other fittings. • Dirty strainer. • Too small a strainer. • Too fine a screen mesh. • If the system lacks a strainer or has one that is too course, abrasive particles will enter the pump and damage the vanes and other parts as well.

42. Rotor and End Disc Examine discs and rotor for wear. A few scratches or a light abraded area should not affect pump performance. Remove any burrs form the edges of the rotor vane slots which could cause vanes to hang up.

43. Rotor and End Disc cont. Excessive wear on ends of rotor or disc after a short period of service is usually caused by end thrust on the shaft by the driver, or high inlet pressure and improper adjustment of the lock collars.

44. Rotor and End Disc cont.2 If the proper tools are available, check to see if the rotor has worn into the disc about .006” or more (about 3 thickness of paper). If so, the disc should be replaced. If the rotor is shorter than the liner by .014” or more, it should be replaced.

45. Ball Bearings • Ordinarily there will be very little wear or deterioration of ball bearings. • If a seal had been leaking extensively so the lubricant has been destroyed, bearings will wear rapidly. • Failure to properly lubricate the bearings at regular intervals will cause bearing failure. • Thoroughly clean the bearings in solvent. • Examine for extra play or clearance, indicating wear. • Spin the outer race and check for roughness of turning. • Look at each ball to detect pitting, rust or chipping of bearing plating.

46. Liners Small scratches made by particles dragged by the vanes seldom reduce pump efficiency. If deep grooves from abrasives are present, the liner should be replaced. If the liner is worn in a “washboard” fashion, which would cause the vanes to bounce, the liner should be replaced. The liner may possibly be repaired by sanding from side to side. However, it is advisable to replace it. Replacement liners and rotors are not included in repair kits, but are available from your distributor.

47. Relief Valve • An excessively worn valve can also result in low capacity, • A worn valve indicates lack of separates back-to-tank bypass, or one improperly adjusted (or sized). • Examine the relief valve. If its surface is shiny and worn, this is an indication that liquid has been recirculating through it, and the relief valve should be replaced.

48. Relief Valve cont. Liquid should not circulate through the valve at all, as this will cause excessive heat build-up and cavitation. To reassemble the valve cover to the pump body, it may be necessary to use two 1 ¼ “ long capscrews to draw the cover capscrews. The built-in spring loaded valve is meant to prevent damage to the pump or pumping system from excess pressure, and should not be used for recirculation.

49. Relief Valve cont.2 A separate bypass valve is required by Underwriter’s Laboratories, Inc. It should be piped from the pump discharge system back to the supply tank. The setting on the separate bypass valve should be at least 25 psi less than the 150 psi relief valve setting.

50. Relief Valve cont.3 Do not pipe the bypass valve back to the intake line. The valve and piping should be of adequate size to accommodate the full flow from the pump, when the discharge line is closed and the pump is running at its normal maximum speed.