Troubleshooting Guide and Field Rep

Troubleshooting Guide and Field Repair
This section is for troubleshooting and repairing the Clark Pump in the field, utilizing the complete offshore kit. There are two offshore kits, one for 7% and 10% Clark Pumps and another for the 15% and 20% versions. If an offshore kit is not available, alternative repair instructions are includedlf the pump is functional, it is advisable to wait to reach a quiet port before attempting any field service. Please note: The center and valve blocks are constructed from engineered plastic and rely on O-rings for seal to the mating surfaces. Use caution not to scratch or damage the mating surfaces, as it may reduce the ability of the part to seal properly .
Recommended basic tools:
1/4” and 5/16” Allen wrenches End wrench set to 7/8”
Annular ring tool
Pliers
Vise
Strong angled dental pick with dulled tip and two small sharp dental picks Spanner, strap wrench or oil filter wrench for end cap retaining rings
Before dismantling the Clark Pump ,determine that there are no problems that exist in the rest of the system. Check the feed pump(s) for rated flow and pressure (see “Troubleshooting” in the owner’s manual and the technical bulletin)*
If a Clark Pump problem arises, it maybe in the form of low or asymmetrical pressure and flow readings, hard or asymmetrical shifting, high feed pressure readings, or a complete stall
Since there is a set of seals and check valves for each cylinder, a single failure mayffect only one cylinder. This will cause the pressures and flows to be different (asymmetrical) from one stroke to the other. Some asymmetry is normal and expected, as it is unlikely that the seals and parts match perfectly from side to side.
Common causes of low or asymmetrical pressure readings, in order of determination:
1. S.S. compression fittings leaking
2. Pressure relief valve leaking
3. Piston rod lip seal leaking
4. Annular ring damaged or cracked
5. Piston seals leaking
6. Check valves or piston poppet leaking
Shifting problem causes:
1. Worn or sticky valve spool seals
2. Worn spool piston seals
3. Worn or sticky pilot spool seals
4. Foreign material caught in a valve port
Stalling can be:
1. Pin seal failure
2 Excessive piston drag (tight pistons)
3. Broken valve spool
Much more complete troubleshooting and repair info is contained in our technical bulletins. Please consult them before proceeding.
1. Stainless Steel Compression Fitting Leaks
If a leak develops at a compression fitting, first try tightening the fitting. Use normal size wrenchs on the body and the nut and tighten hard If the leak persists, replace the tube assembly. If a pipe thread is leaking, remove the part, rewrap with Teflon tape and reinstall. Refer to the rebuild instructions for fitting pipe threads into plastic and meta l.
2. Pressure Relief Valve High Pessure Seal Leak
This will reduce pressure and product flow. Unscrew the valve and examine the rounded end. Check to see if there is any damage. If the damage is slight it can be dressed with 800 grit sandpaper. Dry out and inspect the bore to see if any foreign material is present. If there is excessive damage in the bore, the valve block will have to be replaced. If the plastic is milky and soft, sodium metabisulfite has been used for storage instead of the Spectra SG1 chemical and other major damage may have occurred.
3. Shaft Seal Leak
One seal leaking will cause asymmetrical product flow. This problenis easy to find. On the back side of the center block is a V4” pipe plug marked “TEST PORT”. This plugs an access port to the space between the two high pressure shaft seals. Remove the plug and run the system. If water squirts, sprays or runs out, the problem is a bad piston rod seal . One or two drops per minute is acceptable. Follow the rebuild instructions for cylinder removal and center block rebuild to replace the seals. If the system is shifting OK, leave the check valves and pilot valve in place.
4. Worn Spool Piston Seals
Worn spool piston seals will cause poor shifting. Remove the end blocks from the reversing valve. Using pliers, remove the white pistons from the end blocks. Examine the pistons for wear and plating of the orange O-ring material onto the surface. This plating can cause the pistons to be sticky and affect shifting. Carefully clean the orange deposits off of the pistons. Avoid scratching the plastic . Remove and replace the O-ring seals using the dull dental pick. Follow the rebuild instructions for reassembly .
5. Reversing Valve
A hissing sound from the valve block along with low or no product flow is an indicator of leaking spool seals or a cracked annular ring A bad spool seal will leak on every stroke. A cracked annular ring will leak on one stroke but may try to pressurize on the next. A spool that has come unthreaded will stall the system. A broken spool will allow the Clark Pump to stroke unpressurized, but will cause a system stall if the pressure relief valve is closed. Leave the valve on the unit and the hoses connected if possible. Follow the reversing valve disassembly in the rebuild instructions to remove and examine the spool. The two end sections thread into the middle. Check for tightness. The spool piston seals can also be checked at this time (see paragraph 4 in this section). Carefully look at the spool seal surfaces to see if they are damaged or worn. The contact area should look polished with minimal scratches, worn evenly, and should compress slightly when installed into the valve block. If foreign material has entered the system it will likely cause damage here. Small scratches across the surface are normal, but if any
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damage is detected or the spool is loose in the annular rings replace the seals. Compare to a new seal if possible. If no replacements are available, careful sanding of the seal surface is possible. Place 800-grit or finer sandpaper on a smooth, flat surface. Lay the complete spool assembly onto the paper, holding it in the center, then pull and rotate the spool along the paper with light pressure. Release and let it roll V8 of a turn and repeat. The paper scratches should run around the seal, not across. Done correctly, minor grooves and flat spots can be removed. If the seals are under size, heating them in hot water and stretching them may help them reseat. If the damage is too deep, the seals and the rubber quad rings underneath them must be replaced. A broken spool will come out in two or more pieces. See the “Technical Bulletins” for instructions on temporary repair of a broken valve spool. Current valve spools are one piece and ship with the seals in place. Earlier three piece spools can be disassembled for seal replacement. It is possible to change the seals on a one piece spool by cutting the old ones off with a razor knife and carefully sliding the new quad rings and seals into place.
6. Annular Ring Damage
The two annular rings inside the valve block are subject to wear and scratches if foreign material gets into the system Wipe away any water and carefully examine the rings with a flashlight. Look for excessive grooves or cracks in the seal contact area across the holes. A crack in a ring will not be visible when installed. If a crack is suspected see the “Reversing Valve Problems” technical bulletin for instructions on temporary repairs. Sanding with 80-grit or finer sandpaper can help clean up any small scratches. Sand along the holes, not across them. The surface must be smooth for proper valve function. If deep grooves are found, remove and replace the bad rings and spool seals following the rebuild instructions.
7. Annular Ring GRing Seal Leak
Since these are static seals around the outside of the ring, failure here is unlikely. A leak here could be caused by a defective O-ring, or from damage during installation. Check other possibilities before pulling the annular rings. Follow the rebuild instructions for the reversing valve.
8. Piston Seal Leak
At this point, the Clark Pump should be removed from its mounting, and a work area set up that can handle water spillage. Piston seal failure is unlikely because of the low working pressures. However, to inspect them, begin by removing the reversing valve assembly as a unit. Follow the rebuild instructions for cylinder and piston removal. The white pistons in 7% and 10% pumps have integral seals which should have a smooth contact area on the outer surface of the rounded lip. Some small scratching is OK. The piston sides may show deeper scratches, which is normal. Check the pistons carefully for embedded abrasive particles which could scratch the cylinders.
9. Piston Poppet (hollow glass piston rod units only)
The piston poppet is in one piston only. If a leak is suspected here, remove the clipring and inspect the underside of the poppet and the seat in the piston for foreign material or damage .
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10. Check Valve Leak
While the cylinders are off, inspect the intake check valves. The retainers and poppet are easily removed. Carefully check the poppets and seats (seats are in the center block). Replace a poppet and/or seat if any damage is found. When a cylinder is pressurizing, the intake check valve is closed (the one closest to the feed-in port) and the output check valve is open. Conversely, the other driving cylinder’s output check valve is closed. A leak in either one will cause poor performance in the suspect cylinder. If you find a problem in a seat and have an “Easy Out” for a 1/2” hole, remove the seat and repair or replace. If no replacements are available and the damage is slight, the poppet and seat can be “lapped” together using softened wet or dry 800-grit sandpaper in between.
11. Pilot Valve Pin Seal Leak
A leaking pin seal will cause asymmetrical pressures. Unless replacement pins and seals are available, it is not recommended to disassemble the pilot valve assembly without compressed air. Check the system by pu