Troubleshooting

Troubleshooting

Trouble Shooting Guide
Erratic Pressure \| Frequent Failure \| Failure to Prime \| Low Pressure \| Seal Life

The following trouble shooting guide has been prepared for the novice as well as experienced service technician. Often it is more expedient to simply replace old parts with new ones and get back to work, but for the chromatographer who doesn't have the budget for that, or who is down on a weekend with no spare parts, we hope these tips get your HPLC pump up and running, and keep it running.
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Problem

Cause

Remedy

Erratic Pressure

Dirty inlet valve	Remove inlet valve and flush with 50 mL of clean HPLC grade solvent.

Dirty outlet valve	Replace with new valve (an inlet cartridge can be substituted for an outlet if no outlet valves are available). If there is no filter on the outlet, then it may be cleaned in the same manner as an inlet.

Clogged solvent intake filter	Replace with new filter.

Leak at solvent inlet line	Tighten fitting. Replace ferrule and fitting if no longer serviceable.
*Note:* This problem may not be easy to detect! On the intake side of the pump there is a slight vacuum, so air will leak into the pump rather than solvent leaking out. There will be no visible sign of a leak. To detect this problem, make sure that there is no air in the intake lines, then open the outlet fitting and watch for air bubbles coming out (place a drop of solvent at the outlet fitting to observe air bubbles). If you continue to observe air bubbles after 60 seconds, then air is probably entering the head from the inlet fitting, a leaky pump seal, or an insufficiently tightened inlet housing.

Worn pump seal or piston	Replace seal. Inspect piston and replace if worn.
*Note:* If your piston is worn, you can sometimes get a Teflon seal to work for a short time, until a new piston can be obtained. Teflon will generally conform to and seal with a worn piston better than UHMW-PE, but not for long. Also, Teflon will generate copious amounts of wear material when used with a worn piston. Replace the worn piston ASAP.

Air in pump head	Erratic Pressure Purge pump for 30 seconds, then operate continued at 1,000 PSI or higher. The air will dissolve in the solvent and be expelled within about 30 minutes.
*Note:* This symptom is normal after replacing a pump seal or piston. Wet the seal and inside of the pump head with IPA to reduce the amount of time it takes to eliminate air from the head.

Not using degassed solvents	Degas, preferably using vacuum and sonication.

Air bubbles in inlet line	Degas solvent. Replace solvent inlet filter. Make sure solvent bottle still has solvent!

Frequent Check Valve Failure

Contaminated solvent	Use clean HPLC grade solvent.

No solvent inlet filter	Always use 10 micron or finer solvent filter.

Worn pump seal or Piston	Replace seal. Inspect piston and replace if worn.
*Note:* If the seal is badly worn, then the pump head will be contaminated with seal wear material. Remove the check valves and seal from head and sonicate the head in 20 % nitric acid for 30 minutes. Rinse thoroughly, then sonicate for 10 minutes in DI water. Wet seal and pump head with IPA prior to reassembly. The inlet valve should be flushed with 50 mL of HPLC grade IPA or Water, and the outlet valve filter inspected (if there is no filter on the outlet, then flush with 50 mL HPLC solvent).

Service life of check valves has been exceeded	Install new valves.

Failure to Prime

Excess back pressure in pump head	Open purge valve, or open fittings at outlet check valve.

Valve installed upside down	Verify that arrow faces up for both inlet and outlet pump.

Clogged solvent inlet filter	Clean or replace with new filter.

Clogged outlet valve filter	Replace outlet valve filter.
*Note:* The outlet valve filter should last at least 2 years in normal service. However, if piston seals are wearing out frequently, then wear material from the seal may cause premature clogging of the outlet frit, as well as contaminating the inlet valve. Replace the outlet filter, and inspect the sapphire piston for wear or score marks.

Operating Pressure is Lower than normal

Worn seal or piston	Replace seal. Inspect piston and replace if worn.

Air in pump head or intake line	Purge pump for 30 seconds, then operate at 1,000 PSI or higher. The air will dissolve in the solvent and be expelled within about 30 minutes.

Clogged solvent inlet filter	Clean or replace with new filter.

Dirty inlet valve	Remove inlet valve and flush with 50 mL of clean HPLC grade solvent.

Dirty outlet valve	Replace with new valve (an inlet cartridge can be substituted for an outlet if no outlet valves are available). If there is no filter on the outlet, then it may be cleaned in the same manner as an inlet.

Leaky fitting	Tighten fitting. Replace ferrule if badly deformed.
*Note:* If a slight amount of additional tightening does not slow stop the leak, then replace the ferrule. Over-tightening the fitting can damage the seat, strip the threads, or worse, cause the nut to shear off. Never exceed 15 in-lbs of torque.

Seal Life Unusually Short

Worn or scratched piston	Replace with new piston.
*Note:* It is not always obvious by visual inspection if a piston is worn or scratched. Use a magnifying glass to look for a glazed appearance, or axial grooves and scratches. The piston is badly worn if any such conditions are visible.

Build-up of salts on piston	Use the piston flush option if available. Always run DI water through the pump before shutting down for the day when running buffers.

Mobile phase incompatible with seal material	Use a Teflon seal.
*Note:* The UHMW-PE blend that is used by ASI is resistant to almost all HPLC solvents. However, there are a few solvents for which Teflon is more suitable. These are 100 % methylene cloride and 100 % toluene. Refer to catalog section on seals.

Trouble Shooting Guide