How to Troubleshoot Low Pressure or No Flow/Solvent Coming Out of 1100/1200 Series Isocratic/Quaternary/Binary Pumps

Answer

This Information Applies To: Agilent 1100/1200 Series G1310A Isocratic Pump, G1311A Quaternary Pump, and G1312A/B Binary Pump modules

Issue

This article shows different options to troubleshoot low pressure or no flow issues in 1100/1200 series Isocratic/Quaternary/Binary pumps. 

Items Required

• Open-end wrench 14 mm (p/n 8710–1924)
• Open-end wrench 1/4 - 5/16 inch (p/n 8710–0510)
• Pair of Tweezers

Steps to follow

The following steps will guide you to find out which part is causing a solvent flow or pressure problem.

Figure 1, Figure 2, and Figure 3 show the hydraulic paths of the pumps.

Figure 1. Hydraulic path of G1310A Isocratic Pump.
1. Damper, 2. Purge Valve, 3. Outlet Ball Valve (OBV), 4. Pump Head, 5. Active Inlet Valve (AIV)

Figure 2. Hydraulic path of G1311A Quaternary Pump.
1. Degasser, 2. Multichannel Gradient Valve (MCGV), 3. AIV, 4. OBV, 5. Damper, 6. To sampling unit and column, 7. To waste

Figure 3. Hydraulic path of G1312A/B Binary Pumps.
1. AIV (Pump head A), 2. OBV (Pump head A), 3. AIV (Pump head B), 4. OBV (Pump head B), 5. Mixing Chamber, 6. Pressure Sensor, 7. Damper, 8. Mixer, 9. Purge Valve

When you observe that your pump cannot draw solvent from some or all solvent lines, the most common reasons for this problem are:

• Large leak in pump head.
• Large leak or total blockage inside the degasser (degasser chambers).
• Total blockage of the solvent bottle inlet filters (p/n 5041–2168).
• Blocked or stuck Outlet Valve (OBV) (p/n G1312-60067) and/or Active Inlet Valve Cartridge (AIV) (p/n 5062–8562 for G1310A/G1311A/G1312A or p/n G1312-60020 for G1312B)
• Blockage within the Multichannel Gradient Valve (MCGV) of the Quaternary Pump module (G1311A).

Warning: Put on suitable gloves and other PPE for the solvents contained in your LC solvent bottles before starting this procedure. Opening fittings while the solvent filters are submerged in solvent will lead to solvents leaks due to hydrostatic pressure. Ensure that enough lab wipes or other absorbent material is used to soak up any spills. Dispose of lab waste appropriately.

1. Do you see the physical leak from the pump or the degasser? 

- If no: go to step 2

- If yes: You may need to observe which parts are damaged, and need to be replaced, by following these steps or contacting your local Agilent support representative.

• Leaking from the gap between the two pump head halves indicates that the piston seals (and wash seals if installed) need to be replaced. See the following article for detailed instructions replacing the piston seals: How to change seals in a 1260 Infinity Binary, Quaternary, or Isocratic Pump without Seal Wash Option. The steps to change these parts are the same as 1260 Infinity pump modules but 1100 and 1200 modules do not require the use of a torque wrench for re-assembly.
• Leaking from the AIV body (p/n G1312-60025) or OBV (p/n G1312-60067). If after trying to retight these valves the leak continues, it may indicate that replacement is required. See How to Change the Active Inlet Valve (AIV) and cartridge on a 1260 Isocratic, Binary or Quaternary Pump and How to Change the Outlet Valve on a 1260 Isocratic or Quaternary Pump. Torque wrench is not required for installation of valves on 1100/1200 series pumps.
• Leaking from the purge valve. Replace the seal cap (p/n 5067–4728) to prevent leaks from between the purge valve and front of pump head. If you notice an internal purge valve leak, i.e. you notice that after closing the purge valve there is still some solvent moving into the waste tube, then the purge valve should be replaced. For further details on purge valve maintenance, see How to Replace the PTFE Frit of the Purge Valve in LC Pumps.
• Leaking from the Degasser. In this case, please contact your local Agilent support representative.

2. Put on gloves and cover the pump leak sensor/tray with paper towels to soak up any spills. Then disconnect the solvent line going into to the AIV body at the bottom of the pump head (red box in Figure 4). 

Figure 4. AIV Fitting.

Does solvent drip freely from the AIV fitting?

- If no: Lift the solvent filters (red box in Figure 5) above the solvent level in the bottle to visibly check the undersides of the solvent filters are in good condition and not blocked. If unblocked, the solvent should freely drip out of the other end of the solvent tube (hydrostatic pressure). If it is partly blocked, then very little solvent will drip out of the solvent tube, and in this case you should replace the solvent filter and go to Step 4.

You can also use gloves and temporarily remove the solvent filter to see if it is causing the no flow issue in that channel. After troubleshooting has been completed, new, or cleaned solvent filters must be installed before further use or to continue troubleshooting the no flow issue.

Figure 5. Bottle-Head Assembly Parts.

If there is still no free dripping from the solvent line, then go to Step 3.

- If yes: go to Step 4.

3. As mentioned previously, the Quaternary Pump has an MCGV that may have a blockage that limits your pump flow. To further identify this problem, you need to bypass the MCGV.

To bypass it, connect a solvent bottle of HPLC-grade IPA (with a clean solvent filter) directly to the AIV (red box in Figure 4).

4. Open the purge valve and purge the pump (5 mL/min).

Can the pump now draw solvent and pump it out the waste line of the purge valve?

- If no, the MCGV may not be the root cause of this problem, go to step 5.

- If yes, The MCGV has a blockage limiting your pump flow. To clean the MCGV, see the article Troubleshooting Unstable Retention Time Issues - Cleaning the Multichannel Gradient Valve (MCGV) on Agilent Quaternary Pump Modules. If the cleaning does not solve the issue, contact your local Agilent support representative.

5. Loosen the capillary coming off the top of the OBV (red box in Figure 6).

Figure 6. OBV Fitting.
1. Valve Capillary, 2. OBV

Briefly start the pump flow again. Do you see any air bubbles or solvent coming out of the top of the OBV?

If no: remove the OBV and go to Step 6.

If yes: wait to see if you get a steady flow of solvent, then stop the pump flow. Retighten the valve capillary to the OBV and restart the pump to see if there is pressure and flow. If you retighten the valve capillary, but the pressure is still reading zero or less than the setpoint, it may indicate that the blockage in the capillary from the outlet valve to the pressure damper or pressure damper itself. Contact your local Agilent support representative for further assistance.

6. Do you see liquid filling up the well where the OBV was removed from?

If No: the AIV cartridge is likely to be the issue. The AIV cartridge only (not the AIV body, Figure 7) can be sonicated in warm water, methanol, or IPA (HPLC grade).

Caution: Only sonicate the AIV cartridge if sonication of an AIV is required. Do not sonicate the body of the AIV as it will damage the electrical components of the valve.

Figure 7. Active Inlet Valve (AIV).
1. AIV body, 2. AIV Cartridge

If yes: The OBV is the issue, sonicate the OBV in warm water, methanol, or IPA (HPLC grade) as it may be sticking. See the article How to Sonicate the Inlet and Outlet Valves of Agilent 1100, 1200 and 1260 Series Pump Heads.

7. Re-attach and tighten the valves on the pump head, reconnect capillaries, and purge the pump again.

8. If the pump is still having issues, then it is time to replace the inlet and/or outlet valves as determined in the preceding troubleshooting steps. Contact your local Agilent service representative for further assistance.

9. Close the purge valve and make sure that the pump reaches pressure and is stable.

Tips: It is recommended to have replacement parts on hand to fix the pump issue. If sonicating the valve fixes the issue it is likely to stick again, so users should prepare to replace the valve soon.

Learn how to effectively troubleshoot your Agilent LC Pump: HPLC-0GEN-2201e - Chromatographic Troubleshooting for HPLC e-learning course available from Agilent Education.