Dionex GP50 Gradient Pump Issue-Please Help

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8 posts Page 1 of 1
Dear all,
I am trying to work with GP50 Dionex gradient pump (PEEK), please find the scenario as below:
1. There was a leak in outlet check valve housing of the left side pump head. So, I removed the housing and cartridges from the pump head and reinstalled it with new check valve.
2. No leaks were observed from the outlet check valve. Now, the leak happened in front of the pump head. So I replaced the piston seal as per the instructions given in GP 50 gradient pump Dionex manual.
3. After I reinstalled the pump head, no more leaks were observed. So I assume that the primary problem was due to the piston seal. But, now the pump is not priming properly.
The minute I open the priming valve, I get a beeping alert with a display message "High Pressure Limit Violation".
When I close the prime valve and try to run the solvent (DI water) through the column, it works just fine. Initially I observed the pressure to fluctuate between 30 to 1800 psi, after 5 mins it slowly settles down to around 1700 psi. Flow rate: 1mL/min.

I am not sure why I am receiving high pressure violation message specifically when I am trying to prime my system. I just got introduced to IC and I am not sure where I what went wrong. I did everything as per the manual and I double checked that I reinstalled all the parts correctly. The piston was cleaned with IPA before re-installation.

I am reaching out to get some help from this community, your suggestions and comments are much appreciated.

PS: I tried calling TF but then I was informed that they do not provide technical support to GP50 gradient pump issues anymore.

Thank you.
Hi akshpolae,

I have seen this a few times in the field. A small piece of the fine tip of your transducer knob has most likely broken off inside the transducer housing and that is causing the high pressure during priming. The fix is to order and replace the GP50 transducer housing (p/n 054052 - HSG,XDCR,PK,GP50/IP25).

You can see a schematic of the pump showing the transducer housing in section 5.4 of the GP50 operators manual available here:

http://tools.thermofisher.com/content/sfs/manuals/Man-031377-GP50-Gradient-Pump-Man031377-EN.pdf

If you don't wish to make the expense on this very old pump, you can still prime by disconnecting the PEEK tubing before it gets to the injection valve, keeping the transducer knob closed, setting a flow rate of 2-3 mL/min, and collecting the waste in a beaker. Just remember to set the flow rate back to your application flow rate when you're done so you don't damage the columns.
Best regards,

John Guajardo
Senior Product Manager
Thermo Fisher Scientific
Dear John,

Thank you for your suggestion. I have one more observation, when I prime the system with transducer's waste valve closed, it gives me a high pressure violation alert. But, when I prime the pump with the transducer's waster valve open it primes without any errors and I can see the solvent flowing out through the waste line.

Now, I am guessing that somewhere/somehow when I prime the pump with the waste valve closed, the flow still goes to column. I am not sure if my understanding is right. Please correct me if I am wrong. Also, do you still think I need to replace the transducer housing?

Thank & Regards,
Akshay
While I have not used that particular kit, I generally find that pumps have a waste valve that needs to be open for priming lest the rest of the system see excess pressure - the high pressure alarm for priming may well be set lower than the system's pressure tolerance for actual runs, which would explain the alarm despite low flow priming.
Thanks,
DR
Image
Hi Akshay,

If you are trying to prime via the prime button with the pressure transducer waste valve knob open and get a high pressure error message, it's very likely that the transducer knob tip has broken off inside the housing. (To be clear, the pressure transducer waste valve knob is located above the two pump heads.)
Best regards,

John Guajardo
Senior Product Manager
Thermo Fisher Scientific
Dear all,

Thank you for your suggestions. The violation had to do with the pressure limits set in the pump, I corrected it and the priming is working fine.

I have a minor issue with PQ, when I performed the flow rate test, I observed that the flow-rate was 50% less of what it was supposed to be. So, I checked left and right pressure on DSP status menu screen and found that one of the pump was not pumping solvent properly. So I dismantled the pump head, cleaned seals and cartridges and re-installed it. This solved the problem and both pump heads are working fine now. Also, pump is priming properly.

I performed the isocratic flow-rate test, all the 4 solvent lines meet the specification. When I started the dual channel flow-rate test (50:50), there is a continuous click sound that is triggered from the instrument. Somewhere from pump compartment. The dual channel flow-rates also meet the specification, but I am concerned about the click sound that is triggered. It is triggered for all the combinations of dual channel flows but it is not triggered for the isocratic flow. I checked to make sure that nothing is broken inside the pump head, prime or transducer compartment. I am guessing this should be from proportioning valve, please correct me if I am wrong. I am going to try to do 25:25:25:25 A:B:C:D lines just to see how this works. Please suggest me if you have any other recommendations.

Thanks and Regards,
Akshay
Hi Akshay,

Nice work resolving your priming issue. The clicking sound is from the proportioning valve and is normal.
Best regards,

John Guajardo
Senior Product Manager
Thermo Fisher Scientific
Dear John,

Thank you for your efforts and help. I appreciate it. Yes, it was the valve. I am glad that I was able to resolve all the issues.

Thanks & Regards,
Akshaya
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