Pressure of inlet lower than setting point - EPC problem?

Question

Hi all,

I am using GC 7820 with split/splitless inlet to analyse liquid samples for a while. However, a problem has recently happened when the GC is running or I turn GC on.

- It shutdown when the temperature of oven is high when running.

or

- When I turn it on, sometimes the inlet pressure cant reach the setting point or increase slowly. In this case, I reduce the flow rate until the setting point of pressure is the same with actual value. After a while, I increase the flow rate with a small increment. By doing that, the pressure of inlet can reach the setting point of the method and the GC is ready for analysis.

I really don't know what is happening. However, I think that EPC module can fail and the inlet EPC valve does not open. Am I right?

Regards,

Long.

james_jenkins · Accepted Answer

This sounds like the inlet pressure and flow were off . If set point was 20 and actual is 1.2 , the inlet is either off or is in shutdown from an inability to maintain pressure. I would check for leaks, typical areas like septa, liner oring, column connection etc. GC enviornmental conditions for a 7820 are below. These are the operational conditions.

thanhlong · Answer

Hi James, After tightening the nuts between column and FID/inlet and also replacing the new septa, the pressure of inlet is stable and reach the setting point quickly. Thank your for your suggestion. Long.

james_jenkins · Answer

Hi thanhlong,

I updated the tags on your post for better visibility. What mode are you operating in with your inlet? It sounds like splitless and you may not have enough total flow supplying the inlet, or perhaps a leak. If you respond with your inlet parameters such as flow, mode etc, I may be able to get a better idea what is happening.

James

thanhlong · Answer

Hi James,

The mode I am using is split with ratio 30:1 and the temperature of inlet is 250oC. Actually, I haven't changed the pressure of supplier and GC has worked with the current supplier. This morning, that symptom happened again and after applying above way, it is running now and 2 samples were completely analysed.

Long.

james_jenkins · Answer

Working in constant flow? Possible this is a small leak at the septa or other connection. With a 30 to 1 split I don't see it being a total flow issue. If it happens again, post your method parameters so those can be ruled out. I hope it keeps working for you .

James

Pressure of inlet lower than setting point - EPC problem?

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