Agilent Technologies

Agilent / HP 6890 GC Repair .... EPC [p/n G1531-60720 ] Module Disassembly, Repair, and Test

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• published: 22 Oct 2016
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This video documents the repair of a malfunctioning EPC [electronic pneumatics control] module for the FID of an Agilent/HP 6890 gas chromatograph [GC] . ...EPC p/n G1531-60720 The malfunction was the FID air flow could not maintain a desired set flow, and the maximum flow that could be achieved kept dropping. Instead of a flow of 450 mL./min, even a maximum flow of 380 mL/min could not be maintained AND error status was generated by the system. It was decided to take the malfunctioning EPC apart and try a cursory repair... a sort of "what do we have to lose?" One of the "enhancements" of the Agilent 6890 series GCs over the earlier 5890 series is the EPC [electronic pneumatics control] module. The EPC permits digital control of the GC gases as compared to the analog control of manually adjusting valves. This video demonstrates repairing the EPC controlling gases to the FID by replacing one of the 3 electro-mechanical valves in the detector EPC. Cost of the replacement valve was under $300 vs the greater than $3,000 cost for a replacement EPC. Preliminary failure hypothesis is briefly examined. Since the GC is almost 20 years old, it was decided not to try a mere "cleaning" of the malfunctioning valve. For us, the most reasonable and cost effective approach would be to replace the malfunctioning valve (and o-rings) and see what happens. Video Time ...... Video Segment Description 00:01 .... Introduction to the problem, replacement valve p/n G1531-60543 1:44 .... Beginning of disassembly of EPC 2:40 .... Using long needle-nose pliers to undo the Molex connectors for the EPC valves. Plastic on these connectors is almost 20 years old for our GC, and getting the Molex connectors to disengage can be tricky; don't be surprised if plastic tabs break. 3:32 ... Getting the PC board off the plastic supports 4:14 ... 3 valves in mounting assembly 5:05 ... Removing old valve ... locations of 5 o-rings to be replaced 5:23 .. Closeup of old o-rings ..fine particles on o-rings 7:07 ... Replaced 2 o-rings on valve side [wiped with 50% ethanol] ... replacement of 3 o-rings on output side not recorded 7:44 ... Comparing old valve with new valve prior to installation 9:21 ... New valve inserted ...PC board reattached ... valve Molex connectors re-inserted 11:45 ... Examination of Zero-Air Generator and addition of 90 micron and 40 micron filters in the output [supply to the GCs] flow tubing. 13:23 ... Filters installed and rationale... perhaps substrate for catalyst is deteriorating slightly ...unit is 20 years old. 15:01 ... Re-install into GC ... Remember: No electrical power to GC 18:06 ... How to remove GC lid 21:34 ... Adding 1/8" copper extensions to FID gas supply feeds 22:53 ... 4 gases re-attached ... GC can be powered on again 23:32 ... GC power on ... testing repair 24:31 ... Using bubble flow meter and smart phone 26:52 ... Re-positioning GC ... re-establish hot exhaust deflector .. split vents re-connected 28:26 ... Setting up for overnight stability "test" 29:30 ....Status after overnight test DISCLAIMER and some other legal stuff .... This video is for educational and documentation purposes only. Due to factors beyond the control of massspecguy, such as, for example, it would be impossible to know the specific future quality (or suitability) of materials, workmanship, and/or labor, I cannot guarantee against improper, unauthorized use, modifications, and/or mishandling of this information. Use of the information in this video is entirely at your own risk. Due to factors beyond the control of massspecguy, no information contained in this video shall create, give, issue, or grant any guarantee or warranty, either express or implied, of any particular result. Any injury, loss, or damage that may result from improper use of tools, methods, equipment, or procedures, or from any information contained in this video is the sole responsibility of the user and not massspecguy. Massspecguy and the creators of this video accept no responsibility nor liability for any actions, injury, loss, damage and/or consequences as a result of viewing this video. Use of the information in this video is entirely at your own risk.