Valve installation effort begins – still on the timeline

by Chris Bergin

So far so good, as engineers move into the next phase of troubleshooting a cabin leak on Endeavour, which is still on the timeline to enable an on-time start to the STS-118 launch countdown Saturday evening.

A replacement Positive Pressure cabin Relief Valve (PPRV B) was successfully tested on Atlantis, before being removed for its three mile trip to Endeavour on Pad 39A. Installation of the valve in Endeavour has now been completed, ahead of schedule. Testing will begin Thursday evening. Update: First test success, new article to be published soon.

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The valve, located behind panels above the Waste Collection System (WCS), was deemed as the culprit of failed leak tests onboard the orbiter, which led to managers deciding that the valve required R&R (Removal and Replacing).

Checks on Atlantis’ PPRV B – which is being donated for her younger sister – were conducted overnight, with a leak check being carried out to ensure the part is in good shape for the switch of orbiters.

That process was completed this morning, despite a couple of testing issues with both PPRV A and B valves, after sources noted that PPRV A failed a reseat test and PPRV B had some problems during testing, although this is believed to be related to a problem with the GSE and not the valves.

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Meanwhile, on Endeavour, engineers removed the WCS to aid access to the panels which protect the two PPRV valves, ahead of work to be conducted this morning. Engineers also inspected PPRV B by borescope and didn’t note any visual inconsistencies.

To doublecheck the valve is causing the issue, United Space Alliance engineers connected Ground Support Equipment (GSE) directly to the valve, which did show that the valve poppet is leaking, confirming the earlier results that pointed to the valve as the culprit of failed leak tests.

Once the replacement valve has been installed into Endeavour, a reset will be conducted, ahead of further leak checks, which – providing they are successful – will allow NASA to pick up the launch countdown, on time, Saturday evening.

The only potential problem to this process at present is the weather, as a thunderstorm warning for the local area was produced Thursday morning. If KSC is alerted to lightning strikes, workers will have to leave the launch pad, delaying continued operations with very little time to spare.

So far, the weather has not affected operations, and the valve was successfully installed into Endeavour before noon – ahead of schedule.

Further updates will follow – refer to the live pages on L2 and STS-118 sections (forum).

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