[T-Cut]

Originally Posted by HarryM1BYT

I don't think the ITP pump type would generate anything like 52PSI, so why a pressure regulator there and are you suggesting that the regulator is actually in the tank?

You're right. The combined pump delivery pressure to the engine compartment is set to 36psi. The pressure regulator mentioned sits inside the so-called 'filter adapter' module located in the LHS tank port. Here's Rimmer's drawing (linked direct from the site)



This is Item 5. The pressure regulator is calibrated to 52psi, but remains shut under normal operation. Exactly what abnormal event would open that I've not figured out. I think Mike will know. I've amended the text to reflect the correct spressure.

If it is indeed there, between ITP and UBP - why there, surely it would have been more sensible to have a regulator after the UBP?

As above, it's function isn't yet clear.

The T, where the HP return flow goes back to the tank - I don't (think) a simple T piece would work to share the flow between the two venturi pumps would it, without some extra help to force it to share the flow?

The drawing is simplistic and as noted doesn't reflect the exact plumbing in the tank. The basic principle is all it illustrates.

When that ITP does fail, might a second UBP in the line from the tank, make up for the failed ITP? The UBP is perfectly capable of self priming I found, from bench testing one.

I guess it would probably work. Maybe somebody will try it.

Must admit I had not thought of venturi pumps to pump fuel from one side of the tank to the other. So I suppose due to the venturi pumps needing pressure to work, that the return system and cooler must be under some pressure?

The return line from the HP/Injector system via the cooler and into the scavenger system is under pressure otherwise it wouldn't work. I'm guessing that if volumetric flow to the engine is down (due to failing ITP) then the scavenging system will also fail. This explains the observed fuel levels in the tank when this happens.

TC