engine bleed pressure

[sibinz]

hi,
after starup 737-900ER, when we put the bleed on for the engines, the right manifold pressure is showing less than that of the left,with the isolation valve in the auto position.Is it normal?

[sjap]

yes this could be normal, what is "less" ?
Is it within limits? What happens if you put the iso vlv in open?

See these limits:

http://www.sjap.nl/BleedcheckNG.xls

[sibinz]

Thank you so much Sir for your reply and thanks for the attachment you sent.

when we did the run at idle,the left duct pressure was around 20-25 , but the right duct pressure was showing around 10-15, with the isolation valve in Auto position.When we put the Isolation valve to open, the duct pressure indicator split was gone.
when we increased the throttle little bit, the right duct pressure was increasing.No fault light,nothing abnormal.

the AMM says a duct pressure at 10-25 psi is normal at engine at idle.Actually my doubt is that ,Is this duct pressure split is there for all 737?

[sjap]

It looks like thh RH bleed is a bit low.
I advise you to do the complete test and see how it behaves at high power settings.
If a little increase from idle is enough to get all pressures within limits? Then no worries. Else start T/S the RH bleed system first. I suggest to start with the HP controller.
But again, do the test with iso vlv closed to seperate the bleed systems, else T/S is not possible.

And yes a little split is normal, as long as the press is within limits. The bleed system consists of many parts on each side, and they act as a independant system on each side they are not always exact similar in pressure output.

[sibinz]

Thank you so much Sir..It really helps.

[cordesco]

FIM 36-10/804 step E. item(16)a states that:

When engines are in GROUND IDLE, no maintenance actions are required for pressure lower than 10 PSI if the pressures DURING FLIGHT are
normal.

See attached chart (.jpg file) where I had defined what's normal for pilots and mechanics knowledge in GOT/GOL.