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hyd over pressure


mrjpc130h
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You have no idea which pump is bad.

If you lower the gear or flaps the pressure may drop but it will return to the high pressure value once movement stops. You will also put the high pressure through all the "other" lines and fittings of the system you operate...

You cruise engine shutdown so you can "stop" the pump. If you turn the pump "off" you isolate it (pump) from the pressure relief valve that may be keeping the pressure under control. Then ALL the pressure will be inside you engine/drybay land may rutpure a line.

Before you CES your first engine inventory your engine conditions. Which one are you going to CES first? Can you start it back up? Have you any failures? SSC? Ign Control CB out?

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You have no idea which pump is bad.

If you lower the gear or flaps the pressure may drop but it will return to the high pressure value once movement stops. You will also put the high pressure through all the "other" lines and fittings of the system you operate...

You cruise engine shutdown so you can "stop" the pump. If you turn the pump "off" you isolate it (pump) from the pressure relief valve that may be keeping the pressure under control. Then ALL the pressure will be inside you engine/drybay land may rutpure a line.

Before you CES your first engine inventory your engine conditions. Which one are you going to CES first? Can you start it back up? Have you any failures? SSC? Ign Control CB out?

Thx... i agree wth u sir,any ideas how much pressure all other lines n fitting are design to stand max pressuer? Im come with ths ideas jst incase of the pressure jst above 3600psi for example by moving the flaps or gear we cn reduce pressure below 3500psi then we cn identifie the bad pump by switching off the edp switch.... and also if already identified one of the engine got prblem which is unable to be restarted mayb we cn consider ths way.....

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If I remember correctly the pressure relief valve starts to open at 3850 psi and then re-seats at 3100 psi. But that's from an old man's memory. Not sure what the max pressure the lines would hold but I sure as hell wouldn't want to find out in flight. A small leak or break in the line at that pressure would be like a laser cutting things in half, not considering the fact that it would be a highly flammable situation.

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If I remember correctly the pressure relief valve starts to open at 3850 psi and then re-seats at 3100 psi. But that's from an old man's memory. Not sure what the max pressure the lines would hold but I sure as hell wouldn't want to find out in flight. A small leak or break in the line at that pressure would be like a laser cutting things in half, not considering the fact that it would be a highly flammable situation.

George, you're not totally far off! The relief valve starts to open at 3450 and is full open by 3850 and you're right about 3100 psi when it resets. The book goes on to say that 3900psi can be seen but both the pump compensator and relief would've failed. The CES is in place just like NATOPS stated. If you would close the hydraulic valve switch associated with each engine you would run the risk of rupturing a line within the engine bay and creating more issues. Once again I don't have a clue on how much the lines could withstand more so each fitting, but the pressure lines are made of the stainless steel type. The catch to the CES is also like NATOPS stated. You would obviously make sure that the engine you shut down has no issues that would affect the restart in case you got the wrong engine at first. The common sense approach would be to shut down a inboard engine first if no issues are there to prevent a restart.

George, I might add not bad for a old man's memory!!

Dave

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  • 1 month later...

If I remember correctly the pressure relief valve starts to open at 3850 psi and then re-seats at 3100 psi. But that's from an old man's memory. Not sure what the max pressure the lines would hold but I sure as hell wouldn't want to find out in flight. A small leak or break in the line at that pressure would be like a laser cutting things in half, not considering the fact that it would be a highly flammable situation.

After sheet metal manufactures a line for us (hydro), we take it to our backshops and test it on the stand (under a very nice protective box of course). The book tell us to test it at twice the operating pressure - so approximately 6000 psi. This of course is not the max it can go, but it must pass that test in order to be installed on the aircraft. And yes... you don't want to be anywhere near a ruptured line when it happens - or any hydraulic component with that kind of pressure. Pin hole leaks are your most DANGEROUS to deal with and we always tell our troops to use a rag or absorbing material to check for leaks - not your hand :P This summer when I was deployed, we had a ramp actuator explode while taxiing and raising the ramp. It damaged several items in the fluids path and made an 8 inch hole in the actuator itself. It also soaked all the PAX baggage loaded on the ramp - I'm pretty sure TIDE won't get that stain out!

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After sheet metal manufactures a line for us (hydro), we take it to our backshops and test it on the stand (under a very nice protective box of course). The book tell us to test it at twice the operating pressure - so approximately 6000 psi. This of course is not the max it can go, but it must pass that test in order to be installed on the aircraft. And yes... you don't want to be anywhere near a ruptured line when it happens - or any hydraulic component with that kind of pressure. Pin hole leaks are your most DANGEROUS to deal with and we always tell our troops to use a rag or absorbing material to check for leaks - not your hand :P This summer when I was deployed, we had a ramp actuator explode while taxiing and raising the ramp. It damaged several items in the fluids path and made an 8 inch hole in the actuator itself. It also soaked all the PAX baggage loaded on the ramp - I'm pretty sure TIDE won't get that stain out!

Interesting info.

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  • 4 years later...

Hi! I have a different problem. My #2 EDP light won't light up when select OFF.   By its own it lights up.  But with #1 EDP it won't.  There's probably back pressure coming from #1. Bleeding done. Check valve replaced. Any suggestions?

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On ‎5‎/‎22‎/‎2016 at 3:09 PM, moe986 said:

Hi! I have a different problem. My #2 EDP light won't light up when select OFF.   By its own it lights up.  But with #1 EDP it won't.  There's probably back pressure coming from #1. Bleeding done. Check valve replaced. Any suggestions?

What year/model?

Snubbers can create this (if you are working H2-up) and it can be normal operations.

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  • 1 month later...
7 hours ago, agarrett said:

I was on the Design review board for the U model. Rockwell was going to up the hydro pressure to 4000psi which scared the crap out of us. They swore the factory said it would be OK. We finally talked them out of it.

They were going to up the system pressure of utility and booster to 4k?  to assist in running the guns, or what was their reasoning?  

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