goboeing
Posts: 2430
Joined: Mon Jun 05, 2000 5:31 am

Isolation Valves

Mon May 07, 2001 6:51 am

I was looking at a 767 checklist on a website last week and saw on it several different times, "left and right isolation valves......ck open". I don't know what they are and have never heard of them. Can anyone who does explain what they are, where they are, and what they do? Thanks to anyone who can explain.
Nick
 
Guest

RE: Isolation Valves

Mon May 07, 2001 6:55 am

Nothing more than a fancy name for a shut off valve. Isolate, to remove or sever all connection. I'm sure some knuckle head will come on here and tell you how to build one and many other facts you could care less about.  Smile
 
goboeing
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RE: Isolation Valves

Mon May 07, 2001 7:05 am

Thanks for the quick response. Knucklehead is still welcome to recite a manual definition though...
Nick
 
JETPILOT
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RE: Isolation Valves

Mon May 07, 2001 7:32 am

I'm not so sure that an isolation valve by defenition means a shutoff valve, but has it's name associated with "isolating" the left and right pneumatic manifilds creating two isolated pneumatic systems working independant of each other.

A duct failure on either side of the pneumatic system would mean complete pneumatic system failure unless you had some way of sealing off the pressure leak on the damadged system.

Normally the system runs "isolated", but in case of an engine failure the left or right system can operate both systems pneumatic demands.

Thats it's function on the 727 anyway.

JET
 
windshear
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Pneumatic Distribution

Mon May 07, 2001 8:04 am

Well Isln. valves has something to do with the air distribution, through the aircraft using a series of interconnected ducts. Normally the left and right distribution ducts are "isolated" so that air from each engine is supplied to it's on-side equipment only. However, though the use of isolation valves, bleed air can be used from any one source to supply the entire system. Additionally, the isolation valves are normally open on the ground so that the APU can supply air to the entire system and for engine starts.

The flow lines drawn on the pneumatic panel can help the pilot visualize the flow of air in the system. The left and right isolation valves are normally closed after engine start so that the left and right systems operate isolated.
These isolation valves must be open to supply air for engine starts. The center isolation valve is always left open and is only closed by abnormal procedure.

The air driven hydraulic pump recieves air for operation through the center duct. If the center isolation duct is closed and the APU is not supplying bleed air, the center hydraulic demand pump will not operate

Pneumatic duct pressure can be monitored using the duct pressure gauge or display on the pneumatic panel. Each ducts has a pressure needle that registers duct pressure downstream from the isolation valves.

I hope I didn't confuse or "bore" you, but that's the most detailed image I can give you for as this moment...
Where did you find the check list?!!

hope it did some good this report on isln.valves Smile/happy/getting dizzy
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
chdmcmanus
Posts: 372
Joined: Wed Mar 21, 2001 12:53 am

RE: Isolation Valves

Mon May 07, 2001 9:01 am

Jetpilot and Windshear both gave good discriptions. Iso valves also exist in the fuel and hydraulic systems, depending on acft mfgr. The definition would be the same.

Regards, ChD
"Never trust a clean Crew Chief"
 
EssentialPowr
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Joined: Wed Sep 06, 2000 10:30 pm

RE: Isolation Valves

Wed May 09, 2001 2:10 am

Windshear,

What a/c are you describing?
 
windshear
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Joined: Tue Mar 14, 2000 4:45 pm

RE: Isolation Valves

Wed May 09, 2001 8:45 pm

The one I was refrerring to is the 767...
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
EssentialPowr
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RE: Isolation Valves

Thu May 10, 2001 1:25 am

Other than engine driven hydraulic pumps, how many other hydraulic pumps does a 767 have? Is it the same config as a 757?
 
windshear
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RE: Essentialpowr

Mon May 14, 2001 7:55 am

You asked about the hydraulic pumps on the 767, if they only have engine driven pumps or other...

For starters I have to say that I can not comment anytthing beloning to the 757, but in considderation that it's the little sis to the 767, then maybe they have simalaritys in some of the circuits, but I can't promise or say for sure...

In fact the 767 has to different systems the L/R Hydraulic sustem and the Center hydraulic system, the L/R systems are identical but not the same as the center system.
Basically you can briefly say that the hydraulic system on the 767 is broken down into three separate systems: Left, Center and right. Each system has multiple pumps that are each driven by separate power sources. The system is designed so that a loss of 1 or 2 systems still permits limited operation of basic flight controls and other systems in a limited capacity. There is also a RAM Air Turbine (RAT) that can be deployed automatically or manually to power critical flight controls in the event of a complete hydraulic system failure.

The left and right hydraulic sytems have identical pump configurations. They both consist of "TWO" pumps: An engine driven primary pump and an electrically driven demand pump. Either pump can supply the necessary pressure to satisfy the demands of it's hydraulic components

The Center hydraulic sustem has three separate pumps controlled by two separate power sources. There are two electrically driven primary pumps and one air driven demand pump (ADP). The ADP is capable of providing normal system demands if both electrical primary pumps fail. The ADP also provides supplemental hydraulic power to the center system during operation of high demand items such as flaps and gear.
The ADP is powered using bleed air from the center pneumatic duct.

The Ram Air Turbine (RAT) is an emergency system that can be used to power primary flight controls in the event of dual engine failure or total hydraulic power loss. The RAT is basically a propeller that when deployed drops into the air stream and creates hydraulic pressure. A minimum airspeed of 130 Knots is required for satisfactory RAT operation.

I hope that it answered your question because there are many more systems or functions to the hydraulic system than just one or two different pumps.

A thing I forgot to mention about isolation valves is that they also excist (though serve other purposes) in the brake system, Aircond. and fuel system if you want to know more just ask:O)

wow I'm beat well hope to hear from you...
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
windshear
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EssentialPowr Please Response

Tue May 15, 2001 6:03 pm

I would love if you would write back, just to let me know if you read my reply, and if it helped...
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
JT-8D
Posts: 423
Joined: Sun Dec 31, 2000 11:34 pm

RE: Isolation Valves

Wed May 16, 2001 7:36 am

757 has one engine driven pump, and one elec pump for left system. There are two elec pumps for the center system, but only one may be turned on if the engine gen is not powering the busses. Right system, same as the left. There is also a hmg, or hyd motor generator, and the rat. Im not sure, but I believe the rat pressurizes the left system, and the hmg runs off the rt. Dont quote me though, school was a while back..JT
 
goboeing
Posts: 2430
Joined: Mon Jun 05, 2000 5:31 am

The Checklist

Thu May 17, 2001 5:29 am

Someone a while back asked where the checklist was from and I tried to send the link but my computer froze in the process. Anyway, it was http://www.smilinjack.com which I saw in a post a couple weeks ago by DC-9CAPT. Thanks for the info. I understand what they are now.
Nick
 
windshear
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Joined: Tue Mar 14, 2000 4:45 pm

RE: Isolation Valves

Thu May 17, 2001 5:49 pm

Thanx for the link, I asked about the ckecklist.
There is a lot of things misiing, buit still very good:O)

Still the Wilco 767 is almost complete in cockpitt preperations a very good product indeed:O)
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
goboeing
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Joined: Mon Jun 05, 2000 5:31 am

Windshear

Fri May 18, 2001 5:48 am

Is there a link for "Wilco 767" that you just mentioned? If so, I'd like to see it if you have it.
Nick

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