Pressure testing gone bad

For those of you lucky / affluent enough to afford a pressurized
aircraft, here is the way NOT to test yours:

http://disastercity.com/kc135/

Mark Hickey

Mark Hickey wrote in message . ..
For those of you lucky / affluent enough to afford a pressurized
aircraft, here is the way NOT to test yours:

http://disastercity.com/kc135/


This is why whenever possible pressure testing should be
done with water, rather than air. Not an option in this
instance.

A former cow-orker of mine used to work for Cleveland Pneumatic
Tools which, in addition to aircraft landing gear, made these
big whatchamacallems, pressure chambers like deep sea divers
might sit in for a few hours to prevent the bends. Anyhow,
he saw one fail hydro testing one time. Said it looked like
a small tsunami as the water swept accross the shop. Had they
tested it with air it might have killed everyone in the room.

Back in another life when I was a contract engineer for a company
that made radiation monitoring equipment our QA technician was
hydrotesting a 'volume' for one of my jobs and I stopped
by to see how it was going, and also to be sure he didn't
have the radiation detector inside when he filled it with
water. He told me that he must have trapped an air bubble
in the volume because it took many strokes of the pump to get
the volume up to the correct pressure (225 psi
IIRC). I stepped back a couple of feet and explained to him
some of the differences between compressible fluids like air
and incompressible fluids like water. Then I pointed out that
1) if the volume he was testing failed the test badly it just
might explode, and 2) the air bubble reduced the sensitivity of
the test rendering the result invalid anyhow.

He was unimpressed and I went back up to my office. Later that
day another engineer told me what he saw happen next. The
technician had installed a short piece of tubing and a ball
valve to be used to drain the volume. The end of the valve
pointed straight out horizontally from the volume. So when
the time was up he went and got a bucket, held the bucket
under the end of the valve expecting to catch the water as
it dribbled out, and opened the valve. The water shot
accross the room hitting an oscilliscope on a wheeled cart
and knocked it over on its side.

I think he understood some of what I was trying to explain
after that.

--

FF

(Fred the Red Shirt) wrote:

A former cow-orker of mine used to work.....
++++++++++++++++++++++++++++++++++


Barny-ard BOb

Fred

One more.

Scuba tanks have to be pressure tested every few years. This is done
in a tank of water in case they fail.

So under water testing is a common thing (except for KC-135's BG)

Big John

On 20 Nov 2003 16:42:49 -0800, (Fred the Red
Shirt) wrote:

Mark Hickey wrote in message . ..
For those of you lucky / affluent enough to afford a pressurized
aircraft, here is the way NOT to test yours:

http://disastercity.com/kc135/


This is why whenever possible pressure testing should be
done with water, rather than air. Not an option in this
instance.

A former cow-orker of mine used to work for Cleveland Pneumatic
Tools which, in addition to aircraft landing gear, made these
big whatchamacallems, pressure chambers like deep sea divers
might sit in for a few hours to prevent the bends. Anyhow,
he saw one fail hydro testing one time. Said it looked like
a small tsunami as the water swept accross the shop. Had they
tested it with air it might have killed everyone in the room.

Back in another life when I was a contract engineer for a company
that made radiation monitoring equipment our QA technician was
hydrotesting a 'volume' for one of my jobs and I stopped
by to see how it was going, and also to be sure he didn't
have the radiation detector inside when he filled it with
water. He told me that he must have trapped an air bubble
in the volume because it took many strokes of the pump to get
the volume up to the correct pressure (225 psi
IIRC). I stepped back a couple of feet and explained to him
some of the differences between compressible fluids like air
and incompressible fluids like water. Then I pointed out that
1) if the volume he was testing failed the test badly it just
might explode, and 2) the air bubble reduced the sensitivity of
the test rendering the result invalid anyhow.

He was unimpressed and I went back up to my office. Later that
day another engineer told me what he saw happen next. The
technician had installed a short piece of tubing and a ball
valve to be used to drain the volume. The end of the valve
pointed straight out horizontally from the volume. So when
the time was up he went and got a bucket, held the bucket
under the end of the valve expecting to catch the water as
it dribbled out, and opened the valve. The water shot
accross the room hitting an oscilliscope on a wheeled cart
and knocked it over on its side.

I think he understood some of what I was trying to explain
after that.

"Big John" wrote in message
...
Fred

One more.

Scuba tanks have to be pressure tested every few years. This is done
in a tank of water in case they fail.

So under water testing is a common thing (except for KC-135's BG)

It may be occasionally used for B-707's. Here's some pics of a test getting
underway. . .

http://www.harbornet.com/folks/shankland/test1.jpg

http://www.harbornet.com/folks/shankland/test2.jpg

http://www.harbornet.com/folks/shankland/test3.jpg

Rich S.

From: "Rich S."

It may be occasionally used for B-707's. Here's some pics of a test getting
underway. . .

http://www.harbornet.com/folks/shankland/test1.jpg

http://www.harbornet.com/folks/shankland/test2.jpg

http://www.harbornet.com/folks/shankland/test3.jpg

Rich S.

What is the story behind those pictures?

Dan, U. S. Air Force, retired

B2431 wrote:
From: "Rich S."

It may be occasionally used for B-707's. Here's some pics of a test getting
underway. . .

http://www.harbornet.com/folks/shankland/test1.jpg

http://www.harbornet.com/folks/shankland/test2.jpg

http://www.harbornet.com/folks/shankland/test3.jpg

Rich S.


What is the story behind those pictures?

Dan, U. S. Air Force, retired
Read he

http://www.everzone.org/pics/707ditch.html

Ben "glad it wasn't me" Sego

"Ben Sego" wrote in message
news
B2431 wrote:
What is the story behind those pictures?

Dan, U. S. Air Force, retired
Read he

http://www.everzone.org/pics/707ditch.html

Guess that answers the question. I didn't remember, actually - they have
just been sitting in my files for the last couple of years. Since the ones
on the web site that Ben linked are more comprehensive and have the
narrative, I'll go ahead and remove them from my server to save space.

Rich S.

Big John wrote in message . ..
Fred

One more.

Scuba tanks have to be pressure tested every few years. This is done
in a tank of water in case they fail.

So under water testing is a common thing (except for KC-135's BG)

Big John


IIUC Scuba tanks are routinely filled while submerged in water for
cooling purposes. In the examples I gave the vessels were pressure
tested while FILLED with water so that there was no compressed air
inside.

In the scuba example the water ouside the pressure vessel provides
(some I suppose) protection from the explosion should it fail.

In the earlier examples, filling the pressure vessel with water
prevents an explosion should the vessel fail.

Just to be clear.

--

FF

"Fred the Red Shirt" wrote in message
om...

IIUC Scuba tanks are routinely filled while submerged in water for
cooling purposes. In the examples I gave the vessels were pressure
tested while FILLED with water so that there was no compressed air
inside.

In the scuba example the water ouside the pressure vessel provides
(some I suppose) protection from the explosion should it fail.

In the earlier examples, filling the pressure vessel with water
prevents an explosion should the vessel fail.

Just to be clear.

Scuba tanks are filled with air while immersed for cooling and protection.
They are also hydrostatically tested every five years, during which they are
filled with water to mitigate expansion if they fail.

Rich S.