I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.

The crack does NOT track the heat affected zone of the original weld,
in fact it is perpendicular to it.

..
|
|===========
|
!

Here the "=" signs denote the weld, and "|" signs denote the crack.

In any case, when I saw this happen, I was quite scared and
immediately relieved the compressor of pressure.

I am not yet sure what was the cause of this crack in the first
place. I will try to find what I can.

My question, obviously, concerns my repair options. I can hardly think
of any welding where more is at stake than here, due to pressure. So,
I see the following options:

1) Take off motor and pump, cut holes in the tank and throw it away,
look for another tank.

2) Repair the tank by welding and hydrotest.

Considering option 2, the first question concerns welding. How would
you weld? How do you identify where the crack ends? Would you drill
relief holes at ends of the crack?

The second question is about hydrotesting. I was thinking about
something simple, such as replace tha gauge with a 400 PSI gauge,
close off all openings besides one, fill tank with water, connect to a
hydraulic pump or grease gun, and bring pressure to 400 PSI (the tank
supports 200 PSI) and look for leaks.

This is very time consuming and I would like to know how likely would
it be that I would make some very bad mistake.
--
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"Ignoramus11135" wrote in message
...
I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.

The crack does NOT track the heat affected zone of the original weld,
in fact it is perpendicular to it.

.
|
|===========
|
!

Here the "=" signs denote the weld, and "|" signs denote the crack.

In any case, when I saw this happen, I was quite scared and
immediately relieved the compressor of pressure.

I am not yet sure what was the cause of this crack in the first
place. I will try to find what I can.

My question, obviously, concerns my repair options. I can hardly think
of any welding where more is at stake than here, due to pressure. So,
I see the following options:

1) Take off motor and pump, cut holes in the tank and throw it away,
look for another tank.

2) Repair the tank by welding and hydrotest.

Considering option 2, the first question concerns welding. How would
you weld? How do you identify where the crack ends? Would you drill
relief holes at ends of the crack?

The second question is about hydrotesting. I was thinking about
something simple, such as replace tha gauge with a 400 PSI gauge,
close off all openings besides one, fill tank with water, connect to a
hydraulic pump or grease gun, and bring pressure to 400 PSI (the tank
supports 200 PSI) and look for leaks.

This is very time consuming and I would like to know how likely would
it be that I would make some very bad mistake.

This is second hand, but I edited a number of articles from the AWS on
pressure vessels, so that's where this comes from:

The HAZ is not the central issue; tank-mounted compressors are the issue.
The AWS says don't mount compressors on tanks but everybody keeps doing it.

It's an invitation to fatigue cracks and eventual failure. The HAZ provides
a possible weakness, relative to the parent metal, along which the crack may
propagate. But it's years of vibration that starts the crack, initiated at
the hard spot located where the pump bracket attaches to the tank.

Once you have a fatigue failure, the tank is done for. Fatigue is a
cumulative effect and a fatigue crack in one place doesn't necessarily
relieve the stress, anyway. The fatigued area can surround the crack by a
large area; the rest is just waiting to go over the fatigue limit and crack.
If you weld it, you've just introduced another hard spot, which will
transmit the vibration to the surrounding area.

This may be -- probably is -- true fatigue. True fatigue occurs at loads
well below the elastic limit, after many millions of load cycles, for steel.
It's actually a pretty difficult phenomenon to analyze, because, except for
actual cracks, it's difficult to judge how far it's progressed without
destructive testing.

Put that into your hopper; I'm not claiming to have a deep knowledge of it.
But the AWS put out press releases and articles every few years about this
very issue, and I read several of them.

--
Ed Huntress

In article ,
Ignoramus11135 wrote:

1) Take off motor and pump, cut holes in the tank and throw it away,
look for another tank.
....
The second question is about hydrotesting. I was thinking about
something simple, such as replace tha gauge with a 400 PSI gauge,
close off all openings besides one, fill tank with water, connect to a
hydraulic pump or grease gun, and bring pressure to 400 PSI (the tank
supports 200 PSI) and look for leaks.

Hydrotesting is more than looking for leaks - it's also looking for
permanent deformation (the tank under test is also submerged in water,
and the amount of water that is displaced when the tank is pumped up is
checked against when the tank is depressurized afterwards - too much
permanent deformation is cause to reject a tank).

While we are a newsgroup full of folk that like to do things themselves,
the only way this would be remotely acceptable (IMNSHO) would be to have
a real hydrotest facility check it out and stamp it. But frankly, given
one failure on an old tank, I'd be wary of others - and I'd leave
welding on pressure vessels to folks certified for that specific, rather
demanding, job. In short, I suggest looking for a new/used tank. Keeping
the compressor separate from it might make it live longer.

This is very time consuming and I would like to know how likely would
it be that I would make some very bad mistake.

Go with option 1 and you're good.

--
Cats, coffee, chocolate...vices to live by

Ignoramus11135 wrote:

1) Take off motor and pump, cut holes in the tank and throw it away,
look for another tank.

If you plan to resell your end assembly, that is the way to go.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

Ignoramus11135 wrote:

I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.


This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

On 2009-01-25, Pete C. wrote:

Ignoramus11135 wrote:

I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.


This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Pete, if I find a replacement and would want to get rid of this tank,
I will let you know.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Ignoramus335 wrote:
On 2009-01-25, Pete C. wrote:
Ignoramus11135 wrote:
I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.

This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Pete, if I find a replacement and would want to get rid of this tank,
I will let you know.

Iggy, I happen to have a like-new IR 80-gallon compressor tank in
storage here in Texas.

On Sun, 25 Jan 2009 17:28:03 -0600, "Pete C."
wrote:

snip
This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Do you have any good plumbing supply houses around town? If
so see if they have any old/warranty bladder tanks lying
around. My Dad got hooked on these (old bladder tanks) years
ago. We must have had 50+ in all shapes and sizes around. He
couldn't pass up free.

They were kind of hard to get rid of back then, decent
amount of metal, but they had a thick rubber bladder trapped
inside. That shouldn't be a problem for you. Split it open
and pull that bladder out. For some images (in case you
don't know what these are) see:

http://www.amtrol.com/wellxtrol.htm

Just one make, lots of others around too.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

"Pete C." wrote in message
ster.com...

Ignoramus11135 wrote:

I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.


This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Pete
For that low pressure usage a water heater tank would work fine and they
are cheap.
Steve

RB wrote:

Ignoramus335 wrote:
On 2009-01-25, Pete C. wrote:
Ignoramus11135 wrote:
I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.

This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Pete, if I find a replacement and would want to get rid of this tank,
I will let you know.

Iggy, I happen to have a like-new IR 80-gallon compressor tank in
storage here in Texas.

I need the not-like-new ~40gal tank in TX too.

Up North wrote:

"Pete C." wrote in message
ster.com...

Ignoramus11135 wrote:

I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.


This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Pete
For that low pressure usage a water heater tank would work fine and they
are cheap.
Steve

Good idea, as is the water tank idea. I also thought of the 40gal LP
tanks and the fact that one that is past it's hydro date would be just
fine for this application too.

emailed

On 2009-01-26, RB wrote:
Ignoramus335 wrote:
On 2009-01-25, Pete C. wrote:
Ignoramus11135 wrote:
I am sure glad that I chose not to sell this 80 gallon Speedaire
compressor.

Based upon first impressions, the motor and pump run fine. However,
when bringing the tank up to pressure, I heard a hissing noise at
about 140 PSI, and realized that there is a hairline crack in the
tank, near a 2" long weld attaching the engine/pump mounting platform
to the tank.

This is the kind of tank I need for my plasma project, one that is NG
for significant pressure use, but would still be fine repaired and
operated at the perhaps 10psi I need.

80 Gal is a bit too big for my coolant tank need, but if the diameter is
within spec I could cut a section out of the middle and weld it back
together shorter.

Pete, if I find a replacement and would want to get rid of this tank,
I will let you know.

Iggy, I happen to have a like-new IR 80-gallon compressor tank in
storage here in Texas.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/