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Help ID Old Compressor

TxRzrBk

Plastic
Joined
Oct 16, 2014
Picked up this old compressor but really have not been able to positively identify the make and model. There are a few markings on it but none of those have yielded any info.

1) Bottom of tank support stamped "Curtis"...so presumably it is an old Curtis unit. Old man who sold it to me said it was all original except the tank was painted.

2) Brass plaque on compressor pump reads MK9281

3) C-353 stamped into compressor pump head

Motor is a 2 HP GE repulsion induction MT8024. Tank is riveted along the seam. Any help figuring out make and model would be greatly appreciated.
 

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This forum needs a "sticky" regarding riveted air tanks

This forum needs a "sticky" or other readily-reference-able material about riveted air tanks. The topic of old air compressors comes up at least once a month, sometimes even more often.

Somebody who writes very well, maybe Joe Michaels, could summarize the necessary precautions in a PM to the moderator, and the moderator could then make this a "sticky."

An alternative would be to put the past wisdom into "greatest hits and links", so we could reference it each time this topic comes up.

This is an attractive old compressor, but that tank gives me the willies. The design seems to be amenable to replacement of the tank with a new ASME-stamped tank, without destroying the funky old fashioned appeal of the machine.

There is an FS-Curtis air compressor company on the web: FS-Curtis Air Compressors - International Compressor Manufacturer Global Sites The OP might want to send them an inquiry.

John Ruth
 
I guess I should have mentioned in my original post that I am aware of the safety concerns with older compressor tanks and riveted tanks alike. I won't be putting it into service without the proper precaution to verify it is sound and safe. As a side note, I am not sure why everyone freaks out about rivets, more than likely you have driven across many bridges that are constructed with rivets, the brooklyn bridge being one of them. Lets not get off into the weeds on tank construction and stories about people blowing their shops apart, I really don't need any info there but hope someone can help me figure out more about the compressor model, age etc.
 
Age up to mid 50's for motor, older for tank..

Slightly earlier looking Curtiss compressor ads, on Epay with 1921 dates..

You BETTER worry about rivited air tanks...

It is not so much the rivits themselves.. It is just the plain old... AGE of the tank..

Do you have an ultrasound wall thickness map of tank??. Current hydrotest?? Interior inspection??

A current inspection, by a shop that has the R stamp??

If not, dump the tank... PERIOD..

Tanks are designed for a certain lifspan (as are Bridges..)

Bridges are constantly inspected.. And still fail... Killing people..

Tanks... rivited or non rivited, also fail.... Killing people..

Aircraft (rivited) after many pressure cycles, fail.. Killing people..

If you come to a place like this for info/advice, it should be listened to..
 
Thanks for the information on the age. I say again... I am aware of the concerns about the tank and will take the necessary precautions.
 
In my shop, I have a Curtis compressor that is from the mid-40's. Almost have it's complete provenance. Was put into a auto repair shop around 1946 or 47 when new. We acquired the building somewhere around 1958, and the compressor came with it. Used it ever since.

The compressor you have looks very, very, similar. Typical 2-stage job like Curtis made for years. Yours lacks the pressure release on the head that later designs used. Since all welded construction of tanks, legs, and mounting brackets were the norm since at least the war years (like mine), I would posit that you compressor is no newer than 1935, and is probably from the late 20's. Motor has been replaced, and is perhaps late 50's on up.

Just a guess.
 
Railroad locomotive air reservoir tanks are often drilled a certain depth into the shell along the bottom, the idea being that after corrosion reduces thickness so far it would open up one of the drill holes giving a "tell tale" indication that its time to condemn the tank. The tank on this compressor looks very similar to a reservoir that would be found under the running board of a steam locomotive. And many operating steamers still use their old riveted reservoir tanks.
 
In my shop, I have a Curtis compressor that is from the mid-40's. Almost have it's complete provenance. Was put into a auto repair shop around 1946 or 47 when new. We acquired the building somewhere around 1958, and the compressor came with it. Used it ever since.

The compressor you have looks very, very, similar.

Thanks! Do you happen to have a picture of yours you could share? Is the plaque on the compressor a model number or a serial number? I have reached out to Curtis and apparently the person who has knowledge of the compressor's of that age won't be back in the office for a week or so.

In terms of a riveted tank and it's suitability for service I really don't see it as a debatable topic, the tank has been in service for 70+ years which speaks for itself. I understand it could be rusted, cracked etc etc and I will make sure it is safe if I decide to use it.
 
I believe the MK9281 is a serial number. I scraped some paint off and found the base of the pump has D-200 cast into it. D-X would be consistent with Curtis compressors. Anyone know anything about a Curtis D-200 ?
 
Over the years, it's been my observation, that folks will ask for your opinion, when what they actually want, is confirmation of their own opinion.

That's just the way of the World .....


It's my opinion, that Pressure Tanks are inexpensive, and readily available, ... therefore there's no good reason to use one that's in any way questionable.



.
 
I know! It is a United States model MK that was manufactured somewhere in Ohio. I think some were sold with Curtis name in 1950s-60s; the tank looks much older. Use a magnet to check if the tank is steel or brass.
 
Old Compressor

Since we learned of the horrors of rivets, old tanks, etc, I am glad someone is trying to answer the question about the origin and date of the compressor... Great looking old unit and I love repuslion start motors...I have a late model Ingersoll t30 that has rust issues on the end of its horizontal tank.. I have cleaned the rust, treated with Chemprime and painted the rusty spot a cpl of times.... I don't know how thick the tank is but I hope it outlasts me.. Cheers; Ramsay 1:)
 
If you want some thoughts on the riveted tank and it's suitability for continued service, give me a PM.

Joe in NH
NHPE #8633

Sorry, I can't resist.

The big issue with ANY tank is corrosion from the moisture inherent in the compression. Moisture and humid air corrodes steel.

One of the nice things about riveted construction is that all riveted joints have a "joint efficiency" - which means the plates are made thicker than theory required for hoop stress alone. Single row rivets typically introduce a 57 percent joint efficiency which means the plates are 1/.57 or 75 percent thicker than hoop stress theory requires - and exists simply to make the riveted joint.

One steam boiler hobbyist of my acquaintance call this "my corrosion safety factor" - a term of some accuracy AS LONG AS YOU DON'T CONSIDER corrosion which may occur in the rivet stress area.

Generally horizontal riveted tanks are constructed so that the longitudinal joint is NOT directly at the bottom, but rather at the 2 o'clock position or the 4 o'clock position. This done for corrosion reasons. Horizontal boilers tend to choose the 4 o'clock position because this locates the longitudinal seam "away" from the boiler waterline which normally would appear at the 2 o'clock position.

So yes, a riveted air tank CAN be a hazard, but it also MAY NOT be depending on the corrosion/ultrasonic/magnetic thickness scan and where the joint is relative to the corrosion.

A power plant of my former experience had riveted VERTICAL tanks. These were sounded out annually as part of the Insurance coverage for the plant. The big concern for these was the lower circumferential joint where the head was attached to the vessel. But these tanks were always found OK, had been in service since 1941, and while there was corrosion, its circumferential joints are subject to HALF the stress of a longitudinal joint. I.e. for this joint a "double corrosion allowance."

Well, the tanks did have a longitudinal joint too.

AND - just for comparison sake, a welded tank joint strength in calculation frequently is taken at 100 percent of the strength of the shell plates where it is made (it can be actually MORE than the shell if the weld bead is left unground) but corrosion allowance on riveted construction usually does not exceed 20 percent additional thickness. Thus riveted tanks with up to 75 percent overkill may actually be SAFER than equivalent welded construction - corrosion wise.

Joe in NH
 
The issue of riveted tanks vs welded tanks is really not the cause for our concern. I routinely do engineering to evaluate steam locomotive boilers with riveted construction, determine fitness for service based on CURRENT inspections and ultrasonic thickness gauge readings.

Here is the low-down, not in any particular order:

1. Air receivers (tanks) are notorious for accumulating condensate (water + "tramp oil" from the compressor). This condensate lays in the bottom of the receiver and causes significant corrosion with resulting loss of material from the shell (or head if a vertical receiver).

2. Air is a compressible substance. When contained in an air receiver, it stores a tremendous amount of energy. If an air receiver has a rupture of its shell due to internal corrosion, the resulting escape of compressed air is usually explosive. The air expands back to its volume at atmospheric pressure, which is several hundred times the volume it occupied inside the receiver. In so doing, the common mode of failure is for the area which "blew through" to be the start of an "unzipping". Often, air receivers that fail in service will blast themselves into shrapnel packing considerable energy.

3. At the powerplant I retired from, we had some huge compressed air receivers (8000 gallons apiece x 12 of them, air at 140 psig). Each year, the insurance company would send out a team of engineers for "risk assessment". Being the senior mechanical engineer, I'd take these engineers around the plant and we'd go over any forced outages, equipment failures, improvements or modifications, and also go over the maintenance records. The insurance company engineers usually had a new horror story about some air receiver blasting itself to bits and taking out a good bit of the surrounding plant. These were WELDED construction air receivers, but had not had any inspection or testing done in ages. The failures were always due to internal corrosion from condensate.

4. In an ideal world, if a person were to evaluate an air receiver to determine its "fitness for service", here is how it would be done:
1. The receiver is inspected for any signs of damage, and for any alterations or repairs. Welded repairs "scabbed onto" old receivers, done by persons unknown,
are cause to cut that receiver up for scrap right then and there. Seeing pipes stabbed into an air receiver ringed with bird-shit welding and no compensation
(reinforcement) around the penetration thru the shell of the receiver is a big red flag.

2. Assuming the air receiver shows no signs of damage or modifications or sloppy repairs, the next step is to draw a grid on it with soapstone or similar, and lightly
grind off the paint in the center of each grid square. Once this is done, the thickness at each of these points is determined by ultrasonic thickness gauging.

3. If no working drawings exist for the receiver, a set of "as built" drawings has to be made based on measuring the reciever. Riveted seams present a little
more challenge as the diameter of the rivet shanks is not known. I take the dimensions/shape of the rivet heads and look up the shank diameters for those heads.
If several references show several shank diameters, I use the least diameter.

4. We use a Minimum Factor of Safety of 5.0 for calculations on pressure vessels. Without mill test reports on the steel the air receiver is made of, I would use
a minimum tensile strength of 50,000 psi, and with a FS = 5, this reduces the ALLOWABLE tensile stress to 10,000 psi.

5. I then run a full set of calculations for the receiver (or boiler). Riveted seams, as Joe in NH correctly states, have to have their efficiency calculated.
This efficiency along with the UT reading at the thinnest point will determine the maximum allowable working pressure (MAWP) the receiver can be operated at.
The efficiency of a riveted seam will result in the MAWP being a good deal lower than if the receiver were simply a cylindrical shell. I use an efficiency of
0.90 for welded seams (which is what the American Society of Mechanical Engineers calls for in Section I, the power boiler code). As I recall from calculations
I;ve done on numerous locomotive boilers, a longitudinal seam with "welt plates" inside and out, with three rows of riveting, will usually have an efficiency
around 84 %. A lapped seam of the sort on the OP's air receiver will have a much lower efficiency and corresponding reduction in MAWP.

6. In the 1920's, it was common for tank shops to build air receivers using riveted seams and then seal weld using oxyacetylene welding. I would not be put off by
welding along the seams rather than calking.

7. The internal condition of the receiver and the complete design of the longitudinal seam are unknowns. From the photo, the seam is a lapped seam, double row
riveted. In today's world we do have fiberoptic 'scopes and can get a look inside things like this air receiver. I would include an internal inspection as part of
evaluating this receiver's fitness for service. Ultrasonic thickness gauging is great, but it is not an absolute, and is only done at a series of points on the
receiver. If I get a low reading at any UT location, I move around that point and get more readings to either corroborate or determine if the low reading is an
anomaly. In old steel plate, "laminations" which are mill scale rolled into the plate at the mills, are common. These laminations do not hurt anything, but will
reflect the ultrasonic beam and give a lower thickness reading. Similarly, small pits will do the same thing. However, localized "wastage" or loss of metal
may be present, and this is why if I see a suspiciously low thickness reading, I "blanket that area" with UT readings.

8. Once I had determined the MAWP based on a minimum FS = 5 and using the minimum thickness readings, if there was enough left of the receiver to hold working air
pressures, I would give the receiver a hydrostatic pressure test (known as a "hydro"). This test is done using WATER. Water is incompressible, so if the tank
should rupture, the release of water will not produce a violent expansion and ripping apart of the tank.

9. The hydro test is done to 1.25 X MAWP, with MAWP determined by calculations base on as-found UT readings and physical inspection of the receiver.

5. The receiver, from the photos, has a "radiator drain petcock" on the bottom. This is the kind of petcock used to drain automotive radiators. Nothing wrong with it, but it is in an inconspicuous location, and not something that will pass a lot of water when opened. I'd bet that petcock was opened very infrequently. Each Sadie Hawkins Day would be a stretch, if that often. I am inclined to bet that there is significant loss of metal in the bottom of that air receiver (approximately 6:00 on the "barrel").

6. Blowing down air receivers to clear out condensate is something that has to be done daily. It also has to be done for a long enough period of time to get all the condensate out of the receiver. A restricted opening like that radiator petcock will spit and sputter and not really "blow clear" unless it is left open for a good few minutes. It is also a question of whether the receiver was set with a downhill pitch so that condensate ran toward that drain petcock.

What is a well settled point here is that old/unknown air receivers are potential bombs. Unless the OP is prepared to go the whole 9 yards as far as determining actual minimum thicknesses and running the numbers followed by a hydro test, my advice is to cut that air receiver lengthwise in two and use it for a planter or watering trough.

As Joe in NH notes, I also have seen old riveted tanks and boilers which held up remarkably well in service, and I've seen newer welded air receivers that went paper-thin due to internal corrosion.

As an illustration of what a "little homeowner grade" air receiver can do when it fails: a neighbor to my buddy's automotive shop bought a used air compressor at a yard sale. It was one of those homeowner specials, direct drive, noisy, and mounted on its own air receiver. The neighbor fired up this compressor outside his house, which is next door to my buddy's shop. My buddy said he heard a hell of a bang and then a thud. He went outside to see what had happened. The neighbor was standing in his backyard, looking up at the compressor which had landed on the roof of a one story portion of his house. The neighbor admitted that when he fired up the compressor, there was a "small leak" in their air receiver, but he figured if the compressor could keep up with it and maintain air pressure, he'd use it as it was. While he was thinking of this shrewd maneuver and seeing if the compressor could keep up with the leak, the receiver "unzipped", rupturing open. The resulting blast of expanding compressed air launched the compressor and what was left of the receiver up into the air, and it came down on the back roof of the house.

In short, if a person wants to use an old air receiver without properly determining its fitness for service, that is their choice. So long as they do it in a location where no one else gets taken along for the ride if the receiver blows apart, that is their own fault. I'd suggest the OP, if he is intent on using that old receiver without proper evaluation and testing, start reading his insurance policies to be sure injuries, death, or property damage caused by an exploding air receiver are covered.
 








 
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