100 year old pipe ratings 1

[gjf36]

I have 100 year old pipes at a milk products factory that run's 24 hours per day. I need to find out their ratings (pressure, thicknesses etc,) but have no way of doing so with out shutting down the plant which is impossible. I do not have a large budget on tap, so ultrasounds etc are not viable. The pipe is brandless but cast-iron, and it has an external diameter of approx 4 and a bit inches, so I assume it is a 4 inch pipe. If anyone could help I would be hugely greatful, as this is part of a summer engineering job I have and cannot go much further with out this.

 

[TD2K]

I don't see any way of getting this information from essentially a visual inspection.

If you need to determine pressure rating, that needs the material to be known and thicknesses to be measured. There isn't any other way in my opinion. You can't go off what the thickness 'should' be when the pipe was new, even if you were sure you knew that information, because of its age and possible internal corrosion.

Materials can be analyzed on line with portable nuclear analyzers and thicknesses can be done with ultrasonic meters. I realize you said that you don't have the budget for this but I think someone is asking an impossible task of you and this is going to be GIGO (garbage in, garbage out) if it's not done correctly.

 

[JOM]

gif,

What service are these pipes being used for? Surely not steam or chemical? Are they pressurised? It's not hard to find 100 year old waste pipes.

Just incidentally, how do you know they are 100 years old? Not doubting you, it's an interesting problem. I gather you're in the Southern Hemisphere, since this is a summer job.

JOM Cheers,
John.

 

[gjf36]

The pipes were installed when the factory was built in 1902, and there is no record of the replacement of these pipes. Also the exact route is the same as the original plan.
The pipes contain pressurised water, to wash the butter which is being made. The estimated flow rate is about 20L/s but that is debate-able, and is what I eventually want to calculate. And you are right, I am in New Zealand.

 

[saxon]

gif, If this pipe is as old as you say it is, corrosion or erosion is a distinct possibility. Ultrasonics is one possibility for tessting metal thickness in place, but this doesn't give you the info you need to make a material determination. Your best bet would be to get a sample pipe section from the line, send a portion out for analysis to a good metallurgical lab. Perhaps the lab can also work up which specfic alloying system this is. If not, you'll need to contact the ASTM office and Library in Cleveland Ohio to do a search through their extensive files (at one time they had the alloying structures for all steels produced in the U.S. since the begining). One note, older forged and wrought pipe has better corrosion properties than the current alloying systems now in use (nobody seems to know why). Also check at the "Piping Design Central" web site, you might get some ideas there.

With this sample section you can also then work up the I.D. and O.D. and hence the thickness. With this info you should be able to work up the P/T ratings and allowable stress based on the B31.1 Pressure Piping code.

If you can't get a sample specimen, it's going to be really hard to figure out what you've actually got an its condition.

Good Luck!

saxon

 

[JOM]

Hi gif,

I thought you might be in New Zealand. I was going to get cheeky and offer you some of our 50-year old piping as replacement.

Keep us up to date as you to what you learn.
Cheers,
John.