Preparing new pipes for service

[StoneCold]

I have some small carbon steel pipes (1 inch) that have been sitting open to the weather for about a year. I now want to finish the piping run and use them for clean solvent transfer. The problem is that the existing piping is now rusted on inside near the welded areas. How would you go about cleaning the pipes and commissioning them? Shot peen the pipe? Pump an abraisive slurry through them? Throw them out an get new pipe? Could you acid wash them to remove the rust?


Thanks
StoneCold

 

[lilliput1]

I'd throw them out. Piping material is cheap. You should not used used piping for new installation. You will be liable for problems that may result.

 

[StoneCold]

lilliput1
The piping is not used, it was just never commisioned. You know, typical dead project that is now being resurected.

 

[jay165]

I would talk to Halliburton or another company that field cleans heat exchangers. They routinely use steam and chemical lances to clean small diameter heat exchanger tubes. I would imagine they also have specialized procedures to passivate the inside after cleaning.

 

[pmover]

something to consider...

proceed with fabrication of the piping system and include connections/fittings for conducting a mild citric acid cleaning of entire system. there are firms that specialize in cleaning of piping systems &/or equipment and these firms should also be responsible for disposal of cleaning solution and any debris removed from piping system.

might want to compare cleaning costs with costs of new pipe/fittings.

good luck!
-pmover

 

[gmorin]

Depending on how clean you need to be, you might be able to get away with an air or steam blow (I don't think a water lance goes down to 1" diam) but both are a hassle.

I agree with pmover. Acid cleaning is probably the way to go if anything (assuming that the system is assembled with the rusty pipe - if you can send the pipe out to get cleaned & returned, then maybe you have more options). When you commission a boiler you would do an acid cleaning to remove mill scale. I think it would also take care of rust. It generally involves citric acid, a pump and a small boiler to heat the solution up a little. The key to the above comment is getting the cleaning company to take care of disposal. Chances are your waste treatment system isn't set up for it.

 

[StoneCold]

Thanks guys
Jay165 I only have about 120ft of pipe so I don't think Haliburton is interested in my problem.

Pmover and Gmorin I am going to try the citric acid bath in the lab. If that works I will probably do it on the pipe in the field after it is all assembled. I am at a chemical company so we can deal with the waste workup.
If it seems very difficult we will just install new pipe. However even new pipe cah be rusty and this might be a great way to commision the piping system. Acid wash then rinse with water then dry with solvent and N2.

Thanks guys.
StoneCold

 

[IRstuff]

The commercial product CLR might also work for this

TTFN

 

[krb]

You may want to contact a company like GE Water Technologies, Nalco, of some of the other companies that provide water treatment. Many of them have chemicals to clean and passivate piping.

 

[phex]

For the removal of rust and cinder, pickling with 6 to 8 wt-% HCl and passivation with phosphate solution is used in our site right now. I would presume, this will be successfull even with very rusty piping.

citric acid may be working also, though I would presume this will take longer than HCl. With concentrations in this range, you have corrosion of 2 to 20 mm per annum, so you don't have to fear any substancial loss of wall thickness. The typical duration until clean would be about 8 hours of circulation.

Keep in mind to absolutely exclude dead ends, as the acid will probably sit in there. When you dry out with dry air, the acid in the dead ends will be partly evaporated and kill the passivation. It will also promote a new layer of rust very fast.

I just had about two weeks of fun on exactly this topic. You need to observe the pickling very closely.

hth,
chris

 

[dunn782]

There are a couple ways to clean this pipe. A 5% w/w hydrochloric acid solution or a 5% - 6% w/w sodium bisulfate (dry acid) solution will work well. Both are available at a pool shop. Mix the solution in a plastic drum and pump it through the line back to the drum. A small plastic diaphgram pump works well. Do this for an hour or so the flush it well with water. That should take out any rust in the line as well as any mill scale in it.

 

[s0eebuch]

The acid clean used for commissioning boilers is normally called a 'boil-out'. We always used a TSP and caustic soda (in flake form) mixer, but I know Nalco has some proprietary 'boil-out' chemicals that are more environmentally friendly.

We never used them to remove rust (we were an OEM and our boilers were installed/commissioned soon after fabrication), but it is definately worth a try, esp. if you can do a test in your lab.

good luck.

 

[steveen]

Stonecold,

Check with Praxair's sandjet technology. Uses nitrogen and sand. Leaves a bright metal surface which can be followed by a epoxy liner....