A different steam tracing problem

[StoneCold]

I have a 2" waste water line that is used intermittantly. I want to steam trace it for freeze protection. The line is about 150ft long. The ideal way to heat trace it for me is to start at one end and run out and back to the starting point. Then trap the steam back near the starting point. I want to run 1/2" copper tubing for the steam tracing but I am concerned that since the total length is 300 ft that I am going to have too long a run and it will freeze. Where can I find out about how long a run I can make without having problems? (My steam pressure is 75psig and my condensate header presssure is about 5 psig.)

Thanks

 

[chief]

You should not have a problem, if your lagging /insulation is maintained in good condition and your steam trap is correctly sized.

Offshore Engineering&Design

 

[pleckner]

It is good piping design practice to put in a steam trap about every 100 feet of pipe.

 

[StoneCold]

pleckner
I agree with you but I have this specical case where if I ran down the pipe and back that I would not have to run a separate steam line and condenstate line to about the middle of the piping run and then do the heat tracing with two shorter loops. So it will cut my initial install costs to about a third of the other design, if it will work???

Regards
StoneCold

 

[TBP]

If it's a horizontal waste water line, I doubt you'll be able to slope it properly over even the 150 feet out, let alone back. If the condensate is being returned to the boiler, I'd go stainless steel tubing. Steam in copper isn't a big problem, but you'll have condensate forming and running along the bottom of the tubing for at least a big chunk of it's length. Copper in contact with condensate can cause problems back at the boiler. The copper in and of itself won't cause a problem, but if another factor related to water treatment chemistry is present, copper can carry back to the boiler. If that happens, it's VERY nasty to deal with.

 

[europipe]

Thermon has a special solution for this;
it doesn't give all the heat at the beginning of the tracer,but with special cement between the pipe and the tracer, it' regulated, so the tracer can be much longer too.

 

[pennpiper]

StoneCold
You wrote:
"I have a 2" waste water line that is used intermittantly."

If this is true, then why not save a lot of time, effort and money by just shutting off the line at a safe (warm) place and draining it? Leave it "dry" until the next time it is needed.

 

[StoneCold]

Pennpiper
The line is used by multiple people. Some of those people are considerate and do blow the line down with air so that it is empty and will not freeze. Others are less helpful and will leave the line full and when it freezes it is someone else's problem. I also though of adding a small pig system to the line but that also takes follow through that is lacking in some of the users.

Regards
StoneCold

 

[dcasto]

don't forget to look at the expansion of the tracing, I watched one such system bow uo it the air 3 feet because there was no expansion loop.

 

[jay165]

Why don't you use electric heat tracing instead?

 

[dppalmer]

Since this tracing is only for freeze-protection, you may want to add a thermostatic control valve (Ogontz makes one) on steam supply to tracing. This will reduce steam consumption when ambient temeberature is above freezing. That is better than relying on someone to rember to turn on the tracing during cold weather.

We typcially limit overall length for a steam tracer to 200' at our plant, but you may be able to make 300' with 1/2" tubing. Ideally, you need to estimate the condensate load for your tracer to make sure it doesn't become waterlogged because steam trap is too small.

I second remark about stainless tubing. Copper is easier to install, but tends to form oxides which plug traps and tracers after several years.