Liquid removal from a pipeline

[ucfmech]

My company manufactures a heater used to heat a thermofluid which is then transported around an asphalt plant to keep the asphalt hot. Inside the heater is a large helical coil through which the thermofluid flows. Before shipping, we test the heater with thermofluid. The problem we're having is removing the thermofluid after testing is completed, and since the helical coil is so large, this adds a significant amount of weight to the heater, making it more expensive to ship. The thermofluid is basically an oil. Is there any way to effectively and cheaply remove this oil from our coil? I've looked at pigging, but I'm wondering if there are other ways possible. Thanks for any help.

 

[ash9144]

Blow it out with nitrogen

 

[ucfmech]

We've been trying to blow it out with an air compressor, the problem is that the pipes have an ID of 2", and not all the oil is removed. Will nitrogen work differently than regularly compressed air?

 

[zdas04]

No, nitrogen will not work differently from compressed air. It is available in bottles and doesn't require a compressor, but if you already have a compressor using nitrogen is an unnecessary expense.

The most efficient and effective way to do it is to put a turbo pig in the line and blow it out with compressed gas (either nitrogen or an air compressor). You will be amazed at how effective this is and with how little pressure and time is required to run the pig. You'll wonder why you resisted pigging (in fact I'm already wondering that).

Blowing the oil out without a seal always causes bypassed flow. It will take between 5 and 30 pipe volumes to blow the oil out without a pig. With a pig going in high on the system, you can do it with less than twice the pipe volume of gas. If you can't go in high on the system, then you'll have to raise the pressure high enough to overcome hydrostatic pressure and you'll use a bit more gas.

David

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"

 

[ucfmech]

The reason we have ressited pigging is the amount of time it would take to disconnect other piping from the heater in order to reach the helical coil on the inside of the heater. However, I've been viewing it as a neccessary expense in order to effectively remove the remaining thermofluid. Just trying to make everyone happy if I can, but you know how that often goes.

 

[zdas04]

You can also try a foam pig, those suckers will make just about any turn (I once ran a 10-inch foam pig out a 2-inch vent, tore it up, but it made it). That way you might be able to avoid disconnecting any pipe.

David

 

[racookpe1978]

Where is your drain? Where is the vent (N2 inlet) w/r to the natural drain of the coil? Will the bottoms of the coil actually drain at all or do they trap the oil so deep that pressure won't empty the lines?

How much time are you allowing for draining? You can drain 95% of the oil in a 2 inch flex hose in 4 minutes, then we had to wait 2 days for the rest to ooze down and out recently while trying to ship out an oil flush rig. .

If you're worried about weight, just drain the 90% amount that flows out quickly, drive to the next station, re-load. (Are you sure the wait and drain and re-fill time make the extra weight really important? Overall - economy requires everything be considered, not just the little problem of weight.)