Recommended pipe velocities for hot thermal oil 1

[Mech85]

I am looking for some data on recommended pipe line velocities for thermal oil operating at 300 Deg C (572 Deg F) and at 120 Deg C (248 Deg F). The oil SG varies from approximately 0.9 to 0.8 and viscosity from approximately 0.8 to 0.5 centipoise.

Using "typical" line velocities for water, I am currently reviewing a 3" schedule 40 ring main with a velocity of 2.6m/s (8.5 fps) and am considering the need for an increase to 4" Schedule 40. I have already emailed two thermal oil suppliers and received no reply as yet. Can anyone advise some more relevant data.

 

[fredb]

Hello,

go to:

http://www.copcoltd.com/soft/freeeng05/pipez.htm

 

[TD2K]

8.5 ft/sec for hot oil wouldn't concern me if you are concerned about erosion. Ultimately, it's the pressure drop through the ring system that I would concentrate on ensuring is adequate since that drives the available dP through each user.

A 4" line (assuming sch 40) is going to drop the velocities to about 5 ft/sec.

 

[nealc]

Very application specific question. I reularly see systems for loading and unloading similar oils (at blending plants) into tank cars where the velocity is 10-15 ft/s, and most gas and diesel is loaded at 15 ft/s and higher. For these, systems have lasted 15+ years with schedule 40 A105 piping and short radius (1x) elbows. These are short runs of pipe loading into tank cars, so pressure drop is not an issue.

 

[CRG]

This is a question of economics.
For a given flow of oil:

The smaller diameter pipe the more it cost to pump the oil through it. The first cost of the pipe is typically less the smaller the pipe. The first cost of the pump is more the smaller the pipe. The annual expense is greater to pump because of friction losses and maintenance of the higher pressure pump. If there are erosion issues, there will be shorter the life of the piping system at the higher velocities. With higher fluid velocities, there will be greater transient pressures which will require larger pipe anchors. On and on ….

Now the rules of thumbs for pipeline velocities take into account many of these factors, but not all. If you want to find the ideal velocity for pumping your product, perform a cost analysis of the system.

CRG