"Positive" pressure assurance in pumping systems.

[gbratis]

Dear friend,
My query may seem quite inane but I would like you to advise me on how to assure that a pipeline operates always in a "positive" pressure at the highest elevation point and the liquid colume doesn't split even if pumps provide sufficient head. For example I'm trying to pump an amount of product from a higher elevation point to a lower,with a pipeline profile that followes ground elevation that forms a high point. Do I have to foresee a back pressure control loop? How can I achieve that?
Thanks in advance.

 

[BigInch]

Theoretically it could be done with a backpressure loop, there is generally be too much play in the system to do it reliably. Generally, it takes too long for the pipeline column packing or depacking to respond to the feed back loop and tuning it is a nightmare. When there is low pressure and high pressure areas involved, the volume to pressure ratio varies a lot over the segment, so its hard to get it right. My client has not had much luck when they tried to let the SCADA system do it automatically. They have a 2800 meter rise and an 800 meter drop in one case and 1500 meter rise and 1000 meter drop in another with extreme temperature variations to the high side making for high vapor pressures. I've set their backpressures at the receiving stations or backpressure control points to give a 50-100 psi or so above a given product's vapor pressure at the mountain tops. I usually calculate different settings for different products in the line, and/or for various temperature conditons throughout the year (with some safety factor for normal operational swings) and include those settings in the pipeline operating manual. The operators make the set point changes themselves. You might be able to do it automatically if your pipeline segment is towards the short side and pressure changes are not dramatic.

If its multiproduct line, don't ever let the vapor pressure go low when an interface is transiting. What a mess that can make.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[stanier]

Are we talking here of a hydrocarbon pipeline or water/wastewater? The solutions may be very different based on the product.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[BigInch]

I know its HC. "Product" simply just could not be water or waste water. I bet.. I bet.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com