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[rak_iam]

Hello there,

 

We have one debutanizer overhead cooler with sea water as cooling media on tube side. Supply & return headers are on ground level with supply pressure of 25 psig and return header is kept open to sea out side of refinery. Cooler is at elevated level of 5 mtrs above ground. Both supply and return piping are of 6 inch each. Supply and return headers are of 30 inch and 24 inch resp.

 

It is observe that vacuum being produced on return line of cooler at 7 inHg. When throttling the return valve to 80%, then only the positive pressure (1 psig) seen on gauge. We are facing low HT efficiency of cooler.

 

Is the vacuum creation because of cooler at above ground? or due to pressure loss on tube side? 28 psi loss on tube side can be expected?

 

Any thoughts and remedy?

 

Thanks in Advance.

[Pilesar]

The vacuum results from the gravity flow. Throttling the return line is the solution to keep the pipe full of liquid. See "Designing Piping for Gravity Flow" by P.D. Hills for a good explanation. The article is available on the internet. Search this forum for several past discussions about gravity flow (if you can get the search function to work... it causes me troubles often.)  Art Montemayor converted the Hills article into spreadsheet format which is available somewhere from this site.