Chilled Water De-Coupler

[Jabba007]

In the recesses of my brain, I recall there being a minimum number of pipe diameters length that a decoupler should be. Can anyone refresh my memory, and/or remind me where that guideline can be found?

TIA

Jabba

 

[willard3]

Bell and Gosset Engineering Design Manual is a good place....."Primary Secondary Piping Pumping Application Manual"... P/S pumping uses decoupling:

"The common piping length is quite short and can vary between a short nipple to an approximate maximum length of two feet.'

 

[imok2]

This from Bell and Gossett:
The maximum pressure drop in the common pipe shall not exceed 1.5 ft— Establish the pressure drop in the common pipe by assuming the flow of the largest chiller pump is passing through the common pipe. The resultant pressure drop should not exceed 1.5 ft and maintain three pipe diameters of separation between the secondary supply tee and the secondary return tee—A common pipe of this length is more than adequate to eliminate mixing due to excessive return velocity in the secondary return piping. Longer length common pipes may result in an excessive pressure drop greater than 1.5 ft with results as described above.