2 replies to this topic

[chem2013]

Dear All,

 

For a closed loop drinking water network, does it require to have a back pressure control valve on the return header to control return header pressure of 3.0 barg? alternatively, does it require an orifice  in place of control valve?

 

Drinking water supply pressure at various unit B/L is 4.5 barg and return pressure is specified as 3.0 barg. These are specified as normal condition at various unit's B/L.

 

Drinking water system has a continuous return flow from each users and there are continuous consumption of drinking water for some of the users. All users are specified with certain peak consumption of drinking water.

 

I think, back pressure control is not required on return header. Also, orifice is not required.

 

Please share your opinion.

 

Regards.

[Dazzler]

Maintaining a minimum back pressure is important for allowing the system:

• Adequately flow into each user particularly during a high demand period (many or all users on). Otherwise those at the end of the network may suffer low pressure.
• Efficient pumping (so the pump does not operate too far either way on the pump curve from its ideal duty point).
• Helping ensure no back flow from users occurs into the network. Contamination.
• Possibly also prevents flow surges and fluid hammer when users suddenly stop/start.

[Ikka]

I couldn't really understand why you have a return line, instead why can't you just have a minimum flow bypass.

 

As Dazzler mentioned, maintaining a back pressure will ensure a constant supply even to a member at hydraulically most remote. If you have return header either you add a back pressure control or provide an orifice which can ensure pump minimum flow. An economics shall be considered before choosing either of these options.