Q & A > Question Details
In what type of situations can we use 2 solenoid valves in series and when do we use 2 solenoid valves in parallel ?
23/04/2008 A: Amarjit Bakshi, Refining Hydrocarbon Technologies LLC, abakshi@rhtgulfcoast.com
The more common design will be on a big diameter line where one might want to have tight shut of requirement, and one finds that the valve size be more economical and provide safe design by two solenoid valves, and one would want these to close quick enough also. These series solenoid valves could also be used on flammable liquids which are stored or have surge capacity on site in the process unit at reasonable pressure, and rupture of line would require solenoid valves at the outlet of the surge drum for safety reasons, and could be used as block and bleed as suggested by earlier apci contributor.
As regards having a parallel solenoid valve it can also be cost effective in large high pressure vapor or liquid lines where the economics might suggest that two valevs might be advantageous and at the lines by dividing the line in the half the cross sectional area, one might not require shut off conditions due to design requirement.
03/04/2008 A: KengYong Chan, Air Products & Chemicals, Inc, chanky@apci.com
For two solenoid valves in series, I have come across a design with a bleed valve (also solenoid) in between the two solenoid valves. It is basically a double block and bleed system actuated by solenoid valves. I believe the intent of having two solenoid valves in series is to have tight isolaton. Having a bleed valve in between provides a more reliable layer of protection.
As for solenoid valves in parallel, it boils down to why there is a parallel (or bypass) line and the need to have a solenoid valve on the parallel line. This may be similiar to concept of parallel control valves for different range control.