Flow switches

[vjr0512]

We have flow switches installed on the pump discharge and this is a start permissive for the starting of the pump . This pump is pumping the aviation fuel to the helicopter and is a positive displacement pump. Client is objecting to use Flow switches and asks to use Flow transmitter as the Flow switches are not reliable and may "stick" sometimes and may give wrong action to pump to start and if there are no flow to the pump the pump may get damaged.

My question is , whether the flow switches are so unreliable?

 

[LittleInch]

What type is your flow switch? Most I've seen are some sort of mechanical flap design which can stick open or fail to indicate flow if the paddle falls off or becomes damaged. However pumping what I hope is very clean, water free fuel to a helicopter they should be ok.

Having said that, flow transmitters especially using non intrusive techniques are now available at low cost and can provide flow info and a "switch" within the transmitter at higher reliability.

Your description sounds a bit odd though as normally flow switches are used to indicate no flow alarms or shut downs rather than a permissive to start, but if that's how it's set up then your client is essentially correct IMO.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[vjr0512]

Yes .You are right littleinch. This switch is a mechanical flap design and i now understand that Client concern is correct. We will go ahead with the transmitter. Thanks for your valuable feedback.