Flow Switch to detect Seal Water
Flow Switch to detect Seal Water
(OP)
I need to install a flow switch to detect Seal Water to interlock the starting of a 2300v motor. Does anyone know of a product that they may have used in a simliar application?





RE: Flow Switch to detect Seal Water
RE: Flow Switch to detect Seal Water
RE: Flow Switch to detect Seal Water
RE: Flow Switch to detect Seal Water
I have had many bad experiences with flow switches, in particular where they spend a long time in the activated position. When you need them to work, they are stuck closed. In a clean lube oil application I have seen 50% failure. For this reason I almost never buy flow switches and I will not recommend one.
If you have a situation where the flow shuts off when the motor stops at least make sure that the switch indicates low flow as a permissive to re-start. Some mechanical seals have a very low flow rate, you might also consider using a pressure switch (water pressure at seal).
If it's a critical application I would recommend using a flow or pressure transmitter or at least a flow switch operating on the principle of rotating paddle e.g. Signet.
Good luck
Roy (Instrumentation consultant)
RE: Flow Switch to detect Seal Water
The application is a HydraPulper(grinds paper with water into pulp)does this with a 2300v motor connected to an agitator in the bottom of the vessel. There is a Seal at the propeller that needs constant water flow for positive pressure that prevents the pulp from entering. The flow is less than 5 GPM. The seal that is being used is a John Crane Split Mechanical 37FS. The issue we have is water is left off, valve handle gets closed on a repair and days later when the seal goes bad it is notice. This is very costly to replace. I think the best prevention would be an inspection sheet but I need to get cost and layout together before I present both.
RE: Flow Switch to detect Seal Water
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If we learn from our mistakes I'm getting a great education!
RE: Flow Switch to detect Seal Water
I have had bad luck with flow switches as Roy said, esp at those low rates. When I need a flow switch I always try to have a pressure switch as well.
I will look up my flow switch models when back in office Monday.
RE: Flow Switch to detect Seal Water
RE: Flow Switch to detect Seal Water