Float switch with 'push to test'

[kcj]

I have a requirement for a hydraulic tank level (float) switch that can be tested daily for operation.

Customer wants to be able to ‘push to test’ the level switch circuit at the tank, to mechanically check the operation daily.

We mainly use small optical level sensors, which have proven more reliable than the float switches used in past. Using two or three, optical sensors in a ‘voting’ type circuit is not acceptable to customer. Fluid may be petroleum oil or water glycol.

Proposals have included:
1. mechanical system that pushes down on the submerged float
2. mounting method to rotate the switch 180 degrees in the tank sidewall so float goes upward and trips the circuit

Anyone know of a float switch with built in rod or shaft that could mechanically move the float?

kcj

 

[budt]

Kevin;

Could you mount the switch on an adjustable base that was shifted manually or with an Air or Hydraulic Cylinder. The switch base connection would only have to move enough to make sure the switch was still able to make or break contacts.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.

http://www.fluidpower1.us

 

[jbthiel]

I have not seen such a switch. The closest I have seen is the float type with externally adjustable contacts sold by Murphy. I liked these because I could fine tune the trip point so that a failure would only result in a little bit of oil loss.

To further elaborate on Bud's idea, I would make it as fail safe as possible.
-make sure it can't be held in the up position
-if something breaks in the mechanism, the switch is at the correct height but not too low.
-If the switch moves, I would be worried about the wiring flexing over time. Obviously you want an open to trip the shutdown, but maybe also consider low voltage in case of a short?