Testing methods for float-type liquid level switches

[ScottAO]

Hello all,

Was wondering if anyone could share their inspection practices for mechanical float-type liquid level switches.

We have some tanks fitted with a chain that can be used to pull the float up and test the signal, but there are concerns that the mechanical linkage may not go back to the proper position; also concern that if the float itself had a hole or crack, the liquid would fill it up and it wouldn't float.

We have discussed 'wet testing' by removing the entire assembly and floating in a pail of product to ensure it displaces, but that is a pain and safety concerns about doing this on top of a tank.

Primary concern is for liquid petroluem vertical storage tank applications.

Any thoughts / ideas / best practices out there? Thanks,

 

[JLSeagull]

Most companies avoid mounting internal float level switches on a vessel. If you use a bridle you can block the vessel then vent and fill the bridle to test the increasing level and drain to test the decreasing level.

 

[DRWeig]

Do what JLSeagull said.

Also, considering the very low cost of float switches, put in as many redundant ones as you think you need to feel comfortable -- depending on how critical the process is.

Good on ya,

Goober Dave

 

[roydm]

Please give us the make & model of the switch.
Are you sure it's a float, not a displacer?
Roy