Corroded RTD terminal board points (large motor in outdoor salty environment). 4

[electricpete]

On our large motors we have (like most) 6 stator RTD’s but we only connect one to our plant computer system. We periodically check to find the hottest one and leave it connected to the computer.

We have frequent problems with erratic indicated winding temperatures creeping up. Often when we investigate the problem is resolved by lifting and relanding the leads (suggesting a problem with corrosion is affecting the connection resistance).

Attached is one of the terminal strips which has found to have more severe corrosion than most. Certainly the screw heads are severely corroded on this one. I'm not sure what else is corroded. I'm reasonably sure we have the same problem (winding temperature creeping up and solved by lifting/landing leads) on other motor terminal strips that don’t look nearly as bad as this one.

For this particular terminal strip, we have a motor refurbishment coming up shortly, I’m going to replace the terminal strip and replace the RTD lugs (with ring lugs).

My question: Are there any practices to help prevent the corrosion (something that could be done during our periodic check).
Is there some type of compound that could be applied before or after tightening the terminations to help improve the resistance of the connection to being disrupted by corrosion?

PS. I'm not looking to install a heater (too much effort). I might be open to changing terminal screws or strips if there is a better choice someone can recommend.

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(2B)+(2B)' ?

 

[edison123]

Replace with brass/SS stud terminal boards?

Muthu

http://www.edison.co.in

 

[Gr8blu]

electricpete: First - monitoring just "the hot one" and switching between phases periodically is not the best long-term preventive maintenance practice. Several things can cause a phase to get hot - that might not affect another phase to the same degree (no pun intended). Second - simply changing from the terminal type shown to a positive lock (ring type) termination is not going to alleviate the root problem, which is corrosion resulting in a high-resistance joint. Third - using less-corrosive hardware (brass or stainless) is going to improve the situation by limiting the corrosion on the hardware itself but might not fix it entirely as the terminal itself might be part of the trouble. Fourth - verify that all cable entry locations are properly sealed for the conditions. This might mean having to add grommets or some form of a non-conductive gland plate to prevent moisture ingress.

Converting energy to motion for more than half a century

 

[TugboatEng]

I would recommend replacing the entire terminal strip. McMaster has CAD drawings so you can find one with the same mounting dimension so you don't have to do any drilling.

I suggest replacing the strip because the spade terminals left the copper bar on the strip open for corrosion.

Replace with ring terminals to form a more environmentally tight connection.

Make sure your terminal strip comes with phillips headed screws. It makes plugging ring terminals much easier.

I would suggest installing a rotary switch to save wear and tear on the connectors.

Lots of options for battery powered RTD transmitters. I see one with 10 year battery life.

 

[TugboatEng]

Because designing stacked rotary switches is challenging, there are off the shelf solutions for this application.

https://www.labfacility.com/tempera...100-thermocouple-panel-selector-switches.html

 

[FacEngrPE]

Sometimes water accumulates in conduits, and provides a continuous source of moisture, If you have this problem, install drains at the low points in your nearby conduits. A more complete discussion of the subject ->

https://forums.mikeholt.com/threads/conduit-drains.49701/