anyone working with limit switch exposed to sea? 3

[bboosstteerr]

Hi,

Anyone have experience which brand/type for limit switch that is durable working in harsh condition (i.e corrosion) especially near sea. Thank you

 

[roydm]

I would use a switch with no exposed moving parts
Some sort of proximity switch, reed switch, GO switch
Perhaps non metallic housing with a potted cable.
Low Voltage 24V rather than 110 AC

Perhaps share more details like what for?
To a control system or operate load directly?

 

[bboosstteerr]

This limit switch used for ship unloader of coal, its for control system.

 

[roydm]

I haven't worked on a ship un-loader but for many years worked in mining with conveyors, diversion chutes, trippers and the like.
We gave up on mechanically actuated switches early on, (they were too easily damaged) for a magnetic proximity switch by Go, these had moving contacts inside actuated by distorting the magmetic field, I don't even know if these are still manufactured.
These days I would use an inductive proximity switch.
You have to be a bit careful selecting proximity switches for a PLC input, most draw too much quiecent current and turn the input on permanently

A typical use is conveyor underspeed, simple targets on the tail-pulley actuate a switch, the PLC has a pair of timers for NO & NC, if one times out the conveyor is not moving, failsafe.
Unlike mechanical switches a proximity should never wear out.

 

[HCBFlash]

I've used plenty. You need to have a NEMA 4x rated device, for conventional limit switches I've mostly used Allen Bradley, Banner, and Square D on stuff I've built myself,but there's lots of different stuff out there. Availability is always an issue, and in the USA those 3 always have had good availability. It's been a couple of years now since I did much specification or purchasing, and Schneider may have shuffled things a bit, but I was always a fan of Square D products, as I felt their quality matched or exceeded Rockwell, and I felt their design features to be better. I've used Go also, and it performed fine. Nonmetallic bodies have advantages in highly corrosive environments, but powder coated or alloy bodies also do well if the design accommodates them.

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(Me,,,wrong? ...aw, just fine-tuning my sarcasm!)

 

[ScottyUK]

Watch for aluminium bodies with stainless steel screws in marine environments. The screws tend to seize into the aluminium to the point where they shear off rather than come loose. Anti-seize paste sometimes can help, but is more effective on screws larger than you find on limit switches.

 

[bboosstteerr]

wow thank you sir for the information i'll look into it.