Recommend: Waterproof Prox?

K7JLJ · Dec 28, 2018

We have an area at work where the humidity and caustic water is breaking down our 18mm proxes and shocking people.

We currently use: AB 871C 2-wire AC Plastic Barrel Tubular Sensors

Can anyone recommend a better solution that is 120vac 2 wire?

Thanks.

mendonsy · Dec 28, 2018

The Omron E2E2 series is stainless and rated IP67 and 1200 psi washdown.

K7JLJ · Dec 28, 2018

Thanks mendonsy,

The ABs are IP67 also, but I think you need IP69K to get the 1200 PSI rating.

The water is about 290F and I'm thinking the only option might be to switch to the food grade stainless tubes so at least if they should ground out to their case it will take a path to the platform instead of being insulated in the mount.

James Mcquade · Dec 28, 2018

the ip rating is only part of the equation.
you need a nema rating - 4x - corrosive rating if I remember correctly.

next, what is the acid in the water?

then you go to AB, Omron, peperal fuchs and tell them what the application is and the caustic substance to see what stainless material you need.

is this a food industry? stainless steel 316

you select a prox switch based on the caustic material.

now for the bigger issue.
you should consider switching to 24 volt sensors if possible before someone gets seriously hurt. may not be practical to do, but you need to plan for something.

james

K7JLJ · Dec 28, 2018

Normal ph is 5-6 it at the head box of a Fournier paper machine. Periodic clean outd raise the ph much higher but I do not know how much.

24vdc is not practical in this case and it's only two proxies in the area.

5618 · Dec 29, 2018

Look into the Allen Bradley stainless barrel 2 wire 871TM line. We use 871TM-BX21-N3 extensively with 120VAC in a food manufacturing caustic washdown environment and haven’t experienced shocking. I have seen shocking from plastic barrel proxes from at least two other manufacturers.

Edit: I just looked at the AB website. These might be discontinued next year, something about DeviceNet. I hope it's just the DN version being dropped. They’ve been excellent sensors. There’s apparently 2 wire all stainless in the 871T line we might have to try someday. Otherwise, consider also Turck. We found a higher temp rated Turck for one application but haven’t tried it. Reworking some heat shields has gotten the AB prox close enough to ratings to last.

rupej · Dec 29, 2018

IFM has a great line of washdown and SS proxes. Some specific for food & bev industry that are corrosion resistant.

K7JLJ · Dec 29, 2018

Thanks guys for the help, I will try the AB prox @5618 suggested.

AB is the preferred manufacturer for the plant so will go that route first.

seth350 · Dec 29, 2018

++1 on swapping to 24VDC, nasty things can happen with water and AC.
Someone really needs to come out with a line of devices that work in harmony with chemicals.
Even food grade stuff isn’t all that great. In our world, the sensors last but the cables literally melt away, same with enclosure gaskets. That occurs with only the off-gassing of the acids.

sparkie · Dec 30, 2018

You might check out Keyence. Quite pricey, but really tough stuff.

K7JLJ · Dec 30, 2018

I don't suppose anyone makes a 24vdc prox to 120vac setup?

I have a JIC within 6ft that I could put some kind of base unit in to feed 120vac back to the PLC if such a "base unit" would feed 24vdc to the prox?

A drop relay is not the answer and the run can only be done on an outage with much "ringing of hands" so the policy is "don't touch 120vac proxes when you are in a shower".

K7JLJ · Dec 30, 2018

Side note... for those that use proxes in the washdown areas, do you have issues with a QD connection or do they work as well as straight corded proxes?

rupej · Dec 30, 2018

IFM's has QDR cords made for washdown. They have an o-ring to seal, are SS, and have a built-in torque limiter so they don't get overtightened. Never had a problem with those.

K7JLJ · Dec 30, 2018

Good info @rupej looking into it, thanks!

5618 · Dec 30, 2018

A quick count in my head, we use at least 45 of these with QD. We use Allen Bradley and Brad Harrison cables. PVC jacket works fine for us but TPE might be worthwhile for some environments.

We don’t have problems with water infiltration but coupling nut material can be a problem. We grease the threads of these and just about everything. Epoxy coated zinc does very well unless the epoxy gets damaged. Stainless is fine but there’s a risk of galling if not greased. Plastic can be stripped by pliers people who know tighter is better. Brass or aluminum would corrode for us.

This might give you a reference: Washdown uses 70 psi Strahman and 600 psi wands. Alkali cleaners are applied with hand pump sprayers or foaming hoses.

Recommend: Waterproof Prox?

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