Looking for a mine-duty on/off air valve

[gregorybosma]

Hello everyone!

I'm having trouble with a cleanout nozzle on some mining equipment-- the solenoid valve for this nozzle sticks open. The air going into this nozzle has a lot of dust/water, which prevents the diaphragm from sealing properly.

I've considered filtering this air, but get backlash on that idea because it's high flow (200-300 cfm air), there's not much room on the machine to mount such a large filter, and it would be an additional maintenance item. Instead, I'm looking for something maintenance-free by trying to find a replacement on/off valve that can handle dust and water.

I've been looking for a replacement on/off valve that can handle the high amount of dust, but haven't had any luck. I've only found electric ball valves that have too slow of actuation time, and dust collector valves that require pilot air pressure to open (it'd be difficult to maintain pilot pressure while running a cleanout nozzle).

Is there a specific on/off valve that would fit this application?

 

[srini1785]

I would start by looking at the material of the diaphragm. NBR is not suitable for abrasive air, the other suitors are EPDM and FKM/FKP. There's only so much you can do with a valve. The best method is to filter the air itself. If not on the machine, at least on the header line feeding the valve.

 

[gregorybosma]

Good call on diaphragm material! It is currently NBR. I'm not sure if switching material would fix the issue though, since the current workaround is to wipe down the diaphragm then reassemble the valve whenever it sticks open. The valve works fine after wipedown, until another layer of dust covers the diaphragm and prevents it from seating again.

Would switching to EPDM or FKM provide any benefits besides wear resistance?

 

[srini1785]

Changing diaphragm material is worth a try. If sealing is the problem then the other option that I can think of is a Piston operated angle seat valve. Some valves from Boschjost (82380/ 84500) *CLAIM* to have good resistance against aggressive and contaminated gases. For the sake of full disclosure, I have not used them in an actual mining application.

However, I still feel that a filter (50Micron) in the header line or a in-line high flow filter would be a better option.

 

[TugboatEng]

What diameter piping are you talking? If you have dirty air you need to avoid pilot operated valves. Magnatrol makes a line of direct actuated valves that should resist clogging.

https://www.magnatrol.com/overview.cfm

 

[gregorybosma]

This is a 1.25" air line. To actuate the valve, we have a 24VDC system, mine air (with dust), or hydraulics (4400 psi load sense system). Filtration is starting to sound more appealing as I'm proving how difficult it is to find a contamination-resistant valve fit for this application.

Magnatrol looks like they have the exact direct-acting valves I'm looking for with their type "D". I'm curious how they're able to get away with a direct-acting solenoid, when a long search shows most other manufacturers depend on some internal pilot mechanism... EDIT: Figured out how they get away with direct-acting on their type "D" valve. Max differential pressure is 2.3 psi, so the valve won't open if inlet pressure is up to 120 psi while the valve is shut. They claim type "D" is good for low pressure, low flow only.

EDIT: Magnatrol also has a valve they claim is good for "gritty coolant." Looking into that now. It has an internal pilot system similar to our current valve which sticks, but the name suggests this internal pilot system is a bit more forgiving to small particles.

 

[TugboatEng]

They're huge, noisy, and have high power consumption. They're a relic of the "they don't build things like they used to" era.