1/4" Plastic Normally Open Solenoid Valve

[cpretty]

Hi all,

This is a little different to many of the valves discussed here, but I am sure someone has had experience with these.

I require a 1/4" BSP female plastic solenoid valve. It needs to be 12vDC, and to have minimal exposed metal (preferably none as the marine environment will kill it quickly). The challenging part is it must be NORMALLY OPEN. It must also be cheap (<8USD - purchasing 200 PA).

It is vital to be normally open as if power is removed, there is a risk of sinking the vessel.

I have spent a large amount of time on google searching for these to minimal success. I have found a single valve that is adequate (R.P.E srl, Italy), but the price is a little high.

The most common applications for these is irrigation, coffee machines, home appliances etc, but a lot of these are not designed for exposed operation.

Does any one else have any thoughts on where they have seen something similar?

Thanks in advance,
Craig

 

[roydm]

You say the valve must be Normally Open yet everything else you say points to Normally closed i.e. close on power failure.
Cole Palmer

http://www.colepalmer.ca

have several different options for 12 VDC in plastic, perhaps one of the types that simply pinch a length of tubing (no potential leak path). The price may be too high though as they start around $70 ea.
Are each of the valves operating independent of others, if not perhaps you could fabricate something to pinch multiple tubes.
Send me a bit more infofmation on what you are trying to do, I might be able to suggest something.
roy_matson at yahoo dot ca

 

[gerhardl]

Hello,

try for instance the European company Gemue in Germany:

http://www.gemue.de/download/db/gb/db_52_102_202_gb.pdf

Which have a wide varity of plastic valves for high-quality use. For seagoing vessel, UL certification is mentioned as available, and I think NO should be no problem.

There is a but: at 200pcs a year and qualified with certification for 'not sinking a vessel' you will have to accept a higher price than your target. (Quality has something to do with price)

Sirai (SRL), which you already found,

http://www.sirai.com/inglese/home.html

is normally cheaper than Gemüe.

You do not mention fluid (air, gas, water?) flow and pressure required.

1/4" is only the connection, a solenoid valve this size connection could have a nominal opening inside from 0,6 mm up to 5mm!

Another option would be to check if any supplier could offer SS or Gunmetal or equal material compatible with environment at a cheaper price than plastic. In this case you could check out:

http://www.buschjost.com/BE_MH_16P_1.cfm

Also check out if your valve will require any certification from UL, Veritas, DNV or other institute certifying vessels.

Good luck!

 

[cpretty]

Thankyou very much for all your help.

roydm - yes, the examples are normally closed, but all I was refering to was style. $70 is significantly above my price range. I will look into pinch valves, but haven't had much success with them for low cost operations in the past.

gerhardl - thanks for all the suggestions. They are excellent resource, and are exactly the type of response I was after. My search obviously did not include the terms that would get me to those suppliers, hence this question. I am looking into them as options.

In terms of my design criteria (which I kept brief so no-one got bogged down on details);

The design is for a vent to atmosphere to break a syphon on a marine vessel.

Medium is atmospheric air, but must handle salt-laden air, salt spray, and salt water, and associated buildup with this type of environment.

Pressure is -10psi to 300psi (valve must withstand not operate). Operation is at ambient pressure.

Flowrate is <10 lpm.

I am not interested in metal valves (even though they are capable of doing the job), as we are a plastic fitting manufacturer extolling the virtues of non-metallic fittings. It would be unwise from a marketing point of view to say 'but in same cases it is ok'.

I am happy with regards to meeting certification requirements, and take UL as a nice to have but not required. DNV/Lloyds certification is not required.

Cheers,
Craig

 

[moltenmetal]

I'm unaware of ANY solenoid valve of any consequence which will cost you < $8 USD in quantities of only a couple hundred per year, much less one with a hermetically sealed coil!

The cheapest ones I've seen are the ones by Eaton, used in mass-market quantities for washing machines and dishwashers. Can they make you a special with a 12VDC coil? Maybe, but not for your price. And these solenoids are anything but hermetically sealed.

You've over-specified the problem. Either you can spend more or you can't have your specs.

 

[cpretty]

moltenmetal,

I am aware that it may be a challenge, hence why I have asked the question, as there is often a company that surprises.

I have found 2 valves at the $12-$13 range from very small suppliers, so was putting the question out to try and find a larger volume supplier that has this as a standard product, and therfore the ability to offer a cheaper price.

I may find that I am not able to acheive my goal, but it is worh trying.

 

[gerhardl]

A technical warning: a pity you have to be careful about your full application here, but salt water, salt sprey and air in combination handeled directly by a solenoid valve is an unfortunate combination. Even if innards are fully protected and sealed, salt crust can form and damage your operation.

I would advice you to have a look into miniature diaphragm valves in all plastics (does exist-check the sites above) air operated over air solenoid valves, and protected by checkvalves to avoid seawater coming in the wrong way

This will probably be m more troublefree and have a longer maintenance free lifetime, but the combination will burst your small bag of money.....

 

[roydm]

Graig,
You never answered my question about the number i.e do you just have one valve per site or multiple valves all together.
Since you are a plastic fitting manufacturer it would be easy for you to make a multiport valve that you could actuate with a small motorized actuator or if you have a source of air, a diaphragm actuator. A 20 port actuated valve should be cheaper than 20 individual units.
Another option instead of solenoid to atmosphere might be to blow air in at the high point thus breaking the syphon that way.
Roy

 

[cpretty]

roydm

One valve per site. No air available.

I have debated using our skills to build a valve ourselves, but as you can imagine, payback on ivestment will be low, as will the time involved in research and development to come to a adequate solution.

After more investigation into valve design, I have now found a further constraint (as if it wasn't tight enough). The valve has to work with small differential pressure. This rules out most of the simple diagphram valves as they rely on the pressure of the fluid to energise the seal.

From what I can see, I may have found one of the only viable options. It is a NO valve with sealed piston, pushing directly onto orifice. It will need an adapter.

http://www.rpesrl.it/prodotti/irrigazione.php

Pricing is a little high, but as identified by moltenmetal, realistic.

Thanks for all you help everybody.

 

[roydm]

That type of valve (the black ones anyway)is known as a pilot operated. The solenoid opens a small orifice connected to line pressure. You need to be careful in selecting this type, they usually require a few psi to operate.
Assuming you connect the discharge of the valve to your syphon, the inlet will be at atmospheric you willl have a differential pressure equivalent to the height of your syphon. I can see it working once the syphon is established but I'm not sure you will be able to get it to close again once the syphon is broken and you no longer have a differential.

The small ones look to be direct acting, they might work. I would be surprised if the metal parts are not in touch with the process fluid. As a general rule the higher the pressure the smaller the orifice.
Anyway
Good luck
Roy

 

[gerhardl]

My warning for seawater and inner, possible encrustion still stand. What about electrically operated diaphragm valves? Exists, but high priced!