hi, this post (as well as my other posts) all relate to one project, and whilst the parts are coming together i seem to have hit yet another hurdle, but this one is really specific!

on my quest, i require a way of dispensing 25ml of liquid (1 bar, water density), in approximately half a second.

also, i don't have a never ending budget, so i have scoured high and low for low cost, but good products. i came across a 2 way (not required to be 2 way, but better pricing than 1 way, and it won't cause an issue) solenoid valve from Invensys (RS Component 342-023) and at £13 is a bargain (seeing as the usual price for these items seems to be £80-£150+

now, the specs say;

Diaphragm operated, normally closed solenoid valves for controlling water at a minimum pressure of 0.2 bar
Coil can be located in any one of eight positions
Maximum flow rate: 0.25 to 17 litres per minute
0.2 to 10 bar pressure range
Power consumption: 4W
Nylon 6 body with 1/2 in. BSP ports (may be base mounted)
1/4 in. spade coil terminals

my issue / query is that although im chucking 12vdc through this thing, it doesn't flow more than the absolute minimum, and the item only has 2 contacts and no adjustable parts.

is this an amp issue? more current, more flow? has anyone worked with these (or similar items) before?

thanks

 

Well, it seems that the valve's ratings cover gases. I would think that the 17 litres per minute rating would be a gas at 10 bar pressure (~145 PSI). Since you are attempting to dispense water (far more viscous than a gas) at 1 bar/~14.5 PSI, I would expect considerably less than 1.7 litres per minute flow.

If the part that you are using is indeed rated for operation at 12VDC, it would require being powered by a supply capable of outputting >= 12v @ 334mA.

When you energize the solenoid, do you measure 12v across the solenoids' terminals? If so, then your supply is adequate, and increasing the current/VA rating of your supply will not help improve performance.

If you can increase the pressure of the vessel containing the water, it will decrease the time required to dispense the water roughly proportionately. If you are filling an open container such as a cup, the valve will likely act as a nozzle, causing a high-pressure fast-moving stream of water that will splash all over, or possibly even blast through the bottom of a fragile container. You would then need a method to slow the stream back down.

 

i get your point, but the specs do specify for water, and not a mention of gases

I would expect considerably less than 1.7 litres per minute flow.

which at this rate is 28ml per second... or less, sure, but i'm currently getting about 1 drip per minute! its like the solenoid isn't fully opening.

 

i get your point, but the specs do specify for water, and not a mention of gases...

In the technical specifications, under "Medium/Temperature", water and air @ 90°C maximum are mentioned. Air qualifies as a combination of gases; I really should have been more specific and said "air" instead - even though the gases present in air can vary considerably from one location to another.

...which at this rate is 28ml per second... or less, sure, but i'm currently getting about 1 drip per minute! its like the solenoid isn't fully opening.

I'm not certain as to the actual type of valve in that unit. It may be a poppet-type, which would need to be installed with pressure in a specific direction.

Actually, this is silly of me - but I didn't notice before that the brand name in the "Technical Specification and Drawings" .pdf document is "Hydralectric", not "Invensys" - but they show an Invensys part on the RS page, even though the manufacturer is listed as Hydralectric. Also, the Invensys part shown is a 1-way valve, not 2-way.

Hydralectrics' page for solenoid valves is here:
http://www.hydralectric.com/category/5-Solenoid+Valves

I could not find the proper page for Invensys valves; their site led me on a wild goose chase where I kept coming up with nothing.

RS components needs to get their web page updated for that part, and supply the proper documentation for it. Right now, I can't tell if the documentation provided matches the part shown in the photo; but since the brand names are not the same, I'll have to say that they don't. There are no part numbers in the documentation that match. Since the part numbers don't match, there is no way to tell if the information in the tech specs is representative of the valve you have.

 

yeah, that led me around too.

i did find http://www.invensyscontrolseurope.com/applianceproduct.aspx?id=1543 but it seems to be the same product, but manufactured by different people, although the above link has descriptions like; available in 110v, 240v, 12v and 24v models etc, like an overview

but the techs were similar.

and i get the water / gas / air thing, but even blowing through this thing (technical i know) 17 litres per minute doesnt even seem feasible... its like blowing through a straw thats been bent!

 

yeah, that led me around too.

i did find http://www.invensyscontrolseurope.com/applianceproduct.aspx?id=1543 but it seems to be the same product, but manufactured by different people, although the above link has descriptions like; available in 110v, 240v, 12v and 24v models etc, like an overview

but the techs were similar.

I don't think that it is very reasonable of RS Components to expect people to be satisfied with items where the specifications are so ill-defined.

You might try contacting the manufacturer directly if you do not/cannot get satisfaction through RS Components.

and i get the water / gas / air thing, but even blowing through this thing (technical i know) 17 litres per minute doesnt even seem feasible... its like blowing through a straw thats been bent!

I understand your dilemma.
On this page:
http://www.hydralectric.com/product/Solenoid+Valves/1477-1+Way+Water+Valve+180+Degree
there is another datasheet:
http://www.hydralectric.com/downloads/696/solenoid_valves_001.pdf
where you STILL cannot determine by part number what options are actually present in the valve that you have. While the flow MIGHT be up to 17L/min IF the pressure is 10 bar for air, you may also have restrictions in the valve as shown in this datasheet.

There are two UK tele#'s and an E-mail address in that datasheet on the bottom of each page - you might at least ask them if Hydralectric is using Invensys as a supplier for these valves.

 

ok, so just to finalise really.

invensys are a hugely gigantic company, and hydrelectric is a kind of subsidiary company.

the valve ive purchased should have an orifice (internal opening) of 4mm, creating an output that should be (with liquid at 0bar) 7.2 litres per minute.

and with the output i'm getting it seems that the valve is faulty and they are going to investigate and replace!

anyway, thanks for your help!