zero leakage cartridge type high speed 2-2 way solenoid valve

[siavash1111]

I am looking for a zero leakage 2/2 way solenoid valve(cartridge type ).I could not find any suitable products.Does anyone have experience in this case? If so , please address
My requirements :

15 Lit/Min @ 100 bar pressure

Oil type :10 CST mineral oil

 

[Oldhydroman]

Lots of companies make seated type solenoid valves but few will actually call them "zero leakage". My experience is that in most applications the valves are effectively zero leakage (as far as is practible) but many manufacturers won't commit to that because too many things are outside their control and they don't want perfectly good valves being returned under warranty.

The problem is that hydraulic oil forms a tenacious film between metal surfaces being pushed together (good! - we rely on that property for lubrication) but the insides of the "zero leakage" valves sometimes struggle to cut through this film to get a true metal-metal contact between the poppet and the seat. There can actually be a microscopic flow through this film and eventually a drop will form on the outlet of the "closed" valve. The time taken for the drop to appear will depend on the pressure and viscosity of the fluid, the cleanliness of the fluid and the age of the valve. A brand new valve might not perform as well as one which has run in a bit; allowing the poppet and the seat to become matched to each other and all the microscopic machining markes to become polished out. An old valve might not close as well because it has accumulated years of damage across the poppet/seat interface - especially if there are some erosion or cavitation issues occurring if the valve is opened with a high differential pressure across the seat.

You might want to look at the products from Hawe (google Hawe D74901). Hawe are brave enough to describe their valves as zero leakage. Other manufacturers, such as Sun Hydraulics, mention figures like 0.6 cc/min. Some manufacturers cleverly skirt around the issue.

So you need to decide what "zero leakage" actually means to you. The same goes for "high speed": a direct operated valve might switch in 50 milliseconds but a pilot operated valve would need 150 milliseconds. Sometimes the opening times and closing times are different and/or pressure dependant.

If that's too slow you could investigate using a power reducing solenoid plug on a half voltage solenoid (Google Wandfluh 1_1_320_e). By initially overenergising the solenoid the output force is increased and the acceleration of the valve's moving parts is much greater. So, for example, you use a 12 VDC solenoid on a 24 VDC supply. The special solenoid plug (P03) reduces the solenoid voltage to 50% after about 1/3 of a second and this stops the solenoid burning out.

DOL

 

[siavash1111]

I understand that If the leakage be near zero(less than 10 drops per minute) , some manufacturer refer them as zero leakage valve but I am looking for bubble tight valve (no leakage).
In your experience is there something can meet my requirement ?
Can you tell me if the pressure increases in a poppet solenoid valve what would be the figure of internal leakage. For example a 2 position ,2 way solenoid valve have 5 drop/min internal leakage at 350 bar(max working pressure ) if we decrease the working pressure to 100 or 50 bar how many leakage will appear at system ? the rate of leakage will increase or decrease ?
Thanks

 

[Oldhydroman]

You really need to ask each manufacturer if they are redefining "zero leakage" as "only leaks a bit". You could also veer towards a gas service valve that can also cope with low viscosity fluids rather than a hydraulic valve. Try valves from "Circle Seal Controls".

To get a bubble tight closure you probably need a valve with a soft seat - then, as the pressure increases, the poppet is pushed harder into the seat and the seat material conforms even more exactly to the contours and machining marks of the poppet.

With a metal-metal seat there is no real answer to the question. As the pressure increases it becomes a race between the increasing flow rate through whatever gap remains and the reduction of that gap as the closing force increases. If you have a pressure balanced construction then the closing force will not increase with pressure so I would expect the residual leakage rate to increase with pressure.

DOL