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mlepyro
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Join Date: Apr 2010
Posts: 3

Solenoid Valve Behind a Nozzle - Problem Closing

04/27/2010 2:43 PM

Hello

I have a problem that I can't understand...

I am putting kerosene pressurised to 160psi through a 1/4" BSP solenoid with 13mm orifice.

On the out port of the solenoid is a 1/4" BSP to 2mm ID nozzle.

The idea is it sprays out a stream of kerosene.

The kerosene is provided by a pressure vessel that is charged with nitrogen. The outlet going to the solenoid is at the bottom, the inlet from the N2 is at the top.

This works fine, except the first time it is used after charging the vessel with fuel and N2 gas. In this situation there is N2/air in the line between the vessel and the solenoid input. On pressurising and opening the solenoid valve first gas comes out, then fuel. The fuel fires out and won't turn off. It takes a random time up to a few seconds to stop after removing power to the coil.

Energising the coil immediately afterwards results in normal operation.

I can then repeat the problem by turning the vessel upside down and clearing the solenoid line of fuel. Reverting the vessel to the correct orientation and opening the solenoid again results in the same problem as above.

Does any one have any idea what is going on! I can't see how it's failing on the first opening.

The solenoids are pilot style... so I wonder if the air coming through is causing problems pushing down on the plunger?

Thanks

Mat
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peterg7lyq
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#1

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/27/2010 3:39 PM

is the return spring in the solenoid strong enough to hold the presure because thats what it sounds like

also is it posible the gas that comes out first is freezing the solenoid open ?

these are the two possible effects given the info you have supplied.

does the valve work ok without any gas or high presure kerosene ?
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JohnDG
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#2

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/27/2010 5:37 PM

Is the solenoid valve rated for both gasses and liquids? And in admixture (bubbly liquid)? If it's piloted, you may have a state where the pilot, filled with nitrogen (compressible), is trying to move the shuttle to stop the flow of the incompressible kerosene.

Check the datasheet, and if in doubt, check with the manufacturer.

Just an idea.

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LG_Dave
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#3
In reply to #2

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 12:03 AM

That would explain the time delay - the pilot clearing of gas.

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Lou M
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#4

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 8:41 AM

That is exactly your problem, never use a pilot style solenoid on anything other then air! Also the kerosene will have adverse effects on the diaphragm and other sealing parts. Use a positive shutoff type safety valve rated for combustible liquids like kerosene. Be Safe, Lou
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Vanam
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#5

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 10:01 AM

Is the vessel completely emptied before refilling? what about the volume between solenoid valve and nozzle? is it possible to refill with certain kerosene in it. N2 may be entrapped in valve or before nozzle of 2mm.
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mlepyro
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#6
In reply to #5

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 10:09 AM

Thanks for the replies all.

The tank is empty yeah. We can recreate the problem by not emptying the tank, but inverting it and purging the solenoid pipeline. Then turning the tank back to ensure keresene is pushed through.

I am having a problem finding a valve that is direct operated and able to cope with 160psi with large throughput (e.g. not 2mm orrifice).

Thanks

Mat
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Anonymous Poster
#8
In reply to #6

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 5:33 PM

try REDHAT (ASCO) solenoids
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mlepyro
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Posts: 3
#7

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 10:47 AM

Just a thought...

If I charge the system, and open the solenoid valve... first time it sticks open most times. 2nd time fine, 3rd time fine... xth time fine. If I continue until it runs out of fluid and starts to just discharge N2 gas - it also works fine. So in this way there is air in the system/pipes/solenoid, but it works fine.

Why doesn't it fail in this situation?

Thanks

Mat
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JohnDG
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#9
In reply to #7

Re: Solenoid Valve Behind a Nozzle - Problem Closing

04/28/2010 5:58 PM

Because you have nitrogen (compressible) in the pilot line and the spool is trying to close the valve against nitrogen (compressible), rather than an incompressible fluid.

<Whacks forehead with the paddy bits of a borrowed furry paw...>

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Anonymous Poster (1); JohnDG (2); LG_Dave (1); Lou M (1); mlepyro (2); peterg7lyq (1); Vanam (1)

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