Solenoid Valves, fluid through Nozzle - not closing

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Discussion Overview

The discussion revolves around the operation of a solenoid valve used in a system to spray kerosene. Participants explore the issue of the valve not closing properly after the initial use, particularly when air is present in the line between the pressure vessel and the solenoid input. The focus includes technical explanations and potential solutions related to fluid dynamics and valve operation.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the setup involving kerosene pressurized to 160psi and a solenoid valve with a specific orifice size, noting that the valve fails to close properly after the first use due to air in the line.
  • Another participant suggests that the air in the pilot-operated solenoid valve's chamber must be flushed out with liquid for proper operation.
  • A participant questions why air behaves differently than liquid in this context, speculating that the compressibility of air may be a factor.
  • There is a suggestion to consider using a direct acting solenoid valve or to contact the manufacturer for recommendations if the current setup does not work.

Areas of Agreement / Disagreement

Participants generally agree that the presence of air in the system affects the operation of the solenoid valve, but there is no consensus on the best solution or the specifics of why air behaves differently than liquid in this scenario.

Contextual Notes

Participants express uncertainty about the behavior of air in the solenoid valve's chamber and whether it is typical for air to enter the system under normal operating conditions.

mjl1982
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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 anyone 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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Pilot operated SV's have a chamber that will be filled with air until they're operated or flushed out with the liquid. Sounds like that's what's happening. The air has to be flushed out of that chamber first.
 
Thanks for the quick reply.

Why doesn't the air work like the liquid does? Is it because it compresses?

Also can you recommend a type of solenoid valve that would work? I believe pilot operated is most common for the dimensions and pressures I'm working with.

Thanks

Mat
 
mjl1982 said:
Why doesn't the air work like the liquid does? Is it because it compresses?
That's probably what's going on. Why not just keep it filled with liquid? Does it get air in it under normal circumstances?

If it doesn't work for you, you can go with a direct acting SV or contact the mfg for recommendations.
 

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