Back Pressure Valve, Pressure Maintaining Valve Europe?

[HeXx]

I thought about buying that valve but its not suitable for a pressure sustaining valve as the output pressure affects the spring force on the valve.
What I bought and am still to test is this sequence valve:
Sequence Valve VSQAPP - Hydraulic Valves for Fluid Control and Regulation Válvulas de Sequência 3/8" - V0642

 

[Agro]

Oleodinamica Marchesini VMP14L80300 tuned to hiss at 150 bar.

Druckbegrenzungsventil VMP-14-L-80/300 | STASTO Automation

www.stasto.eu

OMG they are very bulky.

And are they airtight indeed? Not leaking?

 

[Dave1w]

What compressor / filter do you have that you are adding a PMV to? It may not be too difficult for someone travelling from the UK to hand carry then post while in the EU?

 

[HeXx]

I'm currently making a DIY compressor from a young heng clone with fully automatic purges.
The pmv will be right after the end stages of filters and water separators.
I'm not interested in a fast compressor. In order to keep the compressor as cold as possible I expect to run 4, 10 min cycles with 5 min break between them to get a 0 to 240 bar 15l cylinder.

 

[HeXx]

If any one is interested, here are some pics of the first setup.
No filtration system yet.
Air in this tank is only for testing purposes.
I modded an input muffler to noise it down a bit and added cooling to the output pipes of both stages.

 

[Gone for diving]

Oh dear now everyone is going to comment and you are going to die.

 

[HeXx]

Oh dear now everyone is going to comment and you are going to die.

It's fine.
That's why I said not for breathing air yet.
I expect that after I get a full filtration system working I will get an ok after sending sample air for analysis.

 

[CG43]

Hello

An interesting project !
Since the compressor has only two stages, I would improve the intermediate cooling even further.
The air at the entrance of the second stage should not be much above ambient temperature.
With a very heat-resistant compressor oil and breaks, this could possibly work.
You should monitor the air temperature at the exit of the second stage .
On the net there are videos with sooted second stages .

 

[HeXx]

Hello

An interesting project !
Since the compressor has only two stages, I would improve the intermediate cooling even further.
The air at the entrance of the second stage should not be much above ambient temperature.
With a very heat-resistant compressor oil and breaks, this could possibly work.
You should monitor the air temperature at the exit of the second stage .
On the net there are videos with sooted second stages .

I'm doing a simple cooling on both output stages with a copper pipe soldered to the output stages and running water trough it.
The air reaching the tank is a little above ambient.
This is just a first test. I m still to buy a filtration system.
I'm using food grade oil with a flash point of 270°C.
I expect to fill in very short runs with long stops in between. Temperature of the first stage never to exceed 60 degrees. Second stage is always lower temp than the first.

 

[CG43]

Hello HeXx

The temperatures you measure are not the air temperatures in the compressor cylinders.
The air temperatures in the cylinder are decisive whether oil is burned or not .
They can be calculated quickly and easily with low accuracy requirements.
Fast-acting compressors are calculated as isentropic compression
and as a material value for air I take kapa = 1.4


Your compressor has a pressure ratio of about P2/P1 = 18 per stage.
With an air inlet temperature of 27 °C in the cylinder, this results in a maximum air temperature of 412 °C.
This temperature is immediately present in the air volume that don't touch the walls and cannot be avoided by breaks.

With three-stage compression to 343 bar final pressure, the pressure ratio is 7 per stage.
All other things being equal, this results in a maximum air temperature in the cylinder volume of 250 °C.

For test runs you don't need a pressure maintenance valve. My compressor doesn't have one yet and I'm also looking for one. I open the tank valve and then close it again so far that I have at least 110 bar at the pressure gauge on the fill hose . With some valves this works well, with others it is a pain.