What is this? Is my multivalve missing something

[drabux]

I've bought a secondhand LPG system and having now connected up the Emer multivalve, I've noticed what appears to be a third inlet or outlet (arrow points to it). Is this the pressure relief valve? It does have a brass collar that screws on to it (see first picture). Should there be anything that fits inside the collar when it is screwed to the multivalve?
Thanks in advance.

Alan

[john_d]

im sure thats a pressure relief

[SimonHobson]

I've bought a secondhand LPG system and having now connected up the Emer multivalve, I've noticed what appears to be a third inlet or outlet (arrow points to it). Is this the pressure relief valve? It does have a brass collar that screws on to it (see first picture). Should there be anything that fits inside the collar when it is screwed to the multivalve?

There should indeed !

It is the pressure relief valve - or at least part of it. Attached is a photo of the innards of one of those valves, rather more parts that you might think I intend doing an article for my site when I get time.

The cap holds down a spring, which in turn holds a cap with rubber seal onto an orifice. You can see these in the top left of the picture. But that's not the half of it !

Look down to the right and down a bit and see the short stiff spring, large plunger, and brass sleeve. The flow for the pressure relief and thermal fuse goes through a small orifice in that large plunger - and if the flow is enough, the pressure drop will be sufficient to lift the plunger against it's spring and that opens a huge hole. If you look on the outside of the multivalve, you'll see three holes about 1/4" diameter (two are visible in the photo) which should have rubber plugs in them - these are the vents for this large valve. If that lets go then you are probably past caring and the car is a raging inferno.
The thermal fuse is at the top, just right of centre. The screw in plug has a soft core - probably some tin alloy with low melting point. If the core melts, the the little brass plunger can pop out, release gas flow, and trigger the main plunger to lift and vent the tank off at quite a rate.

Just for completeness, working clockwise from the top we have ...

• Thermal fuse.

• Liquid draw off assembly - you can just see the end of the dip tube and it's nut at the edge of the photo. Inside the brass fitting is the non-return valve.

• Level indicator/gauge sender drive. The bit of metal in the black plastic bit is a magnet and that drives a magnet in the indicator or sender through the brass. It is rotated by the float arm (not in the photo) which is part of the fill valve.

• "Servo" valve for the pressure relief valve and thermal fuse.

• Fill valve. The float arm fits into the brass bit at the bottom of the photo - and when it lifts high enough, it allows the pin of the fill valve to pop out, and the valve shuts to the incoming flow.

• "O"-ring for sealing the valve to the tank.

• Inlet and non-return valve. The black plunger and spring are fitted inside the large brass fitting.

• Internal ball valve. The two white rings are the ball seats, and the brass ring screws down the tube to clamp it up. The ball is turned by the stubby shaft fitted with the yellow lever.

• And finally, to the left of that is the solenoid valve. The coil fits over the stem and when current is passed through it, it lifts the small plunger you can see in the end of the stem.

Well, I'd just swapped one, and I just had to know what's inside

[drabux]

Thank you so much for this response. Very helpful. I ended up buying new multivalve because of the missing bits.

alanb

[john_d]

are you able to buy parts to service multivalves?

[SimonHobson]

are you able to buy parts to service multivalves?

I've never seen them for sale - and in general it wouldn't be worth while.

Trade price for an Emer valve is thirty-something quid, and for that you get something which you can reasonably expect to work and to have the pressure relief set up correctly. Once you start taking things apart to replace parts, then you have to get it all back together again correctly, get it all to seal, set up the pressure relief if you've disturbed it - and you're not going to be paying less in garage labour rates than for a new valve.

Probably the only bits that people keep before binning the old valve (at least I do) is the solenoid coil. These are easily replaced (without upsetting any gas seals) and do fail sometimes. The gauge sender would just be transferred to the new multivalve.