Unusual fault on 6 bar PRV

[gassafe]

Hey guys,

i changed a faulty 6 bar PRV on a customers Range tribune cylinder about a year ago ( it was gushing water through the tundish & the fault was that there was a big etching on the seat of the PRV just like when a tap has been dropping for years!

Called back today & the same fault again?!! Big recess in the seat of the valve so it was running out the PRV, the valve itself is working okay & shut, but why would the brass seat be wearing out! All I could come up with was that the water must be very aggressive, but iv not had that before!

Any ideas, this is the valve in question...

 

[Atouchofgas]

Is the pressure in the expansion vessel ok?
Just wondering if there's to much pressure causing it to lift a wee bit

 

[billybob150811]

had this myself needed a new 18 litre exp vessel then I had to buy a whole new inlet block as they don't sell the prv seperatly anymore

 

[Chalked]

Generally, that fault is over pressure.

 

[townfanjon]

Its a long shot pal, i was a trib engineer for about 5 few years . Sorry I cant tell from the pic but is that the ex valve thats held in with the small machine screw that is a allen key head . If it is , the screws can work loose, or aren't tightened in the first place .

 

[kris]

I wouldn't think it would be high pressure as that would simply lift or open the valve and would attack the seating first, it is strange it's the brass that's getting it,
Don't suppose it's a private water supply , maybe a combination of aggressive water and high pressure

 

[gassafe]

Pressure in the vessel was low again, they seem to need recharging once a year these crap things! Only a little 8 litre one...

Seems excessive replacing the whole block for a 20 quid part lol!

 

[townfanjon]

They do need checking every year pal, it sounds like somebody has changed that vessel , it should not be an 8 litre no wonder theres problems, what size is the cylinder ?

 

[gassafe]

They do need checking every year pal, it sounds like somebody has changed that vessel , it should not be an 8 litre no wonder theres problems, what size is the cylinder ?

It may be 16, it's a new build estate & has the small vessel provided with the tank, it's probably about 120 litres...

 

[townfanjon]

A 120, would have or should have a 12 litre. You would expect a vessel to loose up to a third or less of pressure i.e if its down to about 2 bar it is probably best to change it, and for the bit of extra cash, I would be tempted to put a 18 litre on it

 

[townfanjon]

Sorry , pressure loss over a year / between services

 

[gassafe]

They do need checking every year pal, it sounds like somebody has changed that vessel , it should not be an 8 litre no wonder theres problems, what size is the cylinder ?

A 120, would have or should have a 12 litre. You would expect a vessel to loose up to a third or less of pressure i.e if its down to about 2 bar it is probably best to change it, and for the bit of extra cash, I would be tempted to put a 18 litre on it

Yes it was probably a 12, I was thinking 16 was the next size up but it's defs the smallest one which comes with these things!

If its dropped in pressure then surely it just needs re-pressurising?

 

[gassafe]

Yes it was probably a 12, I was thinking 16 was the next size up but it's defs the smallest one which comes with these things!

If its dropped in pressure then surely it just needs re-pressurising?

A larger vessel would make sense tho, less stress on a larger vessel I suppose, still dosent explain the funny pitted brass seats!

 

[gassafe]

I wouldn't think it would be high pressure as that would simply lift or open the valve and would attack the seating first, it is strange it's the brass that's getting it,
Don't suppose it's a private water supply , maybe a combination of aggressive water and high pressure

Not a private supply no, just regular Thames water... Iv had to change a few of these 6 bar valves in the same estate so I guess it's just poorly produced parts on range tribune side of things!!or extra soft brass lol!

 

[townfanjon]

The 'seat' is a weird one , i dont know where you as regards your water hardness.
Think of the vessel as a car tyre, if you are constantly topping it up its obviously got a puncture.
I do loads of unvented services and some only loose 0.2 bar over the year, but as said , alarm bells ring if i go to one and its down to 2 bar, generally I top them up once , warn the customer its lost a bit too much , and then the year after perhaps change it.

 

[gassafe]

The Thames water website says the water harness at this postcode area is rated at 281ppm

 

[townfanjon]

Yep just noticed you are down the 'smoke' the expansion valve is a Caleffi made in Italy , i wont say any more lol