Navitron Renewable Energy and Sustainability Forum

SOLAR THERMAL => Solar Thermal Systems => Topic started by: wookey on January 24, 2016, 09:11:02 PM



Title: Leaking ball valves
Post by: wookey on January 24, 2016, 09:11:02 PM
Hello chaps, long time no see.

So, I have a now 6.5 year old ST system, which has generally worked very well, modulo some heat exchanger corrosion requiring a fettle 3 years ago, and occaisional temp sensors needing replacing.

Now I've noticed that all 4 of the service values in it are leaking (out of the screwdriver twizzly-bit). These are standard 15mm ball-valves, 2 straighr, 2 angled. Probably BES's finest 'brass, compression, imported' (OK, cheapest).

Anyone else had this problem? I presume there is an O-ring in there and it doesn't like the persistent high temps it gets in the summer? OR maybe itdoesn;t like the glycol? Or maybe both.

So, anyone know which ones _will_ survive more than 5 years in this situation? We have quite a lot of experience between us now. But I guess mine runs hotter than most with it often being 80-90C in the summer (due to being top-loading, not bottom). So maybe the rest of you are not ruining your gaskets?

Servicing ST is a bit inconvenient as it's best done in the winter dark, so I'd quite like not to just fit more cr*p ones.

Is it just a matter of buying less cheap and nasty valves?

There is plenty of choice in plain 15mm service valves:
I think the failed ones are these:
https://www.bes.co.uk/products/097.asp#10406  (1.27)
and
https://www.bes.co.uk/products/097.asp#21050

There are plenty of alternatives, although most are threaded rather than compression or have levers/handles so don't fit in the insulation so well.

These say 'max 85C, but also 'suitable for steam' - surely that's a contradiction?
https://www.bes.co.uk/products/099.asp#8121  3.19
Is that good enough in practice?

There is 'genuine ballofix':
https://www.bes.co.uk/products/097.asp#6131
Expensive at 13.76. Are they good with heat/glycol?

Or stainless (1000bar, 230C!):
https://www.bes.co.uk/products/100.asp#20304
And only 5.78 (plus compression->3/8" fittings (1.30*2))
They'll take up more space so some re-arrangement needed in
http://wookware.org/pics/solar/038-IMG_2554.JPG.html
But not available in 90-degree form.
Any issue mixing copper and stainless bits?

I think I'll just scrap the 90-degree isolators. They are not very useful in practice. Not enough to justify leaks, anyway.

One thing I did wonder is whether I can just put new gaskets in my valves? Anyone tried? They have a tricky push-fit retaining clip in one end, which seems very hard to take out - as once it's popped in it rotates, and you need to bend all 4 flanges in at once to get it out. I have failed in this so far as it just spins when you try to pry it.

And I'd still need to find a gasket of exactly the right size/material. anyone know what is normally used? Nitrile rubber? And which things are best for PV heat+glycol (PTFE is presumably fine)?

Discuss.



Title: Re: Leaking ball valves
Post by: dimengineer on January 25, 2016, 08:33:00 PM
My thoughts
 - at 3 a valve you really are not getting quality.
 - I like the sound of the SS valves - thats what I think I'd go for
 - Replacing the O ring on such a small/cheap item is a mugs game - they really are not designed for repair.
 - O ring material is a tricky subject. Pure PTFE is not too good - it cold sets and has very little resilience, so is a nightmare to seal. I'd suspect nitrile is whats in there - which should be OK, but it depends if you've stagnated, as its only good up to 110c


Title: Re: Leaking ball valves
Post by: desperate on January 25, 2016, 09:13:15 PM
Do you really need service valves?? mostly those ball type valve are horrible nasty bits of scrap that will leak the first time you use them, generally they have plastic/nylon/nitrile etc which just wont last at the sort of temps ST runs at. Most ST systems only have about 10litres in them so if you have to work on them just drain it into your garden sprayer and when finished pump it back in. I use standard gate valves for drains and air bleeds as you can plug the open end with a short length of copper and a JG stop end and tighten up the stuffing nut around the spindle if it weeps, far less hassle than those ball valves.

As their name implies they are balleaux.

Desp


Title: Re: Leaking ball valves
Post by: martin W on January 31, 2016, 10:21:10 PM
Can you use normal lever or T ball valves instead of those rubbish service valves? Pegler 15mm at screwfix about 6 each..

Failing that use gate valves, you can usually badge the stem seal with ptfe tape if it weeps. I think some of the SS valves do 130 deg C


Title: Re: Leaking ball valves
Post by: wookey on February 04, 2016, 04:33:21 AM
Quote
Do you really need service valves??

Well one to bypass the non-return valve for filling, and another to open/close the filling point.

How would I fill/empty without said service-values?  Some kind of radiator valve thing with a fill-attachment? (The radiator-type valves in the system have not leaked).


Title: Re: Leaking ball valves
Post by: wookey on February 04, 2016, 04:36:52 AM
Quote
I'd suspect nitrile is whats in there - which should be OK, but it depends if you've stagnated, as its only good up to 110c

Well, it has stagnated a couple of times (due to sensor failures), but it's designed so that > 110C fluid never gets down to the bottom where the service bits are. Maybe it didn't work as designed, or maybe persistent operation at 80-90C is enough to make them leak.


Title: Re: Leaking ball valves
Post by: wookey on February 04, 2016, 04:42:40 AM
Quote
Replacing the O ring on such a small/cheap item is a mugs game - they really are not designed for repair.

Right. I had a go and concluded that it's essentially impossible to disassemble without knackering it. And certainly not worth the effort.


Title: Re: Leaking ball valves
Post by: Nickel2 on February 04, 2016, 10:19:35 AM
Copper and stainless OK. Most FPHX's are stainless, the plates vacuum-brazed together with copper.
In the past I have winced at the price of proper ball-valves, but then denied myself a couple of pints of ale per unit fitted. The health benefits are amazing; reduced hangovers, better sleep, weight-loss etc. Fit and forget.
Experience teaches that cheap gate-valves and cheap ball-valves fit into the same category, i.e. next years nightmare. I am wary of partial openings of ball-valves, in case the seat-plastic takes a set at the degree of opening and weeps after movement. Open or shut, never partial.


Title: Re: Leaking ball valves
Post by: Antman on February 05, 2016, 10:00:24 AM
Not sure if the cheap ball service valves even have an 'O' ring seal - they just rely on the internal nylon ball. Probably why they are only rated 70 deg max (or even 60 deg in some I have seen!).

The filling valve can be extended away from the other components to keep it clear of heat. A quality Pegler valve (or similar) should then last. The better Pegler lever 15mm valves are rated at 120deg at 5 bar.

Antman


Title: Re: Leaking ball valves
Post by: wookey on February 06, 2016, 12:59:37 PM
The cheap BES ball valves that leaked do have an O-ring. Seems to be nitrile rubber, and not in obviously bad condition, but I suspect is a lot harder than when it went in. It now feels like hard rubber rather than soft rubber.

The fill valve can be extended away from the main run, but that's rather less convenient for the one-way valve bypass. I shall put a pair of Pegler valves in, without changing the pipework more than I have to to accommodate the longer valves, because that's a pain. This should give another 10 years operation at least (assuming they are twice as good as the first lot).


Title: Re: Leaking ball valves
Post by: Mostie on February 06, 2016, 01:41:05 PM
got mine from Screwfix Mr Wookey, 4.99 yellow handle full bore, no mention of temperature  whistle fitted to solar thermal, if they melt you will be the first to know  chocpot:


Title: Re: Leaking ball valves
Post by: MR GUS on February 06, 2016, 04:48:43 PM
got mine from Screwfix Mr Wookey, 4.99 yellow handle full bore, no mention of temperature  whistle fitted to solar thermal, if they melt you will be the first to know  chocpot:

Ditto (though not on a solar thermal system) I had my daughter cut out the old "Wenk" one, the cheap no good from the word go units that are fitted as standard & in case of emergency delayed turn off by need of a damn screwdriver on soft as butter monkey metal ! ...I hate to think how many knacked ones in the uk have wasted water as a result, especially bearing in mind how clueless folk are as to "what it does".

My nipper was perhaps 7 or 8 when she did this as part of a cub / beaver badge, personally i'd make the screwdriver variant illegal to fit any more, far more sensible to plan the application & pop a tile on a clip or two if it needs not to be seen.

Face it, fitted & "knackered" as  a stopgap to a proper repair it nigh on renders a system useless & makes more work of an eventual repair (ie replacing the cisterns filler unit) ..which the nipper did also, ..worth the extra for far less bother, I can live with a yellow handle compared to a wet dripping floor, musty room for a couple more quid. ..the cheap units are only good for a handfl of turns of which if you are checking your pipework out periodically you can wreck em pretty quickly, ...a decent pull lever enables anyone to check or utilise as required.

As a result I actually deigned to do a few more jobs on that area of the plumbing, something i'd put off till the point of ruination (may do) under the old chepo-unit, gives more reassurance to those who come after you as well imho (trying to undo the  bad from the previous fool).

As I recall the screwfix unit had a pretty decent rating, but i'd definitely up to the pegler for customer service "heave ho" if required.

(the use of olives was a first for both of us too)  :-[ ...much to my chagrin


Title: Re: Leaking ball valves
Post by: Axel on April 02, 2016, 12:13:15 AM
I am plotting to use 1000WOG valves on my system, they are supposed to cope with high temperatures and pressures I think (hope)  - There will be three banks of four ST panels, 4 in series, each bank can be isolated each end with a three port manual valve.  Reason being that if you operate the valve it always leaves the panel either connected to pipework (and therefore to the expansion vessel & PRV) or open to air, so no pressure issues / exploding panels if the valve is inadvertently operated. 

The idea of being able to isolate the banks is so that I can reduce output in summer - 4, 8 or 12 panels connected.


Title: Re: Leaking ball valves
Post by: Stochengberge on April 02, 2016, 08:16:14 AM
So the isolated panel will be in an almost permanent state of stagnation through the summer? Sounds risky to me...
Or are you planning a drain back system?

And I'm guessing you can get 1000WOG valves at a reasonable price? They may be a bit over spec'd, but better over than under.

SB.


Title: Re: Leaking ball valves
Post by: Nickel2 on April 02, 2016, 10:16:45 AM
Can we assume that these are flat-panel units? My own (home-made) panel will go well over the boiling the point of water if not kept covered or pumped. When I left my panel uncovered before finalising the plumbing, it got hot enough to make the twin-wall polycarbonate soft and saggy. When water was introduced, there was steam. A closed valve at both ends would result in a roof-mounted balloon.