i may have totally over looked this with regards to meter governors...

[acecharly]

This question is purely hypothetical and i dont see it happening to soon, but anyway, Why do we put governors on meters? i was never told this. Im assuming its due to having mains pressure running round the dwelling but then if the meters under your stairs 2 bar could be just as bad if there was a leak. Why cant we have governors on every appliance and an actuator instead at the meter to isolate the gas automatically if a large drop in pressure is registered this what ive allways done in plant rooms of hospitals where you have lots of kitchens running of a main. Be the end of gas starvation at the appliance and would reduce material costs on the carcus ....so fundamentally what havent i taken into account? cheers

 

[Resolute]

You wouldn't have 2 bar under stairs as medium pressure should be outside. Low pressure 0.75mb can be run into the property.

 

[AWheating]

75mb.

the main reason it will never change would be cost. pointless re-inventing the wheel really.

 

[acecharly]

ok have to go over that never liked them, allways struggled to reset them aswell, but still anyway 75mb would still be ok to stop gas starvation at any appliance so why does it have to be governed at the meter?

 

[Ermintrude]

Plus make appliances more expensive and a leak of 4mbar over 2 mins would fill street not just dilute under floor. All those air changes in plant rooms might dilute leak?

 

[acecharly]

didnt see your post there Mr wheating , i can see what your saying, cost but it would easier. Seems mad its so close to whats needed i.e. 21 at meter and 20 at appliance, if they made it say 26 at the meter it would give a better range. So being so close im thinking there must be another reason. Probably wrong though lol

 

[acecharly]

Plus make appliances more expensive and a leak of 4mbar over 2 mins would fill street not just dilute under floor. All those air changes in plant rooms might dilute leak?

i dont quite think it would fill the street at 4mb/2mins, all boilers have a governor already. Is it the meters themselves? Is it to do with making sure we dont use more gas than were ment to?

 

[Kev the gas]

Acecharly, really think you need to get a hobby !

Gas pressure has to be regulated as you know, the lower the gas pressure inside a domestic property the better incase sh.t happens.

As a rule large commercial properties gas appliances are better maintained/ larger air changes than the average domestic property.

In the old days gas meters were fitted internally, havent seen a house built within the last 15/20'years without an outside meter box.

Appliances with a correctly sized gas pipe wont suffer from gas starvation.

 

[helpsy]

On my gas training they said they are going to be putting into place a system with 500mb

 

[acecharly]

Hi Kev just a Q that came to mind, my first reason is what you say about safety.

Its a good point you dont see any internal ones nowadays unless in a meter housing for apartments etc

Also air changes can be huge in a plant room very true.

When i did my domestic gas it was a quickie course so i probably do ask some daft questions but thanks great points mate.

 

[acecharly]

On my gas training they said they are going to be putting into place a system with 500mb

are you sure they werent talking about mega bytes and computers mate

 

[Kev the gas]

Doubt it will be in my life time and I am 44.

A complete/nearly repipe of the whole country, I know a lot has already been done, but still a long way off.

 

[Killy Bing]

To be honest my bum would wiggle with higher pressures in a domestic house.

Lpg is slightly different because its such a searching gas, if theres a leak you know about it.

you can have a test sat with no drop on natural gas over 2 minutes, leave it on there for a few hours and it will drop the lot from a leak "outside the tightness testing procedure" hence ventilation requirements doe boxing in.


Boiler not working, i got sent to look why
Medium pressure rig, tested all fine, no let by, 2mb drop over 2 minutes ok thats fine on a u6 appliances are connected.

Working pressure of 76mb when the gas valve opened!

So that 2mb drop at 20mb over two minutes
i wonder what it would have been at 76mb!

 

[acecharly]

Im just glad ive never come accross a medium pressure meter if ever i had to reset one id have to go back to school or bore myself with the viper sure its quite easy but i have forgot, dont you have to hold something until you get so much pressure? im actually goin to look now as i feel all inadequate haha.

Ive had 30mb at the meter standing before now but as i said in a previous post transco werent that bothered they were more concerned with it had it been low.

That was quite a funny situation aswell, one of the first jobs i did on my own. The initial reason i called them was that when i did the letby it went up to 30mb from the 10mb in a minute so i was like oh carp better call em out.

When the guy got there he said it was ok and that he had a special tool for such problems...turned out to be a paper clip. He poked the test point on the meter and cleared some grease. Turns out when i did the letby the system went upto 30mb but the pinhole in the test point couldnt let enough pressure through to the manometerso it slowly crept up!! You live and learn lol

 

[Ermintrude]

i dont quite think it would fill the street at 4mb/2mins, all boilers have a governor already. Is it the meters themselves? Is it to do with making sure we dont use more gas than were ment to?

4mbar loss over 2 mins when run constantly equates to 19l per hour from memory ( see technical note to igup/1b) if at 3 times that the rate is cubed I think. So that's about 7000L per hour? Correct me if I'm wrong please!

 

[acecharly]

That cant be rite surely? in my gauge 4mb is about an inch long. If i lost 1 of those volumes every 2 minutes for an hour that would be 30 lots which is about 2 manometers worth? it wouldnt be 1 lkitre let alone 7000.

 

[Killy Bing]

That cant be rite surely? in my gauge 4mb is about an inch long. If i lost 1 of those volumes every 2 minutes for an hour that would be 30 lots which is about 2 manometers worth? it wouldnt be 1 lkitre let alone 7000.

Millibar is pressure and litre in a unit of volume.
the manometer only reads the pressure, the amount it drops by has no relation to volume of the install.

if you drop 1mb on a 10 litre install well, that isnt much
drop 1 mb on a 1m3 install.....thats hell of alot more!

although i think ermis numbers are rather high!

 

[acecharly]

Millibar is pressure and litre in a unit of volume.
the manometer only reads the pressure, the amount it drops by has no relation to volume of the install.

if you drop 1mb on a 10 litre install well, that isnt much
drop 1 mb on a 1m3 install.....thats hell of alot more!

although i think ermis numbers are rather high!

Thats exactly what i ment... lol

 

[Ermintrude]

19l per hour is low. Value cubes can't remember equation but to do with area and force acting on it and volumetric flow rate. Will dig it up.

 

[acecharly]

are we talking about the inverse square law?

 

[acecharly]

You would be talking just over 1/2 litre per second at that rate thats an open end more than a leak

 

[acecharly]

sorry nearly 2 litres per second

 

[Ermintrude]

19l per hour.

 

[acecharly]

That's not very much then. I'd imagine for it to do what your saying would mean that the size of the leak would have to cube for it to cube the loss as the only thing that's changing is the volume. Still its enough to blow the door of a boiler compartment if there were no ventilation.

 

[AWheating]

So you think it's a good idea to fit every gas fire and cooker in the country with a regulator and change the one on every heating appliance just so you don't have to have one at the meter.?

Also so what happens when you don't get 75mb from the main, put a pump on it to bring it up? Then a meter reg to get it back to 75.............. Seems like the current method works better to me.