Gas pressure?

[spikewt]

Im sure someone may have already asked this on here somewhere or if not it may be me being really simple but does anyone have an answer as to why we only have a maximum of 21 mbar regulated at the meter.

the reason why i ask is a national grid guy came out to a job i was on today where the regulator was only giving out 18 mbar working pressure. i thort id pick his brains and he dint have an answer but said america has high pressure past the meter so there aint much problems with low pressure's and pipe sizing issue's!

now i know there are some pretty clever guys and girls on here and there are also some pretty amature people. i jus hope iv not missed something in that very expensive qualification i hold and make my self out the be the latter in that previous sentance!

 

[oldplumber]

cos all our appliances are designed to work at 21mb

 

[psk]

that is bcoz we use G20 NG appliances which are designedto operate with a maximum of 1 mb pressure drop.
as i was taught, if the working pressure at the meter is less 21+/-mbar there is a a blockage in the supply pipework.

you can correct me if i am wrong, thats just more blessing of advice.

thx

 

[spikewt]

how about the appliance regulating the pressure it self??

 

[spikewt]

oh he jus changed the regulator cause it was faulty by the way!

 

[psk]

that is the burner pressure being regulated not the inlet pressure to the gas valve.

some appliances even work on 10mbars or whatever the manufacturers want them to set on but he inlet pressure should be 20+/-mb

cheers

 

[spikewt]

but thats sort of what im getting at. on a long run round a house for instance, to get that "less than 1 mbar pressure drop" it can sometimes be some big amounts of large pipework but if you was to up the pressure and as long as the pipe could provide the correct gas flow then wouldnt it eliminate a few problems. the gas valve is regulating so why do it to such a low pressure at the meter? i know this may be a stupid subject.

 

[oldplumber]

cozsomeone decided when they first laid a gas main it would be a good idea to work at 21mb. If you pumped everything up to 1 bar then all yours mains would have to work at a higher pressure and then I expect youed find gas leaks would become more like a small Nagasaki impersonation than our present explosions.

 

[Dotty]

cozsomeone decided when they first laid a gas main it would be a good idea to work at 21mb. If you pumped everything up to 1 bar then all yours mains would have to work at a higher pressure and then I expect youed find gas leaks would become more like a small Nagasaki impersonation than our present explosions.

Take more'n yer hairs off yer arm lol

 

[spikewt]

What about medium pressure? I know it wont happen what im sayin but would it solve all this low pressure problems we keep findin?

 

[Billy Bob Bob]

try running a gas hob at over 21mb see what happens to the street,flames would lift and extinguish

 

[Puddle]

What about medium pressure? I know it wont happen what im sayin but would it solve all this low pressure problems we keep findin?

How we ended up with existing pressures I do not know but they are adequate,the industry is in discussion now and maybe on new mains, pressures can be increased,we may come to a time when certain boilers can only be fitted in certain areas with the right pressures,like how broadband is done

We are only finding these problems really because of boiler manufacturers unrealistic targets that they have no right to request at the present time,if we had twice as much pressure ,the manufacturers would just make smaller units that require the max pressure again

Up until a few years ago the existing pressures were far more than was required at domestic appliances and still is really if manufacturers would get in line,also it gave us a nice % leeway ,how we have none,I find it hard to believe the manufacturers are getting away with output claims that can not be met during peak demand periods if at all

imho

 

[GrahamM]

Don't know where or when it came to pass, but it has been decided that 20 mbar is a good safe happy medium for a domestic gas supply pressure. If pipework is properly sized you have no problems. Any higher a gas pressure would be unsafe for domestic situations.
You mention medium pressure solving the low pressure problem? Your standard low pressure gas supply may be upto 75mbar before the meter, so the gas supply is not the issue. The issue is poorly sized pipework in an installation.

 

[Reg Man]

Back to basics: Many boilers will regulate down to lower pressures, but its all about volume, pressure and speed with the amount of air. What would happen if you over pressure a gas hob? Lifting off the burner. The appliances are designed to burn for the pressure and type of gas burnt. I came across a NAT GAS cooker fitted on an LPG supply. It was very efficient, appparently the user cooked a chicken in 20minutes, but it was very sooty.

 

[gbgas001]

the reason why i ask is a national grid guy came out to a job i was on today where the regulator was only giving out 18 mbar working pressure. i thort id pick his brains and he dint have an answer but said america has high pressure past the meter so there aint much problems with low pressure's and pipe sizing issue's!

Because LPG works at higher pressure 37 mb +/- 5mb.... you are allowed a 2.5mb drop through the pipe work
so the logic is there in the statement. but as the rest of the guys said its appliance design.... or more so... injector size.

when the country moved from town gas to natural gas (for those of you who may remember) the pressure was increased and the injectors were made smaller

gb-gas

 

[Reg Man]

In more recent times; The Isle Of Man, was converted from LPG gas air mix on the grid, to natural gas. A pipe line was laid in from scotland. All of the appliances in Douglas had to be converted over to Nat Gas because to previous pressure and was much lower. This included injector sizes and some burners. There is some useful reference material for combustion characteristics in the old CORGI essential gas safety manual section 3.