One for the Corgis

[megawatt]

Given the increasing demands for higher gas volumes why are we still working with the relatively low mb operating pressure which was specified decades ago when demands were less.

Why not legislate for an increase in supply pressure and utilise point of use regulation (as regulators are cheap as chips) instead and negate the need to rip out miles of copper every time a new boiler is fitted?

MW

 

[gas4you]

There are several new gas installations that utilise medium pressure.

If you have 21mBar at meter govenor and pipe work is sized correctly then you should easily get 20mBar at each appliance.

Medium pressure overcomes the low supply pressure from the street.

 

[megawatt]

Okay, let me put this slightly differently.

The biggest % of homes still have gas pipework sized for appliances in use decades ago and, to utilise new technologies, require much pipework upgrading costing lots of £'s and much disruption.

Assuming the supply in the street is capable of supplying the demand what prevents legislation from making meter outlet pressure (say) 150mb with point of use regulation applied at each appliance?

I'm curious how medium pressure at the meter overcomes low pressure at the street or have I misinterpreted what you mean?

MW

 

[namsag]

The supply in the street is not capable of taking the increased pressure with many areas running at a reduced pressure so the mains don`t leak . Although there is a renewal programme the cost to renew everything would be horrendous with far more disrution than a householder having to alter there pipework.
Individual appliance governors to take down the pressure would be bulky and have to be hidden within the new appliance or on pipework to old appliances which is not always possible sometimes you only have a few inches of visible pipework,
So most cost effective way is for larger pipes in the house for the modern high input combi`s and cooker ranges etc

 

[Agile]

I'm curious how medium pressure at the meter overcomes low pressure at the street or have I misinterpreted what you mean?

MW

I understand what you are asking but there are about 15 million homes with a gas supply which would all need to have new regulators and meters fitted.

Only about 7% of homes have new boilers fitted each year and any pipework upgrading is then done at the cost of the owner.

The money is currently being spent upgrading the street supplies to avoid leaks and in a few cases to give a potential supply pressure increase capability.

Tony

 

[doitall]

Also the risk of a potentially dangerous leak is greater with a higher pressure.

 

[megawatt]

I would concede that this is true if you get into much higher pressure DIA but not moving from 20mb to 200mb which would probably make current 22/15mm installations more than adequate

It just seems to me that we are only delaying the inevitable unless we expect homes to be gas piped in sewage terms in the future

Thanks for the responses.

MW

 

[ChrisR]

DOmestic gas pipes can now be up to 35mm, which is even big enough for my house .
Remember things like cookers and fires may have no appliance regulator at all, so they would all need changing.
One route could be a small pressure booster sited right by the meter, as long as all appliances in the house were suitably dealt with.
It's done industrially, but I can't see it happening in houses, because there's too much diy, and too many existing gas fitters would never get it right.

 

[WDIK]

Assuming the supply in the street is capable of supplying the demand what prevents legislation from making meter outlet pressure (say) 150mb with point of use regulation applied at each appliance?

generally local district supplies operate at a MOP maximum operating pressure of less than 75mb.
many fall well short of that figure.

because the district infastructures are elderly there is a known leakage rate through out, this is lessen during summer months by reducing the actual district pressure.
it saves money.

because low pressure supplies are fed from medium pressure supplies and regulated down the MIP maximum incident pressure is 200mb.

i refer you to the normative document BS 6400-1
specification for installation of domestic-sized gas meters maximum rated capacity not exceeding 6 cubic M/h (2nd and 3rd family gases)

in particular to a little known content...


6 Design

6.1.3Pressure absortion

The pressure absortion across the primary meter shall not exceed 4 mbar at a flow rate equivalent to the maximum capacity of the meter, with a pressure of 19 mbar at the outlet of the emergency control valve.

it is a requirement of BS 6891 that the maximum pressure absorbtion across the installation pipe is 1 mbar.

conclusion being that the working pressure after the meter can be 15 mbar and drop to 14 mbar at the appliance inlet.

 

[ChrisR]

Not as little-known as it was, as it's part of the ACS gas test now.

Just worth mentioning -
Sometimes the street pressure can drop to below 19mbar, even around 15mbar, and
MANY appliances won't light at 14mbar.

If we had small boosters which guaranteed to maintain the upper outlet pressure, which is 23mbar, that would solve a few problems, but not all. 30mbar and a regulator on every appliance could do it.
?

 

[WDIK]

yes but they still charge for it at the same rate

 

[ChrisR]

Yes. I got that stuck in my head until someom=ne poointed out that you're measuring it relative to atmosphere so you're getting

1015
1021
of what you should, which is 99.4% of it!
You could always freeze your meter to squash more in!

 

[WDIK]

Yes. I got that stuck in my head until someom=ne poointed out that you're measuring it relative to atmosphere so you're getting

1015
1021
of what you should, which is 99.4% of it!
You could always freeze your meter to squash more in!

can you explain that more clearly?

so far I imagine, from situations ive seen, where due to inadequately sized supply pipework there has been an inlet pressure as low as 13 mbar,
yet due to the construction of meters they measure volume.
so 1 cu ft of gas is the same volume at 20 mbar as it is at 10 mbar.

reduce the contained pressure to atmospheric pressure then the 20mb has twice the volume as the 10mb.

i would postulate that the calorific value of the 20mb is twice that of the 10mb.

 

[gas4you]

Sounds to me that this post is degenerating into a load of bo***cks, with some trying to score points with ridiculous equations that mean jack sh*t in the real world

 

[clf-gas]

I was/am under the impression that supply pressure could go down as low as 12mb, is this not the case anymore