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Re: What's a Gas Siphon |
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| message from Set Square on 21 May 2004 |
If you had asked that question a week ago, I couldn't have answered it.
Today, I can!
We have just had the gas main replaced in our road - the old cast iron pipe
being replaced by plastic. My house is at the lowest point, with the road
rising slightly in either direction. Opposite my house was a gas syphon.
This turned out to be a metal bomb-like object immediately underneath, and
connected to the gas main - designed to collect any condensation forming in
the pipe. A small vertical pipe comes from near the bottom of this chamber
up to ground level. Apparently the idea is that when a tap on the top of
this pipe is opened, gas pressure forces any collected water out through the
pipe.
This device has been removed, and not replaced when replacing metal pipe
with plastic. The explanation given by the contractors is that you don't get
condensation in plastic pipes. My suspicion is that you don't get
condensation in natural gas - whereas you did in towns gas, which was still
(just) in use when the original pipes were put in around 1965.
I didn't know that the syphon was there until a few days ago, and have never
seen anyone accessing it in the 27 years I have lived in this house!
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| Andy Hall replied to Set Square on 21 May 2004 |
When I was a kid, the gas board used to have a kind of tank/compressor
with pump (a bit like a roadworks one only smaller) which was towed
behind a van.
Apparently with towns gas and metal pipes there was a problem of
rusting inside the pipes as a result of the water content in the gas -
I am not certain whether it was fundamentally there or as a result of
the scrubbing process to remove as much of the crap in it as possible.
This particulate matter would be carried through the pipes and collect
eventually in customer's service pipes from the road and reduce the
gas flow.
THen the van and compressor would show up, hoses would be connected at
the meter and the rusty powder sucked through - at least I assume it
was sucked. I saw this being done three or four times at
neightbours and of course the gas men would always have a fag on while
they were doing it. HSE? WHat HSE.
For a while after natural gas was introduced, I understand that this
was worse, because it is basically dry and more particulate matter
came away. However, one doesn't often see the suction machines
nowadays so I guess with gradual conversion to plastic pipes as well,
the problem has gone away.
.andy
To email, substitute .nospam with .gl
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| the q replied to Andy Hall on 23 May 2004 |
When natural gas is brought ashore the last stage before feeding the gas
into the grid at around 1000 pounds, is to fed it into a Dew Point Train.
all the way down the train glycol (PEG) is sprayed into the flow. At the end
it then goes through a propane chiller and the glycol and most off the water
drops out.
the gas then is fed to the grid at around 0 degrees.
Hence no condensation in the grid.
Just so you know..
The Q (ex Bacton Gas terminal)(for a short time before we got taken over and
half of us got made redundant)
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| the q replied to the q on 23 May 2004 |
OOps ERROR!!! the Peg Above should be MEG (Mono Eth...)
The Q
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| sylva replied to the q on 23 May 2004 |
Is this propane chiller where the propane and butane drops out?
AJH
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| the q replied to sylva on 25 May 2004 |
Nope it's a wacking great fridge which cools the gas flow, ( to roughly 0
degrees for Transco to accept) propane is the refrigerant, compressed by a
Huge V8 each cylinder is over a foot across and that powers two compressing
cylinders of around half a ton each!! Oh and there are four V8s of these in
the one building if required.
The compressor is powered by waste gasses drawn mostly off of the small
amounts (comparatively) of hydrocarbon liquids that come ashore with the
gas.
The hydrocarbon gases are drawn off of the liquids so they can be made
stable enough for transportation for processing.
I hope that's a good explanation above, I've just been on the home brew
again..
The Q
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| IMM replied to Andy Hall on 21 May 2004 |
You are correct. Town gas contained water. The first ng system was a pilot
in London in 1966, about a year after Sea Gem discovered gas in the North
Sea. They moved very fast to use ng. Most ng was introduced around 1970-74.
A siphon had to be installed immediately after a meter. Many of them are
still around with few people knowing what it was for.
Many pipes started to escape after ng. The pressure was twice town gas, but
that wasn't the problem. The moisture helped seal up some joints. Once they
dried out they escaped.
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| Andy Hall replied to IMM on 22 May 2004 |
I think ours was done in the late 60s but can't remember exactly the
year. Certainly before 1970.
At the time, I'm sure they were still storing gas in the old fashioned
holders, which used water as a seal, but presumably there must have
either been some dryers after these before the distribution or
something like that......
After a domestic meter? I don't remember seeing one of those.
What did they look like?
I suspect that they still do.
.andy
To email, substitute .nospam with .gl
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| Jerry. replied to Andy Hall on 22 May 2004 |
<snip>
Surely BEFORE the meter, you wouldn't want to such all the crap through the
meter nor would you want to force compressed air through a meter the wrong
way ?
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| IMM replied to Andy Hall on 22 May 2004 |
The water seals were impregnated with oil. They did not make any difference
to the gas. It was stored at low pressure and pumped to high pressure in
many cases.
Yep.
All the internal pipe had to fall back to the meter, so water would be
collected at the trap. The lead outlets was in a U shape from the meter
horn. It then went to copper or iron. A tee was inserted to take feed the
house. the downward side off the tee had a short piece and a plug on it.
In many installations the plug was under the floor. During the 1963 freeze,
the Gas Boards were working 24 hours to unfreeze the siphons and empty them.
Better seals are now fited.
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