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Pressure regulation and supply control
An Important component in a
motorhome gas system is a regulator. This fulfils two functions:
1. It makes sure that the delivery of gas from a
cylinder is at a stable and constant pressure as required by motorhome's
appliances. It therefore evens out the tendency for a full cylinder to deliver
gas at a higher rate than one which is nearly empty.
2. It incorporates a union so that the flexible feed pipe to the supply system
can be coupled up safely to the cylinder without fear of leakage.
One of the problems of
gas systems is the absence of a universal coupling. To connect to a propane
cylinder the regulator is manufactured with a carefully machined and threaded
insert (male) which creates a close register when tightened up within the
receiving socket (female) of the cylinder. No washer is involved - merely
a close metal-to-metal location. The coupling method is the same on all Calor
Gas propane cylinders and you'll need to keep a spanner handy.
Regrettably butane couplings are less straightforward
because there are several different types. For instance, on a 4.5kg Calor
cylinder, there's a threaded female nut; this has to be positioned over the
threaded male outlet and
tightened anti-clockwise.
The left hand thread often surprises newcomers to motorhoming and a
spanner is needed to form a tight joint. There is also a small washer held
within the regulator coupling nut which must be changed periodically, however
spare washers are available for a relatively cheaply from any Calor stockists.
On both the Calor propane cylinders and the Calor
4.5kg butane cylinders, a robust turn wheel on the top opens or closes the gas
supply valve.
When motorhomers find it necessary to use Camping Gaz, they usually buy an
adaptor that screws into the top of the butane cylinder. This also incorporates
a control wheel and enables the type of Calor butane regulator already described
to be coupled into a Camping Gaz supply.
The larger butane cylinders from Calor Gas adopt a
different coupling method. The regulator has a special clip-on coupling. The gas
cock now forms part of the regulator itself whereas on the smaller 4.5kg product
the turn wheel is part of the cylinder.
To summarise, if using different types of cylinder, three different regulators
are needed plus an adaptor if you want to connect up to a Camping Gaz cylinder.
These are:
1. A Calor screw-on propane regulator - with open-ended spanner.
2. A Calor screw-on butane regulator to suit 4.5kg cylinders - with
open-ended spanner.
3. A Calor, clip-on butane regulator to suit 7kg cylinders.
4. Either an adaptor to enable a Camping Gaz 2.72kg cylinder to be coupled
up with a Calor screw-on butane regulator, or a Camping Gaz regulator with
on-off control.
Cylinder state
Assessing the amount of gas
remaining in a cylinder can be difficult. There are several devices intended to
give a clear indication of the fill, including weighing accessories.
If using Calor cylinders, one procedure is to establish their weight, when
empty, by referring to the information on the aluminium collar below the valve.
This is given in Ibs/ozs (if you prefer to work in kilograms, pounds have to be
divided by 2.2046). Then the cylinder should be weighed on bathroom scales to
establish by how much its weight exceeds the stated empty weight.
Alternatively the cylinder pressure can be monitored
using one of the gauges from a company called 'Gaslow', these are available
individually or incorporated in a 'Gaslow' regulator. They also serve a further
role as leak detectors. To assess the condition of a cylinder using a
'Gaslow' gauge, the gas must be turned on, with at least one appliance in use.
Taking into account the load imposed by the appliance/s a 'Gaslow' gauge then
indicates if the supply is in a good state, a mediocre condition, or approaching
exhaustion. Earlier gauges used a needle which
pointed to 'traffic light'
segments in the dial; the red section warned of a nearly empty cylinder whereas
the green segment indicated that all was well. On the latest gauges it is the
segment that moves, and to achieve even greater accuracy there are separate
read-outs for use on 'cold days', 'cool days' and 'hot days'. This is ok,
system, but it only gives an indication of cylinder condition when appliances
are being used.
Change over systems
Running out of gas is always
inconvenient. Even if there's a back-up cylinder, the business of disconnecting
the regulator and coupling up to a new one is a nuisance, especially if it's
raining. It is even more annoying if it happens when a meal is being cooked or
in the middle of a cold night when the heating system is crucial for comfort.
This is why a changeover system is so useful especially one which is completely
automatic. The simplest and least expensive types, like the
'Gaslow' manual changeover, merely involve turning off the failed cylinder and
opening the valve on its replacement. Since both connections are permanently in
place, the task takes seconds to complete. Automatic types are even more
convenient though progress should be monitored periodically so that steps can
be taken to remove and replace an emptied cylinder. In many systems the
exhausted cylinder can be disconnected and taken to a dealers for exchange
without upsetting the one that's operating; there's no risk of gas leaking when
one cylinder is uncoupled. There is also the Truma Duomatic L automatic
changeover, where there's a control panel for mounting in the living quarters
which bears red and green LED indicators. This enables you to keep a close watch
on the cylinders without having to go outside. There is also a defroster to
ensure the Duomatic L doesn't freeze.
Safety Notes:
For some time it has been ruled that work on gas connections,
flues and supply systems should only be undertaken by a competent gas engineer.
More recently, however, this prescription has been deemed too vague and some
advisers insist that only a 'CORGI' registered engineer tackles this kind of
work. Others assert that the requirement is even more stringent and state that a
'CORGI' qualified person must have successfully completed a course which
embraces training in LPG installations in leisure vehicles. This caveat is added
because some 'CORGI' registered engineers are only trained to deal with domestic
household installations.
('CORGI' stands for Council
for Registered Gas Installers. Registration is a
requirement for those who install and maintain LPG installations as laid down in
the Gas Safety (Installation & Use) Regulations 1994.
Always transport cylinders in its upright
position. If a cylinder is laid on its side, the
liquefied gas might prevent the pressure relief safety valve
from functioning
correctly. Gas can also escape from a
faulty valve and it's acknowledged that in the transfer from
a liquid to a vapour there's an approximately
two hundred times increase in
its volume, so the potential hazard is fairly obvious.
Pipe work and
Installation
After the cylinder and
regulator, the supply route starts with a length of flexible hose.
The flexible hose is neither a plastic nor natural
rubber; it is made from a special composition to comply with British Standard
3212 so do not replace it except with the correct part.
There should
be only one flexible
hose in the entire system - the one coupling to the gas cylinder.
Elsewhere, metal pipes must be used, copper being the most common material.
Where the hose is pushed on to ribbed unions, it is important that hose clips
are used to secure it. Flexible hose deteriorates in sunlight and
atmospheric conditions. Therefore it must be inspected regularly and replaced if
there are any signs of cracking or general deterioration. Flexible hoses
bear a date on the side to indicate when it left the factory; this may be a year
or so before purchase, depending on stock turnover. It is important to
note the date when new hose is installed since it should be changed
periodically. The Calor Gas Dealer Directory (1995) recommends this is done at
five-year intervals or more frequently if there is evidence of deterioration;
for instance, hoses sometimes lose resilience and stretch at ribbed unions.
The inboard end of the flexible supply hose terminates with a bulkhead
connector, after which the supply pipe is rigid. At this point DIY ends
and a qualified engineer is required. (See safety notes above)
Leak Detection
Whereas work on a gas supply
system should not be undertaken by a DIY owner, exercising vigilance over the
integrity of the system is different. A wise owner, for example, might want a
leak detection device fitted and some types are available that you could fit
yourself. In addition, if you want reassurance that couplings are sound, there
is no reason why you shouldn't check them using a leak detection liquid.
The procedure is to have the system switched on at the
cylinder and to keep all appliances off. Cigarettes and naked flames should be
extinguished. Couplings are then smeared with either a proprietary product or a
solution made of diluted
washing-up liquid. Once applied, check for bubbles - which indicates a leak. It
is usual to apply the mixture with a small brush and to hold your fingers around
the joint to prevent the fluid running away. If you find a leak, switch the
system off at once and get the coupling tightened or replaced by a gas engineer.
A more convenient way to monitor a system is to fit a
'Gaslow' gauge at the gas supply cylinder. These products were mentioned earlier
because they have an additional function of indicating the pressure in a
cylinder. The test procedure is as follows:
1. Turn off all gas appliances.
2. Turn on the gas supply cylinder; the gauge should show a green segment.
3. Turn off the gas supply at the cylinder.
4. Provided there is no leak, gas will be held in the supply pipes and the
gauge will remain green for a prolonged period.
4. Using a standard 'Gaslow' product, if the gauge remains green for at
least a minute, the system is sound.
Note: Over a longer period, the gauge will eventually return to the
red sector.
Another way to keep a long-term check is to have an 'Aide' leak detector fitted
into the supply line by a gas engineer. This incorporates a small glass sighting
chamber filled with a glycol liquid.
To conduct the test:
1. Switch the gas supply on and turn all appliances off.
2. When a red test button on the top of the detector is depressed, a
regular flow of bubbles in the sighting chamber gives away the fact that gas is
escaping somewhere in the system.
Different again are leak detectors that give an audible warning when a sensor
detects gas. This type of device could be fitted by a competent DIY
motorhome owner. For example, the First Alert electronic alarm warns the
occupants of a leak, using a piercing 85dB siren. The unit only has to be
connected to a 12v DC supply
and should be fixed to a secure base in an appropriate location. LPG is heavier
than air and therefore that means it needs to be fitted low down.
To be
continued................
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