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Refilling an LPG cylinder that is not compatible with the local standard



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What is the issue?
Cruising vessels are completely dependant on their stoves for hot food and drinks. This, in turn, is typically underpinned by exchangeable 'liquefied petroleum gas' or 'liquid petroleum gas' (LPG) cylinders. But extended cruising takes vessels to other nations and there is, unfortunately, no worldwide standardisation of gas usage, gas cylinders, or gas valves and fittings as far as LPG is concerned.

Why address this?
At best this means filling non-domestic standard cylinders may only be achieved at a large central gas depot. These are typically difficult to get to and will require an expensive taxi ride if you can convince the driver to transport gas bottles. Typically these depots offer an overnight service which means you have to return the following day to collect the refilled cylinders so that the process will take up two days and two taxi rides. At worst you will not be able to replace your gas cylinders locally, obliging you to invest in a local regulator and cylinder or force a vessel to reroute a passage plan to encompass a large urban area where a gas depot may be found to refill LPG cylinders.

How to address this?
The solution is to refill cylinders by decanting locally available bottles into the vessels cylinders.

This may seem a recklessly dangerous endeavour for many but it is common practice in sailing circles and where done properly presents no issues whatsoever. I admittedly have not carried out this procedure with propane, which is stored under much high pressure, but do it as a matter of course with my lower pressurised butane set up when long-distance sailing and to this day with my present leisure sailing - the differences between propane and butane is discussed in provisioning Experience. It has been a practice detailed by Nigel Calder in the sailing bible 'Boatowners Mechanical and Electrical Manual' Experience up to including the current 4th Edition (2015).


GETTING SET-UP FOR LPG DECANTING

You will need to get is the connector(s) (not regulators) that fit the onboard bottle(s). A length of high-pressure pipe, intended to be fitted before the regulator (not the type that you would fit between the regulator and a cooker) will also be required and some sturdy stainless steel hose clips.

UK M20 Butane Pigtail Hose
Photo: Courtesy of PLS

A good way to start this process is to buy a local 'pigtail adapter' designed to attach LPG bottles together or to a bulkhead regulator. These will have at least one usable connector well sealed onto a length of high-pressure pipe. Pigtails all come with anti-syphon valves fitted internally so as not to allow gas/liquid to flow unless it is connected to a regulator. This will prevent the transfer operation so it will have to be removed for any decanting work to take place. Some can be simply unscrewed and removed others may have to be drilled out. This is easily achieved in the case of the latter as the fittings are usually made from brass which is a relatively soft material. Try get the longest hose pigtail avialable to provide the most set up scope.

The next essential step before any refiling takes place is to record the total weight of the bottle. This should be stamped or printed on the bottle and/or easily obtained from a web search. The three numbers tare weight (the weight of the cylinder), contents weight (the recommended LPG capacity weight) and total weight (the overall weight of a full container). The tare weight will be stamped on the base ring preceded by the letter 'T'.

Let me illustrate this with the Campingaz 907 refillable cylinder, a very expensive means of buying gas, that fit's my Hanse's gas locker. Its specifications state a total weight is 6.42 kg made up of 2.72 kg of butane LPG and a tare or cylinder weight is 3.7 kg. But the empty weight of the cylinder can vary. I have seen Campingaz 907's of 3.50, 3.60 and 3.70 but the carrying capacity for this type of bottle will always be the 2.72 kg. So, for instance, and as with the case of my current bottle, the tare weight is 3.68 kg so when it is nominally full it should weigh 3.68 + 2.72 = 6.40 kg. You should detail this for all the cylinders and make sure it is clearly written on the outside. Because once you know the total weight of the bottle you know when to stop filling them.

The biggest potential problem with this process is that you overfill the bottles. A gas head above the liquid in your cylinder is absolutely essential and that is why you do not run your cooker etc with the cylinder on its side or upside down. It is why the supply valve is at the top of the cylinder, rather than the bottom. If a cylinder is completely filled with liquid and the ambient temperature rises expanding the liquid more than the bottle can contain, it could rupture the bottle and lead to an explosion. Therefore, cylinders should never be filled beyond 80% or beyond 70% in the tropics as an added measure of safety to allow for expansion should they be left in direct sunlight.

In practice, you will most likely find it difficult to overfill bottles especially after the first decant has been taken from a large bottle. Many bottles have a device that prevents them from being over-filled but I believe that Campingaz, for example, does not. So if filling from a large bottle to a small, knowing the appropriate weight of gas to fill and check-weighing the bottle whilst it is being filled is essential if you want to get the maximum possible fill.

Gas decanting kit for our circumnavigation
Photo: Mark Murray


With the connector(s) required for your own bottle(s), their weight(s) recorded and some high-pressure hose pipe, all that is required is a sturdy pair of gloves so to protect your hands from condensation burns. Plus of course the occasional purchase of a local connector for the local standard.


DECANTING PROCESS

Most retail LPG suppliers operate on a contract and exchange basis but shops in yachting areas are typically happy to allow you to take out a local bottle for a short while without a contract provided you cover the cost of the bottle with a deposit should it not be returned empty.

When you arrive at a destination that has an incompatible gas standard find out the connector type that fits a decent sized bottle that makes it economically efficient to purchase gas. Buy it and securely fit the local valve connector to the opposite end of the LPG hosepipe to your own connector and fastening it down tight with a hose-clip. Make certain that the connections on both ends of the hose are secure and there is zero possibility of leaks. The decanting process is achieved then by the following steps:

  • 1/ Go to a remote well-ventilated area with a potential hoist point or an elevated standing point where there are no people or naked flames. A quiet beach with a tree is ideal.

  • 2/ Attach the local connector to the local cylinder with its valve closed and tighten.

  • 3/ Attaching the opposite end into the empty boat cylinder, again with its valve closed and tighten down to join the two bottles.

  • 4/ Connect a line to the bottom of the full local doner bottle and hang it upside down, or if an elevated standing point is available invert it and set it on standing upside down.

  • 5/ Stand the vessel's empty cylinder upright on the ground beneath as normal and place a scales underneath.

  • 6/ Put on the protective gloves and open the valve on the top donor cylinder. As the pressurised gas is in a liquid form it will pour down the pipe. Here Nigel Calder's bibe on this subject the 'Boatowners Mechanical and Electrical Manual 4th Edition (2015)' Experience recommends an additional step that I admittedly have never taken and caused me no issues in the past. This is a step to keep air out of the system by [Loosely attach the connecting hose to the cylinder being refilled, and crack the valve on the full cylinder just enough to blow off a little gas at the loose connection: then snug up the connection (this purges the hose of air)].

  • 7/The pressure will begin to immediately equalise between both cylinders pouring the liquid gas down into the donor bottle. Then the proper weight determines the liquid level. Once the scales arrive at the appropriate weight turn off the valve on the upper cylinder. If you accidentally exceeded the weight just close both valves reverse the process, lift the receiving cylinder up and lower the downer, and open the valves again for a while. If, on the other hand, you are not too bothered with squeezing every ounce into a bottle and you can spread the load just give the bottle a shake every so often to see how it is filling as it nears the top and the sloshing about becomes increasingly reduced just shut it down well inside the max fill capability. This is what we tended to do as we had ample capacity to store the contents.

  • 8/Allow a few minutes for the hose to drain down, then close the valve on the lower cylinder. This will drain any liquid from the connecting pipe and replace it with gas, so that when you turn off the valves and disconnect them only a small amount of gas will escape. Check that there are no naked flames before the connectors are disconnected. Once you are absolutely safe undo the fitting on the lower cylinder and there should be the briefest equalising hiss and then smell of the gas trapped in the connecting hose pipe bleeding out. Remove the connector from the receiving bottle and place the safety cap securely over it.

  • 9/ Replace the bottom cylinder with the next empty, reopen the valves repeating the process. After the first refills and the top cylinders. As the donor is drained the pressure reduces and the flow slows down. The latter fills can be slow, depending on the valve, but typical, it should be complete in about thirty minutes to an hour. If you are drawing of the last of the gas from the doner tank it may take a long time. Continue until the top local cylinder is exhausted or you have run out of capacity to contain it.

  • 10/ To dismantle close off both valves as described above bleed the residual gas from the pipe. Disconnect both ends and lower the emptied cylinder.

  • 11/ Return local cylinder to the vendor for the deposit.

That all there is to the process. Some people go to extraordinary lengths to get every ounce out of a bottle by expanding the gas in the supply bottle and contracting the fluid in the receiving bottle in order to increase the fill. For example keeping the (receiving) bottle tightly wrapped in a towel, wet and in the shade to keep it cool, whilst keeping the elevated full bottle (donor) in the sun before and during a decanting. Some even go as far as placing the receiving cylinder in iced water to cool the butane.

I would not recommend any of this. It vastly overcomplicates a very simple process at best and may lead to dangerous overfilling. If you want to get the most out of a donor bottle just add another cylinder to your stockpile and only partially fill it. Getting the last ½ kg of LPG is not worth all the trouble or the risk of overfilling a cylinder. However, I have to say, you are doing this at your own risk and I take no responsibility for anyone who has problem or injuries as a result of this practice. I in no way accept iability.

With thanks to:
Mark Murray, S/Y Stephany B




Decanting LPG Propane


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Add your review or comment:

Witold Miedzybrodzki wrote this review on Oct 15th 2009:
RE. Refilling butane gas bottles when your cylinder is not compatible with the local standard I am a Process Engineer/ HSE Adviser in the oil industry (nor am I a yachtsman. I am not an expert on filling LPG gas bottles but feel a bit concerned about this article. How do you ensure the bottle is not completely liquid filled? If it is completely liquid filled with no gas space then, because of ambient temperature changes or sunlight, the pressure can increase very quickly (30 mins) to such a level that the bottle will fail catastrophically. These are not theoretical but are actual events that happen quite often in my industry. I suggest you discuss this with a bottled gas expert before doing it or you and your crew may get killed or badly burned if you do this. Witold

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