Cooking, grilling, heating: How to install a liquefied petroleum gas system
The fact that there are hardly any production boats without a gas cooker speaks in favour of the reliability of the systems. In everyday operation, a properly installed and maintained gas system is no more dangerous than other fuels. However, the ease of use often makes people forget that a minimum level of maintenance and control is necessary for safe operation. Unlike a paraffin cooker, a leaking gas pipe cannot be recognised with the naked eye. For privately used watercraft up to 25 metres in length, the international standard ISO 10239 and, in Germany, worksheet G 608 of the German Technical and Scientific Association for Gas and Water (DVGW for short) regulate what the system must look like. German regulations not only govern the initial installation, but also require repeat inspections every two years. However, these specifications are not legally binding.
In theory, no skipper has to worry about it and can install and operate a system as he pleases. However, this tactic only works as long as no damage occurs, because then at the latest the insurance company will ask about the gas system and whether it is state of the art. The DVGW specifications serve as a guideline here.
Warehousing
Depending on the Bottle format either butane - in the blue Campingaz bottles - or propane is used on board. Although the two fuels differ chemically and in price, in practice they hardly differ at all. Both the heater and the cooker run on both fuels without any changes having to be made. Which of the gases is used on board is a question of space and area. This is because butane and propane have different boiling points. While pure butane only becomes gaseous at temperatures above zero degrees Celsius, pure propane already vaporises when it gets warmer than minus 42 degrees, which is helpful in winter.
This results in a decisive limitation: butane is not suitable for winter use. For example, anyone travelling with a blue Campingaz bottle at Easter when it is freezing can run into problems. If it gets too cold, the gas will no longer vaporise and the heating and cooker will remain cold. The production of pure butane or propane is complex, so in practice you always have to deal with gas mixtures. The blue Campingaz cylinders therefore work down to around minus five degrees. That's enough for most boaters. However, due to the cold winters, butane is difficult to obtain in Scandinavia, where people rely on propane.
Thermal expansions
Another consequence of the different boiling points of the two gases is the different thermal expansions. While a cylinder filled with propane is pressurised to around 7 bar at 20 degrees, a butane cylinder is only pressurised to 1.2 bar. Campingaz cylinders can therefore be thinner-walled and therefore lighter. However, they must never be filled with a higher proportion of propane, as they would not be able to withstand the rapidly increasing pressure when heated.
Both butane and propane are heavier than air, so escaping gas always collects at the lowest point, in the case of boats in the bilge. The container should therefore be placed in a gas-tight box. The regulator on the cylinder has a safety valve that protects the system from damage caused by excessive pressure. If it blows off, the gas must be able to flow outboard. For this reason, the gas locker must have a drain with a diameter of at least 19 millimetres at the lowest point, which ends above the waterline. This can be checked with a bail of water in the box. The tank must run completely empty without any puddles remaining.
Modern boats usually already have a corresponding storage space. If you are switching from spirit or petroleum and need to retrofit, you can fall back on ready-made gas boxes. These are available at prices starting at 150 euros for a two-kilogram bottle. Alternatively, you can build a customised plywood box and then cover it with GRP on the inside. DIY solutions made from 250 millimetre diameter drainage pipes are also possible. You can easily assemble a round gas box yourself from a piece with a sleeve and a suitable plug. Incidentally, the spare cylinder should also be in the gas box, because even if it is not connected, gas can escape if the valve is defective.
If the bottle locker is installed in the forecastle locker or another space that is not sealed off from the inside of the ship, it must have a tight lid. If it is installed in the anchor locker, it is sufficient if the connections and bottle are separated from the anchor gear and there is a separate drain. However, installation in a frequently damp anchor locker can lead to severe corrosion of the pressure regulator and bottles. There must also be no ignition sources in the bottle locker. So if you have an electric windlass, you should close the box completely or, better still, install it aft.
Pressure in the LPG system
The pressure in the cylinder varies depending on the ambient temperature. Propane cylinders, for example, have a pressure of around 7 bar at 20 degrees, but only 5.5 bar at 15 degrees. The operating pressure must be constant so that the cooker and heater run evenly. This is ensured by the regulator. It simultaneously reduces the pressure to the 50 or 30 millibars required for the appliances. Until 1996, 50 millibar systems were prescribed in Germany, but in the meantime an international agreement has been reached on 30 millibars. However, 50 millibars is still permitted. This means that anyone with an old cooker or an old heating system does not have to convert. However, only one pressure may be used for all consumers on board. Most cookers for yacht use are still available in both versions. Nevertheless, you should pay attention to this. The situation is different for gas heaters. Market leader Truma has now switched to producing only 30 millibar appliances. A defect in the old heater can therefore force the entire system to be converted.
The pressure supplied by the regulator is indicated by the colour. 50 millibar models are labelled orange and 30 millibar models yellow. Pressure regulators are wearing parts and must be replaced every six years.
However, not every regulator is suitable for use on board. Only models approved to G 608 are protected against corrosion both inside and out. Cheaper models from camping accessories will not last long in an aggressive sea climate. The regulator should also have a pressure gauge. Although this does not allow you to determine how much gas is left in the cylinder, as is often claimed, you can check the tightness of the system at any time: Simply turn off the cylinder valve after boiling and mark the pointer reading. As long as the temperature does not change significantly, the pointer should still be in the same position after a few hours. However, if the pressure has dropped, the system is leaking and a specialist should be consulted.
The gas installation at a glance
Instructions for installing the LPG system
To get the gas from the cylinder to the consumer, pipes have to be laid. Pipes are robust and low-maintenance. According to the rules of worksheet G 608, stainless steel or copper pipes are permitted. Steel, as is common in caravans, is no longer permitted. Copper pipes with a diameter of eight millimetres are usually used; they are easy to bend and easy to lay. As the material becomes more brittle with every deformation, increasing the risk of breakage, the pipe should be bent back and forth as little as possible during installation. To prevent vibration fractures, the pipe must also be supported with a clamp every 50 centimetres. At the bulkheads, either a screw connection is used or a cut-out is sawn into the wood large enough to prevent the pipe from rubbing against the walls or bulkheads.
Cutting ring fittings are used as coupling elements. These metal connectors are easy to fit yourself and can be easily opened again. This type of installation cannot do completely without hoses, as the gas cylinder needs to be changed and the cooker, which may be gimballed, needs to be able to swing freely. For this reason, a 40-centimetre-long medium-pressure hose is permitted in the cylinder box and at the cooker connection. However, gimballed cookers often do not work properly with such short feeds. Longer hoses are therefore also possible as part of the protection of existing equipment. However, these can only be obtained from a specialist; the usual ship chandlers only offer standard lengths. Each consumer must be able to be disconnected from the rest of the system using a quick-action shut-off valve. However, this only works if it is accessible during operation. It must therefore not be installed behind the cooker, as is usual on many Scandinavian ships. Otherwise, in case of doubt, the flames from the out-of-control cooker will prevent the emergency shutdown. If the stopcock is located in a cupboard or cabinet, it must be labelled accordingly. Even if the valves are moved frequently, they will normally last the life of the boat. As long as no gas is being used, the cylinder valve should always be closed so that no gas can escape even if there is a leak in the system.
In practice, however, the situation is often different: to avoid taking up valuable storage space, the gas cylinder is usually installed in the furthest corner. However, this also means that the extraction valve is a long way away. And who wants to crawl around the cockpit after dinner and close the cylinder, especially if it has to be turned on again for the coffee water the next morning? Convenient electric remote gas switches solve this dilemma, but are no longer permitted on boats. However, old installations are protected. A gas alarm provides even more safety. Although propane and butane are mixed with a characteristic fragrance, this can easily be masked by other odours. In addition, the gas does not necessarily have to be odourless in the saloon once it has collected in the bilge. A gas alarm also works reliably in such situations. Depending on the model, these electronic sniffers cost between 30 and 150 euros.
Exam question
If all components of the system are approved for use on watercraft, nothing should stand in the way of acceptance by an expert. Among other things, this includes a leak test. For this purpose, an air pump with a pressure gauge is connected instead of the pressure regulator and an overpressure of 150 millibars is applied to the system. After waiting five minutes, the pressure displayed must remain constant for a further five minutes. This test is much more sensitive than searching with a leak spray and reveals even the smallest leaks.
The leak test is followed by a burn test of all consumers and a check of the ignition fuses. A maximum of 60 seconds may elapse between the flame going out and the fuse being switched off. If all criteria are met, an entry is made in the gas logbook. This blue booklet is part of every gas system. Anyone who does not have it despite the inspection sticker on the gas box should ask the inspector or consult another expert.
Always the right bottle
Small or large, blue or grey, steel, aluminium or plastic - at first glance, there are various gas containers to choose from. However, this only applies as long as the trip is only travelling through Germany or the volume of gas carried is sufficient for the entire trip. Depending on the space available, the skipper can choose between Campingaz cylinders filled with butane with a capacity of 1.8 and 2.75 kilograms or propane gas cylinders in the sizes 2, 3, 5 or 11 kilograms. There are also lightweight 6 and 11-kilogram Alugas cylinders and plastic cylinders with 2 and 5-kilogram fillings.
A glance at the prices quickly makes buyers flirt with the grey propane cylinders. Although they are proprietary containers, both exchange and filling are possible, and the gas costs just 13 to 17 euros for 5 kilograms. With the rarer 2- or 3-kilogram formats, you only have a few exchange stations to choose from, but filling is possible throughout Germany. Plastic bottles usually have to be filled. Although they have the advantage that they are very light, do not corrode and the amount of gas can be recognised from the outside at any time, there is no testing infrastructure. The pressurised containers must be inspected every ten years. In the case of steel cylinders, this TÜV inspection is organised by the filling station and costs around 15 euros. Some companies also carry out the inspection free of charge for their regular customers or a pro rata fee is charged for each filling. Plastic bottles have to be sent to the manufacturer separately.
That leaves the blue Campingaz cylinders provided by many shipyards. Here it gets expensive: one filling costs between 30 and 40 euros for 2.75 kilograms of gas. Your advantage: According to the manufacturer, the supply is guaranteed worldwide. This statement is true for Europe at least, albeit with restrictions - in Scandinavia, especially in Norway and Sweden, the cylinders cannot be exchanged everywhere. You also have to dig deep into your pockets. Replacement is easily twice as expensive there as it is here. Anyone expecting that there will be an EU standard for gas cylinders and connections as standardisation continues to progress will be disappointed.
Travelling abroad is actually problematic for all other formats. Although the containers are similar on the outside, each country still annoyingly relies on its own standard for the connections. In practice, this means that anyone travelling with one of the grey propane cylinders commonly used in Germany will have a problem in Denmark as soon as the bottle is empty.
The usual exchange procedure in Germany is not possible, so the only option is to refill. So-called Euro adapter sets are available in the accessories trade. However, refilling stations are rarer than exchange opportunities and usually not close to the marina. And you are at the mercy of the bottler: In many countries, only bottles that comply with the national standard may actually be filled. And then there is a risk that the bottle will remain empty. An overview of gas supplies abroad can be found on various camping sites on the Internet, for example here. However, only experience reports can be found there - a residual risk remains.
