Equipment: This is important when installing and maintaining a gas system
The fact that almost all series-produced ships are equipped with gas cookers emphasises the reliability of these systems. If installed and maintained correctly, a gas system is no more risky in everyday use than other fuels. However, the convenience of use often leads to the necessary minimum maintenance and checks being forgotten. Unlike a paraffin cooker, a leak in the gas pipe is not visible.
Read also:
The international standard ISO 10239 and worksheet G 608 of the German Technical and Scientific Association for Gas and Water (DVGW) regulate how systems for privately used watercraft up to 25 metres in length must be designed. In Germany, regular inspections are also required every two years, not just a check of the initial installation. Although these guidelines are not legally binding, every owner should nevertheless pay attention to them. This is because in the event of a claim, the insurance company will demand information about the gas system and whether it complies with current technical standards. The DVGW specifications serve as a guide.
Store gas on board
Depending on the cylinder format used, either butane in the blue Campingaz cylinders or propane is used on board. Although the two fuels differ in terms of chemistry and price, there are hardly any practical differences. Both the heater and the cooker work with both fuels without any adjustments. Which gas is used on board depends on the space available and the area, as butane and propane have different boiling points. Pure butane only becomes gaseous at temperatures above zero degrees Celsius, while pure propane vaporises at temperatures as low as minus 42 degrees.
This results in an important restriction: butane is not suitable for winter use. Anyone travelling with a blue Campingaz bottle at Easter, for example, could have problems. If the temperature is too low, the gas will no longer vaporise and the heating and cooker will remain cold. As the production of pure butane or propane is expensive, gas mixtures are always used in practice. The blue Campingaz cylinders therefore work down to around minus five degrees, which is sufficient for most sailors. Due to the cold winters, butane is difficult to obtain in Scandinavia, where propane is used.
The gas installation at a glance
Another difference between the boiling points of propane and butane lies in their different thermal expansion. At 20 degrees, a propane-filled cylinder has a pressure of around 7 bar, while a butane-filled cylinder only reaches 1.2 bar. Campingaz cylinders can therefore be thinner-walled and lighter. However, they must never be filled with more propane, as they would not be able to withstand the increase in pressure when heated.
Propane and butane are heavier than air, so escaping gas always collects at the lowest point, in 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 excessive pressure. If it is triggered, the gas must be able to escape to the outside. The gas box therefore needs 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: The container must drain completely without leaving puddles.
Modern boats usually have a corresponding storage space. If you are switching from spirit or petroleum to gas and need to retrofit, you can use ready-made gas boxes.
These are available from 150 euros for a two-kilogram bottle. Alternatively, you can build a customised plywood box and cover it with GRP on the inside. DIY solutions made from a 250 millimetre drain pipe are just as possible. A round gas box can easily be assembled from a piece with a sleeve and a suitable plug. The spare cylinder should also be placed in the gas box, as a defective valve could allow gas to escape even if the cylinders are not connected.
If the bottle locker is installed in a non-sealed locker or other space, it needs a sealed lid. If it is installed in the anchor locker, the connections and bottle must be separated from the anchor gear and there must be a separate drain. However, installation in a damp anchor locker can lead to corrosion of the regulator and bottles. Ignition sources do not belong in the bottle locker. If you have an electric windlass, you should seal the box completely or, better still, install it aft.
Regulate pressure
The pressure in a cylinder varies depending on the ambient temperature. The pressure in propane cylinders is around 7 bar at 20 degrees and only 5.5 bar at 15 degrees. The operating pressure must remain constant so that the cooker and heater work evenly. This is ensured by the regulator, which reduces the pressure to the required 50 or 30 millibars. 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 owners of an old cooker or an old heating system do not have to convert. It is important that only one pressure applies to all consumers on board. Most cookers for yacht use are still available in both versions. The situation is different for gas heaters. The market leader Truma has now decided to only produce appliances with 30 millibar. A defect in the old heater can therefore mean that the entire system has 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.
Not every regulator is suitable for on-board use. Only models approved to G 608 offer corrosion protection inside and out. Cheaper models from the camping sector will not survive the aggressive sea climate for long. A regulator should also have a pressure gauge. Although this does not allow you to measure exactly how much gas is left in the cylinder, it does allow you to check the tightness of the system: Simply close the cylinder valve after boiling and mark the pointer reading. As long as the temperature does not change significantly, the pointer should remain unchanged even after a few hours. However, if the pressure drops, there is a leak and a specialist should be called in.
Gas pipes
In order for the gas to reach the consumer from the cylinder, pipes must be installed. Pipes are stable and require little maintenance. According to the specifications of worksheet G 608, stainless steel or copper pipes are permitted. Steel, which is often used in caravans, is now prohibited. As a rule, copper pipes with a diameter of eight millimetres are used, as they are easy to bend and simple to lay.
Because the material becomes more brittle with every deformation and the risk of breakage increases, the pipe should be bent as little as possible during installation. To avoid breakage due to vibrations, the pipe must be secured with a clamp every 50 centimetres. Either a screw connection can be used at the bulkheads or a cut-out can be sawn into the wood large enough to prevent the pipe from rubbing.
Cutting ring fittings are used for coupling elements. These metal connectors are easy to fit yourself and can be easily opened again. Such an installation cannot do without hoses, as the gas cylinder has to be changed and a gimbal-mounted cooker should swing freely. For this reason, a 40-centimetre medium-pressure hose is permitted in the cylinder box and at the cooker connection. Cardanic cookers often do not work properly with such short hoses. Longer hoses are therefore also permitted as part of the protection of existing equipment. However, these are only available from specialists, as normal ship chandlers usually only offer standard lengths.
Each consumer must have a quick-closing valve that allows it to be disconnected from the rest of the system. This only works if it is easily accessible during operation. It cannot therefore be installed behind the cooker, as is often the case on Scandinavian ships, as the flames of an out-of-control cooker could prevent it from being switched off in an emergency. If the stopcock is located in a cabinet, it should be labelled accordingly.
Even if the valves are used frequently, they usually last the entire life of the boat. As long as no gas is required, the cylinder valve should always remain closed to prevent gas from escaping in the event of a leak. In practice, however, the situation is often different: To save valuable storage space, the gas cylinder is usually placed in the furthest corner. This means that the extraction valve is a long way away. Who is going to crawl around in the cockpit after dinner to close the cylinder, especially if it has to be opened again the next morning for coffee?
Convenient electric remote gas switches offer a solution to this problem, but are no longer permitted on boats. However, old installations are protected. A gas alarm provides additional safety. Although propane and butane are mixed with a characteristic odour, this can easily be masked by other odours. In addition, the gas may not necessarily be noticeable in the saloon, especially if it first accumulates in the bilge. A gas detector also reacts reliably in such cases. These electronic detectors cost between 30 and 150 euros, depending on the model.
Testing the system
If all parts of the system are approved for use on watercraft, there should be nothing to prevent acceptance by an expert. This includes, among other things, a leak test. To do this, an air pump with a pressure gauge is connected instead of the pressure regulator to pressurise the system to 150 millibars. After five minutes, the indicated pressure must remain constant for a further five minutes. This test is more sensitive than searching with a leak spray and detects even the smallest leaks.
After the leak test, all consumers are checked by means of a burning test and the ignition fuses are checked. A maximum of 60 seconds must elapse between the flame going out and the fuse being switched off. With gas cookers, the switching off of this fuse can be recognised by a clicking sound.
If all criteria are met, an entry is made in the gas logbook. This blue booklet is part of every gas system. If you do not have it despite the inspection sticker on the gas box, you should ask the inspector or consult another expert. Approval of the system costs around 60 euros.
Always the right bottle
Whether small or large, blue or grey, made of steel, aluminium or plastic - at first glance, there is a wide range of gas containers to choose from. However, this only applies as long as the journey takes you exclusively through Germany or the gas you have brought with you is sufficient for the entire route. Depending on the space available, the skipper can choose between butane-filled Campingaz cylinders weighing 1.8 and 2.75 kilograms or propane gas cylinders weighing 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 take a liking to the grey propane gas cylinders. Even if they are proprietary containers, both exchange and filling are possible, and the gas only costs around 13 to 17 euros for 5 kilograms. There are only a few exchange stations for the rarer 2- or 3-kilogram formats, but filling is possible throughout Germany.
Plastic cylinders usually have to be filled. They score points due to their low weight, rust-free design and the ability to see the amount of gas from the outside, but there is no testing infrastructure. Pressurised containers must be inspected every ten years. For steel cylinders, this TÜV inspection is organised by the filling station and costs around 15 euros. Some companies organise the inspection free of charge for regular customers or charge a pro rata fee for each filling. Plastic bottles, however, have to be sent to the manufacturer separately.
That leaves the blue Campingaz cylinders provided by many shipyards. These are expensive: one filling costs between 30 and 40 euros for 2.75 kilograms of gas. The advantage, however, is the worldwide security of supply according to the manufacturer. At least in Europe, this statement is largely true, even if there are restrictions in Scandinavia, especially Norway and Sweden - the cylinders cannot be exchanged everywhere. They are also often twice as expensive there as they are here. Anyone expecting an EU standard for gas cylinders and connections will be disappointed.
Travelling abroad is actually a problem with other formats. Although the containers are similar on the outside, each country still has its own standard for connections. In practice, this means that anyone travelling with one of the grey propane gas cylinders commonly used in Germany could run into problems in Denmark when the cylinder is empty.
The usual replacement in Germany is not possible, the only option is to refill. So-called Euro adapter sets are available from accessory dealers for this purpose. However, filling stations are less common than exchange stations and are often not located near marinas. You are also dependent on the goodwill of the filler, as in many countries only bottles that conform to national standards may be filled. There is therefore a risk that the bottle will remain empty.
Online camping sites like reisemobil-international.de offer insights into gas supplies abroad. However, these only contain field reports, which means that a certain residual risk remains.
