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Fixed fuel systems.

Fuel System Maintenance

A diesel fuel system is a miracle of modern technology. It must meter quantities of fuel as small as a few millionths of a gallon, raise this to a pressure as high as 5,000 psi, and inject it into the engine at a moment in time. Given the close tolerances in the machining of all fuel injection pumps and injectors, a minuscule piece of dirt can do extensive damage. If right from the start the owner gets rid of dirt and water in the fuel, then 90 percent of potential engine problems can be avoided.

"Give a diesel engine clean fuel and it will run forever." This is less of an exaggeration than you might think.

Repair statistics show that 90% of diesel engine problems stem from contaminated fuel. The promise of eliminating 9 out of 10 potential failures should put fuel-system maintenance at the top of your list.

Start With Clean Fuel

Don't make your task more difficult by taking on contaminated fuel. The bad things that happen to diesel fuel inside your tank also occur inside the supplier's storage tanks. That isn't a problem for you if the fuel is efficiently filtered on the way to the nozzle. If you have any doubts about the cleanliness of the fuel, pump some into a clean glass jar and let it sit a few minutes. Water and dirt will settle to the bottom. If you see either, filter the fuel before it goes into the tank, or better yet, buy your fuel somewhere else!

Keep Out Water

Petrol engines can ingest a certain amount of water with the fuel without serious consequences, but if a single droplet of water in diesel fuel makes it all the way to the cylinder, the sudden steaming of the water can blow the tip right off an injector. This is the reason for having a water-separating filter, but too much water in the fuel can overwhelm this filter.

If you took aboard dry fuel, shouldn't it stay dry inside your tank? No. Contaminated fuel is only one way water gets into the fuel aboard boats. It also leaks in around the fill cap, it is occasionally driven in through a flooded vent fitting, and it forms inside the tank as condensation.

By far the most common cause of contaminated boat tanks are deck fill caps that leak. Most of these things are stupidly mounted flat on decks which may puddle with water. The cap has a tiny little O-ring that is supposed to seal and keep water out. DOES IT? I wouldn't depend on one of these things unless I could prove that it doesn't leak. Check the condition of the o-ring and weather it is sealing. One way to check positively is to clean the o-ring seat thoroughly; next apply some black or any colour paint to the o-ring and screw the cap in place, tight. Then remove it and see if the paint has been completely transferred to the ring seat. If not, you now know where the problem is.

Another problem is the simple failure to seat the cap fully after refuelling. This actually happens a lot, so check to see if the cap is loose. Side-deck deck-fills, especially on sailboats, can spend a lot of time under water and are often the primary source of water contamination. If the cap's seal isn't airtight, replace the gasket or the fitting.

Improperly located fuel tank vent fittings are one of the top causes of water getting into tanks. When this is the cause, if you are a salt water boater, then it will be salt water in your tank. A fuel tank vent fitting on the side of the hull should be angled down and aft ward. If angled in any other direction, you've got a problem that needs fixing. Watch out for deteriorated plastic and zinc alloy fittings; some of these things deteriorate incredibly fast. The vent line should have a riser loop on the inside. That is, it travels upward first, then downward. If not, that is another potential problem.

Where is the tank's vent fitting? If it is on the side of the hull, deep heeling or heavy rolling might submerge it, admitting water into the tank. If it is through the transom, a following sea might drive water back into the tank. Even when it is located in the cockpit or on the cabin side an errant wave might engulf it. Water also condenses out of the air inside the tank. Due to the daily heating/cooling cycle, a small amount of moisture will condense out of the air every day. The more air in the tank, the more potential for condensation, so it is a good idea to keep tanks topped off, especially while the boat is not being used.

Prevent Algae

Like mold on bread, algae and fungi can thrive inside fuel tanks. These microbes require both fuel and water, so the drier the fuel, the smaller your algae problem is likely to be. However, keeping all water out of the fuel is improbable, so diesel fuel should always be treated with a biocide to prevent the growth of microbes. Avoid products that contain alcohol, which attacks O-rings and other rubber parts in the fuel system.

No matter how meticulous you are about the fuel you take aboard, dirt, water, and microbes-dead or alive-accumulate in the bottom of the tank over time. They may seem harmless enough just lying there, but the first time you are motoring in bumpy conditions, they get churned up and find their way to the fuel pick-up, either in small amounts or in big gulps. If you are lucky, this contamination simply plugs your primary filter and starves the engine of fuel until it dies-hopefully not at some critical moment. If you are unlucky, some of this debris finds a way past the filters and damages the injector pump or the engine. It is advisable to clean out the tank periodically. How often depends on fuel quality and even tank material, but every couple of years you should at least draw some fuel from the very bottom of the tank to check for water and/or sediment. You cannot do this through the pick-up tube feeding the engine because it is an inch or so above the bottom. If the tank doesn't have a drain fitting or a clean-out port, you will need to find some other way to get a suction hose to the bottom. Mobile services are also available that draw all the fuel out of your tank and circulate it through a filtration system. This is known as "polishing" the fuel, and done properly it removes the majority of the sediment from the tank.

Deterioration

Most permanent fuel tanks are housed deep in the bilge where rapid changes in temperatures cause a fair amount of sweating on the tank exterior and condensation inside. The fuel filter and water separator will remove the internal condensation, but the exterior of the tank relies on air moving through the bilge to keep its surfaces dry. Welded edges on metal tanks are susceptible to crevice corrosion. Threaded and welded fittings for draw and fill lines are other trouble spots. Unfortunately, a metal tank’s weakest links are the undersides and outboard side, which are difficult and in some cases impossible to see. Another troublesome situation is when a metal fuel tank is encased in foam. The idea is the foam will help anchor the tank in place and insulate it from moisture. In reality, the opposite is true and over time vibration and movement cause the foam to separate from the metal. The expansion serves as a gateway for moisture to wick its way between the foam and the tank where it often is trapped. Bottom line is that if your boat is more than 10 years old and the fuel tank installation is similar to the scenario described above, you need to take a long hard look at its condition sooner rather than later.

Fuel Lines

Proper fuel lines last a long time, but improper lines can shed internally and contribute to fuel contamination. Metal fuel lines are less susceptible to chemical deterioration, but the supply line connected to the engine must never be metal because movement and vibration will eventually cause the rigid line to crack. Flexible hose is unaffected by vibration and ideal for boat use. Vent and fill hoses should exhibit an uninterrupted drop to the tank; any dip that allows fuel to stand risks hose deterioration and fuel contamination.

Filters

There is a reason that the fuel filter mounted on a diesel engine is called the secondary filter. The engine manufacturer expects this filter to deal only with contamination small enough to have passed through the primary filter. Every diesel engine must have both a primary and a secondary filter, and the primary filter must remove water from the fuel. I prefer a primary filter with a clear sediment bowl (although, if this is not a fire resistant type it can cause problems with passing BSS examinations), which should be inspected daily. Water in the bowl is visible evidence of water in the tank. If you need to drain the bowl (it has a plug just for this function) more often than every 100 engine hours, the tank needs cleaning.

Filters should be changed when they are dirty, but unless your primary filter is fitted with a vacuum gauge (which reveals the extent of restriction), you will need to change the element at some regular engine-hours interval. Your engine manual should specify. In recognition that the primary filter captures most of the contaminants, it is a common and generally acceptable practice to change the secondary filter element at every other primary filter change.

Therefore boats obliged to meet BSS requirements will need to comply with the following:

• All permanently installed fuel systems and fixed engines must be designed, installed and maintained in a way that minimises the risks of explosion, or of fire starting or spreading.
• Fuel filling arrangements must prevent any overflow from entering the interior of the vessel.
• All fuel filling points must clearly identify the fuel in use.
• Marking must be provided to identify the location of fuel system emergency shut-off devices, or their means of operation, which are not in open view.
• All permanently installed fuel systems must be designed, installed and maintained to ensure fuel-tight integrity.
• All permanently installed fuel tanks and fuel system connections must be accessible for inspection.
• The pressure systems of steam-powered installations must have a current inspection certificate issued by a recognised competent person.

Filling Pipes Filling pipes shall be taken to deck level or so arranged as to ensure that any fuel overflowing will not be discharged into any part of the vessel including the bilges.

Objective

The objective of this standard is to avoid any accumulation of fuel inside a boat as a result of overfilling the fuel tank. Whether the cause is overfilling, blockages, restrictions or blowbacks, there is a risk that fuel could find its way into the interior of the boat if its fuel-filling points have no means of preventing this. A small amount of leaked fuel can contribute to the cause or a spread of a fire. Leaked petrol could cause an explosion. This is the risk being addressed in this section.

Installation & Design

The objective, which is particularly pertinent when tanks are out of sight of the person carrying out the filling operation, can be achieved if the filler cap is positioned so that: (see example images below).

The position of the filling connection and the camber (slope) of the deck may be such that fuel overflowing can still be discharged into the vessel even though the filler pipe is taken to deck level, therefore installing the filler pipe to deck level is not, by itself, sufficient. Preventing overflowing fuel from entering any part of the vessel takes precedence over the installation of the filling pipe to deck level.

The design must ensure that there is no risk of unseen spillage during fueling operations.

Notes – This requirement does not apply to the following provided there is no risk of unseen spillage:

Open vessels, such as RIBs (Rigid Inflatable Boats) with a continuous deck or sole that is fuel tight to the interior of the vessel and bilge spaces, meet this requirement. Diesel fuel fillers onto self-draining cockpits meet this requirement if they have…

The objective of this standard is to ensure that fuel can be safely loaded onto the boat without blowback and spillage and that the fuel filling system is free of leaks.

Its good installation practice that all joints and connections are ready accessible. This means they must be capable of being reached for inspection, removal or maintenance without the removal of permanent craft structure but it may be necessary to use tools or remove access panels or remove any items of portable equipment stowed in places intended for storage of portable equipment in order to gain access.

Filling pipe

The internal diameter of the filling pipe should be at least 31.5mm throughout its length.

The outside diameter of this pipe would be approximately 50mm.

If the pipe has a diameter less than this “blowback” of fuel could occur or the filling nozzle may not enter properly.

It is important that the bore of the pipe cannot become restricted either by design or by accident.

A non-kinking pipe will prevent the walls of the pipe from collapsing and thus restricting the bore when it is necessary for the pipe to be bent at an angle or any object comes into accidental contact with the pipe.

Check that the flexible filling pipe cannot be compressed by squeezing it by hand.

This is an upgraded standard introduced in April 2005: Fuel filling lines must be ‘self-draining’ i.e. fall continuously from the filling point to the fuel tank connection so that fuel is not retained. Fuel filling lines must not be kinked or restricted.

Damaged or deteriorating fuel filling lines could fail and result in a leak that could form a potential fire, explosion, or pollution hazard depending on the fuel used. In the case of petrol, hose not designed specifically for that fuel can fail rapidly. Indeed all fuel oils can ‘attack’ unsuitable materials.

The material of the pipe must not be unduly permeable to the fuel used or react chemically with the fuel leading to deterioration and leaks.

In use, the material must be resistant to damage deterioration resulting in corrosion, hardening, brittleness, shrinkage and cracking. Any localised or undue softening of flexible hoses may be a sign of an adverse reaction affecting the inner wall which has not yet reached the outer layers.

Fuel filling hose must be marked as suitable for the fuel in use or supported by an appropriate declaration.

Note: However since April 2005 – diesel filling hose in good condition may be accepted without marking or declaration provided it can be examined over its entire length. Enough suitably marked diesel filling hose, or enough petrol hose, must be accessible to make a reasonable assessment as to the hose’s general condition.

It is not a requirement under the BSS for diesel filler hose to be fire resistant but it is strongly recommended.

Best Practice: We recommend that you use hoses marked with BS EN ISO 7840 although hoses marked with SAE J 1527, DIN 4798 or marked with the type of fuel in use are acceptable. We recommend the use of double clamps on a filling hose used for petrol.

Metal Filling pipes must be examined carefully to ensure that the pipe and its connections show no signs of cracking or slackness etc caused by metal fatigue due to vibration.

Deck and fuel filling connections All deck and fuel filling connections shall be situated as to minimise the risk of cross contamination and shall be clearly marked on the deck fittings or immediately beside then indicating the purpose of each connection and, in the case of fuel connections, the exact type of fuel.

Objective

The objective of this standard is to prevent fuels being incorrectly loaded and contacting systems and components which are not suitable.

Cross contamination may be prevented by:

The purpose of each deck connection shall be clearly labelled/marked. This marking is to be either on the fitting, or cap or immediately beside it. Fuel connections must be marked with the exact type of fuel used. The label can be made of plastic, (but not embossed tape) and can be painted on.

Connections marked with the word FUEL or GAS are not acceptable.

Filling and discharge points may be marked with the internationally accepted symbol (eg ISO 11192 and ISO8099).

Clearly marked means that the marking is in direct view of any person using the connection.

It is recommended that lettering is:

The specific fuel type in use must be correctly and clearly marked on or adjacent to all fuel filling points:

We recommend that other disused deck connections, if not blanked off, also be marked clearly to prevent cross contamination and spillage.

Note – Unused fuel filling points must be permanently disabled to such an extent that it would require the use of tools to remove the disabling method. The use of a suitable proprietary adhesive to secure filling point caps or plugs in place etc. meets this requirement.

Vent pipes A vent pipe of minimum practicable length with an internal diameter of not less than 12mm shall be fitted at the highest point of every fuel tank and connected with leak proof joints. The material used shall be non kinking and suitable for use with the fuel concerned.

The objective of this standard is to ensure that fuel tanks are effectively vented to prevent over and under pressure and blow backs during filling operations. Potentially dangerous and polluting fuel blow-backs are known to happen during refilling. The tank also needs to be able to ‘breathe’ to help the supply of fuel to the engine or appliance. Temperature changes cause the volume of fuel to expand and contract.

Venting needs to be effective at all levels of fuel in the tank. A vent line can also be a filling line, or an overflow line, and the requirement for a vent does not apply to small auxiliary tanks with a vented filling cap on the tank.

The vent pipe is required to extend to a height equal to or greater than the level of the filling connection.

It may be necessary to incorporate an inverted “U” bend or swan’s neck in the pipe to prevent ingress of water and debris which could result in contamination of the fuel or blockage of the vent pipe.

Note – where the filling point is mounted on a deck a swan neck in the vent line to the underside of the deck meets this requirement.

If fuel were retained in the pipe it would no longer act as a vent pipe as there would be no clear passage for the air venting from the tank. The category would also change to that of a fuel pipe permanently charged with fuel.

The route taken by a flexible vent pipe is to take into account of anything which may damage the pipe e.g. heat sources and the need for access to the connections.

In general, every fuel tank must have an individual and separate vent line. However, a vent is not required where day tanks are fitted with an overflow pipe which returns fuel back to the main storage tank. The hole in the filler cap of small capacity tanks of no more than 27 litres is deemed to meet this requirement. Examples include those found on Stuart Turner petrol tanks, Yanmar engines’ close-coupled tanks or diesel tanks supplying appliances.

Vent lines must be connected to the top of the tank and be ‘selfdraining’, i.e. fall continuously from the vent outlet to the tank, or, where a swan neck is installed, from the top of the swan neck down to the vent outlet and the fuel tank connection.

On tanks over 27 litres visually check that the vent is:

However, we recommend fitting a vent line of at least 12mm (1/2 in) internal diameter fitted which meets with international standards.

Notes – The internal diameter may be verified by measuring the outside diameter and estimating wall thickness. The following are approximate indications, copper 11.5mm (1/2 in), steel 12.5mm (1/2 in), hose 15.5mm (5/8 in).

The vent pipe is to be fitted at the highest point of the fuel tank to minimise the risk of creating a space at the top of the tank where fuel vapour could accumulate.

Visually and manually check vent pipes for leaking fuel at joints.

It is important that the bore of the pipe cannot become restricted either by design or by accident. A non kinking pipe will prevent the walls of the pipe from collapsing and thus restricting the bore when the hose is bent or any object comes into accidental contact with the pipe.

This standard has been recently adjusted, and since April 2005 Diesel tank vent hose (not petrol) in good condition may be accepted without marking or declaration provided it can be examined over its entire length. However we highly recommend suitability is determined by the long-term performance of the pipe and its condition in use, and we suggest the material of the pipe should not be unduly permeable to the fuel used nor react chemically with the fuel leading to deterioration and leaks.

We suggest the material should be resistant to damage and deterioration resulting in corrosion, hardening, brittleness, shrinkage and cracking and any localised or undue softening of flexible hoses may be a sign of an adverse reaction affecting the inner wall which has not yet reached the outer layers.

Best practice

We recommend that you use hoses marked with BS EN ISO 7840 although hoses marked with SAE J 1527, DIN 4798 or marked with the type of fuel in use are acceptable.

Petrol filling pipes which are not marked but supported by a declaration of suitability from the manufacturer, supplier or boat builder are acceptable. Examiners may also accept petrol filling hose which they recognise as being compliant.

Metal vent pipes must be examined carefully to ensure that the pipe and its connections show no signs of deterioration or slackness. Soldered joints may be used but their use is not encouraged.

Vent pipe outlets and flame arrestors Vent pipe outlets shall be fitted in a position where no danger will be incurred from escaping fuel or vapour. Each opening shall be furnished with an effective wire gauze diaphragm flame arrestor of non-corrosive material

The objective of this standard is to ensure that any vapours emerging from the vent opening do not give rise to an explosion hazard. Fuel vapours exhaust from the vent. If ignited, a flame close to, or at the end of, the vent line, has the potential to flash back into the fuel tank. An unprotected vent outlet could become blocked by debris or insects, etc.

It is important, and good safety practice to ensure that the vent pipes terminal is not in a position where there is a risk of danger. The international standard recommends that the vent pipe terminals be in the open air and at least 400mm from any ventilation openings where vapour may enter enclosed cabin spaces. Vent pipe terminals must also be clear of any potential source of ignition and 400mm is an appropriate guideline for a minium separation.

Diesel, paraffin or other fuel-oils escaping onto a source of ignition would create a fire hazard. There is even greater risk with petrol as the vent will exhaust highly flammable vapours regularly.

It is fundamental marine engineering practice to install a flame arrester on the outlet of all vent pipes. This device prevents the passage of flame by means of small openings, convoluted flame paths or by ensuring that the temperature of the side which is not exposed to flame does not reach a high enough temperature to ignite a flammable vapour mix.

In the UK it has been historically recommended practice to install a copper or brass gauze with a mesh size of 28 wires per inch. However, the ISO does not have any recommendation for gauze size and requires only that an effective flame arrestor is fitted. For the purpose of the BSS therefore any proprietary flame arrestor will be accepted.

What ever type of flame arrestor is used it is important to ensure that the openings in the flame arrestor body do not restrict the passage of either by design or by blockage with dirt or corrosion etc.

Where the flame arrester is not of a suitable proprietary type the openings in the arrester’s body must be at least of the same area as the cross-sectional area of the vent line.

Notes – Flame arresters not recognised as proprietary must be supported by satisfactory documentation. The hole in the top in the filler cap as provided by the original engine or fuel tank manufacturer, on tanks no more than 27 litres (6 gal) capacity, is compliant.

Fuel tanks Fuel tanks shall be properly secured and be installed as low as practicable and shall be constructed of a suitable non-corrosive material. Materials used in the construction of fuel tanks shall have a fire resistance of 30 minutes in accordance with BS 476: Part 20. Tanks shall have sustained a pressure test of 0.25Kgf/cm2 (no longer mandatory).

The objective of this standard is to ensure that fuel tanks are manufactured to give adequate protection to their contents in normal use or in the event of an accident.

This section considers the vulnerability of fuel tanks to leaks or failures that can lead to fuel and/or fuel vapour building up in the interior of the boat. It also covers the potential for chemical reaction between the fuel used and the tank material. The final concern is the fuel tank’s fire resistance which can help prevent a major escalation of a small fire close to the tank. Any stress in your boat’s fuel tank, lines, or fittings, caused by movement in the system, could lead to a persistent or even catastrophic fuel leak.

Fuel tanks which are not an integral part of the hull must be properly secured to prevent any movement which could result in:

Tanks must be secured by: metal framework; brackets; straps; welding to the hull; or collision chocks.

Soft soldered fillers must not be used since they would inevitably fail when exposed to excessive heat e.g. in a fire situation.

If the fuel tank is installed in the position determined by the boat builder it will be accepted that it complies with this standard. This applies if the boat was built by the owner.

There must be no obvious signs that any modifications have been carried out. The main indications that this may have occurred are that the additions and/alterations do not match the manufactures specification for:

Suitable materials must be used for the construction of the fuel tanks since fuel tanks must be resistant to corrosion. Choosing the wrong material for a boat’s tank, could introduce weakness and/or poor fire resistance. Unsuitable types of materials may be susceptible to corrosion and/or chemical reaction with the fuel inside. The wrong material may not be strong enough or may not have the right durability to prevent permeation or cracking. Failure could lead to fuel or fuel vapour building up unnoticed within the confines of your boat.

Example image: This fuel tank pictured above was installed in a Sealine F43 (year 2000) ocean going motor cruiser. It was constructed from Aluminium. It had a manufacturers label fixed and clearly visible, and was date tagged and pressure tested to 5 PSI. The filler pipe, vent arrangement, securing devices and associated connections had all been competently installed under the RCD regulations introduced in 1998 (EU) and which run in line with the BSS standards. (great example, with the remote fuel shut off cock noticeable in the fore-ground).

CE marked plastic tanks are accepted provided they are used within any restrictions placed on their use by the manufacturer. The requirements for marking of the fuel and the test procedure apply to these tanks. A separate information sheet is available on application to the BSS office www.boatsafetyscheme.com .

Notes – Examiners are not required to identify whether fuel tanks are lined or otherwise internally coated. A judgement will be made on suitability from a visual assessment of the tank’s external surfaces. If inaccessibility prevents a general assessment of the fuel tank material, it is ‘not verifiable’, and will be considered as non-compliant until the suitability of the material can be verified.

Notes – Particular attention should be paid to areas under dipsticks/sounding pipes for evidence of damage from dipstick ‘bounce’, where these are accessible.

Visually and manually check for material of tank for suitability and metrical failure such as:

Example Images: Welded edges on metal tanks are susceptible to crevice corrosion. Threaded and welded fittings for draw and fill lines are other trouble spots. Unfortunately, a metal tank’s weakest link is its undersides and outboard side, which are difficult and in some cases impossible to see. This tank, although not leaking, is ready for replacement! The plastic tank, above left was fine and properly CE marked, there was however a leak at the filling pipe position which will require further investigation. (see pooling diesel around the rim).

Fire resistance

The international standard BS EN ISO 10088 does not make any recommendation for fire resistance of fuel tanks with exception of non-metallic petrol tanks which must meet a fire test of 2 ½ mins followed by a pressure test.

Joints and seams made by close riveting must be suitably sealed by hard soldering or brazing or other means to make the joint fuel tight and fire resistant.

(not BSS mandatory for vessels manufactured prior to 16 June 1998).

This exemption only applies to the pressure test and not to any other requirements for fuel tanks e.g. non-corrosive material or fire resistance.

The international standard lowers the required tank pressure test from the previous UK recommendation of 0.25 Kgf/cm2 to 0.2 Kgf/cm2.

It is not necessary for the tank to be accessible for removal or maintenance but it is necessary for at least part of the tank to be capable of being reached for inspection.

If inaccessibility prevents a general assessment of the fuel tank material, it is ‘not verifiable’, and will be considered as non-compliant until the suitability of the material can be verified.

Accessibility of tank connections

It is a requirement of this standard ands it is also good installation practice that all connections are ready accessible for inspection.

However it is acceptable for connections to be accessible and not ready accessible. (I.e. behind screwed down inspection panels etc). This means that they must be capable of being reached for inspection without removal of permanent craft structure but it may be necessary to use tools.

The principal connections to fuel tanks are: filling pipes; fuel take off pipe; fuel return pipe; vent pipe; drain plugs or cocks; fuel level indicators; balance pipes (diesel engines only).

The objective of this standard is to ensure that petrol and paraffin tanks are protected against the effects of overheating and the production of excessive amounts of vapour.

Petrol tanks placed near an engine or heating appliance run the risk of generating flammable vapours and the potential for fire or explosion.

The purpose of a baffle in this context is to protect the fuel tank from directly radiated heat. They may be constructed from any material which is inherently fire resistant or which has been treated to be fire resistant.

Suitable materials would have a fire resistance of 30 minutes in accordance with BS 476; such as sheet metal of min thickness 0.9mm; or fibre glass of approx 5mm thickness.

If timber or ply was used it must be faced with metal or treated in such a way that it would provide the same degree of fire resistance.

The baffle may be modified to allow for the routing of pipes and cables etc providing the baffle, cables and pipes meet all the requirement standards.

The international standard has changed previous UK recommended practice of separation between a petrol tank and an engine from one metre to 100mm (4”) and this latter distance will be accepted for the purpose of the BSS. However, max separation between a petrol tank and a source of heat is considered to be best practice.

The international standard does remove the lower limit on tank size and this change has also been adopted.

Fuel level indicators Glass or plastic fuel sight tube gauges should not be used. Fuel level indicators, if fitted, shall be of a type which does not allow escape of fuel vapour in the event of damage to the indicator.

The objective of this standard is to ensure that fuel level indicators are properly installed so as to minimise the risk of the loss of the contents of the fuel tank in the event of damage. An inappropriately installed gauge on your tank could introduce a serious weakness. Glass or plastic fuel-sight tube gauges can easily be damaged by knocks or the heat from a fire, leading to a complete loss of the tank contents. With diesel or paraffin tanks, limiting any potential fuel escape is key to maintaining protection.

For many years the use of plastic or glass fuel sight tube gauges was not recommended practice in the UK as they were felt to be breakable, required a joint at or near the base of the tank, were exposed to physical damage and breached the fire resistance requirements of the tank.

This applied to all gauges of this type including those which are not errantly charged with fuel i.e. fuel is only admitted to the sight tube by means of a cock or valve for the purpose of taking a reading.

However, BS EN ISO 10088 allows their use on diesel tanks only provided that they are protected against physical damage and that damage does not lead to the loss of the contents of the tank. This is achieved by the use of a shield or cage, or by robust design, and by the incorporation of self closing valves which means that the gauge is only open to the tank when the operator is in attendance at the gauge.

Where a sight tube gauge has been disconnected to comply with this standard, the tank outlet must be fitted with a plug which;

(note that the self-closing valve at the top is not required if the gauge connection is made to the top of the tank)

Petrol tanks must not be fitted with glass or plastic tube or strip-type fuel gauges.

Gauges covered with a transparent cover for the purpose of reading a dial or indicator are only acceptable if no fuel has leaked into the space behind the cover.

If fuel can be seen behind the cover, the gauge becomes a glass or plastic sight tube gauge which is not permitted.

Note – Self-closing valves are not required for fuel gauges on any diesel fuelled vessel formerly used for the commercial carriage of freight or passengers or as a tug or as an icebreaker and which is to be licensed for use as a pleasure vessel, or registered for use as a houseboat, unless used for the purposes of hire or reward. Documentary evidence of former use addressed to the BSS manager is required to enjoy this exception.

Note – loose or damaged gauge needles, or other such level-indicators, mounted behind any glass or transparent cover do not constitute non-compliance.

Fitted dipsticks may be attached to the fuel filler cap, or separate fitting, provided they comply with these standards.

Dipsticks, when fitted shall be calibrated by means of marks, numbers, or letters etched or engraved into the surface.

Bonding of fuel tanks Tanks shall be effectively bonded by low resistance metallic conductors of adequate strength to their deck filling connection, and in the case of non-conducting deck or hull, tanks shall be electrically bonded to an earth point in direct electrical contact with the surrounding water, for discharge of static electricity.

The objective of this standard is to ensure that petrol filling and tank systems are electrically bonded to prevent the build up of static charge which may lead to an ignition hazard. This section addresses the hazards related to static charges and petrol vapours. The build-up of static charge, from fuel flowing through the filling pipe could result in sparks, which in turn could ignite petrol vapour.

Note: The international standard restricts this requirement to petrol systems against the wish of the UK to see it retained for all fuel systems. Bonding of diesel systems is therefore recommended as good practice. (but not a BSS failure).

The bonding to the deck filling connection must be: effective and by a low resistance metallic conductor of adequate strength. An effective bond is made when a conductor of the correct grade is securely fitted between the tank and the deck connection.

The recommended grade is a heavy duty cable with a conductor of at least 2.5mm Sq.

Where the filling pipe is made of conducting material it is not necessary to provide additional metallic conductor between the tank and the filling connection.

There must be:

Note – all necessary electrical bonding connections must be seen or reached in order to be able to establish the existence of adequate bonding provision.

The standard does not specify the size of this earthing point and the BMEA Code of Practice recommends that the resistance to ground be less than 10 ohms.

No minimum size is specified for the cable connecting the fuel tank to an earthing point but note the recommended size (2.5mm Sq) for the cable used for bonding the tank to a deck filling connection.

Fuel tank drainage Tanks may be drained only by a suitable drain valve fitted with a plug on the outlet.

The objection of this standard is to ensure that fuel tanks can be drained in a controlled way and that drains are protected against unintended operation. Leaking fuel from a poor connection or an unsuitable pipe is a hazard. If there is a fire, the system must be resistant to the heat and flames. It is known that fuel can leak past tank drains which are worn, or which have not been properly closed.

It is not a requirement that a drain valve must be fitted and it is not a fault if there is no valve. However, if a valve is fitted it must be suitable.

If a drain valve is fitted it must be connected to the tank by a leak proof connection and fitted with a plug which:

If a drain tap or cock is used, the outlet must be sealed with a plug which cannot be removed without the use of tools.

Fuel supply The fuel supply shall be drawn through the top of the tank or as near to the top of the tank as is practicable by means of an internal pipe extending to near the bottom of the tank. In the case only of gravity feed systems a feed from a cock or valve directly screwed in near the bottom of the tank is permitted. Any return fuel line required to be connected to the tank shall be connected through the top of the tank or as near to the top as is practicable.

The objective of this standard is to ensure that the risk of the loss of the contents of a fuel tank is minimised in the event that any fuel pipe is damaged.

It has previously been UK recommended practice to ensure all connections to fuel tanks are made at the top of the tank. The intention behind this recommendation was to minimise the risk of the loss of the contents of the tank in the event that the fuel pipe was damaged downstream. This is particularly hazardous in the case of petrol tanks.

However, BS EN ISO 10088 gives further options in the case of diesel fuel systems. In these types of installations the connection of the fuel feed can be made below the top of the tank or the highest point on the sides or end of the tank provided that:

For gravity fed systems, petrol or diesel, where the fuel supply has to be drawn through the bottom of the tank it must be drawn through a cock or valve screwed directly attached to the tank.

Providing it is installed as near the top of the tank as possible, the fuel supply may be drawn through the side of the tank if there is insufficient room to install a take-off fitting and associated pipe work at the top of the tank.

Note – A gravity-fed petrol installation is one where there is no lift-pump to move the fuel from the tank to the engine and the height of the tank is above that of the engine.

Best practice We recommend/suggest that diesel fuel feed or return lines are drawn through the top of the tank, or as near to the top of the tank as is practical.

The purpose of fitting the return fuel pipe to the top of the tank is to avoid the loss of the tanks contents if the return pipe or its fittings and connections develop a leak or are damaged. Therefore the options that apply to fuel feed systems apply here.

This check only applies to installations where the return fuel line is connected to the tank. It does not apply to systems where it returns fuel to some other part of the fuel installation e.g. it is connected to the fuel filter.

Return fuel lines must not discharge direct into the engine compartment or bilge. Return lines are only found on diesel engine vessels and petrol engines with fuel injection systems.

Notes – If any tank connections or tank valves are inaccessible for inspection and the condition is ‘not verifiable’, they will be classified as non-compliant until their condition can be verified as acceptable. This requirement applies to all tank connections and valves, including fuel filling lines, vent lines and balance pipes.

Fuel pipes, balance pipes and valves All fixed fuel feeds and pipes permanently charged with fuel shall be made of softened copper, stainless steel, aluminium alloy, or (diesel installations only) mild steel of suitable size, fixed clear of exhaust systems and heating apparatus and adequately supported to minimise vibration and strain. Ballance pipes are only permitted in diesel fuel installations. Any balance pipe between fuel tanks must comply with the requirements of this standard and must in addition be fitted with valves directly attached to the tank and so construction that the valves will not become slack when operated.

The objective of this standard is to ensure that fuel pipes and hoses are manufactured of appropriate materials and are installed to prevent damage in normal use. It is also intended to specify particular requirements for balance pipes in diesel systems to minimise the risk of the loss of the contents of the tanks in the event of damage.

All fixed fuel feeds and fuel pipes permantley charged with fuel are to be made of the materials listed above as:

Softened copper pipe is solid drawn copper pipe which has been annealed (heated) after the drawing process which makes it more suitable for bending and working than hard drawn pipes.

Flexible tubing is more vulnerable to damage and the effects of heat than rigid pipework and its use for pipes permanently charged with fuel is a balance between convenience and replacement costs. It must be expected that a flexible hose will need replacement a number of times through out the lifetime of the boat.

The material of any hose must not react chemically with the fuel in use leading to deterioration and leaks as in this case.

Flexible hose is widely used for connections to engines in order to mitigate the effects of vibration when the engine is running, and to take into account of the relative movement between different parts of the boats structure.

Existing engines may be fitted with hose to BS MA 102 which is acceptable providing the hose is in good condition. If the condition of the hose is suspect, they must be replaced with hoses which meet at least the fire resisting quality of BS EN ISO 7840.

Flexible balance pipes are allowed providing the installation meets the requirements of the appropriate Standard.

Spill racks must comply with the fire resisting quality requirements of BS EN 7840 and be connected with efficient joints.

Soft soldered connections and unclipped push-on joints must not be used.

The requirement is consistent with the international standard for marine diesel engines for small craft IOS 16147.

Note: Supplementary information on spill rail options is available on www.boatsafetyscheme.com or by post or email from the BSS Office. Injector leak-off hoses fitted by the manufacturer within an enclosure on the engine meet this requirement.

These PVC push on pipes must not be used. They can be replaced with either a solid metallic spill rail or replace them with BS EN ISO 7840 hose and small hose clamps.

Identify pipes and hoses permanently charged with fuel and visually and manually check for signs of:

Visually check route of pipes and hoses for clearance from unshielded or unlagged exhaust systems. Where clearance is less than 75mm check for damage to fuel system. Note: that the failure point is on damage not distance.

As can be seen in the picture a fuel pipe is almost touching a hot exhaust pipe on this Eperspacher warm air diesel heater. The exhaust should be properly lagged (they get very hot) and the fuel pipe re-routed away from the exhaust.

THIS PAGE IS STILL UNDER CONSTRUCTION AND THE REMAINING BSS REQUIREMENTS FOR FUEL SYSTEMS WILL BE INCLUDED SHORTLY