Fuel hoses for petrol inboard engines

The context of this article is in relation to improving the safety of operators and crew of existing inboard petrol powered vessels including auxiliary petrol motors from the possibility of explosion resulting in death or injury.

As one of our clients stated: “This vessel has only exploded once in all my 40 years of fishing. The explosion throwing me backwards onto the net board, so my vessel is perfectly safe!”

This particular case was the result of the fuel tank breather line falling off the fuel tank connection with the resulting fumes allowing free passage through the open boat structure as no bulkheads were included in the construction of the vessel finally allowed to gathering in the bilge under the motor. This nearly resulted in a personal space shuttle, he was lucky.

Material safety data sheet
The CSR material safety data sheet for E-85 Fuel Ethanol 2009 describes unleaded petrol/ethanol blended fuels having a;
Lower explosive limit of just 1%
Upper explosive limit of 8%

National Standards for Commercial Vessels (NSCV)
Part C Subsection 5A 2.14.3 Vessels where fuel having a flash point less than 60°C is permitted.
Fuel having a flash point less than 60°C may be used in the following applications:
a) Outboard engines in classes C, D and E vessels
b) Internal combustion engines in class 2C, 2D,2E,3C, 3D and 3E vessels that are not located below decks.

NOTE: An engine is considered to be “below decks” if fuel or fumes emanating from the engine installation could result in the accumulation of fuel or explosive mixtures within any space on the vessel. Fuel and fumes from the engine must be able to drain rapidly and directly overboard without the assistance of fan forced ventilation or wind-induced air movement.

Part C Section 5 Subsection 5A
Additional Requirements for Fuel Systems in Vessels with Non-portable Fuel Tanks and which Operate on Fuel with a Flashpoint Less than 60°C

4.10 Additional requirements for fuel systems in vessels with non-portable fuel tanks and which operate
on fuel with a flashpoint less than 60 degrees C

4.10.11 Fuel piping
Unless provided for in clause 4.10.12, piping in fuel systems for non-portable fuel tanks shall be of seamless heavy gauge metal. Pipe connections shall be made via a flanged joint, metal to metal joints of the conical type or other suitable means, and shall be minimised. Pipe connections shall also be readily visible and accessible. Where cone nipples are used, they shall be welded. Olive- type Compression fittings shall not be used.

4.10.12 Flexible piping
A short length of flexible piping may be fitted in fuel systems for non-portable fuel tanks in the section of line between the engine bed and the fuel lift pump.
Flexible piping shall have a synthetic rubber inner tube with a metal braided reinforcement. It shall be resistant to heat, salt water, petroleum products and vibration and shall comply with a relevant national or international standard
(SAE J1527 type A or ISO 7840 TYPE A1). It shall be visible and clear of the bilge, and shall be secured to prevent chafing.

As you can see from the last two statements the NSCV specifies only a short length of flexible fuel hose is permitted on the fuel system to adsorb the vibrations from the engine movements. How often have we seen flexible fuel hoses installed for the entire run from the petrol tank to the motor?

Our current NSCV standards refers to the use of fuel hoses to the Society of Automotive Engineers (SAE) J30 code
Fuel and Oil Hose
J30 refers to
1. SAE J1527 – Marine Fuel Hose 2007-01
2. SAE J1942 – Hoses and Hose Assemblies for Marine Applications 2007-04

SAE J30 fuel and oil hose
Historically the older version of SAE J30 code (pre 1998) was ratified in the USL code before the introduction of Ethanol or alcohol additives to the petrol (E10 fuel) that we use today. Either SAE J30 standards (pre1998 or the post dated standard) will not be ratified in the new NSCV code its downfall being that there is no fire protection requirements specified to the exterior of the hoses.
The SAE J30 1998 code is being replaced with SAE J1527 Type A Jan 2007 or ISO 7840 Type A1 2004 codes.

SAE J1527 Marine fuel hoses
The SAE J30 references to the more recent code SAE J1527 Jan 2007 standards. SAE J1527 code refers directly to the American Code of Federal Regulations 183.558 who takes onboard the United States Coast Guard (USCG) 183.558 standards for fuel hoses. Both United States Coast Guard (USCG) standards and the proposed National Standards for Commercial Vessels (NSCV).

Equivalent standard ISO 7840-2004 Small Craft- Fire- resistant Fuel Hoses specifications, identify the different classifications of hoses and there testing procedures for
• Fire resistance
• Abrasive resistance
• Burst pressures
• Cold conditions flexibility
• Dry heat resistance
• Oil proof resistance
• Ozone and UV resistance
• Delamination of the internal components of the hose.
• Fuel permeation (fuel leaching through the hose structure)
• Markings and the ID of hoses (every 300mm)

The USCG, ISO and the SAE codes do not describe the application for the different hoses identified.

SAE J1942 hose and hose assemblies for marine applications
This standard refers to the application of hoses certified by SAE J 1527 type A and the USCG standards.

In relation to the subject of petrol fuel hoses the hose and fittings are described as:
Flexible fuel hoses
Lube oil and Fuel Systems
• has the construction that includes plies or braids of steel wire with or without textile with reference to the working pressure of the system i.e. fuel pump or fuel injection pressures. (SAE J1942 section 3 Table 1)

Fuel Hose Fittings
Fittings not accepted are,
• Push on fittings
• Quick disconnect couplings
• A single worm drive clamp
• A single band around the hose

Only hose to SAE J 1527 type A and fitting combinations SAE J1942 that have been tested and passed the requirements of this document as hose assemblies are acceptable. The tests performed on these assemblies include,
• Fire resistance
• Abrasive resistance
• Burst pressures
• Salt water permutation
• Cold conditions flexibility
• Dry heat resistance
• Oil proof resistance
• Ozone and UV resistance
• Delamination of the internal components of the hose.
• Fuel permeation (fuel leaching through the hose structures)
• Markings and the ID of hoses (every 300mm)

Hose Identification
The identification of the approved type fuel hoses will display some form of Standards mark. The approved types of hoses are required by all standards to be permanently marked every 300 mm with either:
• SAE J1527 Type A
• USCG TYPE A1
• Underwriters Laboratories Inc (UL) standard 1114
• ISO 7840 type A1 standard with or without C.E. (Conformite Europeenne) certification

Surveying petrol inboard vessels
With this in mind in the inspection of these petrol inboard vessels we have to assess not only the fuel system and lines but engine compartment ventilation and potential sources of ignition both from electrical sources, heat sources, and any potential engine misfire/backfires thought the carburettor throttle bodies as well as the leaking of fuel from the float chambers and vents of carburettor type fuel fed motors. (SAE J1223 – 1993 Marine Carburettors and Fuel Injection Throttle Bodies).

The Risk Assessment process should include the scenario of one or a series of conditions that occur simultaneously, an assessment should be based on the elements of the fire triangle.
The fire triangle requires the presence of the three elements:
1. The presence of a fuel
2. The presence of oxygen
3. The presence of a ignition source

If you have ever studied the Mercruiser petrol inboard engines you can see how they have tackled the problems of petrol motors in fuel and ignition sources.
• Most motors are fuel injected engines but even the carburettor motors conform to the SAE J1223 1993 Marine Carburettors and Fuel Injection Throttle Bodies standard.
• The factory engines have all swaged fuel fittings on heavy braided or steel braided certified fuel hoses and fuel assemblies.
• Intrinsically safe spark shielded starter motors and brushless alternators to SAE J1171 2004 External Ignition Protection of Marine Electrical Devices.
• All exposed electrical terminals are covered and insulated.
• The engine air intake filter has a spark proof gauze on its exterior.

Degradation of fuel hoses
Degradation of the fuel hoses can be caused not only by mechanical damage but the permutation or weeping of fuel through the pores of the internal fuel hose causing the hose to become spongy by feel and in the case of non approved hoses the breakdown of the outer cover by UV light. The biggest problem we face is this non approved hose. These types of hoses may include the transparent type with a few plies of nylon reinforcing through them. These hoses are sold as food and petrochemical hose but they don’t carry any standards marking. The outside layer of this hose is not UV stable or more important fire proof to satisfy the SAE 1527
type A standards.

Carburettor tray
NSCV Part C section 5 subsection 5A 4.10.13 specifies that the carburettor should be installed with a flame proof removable catch tray to catch any leaks of fuel from the carburettors.

Vessel ventilation
Vessel ventilation will have to be assessed. It could be natural or power operated. If we look at the ISO 11105-1997 standard Small Craft- Ventilation of Petrol Engine and/or Petrol Tank Compartments.
The standard defines open air ventilation as:
3.1 Open to the atmosphere. Compartment or space having at least 0.34 metre square of permanent open area directly exposed to the atmosphere for each cubic metre of net compartment volume.

There is also the question of just where in the engine compartment the exhaust vent should originate from. The ISO 11105 standard specified in 5.2 that the exhaust vent shall originate from the lower one third of the compartment above the normal level of accumulated bilge water. This should also echo for the origin of any fan forced bilge blower system installed.

Bilge blowers
NSCV Part C section 5 subsection 5A 2.21
Ventilation of Machinery Spaces.
Refer to this section to ascertain the size of the apertures required and size of the bilge blowers required.
The operational procedure that the vessel operators must adhere to [small ship management procedures (SSM)] can be found in ISO 11105: 1997-05-15 Small Craft- Ventilation of Petrol Engine and/or Petrol Tank Compartments 1997.
6 Powered ventilation Systems

6.1 Unless open to the atmosphere, each compartment containing a permanently installed petrol engine shall be vented by removing air from the compartment to the atmosphere outside the craft by an exhaust blower system.

6.5 Each craft that is required to have an exhaust blower shall have a label that
• is located as close as practicable to each ignition switch;
• is in plain view of the operator;
• has the symbols in accordance with ISO 11192, depicted in the figure below, or at least the following information in the language acceptable in the country of sale:
WARNING – Operate blower for 4 min before starting engine.

The issues associated with bilge blowers are;
1. The blower units are to be installed to evacuate fumes out of the compartment and not to blow air from the atmosphere outside the compartment into the engine space.
2. The blower units themselves are to be intrinsically safe types.
3. Is the blower installed to remove the fumes outside of the vessel and not just transferring them outside of the space to create other potential explosive hazards?

Electrical assessment
An assessment of the vessel’s wiring in the high risk areas and in the engine space where the considerations for the condition and state of the installation.
• NSCV Part C section 5 subsection 5B 3.8.4.2 Mechanical protection specifying the protection of wiring
• NSCV Part C section 5 subsection 5B 3.8.4.3 Battery boxes specifying on the installation and security of batteries
• SAE J1171 2004 External Ignition Protection of Marine Electrical Devices
or ISO 8846 1990 (E)
Small Craft- Electrical devices- Protection Against Ignition of Surrounding Flammable Gasses
Specifying the installation of electrical devices are intrinsically safe items such as starters, starter solenoids, alternators/generators, bilge pumps, high water alarm, ignition coils, distributors, high tension wires, radio interference suppression devises

As you can see the issue of petrol engines is quite technical, but it is the outcome that is most important to create a safe vessel.

Recommendations
1. Check that the installed electrical devices are intrinsically safe items such as starters, starter solenoids, alternators/generators, bilge pumps, high water alarm, ignition coils, distributors, high tension wires, radio interference suppression devises. SAE J1171 2004 External Ignition Protection of Marine Electrical Devices or ISO 8846 1990 (E) Small Craft- Electrical devices- Protection Against Ignition of Surrounding Flammable Gasses.

2. The battery is not to be installed under the engine cowling and should be contained within its own dedicated battery box. The battery box should be secured to the vessel to prevent battery movement and be installed in a location where battery vapours will not gather in concentration in the bilges of the vessel. NSCV Part C section 5 subsection 5B 3.8.4.2 Mechanical protection and NSCV Part C section 5 subsection 5B 3.8.4.3 Battery boxes.

3.All terminals and connectors are to be clean and tightly secured as not to cause any resistance between the connections. This will cause heat to build up in the joint.

4. Any non essential wiring not required to run the engine or bilge system shall be removed from within the engine space.

5. All essential wiring within the engine space is to be of the standard of:
• In one continuous length, with no unnecessary electrical connections or joins just to increase the length of the wiring.
• All wiring should be contained within a wiring loom and be double insulated being contained in split corrugated conduit or simular.
• Any necessary connections should be first insulated with electrical insulation tape then wrapped in self vulcanizing rubber tape e.g. 3M Scotch 42 tape.
• They should be run in a way as to be secured clear of sources of heat, abrasive and sharp edges with secure clips to the vessel.

6. The fuel hoses are to meet the standards for ethanol fuel proof, steel braided and possess a fireproof standard to meet the SAE J1527 type A or USCG type A-1 or ISO 7840 type A1. The hoses should be as short as possible and only installed to adsorb motor vibration at the engine mounts. All other hoses should be constructed of solid seamless pipe have commercially swaged fittings with no unnecessary joins and be adequately clipped clear of sources of heat, abrasive and sharp edges with secure clips to the vessel from the engine to the fuel tank.

7. Install a suitable fuel shut off valve that can be operated from an accessible position outside of the engine enclosure or tank to enable the fuel supply to the motor to be isolated in an emergency.

8. Electrically earth all metal fuel filler necks to the fuel tank to prevent the risk of kinetic sparking from the potential difference between the fuel tank and fitting.

9. Install a suitable intrinsically safe bilge blower to the ISO 11105 standard taking into account the enclosed volume in the engine space. The blower is to be rated for continuous operation as stated in the standard. Install ducting using heat proof hose. The intake for the duct shall be in the lowest one- third of the bilge and above the normal level of accumulated bilge water. The blower is to be installed to exhaust fumes (remove air) out the engine space and not blow air into the space. Note the standard ISO 11105 requires the ISO signage at the helm stating that the blower to be activated four minutes before starting the vessels petrol engine.

Article written by Symon Thomas MIIMS

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