LPG
has been used as an internal combustion engine fuel for a great many years.
This revision of the 1992 edition recognises the advances in engine design and
the improvements in engine management systems. It also now includes guidance on
fuel systems for heavy duty engines for buses and coaches and passenger service
vehicles which usually involve conversions from diesel fuel or the use of such
engines specifically designed for LPG operation.
LPG
engine fuel systems are now available for all generations of spark ignition
management systems. These are broadly defined as follows:-
1st
generation������������ Carburettor
air-gas mixing systems.
2nd
generation������������ Carburettor
systems with micro processor control�
derived
����������������������������������� from
engine speed, manifold pressure and lambda sensor
����������������������������������� for
optimising 3-way exhaust catalyst operation.
3rd
generation������������� Multi-point
liquid or vapour injection systems, but with
������������������������������������
non-adjustable self learning feedback controls.
There
are many variations of property systems available, but the principles are
illustrated in Appendix 4.
Most
LPG conversions from petrol are bi-fuel systems retaining the petrol fuel
system as an alternative.
Diesel
conversions are dedicated LPG systems since diesel compression ratios are too
high for LPG and require piston or cylinder head modification.
There
are heavy duty engines available designed specifically for LPG operation.
OBJECTIVE.
To
set minimum standards for the safe installation and use of LPG as a road
vehicle engine fuel.
Scope.
The
Code includes the design and installation of the fixed LPG fuel tank or tanks,
and the fuel feed system comprising fittings, pipework, connections and
controls for internal combustion engines of road vehicles including bi-fuel
installations (for LPG or petrol operation), or conversions from diesel, or specifically
designed engines for LPG operation.
Buses,
including Public Service Vehicles (PSVs) are covered in Section 6 to draw
attention to the special requirements for this important sector of the road
vehicle industry in view of the interest in introducing LPG as a means of
reducing urban pollution.
Both
vapour feed and liquid feed systems are included to cover all four generations
of engine design, including injection. Detailed design or modification of the
engine
And
its management system, and the electronic controls for stoichiometric or
lean-burn operation are all state of the art developments subject to continuous
development by engine manufacturers and conversion specialists, and are not
part of this Code.
The
Code excludes fuel systems for:-� Dual
fuel engines i.e.LPG-Diesel
�������������������������������������������������������������
Fork-lift trucks
�������������������������������������������������������������
Stationary engines i.e. non-transport.
DEFINITIONS
For
the purpose of this Code the following definitions shall apply:-
Competent
Person:�� A person with knowledge,
training and ability to cxarry out their work safely and with the necessary
proficiency to ensure the subsequent safe operation of the vehicle.
Component:� Any equipment through which LPG or other
fuel flows and is added as part of the vehicle conversion.
Gas
Container :� The term used in the �
Construction and Use�Regulations meaning a fuel tank which is a pressure vessel
for the storage of LPG to be used as an automotive engine fuel.
Contents
Gauge:� A guage which gives visual
indication of the liquid contents of the fuel tank.
Bi-Fuel:� Where two alternative fuels are provided.
Dual-Fuel:� Where two different fuels are fed to the
engine simultaneously:usually a
gaseous
fuel addition to a diesel engine.
Bus:� A motor vehicle which is constructed or
adapted to carry more than eight seated passengers in addition to the driver
(Road Vehicles Construction and Use Regulations).
Passenger
Service Vehicle(PSV).� A bus used for
carrying passengers for hire or reward, or other vehicle, except a taxi used
for carrying passengers for hire or reward at separate fares in the course of
business (Public Passenger Vehicle Act 1981).
Mini-Bus:� A bus designed to carry seated more than
eight passengers but not more than sixteen excluding the vehicle driver.
Fixed
Maximum Liquid Level Indicator:� A gauge
which indicates the maximum permitted liquid level in the fuel tank. It
comprises a tube arranged with its open end located at the maximum permitted
liquid level, so that gaseous discharge changes to a visible liquid discharge
as the liquid surface reaches� the level
during filling.
Hydrostatic
Relief Valve:� A valve whose purpose is
to relieve and prevent over pressure due to thermal expansion in any supply
pipeline carrying LPG in the liquid state.
Stop
Fill Valve:� A double check level
device, which prevents the over filling of a fuel tank beyond a pre-determined
liquid level. (usually 80%).
Lock-off
Valve:� A term used to describe a
shut-off valve in the fuel feed line which will automatically shut-off the fuel
feed to the engine under specified conditions relating to vehicle operation and
safety.
Lambda
(^)�� The ratio of air supplied to an
engine to the stoichiometric air required. At stoichiometric ^=1: lean
burn^> 1.
Multiple
Valve.� A manifold block which requires
only a single nozzle opening in the fuel tank which incorporates all or some of
the following fittings: 80% stop-fill valve, level indicator, pressure release
valve, service valve with excess-flow valve, and fuel pump.
Gas
Tight Housing:� A cover mounted over the
fuel tank fittings to protect them and to prevent gas leakage entering a
vehicle, and to vent to the open air.
Non-Return
Valve:� A device to permit flow in one
direction and prevent the flow in the opposite direction.
Check
Valve (device):� Another term for a
non-return valve.
Fill
Connector:� The self-sealing fitting at
the fuel tank or at the terminal of the fill pipe extension designed to accept
the self-sealing coupling of the refuelling facility.
Design
Pressure:� In this Code, design pressure
is the pressure for design purposes in BS5054 part 2. Care is necessary in
using other pressure vessel standards as design is sometimes based on the test
pressure which may not be the same.
�����������������
���������������������������������������� LPG FUEL TANK OR TANKS
Fuel
tanks shall be designed and constructed in accordance with BS5045 Part 2 or
other equivalent recognised Pressure Valve Standard and a Test Certificate
issued accordingly.
Fuel
Tanks shall have a design pressure of not less than 26 per gauge and preferably
be constructed of steel.� Other
materials are not precluded where equivalent standards of physical, thermal and
chemical integrity have been demonstrated.
�
Marking:_
Each
fuel tank shall be conspicuously and permanently marked with its design/test
pressure and other data required by the pressure vessel standard.
The
information should include at least the following:-�
The
specification or code to which the fuel tank is manufactured.
The
manufacturers name or identification mark.
The
fuel tank serial number.
The
minimum designed water capacity in litres.
The
design/test pressure in bar gauge.
The
year and month of manufacture.
The
date of the hydraulic test and identification mark of the testing authority and
space allowed for subsequent re-tests.
These
marks should not be less than 6mm in height.
Tanks
must be clearly and permanently marked to indicate the correct orientation to
ensure the correct operation of the valves and contents gauge.
Location
of the Fuel Tank(s):-
Fuel
tanks shall be located in a place and in a manner as to minimise the
possibility of collision to the fuel tank and its fittings. Fuel tanks located
toward the rear of� a vehicle when
protected� by substantial bumpers or
structure from the rear or side impacts, shall be� deemed to comply with this requirement.
The
vehicle manufacturer should if possible, be consulted to ascertain if there is
a recommended position for the fuel tank in or on the vehicle.
Fuel
tanks within a vehicle should be located in a sealed compartment� or should have their valves, fittings and
extensions to the outside enclosed in a gas-tight housing attached to the tank.
This housing shall be vapour tight to the interior of the vehicle, but vented
from its lowest point to the outside of the vehicle, e.g. by a vent tube. The
vent tube should have a free ventilation cross-sectional area of not less than
450mm2.
Fuel
tanks other than those for mini-buses, estate cars and those with hatch-backs,
may be located in a vehicle compartment which is effectively sealed from the
remainder of the vehicle and ventilated to the outside. The ventilation shall
be by permanent openings not less than 2000mm2 in total area.
The
opening should be direct to the outside air from the lowest practicable
position within the compartment.
The
opening should be remote from the engine exhaust system and not closer than
250mm.
The
opening should be by position, or other means, be protected from blockage both
from within the compartment or without.
Fuel
tanks, valves and fittings may be located beneath a vehicle in a suitable
protected position.
Fuel
tanks may be mounted on the rooftops of vehicles, subject to the following:-
There
shall be confirmation by the vehicle manufacturer that the location will not
seriously affect the stability of the vehicle. See section on buses and PSVs.
Crash
bars and/or roll-over protection shall be provided where deemed necessary for
the type of vehicle and its duty.
Tank
valves, fittings and extended pipework should be housed in a gas-tight housing
as previously described , unless a suitable protected roof compartment is
provided.
The
ventilation from the gas-tight housing or compartment shall take account of the
heavier than air density of LPG vapour, and shall ensure no discharge can enter
the interior of the vehicle
Fuel
tank(s) mounted underneath vehicles should be situated to ensure effective
ground clearance and take account of the following:-
The
fuel tank, its fittings and any pipes adjacent thereto shall be located so as
to minimise the possibility of damage due to contact with the road or
obstructions on the road.
The effective ground
clearances recommended by the vehicle manufacturer shall be
Maintained,
but where these cannot be determined then either of the options below
Shall
be met. This clearance shall be measured to the bottom of the fuel tank or to
the lowest fitting, support or attachment of the fuel tank if this is less.
Fuel
tanks shall be installed with as much effective road clearance as is
practicable and not less than 250mm. It should take account of the minimum
horizontal clearance of the vehicle.The effective ground clearance should take
account of the minimum horizontal clearance of the vehicle from the front to
back and of the clearances between the axles and behind the rear axles to take
account of kerbs and bridges and entry to and exit from ramps. These clearances
vary considerably between vehicle manufacturers and for different types of
vehicle use, but shall be determined as follows:-
The
effective road clearance� at the fuel
tank when the vehicle is loaded to the point of maximum spring deflection.
The
effective road clearance of the vehicle at the fuel tank position when loaded
to its gross vehicle weight rating, provided that under unfavourable road
conditions, a fixed part of the vehicle comes into contact with the road
surface before that of the fuel tank, its fittings and adjacent pipes.
.
Fuel
Tank Mounting.
Means
should be provided for attaching the fuel tank(s) securely to the vehicle. This
provision may take the form of fixed lugs welded to the fuel tank during
manufacture or the provision of cradles, metal straps or bonds attached to the
vehicle. In order to prevent distortion of the fixing area or the tank(s)
breaking loose in the event iof an impact, reinforcement of sheet metal body
panels etc. should be provided by suitable means designed to equally distribute
the weight of the tank and its contents. The fuel tank(s) mounting shall be
sufficient to resist safely a deceleration of 30g.� Care should be taken to ensure that friction, rubbing and
corrosion does not take place between tank and cradle by the use if necessary
of suitable friction preventing material i.e. rubber, plastic etc.
Fuel
tank(s) should be mounted in a level position, correctly orientated as marked.
Fuel
tanks and their fittings should be protected by position, or other means,
against physical impact and tampering.
The
fuel tank shell, fittings and pipework should not be run outside the plan area
of the vehicle viewed from above.
Where
this requirement cannot be met collision bars or other suitable protection must
be provided.
Multitank
Installations.
A
means to prevent the flow of liquid from one tank to another must be fitted
into both the filling and fuel supply lines.
������������������������������� FUEL TANK FITTINGS AND CONNECTIONS
All
fittings should be constructed for LPG service and suitable for operation at a
pressure not less than the working pressure of the fuel(s) concerned.
All
connections and fittings should, by position or other means, be protected
against physical damage, weather and tampering where possible. Manual operated
valves should be readily accessible.
Connections.
All
connections to fuel tanks greater than 3mm diameter for liquid and 8mm for
vapour, with the exception of those for relief valves, and contents gauges,
should be provided with a self closing device eg an excess flow valve, or
non-return valve, to prevent the escape of product in the event of damage to
the connections.
All
liquid and vapour connections to and from the furl tanks with the exception of
those for relief valves, plugged openings, and those where blind connections
through the fuel tank shell are not greater than 1.4mm diameter should have
shut off valves located as close to the fuel tank as practicable.
Fuel
supply valves should be clearly marked with the direction of rotation to close,
if manually operated.
The
position of manual shut off valves, if not visible from the outside of the
vehicle, should be indicated by a suitable notice clearly visible from outside
the vehicle.
Fittings.
Fittings
and components subject to tank pressure shall be proven suitable for contact
with vapour and liquid phase LPG and designed for a pressure not less than the
tank design pressure. They may be separately mounted on the fuel tank or they may
be in the form of a multiple valve system incorporating some or all of the
fittings in a single tank entry/exit.
Tank
Fill Valves and Fill Connector.
The
fill valve on the tanks shall incorporate a double check valve to prevent
reverse flow and an automatic stop fill shut off device fitted directly to each
fuel tank. The automatic stop fill shut-off device shall be designed to limit
the maximum quantity of LPG to 80% of each tank capacity, and shall meet the
requirements of ECE Regulation 67 or equivalent.�
Where
tanks are located inside a vehicle an extended fill line to the outside of the
vehicle should be provided terminating with a further check-valve and refilling
connection. This should be enclosed to prevent ingress of road dirt.
The
fill connector should be located so as to be readily accessible, but should not
be fitted within 250mm of the exhaust outlet, (except buses). Adequate ground
clearance shall be provided and it shall be as far as practicable in a
protected position.
The
fill connector shall be compatible with the mating coupling of the refuelling
facilities. The need for adaptors shall be discouraged.
(An
international standard is desirable and it is expected that a European standard
will be issued in due course).
The
essential design requirements of the fill-connector and its mating coupling
are:-
There
shall be no leakage to atmosphere during the filling operation.
The
design operating pressure shall be not less than the fuel tank design pressure.
Automatic
self sealing shall occur immediately the refuelling coupling is disconnected.
There
shall be no significant LPG release from the connector as the mating coupling
is disconnected.
The
seals shall provide long term resistance to liquid phase LPG to BS6505 or
equivalent.
Adequate
endurance in operation shall be proven, preferably by testing, to suit the
predicted vehicle operation.
The
connector shall be provided with an end cap which is vented by an aperture not
greater than 1.5mm diameter, which is secured to the vehicle by a chain or
other means.
Fuel
Feed Valves.
The
fuel feed outlet from each tank requires:-
A
suitably sized excess flow valve mounted directly to the tank. An excess flow
valve in this context means a device which automatically and instantaneously
reduces to a minimum the flow of gas through the valve when the flow rate
exceeds a set value.
An
electrically controlled solenoid valve which closes on de-energising and closes
automatically when the ignition control is in the off position and also
whenever the engine is not running. If it is not practical for the above valve
to be fitted directly to the tank, it shall be fitted as close as practical and
a manually operated shut-off valve shall be fitted directly to the fuel tank.
To
relieve thermal over pressure in the fuel feed pipework due to lock-up when the
solenoid valve is closed, the valve for single tank installations may be
designed to permit reverse flow back to the fuel tank. If the valve does not
permit this, or if a manual valve is fitted at the tank outlet, a hydrostatic
relief valve will need to be incorporated which may relieve back to the tank,
where the volume of gas which is locked up exceeds 200ml.
For
inter-connected multi-tanks reverse flow solenoid valves may not be suitable
unless other means are provided to ensure that overfilling of any tank from the
others is prevented.
�
Safety
Relief Valve.
Each
fuel tank must be fitted with a spring loaded safety relief valve mounted
directly in the vapour space of the tank.
Safety
relief valves shall be designed to start discharge and attain full flow at
pressures in accordance with the design code of the fuel tank to which they are
fitted with full allowance for the effect of extended discharge pipework.
Reference should be made to LPGA Code of Practice No. 15 part 1. This requires
relief valves to be marked with specified information which includes the set
pressure.
The
discharge from safety relief valves shall be vented to the outside of the
vehicle and as far as practicable from possible sources of ignition and shall,
in any case, be not closer than 250mm from the exhaust system. The outlet shall
be positioned in such a manner as to prevent impingement of escaping gas on any
fuel tanks, and in any case of externally mounted tanks directed downwards, and
in such a way as to prevent ingress of water. A captive raincap or other
captive protector shall be used to keep water and dirt from collecting in the
vent pipe but which shall not prevent free discharge when venting.
Piping
or ductwork used to convey the escaping gas from the safety relief valve shall
be of a material suitable for use with LPG and shall not reduce its maximum
flow to less than that required. Elbows and bends can have a severe effect on
flow. The minimum size of discharge line shall be 13.5mm� ID for containers up to 200 litres water
capacity and 16mm for containers exceeding this capacity.
Such
a discharge line shall be able to withstand the pressure resulting from the
discharge of vapour when the safety relief valve is in the fully open position.
It shall be of sufficient mechanical strength and adequately against physical
damage or leaks.
The
piping or duct work connection to the relief valves shall be mechanically
secured and shall not rely on adhesives etc for retention.
Fixed
Maximum Liquid Level Indicator.
Where
a maximum stop/fill valve is fitted, a fixed maximum liquid level indicator is
not necessary.
The
fixed maximum liquid level device, when fitted, should be suitable for use with
the LPG stored and should indicate a maximum permitted fuel content at 80% tank
volume.
If
the device relies on a bleed to atmosphere it should be so designed that the
bleed hole does not exceed 1.4mm diameter.
The
device should be designed so that the moveable parts of the device cannot be
withdrawn completely in normal gauging operations.
The
bleed from the device should be extended to the outside of the vehicle,
together with the fill pipe.
Where
more than one tank is fitted, each tank should have a separate fixed liquid level
gauge. This is in order to prevent accidental over filling by inadvertently
topping up already full containers in successive filling operations.
Alternatively,
this requirement may be relaxed if the system uses automatic switching of fuel
supply to the engine between tanks every few minutes, or separate fill points
to each tank.
Contents
Gauge. (Optional Fitting).
Direct
reading magnetic tape float gauges are recommended.
Contents
gauges should clearly indicate FULL at 80%.
The
sensing device of any indicator operated by an electrical system that may be
exposed to LPG vapour should be of an approved construction for use in
flammable atmospheres.
All
contents gauges materials should be suitable for the application with awareness
of tank location. Those mounted under vehicles should not be manufactured from
aluminium or other materials susceptible to salt spray.
All
wiring connections within the tank valve box should be adequately fixed and
protected.
A
remote reading fuel gauge should be provided for dashboard mounting.
Multiple
Tanks.
A
single refuelling connection is normal for multiple tanks, and the fuel feed
outlets are manifolded to a single feed pipe to the engine. Appropriate check
valves are therefore necessary at each tank connection to prevent flow between
tanks.
��
����������������������������������������������
PIPEWORK
LPG
Pipelines.
Pipelines
or pipework for automotive applications are classified as �high pressure
pipelines� if either are carrying LPG in the liquid phase, or carrying vapour
in excess of 200mbar gauge. In either case, the pipelines and their assemblies
shall be resistant to liquid phase LPG. Pipelines carrying vapour up to 200
mbar gauge are classified as �low pressure pipelines�.
High
pressure pipelines should be:-
Seamless
stainless steel to BS6362 or equivalent or,
Copper
or copper alloy to DIN1787 or DIN17671 or equivalent or
Flexible
fabric or metallic reinforced synthetic rubber or polymer hose designed for the
service pressure but not less than 25 bar gauge with a burst pressure not less
than 125 bar gauge and to meet the criteria of ISO8789:1994.
Engine
compartment hoses should be suitable for an ambient temperature of 120 degrees
centigrade and need to be specifically warranted for this temperature as stated
in ISO8789. A lower temperature may be acceptable if approved by the vehicle
manufacturer.
Hoses
shall be permanently marked as required by their specification standard and in
relation to their test certificate.
Low
pressure pipelines may be rigid or flexible and in either case they shall be
impervious and resistant to LPG in both liquid or vapour phase at the predicted
operating temperatures. They shall be capable of sustaining at least 3.5 bar
gauge without leaking or excessive distortion. If the operating conditions will
involve an internal vacuum, they shall be capable of withstanding safely the
maximum operating vacuum, or preferably a full vacuum, without collapse or
undue distortion. Engine compartment flexible pipelines (hoses) shall be
suitable for an ambient temperature of 120 degrees centigrade.� A lower temperature may be acceptable if
approved by the vehicle manufacturers.
Joints
and Connections.
Every
joint or connective fitting should be of metal and of a type suitable for service
with LPG at the operating pressure. This does not preclude the use of� suitable non-metallic seals within the
fitting, complying with BS EN 549. Jointing compound for screw threads where
appropriate shall be suitable for use with LPG and comply with BS6956 part 6 or
7 or pr EN751.
The
number of joints and connections should be the minimum for the melusion of
essential components.
Flared
joints or compression union fittings with brass olives are preferred. Soldered
or welded joints and �bite� type compression unions should not be used.
Fuel
feed connections to engine mounted components need adequate flexibility to
accommodate engine vibration. Flexible high pressure or low pressure pipelines
as described previously may be used depending on the maximum operating
pressure.
Joint
fittings and connections shall be compatible with one another and their mating
materials shall not create electrolytic corrosion.
Sizing
of Pipelines.
The
LPG liquid pipeline bore should be as small as possible to avoid undue rigidity
and sufficiently large to provide for maximum engine fuel demand.
It
should be recognised that an excess flow valve incorporated into an LPG service
valve will not protect the pipe in every eventuality, and it is therefore
emphasised that the liquid pipeline should be as small a bore as practicable
whilst meeting the maximum fuel requirement of the engine. In the event of a
liquid feed pipe fracture, the engine will stop from a lack of fuel, and the
electric valve at each tank will, therefore, be de-energised to provide
complete shut off.
Pipeline
Location.
Every
pipeline feeding from or into the fuel tank should follow the safest route and
be protected from impact, preferably below the body shell where it may be
shielded by structural members of the vehicle.
Pipelines
should be remote from the vehicle exhaust system and not closer than 250mm.
Where
the requirement� of the above is not
practicable, the pipeline must be shielded from the vehicle exhaust system by a
suitable heat shield.
Pipelines
should be effectively secured to the chassis frame or body shell at intervals
of not exceeding 600mm and in such a manner to be protected against excessive
strain and vibration.
Pipelines
shall not be installed where any part is permanently hidden from view and
cannot be inspected regularly.
The
positioning shall be such that pipelines will not be affected by suspension or
propshaft movement and shall not be located at jacking points.
Flexibility.
Pipelines
shall be installed so as to take up safely the relative movement between
chassis/body and the fuel system components and secured in such a manner so as
to prevent wear taking place. All runs of rigid pipelines between components
shall be installed with gentle curves, U bends or loops to provide flexibility.
Pipeline
Over Pressure Protection.
Every
section of LPG liquid pipeline between positive shut-off or lock-off valves
should be protected against resultant damage from over pressure due to liquid
thermal expansion.
Hydrostatic
relief valves, where fitted, should be vented away from the vehicle exhaust or
people, to open air.
����������������������������� LPG CONTROL EQUIPMENT
Purpose.
The
control equipment comprises components which are necessary to supply the LPG in
a state, either vapour or liquid, and at the pressure required by the engine
design and the fuel management system and to ensure safe and efficient
operation under all foreseeable modes of vehicle operation and use. Where an
alternative fuel system is installed (bi-fuel), neither shall impair the safety
or efficiency of the other.
Components
for all Engines.
Installation
The
LPG control equipment should be:_
Installed
in positions that are easily accessible for routine inspection, maintenance and
adjustment.
Securely
mounted and reasonably protected by location from accidental damage.
As
remote as possible from the engine exhaust system or protected therefrom by a
heat shield.
No
closer to any electrical equipment capable of sparking than is avoidable.
Filter.
Systems
in which components are susceptible to mal-function or damage from solid
particulate matter may need a filter of suitable mesh in the fuel supply or
such other device which will protect these components. Some components have
integral filters or devices.
Lock-off
Valve.
Immediately
after any filter and upstream of any pressure reducing regulators there should
be installed an efficient lock-off valve.
The
lock-off valve should be designed for automatic closure whenever there is no
fuel demand from the engine.
The
lock-off valve should be capable of automatically opening to relieve excess
hydrostatic pressure generated on the engine side of the valve.
Automatic
Safety Controls.
Safety
control systems shall be���������������
by at least two means, either of which shall cut off the LPG supply, and
at least one of which shall operate if the engine stops for any reason.
Various
methods can be adopted to meet these requirements. The following are examples:-
A
pressure regulator designed to give total closure on zero engine manifold
depression.
A
manifold pressure sensitive switch, normally open at zero depression, connected
in series with the electric supply to the lock-off valve.
An
oil pressure sensitive switch open for zero oil pressure, connected in series
with the electric supply to the lock-off valve.
An
ignition coil triggered switch in the electric supply to the lock-off valve
which is open when the coil is de-energised.
The
electrical switches controlling the lock-off valve shall be connected in� series
With
the electrical supply to the solenoid shut-off valves at the fuel tank(s) to
provide simultaneous shut-off.
The
electrical switch or mechanical means used to bypass a device as defined above
to facilitate engine starting or tuning should require continuous manual
pressure to operate and should automatically return to the off position.
For
large passenger carrying vehicles see next section.
Additional
safety controls in the fuel system may be incorporated eg, inertia cut-off,
tilt switches, some of which are required by law for buses. See next section.
Components
for Non-fuel Injection Engines.
Vaporisers.
Vaporisers
for automotive use normally utilise heat from the engine coolant system.
Where
water circulation is employed.
A continuous
flow of water should be ensured which is not subject to interruption by
operation of the vehicle heater controls.
The
design of the water jacket of the vaporiser should take into account the
possibility of internal expansion resulting from water freezing and shall be
resistant to antifreeze.
The
use of exhaust gas/LPG heat exchangers are not recommended.
Every
vaporiser should be constructed of materials suitable for use with LPG and be
capable of withstanding the maximum pressure likely to be encountered in
service.
Pressure
Regulators.
LPG
systems have one or two stages of pressure reduction. The pressure regulators
and the vaporiser may be separate units but frequently are combined into a
single unit referred to as a converter.
The
first stage regulator should reduce the pressure to a valve appropriate to the
second stage regulator inlet pressure.
The
second stage regulator should be designed to give the pressure required at the
carburettor, gas-air mixer or injectors.
Every
pressure regulator should be constructed of materials suitable for use with LPG
and capable of withstanding the maximum pressure likely to be encountered in
service.
�
Carburettors
and Adaptors.
The
Carburettor or adaptor is a gas/air mixing device in which the gas and air are
metered in the correct proportions for combustion. The choice of carburation
deprnds on the engine layout and application:-
Single
fuel-� applies where complete conversion
to LPG is effected, and a purpose designed LPG carburettor may be employed.
Bi-fuel-� applies on an engine which may be supplied
with an alternative fuel, normally petrol, the engine operating wholly on one
or other fuel according to choice.
Components
for Vapour Phase Fuel Injection.
Vaporiser.
The
fuel is changes to a vapour by the use of water heat and then is transferred
under pressure to a distribution valve that feeds the vapour to the injectors.
The essential requirements are the same as for a non-fuel injection system.
Distributor.
The
distributor shall be designed to provide the fuel to the injectors at the right
time and quantity and linked into the electronic control system via the Lambda
sensor.
Safety.
The
unit shall be designed to fail safe in any condition and is triggered
electronically.
Components
for Liquid Phase Fuel Injection.
Fuel
Feed System.
The
essential difference between the fuel feed system for a liquid fuel injection
system and a non-fuel injection engine (carburettor) or a vapour injection
engine is the absence of a vaporiser.
Fuel
Feed Pump.
A
pump is required to raise the fuel pressure, which will otherwise be at the
vapour pressure of the liquid in the fuel tank, to a sufficiently high pressure
to ensure it remains liquid throughout the fuel system allowing for heat gain
in the vicinity of the engine when running and to avoid hot restart problems
due to heat soak after shut down, or at switch over, if it is a bi-fuel system.
Pump
external to the fuel tank.����� Feed
from the bottom of the tank or from the top via a dip tube. In either case the
suction line should be gererous in diameter and as shot as possible to avoid
pump damage from cavitation.
Submerged
pump in the fuel tank.��� This avoids
the likelihood of cavitation.
Pressure
Control.
To
provide a constant feed pressure to the injectors, a pressure controller is
normally provided. This may form part of the management system of the engine or
the conversion equipment.
��������������� REQUIREMENTS
FOR BUSES AND MINIBUSES
Regulations.
The
Road Vehicle (Construction and Use) Regulations 1986 call for special
requirements over and above those elsewhere in this Code relating to fuel
systems for buses and minibuses. Some buses and minibuses may be classified as
Passenger Service Vehicle (Conditions of�
Fitness, Equipment, Use and Certification) Regulations 1981, generally
referred to as C.O.I.F., being the conditions of Initial Fitness. These also
apply to some vehicles which are not buses or minibuses as defined but carry
passengers who pay individually.
PSVs
are required to be inspected by the Department of Transport, Vehicle
Inspectorate, Swansea, before entry into service.
This
section applies to buses and minibuses, but if they are to operate as PSVs the
legal requirements for the fuel system should be discussed with the Vehicle
Inspectorate Department of Transport at an early stage.
Where
the following requirements are taken from the Passenger Service Vehicle
(Conditions of Fitness, Equipment, Use and Certification) Regulation, they are
indentified by (C O I F ).
Fuel
Tanks.
The
LPG fuel tanks, pipework arrangements, associated fittings and valves shall be
located to comply with previous location guidelines and the following special
requirements:-
Fuel
tanks shall not be situated within 600mm of the entrance/exit on a vehicle with
more than 12 passenger seats nor within 300mm of any entrance/exit on a vehicle
with 12 passenger seats or less (C O I F 13).
Fuel
tanks may be externally mountes or may be within the passenger compartment only
if suitably enclosed and protected . (C O I F 13).
Fuel
tanks mounted beneath a vehicle shall:-
Preferably
be at least 500mm inboard of the sides of the vehicle or on the inside of the
chassis longitudinal frame members where applicable. If this location is not
technically possible, it is permissable to locate LPG fuel tanks outboard of
this, but within the width of the vehicle, in which case, suitable caging or
structural fixtures shall be provided to protect them� and their associated fittings from severe side impacts.
Have
adequate ground clearance in line with the vehicle manufacturers
recommendations for laden and unladen use.
Fuel
tanks for vehicles over 5 tonnes Gross Vehicle Weight shall be situated between
the front and rear axles.
Fuel
tanks shall be situated as far as practicable from the exhaust system. If the
clearance is less than 250mm adequate shielding against heat radiation shall be
provided.
Roof-mounted
fuel tanks shall comply with guidelines already set out. PSVs need to be
assessed for the legal requirements for stability. (C O I F 6).
Tilt/inertia
Cut-off switches (applies to all buses).
A
vehicle tilt switch and an inertia switch are required both of which shall
cause the
electric
solenoid valves at the outlet of each tank to close.
The
tilt switch shall cause the fuel tank valves to close when the vehicle body
angle of tilt to the vertical is greater than 35 degrees for single deck
vehicles, or 28 degrees for double deck vehicles.
The
inertia switch shall cause the fuel tank valves to close in the event of
deceleration of the vehicle exceeding 5g. The valves shall remain closed after
actuation until the inertia switch is manually reset.
Fuel
Tank Fill Connection.
The
filling point shall be accessible only from the outside of the vehicle (C O I F
13).
For
vehicles with less� than 12 passenger
seats, the filling point shall not be at the rear of the vehicle. (C O I F 13).
The
fuel tank fill connection shall not be within 300mm of any door or other
aperature into the vehicle interior (C O I F 13).
The
fuel tank fill connection shall not be located within 500mm of the exhaust
outlet.
Pressure
Relief Valve (PRV) Discharge.
The
discharge shall be directed downwards so as not to impinge on any part of the
vehicle and shall be arranged as far as practicable so as to be clear at all
times of the vehicle flooring, tyres, wheel arches, fuel tanks, manifolds and
exhaust systems.
LPG
Fuel System Relative to Vehicle Interior Apertures.
The
design, location and installation of the LPG fuel system shall be arranged so
that no leakage from the LPG fuel system shall enter the vehicle interior.
The
PRV discharge shall be directed as far away as is necessary from all openings
and apertures into the vehicle to avoid leakage into the vehicle interior and
so as not to interfere with people exiting from the vehicle in an emergency
when the PRV may be venting and so that no fuel overflowing or leaking can
accumulate on any woodwork or other part of the body such that it might be� readily ignited.(C O I F 13 (2) ).
Fuel
feed Pipe.
The
LPG feed pipework shall comply with guidelines already set out and shall not
pass through the passenger or driver compartments.
Manual
External Fuel Cut-off.
A
device shall be provided� by means of
which the supply of fuel to the engine can be readily cut off. The means to cut
off shall at all times be readily accessible from outside the vehicle and shall
be operated by hand. The location of the means of cut off shall be clearly
marked on the outside of the vehicle, and indication of the function and means
of operation to the cut off shall be provided nearby. The �off� position shall
be clearly indicated.(C O I F 13 (1) d).
The
fuel cut off may be provided by any combination of the following:-
A
manual device, accessible from outside the vehicle, which directly or
indirectly closes a valve in the LPG supply and simultaneously for a bi-fuelled
vehicle, cuts off the petrol feed.
Closing
of the externally operated battery isolation switch (where provided), which in
turn, results 8in the closure of the valves.
Closing
of an LPG fuel pipe manual valve located near to and upstream of the vaporiser.
Fuel
Gauges.
A
dashboard fuel gauge shall be provided. For multiple tanks one gauge for each
tank is recommended. They should read �FULL� at 80% of the tanks contents.
������������ COMMISSIONING,
MAINTENANCE AND INSPECTION
Installation
and commissioning of the fuel supply system should only be carried out by and
supervised by LPGA �Approved� competent persons adequately trained in LPG
automotive installation work and conversant with the properties of LPG.
Leak
Test.
Except
as described below , the complete system, including the tank(s) and all joints,
should be tested with air or inert gas at a pressure not less than 6 bar gauge,
but not more than 90% of the fuel tank design pressure. Soap solution or a
proprietary leak detection fluid, or other method of at least equal
sensitivity, should be used.
If
the fuel tank(s) and fittings are tested independently of the remainder of the
system, and charged with LPG, the remainder of the system should be tested
separately as above before connection to the tank(s) and the final
connection(s) then leak tested at the available tank pressure.
Charging
the Fuel Tank and System with LPG.
Subject
to the elimination of all leaks, the fuel tank(s) may be charged with LPG. It
is good practice to reduce the oxygen content of the tank(s) to 10% or less by
volume before introducing LPG. This can be achieved by introducing an inert gas
eg, nitrogen or carbon dioxide dilution of the air in the tank(s) until the
required end point is reached. When charging the tank(s) with LPG, the inert
gas/air/LPG� vapour, should be vented or
discharged in a safe place into the open air, and away from any sources of
ignition. This shall continue until the inert gas/air has been eliminated.
Testing
the Fuel System.
A
final leak test should be carried out on any joints not previously tested under
LPG pressure, once LPG has been introduced.
Testing
of controls under static conditions may be undertaken at this stage.
Road
test.
Following
the engine tuning, the vehicle should be given a thorough road test for
satisfactory performance. Bi-fuelled vehicles should be subjected to fuel change
over tests to ensure smooth transition.
Final
Certificate and Documentation.
A
competent person responsible for ensuring compliance with the Code of Practice
and relevant Statutory Regulations should, upon satisfactory completion of all
tuning and tests, issue a signed certificate of conformity for the purchaser.
The
vehicle owner should be provided with a Drivers Operation Manual which should
include the Certificate of Conformity with a recommendation that this is
carried in the vehicle at all times, for examination by authorised enforcement
agencies.
The
vehicle owner should be informed that the Department of Transport, DVLA, need
to be notified of the material change to the vehicle which must be noted on the
vehicle registration document.
Vehicle
owners/operators need to ensure that a Special Vehicle Order has been obtained
for any feature of the vehicle fuel system which does not comply with the Road
Vehicle (Construction and Use) Regulations 1986 or as amended. See �Foreword�.
Passenger
Service Vehicle (PSV) operators need to apply to the Department of Transport
Vehicle Inspectorate, Swansea, to ensure the Certificate of Initial Fitness is
valid for putting the LPG fuelled vehicle into service.
Vehicle
Marking.
LPG
powered vehicles should be fitted with a conspicuous durable marking informing
that the vehicle operates on LPG and indicating the tank location and the
position of the shut-off valves. The marking shall be of a durable type
material.
The
marking should be displayed at the front and rear of the vehicle. The preferred
locations are adjacent to the excise tax disc on the front of the vehicle and
on the off-side windscreen at the rear of the vehicle.
Maintenance
and Inspection.
�The service manual for LPG fuelled vehicles
should specify regular service requirements for the LPG fuel system or the
additional requirements in the case od bi-fuelled vehicles.
Every
service shall include a check of the condition of all valves and connections
for corrosion, damage or leakage, and corrected or replaced as necessary.
At
5 year intervals � Flexible pipework should be replaced unless proved suitable
for further service.
Fuel
Tank(s).
Examinations
and tests shall be carried out by a competent person.
Every
5 years an external visual examination shall be made of the tank(s) and its
fittings, including the pressure relief valve, for signs of deterioration,
corrision or leakage.
Every
15 years� -�� The tank(s) shall be subjected to an hydraulic pressure test and
marked with the date and the testing authority symbol.
The
accuracy of the 80% stop fill valve should be verified whenever the fuel tank
is emptied by using a re-fuelling meter.
Garaging,
Repair and Maintenance.
Vehicles
fuelled with LPG may be parked, serviced and repaired inside garages provided
that the following conditions are observed:-
Only
trained and competent personnel on the use of LPG as a road vehicle fuel should
be allowed to work on the vehicle engine or fuel system.
There
shall be no leaks in the fuel system and the fuel tanks shall not be filled
beyond the 80% maximum level.
Such
vehicles shall not be parked within 3m of sources of heat, open flames or other
sources of ignition.
LPG
fuelled vehicles being repaired in garages, unless the fuel is required for
engine operation, shall have the fuel tank(s) shut-off valve closed and the LPG
fuel in the service line exhausted by running the engine or, if this is not
possible, by disconnecting, in the open air, where the LPG cannot accumulate.
Vehicles
undergoing repairs involving welding or the application of heat, to any part
within 1m of the fuel tank, shall have the fuel lines emptied and the tank
removed or shielded from the source of heat.
If
the vehicle is to be repaired over an open pit, the pit shall be adequately
ventilated. It is recommended that lighting needs to be safe to use in a zone 2
area and that gas detectors are permanently fitted at the bottom of the pit.
These
should be checked daily.
Vehicles
shall not be put through a low bake repainting oven or similar heating process
unless the entire LPG system is safely removed or rendered gas-free.
Transfer
and Refit of the LPG Fuel System.
Whenever
this takes place, the completed system should be tested and inspected prior to
re-installation and rectification work, as necessary, carried out.
Demounted
fuel tanks containing LPG should be handled with care and stored in accordance
with Code of Practice No. 7.
All
non-flexible pipelines should be replaced.
All
flexible liquid phase hoses over 5 years old should be changed or re-tested in
accordance with production proof tests in BS4089 or equivalent.
Consideration
should be given to exchanging the relief valve of the fuel tank whenever it
might be refitted to a different vehicle or if vehicle ownership changes,
whether or not this coincides with a 5 or 15 year inspection.
Vehicle
Scrapping.
LPG
fuel tanks must be removed from a vehicle before the vehicle is sent to be
scrapped. Tanks should be handled with care and stored in accordance with Code
of Practice No. 7 � �Storage of full and empty LPG cylinders and cartridges�.
Tanks to be scrapped shall be destroyed in accordance with BS5430 by or under
the supervision of a competent person and in a manner rendering them
unserviceable
for
holding gas.
Hotwork.
No
hotwork eg, welding, cutting or bending should be carried out on vehicles
unless the risk of affecting the LPG tank or system has been eliminated. This
may require the removal of the tank or system.
All
persons concerned with the storage and handling of LPG should be familiar with
the following characteristics and hazards:-
LPG
is stored normally as a liquid under pressure, is colourless and its weight as
a liquid is approximately half that of an equivalent volume of water.
LPG
vapour is denser than air, commercial butane being about twice as heavy as air
and commercial propane about one and a half times as heavy as air. Therefore,
the vapour may flow along the ground and into drains, sinking to the lowest
level of the surroundings and be ignited at a considerable distance from the
source of leakage. In still air any vapour will disperse slowly.
When
mixed with air, LPG can form a flammable mixture: the flammable range at ambient
temperature and pressure extends between approx. 2% of the vapour in air at its
lower limit and approx. 10% of the vapour in air at its upper limit: within
this range there is a risk of explosion. Outside this range any mixture is
either too weak or too rich to propagate flame, but over rich mixtures can
become hazardous when diluted with air. It should be noted that at pressures
greater than atmospheric, the upper limit of flammability is increased but the
increase with pressure is notlinear.
Small
quantities of the liquefied gas can give rise to large volumes of vapour/air
mixture and thus cause considerable hazard. A suitable, properly calibrated
explosimeter� may be used for testing
the concentration of LPG in air. ON NO ACCOUNT SHOULD A NAKED FLAME BE USED TO
DETECT A LEAK.
LPG
vapour is slightly anaesthetic and may also cause suffocation if present in
sufficiently high concentrations.
LPG
is normally odorised before distribution by the addition of an odorant such as
ethyl mercaptan or dimethyl sulphide, enabling detection of smell of the gas as
concentrations down to one-fifth of the lower limit of flammability
(ie,approximately 0.4%of the gas in air).
Escape of LPG may be noticeable otherwise than by smell.
When the liquid evaporates, the cooling effect on the surrounding air causes
condensation and even freezing of water vapour in the air. This effect may show
itself as frost at the point of escape and thus make it easier to detect an
escape of LPG. Because of the refractive index of LPG, leaks can sometimes be
seen as a �shimmering�.
APPENDIX��� 5
STATUTORY
INSTRUMENTS ETC.
The
Public Vehicle Act 1981
The
Road Vehicle (Construction and Use) Regulations 1986 (and Amendments)
The
Public Service Vehicle (Conditions of Fitness, Equipment, Use and
Certification) Regulations 1981
ECE
Regulation 67
The
Department of Transport Vehicle Inspectorate, Swansea.
STANDARDS.
BS
4089��������������� Specification for
hoses and Hose Assemblies for Liquefied
����������������������������� Petroleum Gas.
BS
5045��������������� Specification for
Steel Containers of 0.5 L up to 450 L
� Part 2������������������ Water Capacity with Welded Seams.
BS
5430��������������� Periodic Inspection,
Testing and Maintenance of
����������������������������� Transportable
gas Containers (Excluding Dissolved Acetylene
����������������������������� Containers).
BS
6362��������������� Specification for
Stainless Steel Tubes suitable for Screwing
������������������������� ����In accordance with BS 21. Pipe Threads for
Tubes and
����������������������������� Fittings Where
Pressure-Tight Joints are made on the Threads
BS
6956��������������� Jointing Materials
and Compounds
�� Part 6����������������� Jointing Compounds for 3rd Family
Gases
�� Part 7���������������� Anaerobic Jointing Compounds for 3rd
Family Gases
EN
549���������������� Specifications for
Rubber Materials for Seals and Diaphragms
����������������������������� For Gas
Appliances and Gas Equipment
Pr
EN 751������������� Jointing Compounds
(will supersede BS6956)
DIN
1787�������������� Copper � Half
Finished Products.
DIN
17671������������� Wrought Copper and
Copper Alloy Tube Properties
ISO
8789��������������� Rubber Hoses and
Hose Assemblies for Liquefied
������������������������������� Petroleum Gas
in Motor Vehicles. Specification.
CODES
OF PRACTICE.
LPGA
COP 15����������� Valves and Fittings
for LPG Service
�������� Part 1������������������ Safety valves.
LPGA
COP 7�������������� Storage of Full and
Empty LPG Cylinders and Cartridges.
��
This
Code of practice has been drawn up in consultation with the department of
Transport. Motor Vehicles in the UK are required to comply with Road Vehicle (Construction
and Use) Regulations 1986 which includes specific requirements for LPG fuelled
vehicles. These are supplemented by further requirements if they are to operate
as Passenger Service Vehicles which are set out in The Public Service Vehicle
(Conditions of Fitness, Equipment, Use and Certification) Regulations 1981.
All
the above apply both to original manufacture and to subsequent modifications,
such as LPG conversions.
An
amendment to the 1986 Regulations during 1997, will, it is anticipated, mean
that compliance with this Code of Practice will also mean compliance with those
Regulations.
Vehicles
which do not comply with the 1986 Regulations, as amended, may only be used on
the road by virtue of a �Vehicle Special Order� issued under Section 44 of The
Road Traffic Act 1988 by the Department of Transport � Vehicle Standards and
Engineering Division.