Working on gas vehicles

Working on gas vehicles
General information and warnings
General information and warningsThis document describes work procedures on vehicles powered by CNG (Com-pressed Natural Gas) and LNG (Liquefied Natural Gas) vehicle gases.

IMPORTANT!

All work on the chassis must be carried out in accordance with ECE-R110 (all ver-sions published after 25 June 2014 are valid).Contact Scania before starting work on the gas system (e.g. for dismantling, assem-bling, adding or moving gas tanks, etc.).

Types of vehicle gas:

• CNG: Vehicle gas that is stored at room temperature at high pressure in gas form.• LNG: Vehicle gas that is cooled down to -162°C and stored as a liquid. When gas

is cooled down to its liquid state, its volume is reduced by more than 600 times, facilitating storage and transport. Vehicle gas is vaporised before it is used as fuel for the engine. LNG has greater energy density than CNG.

Scania Truck Bodybuilder 22:10-728 Issue 4 2021-05-11© Scania CV AB 2021, Sweden 1 (19)



WARNING!Vehicle gas comprises natural gas and biogas, both of which are mostly made up of methane. Vehicle gas is flammable and must be handled with great care.

WARNING!Place the vehicle in the workshop so that the gas vehicle can easily be pulled out of the workshop in the event of fire or other hazards.

WARNING!Deformation of coolant hoses and gas lines to the gas system leads to an increased fire risk. Deformation can prevent the engine’s coolant from reaching the gas system and gas panel. Ensure that coolant hoses and gas lines are not affected/deformed for any reason. Fit the cable ties very carefully so that deformation of the coolant hoses does not occur during operation.

WARNING!Do not loosen union assemblies when the system is pressurised




WARNING!If hot components are positioned at a distance of less than 200 mm from the gas sys-tem, a heat shield must be installed on the heat source.The distance between a heat shield fitted on retrofitted hot components and the gas system must be at least 100 mm.

WARNING!The exhaust gas temperature is higher for gas vehicles than for diesel vehicles, in-cluding during idling. For this reason, avoid positioning heat-sensitive objects (e.g. clothes, gloves, tools, etc.) on or near the exhaust system. Inform and train customers and drivers about the risks of positioning heat-sensitive objects on or near the exhaust system. The information must be included in the driver's instructions.

WARNING!If the work affects any part of the gas system, the affected parts of the gas system must first be emptied or de-pressurised and then declared free of gas leakage. Contact a Scania workshop for more information.

WARNING!Protect the gas system from temperatures above 60°C and major or sudden tempera-ture fluctuations.


Handling gas vehicles in the workshop


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Example of warning plate.

Handling gas vehicles in the workshopSafety precautionsComply with applicable local and ECE regulations when handling gas vehicles. For example:

• ECE-R110• National work environment legislation• Regulations governing work with pressurised vessels• Regulations on flammable and explosive goods

Smoking is prohibited in the vicinity of gas vehicles.

The actions below must always be carried out when working on a vehicle with a gas engine:

Make sure that the pressure in the tanks is as low as possible before driving the ve-hicle into the workshop, to avoid evaporation of methane gas. This is particularly im-portant at low outside temperatures, since the gas pressure will increase as the temperature increases.

Carry out leak tracing in the following areas before driving the vehicle into the work-shop:

• Fuel pick-up unit on gas tanks• Temperature-controlled safety valves on gas tanks• Exhaust pipe from the gas tanks to and from the manual shut-off valve on the gas

panel

Inform all personnel in the workshop of the basic risks of vehicle gas. Use warning plates to indicate that work with flammable fuel is in progress. The design of the warning signs must comply with local regulations and be written in the local lan-guage.




The gas tanks, gas lines and gas panel must be well covered with a fire blanket if hot work is to be carried out near the gas system. Hot work may only be carried out on the vehicle if the work does not affect any part of the gas system or the gas tanks.

Protect the gas system and gas tanks from sparks that may occur when working on or near the vehicle. Examples of work generating sparks include welding and metal-working.

Specific warnings for LNG vehiclesWARNING!

Liquefied natural gas, LNG (Liquefied Natural Gas), is very cold and goes down to temperatures of approximately -162°C. Physical contact with the gas can cause frost-bite. Equip yourself correctly when working in the vicinity of LNG.

WARNING!Prevent sparking through equipotential bonding between the person and the vehicle.




Boil-offGas may escape through the ventilation pipe when the LNG vehicle is stationary for a prolonged period in the workshop. This is due to boil-off. For this reason, make sure the boil-off gas is adequately vented out of the workshop.

More information on ventilation can be found under the heading Ventilation.

WARNING!The pressure is relieved automatically when the pressure reaches 16 bar.




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Examples of fusible links located on the gas tanks on CNG vehicles.

Safety precautions in the event of fire• Move the vehicle out of the workshop.• Never try to extinguish a burning gas flame. If there is no risk, try to switch off

the ignition to restrict the flow of gas to the engine.• Remove all material that could be ignited by the flame.

CNG vehiclesWARNING!

Do not cool fusible links on a CNG vehicle in case of fire, see illustration. Fusible links release at 110°C, allowing the gas to freely flow out. This prevents the gas pres-sure from becoming so high that the gas tank explodes.

LNG vehiclesWARNING!

Use a powder fire extinguisher. Do not use water or carbon dioxide to extinguish the fire as this will vaporise the LNG more quickly, thus intensifying the fire.




Chassis modificationWARNING!

• Hot components must not be fitted near valves and connections in the gas system.• The bodywork must not obstruct access to valves and connections in the gas sys-

tem.• The bodywork and lateral protection must not obstruct access to the gas tanks.• The installation of the bodywork around the gas tank mounting brackets must be

designed so that it is easy to remove and fit gas tanks during inspections or main-tenance. The distance between the bodywork, bed and gas tanks must be at least 230 mm.

• Be careful when drilling near the gas system. More information can be found un-der the heading Safety precautions.




≥200

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241

Minimum permitted ground clearance.

Ground clearanceThe minimum permitted ground clearance from the underside of the gas tank is nor-mally 200 mm and applies to laden vehicles with complete bodywork; see illustra-tion.

Gas tanksWARNING!

Protect gas tanks from temperatures above 60°C and major temperature fluctuations.

Gas linesWARNING!

• The gas lines must be kept clear of other components• Gas lines must not be deformed or damaged by other components• If components in the gas system show signs of damage, they must be renewed im-

mediately by authorised personnel; contact a Scania workshop• Brackets and attachments for pressurised lines and their components may not be

tightened or loosened. This involves a risk of explosion.




PaintingWARNING!

• Only metal parts in the gas system may be painted, with the exception of shut-off valves and various markings, which must not be painted over

• Gas lines must be marked in accordance with local guidelines and UNECE R110 regulations

• Protect gas tanks and gas systems from increased temperatures during painting

Exhaust systemWARNING!

• The silencer’s attachment must not be modified• Lines between the silencer and turbocharger must not be extended• The exhaust gas temperature for gas is higher than for diesel vehicles (the normal

temperature during idling can vary between 400°C-500°C)• If the exhaust system is positioned less than 200 mm from the gas system, a heat

shield must be used. The minimum permitted distance between the exhaust sys-tem and gas system components is 100 mm.

More information on heat shields can be found in the document Risk of fire in con-nection with hot components.


Declaring a gas vehicle leakage-free in the workshop


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Gas detector.

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Declaring a gas vehicle leakage-free in the workshopPreparatory operationsEnsure the following before starting work:

• That the personnel carrying out the work are aware of the risks of working with gas. That they have knowledge of how a gas detector works and is to be used.

• That the gas detector has been calibrated within the last 12 months. • That all hazardous areas are covered by the gas detector; see illustration. More in-

formation is found under the heading Work description.

Only applies to LNG vehicles: That vehicle gas from the vehicle’s ventilation pipe is routed outside using a hose.

More information is found under the heading Work description. That a warning plate is located at the outlet.

Gas detectors (part number 2 380 848) are available from Scania dealers.

If the measured value exceeds 0.2% LEL (Lower Explosive Limit) or 100 ppm:

Use the leak detection spray to verify and locate the gas leakage. Bubbles will form if the leak detection spray is applied in the event of leakage; see illustration. Gas leak-age must be rectified.

IMPORTANT!

A leak test must be performed in accordance with ECE-R110 for CNG vehicles and LNG vehicles.




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Routing gas out of the workshop.

Work descriptionNote:If possible, make sure that the LNG tank is empty or contains a maximum of 4 kg of gas. This is to ensure that the vehicle does not release gas when the pressure increas-es.

Drive the vehicle into the workshop:

1. LNG vehicles: Connect an evacuation kit (part number 2 987 685) or a hose to the ventilation pipe immediately after the vehicle has been driven into the work-shop; see illustration. Make sure the hose outlet is positioned outside the work-shop, see illustration.




5m

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2. Route the evacuation kit's hose reel or the hose end outside the workshop. The hose reel or hose end must be positioned 5 m from heat sources, buildings or oth-er flammable objects where the evaporated gas can cause damage; see illustra-tion. Also ensure that gas cannot flow into the workshop.

– When the engine is not running, the pressure in the LNG tank continually in-creases over time. This pressure increase is due to the temperature difference between the gas and the ambient temperature.

3. Carry out a visual inspection while also searching for gas leaks using the gas de-tector. Hold the gas detector sensor very close to the component or area being checked. More information about the components to be checked is found under the headings Searching for gas leakages on CNG vehicles and Searching for gas leakages on LNG vehicles.

WARNING!Contact a Scania workshop if the vehicle is leaking gas. Park the vehicle outside while awaiting remedial action.

IMPORTANT!

The evacuation kit (part number 2 987 685)for LNG must not be subjected to high pressure. For this reason, make sure that the gas tank pressure does not exceed 13 bar when connecting the tool.

If the LNG tank is empty, the vehicle must be moved using another vehicle. Remem-ber that the vehicle will likely need to be refuelled once the bodywork is complete. In this case, the vehicle must be transported to the nearest LNG station.




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2

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4454

4

5

4

Searching for gas leaks on CNG vehiclesComponents to be checked for leakage:

1. Union assemblies between the gas panel and the engine, including the fuel manifold

2. Union assemblies and components on the gas panel3. Union assemblies between the gas tanks and the gas panel4. Tank valves5. Refuelling

Also check the remaining connections related to the gas system.




1

6

2

1345 43

8 63

9

Searching for gas leaks on LNG vehiclesComponents to be checked for leakage.

1. Union assemblies in the gas fuel tank armature.2. Union assemblies between the gas tanks3. Union assemblies between the gas tanks and the gas panel4. Union assemblies and components on the gas panel5. Union assemblies between the gas panel and the engine, including the fuel

manifold6. For refuelling

Also check the remaining connections related to the gas system.


Ventilation


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VentilationLNG tank ventilationTo enable transport of the vehicle from the factory, a transport-mounted ventilation solution is fitted on certain vehicles.

The bodybuilder is responsible for final fitting and additional material. More infor-mation can be found under the following headings:

• Installation of the transport-mounted ventilation for LNG tanks• Final fitting of ventilation for LNG tanks

IMPORTANT!

Keep electrical cables and hydraulic hoses at a safe distance from ventilation pipes to prevent sparks and fire.


Ventilation


≤400

0-300

2

1

4

3

426

435

Final fitting of ventilation for LNG tanks1. Lift the ventilation pipe hose away from the transport bracket.2. Secure the hose with the ventilation pipe on a separate metal stay (1). The metal

stay is fitted by the bodybuilder between the cab and the bodywork, see illustra-tion:

– If the hose is too long, remove the ventilation pipe (2) and shorten the hose. Reattach the ventilation pipe using a hose clamp (3).

– The maximum permitted distance between hose attachment points on the met-al stay is 400 mm.

– The ventilation pipe should be positioned level with the cab roof. If the venti-lation pipe needs to be positioned below cab roof height, the maximum per-mitted distance between the cab roof and ventilation pipe is 300 mm.

– Attach a bowl-shaped plate (4) under the ventilation pipe opening to direct the gas upwards. This is obligatory for vehicles that are approved under ADR AT/FL.

IMPORTANT!

The installation must satisfy the requirements in ECE-R110. The ventilation must not be aimed towards other vehicles, exhaust pipes or air intakes such as air conditioning and air intakes for engines.


Ventilation


≥50≤100

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1

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1. Ventilation pipe2. Minimum permitted distance between ventilation pipe and heat shield3. Minimum permitted distance between heat shield and hot components

Ventilation pipe's distance from hot components

WARNING!Position the ventilation pipe at a safe distance from the exhaust pipe or hot compo-nents.Ventilation pipes (1) must be positioned at least 200 mm from exhaust pipes or other hot components.If a heat shield is used between a ventilation pipe and a hot component, the distance must be at least 150 mm. In this case, the minimum permitted distance between the heat shield and the hot component is 100 mm (3) and the minimum permitted dis-tance between the heat shield and the ventilation pipe is 50 mm (2); see illustration.


Ventilation


1

2

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19

1. Drain hole2. Heat-resistant cable tie

Pump installation on ED120P for gas vehiclesWhen a hydraulic pump is to be fitted on power take-off ED120P, a heat shield must be installed to prevent damage to the pump due to high temperatures.

Use Scania’s heat shield or a similar heat shield approved by Scania. The heat shield consists of an insulating fabric which is fitted around the power take-off and hydrau-lic pump, see illustration.

Instructions for fitting the heat shield:

1. Position the insulation with the drain hole (1) facing downwards2. Assemble the insulation with 5 heat-resistant metal cable ties (2)

Part informationThe parts are available from Scania dealers.

Part Part numberInsulation 1 926 885Cable tie 1 534 703


Documents

Working on gas vehicles