Flameproofing

FLAMEPROOFING

OPERATING IN HAZARDOUS ENVIRONMENTS

With today's increasing emphasis on total quality and safety in the workplace, employers and staff are becoming increasingly aware of the dangers presented when dealing with hazardous materials and environments.

Companies in the food, petrochemical and agriculture industries are regularly faced with dealing with explosive gas atmospheres in which operating a forklift can be hazardous. This is where a flameproofed forklift can come into effect.

Areas where explosive gas/vapor mixtures exist such as oil refineries and paint handling are prime examples where a flameproofed vehicle is invaluable. These atmospheres are designated according to Zones.

Zone 0 areas always contain hazardous atmospheres, and it is illegal to operate any type of traction vehicle in these zones. Zone 1 areas are likely to contain gas mixtures, whilst Zone 2 areas are unlikely to contain explosive gas mixtures during the course of operation but still require safeguarding against accidental exposure.

Hazardous areas can also be created due to combustible dusts such as in grain storage areas and polymer handling. Dust zones are classifications as Zone 20 and 21, with Zone 20 having the highest density of dust present.

DIESEL FORKLIFT FLAMEPROOFING

Diesel forklifts are one of the options presented to buyers when considering a unit for their materials handling needs. By their very nature, petrol and LPG units, which require spark ignition, are unsuitable for flameproof areas.

In a typical conversion all electrical equipment is removed such as lights, alternator, brake lights, indicators, dash instruments and battery. If required, lights can still be run by adding a self excited flameproof alternator, which generates power from the belt drive connected to the diesel engine. Then, depending on the operating areas we can either add full flameproof enclosed lights to comply with Zone1 or modify the existing lights to comply with a Non-sparking protection technique which is safe for Zone2 only.

The electric directional change used on some forklift models is replaced with a hydraulic gear change mechanism and any electrically operated instrumentation is either removed or replaced with mechanical equivalent gauges.

Sometimes engine heads need modifying such as when the standard manifolds do not comply with Zone1 minimum flamepath requirement of 12mm. This can be achieved by welding additional metal to the heads and re-machining to increase the gasket contact area ensuring no spark transmission to the surrounding environment. A water cooled exhaust manifold is fitted to help it achieve a T4 temperature rating. Also, a flame trap and strangler is fitted to the inlet manifold to protect against ignition due to backfiring.

To prevent the potential for sparks from exiting the exhaust and to cool the exhaust gasses the exhaust is also run through a parallel plate flame arrestor, then a water wash box. All exposed portions of the exhaust are coated with fire retardant insulating tape.

Integral to the Forktorque Flamesafe system is the use of sentinel shutdown equipment. Should the wash box or engine temperature exceed a set temperature, the sentinel equipment automatically shuts down the motor, cutting out the fuel supply.

The units are then tested to procedures outlined in Australian Standards to verify its temperature rating, which is usually to a T4 (135ºC maximum) and the spark arrestor is rated to a Group IIB gas level. the trucks static discharge through the tyres and antistatic belts are also tested.

Certified parts are always used where appropriate. Our exhaust systems have been tested and approved by and independent testing laboratory and the spark arrestor is certified to a Group IIB gas level. Air start motors and the sentinel system are also approved. In saying this we can only fully certify our Zone 2 modifications. If the customer requires third party certification for Zone 1 modifications we can arrange on their behalf but must be at the customers expense. This is a considerable expense and is not included in the general quotation of Zone 1 modifications.

Ahead of our local competitors we have chosen to fall in line with International standards that have not been deemed mandatory in Australia so far but we feel that there is a strong argument to not allow the use of on-board compressors in hazardous areas as they have the potential in themselves to create an explosion. A compressor is generally installed to a diesel air start unit to charge the air tank whilst the unit is operating. This ensures the air tank is always charged. The argument is though that even without the presence of a spark the compression of potentially hazardous air and the increased temperatures inside the compression chamber is arguably enough to create ignition.

A safer form of air start is the remote method. This allows the unit to be installed with an air starter and an onboard compressor but compressed are needs to be accessed externally. This way the air can be fed into a hazardous area but the air compression can be done in a safe zone eliminating the potential for compressing hazardous gasses. The air tank can usually store enough air pressure for three starts before recharging. The tank can be installed above the overhead guard as pictured or behind the guard for low clearance access. Behind the guard sometimes poses a rear vision problem on small trucks but generally they are quite acceptable.

Also, another starting option is a remote battery start. Unlike the remote air start this method requires that the unit be started in a safe zone outside of any potential hazardous gas areas. The unit retains the original starter motor but the battery is removed. The original battery is supplied on a portable trolley and a quick connecting Anderson plug which should be permanently stored in a

Cleaning the flametrap which is located in the washer box needs to be a daily chore. If this maintenance is not done regularly it will block the exhaust and may damage the washer box from buildup of back pressure. Another option available which can save you maintenance time is a constant water level system. This does a way with the flametrap because constant water is maintained in the washer box from a water reserve, preventing ignition to the atmosphere. The system will discharge some water from the exhaust end pipe which sometimes is not appropriate for some applications.

ELECTRIC FORKLIFT FLAMEPROOFING

Electric forklifts are becoming increasingly popular as people are being made more aware of the capabilities and advantages that they can offer, including reduced noise, emission and lower running costs. In order to keep up with customer requirements, Forktorque now offers flameproofing on virtually any model of electric fork truck.

Flameproofing an electric truck, as with diesel trucks, requires strict adherence to numerous standards including AS2359 (Industrial Trucks), AS2430 (Classification of Hazardous areas), and AS2380 (Electrical equipment for explosive atmospheres).

Unlike diesel trucks, electrical forklifts cannot have their electrical equipment removed. Thus, flameproofing an electric vehicle requires the following techniques to be employed:

Intrinsic safety

All equipment is to be made intrinsically safe. The term intrinsically safe refers to the fact that a device is not capable of generating a spark of sufficient magnitude or thermal effect to initiate an explosion. This is done by installing a suitable safety barrier, typically wired through a flameproof box between the power supply to the apparatus requiring protection.

Right: An open flameproof box showing a series of safety barriers controlling forklift functions. Also, contactors and relays are installed in the flameproof box.

Flameproof enclosure

Any equipment that cannot be made intrinsically safe (for the main part, contactors, relays and electric motors), must be encapsulated in explosionproof containers. these containers will withstand an internal explosion if it were to occur and also prevent ignition to the surrounding environment due to its flame-path design. All our explosion protection boxes are manufactured in accordance with current standards and a select range have been tested by an independent certified laboratory for compliance which have come at a huge expense. To keep the cost down on conversions and to be able to supply at a reasonable turnaround time we test all non-standard size explosion protection boxes in-house in accordance to current standards. Externally prepared certifications can be supplied for all of these products upon request at the clients expense.

Left: Hydraulic and drive motors have been encapsulated in flameproof enclosures. This is typically used in Zone 1 areas and on DC motors in Zone 2 areas.

Right: Electronic displays are also encapsulated and have a thick polycarbonate front panel for viewing.

Increased safety

Falling in line with European standards, Australia has adopted an increased safety standard which helps us to achieve acceptable flameproofing for electric motors with sufficient ingress protection techniques. This technique allows the motor to breath and reduces overheating problems that explosionproof containers sometimes introduce to the system.

Increased safety techniques generally are one of avoidance of arcs, sparks and hot surfaces. it applies only to electrical apparatus of which no parts produce arcs or sparks or exceed the limiting temperature in normal services. This technique is suitable for both Zone 1 and 2.

Right: Ingress protection used on Increased safety modified motor

Non-sparking

In zone 2 applications we can comply to a non-sparking standard in alternating current style motors. This can be achieved by a combination of using energy limiting components and ingress protection techniques. This can also apply to light fittings. Direct current motors are still required to comply with a flameproof enclosure standard. Like in increased safety, non-sparking techniques address heat concerns and ingress of dust and water in quantities that could be harmful to the electrical component.

Battery and battery containers

Batteries are modified to comply with necessary creepage distances and guarding manufactured to satisfy ingress protection requirements without disturbing ventilation.

Right: Creepage distance achieved with panels between cells.

Far right: Anderson plugs are protected by a flameproof enclosure in Zone 1 areas.

An additional advantage of electric flameproofs is that they are much cleaner and easier to maintain than diesel trucks, as there are no corrosive mixtures or contaminant buildups involved. Below are some more photos of typical electric conversions we have completed to operate in Zone 1 & 2.