Forklift truck operation in hazardous environments
25/02/2021
Cat® Lift Trucks can confidently say that its forklift trucks are suitable for most normal materials handling circumstances, but there are situations where special treatment is necessary.
Chemicals and explosives are obviously hazardous, as are industrial gases, for example, but even everyday items such as foodstuffs or drinks can also be dangerous. In the right – or rather, wrong! – conditions, even baking powder and flour can be explosive. If customers are operating in dangerous or challenging environments, then help and advice is at hand.
“There is an extensive array of legislation within the European Union that covers hazardous materials and dangerous environments, along with the measures that are required to manage them and make them safe,” said Matthew Shirkie, Industrial Commercial Manager, EMEA, with Pyroban. Other countries have their own regulations and some – such as China’s – can require modifications over and above Europe’s.
“The EU’s legislation is under two ATEX (Atmosphères Explosives) directives: ATEX 1999/92/EC, which covers industries that operate with potentially explosive atmospheres; and ATEX 94/9/EC, which deals with industries that supply equipment into hazardous areas.”
The two directives have been applied in individual EU states under national laws; DSEAR (the Dangerous Substances and Explosive Atmospheres Regulations), for instance, is the United Kingdom’s implementation of ATEX.
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Avoid bright sparks
Some of the requirements look like basic, sensible precautions – for example, ATEX 1999/92/EC requires companies to prevent the formation of explosive atmospheres in the workplace, or (where this is impossible) avoid the ignition of explosive atmospheres. But what the regulations do is to provide a framework and lay out clear common standards, which apply across the EU. While some materials will be recognised as potentially hazardous to handle even by lay people and non-experts, some are not so obvious. “The danger with flour, for example, is that fine particles of it can be explosive if suspended in the air in a confined space. A simple spark from an electric lift truck can set off a catastrophic explosion,” said Shirkie. “The first step in avoiding disaster and ensuring a safe working environment is the completion of a ‘hazardous risk assessment’. This will cover the likelihood of explosive atmospheres and any source(s) of ignition. A systematic review will identify, and classify into zones, areas within the premises where potentially explosive atmospheres exist.”“The danger with flour, for example, is that fine particles of it can be explosive if suspended in the air in a confined space. A simple spark from an electric lift truck can set off a catastrophic explosion,”
The zones themselves will identify the standard of certified equipment to be installed within them. They are: Zone 1 (high risk gas/vapour); Zone 2 (medium risk gas/vapour); Zone 21 (high risk powder/dust); and Zone 22 (medium risk powder/dust). [See Hazardous Area Classification chart]
‘Effective ignition sources’ – i.e. things that could initiate explosions – range from open flames and lightning strikes to radiation and – importantly, in the context of lift trucks – mechanically generated friction sparks and electric sparks among others.
“Hazardous area zones have to be identified and clearly marked, according to their classification, and ATEX 94/9/EC-compliant explosion-proof equipment, such as forklift trucks, diesel engines, access platforms, sweepers and cranes must either be selected or converted so that they are suitable for use in those areas,” Shirkie explained. “The classification of such equipment is directly matched to the risk in the zones in which they will be used.”[See Hazardous Area Classification chart]
Train and modify
Safe operation requires that forklift drivers should be properly trained for hazardous operations but the equipment they are using must be suitable for purpose. Making them compliant is a conversion activity in which Pyroban Group specialises. It has facilities in the UK, Netherlands, China and Singapore that convert forklift trucks and other materials handling equipment to ensure ATEX compliance. “They must not have sources of ignition. Standard equipment has switches, hot surfaces and even static electricity from the seat,” he continued. “Pyroban goes right back to the bare chassis and assesses every element of the equipment, including brake linings, tyres, electrical and lighting systems, wiper motors and engine temperatures. They are rebuilt and certified as safe from causing explosions. Pyroban tries to achieve certification with minimum modification.” Zone 1 areas can be serviced by Category 2G electric trucks still equipped with their original DC motors, which are completely enclosed within explosion-proof casings. Category 3G trucks, which operate in Zone 2 areas, are typically fitted with enclosures on DC motors which prevent gas penetrating for up to a minute. The Pyroban system also detects gas and shuts the truck down if necessary. AC motors are non-sparking in normal operation and use a different technology to the 60-second enclosure.
Cat® lift truck that has been prepared by Pyroban for ‘medium risk’ (Zone 2 operation) to Category 3G ATEX 94/9EC specifi cation.
Cool running
“Diesel trucks are modified so that the operating temperature of the engine is reduced below the required class level,” said Shirkie. “A water-cooled jacket cools exhaust gases, and temperature probes are fitted in order to monitor engine, exhaust gas and manifold temperatures.” Pyroban’s modifications also include spark arrestors and shutdown valves in order to inhibit ingestion of gases, which can cause overspeed running and potentially generate exhaust flame. “Once a truck has been modified to meet the necessarily high safety standards, the right maintenance is essential to ensure it stays that way,” he emphasised. “Any attention by untrained engineers is strongly discouraged as procedures that are not totally compliant can compromise the explosion-proofing in a matter of seconds.”Safe operation requires that forklift drivers should be properly trained for hazardous operations but the equipment they are using must be suitable for purpose.
Potentially explosive atmospheres are not the only challenges that forklift truck operators have to cope with. Heat and fine dust in aluminium smelters can clog up filters and accelerate wear in machine components. The heat has been known to melt rotating warning lights; a solution provided by Al Bahar, Cat® Lift Trucks’ dealer in the Middle East, was to provide an LED beacon with a different lens material.
And the electromagnetic fields around aluminium smelter pots are strong enough to wipe credit cards and interfere with electrical equipment; as a result, such operations use diesel trucks, even indoors, rather than battery-powered units. The diesel trucks are also less likely to ignite any fine bauxite powder that hangs in the air.
Modifications to ensure that air filters do not become clogged and that dust is kept out of the lubrication system are also part of the normal service. Even the tyres are special: they are solid pneumatic, providing the same shock-absorbing performance as normal units but without the risk of puncture.
At the other extreme, Cat® Lift Trucks has been a sponsor of a project from the University of Utrecht which sent a solar-powered vehicle to Antarctica. Whatever the challenge, across a range of situations and temperatures, Cat® Lift Trucks has the expertise to rise to it.
Hazardous area classification chart
Source : https://eurekapub.eu/health-safety/2015/04/14/forklift-trucks-in-hazardous-environments