Safety in Flammable/Explosive Reactions and Distillations: Utmost care should be taken during storage, transport, hardling and reaction of explosive and flammable materials. Bulk storage of these chemicals come under purview of Chief Controller of Explosives. Free fall of flammable liquids should be avoided. Suitable dip pipe should be provided. All lines carrying flammable materials must be bonded by copper clamp and earthed. Continuity should be periodically checked and resistance to earth should be less than 1 Ohm. Pumps handling these chemicals should have brass or non-metal impeller to avoid sparks due to fiction. Flow velocity should not exceed 6 m/sec in pipeline to avoid static charge accumulation. Reaction of flammable chemicals including solvent distillation should be carried out at low pressure or under vacuum or inert blanketing. Even on distillation vessel, a safety valve or explosion vent should be provided to take care of any accidental pressure. Flare, condenser, vent gas condenser or incinerator should be provided if required.
Another danger to flammable solvents come from smoking and electric sparks. All electric fitting should be flameproof including lighting. During maintenance, use of ferrous tools should be avoided as it can give rise to sparks. Flame arrester and smoke detector should be provided. Fire extinguishers should be kept ready.
As far as possible flammable substances should be processed at low temperature (below flash point) and pressure. Dip feed pipe, slow and controlled addition (e.g. niddle valve), inert blanketing, vacuum, spark/flame avoidance; spark/flame detectors with alarm, no-smoking habit, good ventilation and training to workers are necessary.
Toxic Reactions
For handling acid, alkali and other toxic chemicals, workers must be provided with suitable protective appliances such as rubber or PVC hand gloves, gum-boots, safety goggles, apron etc. Suitable posters showing dangerous properties of these chemicals and safe working procedure should be prominently displayed. Arrangement for combating spills of these chemicals such as water shower or pipe for covering up should be available nearby. The workers should be trained in the use of these chemicals and safety equipment before giving responsible job independently. Suitable scrubbers, absorbers or neutralizers for inorganic gas or vapour and condenser for organic vapour should be provided and well maintained.
Scrubber line should be always open. If it is provided with a valve, the reactor should have safety Valve to take care of any pressure built-up due to closer of the scrubber line valve or any choking in that line. Interlocking of a scrubber line valve with the addition valve is necessary so that no addition of any hazardous chemical can be started in the reactor unless the scrubber line valve is open. Concentration of scrubbing media should be checked and always maintained. f scrubber stops, alarm should be available and the process should also be stopped. Leak detector with alarm, ventilation according to the vapour density of the material, open working space, local exhaust Ventilation on toxic (e.g. pesticide) fumes and dusts, wind velocity and speed indicators, safety showers and eye washers, cautionary notices and medical examinations of workers are necessary.
The modern instrumentation and control devices, interlocks, trips and alarms, auto controllers, automatic process correction device, computer controls, DCS system, direct reading, display and correction system etc. should be provided as per process requirement.
For handling poisonous gases such as chlorine, ammonia, sulphur dioxide, phosgene, phosphine etc, Workers must be trained before assigning them responsible jobs. They should be provided with suitable respiratory protection. Arrangement for good ventilation such as suction hood with scrubbing arrangement should be provided in the plant.
A chemical can enter our body through injection, inhalation or skin contact. Lead, mercury, aromatic solvents, nitro and amino aromatic compounds, benzene, toluene, chlorine, chromium etc. are a few examples which can find entry into human body through various routes. The workers must be suitably protected from exposure to such chemicals. Efficient exhaust system, scrubbers and suitable protective appliances to avoid body contact should be provided. Skin absorption is the most important route and least understood by the average worker. Worker education plays an important role in the proper use of PPE. Workers should be trained to wear proper PPE. After handling of dangerous chemicals, workers must change their clothing followed by bath with soap and water. Provision of safety shower within easy reach is essential.
Periodic medical examination of workers exposed hazardous chemical should be carried out. If workers shows any indication of poisoning due to chemical, suitable preventive measures should be taken.
