March 3, 2011

Learn Lessons from Incidents

The Directorate General, Factory Advice Services and Labour Insitutes (DGFASLI) has published a number of incidents on their website. I have separated the process incidents and given them below. Learn lessons from them.

Incident 1:"In a chemical factory yellow phosphorous was converted into red phosphorous in a rotary furnace. When the yellow phosphorous was cooked in the rotary furnace for its conversion to red phosphorous at 244oc, water which was surrounding the yellow phosphorous, became steam. When steam was vented, it carried away certain amount of phosphorous and this caused the vent line choke. This ultimately increased the temperature and pressure of the vessel. Temperature shot up to 300oC and pressure was not being monitored. Suddenly the furnace exploded and the stored up hot gases caused flash fire injury on the worker and subsequently he died.
Causes :

  • The outlet for the generated steam and system pressure was chocked by the phosphorous and there was a pressure and there was a pressure temperature built up in the vessel
  • Pressure was not monitored by the pressure gauge installed in the furnace
  • No safety valve with the proper scrubber arrangement was not installed in the furnace".
Incident 2: "On 18-07-2004 at 06.02 P,M, the Captive Power Plant feeding electrical supply to Cell House - II got tripped due to a flashover (earth fault). This resulted in the tripping of load in Cell House - II and a few motor drives in other sections. But the Cell House-I continued to function, producing Chlorine as it was being operated on EB Power. There was a Chlorine Scrubber system which was a packed column and whose function was to absorb the chlorine gas by means of the circulating lime slurry, in the event of any operational upsets in the process and chlorine free air was vented to the atmosphere. There is a chlorine gas compressor in the chlorine liquefaction section, the compressor sucks the chlorine which is evolved in the cell during electrolysis and compresses it for chlorine liquefaction. Since both the Chlorine scrubber blower and the Chlorine Compressor also got tripped along with the Cell House - II, the Chlorine gas which evolved from the Cells of Cell House – II came out freely and drifted along with the wind toward the adjoining villages. No casualty. Causes:
  • Emergency power supply was not provided to the Chlorine absorption system to meet out any problem of power interruption during emergency of chlorine leak
  • Cell House – I and Cell house - II were not provided with interlock arrangements in such a manner that if one cell house trips due to operational problem, the other cell house also gets tripped instantaneously".

Incident 3: "In a factory, where 10 MT weak sulphuric acid was stored, suddenly the suction line valve tank nozzle assembly got broken and through this opening sulphuric acid drained out from the tank and this resulted in vacuum formation in the tank. This FRP tank hit against the supporting channel legs due to the formation of vacuum. Causes:
  • The FRP tank was not maintained with a adequate strength and stability
  • The FRP tank was not tested and certified by the Competent person every year"

Incident 4:"In a fertilizer factory, as the granulator discharge chute got chocked the plant was stopped and the workers cleaned the choked discharge chute by means of poking. After cleaning, the plant was, started without feeding the raw materials namely phosphoric acid, sulphuric acid and ammonia; the granulator was put on dry run. Meanwhile, the heavy lump which caused the block in exhaust ducting fell down and consequently the unreacted ammonia, came out from the discharge end in the form of heavy puffing and injured 5 contract workers. They were given medical treatment in Government hospital and were discharged later. Cause: Un-reacted ammonia in the granulator came out from the discharge end in the form of heavy puffing and injured the workers"

Incident 5:"In a pharmaceuticals manufacturing industry, after the bulk drug is produced the solvents are recovered by distillation in solvent recovery plant. In this instance, a flash distillation still, T-302 was used for the recovery of solvent, Dimethly Sulfoxide (DMSO) in the Solvent Recovery Plant. A batch quantity of 5 KI. of 75% concentration DMSO was charged into the still T-302 in which 700 mm. of Hg vacuum using a piston vacuum pump and a temperature of 136~ were maintained. When this batch was going on and 2.5 KI. of DMSO was inside T-302, there was a hissing sound and immediately after the hissing sound was heard by the worker the still T-302 exploded with a fire ball, killing a chemist and another chemical engineer. The control room which was located very close to the Solvent Recovery Plant was heavily damaged in the explosion. There were so many joints, flanges and gaskets in the pipe line along the DMSO vapour route on the vacuum pump side. Hence failure of such parts might have led to leakage of air in the circuit and could have caused air DMSO explosive mixture. Causes:
  • DMSO is a flammable liquid. It has a flash point of 80°C and flammable range from 2.6% (volume) LFL to 63% (volume) UFL. Hence when the still, T-302 is at 136°C, vacuum is absolutely necessary to rule out air entry and to prevent fire. Before the explosion, a hissing sound was heard by a witness; this indicates that vacuum still T-302 could have failed due to development of hole (s) through which air entered and formed an explosion.
  • As air ingressed the still T-302, static charges could have been generated due to mixing with the DMSO. The static charges generated could have ignited the explosive mixture, leading to explosion and fire ball"

Incident 6: "In a fine chemicals manufacturing industry, chemicals like 2 – amino Di-bromo-benzly alcohol, manganese dioxide and toluene were loaded into the 4 KL stainless steel reactor (SSR5) and heated upto 65-70 degree centigrade and agitated in the above process. The resultant product layer was settled and filtered in SS nutsche filter by transferring through a HDPE hose. The remaining layer containing toluene was unloaded in a 200 litre HDPE barrel which was not provided with proper earthing or bonding to dissipate the static electric charges and hence fire broke out and spread to the nearby nutsche filter and SSR 6 reactor. Cause: HDPE barrel which was not provided with proper earthing or bonding to dissipate the static electric charges and hence fire broke out".

Incident 7: "A chemical factory had erected three MS cylindrical storage vessels with a capacity of 24 KL - 2 nos. and 30 KL - 1 no. At the time of incident, a tanker lorry with 24 KL petroleum product was brought to the premises for the purpose of unloading into the installed storage tanks. The workers tried to unload the petroleum product into the left extreme vessel of the 3 vessels (30 KL capacity) by using the rubber hose, one end of the rubber hose was connected to the outlet valve of the lorry and the other end of the rubber hose was connected to the 30 KL horizontal tank valve. While transferring the material, there was some leakage at the point of outlet valve connected to the rubber hose. In order to control the leakage, the workers decided to move the lorry to correct position. The driver started the tanker lorry and immediately there was a sudden fire noticed at the outlet valve leakage area. The workers tried to put out the fire but they could not do so. Fire spread out to the other area and consequently the storage vessel got suddenly burst out and thrown out from its foundation. Because of this explosion, the petroleum material became a fire ball, causing minor burn injury to about 23 onlookers and nearby factory workers.Causes :
  • The petroleum product which is very highly flammable in nature was unloaded from the road tanker to the M.S. tanks without providing proper bonding to the road tanker and the storage tank; also earthing to avoid the risk of static electricity was not done.
  • While the petroleum product was leaking through the rubber hose, the driver started the tanker lorry. The small sparks released from the exhaust pipe, ignited the petroleum product vapour, resulting in fire and tank explosion".
The above information has been obtained from this link.

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