Chlorine incident

Thanks to Mr Harbhajan Singh Seghal for sending this case study:
CASE STUDY OF CHLORINE LEAKAGE

 INCIDENT :

Chlorine leakage took place from the bottom of 100 Kgs. chlorine cylinder at one of the water chlorination plant situated in a populated area.
ACTION TAKEN :
- The consumer informed the FIRE BRIGADE and the manufacturer.
- Fire brigade reached the site at the earliest and the manufacturer reaches after 1.5 hr. being 100 km away. By the time situation was under control.
- Fire brigade put the leaking cylinder in the underground pit with MANHOLE.
PROBLEM EXPERIENCED IN CONTROLLING CHLORINE LEAKAGE:
- The cylinder started floating on the surface of water in the pit and gas started coming out from the MANHOLE.
- Additional weights were tied with cylinder to keep it dipped.
- Additional water had to be pumped as still some gas was coming out.
- It took about one hour to control the situation in the populated area. No body in the area was affected
OBSERVATIONS:
- The cylinder was 15 years old
- It was tested hydraulically 20 months earlier.
- Pitting & dents were observed at the bottom side near the STAND.
- Pin hole had developed in the pitting area near the welding of the stand.
- There was no safety equipment, neutralizing system with the consumer.
- No proper loading / unloading system of Cl2 cylinder was there.
- No provision of Ammonia torch / ammonia was there to check leakage during connection / disconnection stage. Corrosion was observed in the chlorination system.
POSSIBLE REASONS OF LEAKAGE:
- Some moisture in the cylinder before filling or backflow of moisture after getting the cylinder empty due to inadequate barometric leg or malfunctioning of chlorination system can result pinhole.
- Unloading of the cylinder by dumping on the ground results dent and makes the surface weak and some times develops pin hole.
- Storage of the cylinder at wet and muddy place excel rate corrosion in the cylinder surface.
- Old cylinders were designed as per Ammonia cylinders code which has tolerance of scattered porosity in the plate of the cylinder & welding against NIL porosity in the present standard IS-3196. Minor leakages were observed in such cylinders also at any time. Now, the permission is not given to such cylinders, only latest code is followed.
- Most of the consumers are withdrawing Cl2 at higher rate which results ice formation on the outer surface of the cylinder. Also gas nuisance is observed in the area due to poor connection or bad MOC particulars gaskets. In the presence of moisture & gas nuisance, chlorine cylinders and Cl2 valves are badly affected and results emergency sometime.
- Most of the consumers do not keep Ammonia Torch at site and not checking leakage at the time of connection / disconnection and on regular basis. This overlooking also causes chlorine leakage beyond control.
SUGGESTED ACTIONS :
- Cylinders are to be stored at concrete flooring under a covered shed. These should be loaded / unloaded with the help of hoist / chain block / on the plate-form to avoid any damage.
- Ammonia Torch should be kept nearby. No leakage should be allowed.Two to Three times leakage should be checked in the shift.
- Extra precautions to be taken while filling cylinder in checking moisture, physical examination of cylinder & painting etc. Cylinders with external pitting / dents should be rejected . Consumer should provide barometric leg in their system.
- Consumers need to be educated for safe handling of chlorine from time to time. Consumers should have all safety equipments, chlorine neutralizing system and competent persons.
- In case of leakage cylinder / tonner is not to be put in water. It results higher chlorine release due to poor solubility of chlorine in water and cause serious emergency. It should be handled by vacuum blower & neutralizing system only.
- At the first site leaky part of the cylinder / tonner should be brought on the upper side. This results reduction in Cl2 leakage by 15 times. By increasing the consumption rate of chlorine after above action, lowers the temperature / pressure of the cylinder and results further reduction in leak rate and gives some relief time for emergency action.
CONCLUSION :
- Cl2 leakage can be handled safely by competent persons with the help of safety equipments and chlorine neutralizing system.
- Cl2 handling system need to be audited and persons need training from time to time.
- Standard guide lines are to be followed for safe handling of chlorine.