Cargo tanks of a chemical tanker are required to be provided with venting systems to prevent both over and under pressurisation of the tank. Two types of venting system are specified by the Code, namely “open” and “controlled”.
- Open tank venting system – An open venting system is for cargoes which are of little or no flammable or toxic hazard.
- Controlled tank-venting system – Controlled venting systems are required to be fitted in all tanks carrying cargoes emitting harmful or flammable vapours. Each tank must be fitted with pressure/vacuum valve to relieve over-pressure or under-pressure.