Increasingly vessels are equipped with Vapour Emission Control Systems. Where provided, it is to be used and operated in accordance with current regulations and instructions contained in the vessel’s VEC System Operation Manual and in conjunction with the requirements and provisions of the shore installation.
Masters and Officers must be aware that significant operational and safety implications are present, as the shore and the ship are effectively joined together as one unit.
The primary hazards include:
- The ship loses effective control of the tank atmosphere pressure, and is directly influenced by any changes which may occur within the terminals system. It is therefore most important that associated pressure sensing devices on the vessel are well maintained. It is also essential that individual cargo tank P.V. valves are properly maintained and operate correctly.
- Vessels fitted with a VEC system must have an independent overfill alarm providing audible and visual warning. These are to be tested at the tank to ensure their proper operation prior to commencing loading, unless the system is provided with an electronic self-testing capability.
Fixed gauging systems must be maintained in a fully operational condition at all times.
- Tanks must not be opened to the atmosphere for gauging or sampling when connected to the shore vapour collecting system, unless loading to the tank is stopped, the tank is isolated from any other tank being loaded, and precautions are taken to reduce any pressure within the cargo tank vapour space.
- The ship’s system is to be provided with means to collect and drain condensed vapour, which may have accumulated in the pipelines. Drains must be installed at low points within the ship’s piping system. These drains must be checked clear before each use of the VEC system and on a regular basis when the system is not in use.
- Care must be taken to ensure that no possibility of misconnection of Vapour and Liquid hoses can occur. The ship’s vapour connection is to be clearly identified. The outboard 1.0 metre of piping is to be painted with yellow and red bands (0.1m red, 0.8m yellow, 0.1m red) and marked with the word “Vapour” (not less than 50mm high). The vessel’s presentation flange is to be fitted with a stud to prevent an incorrect connection.
- To prevent electrostatic build up within the vapour return pipe work, all pipe work is electrically bonded to the hull. The integrity of these connections is to be periodically checked.
Points to pounder :
Ship’s personnel are to make themselves fully aware of the operation of the VEC system on board.
Reference to the approved operations manual is to be made. The oil transfer procedure, required by section 4.7.2 of this manual must contain a description of the VEC system as listed in 33 CFR 155.750 (d).
The full procedures for the use of the VEC system are to be clearly agreed at the pre-transfer meeting between the Terminal Representative and the Chief Officer.
All tests and inspections required by 33 CFR 156.170(g) must be carried out prior to transfer operations.
The VEC system must be inspected and approved/certified by the USCG prior to use in the USA.
The TVEL/LOC will reflect this approval, being endorsed accordingly.
You may also know about STS using VEC :
Before carrying out such an operation reference is to be made to the operational guidelines contained within ISGOTT and other applicable reference publications. The technique is probably described as Vapour Balancing.
Ships carrying out this operation are to be inerted.
Before commencing transfer the following operational precautions must be complied with as a minimum.
- At least one of the vessels must be able to permanently monitor the oxygen content of the vapour stream. The sample point must be close to the manifold and audible and visual alarms are to be available should the oxygen content exceed 7% by volume.
- The oxygen content of all tanks in the common system is to be maintained at a level no higher than 7% by volume.
- The vapour transfer hose is to be purged of air using inert gas or nitrogen until the oxygen content is below 7% before transfer commences.
- Vapour manifold valves are not to be opened until the receiving vessel system pressure exceeds that of the discharging vessel system pressure.
During the Cargo Transfer:
- Operations are to be terminated if the oxygen content of the vapour stream exceeds 7% by volume. Operations are not to be resumed until the oxygen content in the receiving ship has been reduced below 7% by volume.
- There is to be frequent monitoring of both ship’s IG pressures with cross comparison on a regular basis and at least hourly. Transfer volumes are to be compared on the same basis.
- No air is permitted to enter the tanks of the discharging ship at any time.