Where required, VEC is to be used and operated in accordance with IBC Code, local 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.

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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. Check that the VECS alarms are correctly set and tested. (Secondary PV alarms are set 5-10% above PV valves setting as per Oil Major requirements for normal operations). Note;
  
  1) For VECS as per USCG requirements the VECS alarms should be activated at 80% of PV valve setting.
  
  2) Where IG pressure sensors are used to satisfy secondary venting requirements, PV alarm setting for secondary venting of cargo tanks are required by Oil majors to be set at 5-10% higher than the PV valve setting.
  
  Whenever any of these alarms activates during cargo operations, the cargo operations shall be immediately stopped and cause of alarm activation rectified before resuming cargo operations.



• 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 the cargo being handled permits, loading to the tank is stopped, the tank is isolated from any other tank being loaded, and precautions are taken to safely 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.



• VECS manual requirements to complied with respect to loading rate, vapour density, pressure drop etc.

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 transfer procedure, required by section 4.6.9 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. Checklist TNK 04 is to assist the responsible officer with VEC operations. This checklist is to be completed prior to commencement of any VEC operation.

NOTE: 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.


Related Info:

Ship to ship transfer guideline using VEC systems

Pre-cleaning /washing of cargo tanks

Practical tank cleaning methods for various noxious liquid cargo

Controlled discharge of tank washings of various chemical cargoes

Fixed and portable tank cleaning equipments

Handling various grade liquid chemicals during loading

How to prepare a cargo loading or discharge program ?

How to avoid solidification in cargo tanks ?

Cargo line clearance requirement for chemical tankers

Cargo segregation requirement for chemical tankers

Closed loading requirement of various grade liquid chemicals and related considerations

How to arrange disposal of tank cleaning waste ?

Restrictions on discharge cargo residue into sea

Retention of slops on chemical tankers

Handling self reactive chemicals

Handling of toxic chemical cargoes



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