Chemical Tankers / Day 1 / Day 1 Topic 6 Static Electricity

6.5 Elimination of static electricity

Loading operations.

To minimize the hazard, flow rates for static accumulator cargoes must be restricted during the initial stages of loading as follows:

The flow velocity through the loading line into each tank is not to exceed 1 meter per second

Note: ISGOTT (latest ed.) contains the formula to calculate max allowable flow rates & precautions to take against accumulation of static charge

6.5 Elimination of static electricity

Loading operations.

Such restricted loading rate should be followed until the cargo has covered the filling inlet and the tank bottom, or depth of 0.5 meters above the tank bottom has been reached, whichever is greater.

6.5 Elimination of static electricity

Loading operations.

Loading rate of 1 meter per second correspond to the following rates:

6.5 Elimination of static electricity

Loading operations.

Thereafter, loading rate may be increased to a maximum pipeline speed of 7 m/s.

Experience indicates that hazardous potentials in respect of static electricity do nor occur if the velocity is below 7 m/s.

6.5 Elimination of static electricity

Loading operations.

Loading of petroleum products into the tanks, which have not been inerted, is not permitted unless the agreement of the Management Office has first been obtained.

6.5 Elimination of static electricity

Loading overall (freefall loading).

If the cargo has been electrically charged by flow through a shore pipeline, loading overall or splash filling will deliver it to the liquid surface in the tank where the hazard from electrostatic charging, in the presence of flammable vapours, is mostly likely to occur.

6.5 Elimination of static electricity

Loading overall (freefall loading).

For these reasons, loading or transferring of flammable cargoes – by

“loading overall” is not permitted – on Company ships.

6.5 Elimination of static electricity

Sampling or manual ullaging.

There should be a delay of 30 minutes (settling time) after the completion of loading and before commencing of ullaging or sampling procedures. This is to allow the settling of gas bubbles, water or particulate matter in the liquid and the dissipation of any electrical Potential.

6.5 Elimination of static electricity

Sampling or manual ullaging.

Therefore, sampling or manual ullaging, including UTI or MMC should not be done unless there has been a settling time of minimum 30 minutes after loading is stopped into the tank.

6.5 Elimination of static electricity

Sampling or manual ullaging.

After the 30 minutes waiting period, metallic equipment (UTI, MMC, sampling devices) may be used for dipping, ullaging and sampling, but it must be effectively bonded and securely earthed to the structure of the ship before it is introduced into the tank, and must remain earthed until after removal.