What are sources of Static Electricity on ships?

Following are the sources of static electricity on ships:

1. Loading and unloading

An electrostatic charge is generated within the liquid as it flows through pipelines. The amount of charge generated will depend on the ability of the liquid to conduct electricity, a property known as its electrical conductivity. liquid flowing into a cargo tank can be charged by friction within the loading pipeline and remain charged within the cargo tank. The static charge within the cargo will slowly d issipate as the difference in potential between the cargo and the tank structure equalises. This process is called charge relaxation and its speed depends upon the conductivity of the liquid. Should the cargo contain water droplets, friction occurs when these droplets settle by gravity through the liquid in the tank (assuming that the liquid has a density less than that of water). Similarly, if the liquid contains a non-dissolved gas, the liquid could become charged when the gas bubbles rise to the surface of the liquid in the tank