You must keep in mind that whenever a piece of your equipment touches any other equipment or structure that is electrically conductive and grounded, then the potential for sparking from a static electrical discharge exists. The discharge or sparking of the accumulated charge is the primary manifestation of static electricity. Ground your equipment and yourself, before opening the gauge hatch. You will have little control, or knowledge, of the vapor / air mix inside the tanks you are working. ALWAYS assume that a commodity is flammable and that a tank atmosphere is between its' upper and lower explosive limits. ALWAYS assume that a commodity is flammable and that a tank atmosphere is between its' upper and lower explosive limits.
Do not lower equipment into tanks where abnormal sounds such as dripping water or steam leaks are suspected. These types of situations, especially steam, can create a heavily ionized atmosphere which will increase the risk of electrostatic build up immensely. Report this type of condition to a responsible vessel or terminal representative. Using a tank's handrail or casually touching tank fixtures aids in bleeding a static body charge. Any electrical or electronic device must be grounded prior to and at all times during its entry into a tank. The ground connection must be firmly attached to an integral part of the tank structure, preferably away from the gauge hatch. Product handling, pumping, mixing, blending, etc., is a major producer of electrostatic generation. It is therefore very important that a period of relaxation be allowed after a product activity, prior to gauging, sampling etc., to allow for charge dissipation. Active tanks should not be gauged or sampled, unless the vapor space is known to be inert.
Some materials, however, have been found to be more susceptible to static generation than others; for example: Ropes and cords used with sampling devices and thermometers must be of 100% natural fiber such as cotton. SYNTHETIC FIBER CORD OR ROPE MUST NOT BE USED. Hazardous electrostatic charges can accumulate only on bodies that are relatively well insulated from each other; and the ground. Otherwise, charges leak away and recombine with their counterparts as fast as they are formed. There are many things that YOU can do to prevent the buildup of an electrostatic charge. Only use gauging tapes that are approved for use in the petroleum industry. Tapes designed for use in other industries may have a protective coating, such as teflon, which acts as an insulator, thereby preventing the dissipation of the charge. Always keep the gauging tape or sampling cord in continuous contact with the rim of the gauge hatch unless some part of it is immersed in the liquid.
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