Preventive Measures Mitigate Static Electricity
Preventing Charge Generation
- For liquids avoid splash filling and misting operation. Limit initial fill rates and maximum flow rates.
- 3 ft/sec maximum initial loading until outlet of fill pipe is submerged
- 23 ft/sec maximum thereafter
- Control hydrocarbon flow velocities in all the applicable piping segments
- Avoid pumping or flowing hydrocarbons with dispersed water or solids
- Avoid use of free flowing steam to “inert” a potentially flammable vapor space as wet steam has been described as a “horrendous separator of electrostatic charges”
Preventing Charge Accumulation
- Use sufficient time downstream of pumps and filters to allow charges to dissipate
- Ground conductive fluids while filling insulated containers
- Raise conductivity of low conductivity fluids by adding anti-static additives (SDA) to 100 pS/m
- Use bonding and grounding to prevent build up of potential differences between conductive parts.
Prevent Incendive Spark Discharges
- Allow charge settling time
- Wait at least 2 minutes before gauging or sampling a newly loaded tank compartment through the dome or hatch
Eliminate (or bond) spark promoters in tanks and vessels:Spark promoters can include floating metallic debris in tank compartment, ungrounded tank gauging rods, chains, etc
Bonding and Grounding (SCE group IC005)
If the voltage between two points is zero, no static discharge can take place. Bonding and Grounding eliminates the potential (voltage) between two points thus preventing hazardous potentials from developing on conductors
The earth may be used as a part of bonding system so that all the objects are at zero electrical potential.
Bonding is the process of connecting two or more conductive objects together by means of a conductor so that they are at the same potential as each other but not necessarily at the same potential as the earth.
Grounding is a specific form of bonding in which one or more bonded, conductive objects is also connected to ground so that each is at the same potential as the earth. Hence, all grounded objects are at the same potential and static discharges cannot occur between them.