The IBC types
The proliferation of IBC types can complicate the application of best practice static control procedures. Lower cost materials like plastic IBCs are being developed in response to the cost of purchasing IBCs made from stainless steel. It is of paramount importance to consult experts and relevant static control guidance documents when selecting IBCs that are potentially non-conductive.
The Solvent Industry Association guidance notice No.51a provides clear instructions on the types of IBC to be used depending on the solvent flash point and its tendency to conduct or insulate charges (oxygenated or hydrocarbons). Depending on these parameters, either stainless steel IBCs or composites with “anti-static sheaths” are recommended.
Earthing of IBC (Tote) with static control monitoring system
In any event, whatever type of IBC is used, it is of paramount importance to ensure any conductive parts that make up the IBC system including the filling pipe, funnels, nozzles and dispensing cans are all bonded and connected to a dedicated static dissipative earth with a continuous resistance of less than 10 ohms. It is also prudent to ensure composite IBCs handling flammable materials are at least classified as static dissipative.
Methods for demonstrating compliance
There are several ways of ensuring an IBC has a low resistance static earth connection. The easiest way is to provide flexible quick releasing static earthing clamps that are designed to make positive low resistance electrical contact with the IBC. The static earthing clamp should have a conductive connection to a dedicated static earthing point. It should contain a positive clamping mechanism capable of achieving low resistance connection to the IBC and be capable of maintaining positive contact in response to vibration effects when the IBC is being filled. Wherever possible IBC users should specify clamps approved for use within hazardous areas. This will provide additional security and guarantees the clamp will do what is designed to do – dissipate static effectively and safely.
ATEX certification guarantees clamps are not made from material or components that could act as mechanical sources of sparking. Factory Mutual (FM) approved clamp tests ensure clamps are conductive to less than 1 ohm, are capable of maintaining positive electrical contact in response to pulling forces and cannot be disconnected due to equipment vibration. Clamps with combined FM and ATEX certifications provide the most comprehensive and convenient safeguards against electrostatic ignitions.
Instead of maintenance engineers regularly monitoring and maintaining static dissipative earthing circuits and connections, it may be more convenient to adopt the use of self-testing static earthing clamps to offset the time required to monitor the condition of circuits (and the risk of it not being done at all). Each time the self-testing clamp is connected by the operator to an IBC a bright green Light Emitting Diode flashes informing the operator the IBC has a groud connection of 10 ohms or less. The clamp continuously monitors the circuit between the IBC and the designated factory earth point so should the clamp lose its connection to the IBC the LED will stop flashing, warning the operator of a potential fire hazard.
When a company is running processes that require frequent or repeated filling of IBCs, it may be desirable to add an extra dimension of safety to the options outlined above. If a ground connection, for any reason, is compromised the rapid generation and accumulation of static charges in the IBC can be eliminated by cutting the flow of material into the IBC. If the risk assessment concludes there is a likelihood that connections have the potential to be compromised, or not made should operators forget to clamp the IBC, output control contacts can be specified to safeguard against such events. Earthing systems with output control contacts prevent the flow of charged material into the IBC when the system detects a lost connection.
The above measures pertain to IBCs that are metallic and are highly conductive. In processes that require static dissipative composite IBCs, users need to specify earthing systems that can monitor to the recommended static dissipative levels. IBC vendors must be capable of informing customers whether or not the IBC is classified as conductive or static dissipative and what the maximum volume resistivity of the IBC material is.
The main points to consider with each of these options is they enable companies to demonstrate compliance with recommended industry best practice and provide options to customers with different approaches to fire risk management of IBCs.
Checklist for effective static control in hazardous areas:
Identify hazardous areas and processes where static electricity may accumulate.
Specify conductive or static dissipative items of plant, equipment and packaging. Only use insulating plastics after carrying out thorough risk assessment/hazard evaluation.
Ensure correct Earthing & Bonding and other prevention techniques are in place, and are properly maintained.
Provide on-going training and awareness for employees and contractors in safe working practices in hazardous areas.
Mike O’Brien, Managing Director for Newson Gale
If you have any questions relating to the topics discussed in this article,
please contact Newson Gale.