Raghuvaran Chakkaravarthy
Environmental, Health And Safety
Mahr
Head - Human Resources
Kesava Pillai
Occupational Safety & Health
Abhaygirish
Hr Executive
Vinoddigwal
Industry

Could someone please guide me on electrical earthing & Equipment body earthing (Reactors, Receivers) checking procedure & frequency of checking for chemical plant where solvents (Hexane , Toluene etc ) are handled.
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Sorry to say I am in construction field only I don't have experience/ idea about above mentioned question (chemical industries). But i will discuss with my seniors i will post. Please give a time. Have a safe day. . .
As per the IER-1956 every equipment must have double earthing. If there are chemical storage in huge quantity, the vessel would also need to to be earthed properly. You may refer the IS-3034 for the earthing procedure for different type of equipments/ machines.
About periodicity of testing The IER-1956 is describing the testing of earthing need to be conduct in driest season of the year means- May/ June.
I discussed the issue with one of my seniors who is working in USA. He said the following:

In US, the requirements for such areas are discussed in various consensus standards, primarily the NFPA (National Fire Protection Association), the API (American Petroleum Institute) and ANSI (American National Standards Institute). These standards are referenced in the US OSHA (Occupational Safety and Health Administration) regulations for General Industry (29CFR1910)

In Europe, the CE standards apply, and are also a good reference.

Grounding of vessels, processes, electrical systems, power supplies, communications, and control circuits is EXTREMELY important, and should be reviewed by a Registered Electrical Engineer. Not only is there concern about arcs occurring in these environments, and about uncontrolled static discharges, including storm lightning, but the processes themselves build considerable ionization potential due to the large quantities of gaseous and liquid components flowing through the piping systems and vessels, especially chemical reactors, distillation columns, and fractionating towers.

Installed grounding systems and earth ground systems in such facilities must be visually checked to assure continuity, but must also be checked with instruments to determine the ground resistance potentials of the systems and that they will perform as designed.

New construction must be verified through Quality Check processes to assure that systems are installed to specification and design. Modifications and / or repairs must be checked against specifications and drawings to assure elements are correctly re-installed, and composed of correct materials.



Some common ground failures are:

- Failure to electrically bond cable tray, pipe flanges, equipment bases, discharge nozzles.

- Failure to bond vessel, equipment, or process ground to installed ground grid or structural grounds

- Failure to assure adequate ground grid and potential distribution for the magnitude of the process or equipment involved, resulting in ionization potential.

- Failure to isolate control equipment from ionization potential of processes and vessels, or from RF energy.

- Failure to consider ionization potential from induced voltages associated with high voltage equipment, power lines, or generators operating near metallic alloy processes, vessels, and equipment.

In the US, Assurred Equipment Grounding for installed grounding systems (this is different from tool and power cord grounding) must be checked every six months, and documented, as per OSHA regulation.

Hope this helps.
Very interesting topic! It looks quite simple though big one to give all the details here. Let me try to answer in a simple way. There is no meaning in giving you all the theory and calculations in this forum.

EARTHING:

Just like us- human beings electricity also takes the easiest, shortest and lowest resistance path. By earthing we are just providing an easiest path for possible faulty current to go away which will be other wise disastrous.

Rule 61(2), and (3), Rule 33, 36,37,38,------------92 are all on earthing. I do not advise you to check on but mentioned here for just your information.

Fool proof and effective earthing system can eliminate major hazards of shocks and fires. This is a very simple item of wiring practice which is too often neglected. Codes of practice lay down the correct methods of earthing. If use of copper ground electrodes and earth conductors are found to be too expensive for an installation, galvanized iron earth plates, rods or pipes and G.I. earth wires can be substituted to save costs and yet offer effective earthing in most cases. It is advisable to introduce earth leakage circuit breakers in an earthing system for higher safety. Earthing system needs to be periodically checked and tested to make sure that it is 100% active and records should be maintained of periodic tests.

Earthing consists of Equipment earthing and system earthing. For Equipment earthing it is obligatory that the casing is provided with two separate and distinct connections to Earth.

Entire earthing system is designed with regard to the maximum likely faulty current based on the equipment rating. In this connection it is pertinent to observe that when ever any plant extension is made which will result in increased earth fault current, the size of earthing is checked for correctness of size.

A good earthing is not only for the safety of personnel but to provide for the protection of plants and equipment. Earthing will improve the reliability of equipment and reduce the likelihood of damage as a result of lightenng or faulty current. Earthing is also to provide safe path for the dissipation of faulty current, Lightening strikes, Static discharges, EMI, and RFI signals and interference,

If you have Electrical generating/Recaiving/Sub-stations it is necessary to provide proper earthing. Earthing is just making electrical connection to the general mass of earth.

Earthing has the following functions:

1. Provide the earth connection for grounded neutral systems.

2. Providing the discharge path for the lightening arresters.

3. Ensuring that the non current carrying parts such as equipment frames are always safely at ground potential even though insulation fails.

4. Providing the means of discharging/de-energising equipment before releasing it for maintenance.

Following are the equipment which is to be earthed:

1. The neutral point of equipment is earthed to the station grounding grid either directly or through reactor or through grounding transformers.

2. Apparatus, framework and other non-current carrying metal works associated with power system e.g. Generators, transformers, circuit breakers, control panel frames etc. are earthed directly.

3. Metal frame work not associated with the power system e.g. boundary fence, steel structure, sheaths of communication cables etc. are grounded directly. This is required to provide ground path for any induction, leakage, direct lightening flashover etc.,

4. Lightening arrester shall have independent ground free of points, so that high discharge current is passed to earth.

Inspection/tests for effectiveness of earthing:

Four tests are included in this.

1. Test the impedance of earth continuity conductor between Earthing terminal and the farthest end

2. Test of earth loop impedance.

3. Test the effectiveness of earth leakage circuit breakers,

4. Test of earth electrode resistance.

The earthing can be considered effective if the resistance to the earth of the whole system does not exceed from 0.5 Ohms at substations to maximum of 25 Ohms at overhead line supports.

There are different methods and materials used for earthing.

Earth strips used are normally 1 1/2 X 3/16“for 30 KA or 2 X ¼” for 40 KA of earth fault current. Even # 8 copper wires are normally used for earthing of various equipment.

Visual inspection must be done quarterly and resistance test annually. As and when any equipment is taken up for maintenance it is essential that before restarting the earthing is inspected and made good.

You may also advise your S.O. to check whether the area where your solvents ( Hexane , Toluene etc. ) are handled can be classifdied as hazardous area and if so under which Division and Zone and initiate safety measures accordingly.

Regards,

Kesava Pillai
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