Explosion-proof digital grounding device type SHGV-NT-UZG made of stainless steel is intended for grounding and static charge removal from the surface of tank cars and road tankers, fuel reservoirs during loading and unloading of flammable liquids, explosive gases, as well as bulk material that form combustible dust.
Intellectual condition control system:
- resistance circuit condition control;
- grounding indication;
- control of pump operation or other electrical handling machine.
If the clamp is removed during loading and unloading, or the grounding is lost (accidental break or high resistance due to undetected oxidation), feeding pump or other electric handling machine will be de-energized.
For direct insertion of cables or wires into Ex d enclosure of the grounding device, the following specially developed Ex d cable glands for direct insertion are applied: KNV, KOV, KNVTN, KNVTV, KNVM, and with encapsulation KNVZ series.
Scope of application - indoor and outdoor hazardous areas in accordance with explosion protection marking - category II for gas subgroups IIA, IIB, IIB+H2, IIC (without acetylene), zones 1, 2, category III for dust IIIA, IIIB, IIIC, zones 21, 22, category I for firedamp and dust РВ, РП, zones 1, 2, areas non-hazardous with dust and gas.
Marking:
1Ex db [ia Ga] IIC T6 Gb X 1Ex db [ia Ga] IIB+H2 T6 Gb Ех tb [ia Da] IIIC T85°С Db PB Ex db [ia Мa] I Mb Х 
| SHGV-NT-UZG | - | X | - | X | / | X | – TU 27.12.31-046-72453807-2017 |
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| Length of grounding cable, m: 10, 20, 30 (other upon approval) | |||||||
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Example: SHGV-NT-UZG-20-2KNV2NK/PROM - TU 27.12.31-046-72453807-2017
CONNECTION AND OPERATION:
Grounding control during loading and unloading of explosive products and prevention of ignition due to electrostatic charge.
Careful examination of production and technological processes reveals many sources of electrostatic charge which cannot be easily detected and which could be missed, and as a result they become a source of ignition in hazardous areas.
There are a lot of cases of explosions and fires caused by static electricity during loading and unloading of flammable and explosive liquid and loose products.
Contact potential difference occurs when two bodies come into contact, especially in case of friction. The value of CPD depends on a number of factors, such as dielectric properties of the materials, value of their mutual pressure during contact, moisture and surface temperature of these bodies, climatic conditions. When these bodies are separated, each of them keeps its charge, and as the distance between them increases, (and electric capacity of the system decreases), contact potential difference increases because of the work on the separation of charges and it could reach tens and hundreds of kV. If field force reaches breakdown as a result of physical contact or a level of charge, then a discharge occurs. Discharge energy can reach a value which exceeds minimum ignition energy of all groups of potentially explosive gas atmospheres.
| Object | Energy storage at 10 kW | Energy storage at 30 kW | Minimum ignition energy | ||
| propanol | methane | hexane | |||
| Road tanker | 250 mJ | 2,250 mJ | 0,24 mJ | 0,65 mJ | 0,28 mJ |
Static discharge in a hazardous area must be prevented by any means because of a potential risk of an ignition or an explosion. The most important protection is a safe leak of a static charge by means of electrical bonding or grounding. It is not allowed to use the materials with low conductivity in a hazardous area.
Electrostatic charge could form during transportation, loading and unloading of chemical and oil-and-gas products. Any transportation and moving of raw materials involve friction which is the main cause of the electrostatic charge especially in case of transportation of big loads of cargo, e.g. loading and unloading of big tankers. Stationary reservoirs do not pose a problem due to safe leak of charge through grounding connection. Constant grounding connection is impossible in case of mobile reservoirs, e.g. tank cars and road tankers. Hence, safe grounding during loading and unloading must be provided by means of special devices.
