Explosion-proof equipment plant
Explosion-proof electronic grounding device SHGVA-UZG ensures grounding during loading and unloading of flammable liquids and explosive gases. Its operation is based on the control of the resistance circuit which guarantees grounding and control of the operation of a pump or other electric loading-unloading device.
Explosion-proof grounding device type SHGVA-UZG is intended for grounding and static charge removal from the surface of tank cars and railroad tankers, fuel reservoirs, ship fuel storage tanks. Intrinsic safety barrier [ia] is used in the grounding device SHGVA-UZG for protection during connection. If the clamps are removed during loading and unloading or if the grounding is lost (accidental fault or high voltage caused by latent oxidation), feeding pump or other electric loading and unloading device will be de-energized.SHGVA-UZG grounding device is assembled on the base of SHORV171712-О09 enclosure made of aluminum-silicon alloy; clamps are made of stainless steel (galvanized steel upon request), contact pads on clamps are made of copper.
For direct insertion of cables and wires into Exd enclosure of the grounding device, the following specially developed Exd glands for direct insertion with sealing are applied KNV, KOV, KNVTN, KNVTV, KNVM and with encapsulation KNVZ series. According to the mandatory requirements, this characteristic is specified in the certificate. This helps to refuse from inlet junction box (except for mining version РВ), which makes the products of "ZAVOD GORELTEX" Co. Ltd. unique compared with products of other companies.
Full production cycle starting from casting molds and to ready product is performed at the explosion-proof equipment plant “ZAVOD GORELTEX” Co. Ltd. on the territory of the Russian Federation.
Scope of application - hazardous indoor and outdoor areas in accordance with explosion protection marking, GOST 30852.13-2002 (IEC 60079-14:1996) and areas hazardous with combustible dust ignition, as per GOST IEC 61241-3-2011, dangerous production facilities of I, II, III, IV hazard classes under supervision of Rostekhnadzor and national supervisory bodies of the CU and the CIS countries.
COMPLETENESS
Internal electronic system with a grounding state indication unit, clamps, brackets for mounting, cable of length 10 m - 30 m or other length upon approval.
Marking:
1Ex db [ia Ga] IIС T6 Gb Ex tb [ia Da] IIIС T85°С Db
TU 27.12.31-046-72453807-2017
Number and dimension type of cable glands are determined in accordance with customers request.
FORMATION OF ORDER| SHGVA-UZG | - | X | - | X | – TU 3400-005-72453807-07 |
| Product name | |||||
| Grounding cable length, m: 10, 20, 30 (other upon approval) | |||||
| Number and dimension type of cable glands |
Example: SHGVA-UZG-20-2KOV2-TU 3400-005-72453807-07
CONNECTION AND OPERATION:
Clamps are connected to the metal part of the road tanker’s body. After pressing of “MEASURING” button, static electricity flows from the road tanker to the earth main line (PE). The second wire measures resistance of ground circuit resistance, transition resistance between clamps’ contacts, and resistance of wires of grounding conductor. If summarized measured resistance does not exceed (60±20) Ohm, “GROUNDED” indicating sign lights up allowing road tanker unloading-loading operations.
The following sequence of actions shall be followed in order to measure transition resistance:1. Connect clamps of grounding conductor to the non-painted metal part of the road tanker.
2. Get “MAINS” switch to “ON” position. Observe lighting up of “NOT GROUNDED” (red indicating sign).
3. Press and hold “MEASURING” button for 2 seconds.
4. If summarized transition resistance is within (60±20) Ohm, light indication “NOT GROUNDED” shall go out (red indicating sign) and “GROUNDED” light indication lights up (orange indicating sign). Road tanker unloading-loading operation will start within 5 seconds after lighting up of “GROUNDED” light indication and “PUMP IS ON” indicating sign will light up (green indicating sign).
5. If light indication does not change after 2 seconds, “MAINS” switch shall be switched to “OFF” position, connection of measuring clamps shall be checked and actions in clauses 2-4 shall be repeated.
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 |
0,65 mJ |
0,28 mJ |
0,24 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.
