The process of filling fuel into tanks is potentially dangerous, since there is a risk of sparking that can cause a fire or explosion. Sparks are formed as a result of static electricity. The latter is a physical phenomenon that arises due to the friction of dissimilar substances that differ in atomic and molecular structure.
Grounding tank trucks can prevent such a dangerous situation, for which special grounding devices (UZA) are used. The use of grounding equipment in the field of refueling and operation of tanks is regulated by regulatory documents - the need for grounding is stated in paragraph 71 of NPB 111-98.
Types of equipment and principle of operation
The rules for the use of grounding conductors are specified in the fire safety requirements directly in paragraph 71 of NPB 111-98 . There are several types of such equipment, which differ in the type of power supply to the tank itself:
- 220 V;
- 12 V;
- rechargeable stationary batteries.
You can determine what type of grounding devices they are by special markings . The most popular types of conductors are:
- UZA 3V;
- UZA 220V;
- UZA-2MK 06;
- UZA 4K.
The operating principle of grounding is simple: you need to connect the grounding conductor clamp to the tanker and the UZA. Having secured the clamps, proceed to measuring resistance .
This is done not only at the conductor, but also between the contacts. You can find out that the operation is being carried out correctly by the green light coming on, indicating that the total resistance is no more than 100 Ohms.
general description
A grounding device for tank trucks is equipment that allows you to avoid sparks when using flammable substances. The main function is to control the resistance to dissipate static currents.
- Design and applications of the main grounding bus
It is worth noting a certain “risk group” - places with low humidity levels. In such rooms, air masses are characterized by excellent conductivity of electricity, which is why currents can easily “flow” through them. In humid environments, the likelihood of sparking due to electrostatic charge is relatively low.
If the humidity level goes beyond eighty-five percent, the chance of problems occurring is almost zero. However, we can talk about such conditions mainly theoretically: they are extremely rare.
To prevent serious accidents caused by sparks, grounding devices are installed at all gas stations. A grounding device is built into the common circuit. However, we should not forget that the UZA is only an element of the overall system, but in no way a replacement for a conventional grounding circuit.
It is possible to highlight the main functions of devices aimed at grounding tank trucks; among them:
- Monitoring the integrity of the conductor providing grounding.
- Monitoring resistance indicators on contact surfaces.
- Notifying employees that the conductor has received damage and has a high level of resistance. In the event of an emergency, workers will be notified through sound and light.
- Automatic shutdown of pumping equipment in the event of a serious accident.
UZA 3V - design and operation features
The grounding device for tank trucks UZA 3V is equipped with a grounding conductor and an indicator equipped with a CR123 lithium battery.
The compound-filled controller board is equipped with a bright red LED placed in a removable cap. The viewing angle of the LED is 180°; it is installed using a pin that is attached to the reverse side.
Additional fastening strength is provided by toothed washers and M8 nuts , by the way, included in the kit. The conductor and the indicator disc contact are connected by a special insulating separated washer, and the resistance must be measured.
Attention! The power element of the grounding device inevitably discharges over time. The service life of the battery depends on the intensity of use of the device, that is, on the number of fuel drains/fills.
The operating time of the LED with continuous flashing is 650 hours. The self-discharge of a lithium battery is extremely insignificant, thanks to which it can operate for 10 years.
UZA 3V is stored at a temperature of -50…+50° C, always in a sealed condition . If the device has been disassembled, it can be stored at +15...+50° C and 80% humidity.
UZA 220V - design and operation features
The grounding device for UZA 220V tank trucks comes in two types, namely: with external power supply and an explosion-protected unit (UZA-220V-BP-VZ) . An externally powered device performs several basic functions:
- tank grounding;
- blocking fuel filling in case of lack of grounding;
- indication.
The equipment has a degree of protection against dust and moisture at the IP66 level, its service life is 15 years.
UZA-220V-BP-VZ consists of three main elements: a conductor, an indicator and a power supply. A distinctive feature of the parts is explosion-proof design : for example, a special steel case with a window for the power supply is provided.
There is also a pair of cable entries for wires with a diameter of 5-10 mm with a cross-section not exceeding 1.5 m2.
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Marking
In accordance with existing regulations, all components of devices in their markings must contain:
- name of the device element;
- production date and serial number;
- explosion protection class;
- manufacturer's trademark;
- a stylized sign indicating explosion safety - “Ex”.
In addition to the indicated points, if the size of the marking plate is small, the accompanying documentation for the device must contain: an image of the sign of circulation on the territory of the countries participating in the Customs Union; number of the certificate of conformity with technical documentation and the name of the organization that issued the certificate and other data required by law.
The use of modern grounding devices for automobile tanks provides a 100% guarantee of protection of hazardous production facilities, including gas stations, from explosions and ignition of volatile fractions of flammable liquids.
UZA-2MK 06 – design and operation features, existing modifications
UZA-2MK 06 is suitable for operation under normal conditions at temperatures of -20...+40° C. Electrical power is provided using autonomous sources equipped with intrinsically safe outputs.
The capacity of the battery used is 3.0 A/h, the permissible voltage should not exceed 6.3 V, and the maximum current should not exceed 0.06 A .
Separately, the characteristics of the intrinsically safe circuit are distinguished, which differ significantly. For example, the voltage reaches 6.7 V, and the permissible current is 0.015 A.
The grounding conductor is 6 meters long. The grounding device for tank trucks UZA-2MK 06, provided that the external power source is regularly recharged, will operate for 6 years at a temperature of +35° C and a relative humidity of 98% .
Equipment
The product is sold together with all necessary elements:
- Grounding device;
- Conductor – length 5 meters;
- Accumulator battery;
- Installation kit.
Installation and operation rules must be followed to ensure the safety of the product.
Other modifications
Several modifications of the UZA-2MK series have been developed: 04, 05, 06. They differ, traditionally, in the type of power supply: for example, model 04 operates from a standard 220 V network, while version 05 requires a 12 V source.
Particularly noteworthy is model 06, which is used exclusively on the road, that is, intended for autonomous field work . The equipment is equipped with a 6.3 V battery, thanks to which the scope of operation is significantly expanded.
The UZA-2MK models stand out among other identical equipment for their durability and endurance. The devices can withstand 5,000 starts in a row, and in general are able to work for about 6 years at temperatures of -40...+40° C.
Electrical power type
The main differentiation of grounding devices is based on the principle of their power supply. Three types of such devices can be distinguished:
- Autonomous power supply. The devices require a built-in battery. These UZA are used primarily for installation in tank trucks or for integration into the grounding system of gas stations. The kit includes a charger.
- 12–24 Volts. A separate category includes those devices that are designed to operate on direct current at a voltage of 12-24 V. Electrical power for such devices is provided by the on-board network of the fuel truck. Such UZA is mounted directly on the tank structure. The power supply unit with rectifier can be located at a gas station.
- 220 volt. Such devices have a very specific operational orientation: they involve integration into the gas station grounding system.
UZA 4K - design and operation features, existing modifications
The grounding device for tank trucks UZA 4K has several modifications, for example, UZA 4 and UZA 4A. The equipment is ideal for ensuring explosion safety when filling automobile tanks with fuel, liquefied gas, and flammable liquids .
The main purpose of the device is to neutralize the effect produced by static electricity , but at the same time, continuous control is carried out over the grounding circuit, the resistance of which should not exceed 90 Ohms.
Note that the type of power supply of the UZA depends on the modification. For example, devices belonging to the 4K series are compatible with 220 V power supply. At the same time, products from the 4A series can be powered by autonomous sources.
Operating temperature also depends on the specific modification . In particular, the 4K series can be used at temperatures of -40...+40° C, while the 4A model operates within temperatures from -50 to +40° C.
Important! The tank is connected to grounding devices using special clamps, thanks to which it is possible to neutralize static electricity.
Equipment and technical characteristics
The complete set of the product also depends on its modification. In particular, 4A is formed from several blocks that perform specific functions:
- Grounding control – the user is notified by an alarm about the presence of grounding.
- Power unit.
- Charger – allows you to charge batteries.
- Owner's kit.
The 4K modification is also equipped with a control unit that detects the presence of grounding and signals its presence, but no other components are provided, with the exception of the owner’s kit.
Technical characteristics, of course, also depend on the type of device. Each model has its own features and advantages.
Modification 4A has a sound and light alarm , which notifies about the level of resistance present in the grounding circuit. The supply voltage is 3.6 V, and the operating temperature at which the product can be successfully operated varies between -40...+40° C.
One of the important indicators that determine operating conditions is the length of the grounding conductor (in this case it reaches 15 meters ). The unit weighs 2.9 kg , which makes it easy to transport and use.
The technical characteristics of the 4K modification differ slightly. Let's start with the fact that there is a light alarm that informs the user about the presence of resistance and its level.
If it is higher or lower than normal, the pump is automatically blocked and manipulations with fuel become impossible . The 4K series is powered from a 220 V network; the devices can be operated at the same temperature conditions as the 4A model.
Portable grounding devices for tank trucks
Portable grounding devices make it possible to remove static electrical charges when filling tank trucks with liquid petroleum products not only at gas stations, but also in the field, which makes them in demand in the Armed Forces, where refueling has to be carried out under special conditions.
Portable samples of such products work on a principle similar to their stationary counterparts: it is necessary to connect a conductor to a ground loop, thereby forming an electrical circuit.
Such devices consist of several structural elements:
- chain control circuits;
- indication circuit;
- connectors for connection.
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Such equipment is simply irreplaceable at gas stations; its use is carried out in accordance with fire safety requirements. There are standards and requirements, based on which, gas station owners are required to operate such equipment.
The choice of one type or another is determined by the type of power supply at a particular station, but the optimal use would be portable devices with built-in batteries.
It is necessary to strictly follow the rules for transporting and storing equipment to avoid loss of functionality
It is important to observe temperature and humidity conditions and conduct constant technical inspection in order to timely identify problems
