The grounding instruction from «Lacover»
Every year powder colouring becomes more accessible, easier and more various.
New technologies and methods are developed. The equipment for painting is improved and becomes more modern, more convenient for the user. But there are problems that all, almost without exception, companies that use powder coating come across.
The Lacover group of companies, including the Lacover Powder Coating Plant in Ukraine, Industrialbud and Element UA, supplying the consumer with imported powder coating and the Smart Line brand, a manufacturer of powder coating equipment, as a specialist in this field and the manufacturer occupying a leading place in the field of powder coloring strives to give recommendations on the question, most often arising when powder coating.
We want this publication to be read by all the employees of the powder coating site: from the top managers, from the chiefs of production to the painters, who work with powder coating every day. So, that the described below could help to settle one of the common issues - grounding.
Grounding is a deliberate electrical connection of any point of a network, electroinstallation or the equipment with a grounding device. Grounding is designed for safety of human life and/or for full elimination of circumstances and strain of the touch, which are dangerous to human life, resulting errors of isolation. Thus grounding provides safety for human life and safe operation of the device / installation.
Considering principles of work of our equipment for powder coating, grounding should correspond to the positioned standards or higher requirements.
Resistance of grounding of our equipment should be less than 1 M Ω. Due to this condition ensures the lifetime of the equipment we provide to our customers, and also plays an important role for the observance of warranty conditions.
Requirements to grounding
A. Grounding of the powder coating chamber:
For grounding a chamber, the wire should be used in adherence to technical characteristics of section to correspond to the design. The wire is connected to the distributive grounding tyre directly bridged to rods of grounding.
The grounding line for the powder coating chamber: a ground wire of 4 mm2 is laid along the conveyor line, starting from a mark of 5 meters to the camera entrance, ending with a mark of 5 meters from the exit of the camera every 2.5 meters.
The camera and other powder coating equipment should not be put into operation in cases if the customer does not provide a ground wire connected to the grounding tyre for the earthing of the camera, necessary section or if the grounding is made not from grounding rods but from another external source.
B. Grounding of the equipment for powder coating and the other equipment:
Grounding with metal of good quality should be between: the cabinet of the main control panel, automatic and manual powder coating equipment, recuperation device, robots, paint supply center, cockpit, cyclone and conveyor.
A separate grounding conductor from the grounding bus to each equipment, device must be grounded, while described above equipment connects to the facility.
In the workshop with automatic devices, the manual equipment for powder coating is grounded by a 4mm2 wire connected to the grounding bus. During connection to the manual chamber, they are grounded by a ground wire with a terminal connected to the ground bus. It is necessary to make sure that the nut is clamped to the back of the appliance and that the connection is correct.
C. Grounding of the painting area:
All equipment and parts located in the painting area within a radius of 5m2 must be grounded separately. All parts must be grounded, as shown in Figure 1 by a 4mm2 weft wire (equipment that does not have welding junctures and mounted with screws).
D. Conductivity of the floor:
Area where the painting process is carried out, must be ensured with conductivity of the floor. As a rule, concrete bases are considered to be conductive. Additionally, it is necessary to check whether the conductivity of the floor / ground is damaged by using an insulating material.
D. maintenance of conductivity of a hanger:
The paint covering the suspension interferes with the conductivity. This is why the suspension should be exposed to furnacing or be replaced. It is an important condition for preventing productivity downgrades of the spray gun and malfunctions. Along with this, suspension in cabins with lost conductivity reduce the level of coating, which affects the reduction of the color quality.
Check of a grounding line
Verification of grounding and its conformity to standards can be made daily by means of the voltmeter. In usual conditions quality of grounding is checked with measurement devices of grounding resistance.
Since this method is inapplicable in any environment, even though the first method is the best, using a measuring instrument and following the instructions it is possible to define quality of grounding more low.
This measurement begins at the end of the power wire leading to the powder coating equipment. If there is a problem, the verification process starts at the end of the splitter or electrical outlet, then the safety box, etc. The electrical socket can function without deviations, and the problem can be in a splitter, located between the machine and an electrical socket. Finally, the grounding of the machine may be absent.
First bring the voltmeter to a high voltage level. Then measure the wire going to the machine. The value between phase and zero should be within 220 V , as shown in Figure 2 (depending on the network station, there may be 110 V). The deviation of the voltage from the set norm negatively affects equipment work.
The stopper is taken out and grounding is connected to the end as is shown in drawing 3. As shown in Figure 3 or Figure 4 - the reading value depends on zero. It shows at which end of the network zero is. In figure 3, the value should be between 0 and 5 V. The difference between zero and ground should be absent or be insignificant (0 - 5).
The stopper on the left is attached to the end of the ground , as shown in Figure 4. Depending on strain of a network value should correspond approximately 220 V. Depending on the connection of a zero the values read in figure 3 and figure 4 can be opposite.
Zeroing is connection of the end of grounding to zero. If the connection is made in this way, it can be read correctly, as shown in Figure 3 and Figure 4, but this action is not grounded.
Grounding / Earthing systems
Initially, ground resistance is measured at the place where grounding is to be carried out. Depending on the received ground resistance value (ρ), the grounding unit is selected. The chosen unit must correspond to the soil structure, the soil must easily transmit excessive electricity to the ground. The most known types of grounding are shown below:
1. Deep grounding rod, Profiled earth electrode. Earthing, which is the maximum vertical installation of grounding rods. The distance between the rods should be at least a double size of the grounding rod.
2. Superficial grounding rod (Horizontal electrodes, conductors with round section and strip conductors). Represents strip grounding in the form of stars, under condition - the distance around the entry point of the load conductor have correct size, according to one conductor or between them a minimum 60 °. Strips should be dug in the earth at depth of 40 sm ,the cross section should be less than 3x20 mm. This kind of grounding is basically preferred on rocky ground.
3. An earthing plate electrode
Since the activity is relatively small, it is best to avoid the use of grounding plate electrodes. This type of grounding is the digging of electrodes into the ground in an upright position. Instead of filled plates dipped in the ground, it is preferable to use network plate electrodes. These electrodes are economical and suitable for both vertical and horizontal use.
Substances used in reducing soil resistance
To reach necessary ground resistance is not always obviously possible. However for maintenance of protection resistance should be reduced below the level positioned by standards. For free transfer of electric current to a ground the soil value resistance must be below the standards, in an ideal grounding system.
The system and a fast stream of ions should correspond to to a given value. Electric current transfer is provided with motion of electrons in a conductor, ions are provided in the ground. A slight movement of ions in the ground delays the transmission of electric current. It shows high ground resistance.Substances that increase conductivity, reduce resistance (for example, Gem powder) are used in this case. These substances are ideal for any kind of soil (for example, rocky, sandy) with low conductivity and high resistance.
Electrochemical corrosion must be taken into consideration when we search for protection against a lightning strokes and select earthing materials. It is necessary to pay attention to coincidence of used material characteristics and bedrock in which it will be installed. Otherwise, it occurs a phenomenon known as "battery"with the interaction of different materials.
This phenomenon implies a flow of electrons with high voltage to a metal with a low voltage. The metal that has lost electrons is depleted with time. For this reason endurance of metal drops. To prevent this voltage should be:
a) in the open air below 0.25 volts;
b) in an enclosed space below 0.50 volts.
Values corresponding in comparison with the Calomel electrode in sea water 25 ° C are shown in the table.
Step-by-step grounding check
- Read the values in the table and read the grounding instructions.
- Determine the grounding equipment.
- Install the distribution ground busbars.
- Connect the wire from the main ground lines to the distributing ground bus.
- Connect the ground wires to each equipment separately.
- Place the grounding contact on the conveyor as shown in figure 5 and 6.
- For equipment that is mounted without welding, throw the contacts as shown in Figure 1.
- Check the grounding line through the meter, as shown in Figure 2.
- The last time to check all the grounding for compliance with standards, as shown in Figures 5 and 6.