Much more common is the need for flexible paints in which it is possible to treat the entire product range of a company or to carry out the service of varnishing various products.

• ensure the highest possible quality of varnishing (surface protection);

• ensure the statutory working conditions;

• to provide for the conditions prescribed by law for the protection of personnel and the environment (applicable human and environmental laws);

• ensure safe operation with respect to fire and explosion protection (applicable PP and PEX protection law).

Also, no matter what painting facility it is, technologically they consist of:

• parts (rooms) for the preparation of varnishing – cleaning, puttying and grinding;

• paint application rooms;

• dying rooms.

In practice, the whole process of treating a subject is cyclically repeated. The number of cycles depends on the type of medium and the level of quality required.

The exhaust and supply systems are made up of fans and piping that stream the air that is being injected or ejected from the paint booth.

Picture 1.1.1 shows the parts of the paint shop and the airflow through it. There are filters at the entrance to filter the polluted atmospheric air to prevent dust from entering the paint booth. At the outlet are filters that filter the polluted air generated by the varnishing process to the point where it is no longer harmful to health and the environment and is released as such into the atmosphere. The type and fineness of air filtration filters at the outlet of the paint both depends primarily on the means used in the paintwork process. Also, depending on the painting process, the outlet filtration is carried out in several stages (multiple filtration – from 2 to 4 filtration stages).

The proper operation of the paint booth requires the maintenance of the minimum amount of air required. The criteria for calculating the amount of air required for ventilation to be correct are:

• effective removal of overspray particles from the workspace that do not end on the subject being varnished;

• maintaining dangerous concentrations below 10% of the lower explosive limit of the agent (s) to be handled (25% per ATEX);

• size of paint booth.

For the lacquering process it is necessary to keep the entire lacquer room in a certain overpressure or underpressure (50 – 200 Pa) depending on the type of process (type of lacquers used). If it is dangerous to create vapor around the outside of the paint shop, the paint shop is kept under pressure (a rarer requirement), and if it is necessary to ensure that no dust particles enter the outside area, the paint shop is kept pressurized (a more frequent requirement). The pressure, that is, the overpressure, is achieved by regulating the supply fan. The amount of supply air also depends on the blockage of the filter, this time the inlet.

In addition to maintaining the flow rate and overpressure, maintaining the operating temperature is also important for the process. It should not be below 10 ^oC, so in winter, when temperatures are regularly below the set point, it is necessary to ensure that the inlet air is heated. Temperature control is by acting on control valves which essentially change the power of the heater (a larger or smaller amount of heated medium passes through it).

In addition to these requirements, each paint shop contains certain safety features. Primarily, these include the door and window enclosure control sensors to prevent the spread of polluted air into the surrounding area or the entry of dust particles from the surrounding area. Also, the process of lacquering leads to the formation of highly flammable and explosive concentrations of gases (primarily due to evaporation of solvents in lacquers), therefore it is necessary to pay attention to the regulations and requirements of the system for work in explosive atmospheres (applies to the use of certified devices) and to control the correctness of the same. , and adherence to the default workflow.

In order to distribute the injected air evenly throughout the space on the ceiling of the paint shop, there are filter panels for air distribution. They can be designed in different ways, and the essential requirement is to reduce the inlet air velocity to less than 1 m / s.

Depending on the method of separation of the varnish from the polluted air, the varnishes can be divided into two main groups, namely:

• dry and
• wet

Dry filtration plants use multiple filtration to purify lightly saturated air. In more recent embodiments, a solution is preferred in which air first passes through a cardboard filter where larger particles of lacquer are filtered. This is followed by a finer filtration in which the air passes through the stop lacquer filters, and finally, as the third stage of filtration, the air passes through absolute filters, after which it is completely clean and without any odors, and as such is released into the atmosphere. The varnishes used and the lacquering process, as well as the regulations, determine how many filtering stages will be used and which filters will be used, so in some cases it is possible to skip the third filtering stage (absolute filters).

Mineral wool filters

In the mineral fiber filters shown in Picture 1.2.2, the separation takes place at a much finer level, both because of the inertia effect and the strength of the electrostatic attraction between the particles and the outer surface of the fibers. Larger particles are retained due to a sieve-like effect. Mineral fiber filters are common post-filters for cardboard filters. A feature of these filters (stop lacquer filters) is the ability to absorb lacquers up to 5 kg / m2.

Table 1.2.1. Comparison of filter materials

A requirement for a wet filtration plant is to mix contaminated air with water which takes over the varnish particles and thus filters the air.

Depending on where the air comes in contact with water, there are two types of wet process lacquer filtering, which are:

– water paint booths;

– fountain walls.

In practice, due to the extreme depreciation of filter materials, ease of construction, environmental friendliness and minimal maintenance, dry filtration paints are nowadays prevalent. The use of water filtration booths is recommended for service paints or plants where the need for varnishing is 8 hours or more per day.

The varnishing and / or drying cabin can be a building (masonry) building or a cabin composed of insulating panels and associated structures. It can be located inside or outside the building. When choosing a paint shop location, it is important to agree on all production processes and to select the location of the paint shop / dryer in relation to them, it is important to pay attention to fire protection.

The number of air changes in the paint shop is 100-250 i / h, which is satisfactory for all branches of the industry (more air changes are used for the automotive and wood industry – high gloss, fewer air changes in the metal industry).

Depending on the industry, two types of ventilation are most commonly used in pressure paint and pressure ventilation systems. The pressure ventilation system is used in the branches of the industry without special requirements on the quality of varnishing, and this way it is achieved that the danger zone does not expand beyond the varnish (suction ventilation greater than 5-10% compared to supply ventilation). The overpressure ventilation system is used in industries with high quality requirements for the varnished surface (automotive, timber, etc.). This kind of ventilation system prevents dust from entering the surrounding area (suction ventilation is less than 5-10% compared to supply ventilation).

Exhaust ventilation is installed sideways or underfloor. The choice of side or floor suction depends on the workpieces to which the paint is applied. Thus, in the automotive and metal industries where large pieces are processed, the installation of a floor suction unit is recommended, while in the branches of the industry where smaller pieces are processed, the lateral suction walls are predominantly used. In addition, a combination of floor and / or side suction is possible, and through the same consumers (the distribution of ventilation inside the cabin depending on the size and shape of the work pieces – switching mode is achieved by automatic or manual flaps).

There are two basic ways of filtering suction air from a paint shop: a dry filtration process and a wet filtration process. Dry suction rocks have built-in filters (pre-filter and post-filter) that retain lacquer particles and prevent environmental pollution, while in wet filtration in addition to water, a filter integrated into the rock itself to filter the waste air.

The suction rock (lateral or floor / dry or wet) is connected by a galvanized pipeline to a suction fan, which is mounted inside the cabin or outside to a wall or concrete base. The design of the fans and electric motors can be standard or explosion proof. The choice of fans and motors is influenced by the colors and varnishes used.

If water-based paints and varnishes are used, fan and motor performance may be standard. They should not be used for the screening of paints and varnishes that form potentially explosive mixtures.

For this purpose a blower and an electric motor must be used in explosion-proof version (the choice of explosion-proof protection depends on the class of colors and varnishes used). Exhaust ventilation must be fitted with ventilation control switches and filter fill gauges.

Supply ventilation consists of an air supply unit, a conduit and a flow ceiling in which an inlet air filtration filter is integrated. The choice of the unit for compensation of air depends on the type of heating medium (water, steam, natural gas, LPG, fuel oil), and accordingly the unit itself is selected. The air intake unit consists of a supply fan, a heat exchanger, a pre-filter (pre-filtration of the inlet air) and a control blind (manual or engine). Supply ventilation is equipped with PTC probes to control the desired temperature. The air supply equipment is connected by a galvanized pipeline to the discharge ceiling. A fire damper is provided at the entrance to the cabin, which closes the air supply and switches off the ventilation if the temperature rises above 70 ° C.

Depending on the wishes of the Investor, in addition to the heating system, air humidification and cooling systems are often installed in the paint shops. They achieve the desired microclimatic conditions in the area of ​​the paint shop, which are a prerequisite for achieving a superior product in terms of surface protection, ie the application of paint and varnish.

Electrical installations include complete automatic process control via PLC and frequency converters. Visualization, control and alarming of the process is done via HMI (touch display).

This kind of electrocardis cabinet allows different processes of varnishing and drying depending on the individual wishes of the customer.

There is a possibility to design multiple processes of varnishing or drying. In addition to these processes, the control cabinet can only have a process of reduced ventilation, in which the preparation work is carried out, without the varnishing and drying process. During this process, the complete ventilation equipment is not used but the same because it has at least twice the capacity.

An integral part of the wiring is various digital and analog sensors that enable ventilation control and regulation of the paint shop, or dryer, in order to ensure safe working conditions and optimum operation.

The cabinet of automation and power supply for all consumers according to the conditions of Ex Agency contains:

– full automatic control of the process of varnishing / drying,

– pre-ventilation,

– control of ventilation,

– control of PP protection,

– control of door closure,

– control of filter fill,

– gun lock for varnishing,

– postventilation,

– regulation of varnishing / drying temperature,

– regulation of pressure / pressure,

– moisture control,

The testing of complete wiring with the issuance of the test protocol necessary for Ex Agency findings consists of:

– timing of the drying process.

– Dielectric testing tensile strength,

-Testing of insulation resistance,

-Testing of continuity of protective conductor and equipotential bonding conductor,

-Testing of grounding resistance,

-Testing of fault loop impedance,

-Testing of floor and wall resistance.