The steel valve lobe valves in the usual design are designed to be installed on the discharge side of axial fans in order to prevent cold air and precipitation from entering the production premises after the fans are turned off. The design of the lobe valve is a housing in the bearings of which the blades are fixed on the axes. The purpose of the bearings is to ensure the free opening of the valve in conditions of negative external temperatures during periodic operation of the fans. When the fan is turned on, the blades are supported in the open position by the action of the airflow. After the fan is turned off, the blades return to their original position and overlap the valve section. In order to reduce the width of the valve, instead of switching from a circular fan section to a rectangular valve section, a transitional diaphragm is provided. The minimum dynamic pressure at which the lobe valve operates is 30…40 Pa.

Valves (dampers) air insulated designed for installation in low-pressure supply (exhaust) ventilation systems to prevent the penetration of outside air into the supply chambers and rooms when the fan is not working and to regulate the amount of air entering the system. The dampers can be either electrically heated or without it. The electric heaters in the valves serve only to warm up the flaps in case of icing, in order to prevent damage to the frozen flaps when opening. The electric heaters of the valves are switched on for 5–7 minutes before opening the valve. Valves (dampers) air insulated consist of a housing, double-walled rotary blades with thermal insulation properties, a drive and a motion transmission system from the drive to the blades. A rubber seal is installed at the interface points of the blades of the sound. An actuator is installed as a drive. It is possible to manufacture a manual-driven system. The maximum allowable pressure drop in the closed position is 1225 Pa (125 kgs/m^>2). Air passage in the closed position at a pressure drop of no more than 5%.

Resistance coefficient in the open position, not more than 0.2.

Dampers are available in the following types:

• Air unified;

• Round section with electric drive;

• Rectangular cross-section with electric drive;

• Circular cross section with manual drive;

• Rectangular cross-section with manual drive;

Air dampers are designed to regulate the amount of air and are used in air ventilation systems, air heating and other sanitary systems with an operating pressure of up to 1000 Pa.

1. For what purpose are air distribution devices used?

2. Name the main characteristics of air distribution devices.

3. What factors are taken into account when choosing the type of air distribution device in the room?

4. What is the value of the dynamic pressure required for the operation of the lobe check valve?

5. What is the purpose of electric heating of air dampers, in which cases it is used?

Installation of ventilation systems is carried out by a team. As a rule, the integrated team of ventilation fitters includes two or three people with related specialties of an electric welder and a gas cutter. The numerical composition of the team is usually six to seven people. Each team is provided with a set of tools, which allows the team or its units to independently perform almost the entire scope of work on the installation of ventilation systems.

Table 6.1.

Table 6.2

Recommended set of electric welding equipment and tools for a team of locksmiths – ventilators