Installation, starting and adjustment of ventilation and air conditioning systems A Guide. Alexey Vasilyevich Antipov
m = 7.7 … 7.8. Simultaneously with an increase in m, the coefficient of local resistance also changes significantly. Figure 5.1 shows a diagram of a cylindrical nozzle with preload.
Supply grilles of various designs, ceiling lampshades and diffusers are also widely used, capable of working as supply and exhaust devices.
In rooms of small height (up to 5 m), air distribution can be carried out through perforated panels mounted in the ceiling. In this case, the normative mobility of air in the working area is achieved with a large multiplicity of air exchange. Perforation holes are made with a diameter of 2 to 10 mm, the area of the living section of the panel does not exceed 10% of the total area of the panel.
In air distributors-lamps, air is released (removed) through fluorescent lamps mounted in the suspended ceiling structure. Such a solution in the case of air extraction reduces the heat input from the lighting into the room, since part of this heat is carried away together with the exhaust air, moreover, due to the cooling of the lamps, it increases illumination.
A sufficiently satisfactory air distribution can be achieved by using perforated air ducts. The holes in the duct of variable cross-section length are located in its lower part.
Local exhaust ventilation is used when the places of harmful emissions in the room are localized and it is possible to prevent their spread throughout the room.
5.3. Devices for adjusting ventilation systems
General-purpose check valves are designed to prevent air from flowing through the branches to the disconnected fans (from the disconnected fans) when the latter are connected to the collectors. When installing valves in a vertical duct, the air flow should be directed from the bottom up. Installation of the valve in the network is allowed at air speeds in horizontal sections V ≥ 5…6m/s and on vertical V ≥ 4m/s.
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/m2). 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.
Questions to Chapter 5
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?
Chapter VI. Mounting tools, fixtures and accessories for mechanization of installation work
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
Table 6.3
Tools for gas cutting of steel
Table. 6.4.
Basic data of non-self-propelled inventory means of scaffolding and rigging
The connection of the end of the box with the flange is carried out using a TRUMPF TF 350–2 manual press. The fastening element is a "press rivet", which is cut and molded from the material of the workpiece in one working stroke of the punch (punch). This mechanical process of joining metal sheets is known as "offset connection" – the upper sheet is connected to the lower by kinematic closure. Its main advantage over traditional spot welding is that there is no damage to the surface due to heating, the butt joint is corrosion resistant. The TF 350–2 press is designed both for joining uncoated sheets and galvanized, painted, polymer-coated sheets. Preliminary and final processing with such "cold welding" is not required, there are no costs for screws, rivets and other connecting elements. For ease of operation, the punch, which forms the "rivet" with a continuous pressing blow, is installed in a movable lever. Thus, the tool frame can be "opened" with a single movement of the hand in order to easily and quickly install the tool at the desired point of the tire. At the same time, the flange height is allowed up to 40mm. A special cone puller makes it possible to fasten the tire with the box as close as possible to the edge of the duct. Depending on the technical and aesthetic requirements, the connecting element can be concave into the surface of the box or protrude above the surface. It is possible to obtain an almost airtight connection for sheets of various thicknesses by choosing the appropriate matrix size. A set of tools is installed on the TRUMPF TF 350–2 press, in accordance with the specified total thickness of the sheets. Tool change is quick and easy and does not require special tools or skills. The productivity of the TRUMPF TF 350–2 press is 2 rivets per second. The tool is suitable for both portable and stationary applications.
Seam connection. The Pittsburgh fold is an ideal connection method for straight or curved boxes. A smooth, dense and aesthetic connection is obtained without any additional processing when using TRUMPF F 300 series tools. The Pittsburgh fold ("American") is obtained