Air conditioning water system installation and construction technology

Air-conditioning chilled water system: This system is mainly composed of refrigeration units, chilled water pumps, chilled water pipes and indoor terminal equipment (fan coil units, air handling units, etc.). The low-temperature chilled water flowing out from the refrigeration unit passes through the chilled water The pipe is input to the indoor terminal equipment to exchange heat with the indoor air, taking away the heat in the room to achieve the cooling effect, and finally returns to the refrigeration unit to complete a cycle.

The chilled water system provides a cold source for the entire air conditioning system.

Air conditioning cooling water system: This system consists of refrigeration units, cooling water pumps, cooling water pipes, cooling towers, etc. While the chilled water circulation system performs indoor heat exchange, it will definitely take away a large amount of indoor heat energy. This heat energy is transferred to the cooling water through the refrigerant of the refrigeration unit, causing the temperature of the cooling water to increase. Then the cooling water is forced from the refrigeration unit through the cooling water pipe to the cooling tower, where it exchanges heat with the atmosphere, lowers the temperature, and is then sent back to the refrigeration unit.

The air conditioning cooling water system is a system that dissipates heat for the entire air conditioner.

Condensate water system: When the indoor air conditioning terminal equipment (fan coil unit, air handling unit) performs heat exchange with the indoor air, because it is lower than the dew point temperature of the indoor and outdoor air,The water vapor in the air will precipitate on the cold wall surface and condense, and finally be discharged through the condensate pipe.

Introduction to the main equipment of the air conditioning system:

1. Water-cooled chiller

Main function: to produce 7℃ chilled water to provide cold source for the entire station’s air conditioning system.

2. Combined air conditioning processing unit

Air treatment equipment performs heat exchange with indoor air and processes indoor air. It is mainly used in large systems and large spaces in stations.

3. Fan coil

The unit continuously recirculates the air in the room or outside, so that the air passes through the cold water (hot water) coil and is cooled (heated) to maintain a constant room temperature.

4. Water collector

The central air-conditioning water distributor and water collector are set up to facilitate the connection of parallel pipes in each water loop, and play a pressure equalizing role to ensure uniform flow distribution.

5. Chilled water pump and cooling water pump

Chilled water pumps and cooling water pumps are mainly power equipment provided for chilled water and cooling water circulation.

6. Cooling tower

Heat dissipation equipment uses water as the circulating medium to transfer the heat on the condenser side of the refrigeration unit (that is, the heat absorbed from the room) through the flow of water in the cooling tower and then transfers the heat to the air around the cooling tower. , after heat dissipation, it enters the central air conditioning condenser again to absorb heat.

Central air conditioning water system process:

Chilled water circulation system: The low-temperature chilled water flowing out from the evaporator of the refrigeration unit enters the water distributor, and is then distributed to the indoor terminal equipment (fan coil unit, air handling unit) through the water distributor, and then heats it with the indoor air. Exchange, take away the heat in the room, achieve cooling, and finally return to the host evaporator through the chilled water pump to complete a cycle.

Cooling water circulation system: While the chilled water circulation system performs indoor heat exchange, it will take away a large amount of indoor heat energy. This heat energy is transferred to the cooling water through the refrigerant in the host machine, causing the temperature of the cooling water to rise, and the cooling water enters In the cooling tower, it exchanges heat with the atmosphere, lowers the temperature, and then returns to the condenser of the refrigeration unit through the cooling circulation water pump.

Common pipe types in air conditioning water systems:

Seamless steel pipeIt is a round steel material with a hollow section and no seams around it. Seamless steel pipe has a hollow section and is widely used as a pipeline for transporting fluids. It is light in weight and is an economical cross-section steel. It is often used for transportation Seamless steel pipes for ordinary fluids (GB/8163-2018), the main fluids transported are For non-corrosive media such as water, oil, and steam, the representative materials are 20 and Q345. Seamless steel pipes have strong pressure-bearing capacity, and are widely used in pipes with diameters above DN100. The working pressure capacity does not exceed 6MPa.

Galvanized steel pipe , a welded steel pipe with a hot-dip or electro-galvanized layer on the surface. Galvanizing can increase the corrosion resistance of the steel pipe and extend its service life. Galvanized pipes are widely used, except for water, gas, oil, etc. In addition to general low-pressure fluid pipeline pipes, it is also used as oil Industry, especially oil well pipes and oil pipelines in offshore oil fields, pipes for oil heaters, condensation coolers, coal distillation oil exchangers, and pipes for trestle pipe piles and support frames of mine tunnels in chemical coking equipment.

Welded steel pipe refers to bending and deforming a steel strip or steel plate into a circle , square and other shapes and then welded into steel pipes with seams on the surface. The blanks used for welded steel pipes are steel plates or strips.

Plastic coated steel pipe Also known as plastic-coated pipe, steel-plastic composite pipe, and plastic-coated composite steel pipe, it uses steel pipe as the base, and a layer of plastic anti-corrosion layer is fused to the inner surface of the steel pipe (bottom pipe) through spraying, rolling, dipping, and suction processes. Or steel-plastic composite steel pipes with plastic anti-corrosion layers fused to the inner and outer surfaces

Plastic-coated steel pipes have excellent corrosion resistance and relatively small friction resistance. Epoxy resin-coated steel pipes are suitable for water supply and drainage, seawater, For the transportation of warm water, oil, gas and other media, PVC-coated steel pipes are suitable for the transportation of drainage, sea water, oil, gas and other media.

Air conditioning water system pipe selection requirements:

Cold water pipe, cooling water pipe, condensate water pipe, expansion water pipe, nominal diameter ≤ DN80 Galvanized steel pipes are used, seamless steel pipes are used for DN100 ≤ nominal diameter < DN300, and spiral welded pipes are used for ≥ DN300. The outer diameter and wall thickness of seamless steel pipes and spiral welded pipes are as follows. The material of seamless steel pipe should comply with the requirements of GB/T8163-2018.

The following focuses on the construction technology and related requirements of seamless steel pipes for air conditioning water.

Construction process of air conditioning water system:

Construction preparation → Coordinate measurement → Bracket prefabrication and installation → Pipe prefabrication → Pipe installation → Installation of pipe valves and accessories → Installation of corrugated compensator→Connection of pipelines and units (equipment)→Installation and inspection of condensate water pipelines→Pipeline pressure test and flushing→Concealed project acceptance→Pipeline insulation.

Construction preparation: Be familiar with technical requirements such as construction drawings and pipeline process flow, transmission medium temperature, pressure and connection form, as well as construction acceptance specifications. At the same time, carefully review the construction drawings, pay attention to the design depth and completeness of the construction drawings, and promptly raise and solve problems existing in the design drawings.

Coordinate determination: According to the coordinate position, pipe diameter, category and specification requirements of the pipeline marked in the design and construction drawing, timely recheck the coordinate position and size of the reserved hole for the pipeline completed by the civil engineering to see if it is consistent. Based on the location of existing buildings and equipment and the indoor elevation baseline, a single-line pipeline processing prefabricated drawing and a bracket processing prefabricated drawing are drawn.

Bracket prefabrication: Process according to the actual size of each bracket, from marking and blanking, positioning and drilling to welding and forming, and paint and anti-corrosion work (two coats of primer, one coat of topcoat, and then painting after the pipeline is installed) paint once).

Bracket installation: The pipe bracket form is reasonably selected, the installation is smooth and firm, and the arrangement is neat and uniform. The pipe is in close contact with the bracket. The supports and hangers fixed on the building structure shall not affect the safety of the structure, and the supports and hangers shall not have defects such as missing welding, under-welding or welding cracks. After the bracket is installed, the process inspection must be carried out. Installation can only be carried out after passing the inspection.

Pipe brackets are divided into: portal brackets, cantilever brackets, hangers and pressed elbow drag brackets, etc.

Maximum spacing between steel pipe pipe supports:

Prefabrication and installation of seamless steel pipes:

Pipe prefabrication: When the nominal diameter of the seamless steel pipe is ≤50mm, it should be cut by machinery or a hacksaw or a pipe cutter. The fracture is not allowed to have necking or burrs, and must be welded by gas welding. When the nominal diameter is ≥65mm, it should be cut Hepo The joints can be cut and beveled mechanically or with oxyacetylene gas, but there should be no cracks or burrs on the surface. For welded joints, the welding quality must meet the requirements of GB50236.

Pipe installation requirements:

1) Before installing various pipelines, you should check whether the pipelines are coordinated with the elevation of the building decoration surface where they pass. In rooms with suspended ceilings and raised floors, you should check whether the pipeline elevations meet the requirements. Equipment clearance requirements to avoid pipeline rework due to civil construction errors

2) Cold water pipes, cooling water pipes, condensate water pipes, expansion water pipes, nominal diameter ≤ DN8 are galvanized steel pipes, DN100 ≤ nominal diameter < DN300 Seamless steel pipe is used, and spiral welded pipe is used for ≥DN300.

3) The nominal diameter ≤ DN80 is connected with threads, and the connection with the equipment is For flanges or flexible rubber joints, a rubber gasket with a thickness of 3 mm is placed between the opposing flanges. Nominal diameter >DN80 adopts welding connection. When welding is used, flange connection must be strengthened at certain intervals, and the tee must be connected with flange.

The tee must be connected with a flange. Threaded connections, welded connections, and flange connections should comply with the requirements of the \”Construction Specifications for Ventilation and Air-Conditioning Projects\” (GB 50738-2011) and \”Construction Quality Acceptance Code for Ventilation and Air-Conditioning Projects\” (GB50243-2002). For directly buried water pipes, Enhanced anti-corrosion should be used to ensure the service life of the pipeline.

4) The pipe elevation is the pipe bottom elevation. All air-conditioning horizontal pipes are laid parallel to the top surface of the civil construction. A DN15 automatic exhaust valve (with ball valve) should be installed at the high point or partial elevation of the main pipe. In addition to what has been considered in the design drawings, if there are changes in pipeline laying due to the intersection of processing pipelines during construction, additional installations should be made, and automatic exhaust valves should be avoided as much as possible in the suspended ceiling. Install a DN25 drain valve or plug at the lowest point of the pipeline. The drainage from the automatic exhaust valve and drain device should be discharged to the nearest floor drain or drainage ditch.

5) The flange sealing gasket is made of medium heat-resistant rubber sheet, and the flexible rubber soft joint must be equipped with a limiting device.

6. Corrugated pipe compensators should be installed every 50m in long straight pipe sections. For pipes equipped with compensators, fixed brackets and guide brackets should be installed. When the pipe passes through a deformation joint ( Settling joints) should be provided with metal hoses and fixed brackets at both ends.

7) After the water system is installed and not insulated, a hydraulic pressure test should be carried out. The test can be carried out in different loops. The test pressure is 1.5 times the working pressure, and it is qualified if there is no leakage or leakage. The water tank must be fully filled During the water test and pressure test, the equipment must not be connected to the pipe network. The water pump should be started to flush the entire loop and circulate for 24 hours until it is flushed. The water system must not be connected to the equipment until it is flushed.

8) Pipes passing through walls or floors should be equipped with steel casings. When passing through floors, the top of the casing should be 20mm higher than the decoration layer. The welds should not be placed inside the casing. The gap between the pipe and the casing should be Filled with non-combustible insulation material

9) Pipe supports and hangers must be installed outside the insulation layer, and anti-condensation insulation pads (insulation pads) with a thickness equivalent to the insulation requirements should be added where they pass through the supports and hangers. The insulation pads are dipped Curved wooden blocks covered with asphalt. The pressure-bearing strength of the thermal insulation liner should be able to meet the weight of the pipe, the thickness should not be less than the thickness of the insulation layer, and the width should be greater than the width of the support and hanger support surfaces.

The pipes of the air conditioning water system are generally Selection: seamless steel pipe, welded steel pipe, galvanized steel pipe, organic material pipe (rigid polyvinyl chloride (PVC-U), polypropylene (PP-R), polybutylene (PB), and cross-linked polyethylene (PEX).

Connection:

A. Galvanized steel pipe:

Pipe diameter less than or equal to 100mm: threaded connection;

Pipe diameter greater than 100mm: flange or clamp-type special pipe fittings connection.

B. Welded steel pipe:

Pipe diameter less than or equal to 32mm: threaded connection;

Pipe diameter greater than 32mm: welding.

C. Seamless steel pipes: all are welded.

D. Water supply steel-plastic composite Pipe:

Threaded connection can be used when the pipe diameter is not greater than 100mm, and flange or groove connection can be used when the pipe diameter is greater than 100mm.

E. Plastic pipes: hot-melt connection, mechanical locking connection, adhesive connection, and plug-in connection can be used.

Notes on installation:

A. The slope of the condensate drain pipe should be greater than or equal to 8‰;

B. The length of the hose connection should not be greater than 150mm;

C. For the supports and hangers of the main pipe in the machine room of the cold (hot) medium water and cooling water system pipes, load-bearing anti-sway pipe racks should be used; the pipes connected to the equipment The pipe rack should have vibration reduction measures;

D. When the single-pole hanger is used for the pipe rack of the horizontal branch pipe, it should be installed at the starting point of the pipe, valves, tees, elbows and lengths every 15m Load-bearing anti-sway supports and hangers.

Casing production and installation:

1) Casing diameter It should be 1 to 2 sizes larger than the diameter of the main pipe and riser passing through the wall panel.

2) The length of the casing: the length of the wall casing = wall thickness + plaster thickness on both sides of the wall.

3) The casing should be filled with loose materials to prevent concrete pouring from clogging the casing.

Installation and piping of air conditioning equipment and accessories:

1. Chiller installation

The methods and steps are as follows:

1. Space size: If allowed during installation, please leave enough space;
2. Keep the whole machine level during installation;
3. The power supply of the ice water machine is required to be connected correctly. Power cord;
4. Keep the whole machine grounded;
5. The cooling and ice water machine pipelines are smooth, and the cooling management can be better than the machine pipelines Slightly larger, the cooling effect should be sufficient after consideration;
6. It is recommended to power on for 12 hours before starting the machine, especially for large screw ice water machines;
7. Make sure the water level in the ice water tank is sufficient before starting the machine;
8. Turn on the cooling system first;
9. Complete the boot.

Notes:
1. The location of the water inlet and outlet is correct;

2. The power phase is correct;
3. The machine remains level;

4. The neutral line is correct. Do not connect it reversely with the bottom line;
5. Keep it grounded for a long time. Electric leakage may hurt people.

2. Installation of cooling tower

1. The cooling tower should be installed smoothly and the anchor bolts should be firmly fixed.

2. The water outlet of the cooling tower The direction and position of the nozzle should be correct and the water should be distributed evenly. For cooling towers with rotating water distributors, the rotating part must be flexible. The water spray outlet should be downward at an angle of 30° to the horizontal, and in the same direction, and should not be vertically downward.

3. The installation of fiberglass cooling towers and cooling towers with plastic fillers should strictly comply with fire prevention regulations.

3. Sub-water collector

(1) The water collector should be installed before laying the heating pipe. When installed horizontally, it is generally suitable to install the water collector on the top and the water collector on the bottom. The center distance should be 200mm. The center of the water collector should be no less than 300mm from the ground. When installed vertically, the distance between the lower end of the water distributor and the water collector should be no less than 150mm.

(2) The location should be located in a place that is easy to control and maintain and has drainage pipes, such as toilets, kitchens, etc. It should not be located in bedrooms, living rooms, let alone storage rooms, cabinets, etc. Can be located in indoor duct wells

(3) For rooms that are semi-cross-floor, the water distributor and water collector should be set at the high point or high and low areas respectively; for full-cross-floor (duplex) rooms The structure should be located on the corresponding unified main pipes on the upper and lower floors.
4. Installation of air conditioning units

1. Classification of air conditioning units

1) Unit structure classification: cabinet type and combination;

2) Installation method classification: vertical, horizontal and ceiling-mounted.

Cabinet air conditioning unit, also called integrated air conditioning unit, is a unit that integrates air filter, surface cooler, heater, humidifier and other air treatment components into a vertical cabinet box.

The pipes connected to the unit should be equipped with brackets, and their weight should not be borne by the unit.

Horizontal combined type:

Combined air conditioning units, also called assembled air conditioning units, are composed of different air treatment sections, such as fresh air section, return air mixing section, heating section, etc. Each component section is assembled using equipment selected according to design parameters, and sections can be assembled on site.

Ceiling type:

1. The boom should have sufficient strength;

2. Anti-loosening measures should be taken for the boom bolts;

3. Vibration isolation pads or spring vibration-absorbing hangers should be installed at the bottom of the unit.

Installation of air conditioning unit:

Installation process:

The air conditioning unit should be installed with sufficient room to prevent insufficient space around the unit from causing difficulty in operating the pipe interface;

At the same time, the installation space should be fully considered Go to the unit for inspection and maintenance, especially pulling out the filter, cleaning or replacing it.

Piping connections for air conditioning units:

No hydraulic test is required before installation. (The premise is that there is no external damage to the surface cooler within the qualification period). Otherwise, a hydraulic pressure test should be performed. The test pressure is 1.5 times the system working pressure and must not be less than 0.4MPa. The observation time is 3 minutes and the pressure drops.

The air-conditioning unit should have a slope of not less than 0.008 for the outlet of condensate water, and the condensate water pipe should be equipped with a water seal of ≥60mm.

Fan coil installation:

Definition: The fan coil unit is the terminal device of the central air conditioner

Composition: heat exchanger, fan, water tray, exhaust valve, etc.

Function: The indoor air or indoor and outdoor mixed air is cooled or heated through the surface cooler and then sent indoors to reduce or increase the indoor temperature to meet people\’s comfort requirements.

The working principle is that within the unit Continuously recirculates the air in the room, causing the air to be cooled (heated) after passing through the cold water (hot water) coil to maintain a constant room temperature.