Key points for quality control of the hottest vent

Key points for quality control of ventilation and air conditioning installation

ventilation and air conditioning installation project is an important divisional project in construction engineering. Ventilation and air conditioning installation should be in strict accordance with the requirements of specifications and inspection and evaluation standards, adopt necessary technical means and installation process, install and debug each sub item and system, and check whether it can meet the expected functional needs after trial operation. Combined with many years of construction experience, I put forward the following suggestions for reference only

1. Make all construction preparations and strictly control the five levels. Namely: joint review of drawings, technical disclosure, construction in strict accordance with drawings, material mobilization inspection, quality of construction personnel

1.1 before construction, foremen, technicians and quality inspectors must first organize relevant personnel to carefully review the drawings, master the design intent of the drawings, and at the same time, find errors, omissions and unreasonable problems in the drawings and solve them in time, which is an important factor to ensure quality and construction progress

1.2 according to the construction contract, the construction shall be carried out in strict accordance with the design drawings, and the design shall not be changed at will. If the jet tuyere cannot be changed into a spherical nozzle at will, the use effect will be affected; If there is any problem, communicate with the designer in time and go through the change negotiation procedures

1.3 make detailed construction scheme and technical disclosure before operation, and clarify the construction preparation, construction technology, quality standard, finished product protection, quality and other issues that should be paid attention to in each process; Detailed drawings of key parts and special practices shall be drawn, and the template guide shall be done well, and the installation template system shall be implemented

1.4 select a labor construction team with good quality, have good management level, construction skills and similar construction experience, and ensure that operators work with certificates

1.5 the purchase of equipment and materials must be based on the specifications of the design drawings. The budgeter puts forward the material plan, and the materialman purchases it uniformly. We should compare goods with other companies, and ensure high quality and low price. The purchased equipment and materials must have factory certificates and inspection and test reports. Unqualified products are not allowed to be purchased. Any materials and equipment can be used only after passing the inspection or test and being approved by the inspection supervisor

2. Effectively implement the three inspection system for process handover

pay close attention to enterprise self inspection. Construction enterprises should carefully carry out self inspection, mutual inspection and handover inspection of process handover. Strengthen mutual inspection and handover inspection of teams. The project quality control function should be carefully performed, and various quality inspections and supervision work should be done before, during and after the construction stage. Pay special attention to carefully check whether the quality self assurance system of the construction unit is sound and perfect, and strictly supervise and inspect its implementation

3. Strengthen the control of five elements (human, material, machine, method and environment)

3.1 check, evaluate, guide and adjust the skills and technologies of operators who implement key technologies, and timely correct or replace those who do not adapt

3.2 check, identify and control the capacity of machines and tools, and check and control the use, maintenance and servicing of construction machines and tools

3.3 control the factory data, mobilization acceptance, use marks and necessary tracing of materials

3.4 analysis, determination, evaluation, test, improvement, implementation, inspection and other activities of the methods and processes used in the main control key technologies

3.5 control the construction environment, storage environment and operation environment

4. Quality of main subdivisional works, control key points

4.1 construction of pipe pre hole or embedded sleeve

4.1.1 basement pipe passes through waterproof outer wall according to the calculated displacement, and rigid or flexible waterproof sleeve shall be embedded with the structure

4.1.2 holes shall be reserved along with the structure at the places where the pipeline passes through the wall, floor slab and roof. The casing shall be buried after the structural construction is completed. Both ends of the reserved casing through the wall must be sealed with adhesive tape

4.1.3 the pipes and pressure measuring pipes passing through the civil air defense floor, civil air defense wall and civil air defense diffusion chamber shall be embedded with the structure

4.1.4 the position of smoke exhaust valve (port) and manual control device (including embedded casing) shall meet the design requirements. The embedded casing shall be free of dead bending and collapse

4.1.5 in residential engineering, the air conditioning condensate pipe and outdoor unit connecting pipe must be embedded in advance. Refer to 88j-w17 for the practice

4.1.6 the reserved hole of the air duct is generally 100 mm larger than the size of each side of the actual section of the air duct

4.2 fabrication and installation of air duct

4.2.1 the marking method of air duct processing can be the right angle line method. Parallel line method is adopted for expansion. According to the different geometric shapes and specifications of air ducts in the detail drawing, draw lines and expand them respectively, and cut them. After blanking, the plate must be chamfered before rolling

4.2.2 the appearance quality of the air duct should be straight, the arc should be uniform, the two ends should be parallel, there should be no warping angle, and the surface concave convex should not be greater than 5 mm; The air duct is firmly connected with the flange, and the flanging is flat, with a width of not less than 6 mm, close to the flange; The hole spacing of the air duct flange shall meet the design requirements and the provisions of the construction specifications, and the welding shall be firm. No screw holes are set at the weld, and the screw holes are interchangeable; When the side length of rectangular air duct is greater than 630 mm and the insulation air duct is greater than 800 mm, reinforcement measures should be taken. The reinforcing bars of angle steel should be arranged neatly, evenly, symmetrically and firmly fixed. 4.2.3 when the right angle elbow of the air duct or the side length is greater than 500 mm, a deflector should be added at the elbow to enable the air flow to pass smoothly and reduce the wind resistance

4.2.4 first place the installation line in advance according to the design drawings. The elevation of the supports and hangers must be correct. The buried part of the expansion bolts of the supports and hangers shall not be painted, and the oil stain shall be removed. Supports and hangers shall not be installed at air vents, valves, inspection holes, etc. The hanger shall not be directly hung on the flange

4.2.5 the connection between air duct and components and equipment is mainly connected by hose, and the material should be non combustible or flame retardant material. The installation of air duct depends on the construction site, which can be hoisted as a whole or in sections; Generally, the installation sequence is from main pipe to branch pipe, and the installation of vertical air duct is generally from bottom to top

4.2.6 the installation direction and position of fire dampers should be correct. When the diameter or long side size of the fire damper is greater than or equal to 630 mm, independent supports and hangers should be set. The inspection hole of the fire damper installed on both sides of the partition wall of the fire compartment can be easily observed, repaired and disassembled, and the distance from the wall surface should not be more than 200 mm

4.2.7 when the air duct passes through the firewall body or floor, the embedded pipe or protective sleeve should be set, and the thickness of its steel plate should not be less than 1 6 mm, between the air duct and the protective sleeve, it should be blocked with non combustible and non harmful flexible materials

4.3 installation of pipes in the shaft

the risers for air-conditioning refrigeration and air-conditioning hot water to supply water to high-rise buildings are mainly concentrated in several pipe shafts. Therefore, before construction, the paper setting out of drawings should be carefully carried out and adjusted to facilitate the completion of various installation processes (pipeline corrosion prevention, pipeline test, pipeline insulation and other processes), and also create conditions for future owners to maintain and manage. Due to the large number of pipes in the shaft, the piping and installation work is more complex than the installation of pipes in the general shaft. Before installation, the paper setting out and field setting out arrangement procedures should be carefully done to ensure the smooth progress of the installation work. For the installation of the riser in the shaft, a section steel support shall be set at the wellhead, and the upper and lower parts of the riser shall be installed with a unified hanging line. The concealed branch pipes shall be marked and positioned, and the prefabricated branch pipes shall be laid at the predetermined position, and fixed with hooks after alignment. The support of the pipeline shall be calculated and redesigned, and the embedded parts shall be buried well when the civil engineering discipline supports the formwork. Due to the long riser length of air-conditioning chilled water, etc., although the temperature difference is not too large, the straight-line length of the pipeline is long. In order to ensure the safe operation of the system, expansion joints and fixed supports are set in the pipeline shaft according to the design requirements

4.4 installation of fan coil unit and other equipment

4.4.1 before the mobilization of fan coil unit, the mobilization acceptance shall be carried out, and the single machine three speed test run and hydraulic test shall be carried out. The test pressure is 1.5 times of the working pressure of the system, and it is qualified if there is no leakage. The horizontal unit shall be fixed by supports and hangers and shall be easy to disassemble and maintain; The slope of the drainage pipe should meet the design requirements, the condensate should flow smoothly to the designated position in the design, and the water supply and return valve and water filter (should be set to prevent blockage) should be installed close to the fan coil unit. The connection between fan coil unit and pipeline should adopt elastic connecting pipe or soft connecting pipe (metal or non-metal hose), and its pressure resistance value should be higher than 1.5 times the working pressure. The hose connection should be firm, and there should be no strong twist or flat pipe. The residual oil of the fins should be cleaned before the equipment leaves the factory, otherwise it is easy to cause the condensed water to not be smoothly discharged into the ponding pan and smoke

4.4.2 the fresh air population of the air conditioning (fresh air) unit shall be equipped with electric air valve and interlocked with the fan to prevent the heat exchanger from freezing and damaging due to too low temperature in winter. Bypass branches shall be set in front of the inlet and outlet pipelines of the unit (especially when there are electric valves) for flushing and repairing pipelines before operation; The ponding pan must be tight and watertight; The heat exchanger shall be provided with maintenance space after freezing

4.4.3 when two cooling towers are connected in parallel, it is best to set a pressure equalizing pipe in the middle of the water collecting pan, with the same diameter as the water inlet pipe, and a valve in the middle. A connecting pipe should also be set between the water supply and return of the water pump, and a check valve should be set in the middle. Otherwise, it is easy to cause the phenomenon that one tower overflows and the other tower keeps replenishing water during the operation of two towers

4.4.4 the shock absorption foundation of the main machine and other equipment must be done well, and the levelness must be within the allowable deviation. Otherwise, it is easy to cause vibration or excessive noise during unit operation

4.5 pipeline flushing test

after the air conditioning water pipeline is installed according to the specified slope, the flushing before use should be carried out with the maximum flow of the system, and the water quality transparency of the flushing outlet is required to be consistent with that of the water inlet. Before flushing, the flow orifice and filter installed in the pipeline should be removed, and the bypass pipeline should be set in front of each unit to connect directly. It can be installed after the flushing is qualified. It is not allowed to use pressure test water for flushing test. Flushing should be carried out by system and section. After washing the unit, open the vent valve on the top to drain all the water to prevent the water from freezing and cracking the heat exchanger in winter. Flushing test is a prerequisite for preventing blockage, ensuring water quality, function and use safety of pressure pipelines and equipment before trial operation. It must be carried out carefully, otherwise there are certain impurities such as welding slag in water chillers, surface coolers and whole process water processors, which will have a certain impact on the normal operation of equipment

4.6 air duct inspection

after the installation of the air duct system, the tightness inspection should be carried out according to the system category, and the strength of the air duct should be able to ensure that there is no crack at the joint under 1.5 times the working pressure. The allowable air leakage of rectangular air duct shall meet the specification requirements. Under the premise of ensuring the processing technology, the tightness inspection of the air duct of the low-pressure system adopts the light leakage method. If the test is unqualified, the air leakage shall be tested according to the specified sampling rate; After the tightness inspection of the air duct of the medium pressure system passes the light leakage inspection, select a special air leakage tester to conduct a spot check of the air leakage; Air leakage test is required for the tightness inspection of air duct of high-pressure system. 4.7 ventilation and air conditioning system commissioning

4.7.1 air volume balance of air duct system

the air volume of each part of the system should be adjusted to the value required by the design, and the air volume can be adjusted by changing the air volume with the regulating valve. Commissioning can start from the end of the system, that is, from the branch pipe farthest from the fan, and gradually adjust to the fan, so that the actual air volume of each branch pipe reaches or approaches the design air volume. Finally, when the air volume of the fan is adjusted to the design value, the air volume of each part of the system can still meet the requirements. That is, after the air volume of the system is adjusted and balanced, it should reach: ① the deviation between the measured value of the air volume, fresh air volume, exhaust air volume and return air volume of the air outlet and the designed air volume should not be greater than 10% by replacing the pendulum and sample base; ② The sum of air volume and return air volume