1 quality control in preparation stage
1. 1 Strictly check the quality of building materials.
Regardless of the materials supplied by Party A or purchased by the construction unit, the material management personnel shall strictly and carefully check the specifications and quality of the materials and conduct spot checks. If the sampling inspection is unqualified, materials are not allowed to enter the site; Materials such as quality certificate and factory certificate are not allowed to enter the site; Make a detailed record of the materials entering the site every time.
1.2 Strictly control the quality of HVAC equipment.
It is necessary to strictly control major equipment and materials, especially important equipment such as water chillers, boilers, air conditioning terminal units, pumps and fans. The main means of quality control is to check the ex-factory quality certificates of materials and equipment, and the specifications and performance must meet the relevant national standards and the design requirements of specific projects, and carry out corresponding tests according to the specification requirements. Unqualified products shall not be used.
1.3 Review the construction plan
Construction scheme review is the main content and steps of quality control before the project starts. The contractor shall prepare the construction scheme according to the actual situation of the project construction, and its quality control shall meet the quality standards required by the specifications, procedures and design. The supervision engineer should focus on whether the construction arrangement is reasonable, whether the construction machinery and personnel are properly configured, whether the construction method is feasible, whether the external conditions for construction are available, and whether the quality assurance measures are complete. , and carefully review the technical difficulties and key parts of the construction scheme and technical guarantee measures. At the same time, the quality control objectives of the coordination contractor should be consistent with those of the supervisor, and there should be no contrast.
2 pay attention to the reserved holes for HVAC installation
In some construction projects, the reserved holes in HVAC construction drawings are not specified in detail due to the poor cooperation of designers, low technical level or negligence. For example, in the construction of a large office project in a province, the author encountered that the reserved holes were not marked on the drawings, which made it impossible to reserve holes and embed related components during construction; In addition, even if the location and size of reserved holes are indicated in the drawings, HVAC construction personnel still need to conduct strict audit before construction to prevent holes from being missed due to the negligence of construction personnel, because if holes are missed, holes will be opened in the shear wall during later construction, which will cause serious damage to the shear wall structure, leave potential safety hazards, consume a lot of manpower and material resources and adversely affect the construction progress.
In the process of structural construction, certain measures should be taken to protect the reserved holes. Protective measures have two main purposes:
1) to prevent people or things from falling into the hole during construction;
2) Prevent it from being occupied or blocked in the construction of other sub-projects.
Key points of quality control in HVAC installation and construction
3. 1 Manufacture and installation of air duct
When making and selecting materials for air ducts, they should be selected according to the drawings and the relevant provisions of the Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Engineering, so as to avoid the large side of air ducts from sinking and deformation in different degrees due to insufficient stiffness, which will lead to noise caused by surface vibration during system operation, environmental pollution and reduce service life. Generally, the glass fiber reinforced plastic duct is made by hand-pasting method, that is, the glass cloth is laid on the mold, coated with glue, and then peeled off after curing. In the actual operation process, be careful not to uncover the film prematurely, and put it on a flat site after uncovering the film to avoid the deformation and skew of the air duct. When the flanges of air duct flanging are connected, the flanging shall be ≮6mm and close to each other, and the cracks at the four corners of air duct flanging shall be welded or coated with sealant. When connecting flanges, bolts should be in the same direction, with gaskets and 2 ~ 3 exposed threads.
3.2 Slope control of main heating pipe
The gradient of the main heating pipeline is determined by the pipeline support. As long as the position and elevation of the pipe rack can meet the design during construction, there is no problem of inappropriate slope. However, in practical engineering, the problem of inappropriate slope often occurs, so it is necessary to analyze the reasons for the inappropriate slope of the main heating pipe and take targeted measures.
Through a lot of engineering practice, it is found that there are two main reasons for improper slope placement:
1) The main heating pipe may not be straight during construction, or the position of the main heating pipe changes greatly after the hole gap in the pipe wall is filled up, which will also lead to inappropriate slope;
2) The construction quality of the pipe rack that determines the gradient of the heating main pipe does not meet the design requirements. For example, there is a big deviation between the position and elevation and the design, so that the pipeline will bend to a certain extent, and the local slope of the main pipeline will be reversed or the slope will change greatly, which will lead to the accumulation of gas and water in the pipeline and adversely affect the normal operation of the system function.
In view of the two reasons that lead to the improper gradient of the main pipe, it is necessary to take targeted measures to solve the problem of improper gradient of the main pipe. First of all, straighten the supervisor before installing it. For air conditioning water pipes, if the horizontal distance is too large, an exhaust valve should be installed at the climbing height and a drain valve should be installed at the descending position. In order to avoid similar situations, the whole system should be fully considered in the construction process to avoid losses caused by rework.
3.3 Problems in the manufacture and installation of the bracket
In the process of HVAC installation and construction, the problem of mixing fixed brackets and movable brackets often occurs. In some projects, only one kind of bracket is used. Mixed supports or only one kind of supports will lead to the failure of pipeline expansion and contraction in the predetermined direction. To further solve this problem, it is necessary to strengthen the quality education of construction technicians, so that construction workers can deeply understand the differences between fixed supports, guide supports and movable supports, and ensure that the types of supports can be correctly selected during construction, thus avoiding the above problems in construction.
3.4 Position control of main outlet and riser outlet.
The position of the supervisor and riser is not allowed, and the coordinates and elevation of the radiator are not accurate. The inaccurate position of the main pipe and riser is mainly caused by measurement error, followed by the deviation of the central axis of civil construction. Elevation is not allowed to be mainly manifested in the elevation difference in the same place, which exceeds15 mm. Before installation, draw a unified elevation line to ensure the consistency of elevation.
3.5 Equipment installation
Before the installation and construction of HVAC equipment, the ground of the computer room should be ready, the wall surface should be painted, and the equipment foundation should be completed and accepted. The direction of the equipment should correspond to the direction of the pipeline as far as possible, and whether there is maintenance space around the equipment should also be considered. The installation of the fan coil unit should match the height of the decorative ceiling and the position of the air return opening, and the orientation of the water collecting tray should be consistent with the drainage direction. The connection between the fan coil unit and the pipeline shall be elastic connection pipe or soft connection pipe, and its pressure resistance value shall be higher than 1.5 times of the working pressure. Hose connection shall be firm, and there shall be no strong twist or flat pipe. Fan coil units shall be inspected and accepted before entering the site, and single machine three-speed trial operation and water pressure test shall be conducted. The test pressure is 1.5 times the working pressure of the system, and it is qualified if there is no leakage. The slope of the drainage pipe should meet the design requirements, the condensed water should flow smoothly to the designated position, and the water supply and return valve and water filter should be installed near the fan coil unit. When two cooling towers are connected in parallel, it is best to set a pressure equalizing pipe in the middle of the water collecting tray, which has the same diameter as the water inlet pipe and a valve in the middle. It is best to set a connecting pipe between the supply and return water of the water pump and a check valve in the middle. The damping foundation of the main engine and other equipment must be well done, and the levelness should be within the allowable deviation. Otherwise, it is easy to cause excessive vibration or noise when the unit is running.
4 Quality control in comprehensive debugging stage
This stage is the last stage of the whole HVAC installation project. It plays a key role in the normal use of the whole project. Before comprehensive debugging, first review the debugging scheme of the construction unit and suppliers, carefully organize and cooperate, and actively coordinate the mutual cooperation between each type of work process and each construction team. Clarify the test and inspection requirements of pipelines and related equipment of each system. Before debugging each system, all preparations must be made, and before entering the debugging stage, all components and functions of all systems must be carefully checked. For example, first check the air conditioning unit, wind pressure and air volume, the opening and closing of fire dampers, the operation and refrigeration of chillers in high and low areas. In addition, check the operation and voltage stabilization of various pumps in HVAC and water supply and drainage systems. Whether the valve switch is flexible, whether the key equipment and accessories are complete, whether it is flexible to use, and whether the water pipes of the vertical branch pipes of the drainage system are leaking or blocked. Debugging must be carried out in strict accordance with the debugging program in the debugging scheme. Only after each subsystem has passed the subsection or layered debugging can the system be fully debugged. And cooperate with the construction unit to carefully record the system debugging for the use of completion data.
In a word, in the process management of HVAC construction, the work should not only be carried out according to the specifications and drawings, but more importantly, a reasonable construction scheme should be adopted according to the actual situation and on the premise of safety first. With lower cost and more exquisite technology, better economic and social benefits can be obtained.
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