Duct parts and muffler production

This chapter applies to the processing and production of other components such as air vents, air valves, exhaust hoods, and silencers in ventilation and air conditioning projects, or the acceptance of the quality of finished products.

1. General provisions

This section stipulates the general provisions for the acceptance of air duct components in ventilation and air conditioning projects. Air duct components are processed by construction companies according to the needs of the project, and there are also finished products purchased from outside. 

According to the development trend of engineering construction in my country, the pattern of air duct components mainly based on product production is gradually taking shape. For this reason, this article stipulates that general Air volume control valves shall be accepted according to the requirements for manufacturing air valves, and others shall be accepted according to the quality of purchased finished products. General air volume control valves refer to valves used in the system that do not require tight shutoff, such as three-way control valves, control valves for system branches, etc.

(Figure 1: Ventilation and air conditioning engineering pipe components)

2. Main control items

2.1 The handwheel or wrench of the manual single-blade or multi-blade regulating air valve should be turned clockwise to close, and its adjustment range and opening angle indication should be consistent with the blade opening angle.

The air valve used for intermittent working points of the dust removal system should be able to seal when closed.

Inspection quantity: 10% of the batch shall be inspected, not less than 1.

Inspection method: manual operation, observation inspection.

Note: This article stipulates the main control items for the quality acceptance of general manual damper adjustment.

2.2 The driving device of the electric and pneumatic damper adjustment should be reliable and work normally under the maximum working pressure.

Inspection quantity: 10% of the batch shall be inspected, not less than 1.

Inspection method: check the product's qualified certificate, performance test report, observation or test.

Note: This article emphasizes the acceptance of the reliability of the electric and pneumatic drive devices of the damper adjustment.

(Figure 2: Systems used for life-saving in construction projects)

2.3 Fire dampers and smoke exhaust valves (smoke exhaust ports) must comply with the provisions of relevant fire protection product standards and have corresponding product qualified certificates.

Inspection quantity: 10% of the batch shall be inspected by type and batch, not less than 2.

Inspection method: check the product's qualified certificate and performance test report.

Note: Fire dampers and smoke exhaust valves are life-saving systems used in construction projects, and their quality must comply with the provisions of fire protection products.

2.4 The materials used to make explosion-proof air valves must comply with the design requirements and must not be replaced by themselves.

Inspection quantity: All inspections.

Inspection method: Check the material types and specifications, visual inspection,

Description: Explosion-proof air valves are mainly used in flammable and explosive systems and places. Improper use of materials will cause serious consequences, so they must be strictly implemented during acceptance.

2.5 The movable parts, fixed parts and fasteners of the air valves in the purification Air conditioning system should be galvanized or treated with other anti-corrosion treatments (such as spraying or baking paint); the gaps between the valve body and the outside world should have reliable sealing measures.

(Figure 3: Purification air conditioning system)

Inspection quantity: 10% of the batch shall be randomly inspected, and no less than 1 piece shall be inspected.

Inspection method: Check the materials of the product, manually operate and observe.

Description: The strength and tightness of the air duct are one of the important indicators of the processing and manufacturing quality of the air duct, and must be met. The test of the air duct strength mainly checks the pressure resistance of the air duct to ensure the performance of the safe operation of the system. The acceptance requirement is that under 1.5 times the working pressure, there is no opening, cracking or other damage to the bite or other joints of the air duct.

2.6 For regulating air valves with a working pressure greater than 1000Pa, the manufacturer should provide a certificate (or test report) of qualified strength test (free opening and closing at 1.5 times the working pressure).

Inspection quantity: 10% of the batch shall be inspected, and shall not be less than 1

Inspection method: Check the product's qualification certificate and performance test report.

Note: This article emphasizes the acceptance of the reliability of the high-pressure regulating air valve.

2.7 The material used to make the flexible short pipe of the smoke exhaust system must be non-combustible material.

Inspection quantity: All inspections.

Inspection method: Check the qualification certificate of the material variety,

Note: When a fire occurs and the smoke exhaust system is used, the air temperature inside or outside the pipe is relatively high. If a flexible short pipe made of ordinary combustible materials is used, it is very easy to cause damage or ignition under high temperature baking, which will make the system function ineffective. For this reason, this article now stipulates that the flexible short pipe of the smoke exhaust system must be made of non-combustible materials.

(Figure 4: Smoke exhaust system)

2.8 When the plane side length of the muffler bend is greater than 800mm, a sound-absorbing guide plate should be added: the cloth surface layer on the direct windward side of the muffler should have protective measures; the covering inside the muffler of the purification air conditioning system should be a material that is not easy to produce dust.

Number of inspections: All inspections,

Inspection methods: Observation inspection, check the product's qualification certification documents,

Description: When the plane side length of the silencer elbow is greater than 800mm, its silencer effect decreases at an accelerated rate, while the resistance increases. Therefore, the article stipulates that sound-absorbing guide plates should be added to improve the airflow organization and improve the silencer performance. The covering materials of the resistive silencer elbow and the inner surface of the silencer are mostly glass fiber woven materials. Under the impact of the airflow in the pipe for a long time, the woven surface is easily loosened and the fibers are broken, causing the cloth surface to be damaged and the sound-absorbing material to fly. Therefore, this article stipulates that the cloth covering layer directly facing the wind in the silencer should have protective measures.

3. General Project

3.1. Manual single-blade or multi-blade regulating air valves shall comply with the following provisions

• The structure should be firm, opening and closing should be flexible, and the flange should be consistent with the corresponding material air duct:

• The overlap of the blades should be consistent, and the gap with the valve body should be less than 2mm;

• The air valves with a cross-sectional area greater than 1, 2- should be adjusted in groups.

Inspection quantity: 10% by category and batch, not less than 1.

Inspection method: manual operation, measurement, visual inspection.

3.2. Check air valves shall comply with the following provisions

• Open and close flexibly, and should be tight when closed:

• The shaft and hinge of the valve leaf should be made of materials that are not easy to rust to ensure flexible rotation and durability:

• The strength of the valve leaf should ensure that it does not bend and deform under the maximum load pressure:

• The horizontally installed check air valve should have a reliable balance adjustment mechanism,

(Figure 5: Air volume balancing valve)

Inspection quantity: 10% by category and batch, not less than 1 

Inspection method: observation, measurement, manual operation test and verification of product qualification certification documents.

3.3. The plug-in air valve shall comply with the following provisions

• The shell should be tight and the inner wall should be treated with anti-corrosion;

• The plug-in plate should be flat, flexible to open and close, and have a reliable positioning and fixing device:

• The upper and lower pipes of the inclined plug-in air valve should be in a straight line.

Inspection quantity: 10% by category and batch, not less than 1

Inspection method: manual operation, measurement, observation and inspection.

3.4. The three-way regulating air valve shall comply with the following provisions

• The joint between the rotating shaft of the pull rod or handle and the air duct should be tight:

• The pull rod can be fixed at any position, and the handle switch should indicate the adjustment angle:

• The valve plate is easy to adjust and does not rub against the air duct.

Inspection quantity: 10% by category and batch, not less than 1.

Inspection method: observation, measurement, manual operation test.

3.5. The air volume balancing valve shall comply with the provisions of the product technical documents

Inspection quantity: 10% by category and batch, not less than 1.

Inspection method: Observe, measure, and check the product's qualified certification documents.

(Figure 6: Muffler)

Note: The air volume balancing valve is a high-precision air valve, which is produced by professional factories, so it emphasizes acceptance according to product standards.

3.6. The production of the air valve should comply with the following regulations

Correct size, firm connection, regular opening, smooth surface, and its outer shell should not have sharp corners: the side suction hood and the slit exhaust hood should be correct in size, the arc at the corner should be uniform, the shape should be regular, the suction port should be flat, and the spacing between the hood reinforcement plates should be consistent; the kitchen stove exhaust hood should be made of non-rusting materials, the lower water collection hood should be tight and leak-proof, and slope towards the discharge port, and the oil fume filter in the hood should be easy to disassemble and clean. 

Inspection quantity: 10% of each batch should be randomly inspected, and no less than 1.

Inspection method: measurement, observation and inspection.

Note: This article only stipulates the basic quality acceptance requirements for the suction hoods frequently used in ventilation systems.

3.7. The production of hoods should comply with the following regulations

The size should be correct, the structure should be reliable, and the allowable deviation of the hood pipe size should be consistent with the regulations of the air duct:

The edge of the umbrella cover of the umbrella hood should be reinforced, and the support height size should be consistent; the centers of the inner and outer cones of the conical hood should be concentric, the connection of the cone combination should be smooth, and the lower drainage should be unobstructed. The shape of the cylindrical hood should be regular, the upper and lower edges of the outer cylinder should be reinforced, and its non-roundness should not be greater than A2% of the diameter. The distance between the edge of the umbrella cover and the outer cylinder should be consistent, and the position of the wind shield should be correct:

The angles of the three branches of the trident hood should be consistent, and the connection with the main pipe should be tight. The taper of the main pipe and the branch pipe should be 3°~4°.

Inspection quantity: 10% of the batch should be randomly inspected, and no less than 1.

Inspection method: measurement and observation inspection.

Explanation: This article stipulates the acceptance requirements for production quality according to the different types of hoods.

3.8. The windward edge of the rectangular curved pipe guide blade should be smooth and firmly fixed 

The curvature of the guide vane should be consistent with the angle of the elbow. The distribution of the guide vane should comply with the design requirements. When the length of the guide vane exceeds 1250mm, strengthening measures should be taken. 

Inspection quantity: 10% of the batch shall be inspected, and no less than 1 piece shall be inspected. 

Inspection method: Check materials, measure and observe. 

Note: The guide vane installed in the elbow can reduce the local positive force of the elbow. The processing of the guide vane can be in various forms and methods. Now it has gradually developed in the direction of stereotyped products, so the article emphasizes that the application performance of rectangular ducts of different materials is the same, rather than stipulating that they are made of the same material. The guide vane is placed in the short elbow, and the sharp edge on the windward side is prone to noise, which is not conducive to use in the system. 

(Figure 7: Flexible short tube)

3.9. Flexible short pipes should comply with the following regulations

Flexible materials that are anti-corrosive, moisture-proof, airtight, and not easy to toxic should be selected. Measures should be taken to prevent condensation for air-conditioning systems; materials used for purification of air-conditioning systems should also be made of materials with smooth inner walls and not easy to generate dust; the length of the flexible short pipe should generally be 150~300mm, and its connection should be tight, firm and reliable; the flexible short pipe is not used as a different-diameter connecting pipe for alignment and leveling; the length of the flexible short pipe installed in the structural deformation joint should be the width of the deformation joint plus 100mm or more. 

Inspection quantity: 10% of the quantity shall be randomly inspected, and shall not be less than 1.

Inspection method: measurement and observation inspection.

Description: The main function of the flexible short pipe is vibration isolation. It is often used at the inlet and outlet of fans or powered air-conditioning equipment as a connecting pipe in the air duct system; sometimes it is also used at the settlement joints of buildings as a telescopic pipe. Therefore, it is necessary to regulate and control its material, connection quality and corresponding length.

3.10. The production of silencers shall comply with the following provisions

The materials selected shall comply with the design requirements, such as fire prevention, anti-corrosion, moisture resistance and hygienic performance requirements; the outer shell shall be firm and tight, and shall be evenly laid according to the specified density, and measures shall be taken to prevent sinking. The covering layer of the silencer material shall not be damaged, and the overlap shall be in the direction of air flow. The interface shall be free of burrs, and the joints between the partition and the wall panel shall be close and tight; the perforated plate shall be flat and burr-free, and its aperture and perforation rate shall meet the design requirements. 

Inspection quantity: 10% shall be inspected by batch sampling, and shall not be less than 1.

Inspection method: measurement, observation and inspection, and verification of the certification documents of qualified materials.

(Figure 8: Inspection of air ducts in purification air conditioning system)

3.11. The inspection door shall be flat, flexible to open and close, and tightly closed

Sealing measures shall be taken at its connection with the air duct or outside the air handling room, and there shall be no obvious leakage. The sealing gasket of the air duct inspection door of the purification air conditioning system should be made of civilian sealing tape or soft rubber strip. 

Inspection quantity: 20% shall be inspected by quantity, and shall not be less than 1.

Inspection method: Observation inspection.

3.12. The acceptance of the air outlet is based on the outer diameter of the neck and the outer length

The allowable deviation value of the size should comply with the provisions of the table. The outer decorative surface of the air outlet should be flat, the distribution of the blades or diFFUser rings should be uniform, the color should be consistent, and there should be no obvious scratches and indentations; the adjustment device should rotate flexibly and reliably, and there should be no obvious free looseness after positioning.

Inspection quantity: 5% of the category and batch shall be randomly inspected, and shall not be less than 1.

Inspection method: measurement, observation inspection, verification of qualified material certification documents and manual inspection.

Allowable deviation of air outlet size (mm)