Taboo 1

During winter construction, hydraulic pressure tests are conducted at negative temperatures.

Consequences: Because the pipe quickly freezes during the hydraulic pressure test, the pipe freezes.

Measures: Try to conduct a hydraulic pressure test before winter installation, and blow out the water after the pressure test. In particular, the water in the valve must be completely cleared, otherwise the valve will rust at best or freeze and crack at worst.

When the water pressure test of the project must be carried out in winter, the indoor temperature must be maintained at a positive temperature, and the water must be blown away after the pressure test.

Taboo 2

If the pipeline system is not flushed carefully before completion, the flow rate and speed cannot meet the pipeline flushing requirements. Even flushing is replaced by hydraulic strength test draining.

Consequences: The water quality does not meet the operating requirements of the pipeline system, which often results in reduced or blocked pipeline cross-section.

Measures: Use the maximum juice flow rate in the system or a water flow speed of not less than 3m/s for flushing. The discharge water color and transparency should be consistent with the color and transparency of the inlet water according to visual inspection.

Taboo 3

Sewage, rainwater and condensate pipes shall be concealed without being tested for water closure.

Consequences: Water leakage may occur and user losses may occur.

Measures: The closed water test work should be inspected and accepted strictly in accordance with the specifications. Concealed sewage, rainwater, condensate pipes, etc. buried underground, in suspended ceilings, between pipes, etc. must be ensured to be impervious to leaks.

Taboo 4

During the hydraulic strength test and tightness test of the pipeline system, only the pressure value and water level changes are observed, and leakage inspection is not enough.

Consequences: Leakage occurs after the pipeline system is in operation, affecting normal use.

Measures: When the pipeline system is tested in accordance with the design requirements and construction specifications, in addition to recording the pressure value or water level changes within the specified time, special attention should be paid to carefully checking whether there is any leakage problem.

Taboo 5

Butterfly valve flange uses ordinary valve flange.

Consequences: The size of the butterfly valve flange is different from that of the ordinary valve flange. Some flanges have a small inner diameter, while the butterfly valve has a large valve disc, causing the valve to fail to open or open hard, causing damage to the valve.

Measures: Process the flange plate according to the actual size of the butterfly valve flange.

Taboo 6

There are no reserved holes and embedded parts during the construction of the building structure, or the reserved holes are too small and the embedded parts are not marked.

Consequences: During the construction of heating and sanitation projects, the building structure is chiseled or even the stress-bearing steel bars are cut, which affects the safety performance of the building.

Measures: Carefully familiarize yourself with the construction drawings of the heating and sanitary engineering project, and proactively and conscientiously cooperate with the construction of the building structure to reserve holes and embedded parts according to the installation needs of pipes and supports and hangers. Specifically refer to the design requirements and construction specifications.

Taboo 7

When welding pipes, the staggered joints of the pipes after matching are not on the same center line, no gap is left for the matching, thick-walled pipes are not beveled, and the width and height of the weld do not meet the requirements of the construction specifications.

Consequences: The misalignment of the pipe joints directly affects the welding quality and visual quality. If there is no gap between the joints, no beveling of thick-walled pipes, and the width and height of the weld do not meet the requirements, the welding will not meet the strength requirements.

Measures: After welding the joints of the pipes, the pipes must not be misaligned and must be on a center line; gaps should be left at the joints; thick-walled pipes must be beveled. In addition, the width and height of the welding seam should be welded in accordance with the specifications.

Taboo 8

The pipelines are directly buried in frozen soil and untreated loose soil, and the spacing and location of pipeline buttresses are improper, and even dry-coded bricks are used.

Consequences: Due to unstable support, the pipeline was damaged during the tamping process of backfill soil, resulting in rework and repair.

Measures: Pipes must not be buried in frozen soil or untreated loose soil. The spacing between buttresses must comply with the requirements of the construction specifications. The support pads must be firm, especially the pipe interfaces, which should not bear shear force. Brick buttresses must be built with cement mortar to ensure integrity and firmness.

Taboo 9

The expansion bolts used to fix the pipe supports are of inferior material, the holes for installing the expansion bolts are too large, or the expansion bolts are installed on brick walls or even lightweight walls.

Consequences: The pipe supports are loose and the pipes are deformed or even fall off.

Measures: Qualified products must be selected for expansion bolts. If necessary, sampling should be carried out for test inspection. The hole diameter for installing expansion bolts should not be larger than the outer diameter of the expansion bolts by 2 mm. Expansion bolts should be used on concrete structures.

Taboo 10

The flange and gasket of the pipe connection are not strong enough, and the connecting bolts are short or thin in diameter. Heating pipes use rubber pads, cold water pipes use double-layer pads or bevel pads, and flange pads protrude into the pipes.

Consequences: The flange connection is not tight, or even damaged, causing leakage. The flange gasket protrudes into the pipe and increases flow resistance.

Measures: Pipe flanges and gaskets must meet the design working pressure requirements of the pipeline.

Rubber asbestos pads should be used for flange linings of heating and hot water supply pipes; rubber pads should be used for flange linings of water supply and drainage pipes.

The flange gasket must not protrude into the pipe, and its outer circle should reach the flange bolt hole. Bevel pads or several pads must not be placed in the middle of the flange. The diameter of the bolt connecting the flange should be less than 2 mm than the flange plate hole diameter. The length of the bolt rod protruding from the nut should be 1/2 of the nut thickness.