Valves are the most common equipment in heating companies, such as fully welded heating ball valves.
It seems easy to install valves, but if they are not implemented in accordance with the relevant technology, that will cause a safety accident. The next is to share some experience in valve installation with you.
Taboo 1
The water pressure test was carried out at a negative temperature in winter construction.
Consequences:
The tube freezes quickly due to the rapid freezing of the tube during the hydraulic pressure test.
Measures:
Try to carry out the hydraulic pressure test before the construction in winter, and blow the water after the pressure test. In particular, the water inside valves must be removed, otherwise the valve will rust and lightly crack.
The project must be carried out at a positive temperature in the room during the hydraulic pressure test in winter, and the water should be blown off after the test.
Taboo 2
Flushing is not serious before the completion of the piping system, and the flow rate and speed are not up to the pipeline flushing requirements. Even hydraulic pressure test leaks replace flushing.
Consequences:
Water quality does not meet the requirements of pipeline system operation, and often results in reduced or blocked pipe cross sections.
Measures:
Flush with the maximum design flow in the system or at a water flow rate should not less than 3 m/s.The discharge outlet water color, transparency and the inlet water color, transparency visual inspection is consistent as qualified.
Taboo 3
Sewage, rainwater, and condensate pipes are concealed without a closed water test.
Consequences:
It may cause water leakage and cause user losses.
Measures:
The closed water test work should be checked and accepted in strict accordance with the specifications. Concealed sewage, rainwater, and condensate pipes, such as buried, inside the ceiling, and between pipes, must be leak-proof.
Taboo 4
In the hydraulic pressure test and the tightness test of the pipeline system, only the pressure value and the water level change are observed, and the leakage inspection is insufficient.
Consequences:
Leakage occurs after the pipeline system is in operation, that will affect normal use.
Measures:
When the pipeline system is tested according to the design requirements and construction specifications, in addition to recording the pressure value or water level change within the specified time, it is especially necessary to carefully check whether there is leakage.
Taboo 5
Butterfly valve flanges use ordinary valve flanges.
Consequences:
The size of the butterfly valve flange and the ordinary valve flange are different. Some flanges have a small inner diameter, and the butterfly valve has a large valve flap, which causes the valve to be broken or hard to open.
Measures:
Machine the flange according to the actual size of the butterfly valve flange.
Taboo 6
There are no reserved holes and embedded parts in the construction of the building structure, or the reserved holes are small in size and the embedded parts are not marked.
Consequences:
During the construction of the heating and sanitation project, it affects the safety performance of the building.
Measures:
Familiar with the construction drawings of the heating and sanitation project carefully. According to the need of the installation of pipelines and hangers, take the initiative to cooperate with the construction structure to reserve holes and embedded parts, that refers to the design requirements and construction specifications.
Taboo 7
When the pipe is welded, the misalignment of the pipe after the joint is not on a center line, there is no gap in the counterpart, the thick-walled pipe does not shovel the groove, and the width and height of the weld do not meet the requirements of the construction code.
Consequences:
The misalignment of the pipe is not directly at the centerline, which directly affects the welding quality and the quality of the look and feel.There is no gap in the counterpart, the thick wall pipe does not shovel the bevel, and the welding width and height do not meet the requirements, resulting in the strength is not achieved.
Measures:
After welding the pipe counterparts, the pipes cannot be staggered, but on a center line; Counterparts should leave gaps; Thick-walled pipes need to bevelled.In addition, the width and height of the weld shall be welded in accordance with the requirements of the code.
Taboo 8
The pipeline is directly buried in frozen soil and untreated loose soil. The distance and location of the supporting pier of the pipeline are improper, even in the form of dry code bricks.
Consequence:
Due to the unstable support of the pipeline, the pipeline was damaged during the compaction of the backfill soil, resulting in rework and repair.
Measures:
The pipeline must not be buried in frozen soil and untreated loose soil. The distance between the pier should meet the requirements of the construction code, and support pad should be solid, especially at the joint of the pipe, it should not bear shear force.The brick pier should be built with cement mortar to ensure completeness and firmness.
Taboo 9
The expansion bolts used to fix the pipe bracket are of poor quality. The hole diameter of the expansion bolts is too large or the expansion bolts are installed on brick walls or even light walls.
Consequence:
The pipe support is loose, the pipe is deformed, or even falls off.
Measures:
Qualified products must be selected for the expansion bolts. If necessary, samples should be tested and checked. The diameter of the expansion bolts should not be greater than 2mm.Expansion bolts are applied to concrete structures.
Taboo 10
The flange and gasket of the pipe connection are not strong enough, and the connecting bolts are short or the diameter is small. Rubber gaskets are used for heat pipes.Double-layer gaskets or bevel pads are used for cold water pipes, Flange gaskets protrude into the pipes.
Consequence:
The flange connection is not tight, even damaged, and leakage occurs. Flange gaskets protrude into the tube and increase water resistance.
Measures:
The flanges and gaskets for pipelines must meet the requirements of the design working pressure of the pipelines. Flange gaskets for heating and hot water supply pipes should be made of rubber asbestos; Rubber gaskets should be used for the flange gasket of water supply and drainage pipes.
The gasket of the flange must not protrude into the pipe, and its outer circle is appropriate to the flange bolt hole.No bevel pad or several gaskets should be placed in the middle of the flange. The diameter of the bolt connecting the flange should be less than 2mm than the diameter of the flange hole. The length of the protruding nut of the bolt rod should be 1/2 of the thickness of the nut.
Taboo 11
Incorrect valve installation method.For example, the flow direction of water (steam) of the stop valve or check valve is opposite to the mark, the valve stem is installed downward, the horizontally installed check valve is installed vertically. there is no open or closed space for the handle of the open-rod gate valve or butterfly valve, and the valve stem of the concealed valve do not face the inspection door.
Consequences:
The valve fails, the switch is difficult to check and repair, and the valve stem often causes water leakage.
Measures:
Install valve strictly in accordance with the valve installation instructions. The open-rod gate valve leaves the valve stem with an extended opening height. The butterfly valve fully considers the turning space of the handle. Various valve stems cannot be lower than the horizontal position, even let alone downward.The concealed valve should not only be provided with an inspection door that meets the needs of valve opening and closing but also the valve stem should face the inspection door.
Taboo 12
The specifications and models of the installed valves do not meet the design requirements.
For example, the nominal pressure of the valve is less than the system test pressure; when the pipe diameter is less than or equal to 50mm, the gate valve is used; The dry and vertical pipes for hot water heating use globe valves;Fire pump suction pipe adopts butterfly valve.
Consequences:
Affects the normal opening and closing of the valve and adjusts resistance, pressure and other functions. It even caused valve damage during system operation and forced repair.
Measures:
Familiar with the application scope of various valves, and choose the specifications and models of the valves according to the design requirements. The nominal pressure of the valve should meet the requirements of the system test pressure.
Taboo 13
The necessary quality inspection is not performed as required before the valve is installed.
Consequences:
The valve switch is not flexible, the closure is not strict, and water leakage (steam) occurs during the system operation, which causes rework and repair, and even affects the normal water supply (steam).
Measures:
The pressure strength and tightness test should be performed before the valve is installed. For closed-circuit valves installed on the main pipe to play the role of cutting off, the strength and tightness tests should be performed one by one.
Taboo 14
The main material, equipment and products used in construction lack technical quality appraisal documents or product qualification certificates that meet the current standards issued by the state or the ministry.
Consequences:
The quality of the project is unqualified.there is a hidden danger of accidents. It cannot be delivered and used on schedule, and it must be reworked for repairs; Cause delays in the construction period and increased labor and material inputs.
Measures:
The main materials, equipment and products used in water supply, drainage and sanitary engineering shall have technical quality appraisal documents or product certifications that meet the current standards issued by the country or the ministry; their product names, models, specifications, national quality standards Code, date of manufacture, name and location of the manufacturer, inspection certificate or code of the manufactured product.
Taboo 15
Valve installed upside down
Consequence:
Stop valve, throttle valve, pressure reducing valve, check valve and other valves are directional. If it is installed upside down, the throttle will affect the use effect and life; the pressure reducing valve will not work at all, the check valve can even be dangerous.
Measures:
General valves have directional signs on the valve body; if not, they should be correctly identified according to the working principle of the valve.
Taboo 16
The manual valve opens and closes with excessive force
Consequences:
In some cases, the valve is damaged, and in another case, a safety accident is caused.
Measures:
The manual valve, its handwheel or handle, is designed according to ordinary manpower, considering the strength of the sealing surface and the necessary closing force. Therefore, you cannot use a long lever or a long wrench to move. Open and close the valve, the force should be stable and not impact.
Taboo 17
Valves are not installed properly in the high-temperature environment.
Consequences:
Cause a leak
Measures:
Because the high-temperature valve above 200 ℃ is at normal temperature during installation, after normal use, the temperature rises, the bolts are heated and expand, and the gap is increased, so they must be tightened again, otherwise, leakage is likely to occur.
Taboo 18
Cold weather does not drain in time.
Measures:
When the weather is cold, the water valve is closed for a long time, and the water behind the valve should be drained. Condensate should also be drained after the steam valve is stopped.
Taboo 19
Non-metallic valves have too much opening and closing force.
Measures:
Some non-metallic valves are hard and brittle, and some have low strength. During operation, the opening and closing force should not be too large, especially not to be vigorous. Also, pay attention to avoid object collision.
Taboo 20
The packing of the new valve is too tight.
Measures:
When the new valve is in use, do not press the packing too tightly, and do not leak as much as possible, so as not to pressure the valve stem too much, which will accelerate the wear and tear, and it will be difficult to open and close. The quality of valve installation directly affects its use.
Taboo 21
There is no operating space in the installation position.
Measures:
The valve installation position must be convenient for operation; even if the installation is temporarily difficult, the long-term work of the operator must be considered.
Taboo 22
Impact valve is made of brittle material.
Measures:
Care must be taken during installation and construction. Avoid hitting valves made of brittle materials. Inspect the valve, check the specifications and models for damage before installation, especially for the valve stem. You need to turn it a few times to see if it is skewed because it is the easiest to bump the valve stem during transportation.
Taboo 23
The valve is not insulated or cooled.
Measures: Some valves also need external protection facilities. This is insulation and cooling. In principle, where the temperature of the medium in the valve is too low, it will affect the production efficiency or freeze the valve. It will need heat preservation and even heat tracing; where the valve is exposed, it is unfavourable to production or causes frost formation and other undesirable phenomena, and it needs to keep cold.
Taboo 24
Steam trap is not bypassed.
Measures:
Some valves, in addition to necessary protection facilities, also have bypasses and meters. A bypass is installed for easy maintenance of the trap. Whether to install a bypass depends on the condition, importance and production requirements of the valve.
Taboo 25
Packing is not changed regularly.
Measures:
Some valves are not suitable for storage valves, and some do not match the use of media. This requires replacement of the packing. The valve faces thousands of different types of media. The stuffing box is always filled with ordinary packing, but when used, the packing must be adapted to the medium.