Valves are the most common equipment in chemical companies. It seems easy to install valves, but if they are not implemented in accordance with the relevant technology, it will cause a safety accident. The next is to share with you some experience in valve installation.
#1 Taboo:
The water pressure test was carried out at a negative temperature in winter construction (such as fully welded valves).
Consequences: The tube freezes quickly due to the rapid freezing of the tube during the hydrostatic test.
Measures:
Try to carry out the hydrostatic test before the construction in winter, and blow the water after the pressure test. In particular, the water inside the fully-welded ball valve and other 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 hydrostatic test in winter, and the water should be blown off after the test.
#2 Taboo:
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 flushing with water pressure test leaks instead of flushing.
Consequences:
Water quality does not meet the requirements of pipeline system operation, and often results in reduced or blocked pipe sections.
Measures:
Flush with the maximum design flow in the system or at a water flow rate should not less than 3 m/s.
#3 Taboo:
Sewage, rainwater, and condensate pipes are concealed without a closed water test.
Consequences:
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, condensate pipes, buried underground, suspended ceilings, pipes must be ensured without leakage.
#4 Taboo:
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, affecting 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.
#5 Taboo:
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.
#6 Taboo:
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, the building structure is cut and even the stressed steel bars are cut, which affects the safety performance of the building.
Measures:
Conscientiously familiar with the construction drawings of the heating and sanitation project, and actively and conscientiously cooperate with the construction of the building structure to reserve the holes and embedded parts according to the needs of the installation of the pipeline and the supporting hangers, with specific reference to the design requirements and construction specifications.
#7 Taboo:
When the pipe is welded, the wrong port of the opposite pipe is not on a center line, no gap is left in the opposite port, and the thick-walled pipe does not shovel the groove. The width and height of the weld are not in conformity with the construction specifications.
Consequences:
The misalignment of the pipe does not directly affect the quality of the weld and the quality of the look and feel in a centerline. There is no gap in the opposite port, and the thick-walled pipe does not shovel the groove. If the width and height of the weld do not meet the requirements, the welding cannot meet the strength requirement.
Measures:
After welding the pipe to the opposite port opposite port, the pipe can not be staggered, it should be on a center line; the gap should be reserved; the thick wall pipe should be shovel. In addition, the width and height of the weld shall be welded in accordance with the specifications.
#8 Taboo:
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; the water supply branch pipe adopts a gate valve when the pipe diameter is less than or equal to 50 mm; the dry water and the riser of the hot water heating adopt a shut-off valve; and the fire pump suction pipe adopts a butterfly valve.
Consequences:
Affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even when the system is running, the valve is damaged and forced to repair.
Measures:
Familiar with the application range of various types of valves, and select the specifications and models of the valves according to the design requirements. The nominal pressure of the valve must meet the requirements of the system test pressure. According to the requirements of construction specifications: the water supply pipe diameter is less than or equal to 50mm should be used as a shut-off valve; when the pipe diameter is greater than 50mm, the gate valve should be used. The hot water heating dry and vertical control valve shall adopt the gate valve, and the fire pump suction pipe shall not adopt the butterfly valve.
#9 Taboo:
Do not perform the necessary quality inspection before installation of the valve.
Consequences:
The valve switch is not flexible during the operation of the system, the shutdown is not strict and the phenomenon of water leakage (steam) occurs, causing rework and repair, and even affecting the normal water supply (steam).
Measures:
Before the valve is installed, the compressive strength and tightness test should be done. The test shall be checked by 10% of each batch (same brand, same specification, same model) and not less than one. For closed-circuit valves installed on the main pipe, the strength and tightness tests shall be made one by one. The test strength of the valve strength and tightness shall be in accordance with the “Code for Acceptance of Construction Quality of Building Water Supply and Drainage and Heating Engineering” (GB 50242-2002).
#10 Taboo:
The main materials, equipment and products used in construction lack technical quality appraisal documents or product certificates that meet the current national or ministerial standards.
Consequences:
The quality of the project is unqualified, there are hidden dangers of accidents, and it cannot be delivered on time, and must be reworked and repaired; resulting in delays in construction period and increased investment in labor and materials.
Measures:
The main materials, equipment and products used in water supply and drainage and heating and sanitation projects shall have technical quality appraisal documents or product certificates that meet the current standards issued by the State or the Ministry; their product names, models, specifications and national quality standards shall be indicated. Code, date of manufacture, manufacturer’s name and location, factory product inspection certificate or code.
#11 Taboo:
Improper installation of valves in high temperature environments
Consequences: Causing leakage accidents
Measures:
High temperature valves above 200 °C, due to normal temperature during installation, and after normal use, the temperature rises, the bolts expand and the gap increases, so they must be tightened again, called “heat tight”, the operator should pay attention to this work, otherwise it will be easy to leak.
#12 Taboo:
Cold weather does not drain in time
Measures:
When the weather is cold, the water valve will be closed for a long time, and the water behind the valve should be removed. After the steam valve is stopped, the condensate should also be excluded. The bottom of the valve is like a plug, which can be opened to drain
#13 Taboo:
Non-metallic valves, too much opening and closing force
Measures:
Non-metallic valves, some hard and brittle, some have low strength, when operating, the opening and closing force can not be too large, especially not to make it strong and also pay attention to the object of bumping.
#14 Taboo:
The new valve packing pressure is too tight.
Measures:
When the new valve is used, the packing should not be pressed too tightly, so as not to leak, so as to avoid the valve stem being pressed too much, speeding up the wear and opening and closing.
The quality of the valve installation directly affects the use, so careful attention must be paid to the direction and position of the valve, valve construction operations, valve protection facilities, bypass and instrumentation, and valve packing replacement.
#15 Taboo:
There is no operation space in the installation position
Measures:
the position of the valve installation must be convenient for operation; even if the installation is temporarily difficult, it is necessary for the long-term work of the operator.
It is best to have the valve handwheel and the chest (usually 1.2 meters away from the operating floor), so that the opening and closing of the valve is more labor-saving. The floor valve hand wheel should be facing up, do not tilt, so as to avoid awkward operation.
The valve against the wall machine should also leave room for the operator to stand. It is necessary to avoid the operation of the sky, especially acid and alkali, toxic media, etc., otherwise it is very unsafe.
#16 Taboo:
Steam trap not installed bypass
Measures:
Some valves, in addition to the necessary protective facilities, must also have bypass and instrumentation. A bypass is installed to facilitate the inspection of the trap. Other valves are also installed with bypass. Whether to install the bypass depends on the condition of the valve, the importance and the requirements of the production.