Valve is the most common equipment in chemical enterprises. It seems easy to install the valve, but if it is not carried out according to the relevant technology, it will cause safety accidents. Today, I would like to share some experience and knowledge about valve installation.
Water pressure test shall be carried out under negative temperature during winter construction.
Consequence: due to the rapid freezing in the pipe during the hydrostatic test, the pipe is frozen
Measures: the water pressure test shall be carried out before winter construction as far as possible, and the water shall be blown clean after the pressure test, especially the water in the valve must be cleaned, otherwise the valve will rust if it is light, and freeze crack if it is heavy.
During the water pressure test in winter, the project shall be carried out under the positive indoor temperature, and the water shall be blown clean after the pressure test.
The pipeline system is not washed carefully before completion, and the flow and speed cannot meet the requirements of pipeline flushing. It even uses the hydraulic strength test to drain water instead of flushing.
Consequence: if the water quality fails to meet the operation requirements of the pipeline system, the pipeline section will be reduced or blocked.
Measures: flush with the maximum designed juice flow or water flow rate not less than 3m / s in the system. The water color and transparency of the outlet shall be consistent with that of the inlet through visual inspection.
Sewage, rainwater and condensate pipes shall be concealed without closed water test.
Consequence: it may cause water leakage and user loss.
Measures: the closed water test shall be checked and accepted in strict accordance with the specifications. Underground laying, ceiling, pipe room and other concealed sewage, rainwater, condensate pipes, etc. shall be guaranteed not to leak.
During the hydraulic strength test and tightness test of the pipeline system, only the pressure value and water level change are observed, and the leakage inspection is not enough.
Consequence: leakage occurs after the operation of the pipeline system, 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 necessary to carefully check whether there is leakage.
Common valve flange is used for butterfly valve flange.
Consequence: the size of butterfly valve flange is different from that of common valve flange. Some of the inner diameter of the flange is small, while the valve disc of butterfly valve is large, which results in failure to open or hard opening and damages the valve.
Measures: the flange plate shall be processed according to the actual size of butterfly valve flange.
There are no reserved holes and embedded parts in the construction of the building structure, or the size of the reserved holes is too small and the embedded parts are not marked.
Consequence: in the construction of warm and sanitary engineering, chiseling the building structure, even cutting the stressed steel bars, affects the safety performance of the building.
Measures: be familiar with the construction drawings of the heating and sanitation project, actively and carefully cooperate with the construction of the building structure to reserve holes and embedded parts according to the needs of the installation of pipes and supports and hangers, and refer to the design requirements and construction specifications for details.
During pipeline welding, after butt joint, the staggered joint of pipe is not on a central line, no gap is left for butt joint, no groove is cut for thick wall pipe, and the width and height of weld do not meet the requirements of construction specifications.
Consequence: if the pipe is not in the same center line, it will directly affect the welding quality and appearance quality. No gap shall be left for butt joint, no groove shall be cut for thick wall pipe, and when the width and height of weld do not meet the requirements, the welding cannot meet the strength requirements.
Measures: after the butt joint of the welded pipe, the pipe shall not be staggered and shall be on a central line; the butt joint shall be provided with clearance; the thick wall pipe shall be beveled. In addition, the width and height of the weld shall be welded in accordance with the specification.
The pipeline is directly buried in frozen soil and untreated loose soil, and the spacing and position of pipeline buttresses are improper, even in the form of dry bricks.
Consequence: the pipeline is damaged in the process of backfill compaction due to unstable support, resulting in rework and repair.
Measures: the pipeline shall not be buried on frozen soil and untreated loose soil. The distance between buttresses shall meet the requirements of construction specifications, and the supporting pad shall be firm, especially at the pipeline interface, which shall not bear shear force. Brick buttresses shall be built with cement mortar to ensure integrity and firmness.
The material of the expansion bolt for fixing the pipe support is poor, the hole diameter for installing the expansion bolt is too large or the expansion bolt is installed on the brick wall or even the light wall.
Consequence: the pipe support is loose, the pipe is deformed or even falls off.
Measures: qualified products must be selected for expansion bolts. If necessary, samples shall be taken for test and inspection. The hole diameter for installing expansion bolts shall not be greater than 2mm of the outer diameter of expansion bolts. Expansion bolts shall be applied to concrete structures.
The strength of flange plate and gasket for pipeline connection is not enough, and the connecting bolt is short or the diameter is thin. Rubber pad shall be used for heat pipe, double-layer pad or bevel pad shall be used for cold water pipe, and flange pad shall protrude into the pipe.
Consequence: the flange connection is not tight, even damaged, and leakage occurs. When the flange gasket protrudes into the pipe, it will increase the flow resistance.
Measures: the flange plate and gasket used for the pipeline must meet the requirements of the design working pressure of the pipeline.
Rubber asbestos pad shall be used for flange gasket of heating and hot water supply pipes; rubber pad shall be used for flange gasket of water supply and drainage pipes.
The gasket of the flange shall not protrude into the pipe, and the outer circle shall be suitable to the bolt hole of the flange. No inclined pad or several pads shall be placed in the middle of the flange. The diameter of the bolt connecting the flange shall be less than 2mm than the flange hole diameter, and the length of the protruding nut of the bolt rod shall be 1 / 2 of the nut thickness.
Post time: Nov-27-2019