The classification and material characteristics of valves are mostly because of valves. Remember the 14 taboos of installing valves

The classification and material characteristics of valves are mostly because of valves. Remember the 14 taboos of installing valves

There are many kinds of valves. With the continuous improvement of the technological process and performance of all kinds of complete sets of equipment, the types of valves are still increasing, and there are a variety of classification methods. Automatic valve: rely on the medium (liquid, gas, steam, etc.) and its own ability to operate the valve. Actuated valve: Valve operated by hand, electric, hydraulic or pneumatic means. Classification according to the structure principle is currently the most common domestic and international classification method, each type of valve can be subdivided into a variety of structural types according to the structural characteristics.
There are many kinds of valves. With the continuous improvement of the technological process and performance of all kinds of complete sets of equipment, the types of valves are still increasing, and there are a variety of classification methods.
1. Classified by automatic and drive
Automatic valve: rely on the medium (liquid, gas, steam, etc.) and its own ability to operate the valve. Such as safety valve, check valve, pressure reducing valve, steam trap, air trap, emergency cut-off valve, self-reliant pressure control valve, self-reliant temperature control valve, etc..
Actuated valve: Valve operated by hand, electric, hydraulic or pneumatic means. Such as gate valve, globe valve, throttle valve, butterfly valve, ball valve, plug valve, diaphragm valve, pneumatic film control valve, pneumatic piston control valve, etc.
2. Classified according to main technical parameters
A. Classification by nominal size (see Chapter 3 for the definition of nominal size)
Small diameter valve: nominal size ≤DN40 valve.
Medium diameter valve: nominal size DN50 ~ DN300 valve.
Large diameter valve: nominal size DN350 ~ DN1200 valve.
Large diameter valve: nominal size ≥DN1400 valve.
B. Classification by nominal pressure (see Chapter 3 for definition of nominal dimensions)
Vacuum valve: valve with working pressure below standard atmospheric pressure.
Low pressure valve: nominal pressure PN≤16 valve.
Medium pressure valve: nominal pressure PN25 ~ 63 valve.
High pressure valve: nominal pressure PN100 ~ 800 valve.
Ultra high pressure valve: nominal pressure PN≥1000 valve.
C, according to the medium working temperature classification
High temperature valve: T > 425℃ valve.
Medium temperature valve: 120℃ < T ≤425℃ valve.
Normal temperature valve: -29℃≤ T ≤120℃ valve.
Low temperature valve: -101℃≤ T < -29℃ valve.
** Temperature valve: T < -101℃ valve.
D, according to the valve body material classification
Non – metallic material valve: such as ceramic valve, FRP valve, plastic valve.
Metal material valve: such as copper alloy valve, aluminum alloy valve, titanium alloy valve, Monel alloy valve, Hastelloy valve, Inkel valve, cast iron valve, carbon steel valve, low alloy steel valve, high alloy steel valve, stainless steel valve.
Metal body lined valve: such as lead lined valve, plastic lined valve, rubber lined valve, enamel lined valve.
E. Classification by connection mode with pipelines (see Chapter 5 for specific connection mode)
Flanged valve: valve with flanged body and flanged pipe.
Threaded valve: valve with internal or external threads in body and threaded to pipe.
Welded valve: valve body with butt groove or socket welds, welded to pipe.
Clamp connection valve: a valve with a clamp on the body and a clamp connection to the pipe.
Sleeve connection valve: a valve connected to a pipe by a sleeve.
F. Classification according to operation mode
Manual valve: Valve operated by human hand with a handwheel, handle, lever, or sprocket. When larger torque is needed, worm gear, gear and other reduction devices can be used.
Electric valve: valve operated by motor, electromagnetic or other electrical device.
Hydraulic or pneumatic valve: valve operated by pressure of a liquid (water, oil, etc.) or air.
3. Classification according to structure principle
Classification according to the structure principle is currently the most common domestic and international classification method, mainly divided into gate valve, globe valve, butterfly valve, ball valve, plug valve, plunger valve, check valve, safety valve, pressure reducing valve, trap valve, diaphragm valve, throttle valve, regulating valve, multi-purpose valve, etc..
Each type of valve can be subdivided into a variety of structural types based on the structural characteristics. Examples of common valves are as follows:
Gate valve – a valve in which the opening and closing parts move perpendicular to the axis of the seat (medium flow).
Gate valves can be divided into wedge gate valves (single gate, double gate, elastic gate, etc.), flat gate valves, knife gate valves, etc. The specific classification and working principle will be described in the relevant chapters later. The gate valve structure is shown as follows:
Wedge gate valve
1, 2, 3, 4 Next page is mostly because of the valve, remember the 14 do not install valve most of the time because of the valve, remember 14 do not install valve. The pipeline system was not flushed carefully before completion, and the flow rate and speed could not meet the requirements of pipeline flushing. Even water pressure strength test drainage instead of flushing. Measures: use the system to set the maximum juice flow or water flow speed should not be less than 3m/s for washing. The color and transparency of discharge outlet should be consistent with that of inlet water visually.
Hydrostatic test was carried out under negative temperature during winter construction.
Consequence: due to the water pressure test tube quickly frozen, so that the tube frozen bad.
Measures: try to carry out water pressure test before winter application, and after pressure test, the water must be blown clean, especially the water in the valve must be perfect in the net, otherwise the valve will be frozen crack.
The water pressure test must be carried out in winter, and the water must be blown clean after the pressure test. When a hydrostatic test is not possible, compressed air may be used.
No-no 2
The pipeline system was not flushed carefully before completion, and the flow rate and speed could not meet the requirements of pipeline flushing. Even water pressure strength test drainage instead of flushing.
Consequence: water quality can not meet the requirements of pipeline system operation, often will cause pipeline section reduction or blockage.
Measures: use the system to set the maximum juice flow or water flow speed should not be less than 3m/s for washing. The color and transparency of discharge outlet should be consistent with that of inlet water visually.
No-no 3
Sewage, rainwater, condensate pipes do not do closed water test will be concealed.
Consequences: May cause water leakage and loss of users.
Measures: closed water test work should be strictly in accordance with the standard inspection acceptance. Underground buried, suspended ceiling, pipe and other hidden sewage, rainwater, condensed water pipe to ensure that no leakage.
Taboo 4
When the water pressure strength test and tightness test of the pipeline system, the pressure value and water level change should be observed, and the leakage inspection is not enough.
Consequence: Leakage occurred after the operation of the pipeline system, affecting the 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.
No-no 5
Butterfly valve flanges with ordinary valve flanges.
Consequences: butterfly valve flange and ordinary valve flange size is not the same, some flange diameter is small, and the butterfly valve disc is large, resulting in not open or hard to open the valve damage.
Measures: according to the actual size of the butterfly valve flange processing flange.
No-no 6
There are no reserved holes and embedded parts in the construction of the building structure, or the size of reserved holes is too small and the embedded parts are not marked.
Consequence: in the construction of heating and sanitation project, chisel the building structure, or even cut off the reinforced steel, affecting the safety performance of the building.
Measures: carefully familiar with the construction drawings of heating and sanitation engineering, according to the needs of pipeline and support hanger installation, take the initiative to seriously cooperate with the construction of reserved holes and embedded parts of the building structure, with specific reference to the design requirements and construction specifications.
No-no 7
When the pipe is welded, the wrong mouth of the opposite pipe is not on a Central Line, the opposite pipe does not leave gaps, the thick wall pipe does not shovel groove, and the width and height of the weld do not meet the requirements of the construction code.
Consequence: the pipe wrong mouth is not in a center line directly affects the welding quality and perception quality. There is no gap between the pair, the thick wall pipe does not shovel the groove, the width and height of the weld does not meet the requirements of welding strength requirements.
Measures: after welding pipe matching, the pipe should not be wrong mouth, should be on a center line, the counterpart should leave a gap, thick wall pipe to shovel groove, in addition, the width and height of the weld should be welded in accordance with the requirements of the specification.
Taboo 8
The pipe is directly buried in frozen soil and untreated loose soil, the distance and position of the pipe piers are improper, and even the form of dry code brick is adopted.
Consequence: The pipeline was damaged in the process of backfill compaction due to unstable support, resulting in rework and repair.
Measures: the pipeline shall not be buried in frozen soil and untreated loose soil, the pier spacing should meet the requirements of the construction code, the pad should be firm, especially the pipeline interface, should not bear shear force. Brick support pier to use cement mortar masonry, ensure integrity, firm.
No-no 9
The expansion bolts used to fix pipe supports are of poor quality, the holes of the expansion bolts are too large, or the expansion bolts are installed on brick walls or even lightweight walls.
Consequence: the pipe bracket loosens, the pipe deforms, even falls off.
Measures: The expansion bolt must be selected qualified products, and the sample test should be carried out if necessary. The aperture of the expansion bolt should not be larger than the outer diameter of the expansion bolt 2mm, and the expansion bolt should be used in the concrete structure.
No-no 10
Flange and gasket strength of pipeline connection is not enough, the connecting bolt is short or thin diameter. Rubber gaskets are used for heat pipes, asbestos gaskets are used for cold water pipes, and double gaskets or beveled gaskets are used with flange gaskets protruded into the pipe.
Consequences: flange joint is not tight, even damage, leakage phenomenon. The flange liner protrudes into the pipe and increases flow resistance.
Measures: flanges and gaskets for pipelines must meet the requirements of design working pressure of pipelines.
For flange gaskets of heating and hot water supply pipes, rubber asbestos gaskets should be used; Rubber gaskets should be used for flange gaskets of water supply and drainage pipes.
Flange gasket should not protrude into the pipe, its outer circle to the flange bolt hole is appropriate. No bevel pad or several gaskets shall be placed in the middle of the flange. The diameter of the bolt connecting the flange should be less than 2mm than the flange aperture, and the length of the bolt rod protrecting nut should be 1/2 of the nut thickness.
Taboo 11
Valve installation method is incorrect.
For example, stop valve or check valve water (steam) flow is opposite to the mark, the stem is installed downward, the check valve installed horizontally is installed vertically, there is no open or close space for the handle of the gate valve or butterfly valve, and the stem of the hidden valve is not facing the inspection door.
Consequences: valve failure, switch maintenance is difficult, valve stem down often cause water leakage.
Measures: strictly according to the valve installation instructions for installation, stem gate valve leave enough extension of the opening height, butterfly valve fully consider the handle rotation space, all kinds of valve stem can not be lower than the horizontal position, but not down. Concealed valve not only to meet the valve opening and closing requirements of the inspection door, at the same time the valve stem should be towards the inspection door.
Taboo 12
The specifications and models of 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; Hot water heating dry, riser using stop valve; Fire pump suction pipe adopts butterfly valve.
Consequences: affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even caused system operation, valve damage forced repair.
Measures: familiar with the application range of all kinds of valves, according to the requirements of the design of valve specifications and models. Nominal valve pressure should meet the requirements of system test pressure. According to the requirements of the construction code: water supply branch pipe diameter less than or equal to 50mm should be used by the globe valve; Gate valves should be used when pipe diameter is greater than 50mm. Hot water heating and drying, vertical control valve should be used gate valve, fire pump suction pipe should not use butterfly valve.
Taboo 13
Valves are not inspected as required before installation.
Consequence: during the operation of the system, the valve switch is not flexible, the valve is not closed strictly and water leakage (steam) occurs, resulting in rework and repair, and even affecting the normal water supply (steam).
Measures: before valve installation, pressure strength and tightness test should be done. The test should be randomly checked 10% of the quantity of each batch (same brand, same specification, same model), and not less than one.
The strength and tightness test should be done one by one for the closed valve which is installed on the main pipe and plays a cutting role. Valve strength and tightness test pressure should meet the requirements of “Code for Acceptance of Construction Quality of Building Water Supply and drainage and heating Engineering” (GB 50242-2002).
Taboo 14
The main materials, equipment and products used in construction lack of technical quality appraisal documents or product certificates in line with the current national or ministerial standards.
Consequences: The project quality is not qualified, there are potential accidents, can not be delivered for use on schedule, must be reworked repair; Cause time limit delay, labor and material input increase.
Measures: the main materials, equipment and products used in water supply and drainage and heating and sanitation projects should meet the technical quality appraisal documents or product certificates issued by the state or the ministry of current standards; The product name, model, specification, code of national quality standard, date of delivery, name and place of manufacturer, inspection certificate or code of delivery product shall be indicated.