The 26 key points of valve installation, 14 major taboos of common valve installation advantages and disadvantages of introduction

The 26 key points of valve installation, 14 major taboos of common valve installation advantages and disadvantages of introduction

In the construction process, the quality of valve installation directly affects the normal operation in the future, so we must pay attention to it. So, how do you install the valve? What are the key points of valve installation? What are the taboos and precautions?
5 key points of valve installation
1 Direction and position
Many valves are directional
For example, globe valve, throttle valve, pressure reducing valve, check valve, etc., if installed in reverse, it will affect the use effect and life (such as throttle valve), or does not work at all (such as pressure reducing valve), and even cause danger (such as check valve). General valves with directional markings on the body. If not, it should be correctly identified according to the principle of valve operation.
The valve chamber around the globe valve is asymmetrical, fluid to let it from the bottom to the top through the valve port, so the fluid resistance is small (determined by the shape), open labor-saving (due to the medium pressure up), closed after the medium pressure packing, easy to repair, this is why the globe valve can not install the truth. Other valves have their own characteristics.
Valve installation position must be easy to operate
Even if the installation is temporarily difficult, it is necessary to consider the long-term work of the operator. Better valve handwheel and chest alignment (generally 1.2 meters from the operating floor), so that the opening and closing of the valve is less effort. Floor valve handwheel should be facing up and not tilted to avoid awkward operation. The valve of the wall machine depends on the equipment, and the operator should also be left standing room.
To avoid the operation of the sky, especially acid and alkali, toxic media, otherwise it is not safe.
The gate should not be inverted (that is, the handwheel is down), otherwise the medium will be retained in the cover space for a long time, easy to corrode the stem, and for some process requirements taboo. It is extremely inconvenient to replace packing at the same time. Open STEM GATE VALVES, DO NOT INSTALL underground, otherwise due to damp corrosion of the exposed stem.
Lift check valve, installation to ensure that the valve disc vertical, so that the lift flexible. Swing check valve, when installed to ensure that the pin level, in order to swing flexible. The pressure reducing valve shall be installed upright on the horizontal pipe, and shall not tilt in any direction.
2 Construction Work
Installation and construction must be careful, do not hit the valve made of brittle materials.
Before the installation
All valve types and specifications shall be carefully checked for compliance with design requirements.
(CHECK whether they CAN BE USED IN THE REQUIRED conditions according to the valve model and factory instructions, and perform water or air pressure tests if necessary.)
In addition, it should also be checked whether the packing is intact, whether the gland bolt has enough adjustment allowance, and to check whether the stem and disc are sound, whether there is stuck and skew phenomenon.
The sealing surface of valve disc must be closed tightly, and the quality of thread should be checked for threaded valves. Unqualified valves shall NOT be INSTALLED and shall be separately stacked or marked.
Debris in the valve.
The installation process
When LIFTING THE VALVE, THE ROPE SHOULD NOT BE TIED TO THE HANDWHEEL OR STEM TO AVOID DAMAGE TO THESE PARTS. It SHOULD BE TIED TO THE flange.
The line to which the valve is connected must be cleaned.
Compressed air can be used to blow iron oxide filings, sand, welding slag and other sundries. These debris, not only easy to scratch the sealing surface of the valve, the large particles of debris (such as welding slag), but also can block the small valve, so that its failure.
When INSTALLING THE SCREW VALVE, THE SEALING PACKING (WIRE AND aluminum oil OR PTFE RAW material belt) should be wrapped on the pipe thread, do not get into the valve, so as to avoid the valve memory volume, affect the medium flow.
When installing flange valves, pay attention to tighten the bolts symmetrically and evenly. The valve flange and the pipe flange must be parallel, the clearance is reasonable, lest the valve produces excessive pressure, even crack. For brittle materials and not high strength of the valve, special attention should be paid. The valve to be welded with the pipe shall be spot welded first, then the closed part shall be fully opened, and then welded dead.
3 Protection Measures
Some valves must also have external protection, which is heat preservation and cold retention. The insulation layer is sometimes mixed with hot steam lines. What kind of valve should be heat or cold, according to the production requirements.
In principle, where the valve medium to reduce the temperature is too much, will affect the production efficiency or frozen valve, you need to keep warm, even mix heat; Where the valve is bare, adverse to production or cause frost and other adverse phenomena, you need to keep cold. Insulation materials are asbestos, slag wool, glass wool, perlite, diatomite, vermiculite, etc.; The cooling materials are cork, perlite, foam, plastic and so on.
4 Bypass and meter
Some valves, in addition to the necessary protection facilities, also have bypass and instrumentation. A bypass is installed. Easy to repair the trap. Other valves, also installed bypass. Bypass installation depends on valve condition, importance, and production requirements.
5 Packing replacement
Stock valve, some packing has not been good, and some do not conform to the use of media, which needs to replace the packing.
Valve factory can not consider the use of thousands of different types of media, packing box is always filled with ordinary root, but when used, must let the packing in the medium to adapt.
When replacing packing, press in round by round. Each ring seam to 45 degrees is appropriate, ring and ring open 180 degrees. The packing height should consider the leeway for the gland to continue pressing, and now it is necessary to let the lower part of the gland press the packing chamber to an appropriate depth, which can generally be 10-20% of the total depth of the packing chamber. For demanding valves, the joint Angle is 30 degrees. The seam between the ring and the ring is staggered 120 degrees.
In addition to the packing, but also according to the specific situation, the use of rubber O-ring (natural rubber resistant to 60 degrees Celsius weak alkali, butadiene rubber resistant to 80 degrees Celsius oil crystal, Fluorine rubber resistant to a variety of corrosive media below 150 degrees Celsius) three stacked polytetrafluoron ring (resistant to strong corrosive media below 200 degrees Celsius) nylon bowl ring (resistant to 120 degrees Celsius ammonia, alkali) and other forming filler.
A layer of TEflon raw material tape can improve the sealing effect and reduce the electrochemical corrosion of the valve stem. When pressing the seasoning, turn the stem at the same time to keep all around evenly, and prevent too dead, tighten the gland to force evenly, can not tilt.
Valve installation 14 major taboos
1
Contraindications: THE main materials, equipment and products used in construction lack technical quality appraisal documents or product qualification certificates in line with current national or ministerial standards.
Consequences: the quality of the project is not qualified, there are hidden accidents, can not be delivered on schedule, must be reworked repair; Cause project delay, manpower and material input increase.
Measures: the main materials, equipment and products used in water supply and drainage and heating and sanitation engineering should meet the current standards issued by the state or the ministry of technical quality appraisal documents or product qualification certificate; The product name, model, specification, national quality standard code, date of delivery, name and place of manufacturer, inspection certificate or code of delivery shall be indicated.
2
Do not: The valve installation before the necessary quality inspection according to the regulations.
Consequences: system operation valve switch is not flexible, close loosely and water leakage (steam) phenomenon, resulting in rework repair, and even affect the normal water supply (steam).
Measure: The valve should be tested for pressure strength and tightness before installation. The test shall select 10% of the quantity of each batch (same brand, same specification, same model), and not less than one. For the closed circuit valve installed on the main pipe to cut off the function, should be one by one for strength and tightness test. The VALVE strength and tightness test pressure shall comply with the “Construction Quality Acceptance Code for Building Water Supply, drainage and Heating Engineering” (GB 50242-2002).
3
Taboo: Installation valve specifications, models do not meet the design requirements. For example, the nominal pressure of the valve is less than the system test pressure; When the diameter of the feed water branch pipe is less than or equal to 50mm, the gate valve is used; Hot water heating dry, vertical pipe using stop valve; The suction pipe of the fire pump uses butterfly valve.
Consequence: Affect the valve normal opening and closing and adjust resistance, pressure and other functions. Even cause system operation, valve damage forced repair.
Measures: Familiar with the application of various types of valves, according to the design requirements to select the valve specifications and models. The nominal pressure of the valve shall meet the requirements of the system test pressure. According to the requirements of the construction code: water supply pipe diameter less than or equal to 50mm should be used cut-off valve; Gate valves should be used when pipe diameter is greater than 50mm.
The hot water heating dry, vertical control valve should use gate valve, fire pump suction pipe should not use butterfly valve.
4
Do not: Valve installation method is wrong. For example, the globe valve or check valve water (steam) flow direction is opposite to the sign, the stem is installed downward, the horizontal installation of the check valve is installed vertically, the rod gate valve or butterfly valve handle is not open or closed space, the valve stem is not facing the inspection door.
Consequences: valve failure, switch maintenance difficulties, valve stem down often cause water leakage.
Measures: Install the valve strictly according to the valve installation instructions, leave the valve stem to extend the opening height, the butterfly valve fully consider the rotation space of the handle, all kinds of valve stem can not be lower than the horizontal position, let alone downward. Hidden valve not only to set up to meet the valve opening and closing needs of the inspection door, at the same time the valve stem should be oriented to the inspection door.
5
Taboo: butterfly valve flange with ordinary valve flange.
Consequences: butterfly valve flange and ordinary valve flange size is different, some flange diameter is small, and the butterfly valve disc is large, resulting in can not be opened or hard to open the valve damage.
Measures: according to the actual size of butterfly valve flange flange processing flange.
6
Taboo: 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: WARM sanitation project construction, pick chisel building structure, even cut off the stress reinforcement, affect the building safety performance.
Measures: Be familiar with the construction drawings of heating and sanitation engineering carefully, and actively cooperate with the construction of the building structure to reserve holes and embedded parts according to the installation needs of pipelines and support hangers, with specific reference to the design requirements and construction specifications.
7
Contraindications: When welding the pipe, the wrong end of the pipe after the pair is not on the same Central Line, there is no gap on the pair, the thick wall pipe is not shovelled, and the width and height of the weld do not meet the requirements of the construction code.
Consequence: The wrong end of the pipe is not in a center line directly affects the quality of welding and visual quality. There is no gap between the two sides, the thick wall pipe is not shovelled, the width and height of the weld do not meet the requirements of the welding strength requirements.
Measures: After welding the pipe pair, the pipe should not be wrong, should be on a Central Line, the gap should be left on the pair, thick wall pipe should be shoVELled groove, in addition, the width and height of the weld seam should be welded according to the specification requirements.
8
Taboo: The pipeline is directly buried in the frozen soil and no treatment of the loose soil, pipeline pier spacing and improper location, or even the use of dry code brick form.
Consequence: Due to the unstable support, the pipe was damaged in the process of backfill earth tamping, resulting in rework repair.
Measures: THE PIPELINE SHALL NOT BE BURIED IN FROZEN SOIL or UNtreated loose soil, THE SPACING OF PIERS SHALL MEET the requirements of construction specifications, AND the SUPPORT CUSHION shall be firm, ESPECIALLY at the pipe interface, which shall not BEAR shear force. The brick piers should be built with cement mortar to ensure integrity and firmness.
9