The Five Main Points Of The Valve

During the construction process, the quality of Valve installation will directly affect the normal operation in the future, so attention must be paid. So, how to install Valve? What are the key points of Valve installation? What are the taboos and precautions?

1. Direction and position

1. Many Valves are directional

For example, stop valves, throttle valves, pressure reducing valves, check valves, etc., if they are installed upside down, it will affect the use effect and life (such as throttle valves), or they will not work at all (such as pressure reducing valves), or even Hazard (e.g. non-return valve). Generally, Valve has a direction mark on the valve body. In case not

Yes, it should be correctly identified according to the working principle of the valve.

The valve cavity of the stop valve is asymmetrical from left to right, and the fluid should pass through the valve port from bottom to top, so that the fluid resistance is small (determined by the shape), and the opening is labor-saving (because the medium pressure is upward), and the medium does not press the packing after closing, which is convenient for maintenance. , This is the reason why the globe valve cannot be reversed. Other valves Doors also have their own characteristics.

2. The installation position of the valve must be convenient for operation

Even if the installation is temporarily difficult, it is necessary to consider the long-term work of the operator. It is best to align the Valve handwheel with the chest (generally 1.2 meters away from the operation floor), so that opening and closing the valve saves effort. The hand wheel of the landing valve should face upwards, not inclined, so as to avoid awkward operation. The valve of the wall machine and the equipment The door should also leave room for the operator to stand. It is necessary to avoid operations on the sky, especially acid-base, toxic media, etc., otherwise it is very unsafe.

Do not install the gate upside down (that is, the handwheel is downward), otherwise the medium will remain in the space of the bonnet for a long time, which is easy to corrode the valve stem, and is contraindicated by certain process requirements. It is extremely inconvenient to replace the packing at the same time. Do not install the rising stem gate valve underground, otherwise the exposed valve stem will be corroded due to moisture.

When installing the lift check valve, ensure that the valve disc is vertical so that the lift can be flexible. When installing the swing check valve, ensure that the pin shaft is horizontal so that the swing can be flexible. The pressure reducing valve should be installed upright on the horizontal pipeline, and should not be tilted in all directions.

2. Construction work

Care must be taken during installation and construction, and avoid hitting valves made of brittle materials.

1. Before installation

① Carefully check whether the models and specifications of all Valves meet the design requirements.

② (According to the Valve model and factory instructions, check whether they can be used under the required conditions, and do a water pressure or air pressure test if necessary.)

③In addition, check whether the packing is in good condition, whether the gland bolts have sufficient adjustment margin, and check whether the valve stem and disc are flexible, whether they are stuck or skewed.

④ (The sealing surface of the valve disc must be closed tightly. For valves connected by threads, the thread quality should be checked. Unqualified valves cannot be installed, and should be stacked or marked separately.)

⑤Remove the sundries in the valve.

2. Installation process

① When the valve is hoisted, the rope should not be tied to the handwheel or the valve stem, so as not to damage these parts, but should be tied to the flange.

②The pipeline connected to the valve must be cleaned.

③ Compressed air can be used to blow away iron oxide chips, mud sand, welding slag and other sundries. These sundries not only easily scratch the sealing surface of the valve, but also large particles of sundries (such as welding slag) can block small valves and make them ineffective.

④ When installing the screw valve, the sealing packing (line hemp plus aluminum oil or polytetrafluoroethylene raw material tape) should be wrapped on the pipe thread, and should not get into the valve, so as not to accumulate in the valve and affect the flow of the medium.

⑤ When installing the flange Valve, pay attention to tighten the bolts symmetrically and evenly. The valve flange and the pipe flange must be parallel, and the clearance is reasonable, so as to prevent the valve from generating excessive pressure or even cracking. Special attention should be paid to brittle materials and valves with low strength. Valves to be welded with pipes should be spot welded first, Then fully open the closing part, and then weld it dead.

3. Protection measures

Some valves must also have external protection, which is heat preservation and cold preservation. In the insulation layer, sometimes a hot steam pipeline is added. What kind of valve should be kept warm or cold, according to production requirements.

In principle, if the temperature of the medium in the valve is too low, which will affect the production efficiency or freeze the valve, it needs to be kept warm or even mixed with heat; when the valve is exposed, which is not good for production or causes frosting and other adverse phenomena, it needs to be kept cold. Insulation materials include asbestos, slag wool, glass wool, perlite, silicon Algae, vermiculite, etc.; cold insulation materials include cork, perlite, foam, plastic, etc.

4. Bypass and instrumentation

Some valves, in addition to the necessary protection facilities, also have bypass and instrumentation. Bypass installed. Easy trap maintenance. Other valves are also installed with bypass. Whether to install a bypass depends on the valve condition, importance and production requirements.

5. Packing replacement

①Stock Valve, some fillers are not working well, and some are inconsistent with the medium used, which requires replacement of fillers.

②Valve manufacturers cannot consider the use of thousands of different media. The stuffing box is always filled with ordinary packing, but when used, the packing must be compatible with the media.

③When replacing the packing, press it in circle by circle. The seams of each circle are preferably 45 degrees, and the joints between circles are 180 degrees. The height of the packing should consider the room for the gland to continue to be tightened, and now the lower part of the gland should be pressed to the appropriate depth of the packing chamber, which can generally be 10-20% of the total depth of the packing chamber. for want

For high valves, the seam angle is 30 degrees. The seams between circles are staggered by 120 degrees.

④ In addition to the above fillers, rubber O-rings can also be used according to specific conditions (natural rubber is resistant to weak alkalis below 60 degrees Celsius, NBR is resistant to oil crystals below 80 degrees Celsius, and fluororubber is resistant to various corrosive media below 150 degrees Celsius) Piece-stacked PTFE ring (resistant to strong corrosion below 200 degrees Celsius Corrosion medium) Nylon bowl ring (resistant to ammonia and alkali below 120 degrees Celsius) and other shaped fillers.

Outside the ordinary asbestos packing, wrap a layer of tetrafluoroethylene raw material tape, which can improve the sealing effect and reduce the electrochemical corrosion of the valve stem. When pressing the seasoning, turn the valve stem at the same time to keep the surrounding even and prevent it from being too dead. Tighten the gland with even force and it can be tilted.