Precautions concerning the Installation of Valves

Precautions concerning the Installation of Valves

valve is a device which we use to control the direction, pressure and flow of a fluid in a fluid system, which can make the media such as the liquid, the gas and the powder in the pipe or equipment flow or cut off. In the construction process, the installation of the valve will directly affect the normal operation of the valve in the future. Today, we summarize some precautions concerning the installation of the valve.

1. The specifications and models of valves can not meet the design requirements. For example, the nominal pressure of the valve is less than the test pressure of the system. The gate valve is supposed to be used when the diameter of the water supply pipe is less than 50mm or equal to 50mm. The globe valve should be used for the hot water or heating supply pipe, and the butterfly valve is the best choice for the fire pump’s water absorption pipe.

If the specifications and models of valves can not meet the design requirements, valves may be unable to be properly opened or closed or the adjustment functions of valves may be affected.

To avoid the occurrences of the above situations, it is better for each valve user to get familiar with the application scope of each kind of valve and then choose the valve with the appropriate specification and model according to the design requirements of valves.

2. The main materials, equipment and products used in the construction lack the quality identification document or the product certification which can prove all the materials, equipment and products used comply with the current standard issued by the Chinese national or ministerial departments.

If the engineering project is unqualified, and there are some hidden dangers, the engineering project will not be able to be completed and must be reworked, which will cause the delays in construction as well as the increased labor and material investment.

Therefore, all the materials, equipment and products used in the construction must have the quality identification document or the product certification. The product’s name, model, specification, national quality standard code, date of production, manufacturer’s name and location, delivery inspection or delivery inspection code, etc. must be indicated clearly.
 
3. The necessary quality inspection of the valve is not carried out before the installation of the valve, which may trigger that the valve is unable to be opened and closed flexibly. The leakage of the media may also happen when the valve can not be completely closed. All these problems will cause the valve being unable to be operated properly. Thus, before the installation of the valve, the pressure-bearing capacity and air tightness of the valve should be tested. Ten percent of each batch of valves (but not less than one) with the same grade, size and type should be tested. However, for the valves used in the main pipelines for cutting off the media, each of them should have the pressure-bearing capacity and air tightness tests.
 
4. The valve is installed in the wrong direction. For example, the globe valve or the check valve is installed in the opposite direction of the direction marks on the valve body. This may bring the failure of the valve, the difficulty in opening, closing and repairing of the valve as well as the leakage of the media in the pipelines.

To avoid these situations, the valve should be installed in strict accordance with the valve installation instructions. For example, enough space must be left for the rotation of the butterfly valve’s hand wheel.


Precautions concerning the Installation of Valves

5. Pressure loss and flow capacity
Pressure loss and flow capacity essentially have the same parameters. The pressure loss is the measurement of the fluid resistance and is the difference between the valve’s inlet pressure and outlet pressure. With the given flow, pressure losses are determined by structures of butterfly valves, shapes of butterfly valves’ inner parts and surface roughness, and pressure losses are often indicated by the flow resistance coefficient. Flow capacity is related to maximum flow rates of valves with the given pressure difference, which is usually indicated by the flow coefficient.

We should consider making valves’ pressure loss smallest and flow capacity largest and we can take the general measures as the following.
①Valve bodies’ channels should not have reducing designs; the channel should not have protruding parts; butterfly valves’ plates should be smooth.
② Reduce values of flow channels’ surface roughness as much as possible.

③ The cross section of the whole channel should be the same or adopt smooth structures.

6. Driving torque
Driving modes of butterfly valves can be electric modes, pneumatic modes, hydraulic modes, etc.
Output torque of driving devices is determined by input torque required by butterfly valves; input torque of butterfly valves is affected by structures, degrees of sealing, types of media(water, oil, gas and powder), media’s pressure, operating frequency(low frequency and high frequency), control modes and other factors.

7. Media’s sensitiveness
Butterfly valves are devices that close and open or regulate piping systems which are used for transporting water, oil, gas, solid-liquid two-phase and gas-solid two-phase flow various media; therefore, the  sensitiveness of the  butterfly  valve’s sealed auxiliary to the medium is one of the important factors to be considered when we design butterfly valves; we should mainly consider selection of materials and structures when we design butterfly valves. We should choose rubber materials with good elasticity as seal rings for cut off butterfly valves whose media contain high dust content, or we can adopt multilayer metal seal rings with self-cleaning structures; sealed auxiliaries themselves can remove particles and other dirt when sealed auxiliaries have relative movements; we can use functions of purges and cleaning to ease dust pollution for sealed auxiliaries. 

Source: China Valves Manufacturer – Yaang Pipe Industry (www.steeljrv.com)

Related News

  • * 暂无相关文章
العربية简体中文NederlandsEnglishFrançaisDeutschItaliano한국어РусскийEspañolไทยTürkçe