With the scientific and technological progress, the production process automation used to control the fluid flow control valve has been widely used in various industries. For the thermal, chemical control systems, as the ultimate control of the process of media production targets of the quality and safety control valve, in the stable production, optimal control, maintenance and repair cost control plays an important role. In the regulation of valve applications, the calculation and selection is the prerequisite, installation and commissioning is the key, use and maintenance is the purpose. Regulating valve case of improper installation, or debugging is not good, not even come into the role of regulation, and even become a drag on the system.
Valve Installation
An installation of the basic principles of
Regulating valve installation should follow the relevant national standards, in accordance with design drawings and design documents provided strictly enforced. For example, the construction and installation, inspection and evaluation of quality standards, industrial automation instrument construction and acceptance specifications, electrical equipment installation engineering construction and acceptance of standards, etc.; to install the required equipment, auxiliary equipment and key material should be consistent with the relevant provisions of existing national standards.
2 pre-installation inspection
Regulating valve and accessories from the factory to the installation before, during transportation by carriers excited by the random vibration and handling is subject to a variety of shocks, as well as in transport and storage process, the environment temperature, humidity and other changes, which can result in the performance of control valve and accessories change. Therefore, it is necessary to carry out part of the performance of pre-installation testing.
Regulating valve pre-installation inspection includes the following elements: appearance, static characteristics, leakage volume, load the whole journey time, compressive strength, insulation performance, air tightness and sealing and so on, which will check for the previous five items. Of course, the test sites have certain requirements. For example: ambient temperature requires 10 ~ 35 ℃; air relative humidity of not more than 75%; the venue has sufficient space and adequate light or lighting conditions; around the local oscillator can not have sharp and strong magnetic field interference; power supply, gas supply meets the requirements.
3 Installation Notes
Regulating valve installation, the need to ensure safety, ensure the use of performance, ease of operation and maintenance, saving installation costs. Here's for the installation of these four points now need to pay attention to specific issues.
3.1 to ensure the safety of
1) To prevent leaks
The installation process does not allow control valve leakage generated. The use of process, if the filling-han, flange gaskets and other parts of the formation of cracks or micro-leakage may arise. If the fluid medium harsh operating conditions, such as high temperature, high pressure, corrosive fluid, then the damage will be aggravated and the greater the risk of leakage. There are many ways to prevent the leakage in the installation process, the choice of filling and sealing method of choice, choose a good valve sealing performance, are all factors that must be considered.
2) installation of relief valve
Any one pipeline design and installation, cut off the plot when they inevitably have high-pressure fluid, if significant accumulation of fluid in the potential energy should be installed on both sides of valve relief valve, so that the system cut off, the control valve in the residual energy of high-pressure fluid can be released, to protect the safety of personnel is conducive to the maintenance of control valve may also be considering the selection to limit traffic relief valve.
3) the safety of pipeline
Before installing the valve, all fittings and pipeline installation should be clean, purge, because pipes in the sand, scale, iron filings, etc. may damage the inner surface of valve, particularly in demanding sealing surface. When the system pressure fluctuation in severe cases, it is recommended to install a buffer in the pipeline facilities. If the emission of harmful gas or liquid fluid is then used to discharge fluid piping must be connected to a safe location, you can also connect to the security of a specific container, so that can protect workers from harm, while it will not cause environmental pollution.
3.2 ensure the use of performance
Install control valve, you should try to ensure that its performance is not affected. This effect would undermine the control valve selection taken into account various factors.
1) control valve on the upstream and downstream shut-off valve and bypass valve installation
Upstream and downstream shut-off valve and control valve length of straight pipe between the pipe should be considered fluid flow resistance and the impact of the state. The length of straight pipe length is conducive to flow through the shut-off valve after the stability of steady fluid flow can reduce the impact of turbulent flow and reduce noise; straight pipe lengths short, the fluid through the shut-off valve after the valve has not yet entered a stable, so that the noise increase large, but the short length of straight pipe pipe helps reduce resistance, improve the control valve pressure drop at both ends, so that the distortion of reduced flow characteristics are conducive to the stability control system operation. Therefore, we should balance, comprehensive consideration. In accordance with experience, usually the upstream side due 10D ~ 20D of straight pipe upstream and downstream side of a 3D ~ 5D of the straight pipe section (D is pipe diameter), if necessary, should be set up rectifier unit.
Valve demolition maintenance, the bypass valve can be used to operate the production process. When charged with the amount of traffic, with the regulating valve can not be properly adjusted, as a contingency measure, can also be used as a control valve bypass valve in parallel connection scheme, the process control. In order to reduce the cost of installing large-diameter hand wheel valve enforcement agency can replace the bypass valve to operate. Bypass valve installation should be easy to operate, with control valve and the upstream and downstream shut-off valve with integral regulator valve. Therefore, the control valve should be installed with shut-off valves and bypass valves matching considerations, and at the same time to complete construction and installation. Bypass valve nominal diameter and nominal diameter pipe the same pressure level pressure level is also consistent with the process.
2) The discharge valve, venting valves, valve installation of sewage
In order to facilitate control valve demolished, the demolition must be carried out before the valve before and after the pressure discharge valve, bleed valve should be installed in the control valve and the upstream and downstream between the shut-off valve. Venting valves and valves for the discharge of sewage flow in the entrainment of the non-condensable gases and condensate, if the installation was charged with the fluid is gas or steam, the condensate order to facilitate the discharge of sewage valve regulating valve installed in the appropriate minimum Department; when charged with fluid is a liquid, in order to facilitate the non-condensable gases, venting valve should install the highest office in the regulation valve.
3) regulating valve and pipe connections
Regulating valve and pipeline connection with threaded connections, flanged and welded connections distinction. Threaded connections for small-caliber valve installed, you must also install the activities of removable connector; flange connections of ordinary-type flange connection and two kinds of gripper-type connection, pipe connection flange nominal diameter should be adjusted valve diameter consistent pressure levels should also be level with the pressure regulating valve in line with the pipe flange vertical axis degree of allowable deviation of l °; try to avoid the use of welded connections. Regulating valve connection, should not link the emergence of new pipelines within the projections, for example, gaskets, welding seam should not have the inner bulge in the pipeline. At the same time, should pay attention to the flow of fluid within the valve body should be marked on the arrow in the same direction, in special circumstances may from time restriction.
4) The installation of the implementing agencies
In general, the implementing agencies directly connected with the regulating valve body, but the hydraulic implementing agencies, implementing agencies and other long-stroke and valve body separately, the installation of the implementing agencies should pay attention to the executing agency of the connecting rod and mechanical moving parts should be flexible, non - twist phenomena such as loose or card; rod length of appropriate, to ensure travel within the movement in the whole stable, flexible and reliable; hand wheel implementing bodies have two kinds of side-loading and top loading, the installation should be left room for maneuver, hand-wheel operation should be flexible , there is no stuck or reverse the phenomenon, there are hand-wheel rotation direction and the valve opening marked the relationship, limit devices should be adjusted to fit, has protective effects; hydraulic controller, implementing agencies should be lower than the installation, if the controller must be higher than the installation, the height difference should not exceed 1.0m, and shall remain in gas gathering pipelines to install exhaust valve, close to the controller, to install automatic shut-off valve.
5) The installation of the valve positioner
Valve positioner of the valve position detecting device and control valve stem or valve shaft directly connected, therefore, should ensure that feedback signals can be installed correctly in a timely manner to reflect valve position signal and change. Typically, the valve positioner and the control valve supporting supply, from factory to complete the connection between the two. When the production process control valve positioner needs to be added, should ensure the valve positioner valve position detecting device action is correct, reliable and flexible, mechanical feedback rod pivot gap should be as small as possible, valve positioner signal lines should be properly connected , gas pipelines and export pipelines source, enter the pipe should be marked; valve positioner valve position display signal should be conducive to the operation and maintenance personnel observations. ball valve Trunnion Mounted Ball Valve Floating Ball Valve Top Entry Ball Valve Three way ball valve V Type Ball Valve
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