Pre installation inspection
There are many types, models, and specifications of commonly used valves. The type of valve to be used should be selected based on the purpose of the valve, the characteristics of the medium, maximum working pressure, maximum temperature, as well as the flow rate, flow rate of the medium or the nominal diameter of the pipeline.
Before installation, carefully check whether the models and specifications of all valves meet the design requirements. According to the valve model and factory manual, check if they can be applied under the required conditions, and if necessary, perform a water pressure or air pressure test. In addition, it is necessary to check whether the packing is intact, whether the gland bolts have sufficient adjustment allowance, and whether the valve stem and valve disc are flexible, and whether there is any jamming or tilting phenomenon. The sealing surface of the valve disc must be tightly closed, and for threaded valves, the quality of the threads should be checked. Unqualified valves cannot be installed and should be separately stacked or marked.
Precautions when installing valves
Open stem valves cannot be directly buried to prevent rust and corrosion of the valve stem. They can only be installed in covered trenches. Valves should be installed in locations that are convenient for operation, inspection, disassembly, maintenance, and operation. When handling valves, it is not allowed to throw them casually to avoid damage and deformation. When stacking, carbon steel valves should be separated from stainless steel valves and non-ferrous metal valves. When lifting valves, the steel wire rope should be tied to the connecting flange between the valve body and the valve cover, and should not be tied to the handwheel or valve stem to prevent damage to the valve stem and handwheel.
The installation position of valves should not hinder the disassembly, maintenance, and operation of equipment, pipelines, and valves themselves. The installation height should be convenient for operation and maintenance, and it is generally recommended to keep the valve operating handle 1-1.2m above the ground. For valves with more operations, when they must be installed more than 1.8m away from the operating surface, a fixed operating platform should be set up. When they must be installed above or below the operating surface, an extension rod should be set up or the valve stem should be horizontally installed, and a handwheel with a transmission device or a remote operating device should be installed. The angle between the axis of the valve transmission device should not exceed 30 °, and its joint should rotate flexibly, be easy to use during operation, and indicate accurately. Valves with thermal displacement should have compensation measures in the transmission device.
It is best to install the valve vertically upwards or the valve stem within the upper semicircle range in a horizontal pipeline, but the valve stem should not be installed downwards. The valve stem and handwheel on the vertical pipeline must be installed in the direction of the operation inspection line. When conditions permit, valves should be installed as centrally as possible for easy operation. Valves on tower area pipelines above 4 meters above ground level should not be installed outside the platform for ease of installation and operation.
For directional valves, the installation direction should be determined based on the flow direction of the medium in the pipeline. When installing a check valve, special attention must be paid to the flow direction of the medium to ensure that the valve disc can automatically open. In important situations, arrows should be clearly marked outside the valve body to indicate the direction of medium flow. For swing check valves, ensure that the rotating pivot of the insert plate is installed in a horizontal position. For lift check valves, it should be ensured that the centerline of the valve disc is perpendicular to the horizontal plane. When installing a shut-off valve, the medium should flow upwards from the bottom of the tray, commonly known as low inlet and high outlet. When installing cocks and gate valves, allow the medium to flow out from either end. |
