• Inspection and installation of valves (part two)

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Inspection and installation of valves (part two)

  • Oct 12, 2018
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Installation precautions:
  • The impact from hefty items is unbearable to fragile valve body materials, which are mostly forged by iron.
  • Throwing is prohibited when carrying the valve, and it is neither hand wheel, nor valve stem, nor flange bolt hole but the valve body should be tied.
  • The valve should be installed in the most convenient place (definitely not in the underground) for operation, maintenance, and service. Inspection well is needed for valves on longitudinally submerged pipes and pipes in trench.
  • Ensure the intactness of screw thread, cover it with lead oil and tie it with hemp rope, or PTEF tape. When screwing, stabilize the position of the hexagonal valve body inserted on one end of the pipe by a wrench.
  • When installing flange valve, diagonally and evenly tighten the connecting bolt, so as to prevent off-tracking of the gasket, deformation and damage of the valve body.
  • Keep the valve closed during installation. For threaded valve clinging to wall, uninstall valve stem, clack and hand wheel before installing and rotating it. Whereas you should keep the valve opened during uninstallation.

installation of common valves

A gate valve, also known as a sluice valve, is a valve which opens and closes by gate, adjusts the medium's flow rate thru changing the cross section. It is mainly used for fluid media, with no specific requirement for direction in installation, aside from inversion.

A globe valve controls the opening and closing by disc. It regulates the flow rate of medium thru changing the space between the disc and valve body. The flow direction of medium must be taken into consideration when installing. The standard flow direction is flowing under the seat, inverse installation is forbidden.

A check valve, also known as a non-return valve, one-way valve, operates under the pressure difference caused by the upstream and downstream pressures, and in order to prevent adverse current, it normally allows fluid to flow through it in only one direction. According to the difference of structure, check valves can be divided into lift type (horizontal and vertical types), swing type and butterfly type. Like globe valve, it should not be installed inversely and the flow direction of fluid has to be considered.

A relief valve can automatically stabilize the outlet pressure by reducing inlet pressure to the needed outlet pressure, and consuming the energy of medium.
From the perspective of fluid mechanics, a relief valve is a restricting element with alterable local resistance, i.e., it can achieve the aim of reducing pressure by altering the throttling area, changing the flow velocity and the kinetic energy of fluid. After that, by controlling and regulating the system, it balances the force based on pressure and the spring force. Within a certain error range, the pressure remains stable.