(1) Preparatory work before assembly: Before assembly, valve parts need to remove the burrs formed by machining and welding residues, clean and cut fillers and gaskets.
(2) Cleaning of valve parts: The inner cavity of the valve installed as a fluid pipeline must be clean. Especially for valves used in nuclear power, medicine and food industries, in order to ensure the purity of the medium and avoid medium infection, the requirements for the cleanliness of the valve cavity are more stringent. Before assembling, the valve parts should be cleaned, and the chips, residual oil, coolant and burrs, welding slag and other dirt on the parts should be washed and cleaned. The valve is usually cleaned by spraying with alkaline water or hot water (kerosene can also be used for scrubbing) or cleaning in an ultrasonic cleaning machine. After the parts are ground and polished, the final cleaning is required. The final cleaning is usually to clean the sealing surface with gasoline, then dry it with compressed air and wipe it with a cloth.
(3) Preparation of fillers and gaskets: graphite fillers are widely used due to their corrosion resistance, good sealing performance and low friction coefficient. Packing and gaskets are used to prevent the medium from leaking through the valve stem and bonnet and the joint surface of the flange. These accessories must be prepared for cutting and receiving before the valve assembly.
(4) Valve assembly: The valve is usually assembled with the valve body as the reference part in the order and method specified by the process. The parts and components should be reviewed before assembling to avoid the parts that are not deburred and cleaned from entering the final assembly. During the assembly process, the parts should be handled with care to avoid bumps and scratches on the processed name. The movable parts of the valve (such as valve stem, bearing, etc.) should be coated with industrial grease. The bonnet and the flange in the valve body are mostly connected by bolts. When tightening the bolts, respond to the scale, interweave, and tighten repeatedly and evenly. Otherwise, the joint surface of the valve body and the bonnet will produce flow control valve due to uneven circumferential force. leakage. The handle used for tightening should not be too long to prevent the pre-tightening force from being too large and affecting the bolt strength. For valves with strict requirements for pre-tightening force, torque should be used to move the hand, and the bolts should be tightened according to the specified torque requirements. After the final assembly is completed, the holding mechanism should be rotated to check whether the movement of the valve opening and closing parts is maneuverable and whether there is any jamming. Whether the installation direction of the valve cover, bracket and other parts of the pressure reducing valve meets the requirements of the drawing, the valve can be tested only after all the reviews have passed.