Technical performance of drainage engineering valves

                  Column:Technical article Time:2019-10-31
                  The strength of the valve is the ability of the valve to withstand medium pressure.Valves are mechanical products under internal pressure and must have sufficient strength and stiffness to ensure long-term use without breaking or deformation.

                  01 strength performance

                  The strength of the valve is the ability of the valve to withstand medium pressure.Valves are mechanical products under internal pressure and must have sufficient strength and stiffness to ensure long-term use without breaking or deformation.

                  02 sealing performance

                  Valve sealing performance refers to the valve sealing parts to prevent the ability of media leakage, it is the most important technical performance index of the valve.The sealing part of the valve has three places: the contact place between the opening and closing parts and the sealing surface of the valve seat;Packing and stem and packing box;Where valve body meets bonnet.One of the previous leaks is called an internal leak, which is often referred to as a loose closure, which will affect the valve's ability to cut off the medium.For the cut-off valve class, internal leakage is not allowed.The last two leaks are called external leaks, that is, media leakage from the valve to the valve.Leakage will cause material loss, pollution of the environment, serious will also cause accidents.For flammable, explosive, toxic or radioactive medium, external leakage is not allowed, so the valve must have a reliable sealing performance.

                  03 flow performance

                  Media flow through the valve will produce pressure loss (that is, the valve before and after the pressure difference), that is, the valve has a certain resistance to the flow of medium, medium to overcome the resistance of the valve will consume a certain amount of energy.From the consideration of energy conservation, when designing and manufacturing valves, the valve should be as far as possible to reduce the resistance of the flow medium.

                  04 performance

                  Operating sensitivity and reliability this refers to the sensitivity of the valve to respond to changes in the medium parameters.For throttling valve, pressure reducing valve, regulating valve used to adjust the medium parameters of the valve and safety valve, traps and other valves with specific functions, the functional sensitivity and reliability is very important.

                  05 technical performance index

                  Opening and closing force and torque refer to the force or torque that must be applied to open or close the valve.Close the valve, the need to make the open-close part and send a form a seal between the two sealing surface pressure, but also overcome between stem and packing, the valve stem and between threads of the nut, valve rod end bearing friction and other parts of the friction force, and therefore must exert closing force and close moment, in the process of opening and closing, the valve is required for opening and closing force and the open-close torque changes, its maximum is in the closed end transient or open the initial transient.Valve shall be designed and manufactured to reduce its closing force and closing torque.

                  Opening and closing speed is indicated by the time required for the valve to complete an opening or closing operation.Generally, there are no strict requirements on the opening and closing speed of the valve, but some working conditions have special requirements on the opening and closing speed, such as some requirements for quick opening and closing to prevent accidents, and some requirements for slow closing to prevent water hammer, etc., which should be considered when selecting the valve type.Valve with temperature less than t and temperature less than 120℃.

                  06 Valve identification paint


                  1. The valve products shall be identified and painted according to the materials of the valve body. The colors shall be as follows: gray cast iron, malleable cast iron, carbon steel, acid-resistant steel and stainless steel alloy steel


                  Note :(1) acid-resistant steel and stainless steel are not allowed to be painted


                  (2) copper alloy without paint


                  2, in order to show the valve product sealing surface material, should be in the transmission hand wheel, handle, plate hand to identify paint, its color according to the table below.


                  Sealing surface material copper alloy babbitt acid-resistant steel stainless steel nitriding steel boronizing steel hard alloy monel alloy plastic rubber cast iron identification paint color bright red light yellow sky blue sky blue deep yellow purple red medium green black


                  Note :(1) when sealing surface materials of valve seat and opening and closing parts are different, paint according to low-hardness materials.


                  (2) check valve, coated on top of cover: safety valve, pressure reducing valve, steam trap, coated on bonnet or bonnet.


                  3. The paint color of the transmission mechanism shall be as follows:


                  (1) electric device: general type medium gray, three-in-one (outdoor, explosion-proof, anticorrosive) type final blue.


                  (2) pneumatic, hydraulic, gear transmission and other transmission mechanism, the same product color.


                  07 general principles


                  The valve used on water supply pipeline is generally selected according to the following principles:


                  1, the pipe diameter is not more than 50mm, should use the globe valve, pipe diameter is more than 50mm use gate valve, butterfly valve.


                  2, need to adjust the flow rate, water pressure timely use of regulating valve, globe valve.


                  3. If the water flow resistance is small (such as water suction pipe of the water pump), gate valve should be used.


                  4. Gate valve and butterfly valve shall be used on the pipe segment where water flow needs to flow in both directions, and globe valve shall not be used.


                  5, installation space is small parts should use butterfly valve, ball valve.


                  6, in the often open and closed section of the pipe, appropriate to use the globe valve.


                  7, the larger diameter water pump outlet pipe should use multi-function valve.


                  Valves shall be installed on the following parts of the water supply pipeline:


                  1. The water supply pipeline in residential area is on the introduction section of municipal water supply pipeline.


                  2. The node of the outdoor loop pipe network in the residential area shall be set according to the separation requirements.Circular section


                  Too long, should be set section valve.


                  3. Starting end of branch pipe connected from main water supply pipe in residential area or starting end of household pipe.


                  4. Household pipe, water meter and branch riser (bottom of riser, upper and lower end of vertical ring pipe network riser).


                  5, the ring pipe network of the dry pipe, through the branch pipe network connection.


                  6. The indoor water supply pipeline shall be set at the beginning of the distribution pipe connected to the household and public toilet, and the distribution points on the distribution branch pipe shall be set at 3 or more.


                  7. The outlet pipe of the water pump and the suction pump of the self-filling water pump.


                  8. Inlet, outlet and discharge pipes of water tank.


                  9. Fill water pipes for equipment (such as heater, cooling tower, etc.).


                  10, sanitary appliances (such as large, urinal, washbasin, shower, etc.) with water pipes.


                  11. Some accessories, such as automatic exhaust valve, pressure relief valve, water hammer eliminator, pressure gauge, sprinkler, etc. Front and back of pressure reducing valve and backflow preventer, etc.


                  12. Drain valve should be set at the lowest place of the water supply network.


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