Definition and principle of Sanitary Diaphragm Valve
Diaphragm valve is a special form of shut-off valve, whose opening and closing parts are a diaphragm made of soft material, which separates the inner cavity of the valve body from the inner cavity of the valve cover. Diaphragm valve is actually just a "clamp" valve, an elastic, perturbed diaphragm, bolted to the compression part, which is operated by the valve stem and moves up and down. When the compression part rises, the diaphragm is lifted up to form a passage. When the compression part falls, the diaphragm is pressed on the weir of the valve body (if it is a weir valve) or on the bottom of the profile (if it is a straight-through type). Diaphragm valve is suitable for switching and throttling.
The working temperature of British standard diaphragm valve is usually limited by the materials used for diaphragm and valve body lining, and its working temperature range is about -50 to 175 degrees. The diaphragm valve has a simple structure and consists of only three main components: valve body, diaphragm and valve cover assembly. The valve is easy to disassemble and repair quickly, and the replacement of the diaphragm can be completed on site and in a short time. The separation of the operating mechanism and the medium passage makes the diaphragm valve not only suitable for food and medical and health industry production, but also for some difficult-to-transport and dangerous media. The application of more artificial synthetic rubber and engineering plastics, as well as a wider selection of valve body lining materials, has made diaphragm valves widely used in all fields of modern industry.
The national standard rubber-lined and fluorine-lined diaphragm valves are particularly suitable for ultra-pure media or heavily polluted, very viscous liquids, gases, corrosive or inert media due to their structural design. When combined with control equipment, the national standard rubber-lined and fluorine-lined diaphragm valves can replace other traditional control systems, especially for solid and easily contaminated inert media. The products are mainly used in biopharmaceutical, food, and industrial water treatment in power, chemical, electroplating, and other industries. They are also used in the production of wafers. Diaphragm valves are particularly suitable for transporting corrosive and viscous fluids, such as mud, food, medicine, and fibrous adhesives. Because the operating mechanism of the diaphragm valve is not exposed to the transported fluid in the pipeline, it is not polluting, does not require packing, and the valve stem packing part is unlikely to leak.
The principle of the British standard rubber-lined and fluorine-lined diaphragm valves is the reverse adjustment in the valve body. When the pressure at the inlet increases, the diameter is automatically reduced to reduce the change in flow, and vice versa. If the reverse connection is reversed, this adjustment system will not work. Moreover, the valve plate that plays a regulating role is directional, and the reverse pressure can even reduce or even close the flow. Since the diaphragm valve is installed for better heating, there is no problem of reverse installation. If it is reversed, it is a human error, and of course it will be corrected. The working principle is to change the flow resistance of the fluid flowing through the valve by changing the gap between the valve core and the valve seat (i.e. the opening), so as to achieve the purpose of regulating the flow. The diaphragm valve is equivalent to a throttling element with variable local resistance. For incompressible fluids, it can be obtained from the flow equation.

Kv is the valve coefficient of the direct-flow rubber-lined diaphragm valve. It is defined as: when the differential pressure before and after the direct-flow rubber-lined diaphragm valve is 1 bar (about 1kgf/cm2), the flow value (m3/h) flowing through the diaphragm valve. The valve coefficient of the direct-flow rubber-lined diaphragm valve when fully opened is equivalent to the flow capacity of an ordinary valve. If the opening of the balancing valve remains unchanged, the valve coefficient Kv remains unchanged, that is, the valve coefficient Kv is determined by the opening. By measuring the valve coefficient at different openings, the diaphragm valve can be used as a throttling element for quantitative flow regulation.

When debugging the diaphragm of the pipeline network, the pressure measuring valve of the debugged diaphragm valve is connected to the intelligent instrument with a hose. The instrument can display the flow value (and pressure drop value) flowing through the valve. After the human-machine dialogue with the instrument and the flow value required at the diaphragm valve is input into the instrument, the instrument calculates and analyzes and obtains the opening value of the valve when the pipeline system reaches hydraulic balance.
The diaphragm valve belongs to the category of regulating valves. The working principle of the internal thread diaphragm valve is to change the flow resistance of the fluid flowing through the valve by changing the gap between the valve core and the valve seat to achieve the purpose of regulating the flow.

1. The opening of the diaphragm valve should not be changed at will. After the pipe network system is installed and the test conditions are met, use the intelligent instrument to debug and adjust all the diaphragm valves, and lock the opening of each valve to achieve hydraulic working condition balance of the pipe network. During the normal operation of the pipe network system, the opening of the diaphragm valve should not be changed at will, especially the opening locking device should not be changed.

2. There is no need to install a stop valve. When repairing a certain loop, the diaphragm valve on the loop can be closed. At this time, the diaphragm valve plays the role of a stop valve to cut off the water flow, and returns to the original locked position after the repair is completed. Therefore, if a diaphragm valve is installed, there is no need to install a stop valve.
3. When adding (or canceling) a loop in the system, the system should be re-adjusted and adjusted. When adding (or canceling) a loop in the pipe network system, in addition to adding (or closing) the corresponding diaphragm valves, in principle, all newly installed diaphragm valves and diaphragm valves in the original system loops should be re-adjusted and adjusted (branch diaphragm valves in the original loop do not need to be readjusted). In air conditioning and heating systems, the hydraulic balance of the water circulation system as a means of transmitting and distributing energy is very important.