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Diaphragm valve :
Diaphragm valves (or membrane valves) consists of a valve body with two or more ports, a diaphragm, and a "saddle" or seat upon which the diaphragm closes the valve. The valve body is commonly constructed from high grades of stainless steel, e.g. AISI 316L, inert polymers e.g. PVDF or higher alloys e.g. Ti, Hastelloy. The diaphragms are usually made out of inert polymers such as EPDM or PTFE, which can be sanitized with superheated water or sterilized with steam. This type of valve was developed in order to get a sanitary type of valve suitable for the pharmaceutical industry, and it is, if correctly installed, completely drainable unlike any other type of valve. Diaphragm valves also give the possibility to construct snug installations with few "dead-legs" in the pipes, which in turn simplifies the CIP -process of the system.
There consist two main categories of diaphragm valves, one type seals over a "saddle" and the other seals over a seat. The main difference is that a saddle-type valve has its two ports in line with each other on the opposite sides of the valve. Whereas the seat-type has the in/out ports located at a 90 degree angle from one another. The saddle type is the most common in process applications and the seat-type is commonly used as a tank bottom valve. Both types come with three ports and even more; however, when more than three ports are included, they require more than one diaphragm.
Diaphram valves can be manual or automated. Their application is generally as shut-off valves in process systems within the food&beverage, pharmaceutical and biotech industries. They are not well suited for regulating/controlling process flows, however seat diaphragm valves are being developed in this direction
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Applications Of Check Valves
Check valves are often used with some types of pumps. Piston-driven and diaphragm pumps such as metering pumps and pumps for chromatography commonly use inlet and outlet ball check valves. These valves often look like small cylinders attached to the pump head on the inlet and outlet lines. Many similar pump-like mechanisms for moving volumes of fluids around use check valves such as ball check valves.
Check valves are used in many fluid systems such as those in chemical, and power plants, and in many other industrial processes.
Check valves are also often used when multiple gases are mixed into one gas stream. A check valve is installed on each of the individual gas streams to prevent mixing of the gases in the original source. For example, if a fuel and an oxidizer are to be mixed, then check valves will normally be used on both the fuel and oxidizer sources to ensure that the original gas cylinders remain pure and therefore nonflammable.
Some types of irrigation sprinklers and drip irrigation emitters have small check valves built into them to keep the lines from draining when the system is shut off. |
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