Search results
Results From The WOW.Com Content Network
A separate actuator on the piping releases pressure in the line if it crosses a threshold. This releases the pressure on the back of the seal, causing the valve to open. The essential parts of a PORV are a pilot valve (or control pilot), a main valve, a pilot tube, the dome, a disc or piston, and a seat. The volume above the piston is called ...
The most common diaphragm valves use pneumatic actuators; in this type of valve, air pressure is applied through a pilot valve into the actuator which in turn raises the diaphragm and opens the valve. This type of valve is one of the more common valves used in operations where valve speed is a necessity.
The upper part of the valve stem, within the rocker box, is lubricated by oil. If this oil travels unchecked along the valve stem, engine HC emissions will become excessive. To control this, an elastomeric seal is fitted over the top of the valve guide. These may wear or stiffen with age, so are usually replaced whenever valves are removed for ...
While there are multiple design variants, the following is a detailed breakdown of a typical pilot-operated solenoid valve. They may use metal seals or rubber seals, and may also have electrical interfaces to allow for easy control. The diagram to the right shows the design of a basic valve, controlling the flow of water in this example.
The valve is controlled by an external, normally closed pilot valve. The pilot will be set to the desired set point of the system, with a sense line that runs up stream of the valve. When the upstream process conditions start to exceed the pilot set point, the valve begins to open and relieve the excess pressure until the correct pressure is ...
Pilot valves are useful because they allow a small and easily operated feed to control a much higher pressure or higher flow feed, which would otherwise require a much larger force to operate; indeed, this is even useful when a solenoid is used to operate the valve. Pilot valves are often used in critical applications (e.g., emergency and SIS ...
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
The valve's body is the outer casing of most or all of the valve that contains the internal parts or trim. The bonnet is the part of the encasing through which the stem (see below) passes and that forms a guide and seal for the stem. The bonnet typically screws into or is bolted to the valve body.