Quarter-turn valves

These valves are relatively inexpensive, quarter-turn valves. The seal is made by a rotating disc that remains in the flowstream subject to erosion while in the open position (Figure 15-4). Except in low-pressure service, they should not be used to provide a leak-tight seaL but they can be u.sed to throttle where a tight shut-off is not required. 

American Petroleum Institute (API), Std 607. Fire Test for Soft-Seated Quarter Turn Valves. Fourth Edition, API, Washington, D.C., 1993. 

Fire Test for Soft Seated Quarter Turn Valves, 1993. 

Fuel flow control in low-temperature cells is relatively simple. The control valves used are servomotor-driven quarter-turn valves, and the flow sensors can be the types used on gas furnaces, such as thermal dispersion type mass flow meters. 

For a period of time just after startup, the piping upstream of this compressor operated under a vacuum. This upstream piping was equipped with a set of double block and bleed valves to a scrubber that circulated diluted caustic soda. During this unusual startup configuration, moisture was sucked into the system and the wet chlorine completely dissolved the stainless steel ball within the 3-inch (7.6 cm) quarter-turn valves. 

Fire-tested valves should be used to isolate reactors, storage vessels, and pipelines. They can be used wherever EBVs are required. With the popularity of automated plants, quarter-turn valves are very popular and are used in most installations. The only common quarter-turn valves that are fire-tested are ball... 

Many of the fail-safe valves used in chemical processes are quarter-turn valves. Generally, ball valves with spring loaded actuators are recommended so that there is positive fail-safe movement in case of power or air failure. It may not be practical for very large valves to be spring loaded. These large valves should generally have a local air supply tank to cause them to fail to the fail-safe condition. 

A plug valve is a quarter-turn valve that controls flow by means of a cylindrical or tapered plug with a hole through the center, which can be positioned from open to closed by a 90° turn (Fig. 5.178). 

A ball valve is a quarter-turn valve in which a drilled ball rotates between seats, allowing straight-through flow in the open position and shutting off flow when the ball is rotated 90° and blocks the flow passage (Fig. 5.180). 

American Petroleum Institute (API). Standard 607, fire test for soft-seated quarter-turn valves. 6th ed. Washington, DC API 2010. 

During the time that the vessel is operating in this manner, it is necessary to have some other means of protecting the vessel from overpressure. One way of doing this is to have an operator stand by a block valve that can be opened so as to depressure the vessel to a vent or flare. If he receives instructions from the control room, or if he notices anything amiss, he will immediately open this valve. The block valve should not allow more than 3% pressure drop quarter-turn valves (e.g., plug or butterfly valve) should have a position indicator positively secured to the stem. 

An emergency shut-off valve is located on the lift truck near the tank to be used in the event of a fuel leak. The valve only requires a quarter turn to shut off the fuel in an emergency. If any worker smells natural gas in or around the engine area, there may be a leak in the CNG system. The quarter-turn valve should be turned to the off position and a trained and authorized mechanic should evaluate the truck. 

Convert quarter turn butterfly valves into ball valves. 

This is a quarter-turn on-off valve (Figure 15-1). A bore through the ball allows flow when it is lined up with the pipe and blocks flow when it... 

A valve that only requires one quarter turn to fully open or close. 

There must be a master control valve or switch accessible to and within 15 feet of the instructor s station for emergency cut-off of all gas cocks, compressed air valves, water, or electrical services accessible to students. Valves must completely shut-off with a one-quarter turn. This master control is in addition to the regular main gas supply cut-off, and the main supply cut-off must be shut down upon activation of the fire alarm system. 

Place in the flask 12 g of red phosphorus and 300 g of glacial acetic acid. Insert a thermometer and the delivery tube, and heat to about 100°. Chlorine is obtained from a cylinder which is connected first to a filter flask, which acts as a trap, and then to the disperser. Rubber tubing (red) of 5 mm in diameter is used to make the connections between the filter flask and the disperser. Open the main valve of the cylinder first, making about one quarter turn, and then, very slowly, open the needle valve. Adjust the latter so a fine stream of bubbles issues through the disperser. Pass chlorine into the mixture slowly at first and increase the flow gradually. The flame is adjusted so that the heat from the reaction is sufficient to keep the temperature at 105-110°. Chlorine is passed into the mixture until the contents of the flask have gained about 150 g (85 per cent of theory) in weight. The time required is about nine hours. After six hours it is necessary to reduce the flow of chlorine. 

An Isolation Valve (BV200) is required by NFPA 86 (sect. 4-2.4.1.1 and sect. 5-2.2). The purpose of the isolation valve is to provide a manual shutoff for maintenance and emergency conditions. Therefore, the valve must be located in a position where a hazardous condition will not impede access to the valve by plant personnel. A quarter-turn ball or butterfly valve with usual indication of valve position is required by NFPA 86 (sect. 4-2.4.1.2). The valve should include a locking feature so that the supply of fuel gas can be locked-out/tagged-out during maintenance operations. 

Another advantage cited for ball valves is their value for application in remote operation because they open and close so easily with only one quarter turn. With the trend to increased automatic control, this is an advantage indeed. 

They are as quick-opening as plug valves (in one quarter turn)... 

Between 1900 and 1930 instrumentation in the process industries consisted of a few field indicators and recorders. Stillmen and firemen would go from one indicator to another and control the process by making a quarter-turn adjustment to a globe valve. 

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