Valve applicator

Solenoid Valves The electric solenoid valve has tw o output states. Wlien sufficient electric current is supplied to the coil, an internal armature moves against a spring to an extreme position. This motion causes an attached pneumatic or hvdraiilic valve to operate. Wlien current is removed, the spring returns the armature and the attached solenoid valve to the deenergized position. An intermediate pilot stage is sometimes used when additional force is required to operate the main solenoid valve. Generallv, solenoid valves are used to pressurize or vent the actuator casing for on/off control-valve application and safetv shutdown applications. 

Valve Application Technology Functional requirements and the properties of the controlled fluid determine which valve and actuator types are best for a specific apphcation. If demands are modest and no unique valve features are required, the valve-design style selection may be determined solely by cost. If so, general-purpose globe or angle valves provide exceptional value, especially in sizes less than 3-inch NFS and hence are very popular. Beyond type selection, there are many other valve specifications that must be determined properly in order to ultimately yield-improved process control. 

A magnetic field due to an electric current can be turned on and off simply by turning the current on and off. A piece of iron attached to the end of a spring having the other end fixed can be moved with a magnetic field and returned to its initial position by the spring. The iron piece can then be used to actuate a switch or move a lever on a valve. Applications of this principle include electrically controlled valves in a washing machine and an electrically controlled switch for the starter in an automobile. 

Figure 10-14 Guidelines for control valve applications. (From Fisher Controls, 1987.)...

For single safety valve applications on cases other than fire no change. 

Decreased maintenance and noncontamination of the fluid stream with lubricants are cited as additional advantages. The valve is cheaper and easier to make than other type valves, and it is easier to obtain a tighter seal with a sphere than with other shapes. Manufacturers have estimated that the ball valve is suitable for one out of five present valve applications. 

The primary use for ball valves in the hydrocarbon processing industry is for valve applications under 400°F and pressures less than 4,000 psi, although with graphite seats they could be operated at temperatures as high as 1,000°F. 

Petrochemical plant engineers seem to be accepting ball valve applications at a much greater rate than oil refiners or gas processing plant operators. The fire hazard in process areas seems to be the deciding factor. 

R. Kiraly, R. Yozu, D. Hillegass, H. Harasaki, S. Murabayashi, J. Snow, Y. Nose, Hexsyn trileaflet valve—application to temporary blood pumps, Artif. Organs 6 (1982) 190-197. 

Most instruments and control devices are of a standardized off-the-shelf design, which complies with one or more national standards. In certain cases, for instance flow measurement orifice plates or control valves, application calculations are necessary, but these are in general in a standardized format. Loop diagrams also tend to follow various standard formats, according to application. In summary, most of this work can be handled in a systematic way, leaning heavily on databanks of item design data and application software. 

PAFRA Ball Valve Applicators (or Similar Ball Valves from Other Suppliers)... 

Suppliers of ball valve applicators Besides Paffa, UK (Fig. 77), we may mention Robatech, Switzerland, and Valeo, USA. 

Figure 77 Example of ball valve application for small jobs (by courtesy of PAFRA).

Having a diverse valve design for each of the three squib valve applications on the APIOOO minimises the simultaneous common mode failure of the three applications. The only disadvantages are that more spares have to be held for maintenance on three valve designs, although this is minimal given the difference in valve size and pressure rating between the three applications. 

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