Seating design

Seat leakage is specified for conventional direct spring operated metal-to-metal seated valves by API RP 527. The important factor in understanding the allowable seat leak is that it is stated at 90% of set point. Therefore, unless special seat lapping is specified or soft seat designs used, a valve operating with a 10% differential between operating and set pressures may be expected to leak. 

RB-90 reverse buckling disk. Pressure on CONVEX side of disk and patented seating design puts compression loading on disk metal. 

Figure 7-8Q. Typical bolted type safety head assemblies with angular seat design. By permission, B.S. B. Safety Systems, Inc.

High pressure homogenizers are especially suitable for the emulsification processes in the food, pharmaceutical and bioprocess industries. A general disadvantage of these type of reactors is that there is no precise control over the cavitationally active volume and the magnitude of the pressure pulses that will be generated at the end of the cavitation events (cavitational intensity), unless the valve seat designs are substantially modified. 

Specific designs also affect how easily discs can be converted from metal- to soft-seated designs. 

Some manufacturers have special designs for particular applications, but high-performance valves extend the characteristics of the normal API/ASME/PED and EN requirements. Many are resilient-seated design. 

Optimum tightness up to set pressure with soft-seated designs... 

Particles (or traces thereof) between seat and disc - especially frequent in pump applications 1. Use a harder and different seat/disc combination. 2. Make sure a knife = edged seat arrangement is used. 3. Use easy to retrofit and compatible soft-seat design - preferably O-ring design. 4. Use bellow valves in case large particles are found or use a rupture disc at both valve inlet and outlet. 

Eliminate any seating design that would lead to or would transmit 3 to 4 cycles per second vibrations, since the resonant frequency of the human vertical trunk in the seated position is between 3 and 4 cycles per second. 

The design of automotive seat covers by the usage of predictive computer models not only provide comfort and durability, but also assist in the quick change in the design and knitted tube size. It adds on quality, provides ergonomic seat design and time saving. 

Use chairs which can be readily adjusted, and show employees how to use them seat height and slope, depth and width, contouring and cushioning and seat-back design all need to be considered. Different people prefer different seat designs. 

The 1989 Ford Fiesta was the first example of a unit seat in a volume car. The dual hardness foam was moulded directly in the textile eover, lined with a barrier film, with the fixtures already positioned for assembly within the ABS shell (see Fig. 4.11). The 1990 BMW 3-series featured bucket seats made in PP-GMT, in a process which included automated finishing and inline painting, all within a one-minute cycle. These seats however still use steel for the safety-critical parts of the structure the seat back and the seat sub-frame. In fact, new seat designs in production still owe more to develop-... 

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