Page 197 - Compression Machinery for Oil and Gas

186 SECTION II Types of Equipment

FIG. 5.3 Typical ported plate valve components. (Courtesy of Ariel Corporation.)

FIG. 5.4 Typical ring valve components. (Courtesy of Ariel Corporation.)

The individual ring design is as it sounds, a series of concentric individual
rings that form the seal element (Fig. 5.4).
The poppet design has each seal element being an individual “poppet” which
can look like a bullet or a mushroom. Each poppet has its own spring and acts
individually as there is no mechanism to force the poppets to open and close
together (Fig. 5.5).
The reed design has the seal element opening and closing parallel to the gas
flow through the valve as opposed to perpendicular to the flow as in the previous
three types (Fig. 5.6).

Dynamics
Fig. 5.7 represents a theoretical, one degree of freedom model of a valve. The
valve is normally held closed by a spring force and opens when the pressure
force on the valve plate (from differential pressure between up and downstream
volumes) overcomes the closing force. In the absence of a preload force, the
valve opens with any pressure differential, but with a preload force present,
a nominal pressure difference is required before the valve can open. The limits