Reciprocating Compressors – Allowable Plate Impact Velocity

Excessive valve plate impact velocity at the valve seat or at the valve guard contributes heavily to valve plate and valve spring failures.

One manufacturer’s operating experience has shown that, in order to eliminate valve plate or spring failures resulting from improper valve dynamics, the plate impact velocities in Figure 300-53 should not be exceeded.

Most vendors have computer programs that mathematically model valve element motion, aerodynamic drag coefficients, and flow through the valves during the compression cycle. These programs assess the valve dynamics and optimize the design in terms of lift, spring stiffness, and the damping for a specific application. The programs have a fairly good record of success, and continue to be improved with time. Figure 300-54 shows the results of a typical computer analysis (note the greatly reduced valve flutter).

If practical, before purchasing, have the vendor run a computer study for new machines, or for any valve upgrades planned for existing machines. It is highly recommended to discuss actual field experience with users of any particular type of valve proposed. Avoid valves which are not being used in similar services.

Results of Computer Study of Valve Dynamics

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