Poppet Seal Gasket O-ring Operating Life and Reliability Equations and Calculator

Related Resources: calculators

Poppet Seal Gasket O-ring Operating Life and Reliability Equations and Calculator

Application and Design Engineering
General Engineering and Design

Poppet Seal Gasket Oring Operating Life and Reliability Equations and Calculator

The primary failure mode of a seal is leakage, and the following equation is a approach developed for evaluating a poppet valve design.

Simple poppet Valve

Preview: Compression Spring Assembly Operating Life and Reliability Calculator

Poppet valve seal reliability equation:

Poppet valve seal reliability equation

Where:

λ_SE = Failure rate of seal, failures/million cycles
λ_SP,B = Base failure rate of seal, failures/million cycles
K₁ = Constant = 3.27 x 10^-4
P₁ = System pressure, lb/in²
P₂ = Standard atmospheric pressure or downstream pressure, lb/in²
Q_f = Allowable leakage rate under conditions of usage, in³/min
?_a = Absolute fluid viscosity, lb-min/in²
r_i = Inside radius of circular interface, in
r_o= Outside radius of circular interface, in
H = Conductance parameter (Meyer hardness M; contact pressure C; surface finish ƒ), in

The conductance parameter is a combination of Meyer hardness, contact pressure and surface finish per the following equation:

conductance parameter is a combination of Meyer hardness

Where:

M = Meyer hardness (or Young's modulus) for rubber and resilient materials, lbs/in²
C = Contact stress, lbs/in²
ƒ = Surface finish, in

In the case of an O-ring seal, the failure rate will increase as a function of time because of gradual hardening of the rubber material. A typical failure rate curve for an O-ring is shown below:

O-ring seal, the failure rate

References:

Handbook of Reliability Prediction Procedures for Machine Equipment