Blow Molding & Hollow Plastic Products worked example

Blow Pressure Window with maximum approved blow pressure of 280 psi or bar: a worked example

What does the result look like when maximum approved blow pressure reaches 280 psi or bar? The full calculation is worked below with real intermediate numbers. a processor needs to check blow-pressure margin before adjusting pressure for a new resin, wall thickness, mold, or container geometry

The inputs for this scenario

  • Maximum approved blow pressure: 280 psi or bar (raised for this scenario; the documented default is 110)
  • Required forming pressure: 92 psi or bar (unchanged)
  • Reference pressure for margin: 110 psi or bar (unchanged)

Working through the calculation

  • Applying the documented formula (Available blow-pressure headroom = maximum approved blow pressure - required forming pressure) to the inputs above produces each figure below.
  • At this operating point the engine returns 171 % pressure margin for blow pressure margin, the number this scenario is built around.
  • At this operating point the engine returns 188 psi or bar for available blow-pressure headroom.
  • At this operating point the engine returns 280 psi or bar for maximum approved blow pressure.
  • At this operating point the engine returns 92 psi or bar for required forming pressure.

How this compares with the baseline

  • Against the tool's baseline example, where maximum approved blow pressure sits at 110 psi or bar and the headline result is 16.36 % pressure margin, this scenario comes in 944% above the baseline at 171 % pressure margin.
  • A figure at this level is achievable when maximum approved blow pressure is genuinely sustained, not just peaked for a shift. It is a static snapshot at one operating point and ignores transient pressure drop during inflation, hose losses, and temperature effects on material stiffness.

Results at a glance

  • Blow pressure margin: 171 % pressure margin (headline result)
  • Available blow-pressure headroom: 188 psi or bar
  • Maximum approved blow pressure: 280 psi or bar
  • Required forming pressure: 92 psi or bar

Run it with your numbers

  • Every input above is editable in the live Blow Pressure Window calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.