Diaphragm Formulas and Definition of Terms

Glossary of Terms

HsMaximum Half Stroke: The maximum distance the diaphragm travels in either direction

from the clamping flange. The total stroke capability is twice the half-stroke capability.

BcCylinder Bore: The inside diameter of the housing with which the diaphragm will be in

contact.

DpPiston Diameter: The outside diameter of the moving component with which the diaphragm

is in contact.

HdDiaphragm Height: The overall height of the diaphragm in the as-molded shape.

WcConvolution Width: The width of the gap created by the difference in the piston diameter

and cylinder bore diameter.

RpPiston Radius: The radius on the diaphragm where it contacts the piston radius.

RfFlange Radius: The radius on the diaphragm where it contacts the hardware flange.

TfTolerance Factor: Diaphragm calculated height +2%.

SfStrength Factor: The average tensile strength of the fabric divided by two.

FtFlange Thickness: Cross section of a diaphragms outer diameter that is clamped or retained

by the hardware.

RPP Corporation 12 Ballard Way Lawrence, MA 01843 USA www.rppcorp.com TIPS-02

Rolling (Top-Hat) Diaphragm Formula for Height:Height = Hs + 1.57 Wc + Rp + Rf +Ft + Tf

Pre-Convoluted Diaphragm Formula for Height:Height = 0.5 (Hs + Wc + Rp + Rf + 2Ft)

Formula for Diaphragm Effective Area:

Effective Area = 0.785 (Bc + Dp)

2

2

Formula for Hardware Piston Skirt Length:

Piston Skirt =

*When Hs is in the direction with the diaphragm rolling onto the piston

(Hd + Hs*)

2

Formula for Diaphragm Working Pressure Capability:

Working Pressure =

Height

Effective Area

Height

Piston Skirt

Working Pressure

Sf

Wc

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