Bellofram Nomenclature
C" Style
Preconvoluted diaphragm. Convolution is molded into "as installed" shape.

Class
A description of the molded configuration of the diaphragm and its flange.

Convolution Width C
The radial clearance between the cylinder wall and piston wall of the hardware.

Convolution Bore, DC
Inside diameter of the cylinder into which the diaphragm will fit and function.
Note: This pertains to the hardware not the diaphragm.

Effective Area, AE
The effective pressure area of the system is defined by a diameter half-way between the hardware cylinder bore and piston diameters.
It may be calculated by the formula:

Effective area does not change regardless of stroke position as long as the diaphragm remains in a 180° convolution.

Flange
Outer portion of the diaphragm retained, supported or clamped by the hardware.

Flange Corner Radius
The blend radius between the sidewall and flange of the diaphragm.

Flash
A fine line of material projecting from the edge of a diaphragm, formed by the parting line or other openings in the mold. It usually cannot be completely removed by trimming.

Head
Area of the diaphragm retained against the piston head.

Head corner Radius
The blend radius between the head and side wall of the diaphragm.

Height, H or K
Height of the diaphragm (H for "Top Hat" or K for "C" style) is measured from bottom of flange to top of head (or convolution in "C" style). Height is measured from top of bead to top of head on Class 1A & 1B type of diaphragms (does not include height of bead).

Height/Stroke Limits
Height of diaphragm necessary to obtain a particular stroke. Formulas for determining this relationship are as follows:
     For "Top Hat" Style Diaphragms Require Height: H = SM +2RP + 1.56C + WF+Z
     For "C" Style Diaphragm: Required Height: K = 1/2 (SM + C + 2RP + 2WF)
     K - Height of "C" style BRD
     SM - Maximum half stroke; SA' up stroke; SB' down stroke.
     Z - Safety factor constant
     WF - Flange Thickness
     H - Height of "Top Hat" style BRD
     C - Convolution width
     RP - Piston corner radius
     RL - Cylinder corner radius

Cylinder

Identification
Diaphragms are identified by a Bellofram ABC (Approximate Bellofram Code) part number. See example below.

1 Class of diaphragm
2 Cylinder bore (DC) = 2.000" dia.
3 Piston diameter (DP) = 1.812" dia. (used only when non-standard DP is required and always placed in parentheses.)
4 Height, H (or K in "C" style) 1.00"
5 Bellofram's designation for sidewall thickness. (May also be a group of numbers.)
6 Bellofram's designation for fabric. (May also be a group of numbers or if no fabric put a dash in parentheses.)
7 Bellofram's designation for elastomer. (May also be a group of numbers.)
8 -1 Designates that the diaphragm has special trim.
Piston Diameter DP
Diameter of the piston as measured diametrically across the piston head.
Note: This pertains to the hardware, not the diaphragm.

Pressure Drop Across Diaphragm
The Bellofram Rolling Diaphragm is designed to have the higher pressure acting on the elastomer side, the pressure on the fabric side should always be less under all conditions of operations.

Sidewall Thickness, WSW
Thickness of the sidewall; that portion of the diaphragm between the head and flange, or between the head and breaded area.

Stroke
• Neutral Position (Neutral Plane) - The stroke capability of a diaphragm is usually calculated or specified using "neutral position" (neutral plane) as a basis. It is defined as that point in the stroke where the piston head is in the same plane as the clamping flange of the cylinder.
• Half Stroke - Many designs involve stroking the piston and diaphragm in only one direction from the neutral plane. "Half-stroke" is the term used to designate the stroke capability of the diaphragm under this condition. The half-stroke is designated as SB if it strokes below neutral plane. If a bonnet is used, the piston and diaphragm are allowed to stroke above the neutral plane, also. This portion of the diaphragm stroke capability is designated as SA stroke above neutral plane.
• Full Stroke (Total Stroke) - The full stroke capability of the diaphragm is the sum of the half strokes (SA + SB = ST). ST designates the total stroke.
Top Hat
Diaphragm molded in familiar "hat" shape that is formed into a rolling convolution when assembled into the hardware.

Trim
Head and flange contour and perforations, made according to customer's design requirements or Bellofram standards (if not specified by customer).