Diaphragm Classes

Diaphragm Classes Class 3C

Class 3C

The Class 3C diaphragm has characteristics similar to the Class 3 except the convolution is molded in. The information concerning flange design described for Class 3 also applies to Class 3C diaphragms.

Since this diaphragm is made in the “as-installed” shape with a permanent convolution it does not require inversion at assembly. It has a small centering force which may tend to return the diaphragm to its “as-molded” or neutral plane position. Because no inversion is required, only a flat retainer plate is needed to retain the head of the diaphragm to the piston.

The stroke of the Class 3C design is limited since deep molded convolutions are presently impractical to manufacture. It is recommended this design be used where differential pressures do not exceed 150 psi.

Class 3C


  1. Height tolerance is ±.015”
  2. This “V” rib is for diaphragm processing only and it may not appear on all diaphragms. It is not functional and need not be completely filled. Rib is normally on rubber side of diaphragm.
  3. Two “V” ribs may be used on beads that are .25 or larger in width.
  4. Number, size, spacing and location of “V” ribs may be modified to suit specific beads, or may be left off altogether.
  5. Trim tolerances Hole Diameter OD Trim Diameter Tolerances 0-1.00” ±.010” 1.01-3.00” ±.015” over 3.01” ±.020”
  6. Dimensions and tolerances pertain to Bellofram Rolling Diaphragms as manufactured and not to dimensions and tolerances of mating parts.
Request a Quote

Your Satisfaction is Our Focus!

Thank you for completing this form. Your interest in our products & services is highly valued, and we're excited to be considered for your needs. Rest assured, we will carefully review the information provided to offer a tailored solution. Our experts will work diligently to ensure you receive a timely and accurate quote. Should you have any questions or need further assistance, please feel free to contact us. We eagerly await the opportunity to serve you.