> Diaphragm Valve Manual Bonnet Selection

Tech Topic By Brad Gregg – Top Line Sales  Engineer – October 2018

Top Line manual bonnet assemblies follow the same time-tested and field verified performance from the start of product line inception in 1997. The standard features that are found in Top Line bonnet assemblies are often upgrades with additional cost from other valve manufacturers.

Standard features include:

  • Sanitary internals
  • FDA FKM O-ring sealed hand wheel and stem
  • Non-galling internal stem assembly
  • Stainless steel bonnet body with an electropolish exterior
  • Fully autoclaveable

Depending on the process and end-user requirements, there’s probably a Top Line bonnet assembly that will meet your need.

  1. A) Standard Open/Close applications:

If adjustability of either the compression or limiting of the open position of the diaphragm is not of concern, a non-adjustable type bonnet is the best and most economical option.

#12 bonnet

  • Stainless steel base with PPS thermoplastic hand wheel (valve sizes ½” – 2”).
  • PPS thermoplastic is very chemical and temperature resistant thermoplastic and can easily withstand wash down, autoclave, and sterilizing chemical wipe down protocols.
  • The stainless steel base is electropolished for both increased chemical resistance and for aesthetic purposes.

#60 bonnet

  • Stainless steel base with stainless steel hand wheel (valve sizes ½” – 2”).
  • The #60 bonnet assembly is essentially the same bonnet as the #12 bonnet, but with an electropolished hand wheel.
  • If diaphragm changes are regularly made after valve assembly installation, many times the PPS hand wheel can be broken due to the assembly being dropped.  The stainless steel hand wheel version is typically selected to prevent breakage and/or increased chemical resistance.

#9 bonnet

  • Stainless steel base with stainless steel hand wheel (valve sizes 2-1/2” – 4”).
  • The #09 bonnet is Top Line’s standard bonnet assembly for valve sizes over 2” and incorporates the same features and benefits as the #60 bonnet.

2) Open/Close with adjustable close stop:

If the prevention of over-compression of the diaphragm during valve closure in order to prolong diaphragm life is required, a bonnet assembly with an adjustable close stop should be used.  The close stop limits the amount of force that can be conveyed to the diaphragm, which prevents cold flow of the center diaphragm bead and premature failure of the elastomer backing cushion.

18A bonnet

  • Stainless steel base with PPS thermoplastic hand wheel (Compact valve sizes ¼” – ½”).
  • The #18A bonnet is Top Line’s standard bonnet for BioFlo II series compact/lab size valves and incorporates an ergonomically designed hand wheel.  The adjustable close stop can be set with a simple turn of a set screw within the bonnet assembly without any disassembly and preventing the possibility of loss of any small parts during bonnet adjustment.

#10 bonnet

  • Stainless steel base with stainless steel hand wheel (valve sizes ½” – 2”).
  • The #10 bonnet has the same features as the #18A bonnet, but with a durable stainless steel hand wheel as standard.

3) Open/Close with adjustable open stop:

If the requirement of the process system is to have some of the complete valve assemblies to remain in the semi-open position but can still be fully closed, an adjustable open stop bonnet should be used.  The adjustable open stop allows the user to manually set the proper open position of the valve during line balancing.

#15 bonnet

  • Stainless steel base with PPS thermoplastic hand wheel & gradient position indicator (valve sizes ½” – 2”).
  • Top Line’s #15 open stop bonnet assembly gives the user the flexibility to set the desired open position, lock it into place to allow the valve to be opened to the same position every time, and the ability to see relative valve position via the gradient indicator incorporated into the bonnet.

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