A Primer on Hygienic Diaphragm Valves

Processors needing to direct fluid quickly throughout their facility will frequently utilize diaphragm valves. That's because they are:

  • Versatile: suitable for use with a wide variety of fluids
  • Sanitary: easy to clean and maintain
  • Simple: contain few moving parts
  • Secure: feature a anti-leak seal with a tight shutoff

The only difficulty for processors is deciding which diaphragm valve style to select. This article will take a detailed look at these specialized valves primarily used in the biotechnology and pharmaceutical manufacturing industries for fluid flow on/off applications.

We will discuss:

  • How diaphragm valves work
  • What they're used for
  • What they're made of
  • Their advantages/disadvantages in particular applications
Diaphragm Valve - Family

What is a Diaphragm Valve?

Diaphragm valves have been around for a long time. In ancient Greece and Rome, individuals used this type of valve to control the water temperature and flow in hot baths. The diaphragm valve was modernized in the early 1900s by a South African mining engineer, P.K. Saunders, whose company continues to manufacture these types of valves to this day.

Diaphragm valves are perhaps one of the most configurable types on the market, well-suited for the highly sanitary processing needs of the biotechnology and pharmaceutical manufacturing industries.

This versatility is due to the nature of how these valves work and their construction.

As the illustration below shows, diaphragm valves consist of a valve body and a flexible elastomeric membrane that combine to control the flow of a fluid. To close the valve, the membrane seals against either a seat — in the case of a "full bore" or "straight-through" diaphragm valve — or a "weir".


In general, straight-through diaphragm valves are used in on/off applications, and weir-type diaphragm valves may be used for either fluid control or throttling applications. Note: in the biopharmaceutical manufacturing industry, weir-type valves are primarily used for on/off applications).

Diaphragm Valves Basics

In both types of diaphragm valves, the flexible diaphragm is connected to a support mechanism known as a compressor which is used to open and close the diaphragm.

  • When the valve is open, the diaphragm is lifted out of the fluid flow path, and the fluid has a smooth, streamlined flow passage.
  • When the valve is closed, the diaphragm is tightly sealed against either the seat or the weir.

Diaphragm valves usually come in what's known as a two-port configuration (called a 2/2-way diaphragm valve). They may also be found with three ports (3/2-way valves, also called t-valves) or more (the so-called multi-port or block valves). When more than three ports are used in the valve, more than one diaphragm seat is generally required; however, special dual actuators can handle more seats with one membrane.

A significant advantage of this type of valve is that only two parts of the valve come in contact with the fluid being processed:

  • The valve body
  • The membrane

All other working components — such as the compressor — are isolated from the fluid flow path.

This isolation makes these types of valves suitable for use with many kinds of fluids, as the diaphragm may be easily replaced or spec'd to be made from a material compatible with the fluid being processed.

For highly sanitary processing applications, diaphragm valves are ideal, as there is nothing in the fluid flow path, and the valve may be easily sanitized and sterilized. Indeed, regulatory agencies such as the USP (United States Pharmacopeia) and the EHEDG (European Hygienic Engineering Design Group) have certified some types of diaphragm membranes/valves for use in the sanitary processing industries, including biopharmaceutical manufacturing.

Diaphragm valves also have outstanding self-draining characteristics and can purge process fluids from the valve when mounted in either horizontal or vertical orientations. These characteristics make these valves well-suited for use in highly sanitary processing applications, where contamination from residual products or fluids may be an issue.

Features affecting drainability include the valve size and tube specification, the internal surface finish, the drain orientation, the surface tension/viscosity of the media, and the pipe run angle (generally recommended to be 2"-3").

The valve actuator (compressor) in diaphragm valves may be operated in several ways:

  • Simple diaphragm valves are operated by hand, with a lever or wheel used to move the compressor.
  • Automated diaphragm valves may use pneumatic, hydraulic, or electric actuators along with devices such as solenoids, limit switches, and positioners to control valve operation.
Diaphragm Valve Actuated Bonnet

Choosing a Diaphragm Valve

Diaphragm valves are made from various materials, not all of which are suitable for sanitary processing applications.

  • Body materials may be made from brass, steel (iron, carbon steel, stainless steel, alloys), and from various types of high-grade plastics (ABS, PVC, PP, PE, PVDF, and PFA).
  • For hygienic applications, 300-grade stainless steel (304, 316, 316L) and alloys such as AL-6XN® and Hastelloy® C-22® are preferred and may even be required per specifications.
  • Body liners may be rubber, fluorine plastic, or glass, or the valve body may be unlined.
  • Diaphragms are made from natural rubber, Buna, EPDM, silicone, or fluorine plastics (FEP, PTFE, or PFA).
  • Diaphragm valves feature a variety of pipe connection types, including butt welds, clamps, flanges, screw connectors, sockets, and spigot welds.
  • Diaphragm valves may be found in diameters ranging from 0.5" to 6". Note: Diaphragm valves used in non-hygienic industries may be found in diameters up to 14”.

Diaphragm Valve Advantages and Disadvantages

As noted previously, diaphragm valves are suitable for use with a wide variety of fluids, so this is a very versatile type of valve.

Advantages

  • Diaphragm valves are very easy to clean and maintain
  • They contain few moving parts
  • The diaphragm membrane is the only part of the valve that comes into contact with process fluids
  • They are easily sterilized
  • They feature a anti-leak seal with a tight shutoff
  • Repairs to the valve may be made without interrupting other pipeline components

Disadvantages

There are some notable limitations with the use of diaphragm valves.

  • Due to the relative fragility of the diaphragm membrane, diaphragm valves can only be used under moderate operating temperatures (-60°F to 450°F) and pressure (<300 psi)
  • The body of diaphragm valves must be made from corrosion-resistant materials

Hygienic Diaphragm Valves for Flow Control Available from CSI

CSI is proud to offer hygienic diaphragm valves from ITT Engineered Valves, a premier supplier of industrial valves for the mining, biopharmaceutical manufacturing, power, chemical, and other process-focused industries.

Diaphragm Valve - EnviZion

The EnviZion® valve is designed with the singular goal of reducing the overall cost of ownership. It requires no valve installation or diaphragm replacement tools and comes with no fasteners requiring regular re-torquing.

This design reduces diaphragm change times from an industry average of 23 minutes to only 3 minutes, a 90% reduction in maintenance time.

The EnviZion is engineered to improve cleanability by minimizing areas in the valve that can trap fluids and possibly lead to process contamination. In addition, the valve's active seating technology provides a reliable seal that does not degrade over time, unlike other diaphragm valve designs using passive seals.

The BioviZion® valve incorporates all of the EnviZion valve’s industry-leading technology into a small package designed specifically for the critical reliability need for sampling and low-flow bioprocess applications.

The BioviZion's stainless steel studs eliminate the small fasteners used in other compact diaphragm valves that are prone to galling and snapping.

Like the EnviZion valve, the BioviZion's thermal compensation system applies sealing force only where needed. These features combine for a more reliable and less costly valve to operate and maintain.

Diaphragm Valve - BioviZion
CSI offers a variety of 2-way valves.

Employing one of the company's three-valve body types (forged, wrought iron, or cast), these valves are suitable for a wide variety of applications. Incorporating valve bodies made with controlled sulfur 316L stainless steel, ITT’s 2-way valves meet the welding requirements needed in the high purity processing industries.

Diaphragm Valve - 2-Way Valve
CSI can supply several types of integrated block valves.

These valves combine multiple valves into a single body, reducing total installation time and validation costs. In addition, the technology optimizes drainability and hold-up volumes and improves cleanability.

Diaphragm Valves - Integrated Block Valves
Diaphragm Valves - Process Fabrication
Finally, CSI can provide custom process fabrications for diaphragm valves consisting of multiple 2-way valves designed to fit a specific application.

Compared to standard valves and fittings, these process fabrications will minimize hold-up volumes and improve drainability.

Next Steps

As we've shown in this article, diaphragm valves are one of the most versatile valve types used to control fluid flows, as processors may use them with a wide range of process materials. In addition, their design and ease in cleaning and sterilization make them particularly well-suited for use in highly sanitary process applications.

Not sure what type of diaphragm valve to use in your application? We're here to help. Call CSI at (417) 831-1411.

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A Guide to Choosing the Right Valve

In determining the correct type of valve to use for your application, there are a number of considerations to take into account. This guide will help you make the correct choice for your specific need.

A Guide to Choosing the Right Valve

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ABOUT CSI

Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.