Comparison: Diaphragm valve ◄► pinch valve

Diaphragm valves are comparable with pinch valves in terms of their function and design.
Both have a soft seal rubber element fitted in the valve housing that performs the main task of stopping the flow of media.
This elastic, shut-off element made out of various different elastomer mixtures is controlled in both types of valve by an external force (e.g. a mechanical, electric or pneumatic drive) and is pushed into the media until it ultimately creates a tight seal to shut off the flow or controls the flow rate to the desired extent.

Find out more below about the advantages that valves from AKO Armaturen offer you in comparison to diaphragm valves.

How does a diaphragm valve work?

Functional principle of a diaphragm valve

Source of the image of the diaphragm valve: Muskid, diaphragm valve, original file supplemented by pipelines, pumped media and animation, CC BY-SA 3.0

Function of an alternative to a diaphragm valve

Alternative to a diaphragm valve – opening and closing animation

A detailed comparison

The following general comparisons are based on publicly accessible information sourced from documents / websites published by various suppliers that were accessed online. The characteristics listed here may vary for valves offered by specific manufacturers of diaphragm valves. We do not provide any guarantee for the completeness / accuracy of the information. Special and high-performance configurations and certain properties of specialist types of valve were not taken into account.

Type of valve ►
▼ Characteristic
Diaphragm valves Pinch valves
Liquid / unproblematic
pumped media
Yes Yes
Problematic pumped media No Yes
Crevice-free design Yes Yes
CIP / SIP / RIP compatibility Yes / Yes / No Yes / Yes / Partially piggable
No redirection of the media flow No Yes
Constriction-free media flow No Yes
Low installation height No Yes
Resistance to wear No Yes
Availability of a large range of nominal sizes No Yes
Feedback about faulty diaphragms (membranes) / sleeves No Yes
Force control Yes  Limited*
Various different drive options Yes    Limited**
Stainless steel, aluminium & POM / PVC variants Yes Yes
Yes = Yes / Possible   Limited = Conditional / Limited   No = No / Not possible Ask AKO about alternatives
to diaphragm valves

* Force controlled membranes are only available for mechanical valves.
** Air operated shut-off valves from AKO only offer direct control using compressed air (cheaper solution). Other drive options are only available in combination with mechanical / manual shut-off valve solutions from AKO.

Media flow

The characteristics of the flow behaviour inside the valve is of essential importance for many transported media. To ensure that there are no blockages, encrustations or similar undesired behaviour by the pumped media, the passage through the valve should ideally have a constriction-free design. In addition, it is helpful if the media is able to flow directly through the valve without being redirected.

In general, diaphragm valves do not allow the constriction-free or direct flow of the media. They reduce the diameter of the pipeline in the area of the valve and redirect the product flow. Apart from when transporting water or other purely liquid media, this can cause problems. Furthermore, diaphragm valves require a higher pump capacity in order to ensure that the media flows at a constant rate after the reduced diameter of the pipeline in the area of the valve.
.
As diaphragm valves usually close on one side and are thus only fitted with a diaphragm on one side, it is possible for encrustations to form on the opposite side which is not actively supporting the closing process because of the contact pressure applied to the media by the diaphragm. These encrustations can build up over time and thus promote other blockages. In addition, these encrustations also make transporting the media more difficult.

Diaphragm valve   Pinch valve
No Direct and undisturbed passage through the valve Yes
No Constriction-free passage through the valve Yes
No No risk of blockages Yes
No Higher pump capacity not required due to the identical
cross-section of the pipeline in the area of the valve
Yes

Conclusion: Apart from when they are used to control unproblematic liquids (without impurities, solids, etc.), diaphragm valves have many disadvantages in comparison to the shut-off valves offered by AKO Armaturen. They do not usually have an identical diameter to the pipeline and the media is not guided directly and unhindered through the valve. In addition, this means that a higher pump capacity needs to be provided in order to compensate for the reduced diameter in the area of the valve.

Problematic pumped media

Transporting and controlling problematic pumped media, such as bulk materials, fibrous media, suspensions or contaminated liquids, is the most challenging task in the valve sector.
Diaphragm valves usually also display their design-related deficiencies in this area.

Due to the redirection of the pumped media through the diaphragm valve, it is possible for blockages to occur within the valve area, especially with viscous media or media containing solids.

The restricted passage through the diaphragm valve can also cause undesired downtimes because particles moving through the narrower passageway in the valve area can become entangled and thus disrupt or stop the flow of the media.

Diaphragm valve   Pinch valve
Limited Pumped media with small particles (e.g. granulate, tablets, etc.) Yes
No Bulk materials with larger particles (e.g. minerals, crushed stone, etc.) Yes
No Suspensions with solids or fibrous media Yes

Conclusion: Conventional diaphragm valves are only suitable to a very limited extent for transporting problematic pumped media such as bulk goods, liquids containing solids and similar media.
In contrast, the design of the shut-off valves that have been specially developed by AKO Armaturen is ideally suited to shutting off problematic media.

Design characteristics

Even if diaphragm valves generally work using almost the same principle as the valves produced by the company AKO Armaturen – the flow of the media is controlled or stopped by pressing together a rubber membrane or a rubber tube – they have significant disadvantages for many processes when compared to the valves offered by AKO Armaturen.

If plant operators or plant constructors require valves with a compact design, the use of diaphragm valves can quickly become a problem. As the control mechanism for diaphragm valves is generally fitted to the valve housing, the result is a substantial valve assembly that usually protrudes far beyond the diameter of the pipe connection or the pipeline even in the case of valves with small nominal sizes.

Higher susceptibility to wear due to, amongst other things, the redirection of the transported media and the increased friction associated with it, can also result in more frequent downtimes due to maintenance and repair work. In addition, diaphragm valves are not able to provide feedback on the limited functionality of the valve (and associated contamination of the control room above the membrane) in the event of a faulty diaphragm (membrane). Therefore, the operator needs to schedule maintenance work at regular intervals where necessary.

Diaphragm valves display their advantages when transporting unproblematic media through valves with small nominal sizes (e.g. nominal sizes of less than 10 DN) because the individual components are exposed to lower forces than is the case with larger nominal sizes. Therefore, many manufactures tend to focus on offering a range of diaphragm valves with smaller nominal sizes.

Diaphragm valve   Pinch valve
No, large height Minimum amount of space required (installation space) beyond the pipe connection Yes, minimal height
No, not wear resistant Less susceptibility to wear Yes, very wear resistant
No feedback Faulty diaphragm (membrane) / sleeve detectable  Limited*
Yes Position indicator (open / closed) Yes

* The pressure generated within the valve housing can be measured with the aid of an optionally fitted pressure switch. If the pressure does not reach the desired value or no pressure can be generated, this indicates a sleeve breakage because the compressed air is escaping via the damaged area.

Conclusion: In comparison to the valves produced by AKO, diaphragm valves have some design drawbacks that can leave plant operators facing unnecessary challenges.
Alongside the shortcomings when transporting pumped media described above, diaphragm valves also have some disadvantages outside of the actual pipelines.
If you are searching for a compact, sustainable, low maintenance and scalable valve solution, look no further than the product range offered by AKO Armaturen.

Controls & drives

A significant advantage offered by diaphragm valves in comparison to the air operated shut-off valves from AKO Armaturen is the so-called “force control” of the installed diaphragm. The installed drive mechanism is firmly connected to the fitted diaphragm and directly transfers the pulling force to open the valve without any delay. This counteracts any undesired deformation – e.g. due to the valve being held in a closed state for a long period of time.
As force control is not offered by AKO for its air operated shut-off valves, special grades of elastomer are available that display a higher rebound elasticity. This ensures constriction-free opening of the valves even after they have been held in a closed state for a long period of time. If you require force control, AKO has multiple mechanical or manually operated valve series with built-in force control available. Another advantage of these types of valves is that they can reliably dose the media flow according to your specifications and can also provide feedback in the form of a visual position indicator.

Air operated shut-off valves from AKO are directly operated exclusively using compressed air (or a fluid) and are thus not able to compete with diaphragm valves when it comes to the range of available drive options. However, direct control using compressed air means that you do not require an external drive that can quickly push up the price of the valve – even in the case of valves with small nominal sizes. If an external drive is nevertheless the only option for you – despite the higher costs and larger installation height – AKO can offer you an alternative in the form of mechanical or manually operated shut-off valves that are available with a range of different drives that is as diverse as the those offered for diaphragm valves.

Mechanical shut-off valves from AKO Armaturen

Mechanical / manual alternatives to diaphragm valves from AKO Armaturen

Force control, a wide range of drive options and the advantages of completely free and direct passage of the media.

Type of valve ►
▼ Characteristic
Diaphragm valve Pinch valve (air operated) Pinch valve (mechanical)
Force control Yes No Yes
Safety setting closed Yes Yes Yes
Position indicator (open / closed Yes Yes Yes
Regulation / dosing Yes   Limited* Yes
Position indicator (intermediate positions) Limited   Limited* Yes
Electrical drive Yes No Yes
Pneumatic drive (pneumatic cylinder) Yes No Yes
Pneumatic drive (direct control using compressed air) No Yes No
Hydraulic drive Yes    Limited** Yes
Manual drive Yes No Yes

* The applied pressure can be adjusted to roughly control the closing level of the sleeve with the aid of a proportional pressure regulator valve. Precise regulation of the flow rate is, however, only possible with the mechanical valves from AKO.
** The various types of air operated valve from AKO Armaturen can also be directly controlled with a fluid, although not using a hydraulic cylinder.

Conclusion: Diaphragm valves offer the advantages of force control and a diverse range of different drives in comparison to the air operated shut-off valves discussed here. However, AKO Armaturen has special mechanical and manually operated valves that offer these characteristics and which, alongside force control, can also be fitted with a selection of different drives that offer you the advantage of restriction-free and direct flow of the media.

Result: Comparison of diaphragm valves and pinch valves

In short: Pinch valves from AKO Armaturen are more than just an alternative to diaphragm valves.

As already described above, the USP of AKO pinch valves is the completely free, unhindered and direct passage that the pumped media take through the valve. This means that important factors that could disrupt the flow of the media are already excluded due to their design. As the valve does not constrict or redirect the transported media, neither blockages nor a reduction in the flow rate of the pumped media inside the valve are possible. 

Pinch valves can also be used for a larger range of transported media than diaphragm valves. The different valves offered by AKO can thus be used almost universally. No matter whether you are transporting and processing unproblematic liquids or problematic media such as bulk goods, slags or suspensions – AKO Armaturen is always your first point of contact for all of these processes.

Alongside the already described design-based advantages, pinch valves from AKO Armaturen also offer you a whole series of other benefits:

  • Crevice-free design of the entire valve
  • Variants for operating pressures up to 40 bar
  • Sleeve qualities that can be used at temperatures up to 120 °C
  • Extremely low-maintenance design
  • ATEX / EX variants
  • Use for applications in a vacuum
  • EHEDG variants
  • Low inherent weight
  • Economical TCO (Total Cost of Ownership)
  • Quick opening & closing times
  • All standard pipe connections (e.g. flange, internal thread, weld-on ends, threaded spigots, tanker flange, tri-clamps, etc.)

The AKO Sales & Support Team would be delighted to advise you on how you can replace your existing diaphragm valves with modern pinch valves and explain how easily AKO valves can be integrated into your system.

Design and function of the alternatives to diaphragm valves from AKO

Find out more about the design and function of the valves from AKO Armaturen.

The modular system for alternatives to diaphragm valves from AKO

Find out how valves from AKO Armaturen can be individually adapted to your requirements.

In-place cleaning for alternatives to diaphragm valves from AKO

SIP, CIP or RIP: Valves from AKO Armaturen can also be used for hygienic processes.

Submit your non-binding enquiry to AKO Armaturen!

Our Service Team would be delighted to advise you on the possibilities that pinch valves could offer you.
If you already have a specific application in mind, the AKO Service Team would naturally be delighted to send you a non-binding quote based on your specifications.
We would be pleased to send you technical information about the products on request. Alternatively, you can download this information on the AKO website in the Download section.

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