Sanitary diaphragm valves are more informally known as the clean valves thanks to their simple yet efficient working principle.
A handwheel / An actuator is used to control the shaft that connects to the diaphragm membrane, which in turn controls the flow rate for the process media. Since the membrane itself is made of some flexible material, most sanitary diaphragm valves don’t feature any extra sealing material. In fact, once pulled up or pushed down by the actuator, the diaphragm seals the flowing material entirely from both the environment and every other moving part of the mechanism.
In addition to the industries mentioned, others like dairy, food, beverage and chemical industries also prefer diaphragm valves since the best protection against any kind of contamination is the top priority for them.
Besides the “purity conservation rate”, there’s another reason why sanitary diaphragm valves are so popular among these industries. While there are other valves that are about equally efficient as diaphragm valves, the latter is the only straight through valve whereas all the others feature the 90-degree configuration.
Scientific & Simple Design
All diaphragm valves feature a straight through design, which means there’s no bend between the inlet and outlet. While the number of outlet port might vary between designs, the core flow pattern is constant. The seal seat lies between the two ports with the membrane diaphragm just above it, which is pressed down with the actuator. All sanitary diaphragm valves follow this basic design.
To avoid contamination of the process material and the compromise valve functionality, most valves require some kind of sealing material between the valve body and the compressor that regulates material flow. Some even use sealing materials between the ports and their subsequent pipeworks.
The diaphragm, on the other hand, is thick in the middle and thin around the edges, which means it can stretch easily in every direction. This is why sanitary diaphragm valves don’t require any extra sealing material.
As a professional manufacturer of sanitary diaphragm vavles, SIMPLE VALVES diaphragm system has very good performance in dealing with dead angles. Our sanitary diaphragm vavles fulfill EHEDG requirements.
Smooth Surface Finish
The importance of surface finish for any valve is that it measures the friction rate of passing material. The lower the friction, the lower the chance of breaking chemical bonds and generating byproducts. However, there’s a more direct and observable part played by surface finish rate. Any surface with too few scratches in per-linear inches and too many peaks and valleys mean it gets dirty quick.
These two features are measured with Grit and Ra respectively and the standard for the latter is 32, which is the basic standard for all sanitary diaphragm valves. Biopharmaceutical and pharmaceutical companies usually use the ASME BPE standard instead of Grit/Ra.
The basic material of a diaphragm valve is always something that is highly resistant to chemical contamination and corrosion. The body is made of either plastic (like PVC and CPVC) or metal (like cast iron, copper, ductile iron, brass and stainless steel).
However, since stainless steel is more acid and corrosion resistant than others, sanitary diaphragm valves are almost exclusively made of this. More specifically, the AISI 316 and 316L stainless steel. AISI, which stands for the American Standard, is the most used standard measure for categorizing steel build. Both of these are austenitic steel with face-centered cubic atomic structure, which makes the material extremely durable.
Some companies, like SIMPLE VALVES, also add molybdenum in the structure to make the material more resistant to chloride. The only actual difference between the 316 and 316L alloys is their carbon levels. 316L’s carbon level never passes past 0.03% whereas 316’s is always around the medium. This is why the former is more resistant to corrosion when used in a welded structure.
The diaphragm itself is made of some flexible elastomers like Ethylene Propylene (EPDM) and Polytetrafluoroethylene (PTFE). The most common variants of these materials that are used in making the diaphragm are EPDM+Teflon (PTFE), silicon and Viton (FPM).
PTFE is a hydrophobic fluorocarbon solid, which means it’s resistant against all kinds of water and water-based wetness. Its coefficient of friction is one of the lowest displayed by any solid.
Silicon is an extremely temperature resistant material that can withstand anything between -80 degrees Fahrenheit and +450 degrees Fahrenheit. However, while it’s highly resistant to ozone and most corrosive elements, undiluted lye and steam can actually destroy a silicon-based diaphragm.
Viton is pretty similar to silicon when it comes to ozone and temperature resistance. Vulnerable to acid, lye, alcohol and steam corrosion, Viton can stand up to a temperature of 400 degrees Fahrenheit. FPM is mostly used as a substitute for silicon when the latter cannot be used for technical reasons.
Advantages of Using Sanitary Diaphragm Valves
1. The smooth inner-surface finish ensures against particle entrapment, which keeps the mechanism clean.
2. The mechanism can perform the self-draining function when fitted into a pipeline with 2-degree incline.
3. When made from a forged 316L alloy, sanitary diaphragm valves achieve a lower porous rate than when a casting alloy is used. This allows for a surface finish as low as 10 Ra. The surface can be made even smoother when electropolished.
4. The simplicity of diaphragm valves design means that they can be fitted into a single block designed for a specific function in multiple configurations, without compromising the straight-through pattern.
5. The diaphragm itself can be reinforced with mesh fiber in case the valve has to handle abrasive materials or somewhat-detrimental elements.
6. Since sanitary diaphragm valves are termed as “top entry”, they can be welded into the pipeline, essentially getting rid of clamp joints. The diaphragm and bonnet can be removed and serviced without dismounting the whole body in top entry valves.
Technical Specifications of SIMPLE VALVES Sanitary Diaphragm Valves
- Body Material: ASTM A351 CF3M (default), AISI316L Forged Body, ASME BPE 316L
- Diaphragm Material: Silicon or Viton (FPM). Single PTFE+EPDM (default)
- Size: 1/2 inches to 4 inches
- Working Pressure: Maximum 145psi (10 bar)
- Surface Finish: Minimum 32Ra (32µin). The default rate is customizable according to requirement.
- Port Connection: Changeable upon request including but-welded and sanitary tri-clamp.
- Actuator Control: Manual handwheel, pneumatic (air pressure controlled) and intelligent control.
- Port: 2/3 way, multiport.
- The specifications detailed above give a standard way to measure the efficient functionality of a good sanitary diaphragm valve. The proper material combination can make the whole system more enduring than generally expected.
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