Quick Answer:
The diaphragm valve with a weir represents the most common design in the fields of pharmaceutical, biotechnology, dairy, and beer production. It is used where no dead legs and complete draining of fluid are needed. What makes HEYIโs weir diaphragm valves different from other designs is that their special raised weir in the valve body creates the flow path of the fluid and its seat.
What Is a Weir Type Diaphragm Valve?
In a weir diaphragm valve, there is a high point referred to as a weir, which is machined in the center part of the valve body. It acts as a support for the diaphragm that closes the valve when pressed on it and opens by moving away from it. Fluids pass through the weir when the valve is opened. The diaphragm forms the seal over the weir when it is closed.
The advantage of the weir valve type is the small stroke of the diaphragm. The diaphragm moves a short distance to open or close in the area of the weir.
HEYI’s Tri-Clamp Diaphragm Valve is a weir type. The body is one-piece molded construction with a mirror-polished internal surface to Ra 0.4 ยตm. Tri-clamp ferrule ends on both sides allow quick-release connection without tools.
Weir Type vs Straight-Through Diaphragm Valve
There are two primary configurations of diaphragm valve bodies. Each of them is suitable for different flow needs. Knowledge of the differences in their construction is important for selection.
| Feature | Weir Type (Tri-Clamp) | Straight-Through / U-Type |
| Body geometry | Raised weir across center | Smooth, unobstructed bore |
| Diaphragm stroke | Short | Longer |
| Drainability | Excellent (self-draining) | Full bore drainage |
| Flow restriction | Slight (over weir) | None |
| Diaphragm life | Longer under frequent cycling | Shorter under frequent cycling |
| Best for | Clean service, CIP/SIP | Viscous fluids, slurries |
HEYI’s U-Type Diaphragm Valve represents the straight-through configuration. Its smooth, unobstructed internal bore handles viscous fluids and products with suspended solids more effectively than a weir body.ย
The drawback to this is that the valve needs a greater diaphragm stroke and increased stress on the material of the diaphragm over time.
For the application in regulated processes with clean fluid media, the weir design is generally preferred. For thick and particle-containing media, the U-type design is preferred.
How the Weir Design Eliminates Dead Legs
Dead legs are spots within a fluid line system where the fluid could become stagnant and cleaning fluids can fail to reach. This occurs with the conventional design where the fluid inside the branch of the line causes the same effect.
This is not the case with the weir body shape. Once the diaphragm opens up, the fluid that moves over the weir will drain out. The fluid is drawn down by the force of gravity.
The flow body shape has no horizontal pocket where the fluid could accumulate.
That is why ASME BPE and 3-A sanitary standards dictate that the weir body shapes must be used in situations where the fluid makes contact. These industries include pharmaceutical and food processing industries.
This design fulfills the 6D dead leg requirement of ASME BPE.
Diaphragm Materials and Their Applications
The diaphragm is the only component that contacts the process fluid in a weir valve. Material selection determines chemical compatibility, temperature range, and regulatory compliance.
EPDM
EPDM is the default choice of material for most food, dairy, and pharmaceutical applications for diaphragms. It can handle caustic cleaning solutions, steam sterilizations, and many process chemicals without deteriorating. The temperature range of operation for EPDM is normally from -10 to 130 degrees Celsius. EPDM is not suitable for oils or solvents.
PTFE
Diaphragms that are lined with PTFE have the largest chemical compatibility. They are chosen in cases when there are aggressive chemicals, acidic or alkaline conditions, and cases where there is an issue with extractables due to elastomeric materials. The elasticity of PTFE is lower than that of EPDM and silicone.
Silicone
Silicone diaphragms are ideal for high-temperature applications as well as those requiring flexibility at wide temperature ranges. Service temperature reaches up to 200 degrees centigrade, which will cover steam cleaning and the SIP cycle.
Silicone conforms to FDA standards and is used extensively in food contact applications where thermal cycling is prevalent. Silicone, along with two other diaphragms, can be found in HEYIโs weir-type diaphragm valves.
ASME BPE and 3-A Requirements
ASME BPE MJ deals with mechanical joints and valve specifications for bioprocessing equipment. ASME BPE requires that the product contact surfaces be of the surface finish class for the intended use.
The minimum surface finish class for general bioprocessing is SF1 (Ra 0.51 ยตm). HEYI’s internal finish Ra 0.4 ยตm closely adheres to such requirements.
Meanwhile, 3-A Sanitary Standard 85-03 applies to diaphragm valves. This standard requires that the product contact surfaces should be smooth and crevice-free. Also, there should be a recognized diaphragm material. Complete drainage of the valve is also a requirement.
CIP and SIP Compatibility
The weir-type diaphragm valve is compatible with CIP and SIP cleaning processes without any changes to the valve body or connectors.
In the CIP process, the cleaning liquid passes through the open valve in the same way as the process liquid. The design of the weir provides a configuration where there is no portion of the internal surface that is inaccessible by the cleaning liquid. The diaphragm may remain open throughout the CIP process.
In the SIP process, steam enters the valve in its defined position through the process connection. The material used in the manufacture of the diaphragm should be able to withstand the sterilization temperature. EPDM can be used in standard SIP processes up to 130 degrees Celsius, and silicone can be used up to 200 degrees Celsius.
Where Weir Type Diaphragm Valves Are Used
Pharmaceutical Manufacturing
These valves find applications in WFI lines, buffer preparation lines, API lines, and fermentation harvest lines. The low diaphragm stroke in these lines facilitates high-cycle automation. Traceability and surface finish documentation are available to aid in the qualification of the equipment.
Biotech and Cell Culture
Weir valves find applications in bioreactor sampling ports and media addition lines. These are chosen for their low-turbulence flow path, which ensures that there is no mechanical stress to the shear-sensitive cell culture fluids.
Dairy and Brewery
Pasteurization flow paths, tank transfer lines, and CIP return lines in dairy and brewery operations make extensive use of weir-type diaphragm valves. These are equipped with EPDM diaphragms which can withstand the harsh chemical environment.
How to Specify a Weir Type Diaphragm Valve
Five parameters define a complete weir valve specification.
Body size and connection end: Tri-clamp ferrule sizes follow 3-A and ISO 2852 standards. Confirm the OD size matches the installed tubing specification.
Diaphragm material: Match to the process fluid and the cleaning agent. Confirm temperature range covers both process and sterilization conditions.
Surface finish class: State the SF class per ASME BPE or confirm Ra value in micrometers. Do not specify “sanitary finish” without a numeric Ra value.
Actuation method: Manual handwheel, pneumatic actuator, or solenoid. Confirm actuator signal type and supply pressure for pneumatic units.
Documentation requirements: Material test reports, Ra measurement records, and 3-A or FDA compliance declarations should be listed explicitly. HEYI provides full material traceability and surface documentation per order. Standard stock ships within 1 to 7 days.
OEM custom orders take 15 to 35 days. Get a quote, and the technical team responds within 24 hours.
