Alfa Laval Unique PMO Plus® Mixproof Valve

The Alfa Laval Unique PMO Plus® mixproof valve offers all the performance of a Unique Mixproof valve and, in addition, meets the requirements of 3-A/PMO standards. The mixproof valve design allows clean-in-place (CIP) fluid to flow to clean one chamber while product is running in the other chamber, without the risk of cross-contamination. Eliminating clean-in-place (CIP) downtime and allowing automated product transfer are just two of the advantages that mixproofs provide. Unique PMO Plus Mixproof Valves combine Alfa's superior cleanability and reliability with the required features for meeting the PMO standard making it a powerful solution for dairy applications.

Unique PMO Plus valves are authorized to carry the 3-A symbol.

The Pasteurized Milk Ordinance (PMO)

Paragraph 15p(B) of the Pasteurized Milk Ordinance (PMO) outlines the requirements for the use of mixproof valves in applications involving milk products and cleaning solutions to ensure the hygienic and safe separation of dairy products flowing concurrently through the same valve.

The PMO requires that:

  • Both valve seats must be position detectable
  • The leakage chamber, found in all mixproof valves, must have the same cross-sectional area as the valve body port connections
  • The actuator must be fail-safe by spring-to-close

In 2007, the Food and Drug Administration (FDA) changed the PMO to allow clean-in-place (CIP) solution to clean one valve seat while product is flowing in the opposite housing. This change virtually eliminates CIP downtime, so processors can run continuous dairy operations and increase production.

In 2008 the FDA issued memorandum M-b-356, confirming that Alfa Laval’s Unique PMO Plus mixproof valve is Pasteurized Milk Ordinance paragraph 15p(B) compliant.

The following benefits make the Unique PMO Plus stand out from the competition:

  • Proven design: Same fundamental technology used in the industry for more than a decade
  • Retrofittable: Replacement of a few components enables conversion of installed Unique PMO valves to Unique PMO Plus
  • Only three elastomers in the isolation chamber: Minimizes risk of product contamination
  • Tested and FDA compliant to 145 psi: The highest operating pressure available for the widest range of process applications
  • Designed with a mix of radial and axial seals: A proven, leading design to protect product
  • Standard, single unit actuator: Simple operation with fewer moving parts
  • Same wetted and actuator service kits as the unique PMO valve: No need to learn or stock new parts
  • Maintenance friendly: No adjustments are required when reassembling the valve after service

This Unique PMO Plus Mixproof valve is based on the well proven and exceptionally flexible design of the Unique PMO Mixproof valves from Alfa Laval. It meets the demands from the 3-A/PMO (Pasteurized Milk Ordinance paragraph 15p(B)) standards saying that all movements have to be detectable, as well as the vent tube has to have the same or greater area than the connection pipe. Furthermore, the Unique PMO Plus meets the FDA demands for seat lift compliance M-b 356. This allows CIP flow to clean one chamber while product is running in the other chamber, thus eliminating CIP downtime. Finally, the actuator is fail-safe by spring-to-close.

Working Principle

Unique PMO Plus is remote-controlled by means of compressed air. The valve is a normally closed (NC) valve. The valve has two independent plug seals, forming a leakage chamber between them which is at atmospheric pressure or less during every working condition. In the rare case of fluid passing a valve seat, the fluid will enter the leakage chamber and be discharged through the leakage outlet. When the valve is open, the leakage chamber is closed.


This PMO Plus edition of the Unique Mixproof valve is a high-end valve with regards to process security as well as from a sanitary point of view. The valve plugs are always balanced in both upper and lower valve body, securing no sensitivity to pressure spikes. The lower and upper seats are position-detectable by the ThinkTop® and a yoke-mounted, external sensor.

Unique PMO vs. Unique PMO Plus
Product Wetted Steel Parts316L
Other Steel Parts304
Product Wetted SealsNBR (std.), EPDM, HNBR, or FPM
Other SealsCIP seals: EPDM
Actuator seals: NBR
FinishExternal bright/internal polished Ra<32µ"

Note: The Ra values are only for the internal surface.

Technical Data
Product Pressure (max)145 psi (for higher pressure, contact CSI)
Product Pressure (min)Full vacuum
Temperature Range23°F - +257°F (Depending on seal material) (For higher temperature, contact CSI)
Air Pressure116 psi
Dimensional Data
Size (in)22.534
Weight (lb)33.00053.00053.00075.000

**The measure C can always be calculated by the formula C = ½ID-upper + ½ID-lower + 1 inch.

Pressure Drop/Capacity Diagrams


Note: For the diagrams the following applies: Medium: Water (68°F). Measurement: In accordance with VDI 2173.

Valve Body Combinations

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