Maintaining uniform pressure in hygienic process lines is critical wherever product quality, fill accuracy, or cleaning validation matters. The Alfa Laval CPM constant-pressure modulating valve addresses this requirement through a purely pneumatic operating principle that eliminates the complexity, cost, and failure modes associated with electronic PID loops and positioners. Air pressure acts directly on a diaphragm assembly to position the valve plug, adjusting flow continuously to hold the set-point pressure steady. The result is fast, repeatable regulation that process engineers can commission and maintain without specialised instrumentation skills.

How does the CPM diaphragm valve construction ensure hygienic operation?

At the heart of the CPM sits a dual-layer diaphragm: a lower PTFE-covered EPDM diaphragm on the product-wetted side and an upper diaphragm separated by 12 stainless steel sectors. These sectors provide mechanical support and even load distribution across the full stroke range, preventing localised fatigue and extending service life. The PTFE-covered product-wetted surface withstands aggressive CIP and SIP media without additional lining or coating.

The valve body and seat are welded together as a single unit, removing crevices where product residue could harbour micro-organisms. Cover and body clamp together for rapid disassembly during maintenance, yet the clamped joint maintains a tight, repeatable seal during operation. Internal surface finish is Ra ≤ 1.6 μm as standard, with optional polishing to Ra ≤ 0.8 μm or Ra ≤ 0.5 μm for applications demanding higher cleanability assurance. Combined with the self-draining body geometry, this construction supports validated cleaning cycles in dairy, food, and pharmaceutical environments.

Which CPM variant suits inlet, outlet, or high-capacity pressure control?

Alfa Laval offers three CPM variants, each optimised for a specific pressure-control scenario. All three share a maximum inlet pressure rating of 1000 kPa (10 bar) and operate across the same temperature bands, so selecting the right variant comes down to control direction and throughput requirement.

The CPMI-2 regulates inlet pressure and is the standard choice for filling equipment where stable upstream pressure prevents overfilling, foaming, or dosing inaccuracy. The CPMO-2 regulates outlet pressure, serving bottling lines and downstream equipment that require consistent back-pressure. Dimensionally, the CPMO-2 shares the same diaphragm and clamp architecture as the CPMI-2 but features a longer body (211 mm versus 175.1 mm) to accommodate the reversed flow path. The CPM-I-D60 targets high-capacity lines with its two-part body design — upper and lower sections with a separate inlet tube — handling larger flow volumes at 413.2 mm overall length while retaining the same pneumatic regulation principle.

What Kv values and connection standards are available for sanitary pressure control?

Specifying a constant-pressure modulating valve means matching the Kv value to the required flow characteristic. The CPM range offers five distinct Kv values — 7, 9, 23, 2/15, and 60 — covering everything from low-flow dosing circuits to high-throughput transfer lines. Pairing the correct Kv with line diameter ensures the valve operates within a responsive stroke range rather than at an extreme that reduces controllability.

ISO, DIN, SMS, BS, and Clamp end connections are available, with male parts or clamp liners supplied to the required standard. For the CPM-I-D60, DIN male connections use a 30 mm fitting and SMS male connections use a 24 mm fitting, reflecting the larger pipe sizes typical of high-capacity installations. Engineers integrating the CPM into an existing line can match the valve directly to the dominant piping standard on site without adaptors or transition pieces.

When should the booster or ATEX option be specified?

In applications where product pressure exceeds the available instrument air supply, a booster accessory multiplies effective actuation force. With the booster fitted, the CPM can regulate product pressures up to 1.8 times the air supply pressure — a practical necessity on high-pressure filling lines or long transfer runs where friction losses push operating pressure above what standard plant air can counteract.

For installations in hazardous areas classified under ATEX directives, Alfa Laval supplies an ATEX-rated version of the CPM. An air throttling valve accessory is also available for the CPM-2 variants, providing fine adjustment of the valve's regulating speed to prevent pressure overshoot during rapid load changes. Specifying the throttling valve is especially relevant on lines with variable demand, such as multi-head fillers cycling between idle and peak throughput.

Temperature also drives material selection. Standard PTFE/EPDM diaphragms cover -10 °C to +95 °C with NBR upper diaphragm, extending to +140 °C when the upper diaphragm is upgraded to PTFE-covered EPDM. For sustained temperatures above 140 °C, both diaphragms can be specified in solid PTFE with FPM O-rings — a configuration suited to SIP cycles or hot-product transfer in pharmaceutical production.