Product: Cerabar M PMP51 (flush-mounted metal diaphragm sensor)
Configuration: 316L stainless steel diaphragm / Tri-Clamp 1½" hygienic connection / 4-20mA HART output / IP69K housing
Quantity: 8 units
Lead Time: 4 weeks (including custom hygienic connection fittings)
Application: Dairy product transfer lines with CIP cleaning cycles; media temperature from 4°C (product) to 130°C (CIP); SIP sterilization at 150°C for up to 1 hour; pipe diameter DN40; pressure range 0–16 bar
Market Context
In Germany—a core region for European dairy processing—CIP (Clean-in-Place) has become a standardized process in food quality compliance systems. However, as cleaning intensity continues to escalate—temperatures rising from conventional 80°C to 130°C, cleaning frequency increasing from once daily to batch-to-batch intervals—the "dead leg" issue at process connection points has become critical. Traditional threaded pressure transmitter interfaces create recessed zones on the inner pipe wall where CIP fluid cannot achieve effective scouring, leading to protein residue accumulation.
Industry feedback indicates that such dead legs are a primary contributor to post-CIP swab test failures, directly impacting batch release and FDA/EHEDG audit passing rates.
Customer and Application Profile
Customer: A mid-sized dairy in Bavaria, Germany, processing approximately 200 tons of raw milk daily, with product lines including UHT milk, yogurt, and cheese products.
Existing Issues:
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8 pressure monitoring points on transfer lines utilized threaded pressure transmitters, requiring manual disassembly for post-CIP cleaning, increasing downtime;
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Three microbiological contamination events in Q1 2025 traced to residue accumulation at pressure interface dead legs;
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Customer planned to pass EHEDG certification re-audit in 2026; existing installation did not meet hygienic design guidelines.
Process Parameters:
Our Solution
Based on the customer’s process evaluation, Cerabar M PMP51 flush-diaphragm pressure transmitters were recommended and installed, with the following core selection rationale:
1. Flush Diaphragm Eliminates Dead Leg
Tri-Clamp 1½" hygienic clamp connection (ISO 2852) is employed, with the process isolating diaphragm mounted flush with the pipe inner wall—the diaphragm surface is directly exposed to CIP fluid flow, eliminating the recessed cavity that is structurally unavoidable in threaded installations. Standard diaphragm surface finish is Ra≤0.76μm, with Ra≤0.38μm electropolished option available—both compliant with EHEDG and 3-A standards.
2. CIP/SIP Temperature Tolerance Verified
The PMP51 metal diaphragm system withstands 150°C steam sterilization for up to 1 hour, covering the customer’s SIP cycle (150°C/20 min) with a substantial margin. Endress+Hauser conducted over 400 thermal shock cycles between cold water and 150°C steam during testing to verify measurement repeatability.
3. Wetted Material Compatibility
The standard 316L diaphragm offers adequate corrosion resistance for raw milk and 1.5% NaOH CIP solution. Should the customer later switch to chlorinated disinfectants or peracetic acid, upgrades to Alloy C or rhodium+gold-plated diaphragms are available.
4. Ingress Protection and Field Environment
The transmitter housing is rated IP69K, withstanding high-pressure, high-temperature water jets—suitable for daily floor and equipment wash-downs in dairy facilities. The 4-20mA HART output is compatible with the existing PLC system, requiring no protocol conversion.
Key Technical Parameters (Solution Summary)
Customer Feedback
Six-week follow-up interview (Andreas Müller, Production Supervisor):
“The most noticeable change after switching to PMP51 is the post-CIP swab test results. Previously, 2 to 3 of the 8 points required retesting; now every test has passed for six consecutive weeks. We no longer disassemble pressure connections for manual cleaning, saving approximately 12 minutes per batch changeover. Additionally, temperature drift has improved significantly—the old threaded sensors exhibited pressure reading fluctuations of ±0.5 bar during CIP temperature ramps, requiring manual data rejection. The PMP51 maintains fluctuations within ±0.1 bar at 130°C CIP temperature, allowing direct real-time data use in the DCS without manual intervention.”
Summary
Value Points:
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Eliminates hygienic dead legs: Flush diaphragm design provides cleanability equivalent to the pipe wall at pressure measurement points;
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Measurement consistency under temperature variation: The metal diaphragm system maintains thermal zero/span change below 0.15% per 10K across –40°C to +130°C, ensuring data availability during SIP cycles;
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Maintenance efficiency: No disassembly cleaning required—each point saves ~1.5 operator-minutes per CIP cycle. At 3 daily washes × 8 points, annual savings total approximately 182 operator-hours;
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Compliance assurance: Installation meets EHEDG and 3-A hygienic design guidelines, supporting the customer’s 2026 certification re-audit.
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