Author: Site Editor Publish Time: 10-12-2026 Origin: Site
Pasteurizers play a critical role in the heat treatment of milk, fruit juice, beverages, beer, and other liquid food products. Any abnormalities regarding temperature, flow rate, pressure, cooling, or cleaning not only impact production efficiency but can also lead to incomplete pasteurization, product quality degradation, or even food safety risks.
Upon detecting an anomaly, one should not simply clear the alarm and resume production; instead, the pasteurization temperature, holding time, and product flow path must first be verified against process specifications. Subsequently, a troubleshooting process—proceeding from the simplest to the most complex elements—should be conducted to inspect heat sources, cooling sources, flow rates, valves, sensors, heat exchangers, and control systems.
Before inspecting the equipment, stop the product feed, shut off utilities (such as steam, hot water, power, and compressed air) as required, and relieve pipeline pressure. Do not disassemble the equipment while it is under pressure, at high temperatures, or powered on, nor should automatic alarm or safety interlock functions be bypassed.
Symptoms | Common Causes | Priority Checks |
Failure to reach set temperature | Insufficient heat source, excessive flow rate, heat exchanger fouling | Check the steam pressure or hot water temperature, product flow rate, and whether the heat exchanger is fouled. |
Continuous temperature fluctuation | Unstable feed temperature, control valve malfunction, sensor deviation. | Check whether the feed temperature is stable and if the steam control valve and temperature sensor are functioning correctly. |
Continuous product backflow | Sterilization temperature fails to meet standards. | Check the steam pressure and verify that the steam control valve and temperature sensor are operating normally. |
Decrease in product flow rate | Pump malfunction, pipeline scaling | Check that the product pump is functioning correctly and that the heat exchanger has been thoroughly cleaned. |
High discharge temperature | Insufficient cooling water, valve opening insufficient | Check the cooling water tower and cooling water pump for proper operation, and ensure valves are sufficiently open. |
Product or medium leakage | Aging of sealing gaskets, damage to plates or piping | Replace seals, plates, or heat exchanger tubes. |
Incomplete CIP cleaning | Flow rate, temperature, concentration, or duration not meeting requirements | Check and configure the cleaning parameters. |
Symptoms | Possible Causes | Solutions |
Product temperature consistently fails to reach the setpoint | Insufficient steam pressure, excessively low hot water temperature, or inadequate heat source supply capacity | Check steam pressure, hot water temperature, and the heat source supply system. |
Product heats up slowly, or the temperature stops rising after reaching a certain level | Heat exchanger fouling, insufficient heating medium flow rate, or insufficient control valve opening | Check the heat exchanger, heating medium flow rate, and the operating status of control valves. |
Product temperature fluctuates continuously and fails to stabilize near the setpoint | Unstable heat source supply, fluctuations in product flow rate, or unsuitable temperature control parameters | Stabilize heat source and product flow rates; check temperature sensors and PID control parameters. |
Touchscreen displays abnormal temperature readings or frequent fluctuations | Temperature sensor malfunction, loose wiring, or signal interference | Check sensors, wiring, and signals; perform calibration if necessary. |
Product continuously enters automatic recirculation mode before reaching the required temperature | Actual sterilization temperature is insufficient; divert valve operates according to safety logic | Check the heating system and verify that the product meets validated sterilization conditions. |
Product continues to recirculate even after reaching the setpoint | Abnormal temperature signal, divert valve malfunction, abnormal position feedback, or abnormal control logic | Compare actual temperatures with displayed values; check the divert valve, actuator, and PLC control signals. |
Product frequently switches between normal discharge and recirculation | Temperature fluctuations, unstable sensor signal, or repeated triggering of the diversion control | Check temperature history curves, heat source supply, and the divert control system. |
Check that the steam or hot water supply is normal.
Verify that the actual product temperature matches the temperature displayed on the touchscreen.
Check the product flow rate, the condition of the heat exchanger, and the temperature control valve.
Check the divert valve, position feedback, and PLC control logic.
Resume normal product discharge only after confirming that the sterilization temperature, holding time, and flow rate all comply with validated process requirements.
Safety Note: Do not attempt to resolve persistent recirculation issues by bypassing interlocks or forcing the divert valve to switch. Reaching the set temperature does not necessarily guarantee a fully compliant sterilization process; the specified holding time and other process requirements must also be met.
Symptoms | Possible Causes | Solutions |
Actual flow rate is lower than the set value | Insufficient feed pump speed or pump performance degradation | Check pump speed, operating status, and VFD settings. |
Flow rate is gradually decreasing | Clogged filter or pipeline fouling | Inspect and clean filters and piping. |
Pump is running but discharge volume is insufficient | Air in the pipeline, insufficient feed, or poor suction conditions | Check feed liquid level, pipe seals, and venting conditions. |
Product flow rate is significantly lower than the water test flow rate | High product viscosity, high solids content, or unsuitable pump selection | Verify pump suitability and operating parameters based on actual product characteristics. |
Flow meter reading is abnormal | Flow meter malfunction, improper installation, or signal abnormalities | Check instrument installation, full-pipe conditions, wiring, and calibration. |
Key areas for inspection include the pressures upstream and downstream of the pump, flow meter readings, and the actual product discharge rate. Satisfactory results from a water test do not guarantee that the same flow rate can be achieved when processing higher-viscosity products.
Additionally, for continuous sterilization systems equipped with holding tubes, the flow rate must not be arbitrarily increased to boost production capacity. Flow rate directly affects the product's residence time within the tube and must comply with validated process requirements.
Symptoms | Possible Causes | Solutions |
Excessive pressure in the heating section or piping | Pipeline blockage, valve not fully open, or excessive downstream resistance | Check valve opening, filters, and pipelines for blockages |
Insufficient pump inlet pressure | Insufficient raw material supply, suction line blockage, or air leakage | Check raw material levels, feed lines, and sealing conditions |
Insufficient pump outlet pressure | Insufficient pump speed, pump wear, or air trapped inside the pump | Check pump operating status, rotational speed, and venting |
Continuous fluctuation of pressure gauge readings | Unstable pump operation, air ingress into the pipeline, or pressure sensor malfunction | Inspect pumps, pipelines, and pressure gauges |
Abnormal pressure difference across the product heat exchange section | Plate blockage, fouling, or increased product flow resistance | Inspect heat exchangers and pipelines; clean if necessary |
Key inspection points: Pressures at the pump inlet, pump outlet, and both the inlet and outlet of the heat exchanger should be recorded individually, rather than relying on a single pressure gauge.
If the equipment utilizes a product-to-product regenerative heat exchanger, the differential pressure between the pasteurized (or sterilized) product side and the unpasteurized (or unsterilized) product side must also be checked. For applicable dairy systems, it must be ensured that the differential pressure and flow direction comply with sanitary design requirements to prevent contamination of the treated product by the untreated product.
Symptoms | Possible Causes | Solutions |
Product outlet temperature exceeds the target value | Cooling water temperature too high | Check cooling water supply temperature and refrigeration system |
Cooling rate slows down | Insufficient cooling water flow rate | Inspect cooling water pumps, valves, and water supply piping. |
Cooling is normal during initial operation but deteriorates subsequently | Scaling on cooling plates or fouling on heat exchanger surfaces | Inspect the heat exchanger and perform appropriate CIP cleaning. |
Product temperature rises as production output increases | Product flow rate exceeds the cooling system's design capacity | Verify the equipment's rated throughput and adjust it to within the design range. |
Cooling water supply is normal, yet product temperature remains high | Reduced heat transfer efficiency in the cooling section, abnormal valve control, or insufficient heat transfer area | Check the design capacities of the cooling section, control valves, and heat exchanger. |
Key inspection points: Simultaneously record the inlet and outlet temperatures of the cooling water and the product, as well as the flow rates on both sides; this is necessary to determine whether the issue stems from insufficient cooling capacity or reduced heat exchanger efficiency.
If a chilled water system is used, also check the cooling capacity and set temperature of the chiller unit, as well as the operating status of the circulation pump.
CIP (Clean-in-Place) refers to an in-situ cleaning system. Suboptimal cleaning results do not necessarily indicate an insufficiency of cleaning agents; they may also be related to temperature, duration, flow rate, or the cleaning procedure.
Symptoms | Possible Causes | Solutions |
Product residue remains on plates or in pipelines | Insufficient cleaning time, inadequate flow rate, or incomplete cleaning procedure | Verify cleaning steps, circulation times, and flow rates. |
Visible fat or protein residue | Cleaning temperature, detergent concentration, or cleaning procedure unsuitable for the type of soil | Adjust conditions according to the cleaning agent supplier's requirements and validated procedures. |
Persistent mineral deposits or scale | Inappropriate acid washing step or insufficient acid washing conditions | Identify the type of scale and employ a validated acid cleaning procedure. |
Foam or cleaning agent residue remains after CIP | Inadequate final rinse or incomplete drainage | Check rinse water volume, rinse endpoints, and pipeline drainage. |
Specific pipeline sections or equipment areas are repeatedly not cleaned effectively | Dead legs in piping, insufficient spray coverage, or poor circuit design | Check piping layout, cleaning coverage, and flow rates in individual branches. |
Unstable flow rate or pressure during the CIP process | CIP pump malfunction, incorrect valve switching, or pipeline blockage | Inspect cleaning pumps, valve matrices, filters, and piping. |
Key focus areas for assessment: Do not limit checks to cleaning agent concentration alone. Simultaneously verify cleaning temperature, duration, flow rate, and concentration, as well as post-cleaning validation results; adjust procedures based on the actual type of soil.
The sequence of acid and alkaline cleaning steps, along with temperatures and concentrations, must be determined based on equipment materials, cleaning agent specifications, and validated cleaning procedures; the same set of parameters should not be applied indiscriminately to all products.
When encountering equipment anomalies, it is recommended to troubleshoot in the following order:
1. Record fault details
Record alarm codes, temperature, flow rate, pressure, valve status, and product conditions to prevent the loss of fault information after a system reset.
2. Assess impact on product safety
Verify that the pasteurization temperature and holding time are within specifications. Products posing safety risks must be isolated and must not be released.
3. Check plant utilities
Confirm the stability of steam, cooling water, chilled water, electricity, and compressed air supplies. Many equipment anomalies actually stem from issues with external utility or medium supplies.
4. Check flow rate and pressure
Inspect the product pump, filters, valve positions, piping connections, and heat exchanger pressure differential.
5. Check temperature and control systems
Inspect temperature sensors, control valves, automatic discharge valves, control parameters, and historical alarm records.
6. Check heat exchanger and CIP status
Assess for fouling, blockages, leaks, or inadequate cleaning.
7. Resume production after verification
Following repairs, conduct tests using water or an appropriate medium to verify that temperature, flow rate, pressure, valve operation, diversion functions, and sealing integrity are normal before resuming full-scale production.
Continued operation is not recommended if any of the following occur:
• Pasteurization temperature consistently falls below the required level;
• Temperature sensor failure prevents verification of the actual temperature;
• Cross-leakage occurs between the product and the heating or cooling medium;
• Significant leakage is detected in the heat exchanger, piping, or valves;
• System pressure exceeds the permissible range;
• Product pump exhibits severe vibration or abnormal noise;
• Electrical system emits a burning odor, produces smoke, or trips repeatedly;
These issues may directly compromise equipment or product safety and should be addressed by qualified technical personnel.
The key to minimizing malfunctions lies in establishing a stable operational baseline and promptly detecting trend changes.
It is recommended to maintain long-term records of:
• Pasteurization temperature;
• Product flow rate;
• Temperature difference across the heat exchanger inlet and outlet;
• Heat exchanger pressure differential;
• Steam and cooling water conditions;
• CIP parameters and cleaning results.
Additionally, sensors should be calibrated regularly, and pumps, valves, and seals should be inspected.
Common issues with pasteurizers mainly focus on temperature, flow rate, pressure, cooling, leakage, and automatic control.
Effective troubleshooting should not only address surface alarms, but should be carried out according to the following logic:
Identify the fault symptoms → Check temperature and controls → Check flow rate and pressure → Inspect the heat exchanger → Assess product safety risks → Verify and then resume production
If the fault involves sustained low sterilization temperature, cross-contamination of media, system overpressure, or electrical safety, production should be stopped immediately and inspected by professional technical personnel.
