Cheese Vat Troubleshooting: Causes & Fixes

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Problems on this page:

Slow coagulation or weak curd Curd pieces uneven in size Cooking temperature not followed Agitator or knife frame drive fault High fines in the whey Whey draining slowly Cleaning results failing Milk fill volume wrong Acid development slow

Slow coagulation or weak curd

Hits OEE: Quality

Symptoms: The milk takes longer than usual to set, or the curd is soft and shatters when cut.

Rennet dose or activity low

Check the rennet dose, its storage temperature and its expiry date.

Milk temperature below the set point at renneting

Check the vat temperature and the sensor reading before adding rennet.

Calcium or pH of the milk different

Check the milk pH and the calcium chloride addition against the recipe.

Milk quality changed

Check the incoming milk records with quality, for example after a change of supply.

Prevention: Setting time recorded for every vat.

Curd pieces uneven in size

Hits OEE: Quality

Symptoms: Cut curd has a mix of large and small pieces, so moisture varies in the cheese.

Knife frame speed or cutting time wrong

Check the cutting programme against the recipe.

Knives damaged or bent

Inspect the knife frames and straighten or replace damaged wires or blades.

Cutting started too early or late

Cut at the firmness set in the recipe, using the firmness check the plant uses.

Stirring too strong straight after cutting

Start stirring gently after the cut, as the recipe sets.

Prevention: Curd size checked visually on every vat.

Cooking temperature not followed

Hits OEE: Quality

Symptoms: The vat heats too fast, too slowly or overshoots during cooking.

Steam or hot water valve not controlling well

Have the control valve checked and tuned.

Temperature sensor out of calibration

Calibrate the vat sensor against a reference thermometer.

Jacket fouled on the water side

Clean or descale the jacket circuit.

Stirring too slow for even heating

Check the agitator speed during cooking.

Prevention: Cooking temperature curve recorded for every vat.

Agitator or knife frame drive fault

Hits OEE: Availability

Symptoms: The frames stop, run unevenly or the drive trips.

Drive overloaded by firm curd

Check the curd firmness and the speed at that step of the recipe.

Gearbox or bearing wear

Check the gearbox oil and listen for bearing noise.

Drive settings changed

Compare the drive settings with the commissioning record.

Frame fouling the vat wall

Check the frame clearance to the vat wall.

Prevention: Drive current trended per recipe.

High fines in the whey

Hits OEE: Quality

Symptoms: Small curd particles are lost in the whey and the yield falls.

Curd cut too soft

Cut at the correct firmness.

Stirring too fast early in the process

Keep early stirring gentle so the curd heals.

Knives blunt and tearing the curd

Check and repair the knives.

Pumping curd with too much shear

Check the curd pump speed and the pipework bends.

Prevention: Fines in the whey measured and trended with the yield.

Whey draining slowly

Hits OEE: Performance

Symptoms: Draining takes longer than planned and the next step waits.

Drain screens blocked with curd

Clean the screens and check their condition.

Drain valve not opening fully

Check the valve actuator.

Whey pump or line restricted

Check the whey line and pump.

Curd matting against the screen

Keep stirring during draining as the recipe sets.

Prevention: Drain time recorded per vat.

Cleaning results failing

Hits OEE: Quality

Symptoms: Swabs or visual checks fail after the vat is cleaned in place.

Spray devices blocked or not turning

Check every spray device during a cleaning run.

Cleaning solution too cool or too weak

Check temperature and concentration at the vat.

Cleaning time cut short

Check the cleaning records against the validated programme.

Knife frames shadowing areas of the vat

Position the frames as the cleaning programme requires.

Prevention: Cleaning verified before each production day.

Milk fill volume wrong

Hits OEE: Quality

Symptoms: The vat holds more or less milk than the recipe, so ingredient ratios are off.

Flow meter out of calibration

Calibrate the flow meter.

Air in the milk line giving false readings

Check for air drawn in at pumps and joints.

Level sensor fouled

Clean the level sensor.

Wrong recipe volume selected

Check the recipe at each product change.

Prevention: Fill volume checked against the meter on a schedule.

Acid development slow

Hits OEE: Quality

Symptoms: The pH falls slower than usual, delaying the make and changing the cheese.

Starter culture weak or handled badly

Check the culture storage, dosing and expiry.

Bacteriophage in the plant

Rotate cultures and follow the plant phage control plan.

Vat temperature low

Check the temperature during ripening.

Inhibitors in the milk

Check the milk testing records.

Prevention: pH logged at set points in every make.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: HTST pasteuriser · CIP system · homogeniser · mixer / agitator · disc stack separator · butter churn

Stop the same fault coming back

Recurring cheese vat stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

Book a Fabrico demo

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Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover