Proper Operation & Maintenance of Double-Layer Water Bath Retort Sterilizer

1. Standard Operating Procedures for Double-Layer Water Bath Retort

1.1 Pre-operation Inspection Before Startup

1. Check the integrity of power supply, steam pipelines, circulating water pumps, safety relief valves, pressure gauges and temperature transmitters; inspect the silicone sealing gasket on the retort door for cracks or foreign debris, and verify the reliable performance of the door interlock safety device.
2. Fill the upper hot water storage tank and lower sterilization chamber with softened water, keep the water level 2–3 cm below the heating pipe inlet; never overfill to avoid overflow or underfill to prevent dry burning.
3. Conduct a 30-minute no-load trial run of the water circulation system. Start formal production only after confirming zero pipeline leakage and uniform temperature distribution with temperature deviation controlled within ±1℃ between dual layers.

1.2 Product Loading & Sterilization Process

1. Load finished products into sterilization baskets with reserved gaps between packages to guarantee unobstructed water circulation, then steadily push baskets into the lower sterilization chamber.
2. Close and fasten the retort door, inflate the door sealing air cushion, and confirm full interlock locking; the door stays locked until full pressure release.
3. Temperature Rise Stage: Open connecting valves, circulation pumps and steam inlet valves to transfer preheated hot water from upper tank into lower chamber. Set target temperature (115~121℃ for common cooked food) and working pressure (0.12~0.15 MPa) per product formula; exhaust cold air thoroughly during heating to eliminate cold spots that cause incomplete sterilization.
4. Constant-temperature Sterilization Stage: Start process timing automatically once parameters reach set values. Continuously monitor real-time pressure and temperature; cut off heat supply immediately if abnormal parameter fluctuation occurs, no unauthorized adjustment of steam valves allowed.
5. Cool-down & Water Recovery: Upon finishing sterilization countdown, recover high-temperature hot water back to the upper storage tank first. Introduce cooling water gradually for staged cooling; unlock the retort door only after internal temperature drops below 60℃ and chamber pressure falls to zero for unloading.

1.3 Post-shutdown Cleaning & Wrap-up

2. Tiered Preventive Maintenance Schedule

Daily Maintenance (After Every Production Run) ✅

1. Complete tank cleaning: Scrub retort interior and basket frames with food-grade detergent and warm water to remove leftover residues, clean filter screens on circulation pipelines, drain all residual water to avoid stainless steel corrosion from standing sewage.
2. Seal gasket care: Wipe dry door sealing rings and coat with food-grade silicone oil; replace gaskets promptly once hardening or damage is spotted.
3. Pipeline inspection: Check all valves and flange connections for water/steam leakage, fasten loose fittings for minor seepage.

Weekly Maintenance (Weekly Off-production Day)

1. Circulation pump upkeep: Refill lubricating grease for pump bearings, inspect motor insulation and abnormal operating noise.
2. Instrument visual check: Confirm pressure and temperature gauges return to zero properly; send faulty instruments for calibration in advance.
3. Safety valve test: Manually lift safety valve pull tab to test smooth pressure relief and exhaust performance.

Monthly & Annual Preventive Maintenance ⚠️

• Monthly Service: Descale full set of circulating pipelines to remove internal limescale; retighten all pipeline bolts and support brackets.
• Annual Overhaul:
  1. Pressure vessel regulatory inspection: Complete external nondestructive testing yearly, internal inspection every two years and full hydraulic pressure test every three years; archive all official inspection documents.
  2. Metrological calibration: Submit pressure gauges and temperature sensors to authorized third-party labs for verification; replace components when temperature error exceeds 0.5℃.
  3. Full tank descaling: Implement food-grade circulating descaling when limescale thickness exceeds 1mm to prevent corrosion of stainless steel tank body.

3. Critical Safety Prohibitions

1. Never force open the retort door under internal pressure; door unlocking is permitted only after zero pressure and temperature below 60℃.
2. Only certified operators are allowed to run the equipment; arbitrary modification of preset temperature and pressure programs is forbidden.
3. Avoid long-term makeup with untreated tap water (high calcium/magnesium content accelerates limescale buildup); always adopt softened water to extend equipment service lifespan.

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