1. Purpose

To standardize the daily use, maintenance, and troubleshooting procedures of the ID208 intelligent 8-hole digestion furnace, ensure stable equipment operation, precise temperature control, reliable digestion data, extend equipment service life, and prevent safety accidents, this standardized operating procedure is hereby formulated.

2. Scope of application

This procedure is applicable to the routine inspection, post-use maintenance, weekly/monthly/quarterly/annual maintenance, troubleshooting, and emergency handling of the ID208 eight-hole intelligent digestion furnace in the laboratory. It serves as the sole basis for equipment records, internal audits, and external audits. This procedure is also applicable to other models of digestion furnaces in the ID series from Shanghai Zhiyue Instrument, such as the ID-214/ID-220 intelligent digestion furnaces.

3. Equipment introduction

The ID208 intelligent digestion furnace features an integrated cast aluminum heating chamber, six-stage programmed temperature rise, intelligent PID temperature control, and overtemperature power-off protection. It is equipped with a water circulation condensation and negative pressure exhaust gas treatment system, and is primarily used for digestion treatment before Kjeldahl nitrogen determination of samples such as food, feed, grain and oil, and soil.

4. General safety requirements

4.1 All maintenance, overhaul, and cleaning operations must be conducted after the machine has been shut down and powered off, and the furnace body has naturally cooled down to room temperature.

4.2 When working with strong acids or acid mist, it is necessary to wear acid-resistant gloves, goggles, and a gas mask.

4.3 It is strictly prohibited to splash water, acid or alkaline liquids on the control panel, power supply compartment, or mainboard area.

4.4 Before heating the equipment, the exhaust pump must be turned on first. Dry burning and heating without exhaust are strictly prohibited.

5. Standardized and graded maintenance procedures

5.1 Maintenance after each use (required for operators)

5.1.1 Shutdown specifications

Stop the heating program, keep the exhaust pump running for 10 minutes, and turn off the gas, water system, and power supply after the digestion rack is placed directly above the cooling rack.

5.1.2 Cleaning of furnace cavity

Wipe the cast aluminum heating holes and the surface of the furnace body with a soft cloth soaked in a 5% to 10% dilute sodium hydroxide solution to neutralize residual acid mist. Then, wipe clean with pure water, open the cover for ventilation, and allow it to dry to prevent the aluminum body from oxidizing, turning white, and experiencing corrosion pitting. It is prohibited to scratch the oxidized layer of the heating body with steel wool or hard objects.

5.1.3 Maintenance of exhaust gas and seals

Dismantle the gas collection hood, rinse it thoroughly, and be careful not to bump the glass exhaust pipe; clean the residual acid solution on the bracket, rinse the heat-resistant small ring cover, and ensure it is well sealed without any air leaks.

5.1.4 Auxiliary system maintenance

Drain the acidic waste liquid from the exhaust pump; check the pipeline for any signs of aging, bending, or air leakage;

5.1.5 Account records

Fill in the equipment usage record, specifying the operating status and whether there are any abnormalities.

5.2 Weekly maintenance (performed by the administrator)

5.2.1 Gas path leak detection: Turn on the exhaust pump and confirm that there is no acid mist leakage or suction.

5.2.2 No-load function test: Run at 150℃ for 10 minutes without load to confirm that the temperature rise, temperature control, and alarm functions are normal.

5.2.3 Check the aging condition of pipelines, and mark damaged and hardened pipelines for replacement.

5.3 Monthly deep maintenance (performed by equipment administrator)

5.3.1 Clean the dust and acid mist condensation inside the chassis, and check the solid-state relay for any ablation or bulging.

5.3.2 Check the button functionality and parameter saving capability.

5.3.3 Clean and remove rust from the furnace lid, apply high-temperature resistant lubricating grease, and ensure smooth opening and closing.

5.3.4 Digestion verification was conducted using standard substance (ammonium sulfate) to confirm the qualified performance of the equipment.

5.4 Long-term shutdown maintenance (shutdown for more than 15 days)

5.4.1 Thoroughly clean the furnace body and pipelines, and ensure they are completely dried without any acid or alkali residue.

5.4.2 To prevent water accumulation in the glass exhaust pipe, place a drip tray to control and dry the moisture.

5.4.3 After powering off, conduct dustproof sealing and store it in a dry environment free from corrosive gases.

5.4.4 Conduct a no-load operation at 150℃ for 30 minutes every month to prevent and eliminate moisture.

6. Common faults and standardized solutions

6.1 No heating or temperature rise upon power-on

Failure causes: Open circuit of temperature sensor, damaged solid-state relay, oxidized and loose wiring terminal, heating element failure, and set temperature lower than current temperature.

Solution: Reset the program; tighten the wiring; clean or replace the thermocouple; replace the solid-state relay; return the heating element to the factory for maintenance if it is abnormal.

6.2 Inaccurate temperature display and large deviation

Failure cause: Fouling, loosening, aging of thermocouple, and drift of temperature control parameters.

Solution: Clean the probe and re-tighten it; perform temperature calibration; if the deviation exceeds the tolerance, replace the thermocouple directly.

6.3 Heating without stopping and overtemperature alarm

Failure causes: solid-state relay sticking, temperature control board out of control, thermocouple short circuit.

Solution: Immediately power off and shut down the machine; replace the relay and sensor; return the motherboard for repair if it is abnormal.

6.4 Acid mist leakage and strong odor

Failure causes: failure to activate water cooling, insufficient suction force, aging of sealing rings, and air leaks in the pipeline.

Solution: Strictly follow the order of water, gas, and then heating; replace gaskets and aging pipelines; drain the waste liquid from the pump body.

6.5 Suction pump backflow and acid water reflux

Cause of failure: The air pump is damaged.

Solution: Replace the air pump.

6.6 Screen is black and unresponsive

Failure causes: abnormal power supply, fuse failure, and damaged power board.

Solution: Replace the independent grounding power supply; replace the fuse with the same specification; return the power board to the factory if it is faulty.

6.7 Key malfunction and automatic parameter reset

Failure cause: Panel corrosion and motherboard moisture.

Solution: Clean the panel with alcohol; dry the chassis.

7. Red line prohibitions for equipment operation and maintenance

7.1 It is strictly prohibited to wash the furnace body or heat aluminum blocks with water when they are at high temperature.

7.2 It is strictly prohibited to use hard objects to polish or scratch the anti-corrosion oxide layer of the heating element.

7.3 It is strictly prohibited to initiate the heating process without water or air extraction.

7.4 It is strictly prohibited to dry-burn the furnace at high temperature for an extended period of time.

7.5 It is strictly prohibited to splash liquid on the control panel and electrical compartment.

8. List of commonly used consumables

Sealing gasket, K-type thermocouple, solid-state relay, acid and alkali resistant exhaust pipe, temperature controller.