1. Preparatory Work (Safety + Environment + Materials)

Safety Isolation：
Shut down the equipment → Turn off the air compressor → Open all exhaust valves → Ensure the pressure gauge returns to zero → Cut off power, lock out and tag out.

Environmental Requirements：

Humidity: ＜60% RH, Temperature: 15–30℃, dust-free and oil-free; Operators shall wear dust masks, goggles and degreased gloves.

Materials and Tools：

Molecular Sieve: Prepare an extra 5% of the same model (e.g., CMS-220/300) based on the rated capacity on the adsorption tower nameplate; mixing different specifications is strictly prohibited.
Auxiliary Materials: Activated alumina balls (bottom cushion layer), coconut fiber mat / palm fiber mat, stainless steel wire mesh, sealing gaskets, nitrogen (≥95% purity).
Tools: Explosion-proof vacuum cleaner, vibrating rod / vibration platform, funnel, wooden mallet, alcohol, dust-free cloth, wrench, sealing grease.

II. Cleaning of Old Molecular Sieve (During Replacement)

Remove the upper/lower head of the adsorption tower, completely extract the old molecular sieve with an explosion-proof vacuum cleaner, and check that no residue remains inside the tower.

Inspect the tower wall, wire mesh, coconut pad and distributor; replace any damaged parts mandatorily.

Wipe the inner wall of the tower with alcohol-dampened dust-free cloth, then purge with oil-free compressed air to ensure no oil, water or impurities are left.

III. Loading of New Molecular Sieve (Key Procedure)

Base Laying: Place coconut mat at the bottom of the tower first → Lay 5cm activated alumina balls → Cover with stainless steel wire mesh (to prevent molecular sieve leakage).

Nitrogen Protection: Purge the tower with nitrogen of ≥95% purity to reduce oxygen content and minimize moisture absorption of molecular sieve.

Layered Loading and Compaction (Core Step)

Feed materials slowly and vertically through a funnel to avoid particle breakage caused by falling from height.

Compact with a vibrating rod or evenly knock the tower wall with a wooden hammer every 30cm of loading height; control the bulk density within 670–690g/L.

Stop loading when reaching 5cm below the lower edge of the upper flange to reserve expansion space.

Cover the top with stainless steel wire mesh and coconut mat, then install flow distribution plate and spring/cylinder pressing device to prevent displacement and pulverization during operation.

Loading Quantity Control: The error of single tower ≤±5%, the error between two towers ≤±2% to avoid gas flow bias.

Refilling Notes: Perform secondary refilling after the new molecular sieve operates for 1 month (to compensate settlement gaps); conduct inspection and refilling every 6–12 months in the later operation period.

IV. Sealing and Air Tightness Test

Clean the flange surface, replace the sealing gasket with a new one, apply sealing grease, and fasten the bolts evenly in a diagonal sequence.

Air tightness test: Maintain pressure at 0.8MPa for 30 minutes. The test is qualified if the pressure drop is ≤0.01MPa with no leakage.

V. Commissioning and Startup

Start under low load and run at no load for 1–2 hours to check that pressure and noise are within normal range.

After 24 hours, verify that nitrogen purity and flow rate meet the standards; calibrate the analyzer and confirm no leakage.

Put the system into full-load operation, and record the filling quantity, date and purity data for filing.

VI. Common Problems and Taboos

❌ Moisture Damage: Molecular sieves shall be used immediately after opening with exposure time less than 30 minutes. If damp, dry them at 150–200℃, cool down, and then reuse.

❌ Oil Contamination: Failure of the front-end refrigerated dryer and filter will cause molecular sieve poisoning and scrapping; the pre-purification system must be repaired first.

❌ Inadequate Packing: It will lead to powder spraying, reduced purity and shortened service life. Layered compaction is mandatory during packing.

How to replace and fill the molecular sieve of a nitrogen generator？

1. Preparatory Work (Safety + Environment + Materials)

Safety Isolation：Shut down the equipment → Turn off the air compressor → Open all exhaust valves → Ensure the pressure gauge returns to zero → Cut off power, lock out and tag out.

Environmental Requirements：

Materials and Tools：

VI. Common Problems and Taboos

Safety Isolation：
Shut down the equipment → Turn off the air compressor → Open all exhaust valves → Ensure the pressure gauge returns to zero → Cut off power, lock out and tag out.