Atlas Copco 1616580381 OFS K-21 Air End

Atlas Copco 1616580381 O.F.S. K-21 Oil-Free Screw Air End Element

Atlas Copco 1616580381 (Model: O.F.S. K-21) is an industrial quality, Class 0 oil-free rotary screw compressor element (airend) for fixed and maritime compressed air systems. The O.F.S. K-21 low-pressure (LP) element is the principal compression stage for Atlas Copco’s leading ZR and ZT series and achieves great volumetric efficiency at low tip speeds using an asymmetrical 4/6 teeth rotor geometry (Standard Atlas Profile – SAP).

This air end is constructed with rotors made of high strength alloy steel with unique anti-corrosion thermocontact coatings and encased in heavy duty ductile iron casting. It ensures 100% oil free air discharge at the most harsh operating temperatures and working pressures up to 10–13 bar. Designed for continuous heavy duty cycles on board commercial vessels, offshore platforms, chemical processing facilities and power production units.

Model Details

• Brand: Atlas Copco
• Primary Part Number (MPN): 1616580381
• Air End Code / Designation: O.F.S. K-21 (Oil-Free Screw K-21 Stage)
• Stage Identity: Low Pressure (LP) Compressor Stage Element

Main features

1. ISO 8573-1 CLASS 0 Certification Compliance: Removes the possibility of oil contamination in key operations, delivering pure air for sensitive maritime and industrial activities.
2. Asymmetrical SAP Rotor Profile (4/6 Tooth Configuration) High-rigidity female rotors decrease deflection and internal leakage backflow, while maximizing pressure ratios of 10–13 bar.
3. Dual-Stage Non-Contact Shaft Seals Reverse-threaded oil seals and stainless steel air seals are separated by an atmospheric vent hole to prevent oil from entering the compression chamber.
4. High Strength Ductile Iron Housing: Vibration-dampened cast housing designed for thermal stability at continuous duty to 200°C discharge conditions.
5. Direct Gear Drive Interface Precision ground timing gear interface for micron level rotor teeth clearances without mechanical contact.

Compatible Equipment Models

• Atlas Copco ZR Series (Water-Cooled Oil-Free): ZR110, ZR132, ZR145, ZR400, ZR400VSD, ZR500VSD.
• Atlas Copco ZT Series (Air-Cooled Oil-Free): ZT110, ZT132, ZT145
• Atlas Copco Portable Marine Units: PTS800, PTE900
• Chicago Pneumatic Equipment: Equivalent OEM oil-free gear-driven screw compressor platforms.

Primary Industrial & Marine Applications

• Marine Engine Room Service Air: Supplies oil-free pneumatic control air for main engine maneuvering, automated control valves, and soot blowers.
• LNG / LPG Gas Carriers: Pure instrument air supply avoiding chemical reactions or contamination in cargo handling control systems.
• Offshore Rig Nitrogen Generation Units: Primary feed air supplier for membrane and PSA nitrogen generator packages.
• Pharmaceutical & Medical Manufacturing: Process air demanding strict ISO Class 0 compliance.
• Electronics & Semiconductor Manufacturing: Clean room pneumatic air supply free of aerosol hydrocarbons.

Part Number Cross-References

• Atlas Copco Primary MPN: 1616580381
• Format Variations: 1616-5803-81, 1616 5803 81
• Alternative Related Stages: 1616580382, 1616-5803-82
• Compatible Service Assembly Cross-References: 1616623603 (Gear Drive), 1616585181 (O.F.S. G-21)

Marine Engineer Expert’s Guide

Chief Engineer’s Technical Inspection Protocol: When installing or swapping out an O.F.S. K-21 LP element onboard a vessel or shore plant, the single biggest cause of premature failure is non-compliance with shaft gear alignment and thermal expansion pre-checks.

Tips:

1) Protect the Rotor Coating During Storage

The O.F.S. K-21 rotors rely on micro-thin PTFE/polymer coatings to maintain internal sealing tolerances without direct metal-to-metal contact. Never introduce solvent-based degreasers into the air inlet or outlet ports during inspection. Always rotate the drive shaft manually by hand at least 5 full turns weekly while in storage to keep bearings lubricated and prevent shaft brinelling.

2) Inspect the Atmospheric Leakage Port (Seal Vent)

The intermediate chamber between the oil seal and stainless steel air seal features an external drain hole. During routine watchkeeping rounds, inspect this vent line. Traces of oil indicate oil seal degradation, whereas air blow-by indicates air seal wear. Addressing a worn seal early prevents lubricating oil from migrating into the compression cavity and ruining Class 0 air compliance.

3) Precision Drive Alignment & Gear Backlash Setting

When mounting the 1616580381 airend to the step-up gearbox housing, verify the backlash on the drive pinion gear using a dial indicator gauge. Always replace the O-rings on the oil feed and return lines, and torque casing flange bolts in a diagonal cross-pattern to exact factory specifications (check manual) to prevent housing deformation.

Frequently Asked Questions

What compressor models use the Atlas Copco 1616580381 air end?

The 1616580381 O.F.S. K-21 air end is primary installed as the low-pressure (LP) compression element in Atlas Copco ZR110, ZR132, ZR145, ZR400, ZT110, ZT132, and ZT145 oil-free rotary screw air compressors. It is also fitted on PTS800 and PTE900 portable marine/industrial units.

Is the Atlas Copco O.F.S. K-21 air end 100% oil-free?

Yes. The O.F.S. K-21 element is certified Class 0 oil-free. Compression takes place completely dry in the rotor chamber, backed by non-contact stainless air seals and reverse-thread oil seals to keep oil entirely out of the air stream.

Can I replace an O.F.S. K-21 element onboard a ship without replacing the entire compressor?

Yes, the air end is a modular component designed for individual replacement during major 24,000 to 40,000-hour overhaul intervals. Marine engineers can replace the element directly using standard rigging tools provided gear backlash and casing alignment specs are followed.

What are the shipping weight and package dimensions for P/N 1616580381?

The net weight of the element is approximately 138 kg (304 lbs). Packed in an export wooden crate, the gross shipping weight is 160 kg (352 lbs) with outer dimensions of 62 cm x 46 cm x 38 cm.