Atlas Copco 1616580381 OFS K-21 Oil-Free Screw Element

Description

The 1616580381 is the OFS K-21 oil-free screw element, the compression stage that Atlas Copco supplies for oil-free rotary screw compressors. It converts drive power into compressed air with no oil at all in the compression chamber, and every part of the package downstream of its discharge port works with the air it produces.

The element is recorded under three numbers in total, 2911991100, 2911990300 and 1616580381, and the last of them is the number an order is placed against today. Packed, the stage measures 62 × 46 × 38 cm and weighs 138.00 kg, with Belgium recorded as the country of origin.

What the 1616580381 OFS K-21 Element Is

An element is the core compression stage of a screw compressor. It is the part that turns shaft power into air flow at pressure, and it is a long-life component rather than a consumable filter or a charge of lubricant.

When a machine reaches the point where the element itself has to be renewed, the replacement arrives as a complete factory assembly, with the rotor pair, the housing and the bearings built as one unit. The interfaces on that unit are the ones the host machine was built around, which is why the stage number is matched against the machine rather than against the family name.

The item data lists the 1616580381 as OFS K-21 and classifies it under rate group S3L, Oil free screw, Element. That rate group places the part in the compressor parts classification as an oil-free compression element, and it is the class an order travels under. The same record names Belgium as the country of origin and carries the customs tariff code 8414900090. The element is recorded as serialized, so each unit carries its own number and can be traced back to the record it was built under.

The OFS K-21 Designation

OFS stands for oil-free screw, the compression principle this element uses. The K-21 code is the stage designation Atlas Copco records for this element, and it is what separates the K-21 stage from the other stages in the same oil-free family. The designation is quoted in the parts records exactly as it appears here, and it is the first reference to match when a replacement is being confirmed.

Two Legacy Numbers Behind the 1616580381

The current 1616580381 replaces two earlier references at once. The first is 2911991100, a number still present in service files written before the present listing was introduced. The second is 2911990300, the later of the two intermediate references. Atlas Copco directs both of them to the same current number, so a renewal documented under 2911991100 or under 2911990300 is ordered today as the 1616580381.

In practice the chain shows up as follows. A machine file that names 2911991100, a quotation from an earlier year that names 2911990300, and a current enquiry for the K-21 element all describe the same position in the machine, and all of them end at the same stage. Whichever of the three numbers the paperwork carries, the order conversation starts with the 1616580381, and the older references stay in the record beside it so the next renewal begins from a confirmed basis.

Oil-Free Compression in the K-21 Element

An oil-free screw element runs with no oil at all in the compression chamber. Two helical rotors turn in opposite directions inside a precision-bored housing, and the gap between the rotors, and between the rotors and the bore, is held small enough to seal the compression pocket without contact. Nothing lubricates the rotor surfaces from the air side, and that is what keeps the air delivered by the 1616580381 clean at the source rather than at a filter downstream of the stage.

Because there is no oil film to carry the load, the rotor pair is held in phase by timing gears at the drive end of the stage, and the rotors carry an anti-friction coating that protects the surfaces as they run in that non-contact gap. Precision rolling bearings take the radial and thrust loads of the rotor shafts. A shaft seal keeps the gear-end lubrication on the gear side of the element, away from the air path through the 1616580381.

The absence of oil also changes how the element is judged in service. There is no oil circuit to sample and no separator performance to read in connection with it, so the evidence of condition comes from the machine as a whole. Air delivery at the rated pressure, discharge temperature at a steady load, power drawn for each unit of air and vibration at the bearing housings are readings a plant already takes, and they belong to the 1616580381 even though they are measured on the package.

Where the 1616580381 Sits in the Machine

The stage is the air end of the compressor package. It sits at the drive end, where the motor or the drive coupling turns the rotor shaft, and it carries both the drive interface and the mounting faces that locate it on the machine frame. Air reaches the inlet port after the inlet filter or silencer, and it leaves the discharge port towards the aftercooler and the air treatment line. Everything between those two ports is the work of the 1616580381.

Oil-free machines are often built with more than one compression stage, with intercooling between them, and the position a given element fills is fixed by the build of the machine. That is why the stage number is checked against the machine record rather than against the family name on its own. A stage taken from one position is not interchangeable with a stage from another position unless the parts list for that serial number says so.

The interfaces on the 1616580381 are what a replacement has to match: the shaft end that takes the drive, the faces of the ports, and the mounting faces that set its position in the frame. Alignment is set on the machine side of the job, and it is confirmed before the first turn rather than after the first run.

Wear Signs and Condition-Based Renewal

An oil-free element is renewed on condition rather than at a fixed hour count. The coating on the rotor surfaces is the part that changes first, because as it wears the running gap opens and the stage loses some of its ability to hold pressure and volume at the same shaft power. A drop in free air delivery at the rated pressure, a rise in discharge temperature under the same load and ambient, and more power for each unit of air are the readings that show it.

Vibration measured at the bearing housings and the noise level around the 1616580381 add a second line of evidence. Bearing fatigue develops over a long period, and a single reading taken at one point says little on its own. Recorded at a fixed interval, the same reading becomes a trend, and the trend is what turns an unplanned stop into a scheduled one.

Left alone, bearing fatigue can end with the rotors touching and seizing, and at that point the element is written off rather than repaired. A planned renewal of the 1616580381 avoids that outcome, because the stage is changed while the machine frame, the drive and the pipework are still in good order. The element is the one spare-part order where the model name alone is not enough to confirm the match.

Handling and Fitting a 138 kg Element

At 138.00 kg in a 62 × 46 × 38 cm box, the 1616580381 is a lifting job with a clear route from the store to the machine. Those figures belong on the plan for the fitting day, and the stage is moved on its mounting faces rather than rolled onto its shaft. The protective caps stay on the ports until the moment of fitment, because grit or moisture on the rotor surfaces or in the bore causes damage on the first start that cannot be undone.

The machine side of the job matters in the same way. The mounting faces are cleaned and checked for burrs, the coupling or the belt layout is inspected for wear, and the alignment and the direction of rotation are confirmed before the 1616580381 is turned. Seals and gaskets are renewed with the stage rather than carried over from the old one.

Once the element is in place and the machine is closed up, the unit is run unloaded under observation. Discharge temperature, pressure and vibration at the bearing housings are watched through the first running period, and the coupling and mounting fasteners are re-torqued after the first hours. A short log of those readings becomes the baseline for every later check on the 1616580381.

Ordering the 1616580381 Through Seadweer

Two pieces of information lock the order down: the number on the element being replaced, which reads 1616580381, 2911991100 or 2911990300, and the model and serial number on the compressor nameplate. The nameplate matters because stage position and port arrangement differ across the builds that use this element family, and the parts list for that serial number is the record that settles it.

Send both to Seadweer and the parts desk checks the number against the machine build and confirms the match in one pass, without a second round of questions. Where the number on the old stage has worn away, the nameplate is enough on its own, because the parts list for the machine names the stage it was built with.

Plants that run more than one compressor keep a short record for each machine: model, serial number and stage number. That record turns the next enquiry into a single message with a confirmed answer, and it is the same record the parts desk works from when the 1616580381 is quoted.

Technical Specifications

The tables below collect the identification data and the physical figures recorded for the 1616580381.

Part Identification

Dimensions and Weight

The 138.00 kg weight and the 62 × 46 × 38 cm box describe the 1616580381 as packed, and they set the handling and transport plan for the fitting day. Seadweer confirms the current package details with the quotation.

FAQ

What is the difference between 1616580381, 2911991100 and 2911990300?

They are one element listed under three numbers from different periods. The 2911991100 is the oldest reference, 2911990300 came after it, and 1616580381 is the current number that an order is placed against today.

Which compressors use the 1616580381 element?

The 1616580381 belongs to the oil-free rotary screw family, which covers stationary oil-free compressors such as the ZR and ZT ranges. Stage position and port arrangement differ across those builds, so the parts list for your machine serial number is the record that confirms the match.

How heavy is the 1616580381 and how is it packed?

The item data lists 138.00 kg and a packed size of 62 × 46 × 38 cm. At that weight the element is handled with lifting gear on a planned route rather than by hand.

What are the signs that the element needs renewal?

Possible signs can include falling free air delivery at the same rated pressure, rising discharge temperature, more power for each unit of air, and growing vibration at the bearing housings. Because the compression chamber runs without oil, there is no oil sample to read from the element itself.

Can an oil-free element be rebuilt instead of replaced?

The rotor surfaces carry an anti-friction coating, and the running gap depends on that coating and on the bearing set. A complete 1616580381 stage returns the machine to its original specification in one step, while a rebuild keeps the original rotors and housing. The choice follows an inspection of the rotor surfaces and the bore.

How do I order a replacement for my compressor?

Read the number on the element being replaced, which reads 1616580381, 2911991100 or 2911990300, and note the model and serial number from the compressor nameplate. Send both to Seadweer and the fitment is confirmed before the order is placed.

More Parts List

If you need other Atlas Copco air compressor parts, we provide more models in the table below. Please check it or contact us for details.