Atlas Copco 1616595281 O.F.S. I-21 Oil-Free Screw Element

Description

The 1616595281 is the Atlas Copco O.F.S. I-21, an oil-free screw element that fills the second-stage position of the two-stage ZR and ZT 75-90 machines. The official item text names it as the stage 2 “short” of this family, and it points every current order to the element 9825066081 together with the standard installation kit.

That ordering detail is the first thing a buyer needs, and it is not the whole picture. The stage belongs to a family that carries two second-stage builds, “short” and “long”, and the build fitted in your machine decides which number the renewal takes. This article sets out the identity of the 1616595281, the short-versus-long distinction, the machines the stage serves and the figures you need before the order.

Identity of the 1616595281 Second Stage

Second-stage elements are the larger of the two compression stages in a two-stage oil-free machine, and their identity has to be exact before an order is placed. The designation, the ordering direction and the stage data of the 1616595281 together settle that identity.

What the O.F.S. I-21 Designation Covers

O.F.S. is the element family of the oil-free screw machines: the compression stages of the two-stage ZR and ZT ranges are listed under this family, and I-21 is the official stage designation of the 1616595281. The item text adds the position and the build: the element is the stage 2 “short” of its family, the second compression stage in the machine, built in the shorter of the two lengths the family carries.

At 95.00 kg and 55 × 37 × 37 cm the element arrives as one serviced assembly, machined and set as a unit. The oil-free design keeps the compression chamber free of lubricant, so the rotors run with their premium coating and external timing gears instead of an oil film, and the serviced assembly preserves that design as delivered. The item data of the 1616595281 describes exactly this complete unit, packed and ready for the machine room.

Where Orders Go Today: the 9825066081 Element

Current orders for the stage 2 “short” of the 1616595281 are directed to the element 9825066081, and the official item text adds a condition that matters: the order includes the standard installation kit. The 1616595281 remains the reference in the documentation of installed machines, in older quotations and in maintenance systems, so both numbers keep appearing in real service work.

In practice the ordering conversation runs like this. A plant reads the code on the old second-stage element or opens the machine file, finds the 1616595281, and the renewal is then placed under the current element 9825066081 with its installation kit. Seadweer performs this match with every quotation, so the number in the machine file and the number on the order never contradict each other.

Nothing about the direction changes the machine itself. The stage 2 “short” position stays what it is, the mounting points stay the same, and the installed machine keeps the O.F.S. I-21 as its second-stage identity. The current element is simply the number the order travels under today, bundled with the kit the installation asks for.

The Short and the Long Second Stage

The ZR and ZT 75-90 family carries two second-stage builds, and the official item text of the 1616595281 names both. Understanding the distinction keeps the renewal of a two-stage oil-free machine on the right track.

Why One Machine Family Carries Two Second-Stage Builds

The second stage of this family was built in two lengths, and the machines in the field carry one or the other according to their build. The stage 2 “short” is the build described on this page, identified under the 1616595281. The stage 2 “long” is a separate element of the same family, carried under its own number 1616672281, which continues with its own installation kit.

The two builds are not interchangeable references for one order. Each build has its own element number and its own kit, and the official text keeps them apart deliberately: renewals of the short stage go to the current element 9825066081 with the standard installation kit, while renewals of the long stage go to 1616672281 with its kit. One physical check at the machine decides which path applies.

Finding Out Which Second Stage Your Machine Carries

The code on the old second-stage element is the fastest answer, because it names the exact build the machine was assembled with. Read that code, note the compressor model and serial, and send all three to Seadweer. The fitment check confirms whether the renewal belongs to the short track of the 1616595281 or to the long track of 1616672281, and the order is placed under the right number with the right kit in the same step.

This check also protects sites that run both builds. A plant with several ZR and ZT machines of this band can carry the two stage identities side by side in its maintenance system, and the tag code separates them at every renewal without any guesswork.

Machines That Use the 1616595281

The official parts documentation of the two-stage oil-free 75-90 band carries the stage 2 “short” under the 1616595281 for a defined group of machines, and the family logic of the range explains which ones.

ZR 75, ZT 75 and ZT 90

The official parts list of the ZR 75, the ZT 75 and the ZT 90 carries the short second stage under the 1616595281, together with its epoxy sibling. These are two-stage oil-free screw machines of the 75-90 band, the ZR built for water cooling and the ZT for air cooling, and in each of them the stage described on this page sits in the second compression position.

For the buyer this confirmation does the important work: the machines above are the documented home of the stage 2 “short”. A machine of this band whose second stage was built long takes the other element of the family instead, and the short-versus-long check in the section above settles that case before the order.

What One Shared Stage Position Means for Spares Planning

Within one machine, the two stages are separate renewals with separate numbers, and the maintenance system should carry them as two positions. The 1616595281 covers the second-stage short position of the 75-90 band, ordered today under the current element 9825066081 with its installation kit, while the first stage and the long second stage keep their own lines in the records.

Planning around a 95.00 kg serviced assembly also means thinking about handling before the renewal day: lifting gear, floor route and mounting clearance at the machine. The item data of the 1616595281 puts exact numbers behind that planning, and Seadweer confirms the package details and the kit contents with the quotation, so the workshop knows what arrives before it arrives.

The Second Stage in a Two-Stage Oil-Free Machine

An oil-free screw machine of this band compresses the air in two steps, and the official system description runs in a fixed order: air passes the filtration and the first stage, crosses the intercooler, and is compressed in the second stage before the aftercooler. The split exists for a thermodynamic reason, because a single oil-free compression step is limited by the temperature the air reaches, and two cooler steps move the same air more efficiently.

The second stage carries the harder half of that work. It takes air that has already been compressed once and cooled, and brings it to the final working pressure, which is why its element is a heavy, separately serviced component in its own right. The 1616595281 renews exactly this position for the machines listed above.

The oil-free design shapes the element itself. External gears keep the rotors synchronized, the rotors never touch each other or the housing, and the compression chamber stays free of lubricant so the delivered air keeps its certified oil-free quality. The serviced assembly brings rotors, housing, gears and sealing as one unit, and the surrounding components of the machine stay in place during the renewal.

Wear Signs and Renewal Timing

A second-stage element of a two-stage oil-free machine announces its aging through measured trends, and the instruments most oil-free plants already run will show them.

Reading the Trends on an Oil-Free Machine

Trends that point to element wear include rising specific energy, drifting discharge pressure, unusual noise or vibration, higher stage temperatures and changes in the air-quality readings of the machine. Because the rotors of an oil-free stage run without contact, bearing and gear condition decide the service life, and vibration analysis reads that condition early. Any one of these trends on a machine carrying the 1616595281 is a reason to inspect the second stage and plan the renewal, and Seadweer checks the trend picture against the service documentation of the 1616595281 before the renewal is scheduled.

Planning the Renewal With the Installation Kit

The renewal of the stage 2 “short” arrives as a package: the current element 9825066081 together with the standard installation kit, exactly as the official item text prescribes. The kit belongs to the renewal, so the order is placed once for both, and the workshop receives what the installation asks for in one consignment.

The real timing of the renewal follows the condition of your machine and the applicable service documentation rather than a fixed hour target. A planned second-stage renewal with the 1616595281, ordered under the current element, beats an unplanned stop, and the before-and-after energy and pressure figures give the maintenance file a clean record of the restoration. The 1616595281 stays the identity of the stage in your records while the order travels under the current element.

Technical Specifications

The tables below collect the identification and physical data of the 1616595281 in one place, exactly as the item data and the official item text list them.

Part Identification

Dimensions and Weight

The figures above are the item data of the 1616595281 for handling and logistics reference. The two tables together are the data sheet of the stage, and Seadweer repeats them with the quotation so the workshop knows what arrives before it arrives.

FAQ

What is the difference between 1616595281 and 9825066081?

They describe the same stage 2 “short” position on the machine, the position documented under the 1616595281. Current orders are directed to the element 9825066081 together with the standard installation kit.

What is the difference between the short and the long second stage?

They are the two second-stage builds of the same oil-free family. Renewals of the short stage go to the current element 9825066081 with the standard installation kit, and renewals of the long stage go to 1616672281 with its own kit.

Which machines use the O.F.S. I-21?

The official parts list of the ZR 75, the ZT 75 and the ZT 90 carries the short second stage under the 1616595281. Whether an individual machine of the 75-90 band carries the short or the long build is settled by the code on the old element tag.

How big and how heavy is the 1616595281?

The item data of the 1616595281 lists 55 × 37 × 37 cm and 95.00 kg. These figures describe the serviced element as packed, so lifting gear and a clear floor route belong on the planning sheet.

Why does an oil-free screw machine have two elements?

The air is compressed in two cooler steps instead of one hot step, with the intercooler between the stages, and each step has its own element. The second stage brings the air to the final working pressure and is renewed as a separate component.

How do I order a renewal for my machine?

Read the code on the old second-stage element and note the compressor model and serial, then send all three to Seadweer. The fitment check confirms the short or long build of your machine, and the order is placed under the current element with the correct installation kit.

More Air Ends Available

Other Atlas Copco air end models are available upon request. Please check the table below or contact us for details.