Description
The 1616590481 is the OFS M-21 oil-free screw element, the compression stage Atlas Copco lists for its ZR and ZT oil-free rotary screw compressors. It turns shaft power into compressed air with nothing added to the compression chamber, so the air leaving its discharge port carries no lubricant from the stage itself.
The stage carries two numbers. The item record names it as the 1616590481, and the same element is printed in the form 1616 5904 81 across Atlas Copco shipping and build documents. It supersedes 9825008481, the number it replaced across the parts records.
Packed, the 1616590481 measures 78 × 47 × 49 cm and weighs 265.00 kg, and Belgium is recorded as the country of origin. The item record lists the unit as serialized, which means a plate on each element identifies it on its own rather than by family alone. This article sets out what the 1616590481 is, which machines it is listed for, how an oil-free element compresses air, and how fitment is confirmed before an order is placed.
Identity of the 1616590481 Element
An element is the core compression stage of a screw compressor, and the 1616590481 fills that role as the OFS M-21 stage. It converts shaft power into air flow at pressure, and it is a long-life factory assembly rather than a consumable. When a stage reaches the end of its working life it is renewed as a complete unit, with the rotor pair, the housing and the bearings built as one.
The interfaces on that assembly are set by the machine it was built for, which is why the 1616590481 is ordered against a compressor record rather than against a description.
What the OFS M-21 Designation Covers
OFS is the oil-free screw designation, and M-21 is the stage code Atlas Copco records for this element. The code is quoted in the parts records exactly as it stands, and it separates the M-21 stage from the other stages of the same oil-free family.
Atlas Copco prints the same number in two forms. The ten-digit form 1616590481 is what the item record carries, and 1616 5904 81 is the printed form used on the shipping and build documents. Both name the same stage, and either one can be used when a renewal is being confirmed.
The Superseded Number 9825008481
The M-21 stage was previously recorded under 9825008481. That number is superseded by the 1616590481, and orders placed against the older number are directed to the current one. Where a machine file still carries 9825008481, it describes the same stage position.
Both numbers point to one element, so a renewal order needs only the current number together with the machine it is going into. Seadweer confirms the direction of that change against the parts records when an enquiry is handled.
Compressors That Take the 1616590481
Atlas Copco lists the 1616590481 in the parts lists for its oil-free ZR and ZT ranges, and the documented coverage runs across two families of machines built on one compression platform.
The ZR 160–275 Range
In the Atlas Copco parts list for the ZR oil-free range, the 1616590481 appears as the service stage for the ZR 160, ZR 200, ZR 250 and ZR 275. The same documentation carries the printed form of the number, so the stage is recognised from either the item record or the machine file.
These are large stationary oil-free machines built for plants that cannot allow lubricant into the air they produce. The stage is the point in the package where that condition is set.
The ZT 160–275 Range
The ZT range shares the compression platform, and the 1616590481 appears as the oil-free stage in the parts lists covering the ZT 160, ZT 200, ZT 250 and ZT 275. Those lists record the element as O.F.S., the same designation used across the oil-free screw family.
Between the two ranges the documented coverage reaches eight models. All of them are oil-free stationary screw compressors, and all of them draw the stage from the same part number.
The ZR-6-52 Installation
That coverage is not limited to the standard range lists. A documented installation record for the Atlas Copco ZR-6-52 names the 1616590481 as the high-pressure element stage for that machine, alongside a low-pressure stage drawn from a different number.
The record identifies the individual compressors by serial number, which ties the part number to specific machines rather than to a range alone. It is the kind of evidence a maintenance file can be built on.
Why Fitment Is Confirmed per Machine
The ZR and ZT 160–275 platform does not draw on a single oil-free stage number. The parts lists for these machines also name other O.F.S. elements, and which one applies depends on the generation, the configuration and the pressure of the individual build.
That is why the 1616590481 is confirmed from the parts list for a machine serial number rather than from the model alone. Two machines under the same model name can carry different stage numbers, and the parts list is the record that settles which one is right.
What the Oil-Free Screw Element Does
Oil-free compression starts from a single condition: nothing inside the compression chamber of the 1616590481 lubricates the rotors. Everything about the way the stage is built follows from that requirement.
The Rotor Pair Without an Oil Film
The rotor pair turns in a precision-bored housing with the running gap held small enough to seal the pocket, and the two rotors stay apart instead of riding on each other. With no oil film carrying the load, timing gears at the drive end hold the pair in phase.
An anti-friction coating on the rotor surfaces protects them inside that non-contact gap, precision rolling bearings take the radial and thrust loads of the shafts, and a shaft seal keeps gear-end lubrication on the gear side of the 1616590481. The result is an air path with no lubricant to remove, and everything downstream of the discharge port inherits the quality the stage delivers.
The High-Pressure Position in a Two-Stage Unit
Oil-free packages of this size compress in two stages with intercooling between them, and the two positions take different elements. The 1616590481 is documented as the high-pressure stage, the second compression step where air already compressed once is brought to final pressure.
That position sets the discharge conditions of the whole package, and the stage built for it carries the port arrangement and the drive interface of the high-pressure side. It does not move to the low-pressure position unless the parts list for the machine says it does.
Serialization and Traceability
The item record lists the 1616590481 as serialized, and that status shapes how the stage is handled from the build record through to the machine file. A serialized element is not tracked as a quantity of identical parts; it is tracked as an individual unit.
Reading the Housing Plate
The plate on the housing is where that identity is read. It carries the part number and a unit number, and the same number appears in the printed form 1616 5904 81 across the shipping and build documents.
Between the two, the unit number is the more specific. It links the stage to the record it was built under and to the compressor it was fitted to, which is the detail a machine file needs.
The Unit Number in the Machine File
Where several machines of one model stand side by side, the unit number is what keeps their histories apart. It records which stage is in which machine, and it makes the next renewal enquiry a matter of reading a file rather than opening a housing.
The same number carries back to the build record of the 1616590481, which is why it is worth logging at the moment of fitment rather than at the next service interval.
The Scale of the M-21 in the Package
At 265.00 kg and 78 × 47 × 49 cm, the 1616590481 is a stage that is planned for rather than lifted by hand. The figures describe the unit as it is supplied, and they shape the route from the unloading point to the machine before the fitting day arrives.
Dimensions and Packing
The envelope decides the access path. A stage of this size reaches the machine on a pallet or in a case, and the openings it has to pass are measured in advance: doorway widths, lift capacity and the turning space in front of the machine.
The lifting gear is matched to the 265.00 kg of the 1616590481, and the slinging is arranged so the load stays level through the move. The pallet quantity is recorded as one, so the unit travels as a single package.
Rigging and Setting Down
The stage is carried on its mounting faces and never on its shaft. Lifting points stay on the housing, and the unit is set down on a surface that will take its weight. The port caps stay in place until the moment of fitment, so nothing reaches the bore of the 1616590481 while it is exposed.
A second pair of hands at the machine is worth planning for. Setting a stage of this mass onto its faces is a controlled two-point operation, and the same care covers the removal of the unit being renewed.
Alignment and the First Run
Before the machine is closed up, the mounting faces are cleaned and checked for burrs, the coupling or the belt layout is inspected for wear, and alignment and direction of rotation are confirmed. Once running, the machine is brought up unloaded and watched while the readings settle.
Discharge temperature, pressure and vibration at the bearing housings are logged through the first running period, and the coupling and mounting fasteners are re-torqued after the first hours. That short log becomes the baseline for every later check on the 1616590481.
Wear Signs and Renewal Timing
Renewal of the 1616590481 is decided on condition rather than on a fixed hour count. Two lines of evidence carry most of that decision, and both of them read best as trends taken at a fixed interval rather than as single figures.
Possible Warning Signs
The rotor coating is what changes first. As it wears, the running gap opens and the stage delivers less air at the same shaft power, so a falling free air delivery measured at the rated pressure is the reading that follows that change. Discharge temperature at a steady load moves with it.
Three further readings carry the same story:
- More power drawn for each unit of air delivered at a steady load, which separates a worn 1616590481 from a machine whose demand has changed.
- Vibration at the bearing housings, read at a fixed interval so the level forms a trend rather than a single figure.
- Noise around the stage, which moves with bearing condition and is worth recording alongside the vibration figures.
Timing the Renewal
Left unchecked, bearing fatigue can end with the rotors touching, and at that point the stage is written off rather than renewed. A planned renewal avoids that outcome, because the unit is changed while the frame, the drive and the pipework are still in good order.
The unit number recorded in the machine file is what makes that timing judgement easier, since it ties the readings to a known stage rather than to a model in general.
Ordering the 1616590481 Through Seadweer
Two pieces of information lock the order down: the number on the stage being renewed, which reads 1616590481 or 1616 5904 81 in the printed form, and the model and serial number from the compressor nameplate. The nameplate matters because stage position and port arrangement differ across the builds that use this element family.
Machine Record Check
Send both to Seadweer and the parts desk checks the number against the machine record and confirms the 1616590481 in one pass. 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 several compressors 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 1616590481 is quoted.
What the Quotation Confirms
The quotation repeats the item data of the 1616590481: the stage designation, the packed size, the weight, the country of origin and the tariff code. One confirmation covers the whole renewal, so the workshop plans the lift and the stop without a second enquiry for the same stage.
Send the machine details with the enquiry and the answer comes back with the fitment already checked. That is the whole of the ordering process for a 1616590481 renewal.
Technical Specifications
The tables below collect the identification data and the physical figures recorded for the 1616590481.
Part Identification
| Item number | 1616590481 |
| Designation | OFS M-21 |
| Printed form | 1616 5904 81 |
| Supersedes | 9825008481 |
| Compression type | Oil-free rotary screw |
| Product group | PCZA |
| Serialized | Yes |
Dimensions and Weight
| Dimensions (L × W × H) | 78 × 47 × 49 cm |
| Weight | 265.00 kg |
| Pallet quantity | 1 |
| Country of origin | Belgium |
| Customs tariff code | 8414900090 |
The 265.00 kg weight and the 78 × 47 × 49 cm envelope describe the 1616590481 as it is supplied, and they set the handling plan for the fitting day. Seadweer confirms the current package details with the quotation.
FAQ
What is the 1616590481?
The 1616590481 is the OFS M-21 oil-free screw element, the compression stage Atlas Copco lists for its ZR and ZT oil-free ranges. It is a complete factory assembly renewed as a unit rather than rebuilt in place.
What does the 1616590481 supersede?
The stage was previously recorded under 9825008481. That number is superseded by the 1616590481, and orders placed against the older number are directed to the current one.
Which compressors take the 1616590481?
Atlas Copco parts lists name it as the service stage for the ZR 160, ZR 200, ZR 250 and ZR 275, and for the ZT 160, ZT 200, ZT 250 and ZT 275. A documented installation record also ties it to the ZR-6-52 as a high-pressure element stage.
Where does the M-21 sit in a two-stage unit?
It is the high-pressure stage, the second compression step in a two-stage oil-free package. The low-pressure position draws a different element, so the two are ordered by their own numbers.
How heavy is the 1616590481?
The item data lists 265.00 kg in a 78 × 47 × 49 cm package, so the move is planned with lifting gear rated for that mass. The 1616590481 is carried on its mounting faces and never on its shaft.
How do I order a renewal for my compressor?
Read the number on the stage being renewed and note the model and serial number from the compressor nameplate. Send both to Seadweer and the fitment is confirmed against the parts list for that machine before the order is placed.
Other Atlas Copco Parts List
If other Atlas Copco air compressor parts are needed, more models are shown in the table below. Check it, or reach out to us and we will assist you.
| Part Number | Part Name | Part-Number |
|---|---|---|
| 1616590482 | O.F.S. M-22 | 1616-5904-82 |
| 1616590483 | O.F.S. M-23 | 1616-5904-83 |
| 1616590463 | O.F.S. M-26 | 1616-5904-63 |
| 1616589181 | STAGE | 1616-5891-81 |
| 1616585187 | ELEMENT COMPR. | 1616-5851-87 |
| 1604025201 | PLATE | 1604-0252-01 |
| 2235567620 | RESISTOR SET IP54 | 2235-5676-20 |
| 1002277101 | DISC-VALVE | 1002-2771-01 |
| 2235103900 | CRANKSHAFT | 2235-1039-00 |
| 1650121002 | SEAL HOUSING | 1650-1210-02 |
| 1900208510 | CUBICLE SF15D 380-400V | 1900-2085-10 |
| 1613140502 | FLEXIBLE | 1613-1405-02 |
| 1630800937 | CONTRAPESO CIGUEYAL VE-4/VA-60 | 1630-8009-37 |
| 1312100644 | SMARTBOX GA5-175PSI, | 1312-1006-44 |
| 1622859200 | PIPE BYPASS | 1622-8592-00 |
| 1901620938 | KIT 1+ FOR RECEIVER | 1901-6209-38 |
| 2204197888 | BACK PLATE 18,5-22 KW DI30 | 2204-1978-88 |
| 1310032274 | ADJUSTER ASY | 1310-0322-74 |
| 9753553340 | SILENCER BDER-30-008-060 | 9753-5533-40 |
| 1617901304 | CONNECTION PLATES | 1617-9013-04 |
| 2235785547 | SUPPORT MOTOR | 2235-7855-47 |
| 2205020241 | WIRE H. A9-A10 230V CE FC | 2205-0202-41 |
| 2252634100 | CORE | 2252-6341-00 |
| 1089931401 | CONNECTOR | 1089-9314-01 |
| 1623076080 | BAFFLE | 1623-0760-80 |
| 1900340186 | CONTROL PANEL-FILME COMPRESSOR | 1900-3401-86 |
| 2253807800 | COUPLING-DRIVE | 2253-8078-00 |
| 3001516600 | THERMOSTATIC VALVE KIT (AIR) | 3001-5166-00 |
| 1623554280 | PLATE | 1623-5542-80 |
| 1613949900 | ELEMENT-COUPLING | 1613-9499-00 |
| 1900500205 | CUBICLE COMPLIST AD1600 | 1900-5002-05 |
| 1625157413 | DOOR ASSEMBLY(BACK) | 1625-1574-13 |
| 9828413403 | CUBICLE TRANSF. DRYER 500V | 9828-4134-03 |
| 1901066388 | PIPE (HTA3000 TO HDDP970) | 1901-0663-88 |
| 1613490500 | STRIP | 1613-4905-00 |
| 9828443544 | CUBICLE A20 460/60 5002 UL | 9828-4435-44 |
| 1129706553 | HEAVY DUTY KIT | 1129-7065-53 |
| 1310047600 | ROOF | 1310-0476-00 |
| 1310044112 | PANEL ASY | 1310-0441-12 |
| 1089072061 | CONTACT BLOCK GND FOR SWITCH | 1089-0720-61 |
| 2901008200 | KIT-SERVICE | 2901-0082-00 |
| 0575021544 | HOSE ASSEMBLY | 0575-0215-44 |
| 0347610300 | CLAMP-HOSE | 0347-6103-00 |
| 1613243004 | BRACKET | 1613-2430-04 |
| 1089922145 | CONTACTOR | 1089-9221-45 |
| 1202961700 | GASKET | 1202-9617-00 |
| 1622031780 | FAN ASSY | 1622-0317-80 |
| 1089070216 | VALVE SOLENOID | 1089-0702-16 |
| 2250998300 | DOOR | 2250-9983-00 |
| 1901013115 | Bottom | 1901-0131-15 |
Ahmed Bin Salem –
We renewed the high-pressure stage on our ZR package and ordered the 1616590481 against the machine number rather than against the model name. Seadweer checked the fitment against the record for that build before the order was placed, and the stage that arrived carried a housing plate of its own that went straight into the machine file. It was set down on its mounting faces with the port caps still fitted, and the first run held discharge temperature and vibration where we record them on a new stage.