Atlas Copco 1616635681 OFS Q-21 Oil-Free Screw Element

Description

The 1616635681 is the OFS Q-21 oil-free screw element, the compression stage Atlas Copco builds for 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.

This is one of the larger stages in the oil-free screw range. Packed, the 1616635681 measures 126 × 86 × 85 cm and weighs 904.00 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 1616635681 is, how an oil-free element produces air with no lubricant in the chamber, what its physical scale means for handling, how fitment is confirmed and how the order is placed.

What the 1616635681 OFS Q-21 Element Is

An element is the core compression stage of a screw compressor, and the 1616635681 fills that role as the OFS Q-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. Two stages can share a designation and still fill different positions on different builds, so the match is confirmed from the compressor record rather than from the code on the casting. That is why the 1616635681 is ordered against a machine rather than against a description.

The OFS Q-21 Designation

OFS is the oil-free screw designation, and Q-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 Q-21 stage from the other stages of the same family. It is the first reference to check when a renewal of the 1616635681 is being confirmed.

The Plate on the Housing

The item record lists the 1616635681 as serialized, and the plate on the housing is where that is read. It carries the part number and a unit number, and the same number appears in the printed form 1616 6356 81 across the shipping and build documents. Both forms name the same stage.

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. Where several machines of one model stand side by side, the unit number is what keeps their histories apart.

How an Oil-Free Screw Element Compresses Air

Oil-free compression starts from a simple condition: nothing inside the compression chamber of the 1616635681 lubricates the rotors. 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 rotor 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 1616635681.

The result is an air path with no lubricant to remove. Plants that run oil-free screw units work to air quality classes where oil must not enter the air at all, and the compression stage is the point where that condition is set. Everything downstream of the discharge port inherits the quality the stage of the 1616635681 delivers.

The Scale of the Q-21 in the Package

At 904.00 kg and 126 × 86 × 85 cm, the 1616635681 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 904.00 kg of the 1616635681, and the slinging is arranged so the load stays level through the move.

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 1616635681 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 replaced. The 1616635681 is handled the same way on the way out as on the way in.

Fitment and the Machine Record

An oil-free package compresses in one stage or in two, with intercooling between them, and the position the 1616635681 fills is fixed by the build of the machine. On a two-stage unit the low pressure and high pressure positions take different stages, and each of them is ordered by its own number.

Interfaces the Renewal Must Match

The shaft end that takes the drive, the faces of the inlet and discharge ports and the mounting faces that set its position in the frame are all part of that build. A stage made for one position carries the port arrangement and the drive interface of that position, so the 1616635681 does not move to another position unless the parts list for the serial number says it does.

Air reaches the inlet after the filter and leaves the discharge towards the aftercooler and the treatment line, which puts the stage at the centre of the air path through the package. Seals and gaskets are renewed with the 1616635681 rather than carried over from the unit coming out.

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 1616635681.

Condition Signals Before a Renewal

Renewal of the 1616635681 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.

Air-Side Readings

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 free air delivery measured at the rated pressure is the reading that follows that change. Discharge temperature at a steady load moves with it.

A stage that has to work harder for the same output draws more power for each unit of air. Recorded beside the delivery figure, that reading separates a worn 1616635681 from a machine whose demand has simply changed.

Mechanical Readings

Vibration at the bearing housings and the noise level around the 1616635681 form the second line of evidence. Bearing fatigue develops slowly, and a single measurement says little on its own; taken at a fixed interval, the same reading becomes a trend.

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 the timing judgement on the 1616635681 easier.

Technical Specifications

The tables below collect the identification data and the physical figures recorded for the 1616635681.

Part Identification

Dimensions and Weight

The 904.00 kg weight and the 126 × 86 × 85 cm envelope describe the 1616635681 as it is supplied, and they set the handling plan for the fitting day. Seadweer confirms the current package details with the quotation.

Ordering the 1616635681 Through Seadweer

Two pieces of information lock the order down: the number on the stage being replaced, which reads 1616635681 or 1616 6356 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.

What to Send with the Enquiry

Send both to Seadweer and the parts desk checks the number against the machine record and confirms the 1616635681 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 1616635681 is quoted.

What the Quotation Repeats

The quotation repeats the item data of the 1616635681: 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.

FAQ

What does the unit number on the 1616635681 record?

The item record lists the stage as serialized, so each 1616635681 carries a part number and a unit number on its housing plate. The unit number links the stage to its build record and to the machine it was fitted to, and it is the reference to log in the machine file after a renewal.

Which compressors take the OFS Q-21 stage?

The OFS Q-21 belongs to the oil-free rotary screw family, which covers stationary oil-free compressors. Stage position and port arrangement differ across those builds, so the parts list for your machine serial number is the record that confirms the 1616635681 for your position.

How is a 904.00 kg element handled on site?

The item data lists 904.00 kg in a 126 × 86 × 85 cm package, so the move is planned with lifting gear rated for that mass and an access route measured in advance. The 1616635681 is carried on its mounting faces and never on its shaft.

Does an oil-free element ever need oil?

No oil enters the compression chamber of the 1616635681. The rotor pair runs in a non-contact gap held by timing gears, and gear-end lubrication stays behind the shaft seal, away from the air path.

What readings show that the stage is due for renewal?

Possible signs can include falling free air delivery at the rated pressure, rising discharge temperature at a steady load, more power for each unit of air, and growing vibration at the bearing housings. Recorded at a fixed interval, those readings form the trend the decision is based on.

How do I confirm the right stage for my machine?

Read the number on the stage being replaced and note the model and serial number from the compressor nameplate. Send both to Seadweer and the fitment is confirmed against the machine record before the order is placed.

More Air Compressor Parts List

If you require other Atlas Copco air compressor parts, additional models can be found in the table below. Please review it or contact us for details.