Atlas Copco ZT 90 VSD (FF VSD⁺) Oil-free Air Compressor

The Atlas Copco ZT 90 VSD is a 90 kW (120 hp) air-cooled oil-free screw compressor published at 8.6 and 10.4 bar(e) on a single-inverter platform, with a second, dual-inverter ZT 90 VSD⁺ platform offered as Pack and Full Feature builds. One detail shapes the selection: at both pressure classes the Minimum row prints the same 75–252 l/s band, so the question is not where the low-flow end sits but how the classes diverge as pressure climbs. Heat leaves with the cooling air rather than a water circuit, which is why the ZT 90 VSD suits halls without a tower.

Where the Two ZT 90 VSD Pressure Classes Part Company

Each class is written as three points: Minimum at the lowest working pressure with its flow band, Effective at the 7 or 9 bar(e) point, and Maximum at rated pressure. The ZT 90 VSD carries a 90 kW (120 hp) motor across both classes, and the table keeps the metric and imperial figures beside the Standard and FF weights printed for the machine.

The shared Minimum band is the notable part of the ZT 90 VSD data. Both the 8.6 bar(e) and 10.4 bar(e) Minimum rows begin at 75 l/s and reach 252 l/s, with the imperial column at 160–535 cfm and 159–534 cfm. From Effective onward the classes move apart: the 8.6 bar(e) row holds 75–252 l/s, while the 10.4 bar(e) row opens at 74 l/s and closes at 232 l/s. At Maximum the gap is sharper, because the higher class starts at 96 l/s against 74 l/s and finishes at 217 l/s rather than 235 l/s.

A plant near full pressure reads those Maximum rows first; a plant with long part-load hours finds the same 75 l/s floor in either ZT 90 VSD class.

The ZT 90 VSD⁺ Pack and Full Feature Envelope

The ZT 90 VSD⁺ uses two NEOS inverters across the two compression stages, and its 10.4 bar(e) table splits into Pack and Full Feature (iMD) builds, each listed at Minimum, Effective at 7 bar(e), a 9 bar(e) point, and Maximum. These figures come from a separate data sheet with their own measured values, so the ZT 90 VSD⁺ rows sit apart from the single-inverter table above.

The Pack Minimum is 79–292 l/s at 4 bar(e) and the Pack Maximum is 76–223 l/s at 10.4 bar(e). The Full Feature (iMD) rows repeat the same bands point for point, with the Minimum quoted at 6 bar(e) instead of 4 bar(e); that shift matters when a plant sets a low-pressure interlock. The ZT 90 VSD⁺ keeps the 90 kW (120 hp) motor, and 10.4 bar(e) is the pressure class published for this air-cooled build.

What the Rotary Drum Dryer Adds to the Canopy

Specifying the ZT 90 VSD with the FF build puts the dryer inside the same canopy, so treated air leaves one frame and the plant connects a single air main. On the ZT 90 VSD data sheet the FF column carries 2700 kg against 2100 kg for the Standard machine, a 600 kg difference belonging to the frame rather than an external tower. The rotary drum splits its surface between drying and regeneration, letting treated air leave continuously.

On the ZT 90 VSD⁺ table the FF (iMD) build states its Minimum at 6 bar(e), the printed consequence of the internal air treatment path. Both belong in the layout drawing: the ZT 90 VSD FF build is longer and heavier than the Standard frame.

Air Cooling, Frame Sizes, and Measured Sound

The ZT 90 VSD rejects heat to the room air, so no cooling water circuit, tower, or pump set enters the scope. The ZT 90 VSD single-inverter table states 76 dB(A) at the work station, while the ZT 90 VSD⁺ is published at 65 dB(A); both are work-station values an operator position can be checked against. Weight separates the two platforms clearly.

The ZT 90 VSD Standard frame is 2100 kg and its FF frame 2700 kg, against 2795 kg for the ZT 90 VSD⁺ Pack and 3445 kg for the FF (iMD) build. Published lengths are 3400 mm for the Pack and 4085 mm for the FF frame, with 1660 mm width and 2000 mm height on the Pack. A slab, a doorway, and a duct route are all checked against the ZT 90 VSD build actually ordered, not against the smallest figure printed anywhere in the family.

Plants That Specify the ZT 90 VSD

Oil-free air matters wherever the compressed stream touches a product or a surface to be sealed. The ZT 90 VSD appears in filling halls, pharmaceutical packing rooms, electronics assembly, and finishing lines where a downstream filter would otherwise be the last defence against lubricant. Being air cooled, the ZT 90 VSD lets plants without a water loop specify oil-free air without a tower. The 8.6 bar(e) class suits headers near 7 bar(e), the 10.4 bar(e) class serves lines needing headroom above 9 bar(e), and the ZT 90 VSD⁺ adds a second inverter for duty that spends long hours away from full load.

Questions Buyers Ask About the ZT 90 VSD

Do the two pressure classes of the ZT 90 VSD start at the same flow? Yes. Both Minimum rows print 75–252 l/s, at 160–535 cfm and 159–534 cfm. They separate from Effective onward, and the clearest gap is at Maximum, where the 10.4 bar(e) row begins at 96 l/s instead of 74 l/s.

Does the FF (iMD) build of the ZT 90 VSD⁺ alter the flow figures? The bands are identical to Pack: 79–292, 79–277, 78–246, and 76–223 l/s. The printed difference is the Minimum pressure, 6 bar(e) for the FF (iMD) build and 4 bar(e) for the Pack ZT 90 VSD⁺.

How loud is the ZT 90 VSD beside the line? The single-inverter table states 76 dB(A) and the ZT 90 VSD⁺ table 65 dB(A), both measured at the work station, so they read directly against a plant’s operator-position limit.

From the ZT 90 VSD to the ZT 110 VSD

When a demand profile grows past the 96–217 l/s Maximum row of the ZT 90 VSD at 10.4 bar(e), the next frame up is the Atlas Copco ZT 110 VSD, with a 110 kW (150 hp) motor and its own 8.6 and 10.4 bar(e) tables plus a VSD⁺ branch. That step is worth making only after the ZT 90 VSD rows are read against the real header, because a plant that never leaves the 7 bar(e) region gains nothing from a larger frame. Where the capacity is needed, the ZT 110 VSD keeps the same air-cooled arrangement and the same Pack or FF choice.

Before the ZT 90 VSD or the ZT 110 VSD is settled, send us the model you run today and the working pressure your process holds; we will confirm whether the 8.6 bar(e) class, the 10.4 bar(e) class, or the ZT 90 VSD⁺ branch applies, then quote the configuration against those rows. That keeps the ZT 90 VSD specification tied to published figures and checks frame size, sound level, and air treatment in advance.