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

The Atlas Copco ZR 90 VSD is a 90 kW (120 hp) water-cooled oil-free screw compressor with three published layers: a single-inverter VSD table at 8.6 and 10.4 bar(e), a dual-inverter ZR 90 VSD⁺ table covering Pack, iMD, and iMDG builds, and a separate 13 bar(e) envelope. That last layer is measured on its own rows and cannot be read off the 10.4 bar(e) figures. Compression heat goes to the site’s water circuit, so the ZR 90 VSD asks for a tower, a closed loop, or a heat recovery connection instead of room ventilation.

Reading the 8.6 and 10.4 bar(e) Rows of the ZR 90 VSD

The single-inverter ZR 90 VSD table gives three points per class: Minimum at the lowest working pressure with its flow band, Effective at the 7 or 9 bar(e) point, and Maximum at rated pressure. A 90 kW (120 hp) motor is installed across both classes, and the data sheet prints Standard and FF weights beside the flow columns.

The two Minimum rows of the ZR 90 VSD coincide at 76–259 l/s, with the imperial column at 161–548 cfm for 8.6 bar(e) and 161–549 cfm for 10.4 bar(e). Divergence begins at Effective, where the 8.6 bar(e) class holds 75–258 l/s and the 10.4 bar(e) class drops to 74–237 l/s. At Maximum the higher class starts higher and ends lower: 96–221 l/s against 74–240 l/s. Both classes keep the same 1970 kg Standard and 2220 kg FF weights, so the pressure choice does not change the frame to be delivered.

Three Builds of the ZR 90 VSD⁺ at 10.4 bar(e)

The ZR 90 VSD⁺ uses two NEOS inverters across the two stages, and its 10.4 bar(e) figures are published for Pack, iMD, and iMDG builds, each listed at Minimum, Effective at 7 bar(e), a 9 bar(e) point, and Maximum. The Pack rows carry two decimal places where the FF rows are rounded; all three builds are reproduced below as printed rather than normalised to one format.

Comparing the three ZR 90 VSD⁺ builds is mostly a question of where the dryer sits and how much the frame weighs. The iMD and iMDG rows are identical at 79–299, 79–284, 79–254, and 78–232 l/s; the Pack rows sit just below them at 78.2–298.3, 78.8–284, 78.6–253.9, and 77.6–232.2 l/s. Both FF builds quote their Minimum at 6 bar(e) against 4 bar(e) for the Pack, so the low-pressure interlock is set against a different stated point. The ZR 90 VSD⁺ keeps the 90 kW (120 hp) motor on all three builds.

The Separate 13 bar(e) Envelope of the ZR 90 VSD⁺

The ZR 90 VSD⁺ also has a 13 bar(e) table with its own three points: Minimum at 9 bar(e) / 131 psig, Effective at 10.4 bar(e) / 150 psig, Maximum at 13 bar(e) / 189 psig. It is not the 10.4 bar(e) table extended by a rule of thumb, because its Maximum lists 75.6–190 l/s against the 77.6–232.2 l/s Pack Maximum at 10.4 bar(e). The 90 kW (120 hp) motor and the 68 dB(A) work-station figure belong to this table as printed.

Water Circuits, Motor Rating, and Measured Sound

The ZR 90 VSD sends compression heat into the site’s water circuit rather than the room, so the tower or closed loop is part of the installation from the start. Two compression stages share the work, and the NEOS inverter sits inside the cubicle. The single-inverter ZR 90 VSD table states 74 dB(A) at the work station, the ZR 90 VSD⁺ is published at 66 dB(A), and the 13 bar(e) ZR 90 VSD⁺ table states 68 dB(A); all are work-station values an operator position can be checked against.

Frame data separates the platforms as clearly as the flow rows do. The ZR 90 VSD Standard frame is 1970 kg and its FF frame 2220 kg, while the ZR 90 VSD⁺ Pack is 2500 kg, the FF (iMD) 3400 kg, and the FF (iMDG) 3700 kg. Published lengths are 2030 mm for the Pack and 3430 mm for the FF build, with 1660 mm width and 2000 mm height on the Pack. A ZR 90 VSD Pack fits a shorter bay than any FF build, and the water connections need service clearance either way.

Duties That Call for the ZR 90 VSD

Water cooling is the first filter: plants with a tower, a chilled loop, or heat recovery can put the ZR 90 VSD into a compact utility room and keep the production hall free of a large cooling-air duct. Oil-free air covers the second filter, for filling, pharmaceutical packing, electronics assembly, and finishing operations where the stream reaches the product directly. The 8.6 bar(e) ZR 90 VSD class suits a header near 7 bar(e), the 10.4 bar(e) class serves a line needing headroom above 9 bar(e), and the 13 bar(e) ZR 90 VSD⁺ variant answers a high-pressure island.

Questions Buyers Ask About the ZR 90 VSD

Is the 13 bar(e) ZR 90 VSD⁺ table just the 10.4 bar(e) figures at a higher setting? No. It has its own measured points: 78.5–232.7 l/s at Minimum, 77.2–231.7 l/s at Effective, and 75.6–190 l/s at Maximum. The last figure is well below the 77.6–232.2 l/s Pack Maximum printed for the 10.4 bar(e) ZR 90 VSD⁺, so the variant trades upper flow for extra headroom.

Do the iMD and iMDG builds of the ZR 90 VSD⁺ differ in output? The published bands are identical: 79–299, 79–284, 79–254, and 78–232 l/s. The visible difference is weight, 3400 kg for the iMD frame and 3700 kg for the iMDG frame of the ZR 90 VSD⁺.

What does the ZR 90 VSD need from the building? A water circuit for compression heat, a floor that carries the chosen frame, and service clearance for the water connections. The single-inverter ZR 90 VSD states 74 dB(A) and the ZR 90 VSD⁺ states 66 dB(A) at the work station, so an operator position beside the machine can be checked against them.

From the ZR 90 VSD to the ZR 110 VSD

When a demand profile grows beyond the 96–221 l/s Maximum row of the ZR 90 VSD at 10.4 bar(e), the next frame up is the Atlas Copco ZR 110 VSD, with a 110 kW (150 hp) motor and its own 8.6 and 10.4 bar(e) tables plus a VSD⁺ branch. The step is worth taking only after the ZR 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 ZR 110 VSD keeps the same water-cooled arrangement and the same Pack or FF choice.

Before the ZR 90 VSD or the ZR 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 one of the ZR 90 VSD⁺ builds applies, then quote the configuration against those rows. That keeps the ZR 90 VSD specification tied to published figures and checks frame weight, sound level, and air treatment in advance.