Atlas Copco ZR 55 VSD Oil-free Tooth Air Compressor

The Atlas Copco ZR 55 VSD is the water-cooled 55 kW (75 hp) flagship of the ZR 37-55 VSD branch, and its data sheet deliberately carries one pressure class: 8.6 bar(e). The air-cooled ZT 55 VSD splits the same motor across 8.6 and 10 bar(e) tables, but the ZR 55 VSD concentrates on a single class of three measured points, an ID / IMD integrated dryer option, and a 70 dB(A) sound pressure level at the work station. The frame measures 2440 × 1016 × 1880 mm across the whole 15-55 VSD platform, so a plant planning around the ZR 55 VSD can lay out the bay on the same width and height the smaller ZT and ZR units occupy.

Water cooling also moves the compression heat out of the room, which is the branch to check first for halls where heat rejection through fans is not welcome.

One Class, Three Points on the ZR 55 VSD

Every published row of the ZR 55 VSD belongs to the 8.6 bar(e) class: Minimum at 4 bar(e), Effective at 7 bar(e), and Maximum at the rated 8.6 bar(e). The drive keeps the flow band almost flat across that whole pressure travel, from 42.5–138.3 l/s at Minimum to 41.0–134.6 l/s at Maximum.

The numbers deserve a close read: between Minimum and Maximum the upper flow edge of the ZR 55 VSD steps down only 3.7 l/s, and the m³/min column moves from 2.5–8.3 to 2.5–8.1, so the flow a buyer counts on at 4 bar(e) is nearly the flow delivered at rated pressure. That flat profile comes from the way the tooth element and the drive are matched on this 55 kW machine, and it means a plant sized on the Effective row at 137.1 l/s will not discover a shortfall when the header rises toward 8.6 bar(e).

Water Cooling and the 70 dB(A) Work Station Level

The ZR 55 VSD rejects its heat through the cooling-water circuit rather than through a fan wall, and the data sheet lists 70 dB(A) at the work station for the whole class. The air-cooled ZT 55 VSD on the same platform prints 78.5 dB(A), so the two cooled variants of the 55 kW point sit 8.5 dB(A) apart in the same table. The figure follows the A-weighted sound pressure level at the work station (LpWSAd), scanned with sound intensity under ISO 2151:2004 and ISO 9614/2 and published with the KpAd uncertainty correction.

For a plant whose compressor room shares a wall with offices, laboratories, or packing lines, the printed spread between the two cooled builds is one of the first numbers to compare.

Weight, Dimensions and the Dryer Choice on the ZR 55 VSD

The standard model weight of the ZR 55 VSD is 1410 kg against 1481 kg for the air-cooled ZT 55 VSD, both printed as standard model weights in the same data sheet. The 2440 × 1016 × 1880 mm frame matches the ZT 30-55 VSD group, and the dryer column lists ID / IMD for the 8.6 bar(e) class — the integrated refrigerant dryer or the integrated MD dryer inside the same canopy. The note on integrated dryers warns that they will increase the weight, so the delivered build should be weighed against the floor plan before installation.

Matching the ZR 55 VSD to the Plant It Serves

The water-cooled VSD branch of the 15-55 line has two rungs, and the table below shows both of them at 70 dB(A): the ZR37VSD-8.6 at 37 kW and 1372 kg, and the ZR 55 VSD one motor size above it. A header regulated near 10 bar(e) is the case where this branch stops — the 10 bar(e) class is printed for the air-cooled ZT 55 VSD, not for the water-cooled ZR 55 VSD — so the cooling-water decision and the pressure decision should be made together.

Plants that already run a cooling loop gain the quieter 70 dB(A) level and the 1410 kg standard frame; plants without water infrastructure compare the ZT 55 VSD instead, accepting the higher sound level for the wider class choice.

Questions Buyers Ask About the ZR 55 VSD

Why does the ZR 55 VSD come in a single pressure class? The water-cooled VSD branch of the 15-55 platform is published at 8.6 bar(e) only, with three measured points and 70 dB(A) throughout. Where a project needs the 10 bar(e) class at 55 kW, the same data sheet carries it on the air-cooled ZT55VSD-10 with a flow band of 32.3–122.0 l/s at Maximum, so the pressure requirement decides the cooled build, not the other way round.

How heavy is the machine that arrives on site? The standard model weight of the ZR 55 VSD is 1410 kg in a 2440 × 1016 × 1880 mm frame. The ID / IMD dryer options are listed inside that frame, and the data sheet explicitly notes that an integrated dryer increases the weight, so the final delivery mass depends on the treatment build ordered with the compressor.

What does the 70 dB(A) figure actually describe? It is the A-weighted emission sound pressure level at the work station (LpWSAd) at rated operation, measured according to ISO 2151:2004 with the ISO 9614/2 sound intensity scanning method and printed with the KpAd uncertainty correction. It is not a sound power rating, and it applies to the whole 8.6 bar(e) class of the ZR 55 VSD from Minimum to Maximum.

From the ZR 55 VSD to the ZR 75 VSD

Above the 138.3 l/s top edge of the ZR 55 VSD, the water-cooled oil-free line continues with the Atlas Copco ZR 75 VSD, whose 8.6 bar(e) class reaches 229.4 l/s at the upper end of its Effective row on a 75 kW motor. Quoting the measured pressure and the demand curve of the header with the enquiry is the shortest route to the right machine and build.