Atlas Copco ZT 250 VSD (iMD VSD⁺) Oil-free Air Compressor

The Atlas Copco ZT 250 VSD is the air-cooled, two-stage oil-free screw compressor in the 250 kW (335 hp) class of the ZR/ZT 160-315 (VSD) range. The family spans the current Pack build, the FF (iMD) build with an integrated heat-of-compression dryer, and the ZT 250 VSD+ branch in Pack and FF (iMD) forms. Because the NEOS inverter synthesizes its own motor frequency, the published performance applies to 50 Hz and 60 Hz plants in one table per build. Air passes filtration and the first compression stage, crosses the intercooler with its moisture separation system, and reaches the final pressure in the second stage.

Ambient air rejects the compression heat, so the ZT line installs where a cooling water circuit does not exist or cannot be extended. Class 0 certification under ISO 8573-1 (2010) keeps oil contamination out of food, textile, medical, and electronics processes, and the variable speed drive follows the demand curve instead of cycling between load and unload.

Turn-down defines the daily value of the ZT 250 VSD. On the 8.6 bar(e) variant the flow modulates from 767 l/s at full speed down to 222 l/s at the top pressure setting, so an extrusion hall that breathes between shifts never forces the package to blow surplus air to atmosphere. Network pressure holds inside a narrow band, downstream equipment sees a steady supply, and fewer load and unload cycles ease the wear on elements, motor, and switchgear.

Especificaciones técnicas

Performance follows ISO 1217, Annex E, Edition 4 (2009), with FAD measured at the effective working pressure of each setting. The Pack table lists the two factory variants, 8.6 and 10.4 bar(e), each with its minimum, effective, and maximum pressure setting.

The Pack build measures 4438 mm long, 1760 mm wide, and 2150 mm high. The 8.6 bar(e) variant reads 75 dB(A) and the 10.4 bar(e) variant 73 dB(A) at the work station, both with the same 250 kW (335 hp) permanent magnet motor. A blow off valve and two pressure relief valves after the moisture separator protect the package across the whole envelope.

The FF (iMD) Build with Integrated Dryer

The FF (iMD) build integrates a heat-of-compression adsorption dryer in the same frame. Around sixty percent of the flow crosses the aftercooler while the hot balance regenerates the adsorption drum, and dry air leaves the outlet flange without a separate dryer vessel row. The dryer raises the minimum setting to 6 bar(e), which the FF tables reflect on both variants.

The integrated dryer stretches the frame to 4962 mm while width and height hold at 1760 and 2150 mm, and packaged weight rises to 7269 kg. Factory-completed wiring and piping between compressor and dryer remove field plumbing and the pressure drop of external connections.

The ZT 250 VSD+ Branch

The ZT 250 VSD+ build carries its own Pack enclosure at 4417 mm long, 1754 mm wide, and 2150 mm high, offered as a single 10.4 bar(e) variant with a 78 dB(A) noise level.

The ZT 250 VSD+ FF (iMD) form adds the integrated dryer to that platform: 256 to 756 l/s at the 7 bar(e) effective setting, the same 78 dB(A) level, and 7792 kg packaged on a 5348 by 1754 by 2200 mm footprint. Sites comparing the two branches weigh the wider turn-down of the VSD+ build against the current machine’s lower noise level and its two-variant pressure choice.

Inside the Package

Two next-generation compression elements with superior rotor coating divide the pressure between the stages, and the gear drive runs in filtered, temperature-controlled oil. The NEOS inverter adjusts motor speed continuously for energy savings of up to 35 percent against fixed speed operation, and the permanent magnet motor keeps class-leading efficiency across that speed span.

The Elektronikon Mk5 Touch controller handles warning indications, maintenance scheduling, and online condition visualization. A bearing life monitor works independently of compressor speed, the IP54 cubicle shields the electrical section, and the cooler block with its highly efficient water separator holds performance over the years. Energy recovery turns up to 94 percent of the electrical input into hot water for processes or space heating.

The air path inside the ZT 250 VSD is laid out for minimal pressure drop: intake air crosses the air filter and inlet valve, passes the pulsation dampener into the first stage, and flows through the intercooler with its moisture separation system and automated drains before the second stage. Zero-loss drains clear condensate without wasting compressed air, the soundproof canopy keeps the surrounding area usable, and grouped service items shorten every maintenance stop.

Where the ZT 250 VSD Fits

Plants without cooling water gain the most: the air-cooled circuit installs outdoors or in roof spaces where a water-cooled machine would need civil work. The drive absorbs batch changes and shift patterns without unload blow-off, and mixed-demand sites consolidate several fixed speed units into one machine. For the water-cooled counterpart in the same output class, the Atlas Copco ZR 250 VSD Oil-free Air Compressor carries the same envelope on a recirculated water circuit.

Engineering teams that plan capacity in stages also fit the ZT 250 VSD into a multi-machine room: the central controller groups the package with existing fixed speed units, trims the average pressure band, and lets the variable speed machine carry the trim duty while base machines run at their efficient full-load point. Options such as a silicone-free rotor, high ambient temperature versions, and witnessed performance testing tailor the package to demanding sites.

ZT 250 VSD FAQ

How does the ZT reject its heat?

Ambient air crosses the intercooler, aftercooler, and oil cooler circuits, so the machine needs no cooling tower, water treatment, or condensate handling on the cooling side.

What does the capacity envelope look like?

The 8.6 bar(e) variant spans 222 to 767 l/s (470 to 1625 cfm) across its settings, and the 10.4 bar(e) variant covers 190 to 698 l/s.

Why does the FF (iMD) table start at 6 bar(e)?

The heat-of-compression dryer needs a minimum circuit pressure to regenerate its adsorption drum, so the minimum setting rises from 4 to 6 bar(e) on the integrated build.

What separates the ZT 250 VSD+ from the current build?

The VSD+ branch comes as one 10.4 bar(e) variant with a 4417 mm Pack frame, 78 dB(A), and a turn-down that reaches 181 l/s at the bottom of its envelope.

Can the machine stand outdoors?

Yes, the coated canopy, sealed cubicle, and grouped service points suit outdoor installation, and sites should confirm the ambient version option for extreme climates.

Which industries take the ZT line?

Food and beverage, pharmaceutical, textile, chemical, and electronics plants use the Class 0 oil-free air for direct contact, instruments, and pneumatic transport.