Cast iron piston compressor WK900-7-5/270P input power 5.5 kW, intake 880 l/min, pressure 10 bar, air receiver 270 l, voltage 400/50 V/Hz
Code: WK900-7-5/270P
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Product detailed description
WALTER WK900-7,5/270P Cast-Iron Piston Compressor
The WK900-7,5/270P is a horizontal cast-iron compressor with a 3W three-cylinder unit, a power input of 5.5 kW, an intake of 880 l/min and an effective delivery of 740 l/min at 10 bar. The unit operates at 902 rpm – for a machine with a 5.5 kW input, this is the range in which compression takes place with a margin to spare, not at the limit. Power supply 400 V / 50 Hz, noise level approx. 80 dB(A), 3-year warranty after registration at waltercesko.cz.
This machine is not intended for a single operator with an impact wrench. It is designed for workshops where two people are at two points of continuous demand and a smaller compressor has begun to drop below the required working pressure. The 270 l horizontal air tank on wheels is a deliberate compromise: the machine delivers 190 l/min more than the 4.0 kW class, while remaining dimensionally manageable and movable within the workshop, rather than permanently cementing one corner.
Configuration of this machine
- Cast-iron unit — 3W · 902 rpm · single-stage compression
- Pressure vessel — 270 l · horizontal
- Horizontal design
- Three-phase 400/50 V/Hz
- Standard pressure of 10 bar for common pneumatic tools
Why choose this model
Three cylinders instead of two – why it is not just marketing
The 3W design means three cylinders arranged in a W configuration. The 880 l/min intake is divided between three compression chambers instead of two, meaning a smaller volume per stroke. The practical impact is threefold: shorter and denser pulses in the delivery instead of two large shocks, a better-balanced crankshaft mechanism, and more uniform tension on the V-belts. This platform shares the 3W three-cylinder unit with the 3.0 kW class – but here it runs slower and with a larger transferred volume.
740 l/min is the threshold between one and two workstations
Compared to the 550 l/min of the 4.0 kW class, this is 190 l/min more. It sounds like a one-third increase, but in practice, it is a turning point: 550 l/min can handle one continuous draw and peaks of a second, whereas 740 l/min covers two truly continuous draws – for example, an orbital sander (300 to 450 l/min) and a chipping hammer simultaneously, with a reserve for leaks in the air network.
902 rpm – approximately 25% less than the 3.0 kW class
A unit of the same design in the 3.0 kW class rotates at 1,202 rpm; this one rotates at 902 rpm. Given a comparable piston stroke, this means approximately a quarter shorter sliding path of the piston ring per hour of operation. This figure is not compared in catalogues because it does not look like performance – but it is precisely the metric that determines how many thousand hours the unit lasts before needing rings.
270 l reserve and a machine you can still move
With a typical pressure differential between cut-in and cut-out of 2 bar, a 270 l tank delivers approximately 540 l of free air per cycle. At a continuous draw of 300 l/min, this results in roughly 20 motor starts per hour. The version with a 500 l tank has about 11 starts under the same conditions, but it is a machine that is positioned and stays put. This variant remains a horizontal tank on wheels – you move it to the work, not just to a corner.
Who is it for
The typical buyer is a metalworking shop or a smaller metal fabrication plant with two permanent workstations – one person grinding, another using a chipping hammer or impact wrench – and a car repair shop with three bays, where the simultaneous use of tools cannot be scheduled. It is also suitable for a joinery with sanders and pneumatic clamping, where it is not just about the volume of air, but ensuring that the pressure in the distribution system does not fluctuate and tools do not slow down. If the machine only runs for a few hours a week and never more than one tool at a time, this class is unnecessarily large.
Typical applications
- Two simultaneous continuous draws: an orbital sander and a chipping hammer in a body shop
- Pneumatic angle grinder (400 to 600 l/min) in continuous operation, with reserve for a second tool
- 1/2" impact wrench across several car repair shop bays without waiting for repressurisation
- Pneumatic clamping, drills, and ratchets in metal fabrication with short but frequent draws
- HVLP spray gun simultaneously with air blow-off – pressure in the distribution system remains stable
- Sandblasting with a 3 mm nozzle in shorter bursts; for continuous sandblasting, choose the 7.5 kW class
Where to choose a different model
The machine is to remain in one place and feed a fixed distribution system across the entire workshop
Opt for the same unit on a 500 l tank. The free air reserve per cycle increases from 540 to 1,000 litres, the number of motor starts at a draw of 300 l/min drops from approximately 20 to 11 per hour, and the distribution system can handle short draws exceeding 740 l/min.
You need to sandblast continuously or serve three draws simultaneously
740 l/min is not enough for this – a sandblasting gun with a 3 mm nozzle consumes 500 to 1,000 l/min on its own. Go for the four-cylinder 7.5 kW class with a delivery rate of 1,100 l/min and a 500 l air tank.
In fact, you never have two tools running continuously at the same time
Do not overpay for power. The 4.0 kW class with the same 270 l tank delivers 550 l/min, runs at 993 rpm, and is a correctly dimensioned machine for one continuous draw plus the peaks of a second one.
What the figures tell you — calculated values
The values are calculated and are meant for comparing the models with each other, not as guaranteed figures.
Design and technology
Related models and alternatives
WK900-7,5/500P
The same 5.5 kW three-cylinder unit on a 500 l tank: double the reserve, roughly half the number of motor starts.
VWK900-7,5/270P
Vertical version of the same unit with a 270 l air tank – same air reserve on approximately half the footprint.
WK1500-10/500P
One class higher: four-cylinder 7.5 kW, 1,100 l/min and 768 rpm – for continuous sandblasting and three draws.
WK900P-PLATE
The unit alone on a base frame without a pressure vessel – for replacing a worn-out unit on your own tank.
Frequently asked questions
- Why does this machine with a 5.5 kW power input have three cylinders, while the smaller 4.0 kW model has only two?
- The number of cylinders is not a measure of power – the combination of bore, stroke and RPM is what matters. The 4.0 kW platform handles its 630 l/min intake with two cylinders with a larger bore at 993 rpm; this 5.5 kW platform distributes 880 l/min into three smaller cylinders in a W-configuration at 902 rpm. Three cylinders provide a smoother compression cycle and a better-balanced crankshaft mechanism, rather than higher power on its own.
- Is a 270 l tank sufficient for a delivery rate of 740 l/min?
- For a continuous draw of approximately up to 400 l/min, yes – at 300 l/min the motor switches on about 20 times per hour, which is normal for this design. Where 270 l is insufficient is during peak demands exceeding 740 l/min: the tank can cover this for only about 2 minutes before the pressure drops. If you expect such peaks regularly, opt for the version with a 500 l tank.
- Can it run two pneumatic angle grinders simultaneously?
- No. A pneumatic angle grinder consumes 400 to 600 l/min continuously, so two would require 800 to 1,200 l/min – which exceeds the 740 l/min provided by the machine. However, it can handle a grinder and an impact wrench, a grinder and a blow gun, or a grinder and a stapler. For two grinders in continuous simultaneous operation, you will need the four-cylinder 7.5 kW class.
- What electrical connection does the machine require?
- It is a three-phase machine 400 V / 50 Hz with a power input of 5.5 kW. The supply and fusing are dimensioned according to the power input and cable length – precise values can be found in the machine manual; leave the installation to a qualified electrician. Starting is facilitated by an unloader valve, which relieves the cylinder head upon stopping, ensuring the motor starts without back pressure in the delivery line and the circuit breaker is not stressed by the full starting current during each of the dozens of daily cycles.
- Is it louder than the smaller models in the range?
- The entire range has the same figure of approximately 80 dB(A). The practical difference is more in the character of the sound than in the number: 902 rpm and three cylinders produce a lower and smoother tone than high-speed units. The machine has an open design without a noise enclosure – the advantage is full service access to the unit and connections; the disadvantage is that the noise is not dampened. If it is located next to a workstation, allow for hearing protection or place it in an adjacent room.
The machine comes with a 3-year warranty after registration with the importer. Warranty terms, the maintenance schedule and a comparison of all 28 models are in the category WALTER cast-iron piston compressors.
Ventilek’s tip
Two people on the tools all day — that's where a real workshop begins. For that kind of work, this is the smallest sensible machine.
Additional parameters
| Category: | Air compressors |
|---|---|
| Warranty: | 3 years |
| EAN: | 5905122000141 |
| Compressor type: | Piston compressor |
| Pressure: | 10 bars |
| Suction power: | 880 l/min |
| Air delivery: | 740 l/min |
| Pressure vessel volume: | 270 L |
| Design of pressure vessel: | Lying down |
| Connecting: | Quick coupling DN 7.2, Ball valve 1/2" |
| Motor power: | 5.5 kW |
| Mains voltage: | 400/50 V/Hz |
| Speeds: | 902 rpm |
| Number of cylinders: | 3 |
| Number of grades: | 1 – single-stage compressor |
| Lubrication: | Oleic |
| Noise: | 80dB(A) |
| Dimensions: | 1650 × 510 × 1150 mm |
| Weight: | 178 kg |
| Accessories: | Pressure regulator, Wheels, Handle, Quick coupler, Ball cock |
| Engine: | Electric |
| Soundproofed: | No |
| Drive: | V-belts |
| Air dryer: | No |
| Retrieved from: | Professional |
| Development: | Mobile |
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