150HP Double Stage VSD Screw Air Compressor

The 150HP two stage screw compressor with VSD is ordered for the pressure band more than for the horsepower. Two stages split the compression so neither carries the full ratio, and the drive keeps the pair turning at the speed the plant is using instead of cycling between loaded and unloaded. Model SAD-110: 110 kW (150 HP), 0.8 to 1.3 MPa (8 to 13 bar), 24.5 to 18 m³/min (865 to 636 CFM), direct drive and air cooled.

Splitting the compression into two stages changes the numbers each stage works with. The first stage raises the air to an intermediate pressure, the intercooler takes the heat of that stage out of the air before the second stage sees it, and the second stage finishes the job from a cooler, denser starting point. Each stage then carries a lower pressure ratio than a single stage machine would need for the same discharge pressure, and a lower ratio means less internal leakage past the rotors and less heat in the oil. That is what separates a double stage air compressor from a single stage machine of the same power on a duty that runs long hours: the air leaves cooler, and the element keeps more of what it took in.

The drive is the second half of the arrangement. A fixed speed machine turns at one speed and unloads when the receiver is full; in the unload state the element still turns and the motor still draws, so the hours a plant spends below full demand are paid for whether the air is used or not. A vsd screw compressor runs at the speed the demand asks for, so those hours are spent at part speed and part power. On a duty that sits at 60 or 70 percent of capacity for a ten hour shift, that band is where most of the difference is found.

The motor is a permanent magnet synchronous type, run by the drive. There is no field winding to excite, so there is no excitation current to lose, and the rotor does not fall away in efficiency as its speed drops the way an induction motor does off its design point. Paired with a two stage airend, whose advantage sits in the rotors rather than in the control, the two effects work on different parts of the same problem. Against a single stage variable speed machine of the same power, the SAD series is rated at 10 to 15 percent less energy for the same air.

The set point is chosen inside the 8 to 13 bar band when the order is placed, and the flow figures follow it: 24.5 m³/min (865 CFM) at 8 bar, falling to 18 m³/min (636 CFM) at 13 bar. A plant that works at 8 bar gets the full output, and a plant that needs 13 bar for a process step gets a machine built for that band rather than a standard 8 bar unit pushed past its design point. Buyers comparing this machine against an 800 cfm air compressor listed elsewhere should check the pressure the figure is quoted at. The number that matters is the one at your working pressure, and we will confirm both before the order is placed.

Two stage compression earns its cost on long shifts near full output. That is why it turns up in plants that never shut the compressor down: textiles, cement, glass, bottling, general works. Where demand swings wide and sits low for most of the day, the second stage does not pay for itself. On that duty a single stage permanent magnet machine at the same power is the cheaper way in. Consumables are the standard set for a screw machine: air filter, oil, oil filter and separator, all from the same service parts range.

Advantages

Why Choose Us

• The airend is a HANBELL two stage unit. It is the most expensive part of the machine and the one with the longest lead time, so it is worth knowing what it is rather than taking an unbranded assembly on trust.

• The machine is built for the top of the pressure band. A two stage element shows its advantage where a single stage machine runs hottest and loses most, which is 13 bar rather than 8, and this model covers the whole 8 to 13 bar range from one frame.

• The pressure band is wide enough that the order starts with a choice rather than a default. 8 bar gives the full 24.5 m³/min, 13 bar gives 18, and the point between them is set on your instruction before the machine ships.

• The flow at both ends of the pressure range is published: 865 CFM at 8 bar, 636 CFM at 13 bar. You can check the machine against your own duty before you order rather than after it lands.

• The receiver and the main line carry as much of the load as the compressor does at this size, and they can be worked out against your peaks as part of the same order.