Some air compressors come in two types: single and two-stage. When it comes to buying a single-stage or dual-stage air compressor, the first question that prospective buyers often ask is, “What are the differences between the two?”
Single-Stage vs. Two-Stage Air Compressor
The main difference between single- and two-stage compressors is the number of times that air gets compressed between the inlet valve and the tool nozzle. In a single-stage compressor, the air is compressed one time; in a two-stage compressor, the air is compressed twice for double the pressure.
Single-stage compressors are also known as piston compressors. The process that takes place within a single-stage compressor goes as follows:
- Air is sucked into a cylinder
- The trapped air is compressed in a single stroke with a piston at roughly 120 psi
- The compressed air is moved onward to a storage tank
In the storage tank, the compressed air serves as energy for the assortment of tools that a single-stage compressor is built to accommodate.
The process within a two-stage compressor — alternately referred to as a dual-stage compressor — is similar to that of a single-stage, but with one variation: the compressed air isn’t sent to a storage tank; it’s instead sent to a smaller piston for a second stroke, this time at roughly 175 psi. From there, the double-pressurized air is cooled and delivered to a storage tank, where it serves as energy for vast arsenals of high-powered equipment.
How Many Compressor Stages Do I Have?
People who are new to air compressors will often confuse the number of cylinders for the number of stages in an air compressor, when in fact, both single- and two-stage compressors use two cylinders because it’s easier to balance air that way.
You can tell how many stages your air compressor has based on the size of the cylinders and the number of air intakes. On a single-stage compressor, all cylinders will be the same size and have their own inlet valves. On the other hand, in two-stage compressors, there is only one inlet, and the second piston is shorter than the first, and the two are linked by a cooling tube, which brings the temperature of the air down before the second round of compression.
Single-stage air compressors are often small units that can easily be transported from one room to another. By contrast, multi-stage compressors are typically larger and somewhat heavier.
Uses of Single-Stage vs. Dual-Stage Air Compressors
Dual-stage air compressors produce higher air power, which makes them a better option for large-scale operations and continuous applications. However, two-stage compressors also cost more, which makes them better suited for factories and workshops than private use. For the independent craftsperson, a single-stage compressor will power a variety of handheld pneumatic tools that don’t exceed 100 psi. At auto shops, pressing plants and other settings in which complex arsenals of air-powered machinery are utilized, the higher capacity dual-stage units are the more preferable option.
Out of all the activities that a person could do in their garage or backyard, few are as tool-intensive as woodworking. From cutting and sawing to sanding, drilling and nailing, there’s a vital tool being used along every step of the way, regardless of whether you’re making furniture, canoes or living room fixtures. Some of the tools used in these steps can be quite intensive in that they require a lot of physical exertion. As such, woodworking involves a certain degree of physical stamina, as well as hand-eye coordination.
However, for all the tools that require such exertion, there’s a pneumatic equivalent that will bear the brunt of the task in question. Imagine being able to cut each board and drill each hole evenly and easily in a matter of seconds; it’s all possible with air-powered saws and drills. All you have to do is hold the tool in place and the airpower does the rest — no strained wrists, no overworked shoulders or elbows. Best of all, each application is accomplished so fast that there’s little time to slip or ruin a project.
With a single-stage air compressor, you could power a vast array of woodworking tools that would make it possible to achieve in minutes what would otherwise take hours with old-fashioned hand tools. The kinds of tasks that you could accomplish with a single-stage compressor include the following:
Sawing: Once a woodworking project has been conceived, the first major step involves trimming the boards and cutting out the shapes and panels for use. Historically, woodcutting was a dangerous task, best left to the strong and skilled. But now it’s far easier with a pneumatic speed saw, which can slice through the wood in just a fraction of the time it would take to manually run carbide blades from one board side to another. Air-powered speed saws can be fitted with blades of various lengths for different board thicknesses.
Nailing: Hammering things together can be one of the most awkward and risky parts of any woodworking project. Awkward because a slip of the hand could bend the nail or send it in crooked. Risky because you could also miss the target and hammer your thumb, the board or even the underlying surface. Worst of all, nails often fail to go in all the way, either due to a hard, impenetrable depth or because the nail wasn’t straight in the first place. The solution to these problems is an air-powered nailer, which sends nails in straight and even while penetrating thicknesses without a fuss. Best of all, it will do all of this in seconds, up and down along a given board.
Drilling: Due to the fact that hole formation relies heavily on hand-eye coordination, the act of operating a drill can be just as awkward as hammering a nail. Any wrist or elbow slip could send a drill in crooked or cause the hole to spread too wide for the allotted nuts and bolts. A drill is also a very powerful device, which can be problematic when you fire off-target and send a line of holes off balance. Such risks are greatly reduced with the use of an air-powered drill, which can drill holes through 2x4s faster, and with greater accuracy.
Sanding: After the project is assembled, the raw edges and rough surfaces need to be smoothed out and polished. Sanding makes the difference between raw wood and panel material, but it usually takes machinery to achieve such a transformation. Sure, sandpaper has been around for ages, but the grains of sand usually leave marks or streaks in whichever direction the hand swings. This isn’t appropriate for any piece of wood that a person might use for a chair, cabinet or picture frame. These are the reasons why woodworking requires an orbital pneumatic sander, which moves around in multiple directions for a smooth, streakless finish on all types of wood surfaces.
If woodworking is a trade that’s greatly facilitated by the use of air compressors, work involving metal is virtually impossible without them. As the world’s strongest material, metal is a lot harder to cut, drill, mold and join together. While it’s still possible, though not exactly preferable, to power woodworking tools with your own physical strength, the same cannot be said for metalwork. Simply put, metal crafts require electric or air-powered tools that go above and beyond mere human capabilities.
The following tasks can be performed on metal within seconds with a single-stage compressor and the appropriate pneumatic tools.
Shearing: As conventional wisdom holds, metal alloys must be molded a certain way in order for the finished product to come in a particular shape. What most people don’t know is the power of pneumatic metal-cutting tools. With an air-powered shear, metal workers can cut through sheets of metal in a similar manner to cutting cardboard with a rotary cutter.
Grinding: Everyone knows what to do when trimming is needed on wooden sheets and boards, but what about when the same thing is needed along metal tubes, pipes and bars? For the material that’s supposedly impervious, pneumatic grinders work wonders. Whether you need to cut a long brass bar in half or trim an inch off the edge of an aluminum pipe, it can all be done in under a minute with an air-powered grinder. When attached to a single-stage air compressor, a grinding tool can be especially useful when that small but critical metal piece is just a few millimeters too wide to fit with a corresponding space.
Riveting: Welding is not the only way to join metal pieces together. In the fabrication of metal drawers or cabinets, plates of metal are joined in a similar manner to panels of wood in oak or mahogany furniture, only the fasteners are different. When metal sheets are combined to build sheds and other structures, rivets are typically the fastener of choice. Using a pneumatic riveter, you can join two metal panels tight along the seams in seconds. The pneumatic riveter sends pin-like fasteners through pre-made metal holes for a tight, secure fit.
Ratcheting: There are certain metal fasteners that need to come undone; trouble is, time acts as a natural welder. When a nut has been screwed as tight as can be, with the purpose of never being unscrewed, you could have your work cut out for you with a regular wrench. For problems like these, there’s the air-powered ratchet, which will break long-stuck nuts loose from bolts and allow you to disassemble items, regardless of how far back a given item might date. Within seconds, a ratchet can separate what would otherwise end up joined for all time in a landfill.
All of these wood and metal applications can be performed independently with tools that operate at 90 psi or under with a single-stage compressor.
With so many heavy-duty applications performed in the process of vehicle construction, pneumatic tools and machines save untold sums of energy at assembly plants. Unlike personal crafts and small-scale operations, however, assembly plants need more than merely 100 psi to perform the vehicle construction and maintenance.
At plants and repair shops alike, two-stage compressors make it possible to pneumatically drive the following applications:
Lifting: The assembly of vehicles requires tons of parts lifting, from the frame and shell to the engine and passenger compartment. At the early stage of vehicle construction, there are parts that need to be mounted onto a conveyor belt for piece-by-piece assembly. After the car is mostly assembled, it needs to be lifted overhead so that finishing touches can be applied. A two or three-stage air compressor can be used to powerlifting devices with suctions strong enough for heavy loads.
Screwing: From engine parts to hubcaps, there are a lot of parts to be screwed and bolted together production. With air-powered impact wrenches and ratchets, work crews can quickly assemble and disassemble vehicle parts, so that each car can be moved along the conveyor with utmost efficiency.
Greasing: An engine consists of several key parts that are continually in motion during vehicle operation. Most of these moving parts are made of metals that would grind together and wear out from friction if it wasn’t for lubrication. As with most machines — air compressors included — grease is vital to the life of each vehicle. At assembly plants, pneumatic-powered greasers apply lubricants on a variety of car parts, some of which are difficult to reach or too hot to handle.
Painting: In the eyes of the casual observer, paint makes the vehicle. What isn’t commonly understood is the complex process of painting vehicle shells. The shells must be primed and coated in a clean environment, free of moisture or oil in both the pneumatic and atmospheric air. Two-stage compressors can be used to power paint sprayers, which provide streak-free, blotch-free coats for an overall smoothness that could never be achieved with spray cans or rollers.
Two and three-stage compressors are also ideal for powering pneumatic tools and machinery along the production lines at furniture factories and food-packing plants.
The two-stage reciprocating air compressor is vital at any factory that bottles beverages for mass distribution. With compressed air, soda pop and fruit drink companies can turn out thousands of units per day with the following pneumatic processes:
Molding: Packaged foods and drinks generally come in containers formed with air-powered equipment. In the beverage industry, air compressors first mold bottles out of glass. Along the conveyor systems at glass plants, pneumatic machines pour liquid glass into cavity molds. Air-powered dryers then solidify the molded glass. A similar process is used to prepare tin cans in factories that package foods.
Filling: After the bottles are ready, they’re distributed by shape and color to various beverage manufacturers, including makers of wine, soft drinks and fruit juices. In the bottling factory, each bottle is sent along a conveyor system where air-powered machines fill each bottle with a preprogrammed amount of the beverage.
Sealing: Once the bottles are full, they must be sealed with air-tight, foolproof caps or lids. One air-powered machine extracts all air from the empty portion of the bottle, and another puts the lid onto place. For example, soda pop and beer bottles get a metal cap around the circumference of the bottle top.
Labeling: Finally, each bottle must receive a label. Sometimes this involves heat-branding the logo onto the glass. In most cases, pneumatic robotic arms apply a sticker to the bottle.
Packaging: After the bottles are filled, sealed and labeled, they are ready to be packaged and shipped. Some drinks are grouped together in packs of four or six, while others are sold separately. At beverage plants, air-powered robotic arms safely and neatly package each bottle into a box for easy delivery.
A similar process happens in factories the package foods in cans and jars. Dual-stage compressors are ideal for the processes employed along the conveyor systems at food and beverage processing plants.
Food Preparation and Packaging
Food assembly and packaging could either need a single- or multi-stage compressor. It depends on the scope and magnitude of the processes. If you are producing foods inside a bakery or the in-house kitchen of a supermarket, you can probably accomplish everything with a one-stage air compressor. For mass preparation and packaging in a factory, you would need a two-stage. Either way, compressed air is typically used to drive the following processes in the food industry:
Mixing: Compressed-air tools are often used to blend the ingredients of various baked goods, such as breads, pastries, cakes and cookies. Once the ingredients are perfectly measured and added for each batch, the mixture is readied in a large bowl with pneumatic blending equipment. This way, bakers can produce these goods in much larger quantities than would otherwise be possible if the mixing relied on human hands.
Powdering: For mass-produced powdered doughnuts and cookies, air-powered equipment usually does the powdering. The impact and radius of applied air are enough to cover the entire surface of each edible item in one application and also light enough to prevent damage. Doughnuts, for instance, will be rotated through pipes where powdered sugar is sprayed onto both sides, ensuring that each doughnut is equally coated by the time they’re packaged.
Frosting: For cakes and other frosted treats, air-powered tools apply the icing. Air-powered tools also inject fillings such as cream or jelly into pastries.
Chopping: Pneumatic tools typically cut chopped or sliced foods. Potato chips, for example, are cut uniformly from raw potatoes. In factories, machine-peeled potatoes pass through conveyors where they are sliced with precision, sometimes with specially designed cutting tools that give certain potato chips their ridges. After being fried, the slices are dried with compressed air and flavor-coated with pneumatic equipment.
Cooling: Air-powered tools cool baked or fried foods to bring them back to room temperature. This reduces the cooling time so foods can be packaged more quickly. Without the aid of air-powered cooling, some of these heated foods could take up to an hour to cool down to a temperature suitable for packaging.
Cleaning: Pneumatic blowing tools clean food and beverage containers before packaging. Containers on a conveyor system receive a blast of air to remove dirt, moisture or air-bound impurities that may have stuck to the interior surfaces.
Nitrogen: For certain packaged foods, pneumatic nitrogen blowers pump nitrogen into the package before sealing to prevent the contents from being crushed.
In a bakery, single-stage air compressors are ideal for the air-powered process that food preparation would normally require. A single-stage compressor can be moved to different locations, if necessary, to meet the demands of a given day’s tasks. For mass-produced foods, factories need a dual-stage compressor to meet the higher demands of industrial machinery.
For aircraft, tanks and other large pieces of equipment, air-powered machines are used in all stages of assembly. As with any factory production, you need a dual-stage compressor to generate the air power needed for the machinery at hand. So how does a two-stage compressor work in aircraft and artillery construction? It does so in the following ways:
Cutting: The parts that comprise an airplane, jet or rocket must first be molded from raw metals and cut into finished shapes. These steps are conducted along large conveyor systems. First, the raw metals are cut into shapes with specific dimensions. Then, the parts are formed inside molding cavities. These parts are then sent along for polishing and further preparation. A similar set of steps is employed for land vehicles and artillery. Such steps generally require high-powered dual-stage air compressors.
Shaping: The raw parts that comprise a vehicle or aircraft are measured and inspected before being sent along the assembly path. If a part has any raw edges that don’t quite fit the exact measurement of a given design, it must be cut into shape with pneumatic sawing tools. The part must then be re-inspected to ensure that it is ready to be connected to the corresponding parts of the structure in question. The parts that pass through these stages on a conveyor system include wings, rudders, flaps, ailerons, propellers and the pieces of an engine.
Assembling: Once all the parts of an airplane or artillery vehicle pass inspection, they move to the conveyor belts where assembly takes place. Human workers work with robotic arms and operate pneumatic tools to fasten each part to another in methodical order. At each stop along the conveyor system, a passing part is affixed with further parts until it becomes the completed component of a larger structure.
Fastening: One of the most crucial tasks along airplane conveyor systems is the fastening of parts, as this step ensures the stability and safety of the aircraft. Each part must be bolted or riveted into place for maximum strength at high altitudes. Humans operate pneumatic tools or oversee computer-operated robotic arms during this stage.
Finishing: Once the components of an aircraft or military vehicle are assembled, some of the final steps involve the outer finish. For an aircraft, this involves paint and decals that give each plane its distinctive look and brand identity. For tanks and other equipment, this involves the paint job that makes it blend in with the colors of the armed services. A mix of air-powered sanders, blowers, painters and dryers handle these finishing touches.
With a dual pump air compressor, manufacturers of aircraft, helicopters, rockets and military vehicles can produce new and more powerful models with speed and precision for maximum efficiency. When there’s an urgent need for new artillery, air compressors make it possible to build new equipment in record time. Without compressed air, manufacturers could not meet such fast production demands.
Is Single-Stage More Reliable Than Two-Stage?
One major difference between single-stage and two-stage pump compressors is that the former are made for intermittent use, whereas the latter are suited for ongoing applications. Therefore, the reliability factor will all depend on what you plan to do with your air compressor.
If you need compressed air to power work tools in your garage or cooking equipment in a kitchen, a single-stage compressor should handle all your needs. If you need an air compressor for factory applications, a single-stage unit would not be a reliable piece of machinery. The parts in a single-stage are larger and more prone to condensation. Moreover, single-stage compressors are not built for non-stop use throughout a given work cycle. Multi-stage compressors have the cfm needed to handle large arsenals of pneumatic tools. They’re also more suited for high-powered applications like sanding and painting.
Is Single-Stage or Two-Stage More Expensive?
Two-stage air compressors are more expensive than their single-stage counterparts because there are more parts involved. However, the parts in a two-stage unit are smaller and typically require maintenance at less frequent intervals. Therefore, the costs to operate a two-stage compressor could be less expensive in the long run. A two-stage compressor can also make your operations less expensive if your applications are factory scale. If you have many pneumatic tools, you need a compressor with optimal cfm for every application that you intend to run simultaneously. In an automotive plant, a single-stage compressor wouldn’t likely suffice. You would probably need a second single-stage compressor to handle some of the applications, thus raising your operating costs. For factory use, your upfront investment in a multi-stage compressor could save you money over time.
What Is Better: Single-Stage or Two-Stage Air Compressor?
Single-stage compressors have one cylinder. Therefore, there is only one piston stroke for each revolution of pressurized air. The relative quietness of these units makes them ideal for smaller working environments like kitchens, garages, workshops and homes. When it comes to the capacity of an air compressor, the most important spec is the cfm, which indicates the operating capacity. If, for example, you have multiple pneumatic tools that you plan to run simultaneously, you will need to make sure that the compressor you chose will exceed the cfm demands. As for horsepower, consider that 1 hp moves 550 pounds 1 foot per minute, then imagine what 2 hp or 3 hp will do. Ultimately, your choice between a one-stage or multi-stage compressor should be based on the size and nature of your operations. In summary, one stage units are for small-scale projects and personal use, while two-stage models are more geared toward industrial-scale arsenals.
Learn More About Single- and Two-Stage Air Compressors
Regardless of the size or scope of a given operation, air-powered tools are essential to the productivity of craftspeople and work crews alike. If you are an independent woodworker or the owner of crafts line, a single-stage compressor could help you make products faster, better and more efficiently. If you manage a work crew at a large pressing plant, two-stage compressors could be used to power the most heavy-duty aspects of your operation.
When it comes to air compressors, Quincy Compressor has long been established as one of the most trusted names in the business. To learn more about our small portable and large stationary units, visit our sales and service page to locate the nearest Quincy service representative.