{"product_id":"castair-3hp-rotary-screw-base-mount-compressor-r31bm50","title":"Castair 3HP Rotary Screw Base Mount Compressor - R31BM50","description":"\u003ch2\u003eCastair 3HP Rotary Screw Base Mount Compressor — R31BM50\u003c\/h2\u003e\n\n\u003cp\u003eThe Castair R31BM50 is a 3-horsepower rotary screw compressor sold as a base mount unit — no tank included. This configuration is designed for shops that already have a receiver tank in place, want to upgrade an existing system's pump and motor, or need to mount the compressor remotely from the air storage. The rotary screw design means 100% duty cycle: this unit can run continuously without the piston heat buildup and valve wear that limits reciprocating compressors in high-demand applications.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNote: Manufacturer specifications for the R31BM50 were not available on Castair's website at time of writing. The specifications below are based on available model number data and Castair's standard rotary screw line. Contact us at 866-217-0063 for confirmed specs before ordering.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003ch3\u003eWhy Rotary Screw vs. Piston for a 3HP Application?\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e100% duty cycle:\u003c\/strong\u003e A rotary screw at this horsepower can run continuously. A piston compressor at 3HP is typically rated for 50-75% duty cycle — in a busy shop, that matters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eQuieter operation:\u003c\/strong\u003e Rotary screw compressors run at lower RPM than piston units of the same output, producing significantly less noise on the shop floor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLower maintenance interval:\u003c\/strong\u003e No valves, pistons, or rings to wear out. Scheduled maintenance is oil, oil filter, air filter, and separator filter changes at manufacturer-specified intervals.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConsistent pressure:\u003c\/strong\u003e Rotary screw compressors maintain steady output pressure without the pressure cycling of a piston\/tank setup running to cut-out and recovering.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eBase Mount Configuration — What This Means for Your Install\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo tank included:\u003c\/strong\u003e The R31BM50 ships as the compressor assembly only — air end, motor, belt drive, controls, and base frame. You supply the receiver tank.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlexible installation:\u003c\/strong\u003e Mount to an existing horizontal or vertical receiver, a wall-mounted tank, or a remote tank plumbed to your drop lines.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSmaller footprint:\u003c\/strong\u003e Ideal when floor space is at a premium and a tank is already in service.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSystem upgrade path:\u003c\/strong\u003e If you have an older piston compressor with a good tank, the base mount configuration lets you drop in a rotary screw head without replacing the entire system.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCastair Rotary Screw Build Quality\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAll cast iron construction:\u003c\/strong\u003e Castair builds with cast iron throughout — not aluminum heads or pot metal fittings. Cast iron handles thermal cycling and wear better in shop environments.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIndustrial 1725 RPM motor:\u003c\/strong\u003e Heavy-duty motor with full 15% service factor. Lower RPM means longer bearing life compared to high-speed motors.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSimple single-solenoid control:\u003c\/strong\u003e One solenoid operates the air end. No computers, no lockout codes, no proprietary diagnostic tools required. Any electrician or competent shop tech can troubleshoot and repair it.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePressure and temperature gauges standard:\u003c\/strong\u003e Easy-to-read analog gauges — no digging through menus on a control panel to check operating status.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh pressure and dual high temperature shutdown:\u003c\/strong\u003e Built-in protection shuts down the unit before damage occurs. Protects the air end from overheating and the system from overpressure.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFactory filled with synthetic lubricant:\u003c\/strong\u003e Ships with Cast-Lube synthetic oil good for 4,000 hours or one year. No break-in oil swap required.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOff-shelf V-belts with adjustable belt tensioner:\u003c\/strong\u003e Standard V-belts available at any industrial supply. No proprietary belt sizes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBuilt-in air\/oil separator with spin-on filter:\u003c\/strong\u003e Keeps oil carryover out of your air lines. Spin-on design makes replacement straightforward.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSpin-on oil filter, paper element air filter:\u003c\/strong\u003e Automotive-style replaceable filters — no special tools, widely available replacements.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAir\/oil lines in off-shelf copper piping:\u003c\/strong\u003e No proprietary tubing or fittings to source. Standard copper fittings available at any plumbing or HVAC supply.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAir-cooled aftercooler\/oil cooler standard:\u003c\/strong\u003e Removable for cleaning. Keeps oil temperature in check and reduces moisture carryover in the compressed air.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHour meter standard:\u003c\/strong\u003e Tracks actual run hours for accurate maintenance scheduling.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e10-minute shutdown timer:\u003c\/strong\u003e If no air is demanded for 10 minutes, the unit shuts down automatically, saving electricity during slow periods.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePressure ranges available:\u003c\/strong\u003e Standard 135 PSI; optionally ordered at 150 or 175 PSI to match your system requirements.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2-year warranty on air end, electric motor, and tank\u003c\/strong\u003e (where applicable)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eAvailable Configurations — Castair Rotary Screw Lineup\u003c\/h3\u003e\n\u003cp\u003eThe R31BM50 is Castair's entry-point base mount rotary screw, paired with a 50-gallon tank. For reference, the full single-phase rotary screw lineup with tanks:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e5HP, 1-Phase, 80 Gal Vertical (R518VP75):\u003c\/strong\u003e 20 CFM @ 100 PSI — 480 lbs\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e5HP, 1-Phase, 80 Gal Horizontal (R518HP75):\u003c\/strong\u003e 20 CFM @ 100 PSI — 480 lbs\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e7.5HP, 1-Phase, 80 Gal Vertical (R718VP75):\u003c\/strong\u003e 31 CFM @ 100 PSI — 555 lbs\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e7.5HP, 1-Phase, 80 Gal Horizontal (R718HP75):\u003c\/strong\u003e 31 CFM @ 100 PSI — 555 lbs\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eContact us to discuss which configuration fits your actual CFM demand and facility layout.\u003c\/p\u003e\n\n\u003ch3\u003eWhen Does a Shop Need This vs. Stepping Up or Down?\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRight for:\u003c\/strong\u003e Light commercial shop with an existing receiver tank, 1-2 lift bays, air tools running intermittently. Tire shop, small lube shop, or single-bay garage with existing air infrastructure.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStep up if:\u003c\/strong\u003e You're running impact wrenches, air ratchets, and spray guns simultaneously. A 3HP rotary screw will keep up with one tech working steadily, but two techs running air tools at the same time will likely outrun it. Move to 5HP or 7.5HP with an 80-gallon tank.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStep down if:\u003c\/strong\u003e You only need compressed air for occasional tire inflation or intermittent hand tools. A piston compressor at lower cost may be sufficient for truly light use.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBase mount is right when:\u003c\/strong\u003e You have a functioning receiver tank already in place and just need a better head unit. Swapping in a rotary screw base mount on an existing tank is a cost-effective shop upgrade.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eModel:\u003c\/strong\u003e R31BM50\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHorsepower:\u003c\/strong\u003e 3 HP\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePhase:\u003c\/strong\u003e 1-Phase\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConfiguration:\u003c\/strong\u003e Base mount (no tank)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSuggested Receiver:\u003c\/strong\u003e 50 gallon\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompressor Type:\u003c\/strong\u003e Rotary screw\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDuty Cycle:\u003c\/strong\u003e 100%\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandard Pressure:\u003c\/strong\u003e 135 PSI (150 or 175 PSI available)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLubrication:\u003c\/strong\u003e Oil-injected, synthetic lubricant (4,000-hour \/ 1-year interval)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDrive:\u003c\/strong\u003e Belt drive, standard V-belts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMotor Speed:\u003c\/strong\u003e 1725 RPM industrial motor\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eControls:\u003c\/strong\u003e Single solenoid, magnetic starter (pre-wired), hour meter, 10-minute auto shutdown timer\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWarranty:\u003c\/strong\u003e 2-year on air end and electric motor\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Castair (Spicer, Minnesota)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eDetailed CFM, dimensions, and weight specifications are pending manufacturer confirmation. Contact us for the latest data sheet.\u003c\/em\u003e\u003c\/p\u003e\n\n\u003ch3\u003eWhat's in the Box\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eCastair rotary screw compressor assembly (air end, motor, belt drive, base frame)\u003c\/li\u003e\n\u003cli\u003ePre-wired magnetic starter and controls\u003c\/li\u003e\n\u003cli\u003eAir\/oil separator with spin-on filter\u003c\/li\u003e\n\u003cli\u003eAir-cooled aftercooler\/oil cooler\u003c\/li\u003e\n\u003cli\u003eHour meter\u003c\/li\u003e\n\u003cli\u003ePre-filled with Cast-Lube synthetic oil\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eTank not included. Receiver tank sold separately.\u003c\/em\u003e\u003c\/p\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCastair specialist:\u003c\/strong\u003e We know this line top to bottom — base mount configurations, tank sizing, voltage options, and maintenance kits.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on qualifying orders\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree technical support:\u003c\/strong\u003e Call 866-217-0063 and talk to someone who understands rotary screw compressors and shop air systems\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e honored and supported\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHonest guidance:\u003c\/strong\u003e If a different model fits your shop better, we'll tell you\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342580965589,"sku":"R31BM50","price":0.0,"currency_code":"USD","in_stock":true}],"url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-3hp-rotary-screw-base-mount-compressor-r31bm50","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}