Cat Pump 277 Plunger Pump 3 Frame — Model 277 Triplex High Pressure Pump
The Cat Pump 277 is a three-plunger positive displacement pump built on the compact 3 Frame platform, and it earns its place in systems where the liquid being moved would chew through an ordinary pump. Nickel aluminum bronze manifolds and 316 stainless steel valve assemblies give it real corrosion resistance, which is why you find this model handling deionized water, seawater, mild chemical solutions, and treated process water just as readily as ordinary tap water. Solid ceramic plungers ride against NBR seals to deliver a steady 3.5 GPM at pressures up to 1500 PSI, and because the flow is positive displacement, that output stays consistent as system pressure rises rather than falling off the way a centrifugal pump would.
Sizing and installation are straightforward. The pump turns at 1420 RPM with two 1/2" NPT(F) inlet ports and two 3/8" NPT(F) discharge ports, so plumbing can come off whichever side suits the frame layout, and the unused ports are simply plugged. It accepts belt, clutch, flexible coupling, or bellhousing drive, which makes it easy to pair with an existing electric motor or gas engine instead of redesigning the whole assembly around a specific pump. At 13.4 pounds and just over ten inches long, it fits skids, carts, and enclosures where a larger frame simply will not go.
Where the 277 really pays for itself is service life. The oil-bath crankcase, replaceable seal packs, and hydraulically opened valve design mean this is a pump you rebuild rather than replace, and parts stay available for the long haul. Reverse osmosis skids, misting and fogging systems, hydrostatic test rigs, industrial washdown lines, humidification equipment, and evaporative cooling systems all lean on this model for the same reason: it runs continuous duty without drama, and when the seals eventually wear, a kit and an afternoon put it back into service.
Key Features
- Triplex positive displacement design for smooth, consistent flow under varying pressure
- Nickel aluminum bronze manifold for excellent corrosion resistance in aggressive liquids
- 316 stainless steel valve assemblies, spring-loaded closed and hydraulically opened
- Solid ceramic plungers for long wear life and low friction
- Standard NBR (Buna-N) seals and O-rings, with alternate seal materials available
- Oil-bath crankcase with sight-glass style fill and integrated oil drain
- Accepts belt, clutch, flexible coupling, or bellhousing drive configurations
- Dual inlet and dual discharge ports for flexible plumbing on either side
- Field-serviceable seal packs, valves, and plungers for full rebuildability
- Compact, lightweight 3 Frame footprint for skid, cart, and enclosure mounting
Applications
- Reverse osmosis and water treatment systems
- High-pressure misting, fogging, and humidification
- Evaporative and industrial cooling
- Hydrostatic testing and pipeline flushing
- Industrial and commercial washdown
- Pressure washing and surface cleaning equipment
- Chemical injection and transfer of compatible fluids
- Car wash and vehicle wash systems
- Agricultural spraying and dust suppression
- Wellhead service and general industrial process water duty
Specifications
- Model: 277
- Frame: 3 Frame
- Type: Triplex positive displacement plunger pump
- Flow Rate: 3.5 GPM (13.2 LPM)
- Pressure Range: 100 to 1500 PSI (6.9 to 103 bar)
- Maximum Pressure: 1500 PSI
- Pump Speed: 1420 RPM
- Inlet Port Size: 2X 1/2" NPT(F)
- Discharge Port Size: 2X 3/8" NPT(F)
- Inlet Pressure Range: Flooded to 60 PSI (4.1 bar)
- Plunger Bore: 0.709" (18 mm)
- Stroke: 0.500" (12.7 mm)
- Shaft Diameter: 0.650" (16.5 mm)
- Crankcase Oil Capacity: 15 oz (0.44 liters)
- Manifold Material: Nickel aluminum bronze
- Valve Material: 316 stainless steel
- Plunger Material: Solid ceramic
- Seals and O-Rings: NBR (Buna-N) standard
- Maximum Liquid Temperature: 160°F (71°C) with NBR seals
- Drive Options: Belt, clutch, flexible coupling, bellhousing
- Dimensions: 10.28" x 8.78" x 5.35" (261 x 223 x 136 mm)
Frequently Asked Questions
Q: Does the Cat Pump 277 come with a motor or is it a pump end only?
A: The 277 is supplied as a bare pump end. It has no motor, pulley, or base attached, which lets you match it to the electric motor or gas engine your system already uses through a belt, clutch, flexible coupling, or bellhousing drive.
Q: What direction can the Cat Pump 277 rotate?
A: The 277 runs in either direction. Crankshaft rotation is bidirectional, so mounting orientation and drive layout will not force you into a specific shaft direction.
Q: Do I need a relief valve or unloader with this pump?
A: Yes. Every high-pressure system built around the 277 requires a primary pressure regulating device such as a regulator or unloader, plus a secondary pressure relief device sized to the pump. Without both, deadheading the pump can damage equipment or cause injury.
Q: What oil does the crankcase take and how often should it be changed?
A: The crankcase holds 15 ounces of Cat Pumps ISO 68 hydraulic crankcase oil. Change it after the first 50 hours of break-in, then every 500 hours or every three months under normal continuous duty.
Q: Can the 277 be run at speeds other than 1420 RPM?
A: It can. The 277 is also offered in an alternate specification rated for 4.2 GPM at 1000 PSI running at 1725 RPM. Flow scales with shaft speed, so pulley sizing lets you tune output within the pump's rated limits.
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