Oberdorfer 4136C Stainless Steel Rotary Gear Pump — W88 Gears with Packed Seal
The Oberdorfer 4136C is a precision-built stainless steel pedestal gear pump designed for demanding fluid transfer tasks where corrosion resistance and consistent flow are non-negotiable. Fitted with W88 stainless alloy helical gears — a specialty non-galling alloy created specifically for metal-on-metal gear contact — this pump delivers smooth, quiet, positive displacement flow across a broad range of viscosities. The packed shaft seal configuration makes it well-suited for applications where a traditional packing arrangement is preferred over mechanical or lip seals, particularly in systems involving solvents, process chemicals, lubricants, or other industrial fluids that benefit from adjustable packing compression.
As a pedestal-style (shafted) pump end, the 4136C is intended for base-mount assemblies with long coupling to a separately powered motor, giving engineers and maintenance crews the flexibility to pair it with the drive system that best fits their installation. The stainless steel construction handles fluids with a pH range from 4 to 11 and temperatures up to 450°F, while the helical gear design reduces operating noise by up to 10 dB compared to spur gear alternatives. Whether used in chemical processing, industrial fluid handling, lubrication systems, or OEM equipment, the Oberdorfer 4136C delivers the durability and reliability that has made Oberdorfer a trusted name in rotary gear pump manufacturing for over a century.
Key Features
- W88 stainless alloy helical gears — non-galling, precision-machined for quiet operation (noise reduction up to 10 dB)
- Stainless steel housing and shaft for excellent corrosion resistance
- Packed shaft seal design — field-adjustable packing for a wide variety of fluid service environments
- External gear positive displacement design — consistent, pulseless flow proportional to shaft speed
- Three-section, O-ring sealed thru-bolt construction for ease of service and parts replacement
- Bi-directional operation — suction and discharge ports can be reversed by changing motor rotation
- Self-priming with suction lift capability up to 20 feet (new pump)
- Carbon bearings — self-lubricating, no external lubrication required
- Compatible with lubricating and non-lubricating fluids
- Pedestal (shafted pump end) configuration for base-mount, long-coupled motor installations
Applications
- Industrial chemical transfer and processing
- High-viscosity fluid handling (oils, glycols, solvents, resins)
- Lubrication system supply and recirculation
- Process fluid metering and dosing
- OEM equipment fluid circuits
- Agriculture fluid transfer operations
- General-purpose corrosive liquid pumping
Specifications
- Part Number: 4136C
- Pump Type: External rotary gear, positive displacement
- Housing Material: Stainless steel
- Shaft Material: Stainless steel
- Drive Gear Material: W88 stainless alloy
- Idle Gear Material: W88 stainless alloy
- Gear Type: Helical
- Bearings: Carbon graphite (self-lubricating)
- Seal Type: Packed shaft seal
- Mount Style: Pedestal (shafted pump end — motor not included)
- Port Size: 3/4 in. NPT (Suction and Discharge)
- Maximum Differential Pressure: 150 PSI (metal/metal gear combination)
- Maximum Operating Temperature: 450°F
- Maximum Viscosity: 100,000 cps (462,000 SSU) at reduced shaft speed
- Maximum Shaft Speed: 1,750 RPM
- Suction Lift: Up to 20 feet (new pump)
- Relief Valve: Not included — external relief valve required
- pH Range: 4 to 11
Note: Picture is representation of pump
Frequently Asked Questions
Q: What does the W88 gear material mean, and why does it matter?
W88 is a proprietary non-galling stainless steel alloy developed for metal-on-metal gear applications. Unlike standard 316 stainless, W88 is formulated to resist the adhesive wear and surface damage that occurs when two stainless steel components rotate in direct contact under load. This makes it significantly more durable in gear pump applications where both the drive and idle gears are metallic.
Q: Is the 4136C a complete pump unit, or just the pump end?
The 4136C is a pedestal-style shafted pump end only. It is designed for base-mount assembly with a separately provided motor connected via a long coupling arrangement. A motor is not included and must be sourced and matched separately based on the required speed and horsepower for the application.
Q: Why does this pump require a pressure relief valve, and where is it installed?
Because the 4136C is a positive displacement pump, it displaces a fixed volume of fluid with every shaft revolution regardless of downstream conditions. If a valve closes or a blockage occurs, pressure will continue to rise until something fails. A relief valve installed on the discharge side protects both the pump and system piping from overpressure events. The valve is not included and must be added externally.
Q: Can the 4136C handle fluids that do not have lubricating properties?
Yes. The 4136C is rated for both lubricating and non-lubricating fluids. However, service life is notably extended when the pumped fluid has some degree of lubricity and is free from fine abrasives such as sand, silt, or particulates, which can accelerate internal wear in a close-tolerance gear pump.
Q: Can the flow direction be reversed on this pump?
Yes. The 4136C supports bi-directional operation. To reverse the flow direction — effectively swapping the inlet and discharge ports — simply reverse the motor rotation by following the wiring instructions for the connected motor. No mechanical changes to the pump itself are required.
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