Robbins & Myers 340-3501-120 Nitrile Stator for Moyno 500 Model 331
Part number 340-3501-120 is the genuine NBR nitrile replacement stator for the Moyno 500 Model 331 and the 41502 grinder pump. Everything a progressing cavity pump does well depends on the interference fit between this elastomer bore and the rotor: the tighter the seal line, the higher the pressure the pump can hold and the less liquid slips back down the pump.
Stators fail in three recognizable ways. Grit and suspended solids abrade the bore gradually, so output tapers off over months. An incompatible liquid attacks the compound chemically, leaving it swollen, sticky or brittle rather than worn. Running the pump dry destroys one in minutes, because the pumped liquid is what lubricates and cools the contact line. NBR nitrile covers a service range of roughly 10 to 160 F, so check the temperature of the liquid as well as its chemistry before settling on an elastomer. The same stator serves the 41502 grinder pump, which shares the 331 pumping element behind its cutter assembly.
Key Features
- Genuine Robbins & Myers Moyno replacement stator
- NBR nitrile elastomer construction
- Molded for the Moyno 500 Model 331 and the 41502 grinder pump pumping element
- Restores the rotor to stator interference fit that sets discharge pressure
- Brings flow and pressure back to the original duty point
- Approximate elastomer service range of 10 to 160 F
- Direct replacement with no machining or modification
Applications
- Moyno 500 Model 331 and the 41502 grinder pump progressing cavity pumps
- Restoring flow and discharge pressure that have fallen away gradually
- Rebuilding a pump after a dry running incident
- Changing elastomer compound to suit a different liquid
- Scheduled overhauls on metering and transfer duties
- Industrial, marine, dockside and washdown installations
Specifications
- Brand: Robbins & Myers
- Manufacturer: Robbins & Myers (Moyno)
- Manufacturer Part Number: 340-3501-120
- Part Type: Stator, progressing cavity pumping element
- Material: NBR nitrile
- Elastomer Service Range: approximately 10 to 160 F
- Quantity Used: One per pump
- Fits: Moyno 500 Model 331 and the 41502 grinder pump
- Condition: New
Frequently Asked Questions
Q: Does direction of rotation matter?
Yes. These pumps are built to turn one way, and running one backwards puts the discharge pressure on the suction side of the pump. Confirm rotation after any motor rewiring, before the pump is allowed to see liquid.
Q: Should the rotor be replaced at the same time?
If the rotor still has intact plating and no scoring it can be reused. Once the plating has worn through, the exposed base metal is rough enough to chew through a new stator quickly, so at that point the pair should be changed together.
Q: Can the pump be left standing full of liquid between runs?
Liquid sitting in the stator causes no harm. A pump left standing dry for a long period is the greater risk, because the elastomer can take a permanent set against the rotor. Turning the shaft by hand from time to time avoids that.
Q: Can the stator be changed without unbolting the pump from its base?
On the smaller Moyno 500 pumps the suction housing and stator come off the front while the pump stays bolted down, which is quicker than breaking the drive coupling. Leave clear space in front of the pump at least equal to the length of the stator so it can be drawn straight off.
Not sure this is the right part? Send us a Picture of the pump plate on your pump and the CLR Marine team will confirm the correct stator before you order.
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