Finish Thompson 105878 Drive Magnet Assembly, 6 Pole, 56C Frame
The 105878 is the outer drive magnet assembly for Finish Thompson DB11 and DB15 sealless magnetic drive centrifugal pumps built on a NEMA 56C motor frame with a six pole magnet ring. A mag drive pump has no mechanical shaft seal to wear out or weep: the motor turns this magnet carrier, and its field couples straight through the containment barrier to the magnet inside the impeller, so torque crosses into the wet end while the pumped chemical stays completely enclosed. The assembly arrives complete with its snap ring and the stainless set screws that lock it onto the motor shaft.
Drive magnets are most often replaced after a decoupling, when the pump has been run against a closed discharge, started under load, or asked to move a fluid past its viscosity limit and the two magnet sets slip out of step. The heat generated during that slip can permanently weaken the magnets, and the pump afterward makes less head than it should or stalls whenever the valve opens. Chipped or lifted magnets, a cracked carrier, scoring on the bore where it passes over the barrier, and set screw threads that no longer grip the motor shaft all mean a new assembly rather than a repair. Pole count and motor frame both have to match the pump as it was built, because a six pole ring on a 56C frame will not substitute for the eight pole version or for a 143 or 145TC frame part.
Key Features
- Six pole drive magnet assembly sized for NEMA 56C motor frames
- Supplied with the snap ring and stainless set screws needed to mount it
- Sealless magnetic coupling carries torque with no shaft seal to leak
- High energy neodymium magnets deliver full torque in a compact carrier
- Direct replacement for the factory fitted assembly on DB11 and DB15 pumps
Applications
- Finish Thompson DB11 and DB15 sealless magnetic drive centrifugal pumps
- Acid, caustic and solvent transfer where a leak path cannot be accepted
- Plating, etching, metal finishing and wastewater treatment systems
- Filter loops, scrubber recirculation and bulk tank transfer duties
- Rebuilding a pump after a magnet decoupling or a dry running incident
Specifications
- Brand: Finish Thompson
- Manufacturer Part Number: 105878
- Part Type: Drive Magnet Assembly with Snap Ring
- Pole Count: Six pole
- Motor Frame: NEMA 56C
- Included Hardware: Snap ring and stainless steel set screws
- Fits: Finish Thompson DB11 and DB15 series pumps
- Quantity Per Pump: 1
- Condition: New
Frequently Asked Questions
Q: Can a single chipped magnet be replaced on its own?
No. The magnets are bonded into a balanced carrier and the ring is supplied and serviced only as a complete assembly.
Q: What should be inspected before a new drive magnet goes on?
Check the containment barrier for cracks or rub marks, look at the impeller magnet for the same slip damage, and confirm the motor shaft and keyway are clean and unworn.
Q: Does the wet end have to be opened to change it?
No. The DB series is a back pull out design, so the clamp ring and motor adapter come off and the magnet slides from the motor shaft once the set screws are backed out.
Q: Will a higher pole count give the pump more torque?
Pole count is set by the motor speed and the coupling the pump was specified with, not by preference, so fitting a different ring changes the magnetic match rather than improving performance.
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 drive magnet assembly before you order.
CLRMarine
