What a 12.5 kg Grease Pump Is
A 12.5 kg grease pump (27.5 lb) mounts on a standard grease keg or bucket and pumps grease through a hose and coupler to the machine. Two drives cover the format: a manual lever and plunger for sites without compressed air, and a pneumatic 50:1 intensifier for continuous workshop dispensing. Both seal the keg with a drum cover and press a follower plate onto the grease, so the inlet stays primed through the whole pail instead of starving as the level drops. The bigger 20 kg format has its own page, linked in the applications section below. Range context sits on the grease pump page and in the complete guide to grease pumps.
Operating Principle: the Follower Plate
The working heart of the pump is not the piston; it is the follower plate. The plate descends by gravity with a perimeter wiper seal that keeps continuous contact with the grease surface, holding positive inlet pressure as the keg empties. Close radial clearance under 0.5 mm between the plate and the pail inner wall prevents grease from bypassing the plate and breaking that contact. If the factory foil seal is not removed completely before the plate is inserted, the plate stalls on the foil and pressure drops mid-pail. On pneumatic models a relief valve on the drum cover prevents over-pressurization of the pail during high-speed dispensing.
Technical Specifications
The manual and pneumatic versions share the body and the pail interface; the drive and the numbers around it differ. At 7 bar (100 psi) air supply, the 50:1 pneumatic pump gives 350 bar (5,000 psi) at the outlet.
| Item | Manual | Pneumatic |
|---|---|---|
| Maximum output pressure | 240-350 bar (3,500-5,000 psi) | up to 345 bar (5,000 psi) |
| Drive | lever and plunger | compressed air, 50:1 ratio |
| Air supply required | not applicable | 4-8 bar (60-120 psi) |
| Air consumption | not applicable | about 4-6 CFM at rated pressure; minimum free air delivery 4 CFM (113 L/min) |
| Output | about 1.0-1.2 cc per stroke | continuous flow |
| Grease compatibility | NLGI 000-2, NLGI 2 standard | NLGI 000-2, NLGI 2 standard; NLGI 3 on verified models only |
| Viscosity limit | up to 1,200 cSt at pump inlet temperature | up to 1,200 cSt at pump inlet temperature |
| Air inlet thread | not applicable | 1/4″ NPT or BSP, model dependent |
| Pump body | carbon steel body, chrome-plated cylinder bore | carbon steel body, chrome-plated cylinder bore |
| Operating temperature | -20°C to +80°C | -20°C to +80°C |
| Outlet | 4-jaw snap coupler on 1/4″ high-pressure hose | 4-jaw snap coupler on 1/4″ high-pressure hose |
NLGI Grade Reference
NLGI runs from 000, the softest grade, to 3, the stiffest; the table maps each grade to its usual work. Grade availability varies by model, so verify against the specification table above.
| NLGI grade | Consistency | Typical use |
|---|---|---|
| 000/00 | semi-fluid | centralized systems, gearboxes; confirm inlet bore at least 12 mm |
| 1 | soft | cold-climate bearings; compatible with most models |
| 2 | firm | wheel bearings, chassis, general machinery; standard on all models |
| 3 | semi-solid | high-temperature slow-speed bearings; pneumatic models only, verify |
Semi-fluid grades flow easily but need the bore confirmed; the stiffest grades need the pneumatic drive and a verification step.
Drum Cover and Follower Plate Notes
The drum cover fits pail inner rims of 287-310 mm, which covers standard kegs, but rim sizes vary so measure the keg before ordering. The lines these pumps feed have their own selection logic, covered in the grease line tubing and fittings selection guide. Grease switching deserves care: lithium and calcium sulfonate greases are generally incompatible, and mixing causes thickener breakdown and oil separation. Purge the pump and hose completely when switching grease types, and dedicate one pump per grease type for critical applications. For any new grease, confirm seal compatibility with the grease data sheet before ordering.
Applications and Industries
Automotive workshops grease wheel bearings, chassis points, and ball joints. Construction sites run bucket pins, articulation joints, and blade pivots in high dust. Agriculture covers PTO shafts, header pivots, and baler bearings, often with no compressed air on site, which is where the manual lever earns its place. Fleet depots hit kingpins, fifth-wheel plates, and U-joints. Industrial plants service motor bearing housings, conveyor roller fittings, and press guide rails. Where air is available and volume is higher, the pneumatic drive covered on the air grease pump page is the faster tool, and the 20 kg grease pump covers the bigger pail. To match drive, keg, and coupler, send the details through the contact page.
Frequently Asked Questions
What does the 50:1 ratio mean?
The ratio multiplies inlet air pressure into grease outlet pressure. At 7 bar (100 psi) air supply, 50:1 gives 350 bar (5,000 psi).
Why does pressure drop mid-pail?
A worn follower plate wiper seal, an unsealed drum cover, or a tired inlet ball valve seat lets air in. An air supply under 4 bar shows the same symptom.
Can it handle synthetic or EP greases?
Usually, but confirm seal compatibility with the grease data sheet before ordering. Do not assume every thickener system behaves the same.
What is the minimum compressor output?
Regulate the supply to 4-8 bar and provide at least 4 CFM (113 L/min) free air delivery. Consumption runs about 4-6 CFM at rated pressure.
How do I match the coupler?
The 4-jaw snap coupler fits standard hydraulic grease nipples used globally. Some European and Asian points use button-head flush-face couplers; use rated adapters only.
Can one pump serve several grease types?
No, lithium and calcium sulfonate greases are generally incompatible, and mixing breaks the thickener down. Purge pump and hose fully, or dedicate one pump per grease type.
What thread is the air inlet?
It is 1/4″ NPT or BSP depending on the model. The two are not interchangeable, so confirm the thread before ordering.
Which NLGI grades can it pump?
Manual and pneumatic models cover NLGI 000 to NLGI 2, with NLGI 2 the standard grade. NLGI 3 runs on verified pneumatic models only.
Should I choose a 12.5 kg or a 20 kg keg pump?
The 12.5 kg keg suits lower-volume and mobile work. For bigger pails, see the 20 kg grease pump, or contact us to compare.
Who builds these pumps?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
