ISOFLEX TOPAS NB 5051 vs SKF LGHP 2: bearing grease comparison
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ISOFLEX TOPAS NB 5051 or SKF LGHP 2: which grease fits?
They answer different design briefs. ISOFLEX TOPAS NB 5051 (Klüber article number 004128) is a dynamically light long-term grease on synthetic hydrocarbon oil with a barium complex thickener, documented for low starting and running torque, plain and rolling bearings, small gears where it reduces gear noise, precision gears and the running-in lubrication of plastic and composite bearings, with a service range of -60 to +150 °C. SKF LGHP 2 is a mineral oil based grease with a di-urea thickener for medium and high speed ball and roller bearings at medium and high temperatures, documented especially for electric motors, with a range of -40 to +150 °C. Choose from the bearing manufacturer's specification and the operating data, rather than from the temperature ratings alone.
The two greases side by side
| Property | ISOFLEX TOPAS NB 5051 | SKF LGHP 2 |
|---|---|---|
| Base oil | Synthetic hydrocarbon oil | Mineral oil |
| Thickener | Barium complex soap | Polyurea (di-urea) |
| Consistency | Worked penetration 385 to 415 (0.1 mm, 25 °C, acc. to Klein) | NLGI class 2-3, penetration 245 to 275 (0.1 mm, 60 strokes) |
| Service temperature range | -60 to +150 °C | -40 to +150 °C |
| Base oil kinematic viscosity at 40 °C | approx. 30 mm²/s (approx. 5.9 mm²/s at 100 °C) | 96 mm²/s (10.5 mm²/s at 100 °C) |
| Drop point, DIN ISO 2176 | ≥ 170 °C | > 240 °C |
| Corrosion protection | SKF-EMCOR ≤ 1 (distilled water, 1 week) | Emcor 0-0 standard, water washout 0-0, salt water 0-0 (per SKF catalogue) |
| Oil separation, DIN 51817, 7 days at 40 °C | not stated on the cited product information | ≤ 3 % |
| Flow pressure, DIN 51805 | ≤ 1,400 mbar at -60 °C | not stated in the cited catalogue |
| DIN 51825 code | not published on the product page | K2N-40 |
| Colour | Beige | Blue |
| Minimum shelf life, unopened | approx. 36 months | 5 years |
Scroll the table horizontally to view all columns.
Sources: Klüber product page for ISOFLEX TOPAS NB 5051 with the Klüber product information for article number 004128; SKF Maintenance and Lubrication Products catalogue, LGHP 2 section. Confirm current values in the datasheets supplied with delivery.
Two different design briefs
NB 5051 is built around low starting and running torque and a wide temperature window down to -60 °C. Klüber documents it for plain and rolling bearings, for gas meters, for small gears where it reduces the noise produced by the gear wheels, for tooth flanks in precision gears such as bevel gears in milling machines and electromechanical valve actuators, and as running-in lubrication for plastic and composite bearings. The low base oil viscosity of about 30 mm²/s is what buys the low torque; it also means thin films, so the load on the bearing has to stay light relative to its size.
LGHP 2 is built around long grease life at high temperature in loaded bearings. SKF documents it for electric motors of all sizes, industrial fans including high speed fans, water pumps, rolling bearings in textile, paper processing and drying machines, clutch release bearings, vertical shaft applications and kiln trucks. The mineral oil with a 96 mm²/s base oil viscosity carries a thicker film; the di-urea thickener and a dropping point above 240 °C are what hold the structure at temperature, with an SKF ROF test L50 life of at least 1,000 hours at 10,000 min⁻¹ and 150 °C documented in the catalogue.
On food registration: SKF's food-grade grease line is LGFG 2, formerly LGFP 2. The catalogue section for LGHP 2 shown here does not list NSF H1 registration, so if a lubrication point requires an H1 lubricant, verify the current SKF documentation or the NSF registry before standardising on it. Klüber does not claim H1 for NB 5051 either.
Checking speed and load
The two numbers that decide most cases are the viscosity ratio (kappa) at operating temperature and the speed factor the bearing needs. NB 5051's thin base oil suits small, lightly loaded bearings and gears where drag must stay low; when kappa falls well below 1 at the actual operating temperature, the film gets marginal and a higher-viscosity grease should be considered. LGHP 2's higher viscosity suits medium speeds and steady loads; in small high-speed bearings it adds churning heat, which is why the bearing manufacturer's speed and fill guidance matters more than any single rating.
Example: two bearings in one plant
A small plastic gear train inside a metering device needs low breakaway torque and compatibility with plastic: NB 5051's documented profile, including its use as running-in lubrication for plastic bearings, matches. A 90 kW fan bearing running hot in a dusty corner needs the long-life-at-temperature profile: that is LGHP 2's documented territory, provided the fan manufacturer's grease spec agrees. The mistake to avoid is standardising the whole plant on one of them because one rating looked impressive.
Changing between them
A barium complex grease and a polyurea grease are different thickener systems. Purge the old grease from the housing as completely as practical when switching in either direction, and do not top up one with the other. SKF notes compatibility of LGHP 2 with common polyurea and lithium greases; that statement covers named systems, not every grease on the shelf, so for an unlisted combination ask the lubricant manufacturer. Klüber recommends compatibility tests with elastomers and plastics before series application of NB 5051, which is worth doing anyway for small precision assemblies.
Common questions
Is ISOFLEX TOPAS NB 5051 a high-speed spindle grease?
Klüber documents it as a dynamically light grease with low starting and running torques, wide temperature range and uses in small and precision gears. The product information does not position it as a spindle bearing grease. For machine tool spindles, check the speed factor against the bearing's requirements at the operating temperature, and compare Klüber's spindle grease documentation before deciding.
Is SKF LGHP 2 NSF H1 registered?
Verify it for the batch you buy. SKF's dedicated food-grade grease is LGFG 2 (formerly LGFP 2), and the catalogue page for LGHP 2 summarised here does not carry an H1 statement. Where incidental food contact is possible, confirm the registration in the current SKF documentation or the NSF White Book, or specify an explicitly H1 registered product.
Which one handles cold starts better?
NB 5051 documents the lower limit and the evidence for it: -60 °C service temperature and a flow pressure of at most 1,400 mbar at -60 °C. For equipment that must start reliably in cold stores or unheated buildings, that is a documented cold-start figure, not a marketing claim.
Can the two be mixed or topped up against each other?
No. Different thickener systems can soften or harden when mixed. Purge when changing over, and keep the blue and beige greases on separate labelled equipment so lubrication rounds cannot mix them by accident.
Which suits an electric motor bearing?
LGHP 2 is documented by SKF for electric motors of small to large frame sizes, with long life at high temperature. NB 5051 suits small, lightly loaded bearings where low torque matters more than load-carrying. The motor manufacturer's lubrication table is the final reference for fill quantity and interval.
Order the grease the specification calls for
Send the bearing type, speed and temperature, the current grease if you are changing over, and the quantity. We will quote with the current product information and safety data sheet.
Manufacturer references
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