Bright Stock BS-MVI

About This Product

Blenders seldom put Bright Stock BS-MVI into a formulation by itself; its value lies in what a measured share does to a lighter base. Even a modest proportion mixed into the 400N-HVI or 500N-HVI lifts viscosity a long way, which is how thick gear oils and heavy monograde engine oils are made, and a blend with the 650N-MVI remains wholly in the medium-VI class for steam and cylinder oils. In every case the aim is to get heavy viscosity and a strong film from the base oil instead of a polymer. Because no other grade in the range has a lower viscosity index, a formulator working towards a high finished VI should add no more than the viscosity target calls for.

Marine cylinder oils show the principle at work. For large slow-speed crosshead engines they are formulated from heavy neutrals, bright stock and a high-alkalinity additive package, and the bright stock is what lets the oil film hold up on hot cylinder liners. Open gear compounds and wire rope dressings draw on its tackiness, which helps them resist being thrown off or washed away. Grease makers select it for bearings that run hot, slow and heavily loaded, and gear oil blenders need it for the heaviest industrial viscosity grades.

The figures are those of a residual oil. Kinematic viscosity is 35.0 – 42.0 cSt at 100 °C, more than three times that of the heaviest distillate neutral in the range, while a viscosity index of min 75 places it in the medium-VI class, as expected of a residual stock containing many large ring molecules. At min 280 °C (COC), its flash point is the highest of any base oil offered here. The pour point limit is max -3 °C and total acid number max 0.05 mg KOH/g. Colour may reach ASTM 6.0, darker than a distillate would be, which has no practical consequence in cylinder oils, greases or open gear lubricants.

Whereas the neutral grades are vacuum distillates, bright stock starts as vacuum residue, the heavy material left at the bottom of the column once the neutral cuts are distilled off. Deasphalting, normally with liquid propane, precipitates asphaltenes and resins; extraction, dewaxing and finishing of the deasphalted oil then follow broadly as for the neutrals. Set beside the black residue it came from, the product is clear and bright, hence its name.

BG Petro Chemicals supplies Bright Stock BS-MVI of Pakistan origin, with indicative availability of 1,000 – 2,000 MT per month. Because the oil is so viscous, bulk or ISO tank deliveries may need heating before discharge; drums, IBC tanks and flexi bags are also offered, and custom packaging can be supplied. Every lot ships with a certificate of analysis, and the technical datasheet and SDS are available on request.