SKF 6212-2Z/VA228 High Temperature Ball Bearing

A shielded, graphite-lubricated ball bearing for ovens, kilns and hot conveyors

The SKF 6212-2Z/VA228 is a single row deep groove ball bearing for high temperature applications, with shields on both sides and a 60 mm bore, 110 mm outside diameter and 22 mm width. The VA228 version is SKF top-performance high temperature variant: it carries a graphite coronet cage and an adjusted radial internal clearance, and it is designed to run at temperatures up to 350 degrees C (660 degrees F) without grease.

The SKF brochure describes the typical failures this solves: grease that thins and runs out, grease that ages and carbonises, and loss of internal clearance when parts expand at high temperature. The graphite does not age and does not lose its lubricating properties at temperatures up to 350 degrees C, so the bearing needs no relubrication. The brochure shows applications such as cooling beds for steel plates, continuous baking ovens, wafer baking ovens and paint lines.

Technical specifications

VA201, VA208 and VA228 compared

The brochure compares three variants. VA201 uses a polyalkylene glycol and graphite mixture for up to 250 degrees C and needs running in; the open version can be relubricated. VA208 has a segmented graphite cage and VA228 a coronet cage made of graphite, both for up to 350 degrees C, both NSF H1 food grade, relubrication free and with no running in required. Limiting speed is stated as 4 500 over the mean diameter dm for VA201 and VA208 and 9 000 over dm for VA228, where dm is the bearing mean diameter.

VA228 is described as an excellent choice for machinery operating at low speeds or oscillating movements in combination with very high temperatures. For this size the product table gives a limiting speed of 100 r/min, consistent with the 9 000 over dm rule (dm is 85 mm). This is a slow-speed bearing and should not be selected for fast rotation.

Selection and ordering notes

Boundary dimensions correspond to ISO standard bearings, so the bearing replaces a standard 6212 without housing changes. All surfaces of the bearing and shields are manganese phosphate treated to improve lubricant adhesion and running in. The product page gives a static load rating of 36 kN, a shaft abutment of 69 to 75.4 mm and a housing abutment of at most 101 mm; the SKF brochure lists a mass of 0.81 kg. A dynamic load rating is not given on the product page.

Confirm the real temperature, the speed, the load and whether the machine requires a food-grade lubricant. See Electric Motors for other bearings on this site, and the SKF TKRT 31 tachometer to check rotation speed on site. Seven Star LLC lists this part number for quotation only; operating conditions remain your responsibility.

Documents and quotation

The attached SKF high temperature bearings brochure contains the variant comparison, the lubrication and running-in notes, and the product tables with this designation. The product page supplies the dimensions in the table. Seven Star LLC, an independent supplier in Muscat, will quote on the designation and quantity you send.