A critical link
- November 10, 2014
Grinding wheel flanges and personal safety
Even experienced grinding wheel users may not realize the importance of wheel mounting procedures and equipment as they relate to personal safety. To illustrate this, consider an analogy of wheels on a car, which are similar to mounting flanges on a grinder in that both transmit rotation by linking a shaft to an outer component (namely, to a tire or a grinding wheel). Imagine you are driving a car at 160 km/hr and you suddenly sense the wheels are damaged or not properly attached. Danger! Any driver would rightly feel unsafe and stop
the car immediately.
Now imagine you operate a grinder whose grinding wheel rotates at 160 km/hr (45 m/s or 8,860 sfpm), and you stand beside that wheel for hours at a time. Would you feel safe if you had reason to suspect that the mounting flanges were damaged, poorly attached, or improperly designed?
The stresses produced by poor mounting procedures and damaged equipment can cause wheels to break, and broken wheels can cause serious injuries to operators and bystanders. Like car owners, grinding wheel users should regularly check their equipment to detect mounting problems before they develop into more serious hazards. Useful guidelines for proper procedures and equipment are given in the American National Standards Institute Requirements for the Use, Care and Protection of Abrasive Wheels (more commonly, ANSI B7.1). For example, the ANSI B7.1 requirements
for flanges cover:
• Flange shapes and dimensional requirements differ by application.
• Flange material must meet given strength and rigidity standards.
• Most flanges require recesses to concentrate the clamping pressure on a precise area.
• Some flanges require undercuts to provide extra clearance near the bore of the grinding wheel.
• Flange pairs generally must be uniform in diameter to prevent cross-bending stresses.
• Flanges must be maintained in good condition with respect to flatness, surface condition (free of burrs and foreign particles), balance, wear, and truth.
• Flange flatness should be checked with and without grinding wheels mounted.
• New blotters (compressible washers) must be used every time a wheel is mounted, unless they are attached to the wheel by the manufacturer.
Blotters are necessary for safe mounting. Besides their primary benefits such as preventing the flanges from slipping and protecting against wear from the abrasive wheel, they have another valuable function. Since blotters are compressible by design, they take on impressions from the flanging surfaces that provide information about the mounting situation. So next time you perform a wheel change, check the used blotter for the following:
• Complete Contact –the blotter should show evidence of complete and consistent flange contact over the entire bearing surface.
• Concentrated Pressure –the blotter impressions should be even and not indicate concentrated or insufficient flange pressure.
• Evidence of Movement –the blotter should display no signs of slipping or other movement of the grinding wheel inside its flanges. Scratches, tears, or other wear marks may indicate there has been movement.
Careful design and periodic inspection of grinding wheel mounting equipment and procedures are critical to a safe operation. Additionally, examination of used blotters is an easy and valuable way to check for potential mounting problems that can develop into a serious hazard if not addressed. Be aware of the risks associated with poor mounting, and be proactive in your approach to abrasive safety. SMT
Ethan Weikleenget is senior product engineer with Norton|Saint-Gobain.