HEB Number of Calipers Product Selection Number of Pads Torque at 60 psi (414 kPa) lb-in (Nm) Coefficient of friction of pads Torque at 80 psi (552 kPa) in lb-in (Nm) Coefficient of friction pads Low (0.12) Med (0.41) High (0.51) Low (0.12) Medium (0.41) High (0.51) 1 2 290 (33) 1007 (114) 1174 (133) 387 (44) 1343 (152) 1565 (177) 2 4 580 (66) 2014 (228) 2348 (265) 773 (87) 2685 (303) 3131 (354) 3 6 870 (99) 3021 (341) 3522 (398) 1160 (131) 4028 (455) 4696 (531) 4 8 1160 (132) 4028 (455) 4696 (531) 1547 (175) 5371 (607) 6261 (707) 5 10 1450 (164) 5035 (569) 5870 (663) 1933 (218) 6713 (759) 7827 (884) 6 12 1740 (197) 6042 (683) 7044 (796) 2320 (262) 8056 (910) 9392 (1061) We recommend sizing the brake using values at 60 psi and medium coefficient of friction pads. Step 1. Determine torque requirement in lb-in from maximum tension and maximum roll diameter. Torque = Tension (pounds) x Radius (inches) at full roll Maximum Line Speed (fpm) 2 x pi x r (r is radius in feet at full roll) Step 3. Determine thermal heat dissipation required. Thermal horsepower = Pneumatic Brakes Step 2. Determine RPM for full roll. RPM at full roll diameter = Torque at full roll diameter (in inch-pounds) x RPM at full roll diameter 63,000 Maximum Line Speed (fpm) Step 4. Determine Effective Average RPM = 3.14 ( Maximum Roll Diameter (feet) + Core Diameter (feet) 2 ) Step 5. Choose the number of calipers required from the chart above that will provide the torque required at the full roll diameter. Since not all facilities have a reliable air pressure source to supply the 80 or 90 psi full pressure rating to the brake, and as a factor of safety in initial applications, select the number of calipers required from the 60 psi table. Step 6. Verify that the thermal horsepower generated by the application can be dissipated by looking at the chart to the right and ensure that the calculated horsepower falls on or under the line at the Effective Average RPM calculated in Step 4. Pneumatic Brakes 91