A design for an industrial oven door has a 15-mm-diameter horizontal bar over the oven opening on which the door hangs. Two smooth cylindrical door hinges are lined with the graphite metalized bearing material listed in Table 16–1. The door weighs 20.40 kN and rotates 110° from vertical to 20° above horizontal as the door is opened to insert or withdraw parts to be heated. It then returns to the original position. The door is opened and closed five times per minute. Determine the required length of the hinges to produce a pV value no more than 25% of the limiting value.
| TABLE 16–1 Typical Performance Parameters for Bearing Materials in Boundary Lubrication at Room Temperature |
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| Material | pV | ||
| psi-fpm | MPa-m/s | ||
| Vespel® SP-21 polyimide | 300000 | 10.500 | Trademark of DuPont Co. |
| DP11™, oiled | 286000 | 10.020 | GGB Bearing Technology |
| Manganese bronze (C86200) | 150000 | 5.250 | Also called SAE 430A |
| Aluminum bronze (C95400) | 125000 | 4.375 | Also called SAE 68A |
| DX®10, dry or oiled | 80000 | 2.800 | GGB Bearing Technology |
| Leaded tin bronze (C93800) | 75000 | 2.625 | Also called SAE 660 |
| DU® | 51400 | 1.800 | GGB Bearing Technology |
| BU dry lubricant bearing | 51400 | 1.785 | See note 1 |
| Porous bronze/oil impregnated | 50000 | 1.750 | |
| Babbitt: high tin content (89%) | 30000 | 1.050 | |
| DP11™, dry | 28600 | 1.000 | GGB Bearing Technology |
| Babbitt: low tin content (10%) | 18000 | 0.630 | |
| Graphite/Metallized | 15000 | 0.525 | Graphite Metallizing Corp |
| Rulon® PTFE: 641 | 10000 | 0.350 | Food and drug applications (see note 2) |
| Rulon® PTFE: J | 7500 | 0.263 | Filled PTFE |
| Polyurethane: UHMW | 4000 | 0.140 | Ultra-high molecular weight |
| Nylon® 101 | 3000 | 0.105 | Trademark of DuPont Co. |
