Industrial seal self study guide - SKF.com

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With the seal removed, check for: • Rough bore surface. • Shaft cleanliness (is it clean and free of carbon?) • Coked lube on the shaft. • Shaft damage. • Flaws or voids in the bore. • Shaft corrosion. • Shaft discoloration. Identify the seal style and materials. Then inspect it for: • Primary lip wear. • Primary lip conditions. • Seal O.D. wear/damage. • Spring damage. Proper Seal Measurement Two of a seal’s measurements are its outer diameter (O.D.) and its inner diameter (I.D.). To determine these, follow these procedures: • To measure the O.D. of a seal, take three measurements equally spaced around the outside of the seal. The average of the three is the seal’s O.D (fig. 9b). • A metal O.D. seal is generally 0.005 to 0.016 inches (0. 13mm to 0.41mm) larger than the bore, for press fit. • A rubber O.D. seal is generally 0.008 to 0.020 inches (0.20mm to 0.51mm) larger than the bore, for proper compression and interference fit. The average of three measurements around the outside of the seal is the seal O.D. (fig. 9b). 9 • The inner diameter is more difficult to measure. Take about five I.D. readings, average them and add an interference figure to the lip I.D. to reach the approximate shaft I.D. (see Catalog 457010). • Alternatively, use the shaft O.D. as the seal I.D. Then refer to size listings in the SKF Handbook of Seals, for determining the correct seal part number. Common Sealing Problems Common sealing problems, their causes and solutions, are detailed below. Hammer Damage Some obvious signs of hammer damage include visible dents on the seal back, a distorted sealing element, or a garter spring that pops out (fig. 9c). Visible dents on the seal back are symptoms of hammer damage (fig. 9c). 79
Troubleshooting (cont...) Causes Such hammer damage can be caused by using a steel hammer on the seal housing during installation. B A Shaft-to-bore misalignments (left) and dynamic run-out (right) both cause early lip leakage (fig. 9d). STBM Misaligned components in a power train create Shaft to Bore Misalignment (STBM) and leaks. The seal lip will appear worn on one side and relatively untouched on the other. Shaft alignment should always be checked before installing a new seal (fig. 9e). DRO Dynamic Run Out (DRO) is the result of a bent, unbalanced or misaligned shaft. The sealing lip will be severely worn around the entire diameter. A dial indicator attached to the bore or housing while the shaft is rotated through 360˚ will reveal DRO. (fig. 9f). Corrective Actions Never hammer directly on the seal. Seals which are to be flush with the outside of the housing should be pressed in with an installation tool larger than the seal O.D. or with a block of wood. In this case it is acceptable to use a steel hammer, a dead blow hammer or soft-faced hammer on the wooden workpiece. When the blow is going through steel (such as a bearing ring), use a soft-faced or dead-blow hammer or mallet. This type of tool, like a block of wood, absorbs the shock wave created by the tool’s impact. A hammer blow without any material to absorb the shock wave can dislodge the garter spring from its proper operating position. Once the spring is out of position, the seal will fail. It may even interfere with the action of the seal lip, or find its way into the bearing. Shaft-to-Bore-Misalignment Dynamic Run-Out Early lip leakage, excessive (uneven) lip wear on one side of the seal, and/or excessive but consistent lip wear all around are symptoms of shaft-to-bore-misalignment or dynamic run-out. Causes Shaft-to-bore-misalignment (STBM) is a condition of excessive misalignment created by inaccurate machining, shaft bending, lack of shaft balance or worn bearings (fig. 9d and fig. 9e). Dynamic run-out (DRO) is a similar condition where the shaft does not rotate around its true center (fig. 9d and fig. 9f). If you find a leaking seal with a wide wear band on one side, but a narrow band on the other, you can suspect high STBM (unless O.D. markings indicated the seal was cocked). The lip area with the greatest wear indicates the direction of shaft misalignment. Initial leakage will generally occur in the area that shows little or no seal wear. This is because of inadequate lip contact. But as the worn side is hardened from excess pressure and heat, it may crack and cause additional leakage. Corrective Actions Check the shaft-to-bore alignment, and adjust it. Inspect the shaft and bore before installing the replacement seal. Replace worn bearings. 80
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Industrial seal self study guide Ma
Page 3 and 4:
CHAPTER 1— INTRODUCTION This book
Page 5 and 6:
INTRODUCTION (cont.) The Total Bear
Page 7 and 8:
BASIC SEAL TYPES (cont.) A As a sha
Page 9 and 10:
BASIC SEAL TYPES (cont.) As was ear
Page 11 and 12:
CHAPTER 2 REVIEW To take this test,
Page 13 and 14:
HM14 SKF’s non-spring loaded desi
Page 15 and 16:
SEAL DESIGN GROUPS (cont.) Hydrodyn
Page 17 and 18:
SEAL DESIGN GROUPS (cont.) CRWA5, C
Page 19 and 20:
SEAL DESIGN GROUPS (cont.) HDSB HDS
Page 21 and 22:
SEAL DESIGN GROUPS (cont.) All HS s
Page 23 and 24:
SEAL DESIGN GROUPS (cont.) HSF SBF
Page 25 and 26:
SEAL DESIGN GROUPS (cont.) VR2 VR2
Page 27 and 28:
SEAL DESIGN GROUPS (cont.) Scotseal
Page 29 and 30: SEAL DESIGN GROUPS (cont.) “OLD
Page 31 and 32: CHAPTER 3 REVIEW (cont.) 30 7. The
Page 33 and 34: V-Ring excludes contaminants, preve
Page 35 and 36: Seal Applications (cont.) An effect
Page 37 and 38: Seal Applications (cont.) Identific
Page 39 and 40: Seal Applications (cont.) Substitut
Page 41 and 42: Seal Applications (cont.) + Handles
Page 43 and 44: Seal Applications (cont.) °C °F 2
Page 45 and 46: Chapter 4 Review To take this test,
Page 47 and 48: Chapter 5—Seal Selection The firs
Page 49 and 50: Seal Selection (cont.) l A B Seal S
Page 51 and 52: Seal Selection (cont.) A longer lip
Page 53 and 54: Chapter 5 Review (cont.) 7. Substit
Page 55 and 56: Wear Sleeves (cont.) Speedi-Sleeve
Page 57 and 58: Wear Sleeves (cont.) 8. Drop the Sp
Page 61 and 62: fig. 7A Shaft surfaces must be smoo
Page 63 and 64: Shaft and Bore Conditions (cont.) S
Page 65 and 66: Shaft and Bore Conditions (cont.) B
Page 67 and 68: Chapter 7 Review (cont.) 6. Spiral
Page 69 and 70: Installation (cont.) For best resul
Page 71 and 72: Installation (cont.) 8. Check seal
Page 73 and 74: Installation (cont.) Corrective Act
Page 75 and 76: Installation (cont.) Split Seal Con
Page 79: Chapter 9—Troubleshooting Prelimi
Page 83 and 84: Troubleshooting (cont...) Out-of-Ro
Page 85 and 86: Troubleshooting (cont...) Pressure
Page 87 and 88: Chapter 9 Review (cont...) 8. Garte
Page 89 and 90: Glossary of Seal Terms (cont...) Di
Page 91 and 92: Glossary of Seal Terms (cont...) MP
Page 93 and 94: Glossary of Seal Terms (cont...) Sh
Page 95 and 96: Final Exam Congratulations. You hav
Page 97 and 98: 12. A cocked seal can cause a seal
Page 99 and 100: 26. In _________________ installati
Page 101 and 102: 40. A sealing lip that is cut, turn
Page 103 and 104: 54. If a shaft is lightly grooved b
Page 105 and 106: 73. More bearings fail from the ent
Page 107 and 108: 96. Ferrous and other commonly used
Page 109 and 110: Fold Here Fold Here PLACE STAMP HER
Page 111 and 112: 110 NOTES
Page 113 and 114: 112 NOTES
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Industrial seal self study guide - SKF.com

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