AA SPEC 371001 - Conveyor Pulleys and Shafts

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AA SPECIFICATION 371001

CONVEYOR PULLEYS AND SHAFTS ISSUE 0

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1 SCOPE 2

2 TECHNICAL REQUIREMENTS TO BE SPECIFIED BY THE PURCHASER 2

3 DEFINITIONS 2

4 REQUIREMENTS 3

4.1 DESIGN AND DIMENSIONS 3 4.2 HUBS AND END DISKS 5 4.3 SHAFT ATTACHMENTS 5 4.4 PULLEY SHELLS 6 4.5 SHAFTS 6 4.6 BEARINGS AND MOUNTINGS 8 4.7 SHELL CROWNING 9 4.8 WELDING 9 4.9 STRESS RELIEVING AND NORMALISING 10 4.10 LAGGING 10 4.11 BALANCING 12 4.12 CORROSION PROTECTION 12

5 QUALITY ASSURANCE PROVISION 12

6 TEST AND INSPECTION METHODS 12

6.1 NON DESTRUCTIVE TESTING 12

7 MARKING AND PACKING 12

7.1 MARKING 12 7.2 PACKING 12

APPENDIX A : RELATED DOCUMENTS 13

APPENDIX B : RECORD OF AMENDMENTS 13

APPENDIX C : BEARING CODING 14






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1 SCOPE

This specification details the requirements for the manufacture of belt conveyor pulleys and shafts. These pulleys are suitable for both general purpose textile reinforced belting and steel cord reinforced belting.

2 TECHNICAL REQUIREMENTS TO BE SPECIFIED BY THE PURCHASER

The following requirements shall be specified in tender invitation and in orders or contracts:

Title, reference number, issue and date of this specification.

Title(s) issue(s) and date(s) of applicable drawing(s).

Diameter, face length and hub bore of pulley and if pulley is crowned (see Clauses 4.1 and 4.6.1).

Type of lagging if required (see Clause 4.9).

The bearing code (see Appendix C)

Bearing centres of shafts. (see Clause 4.1)

Type of shaft attachment. (see Clause 4.2.1 and 4.2.2)

The name of the independent Quality Assurance Representative. (see AA STD 100)

3 DEFINITIONS

For the purpose of this specification the following definitions shall apply:

APPROVED : Approved by the Engineer in writing

BS : British Standard

DEFECTIVE : A pulley or shaft that fails to comply in one or more respects with the requirements of this specification

PURCHASER : The Company or store designated as the recipient of finished products or services

QUALITY ASSURANCE REPRESENTATIVE (QAR)

: An independent inspection agency appointed and approved by the Engineer

SANS : South African National Standards

STD : An AA Quality Assurance Procedure

The following terms are defined in the Conditions of Contract:

AA, Engineer, Company, Contractor.






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4 REQUIREMENTS

4.1 DESIGN AND DIMENSIONS

The design and dimensions of pulleys and shafts shall be in accordance with the requirements of Figure 1 and Table 1 below. In addition, when a pulley is not designed by finite element analysis the dimensions in Table 2 shall apply.

When a pulley is designed by finite element analysis the Engineer shall approve the analysis, pulley dimensions and manufacturing details. The minimum shell thickness in Table 2 shall apply. The stress range in weld toes shall not exceed the values for infinite life given in BS 7608 Fatigue Design and Assessment of Steel Structures.

4.1.1 Standard dimensions

Standard pulley dimensions are as follows:

Wide Bearing Centres

Note: Dimension A is to the inside of the chute liners.

Narrow Bearing Centres

To be used at all locations where chutes are not required.

Figure 1

Legend: D Pulley face to centre-line of bearing housing E Pulley face to belt edge G Pulley face to inside chute plate

Note: If the required shaft diameter exceeds the allowable shaft diameter then use wide bearing centres.

B or C B

A

G G

E EW

D DF

W

D D F






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4.1.2 Table 1 - Standard Pulley Dimensions

Belt width (mm)

Face width (mm)

Chute plates I/S

(mm)

Bearing centres (mm) Clearances for

wide centres. (mm) Wide Narrow

W F A B C

Max. allowable

shaft ø (mm)

D E G

450 550 650 1000 760 115 225 50 50 500 600 700 1050 810 115 225 50 50 600 700 800 1150 1020 140 225 50 50 750 900 1000 1350 1170 140 225 75 50 900 1050 1150 1550 1370 140 250 75 50

1050 1200 1300 1700 1520 140 250 75 50 1200 1350 1450 1850 1680 140 250 75 50 1350 1500 1600 2050 1830 140 275 75 50 1500 1700 1850 2300 1980 140 300 100 75 1650 1850 2000 2450 - - 300 100 75 1800 2000 2150 2600 - - 300 100 75 2100 2300 2450 2900 - - 300 100 75 2400 2600 2750 3200 - - 300 100 75

4.1.3 Table 2 - Standard Pulleys: Additional Information

Shaft Diameter at

locking element

Type of End disk

End disk inset

Minimum Shell Thickness

Min Hub Diameter

End Disk Thickness

At Hub At

Shell

50

Tur

bine

30 14 134 25 14

65 30 14 164 25 14

75 30 14 194 30 14

90 30 18 220 30 18

100 30 18 260 32 18

120 30 18 296 32 18

130 30 18 316 40 18

140 30 22 320 40 22

150 30 22 350 40 22

160 30 22 376 40 22

180 35 22 360 50 22






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200 35 25 420 50 25

220

T-B

otto

m

38 25 454 101 25

240 38 25 550 101 25

260 38 25 580 101 25

280 38 25 644 101 25

300 38 25 656 101 25

NOTE:

1. The minimum hub diameter is based on material with a yield stress of 0,2 = 280 MPa for turbine end disks and 0,2 = 270 MPa for T-bottom end disks.

2. The table is further based on Bikon 1006 (and equivalent) locking elements for turbine end disks and Bikon 1015 (and equivalent) locking elements for T-bottom end disks. Other locking devices may be submitted for consideration by the Engineer, in order to maintain best practice.

4.2 HUBS AND END DISKS

Hubs and end disks shall be manufactured from steel to SANS 1431 grade 300 WA, or 350 WA, or BS 970 Part 1 grade 070M20, or cast to BS 3100 grade A2. All hubs and end disks shall be tested prior to assembly in accordance with the method detailed in Clause 7.1. Cracks, inclusions, blow-holes and laminations shall be cause for rejection. Suppliers of cast hubs shall be approved. Note that cast hubs are to be considered only for pulleys with shafts greater than 200 mm.

4.3 SHAFT ATTACHMENTS

Pulley shaft-to-hub attachments shall be by means of keyless locking elements. The elements shall be so chosen as to be capable of transmitting the maximum torque that can be developed by the pulley shaft.

4.3.1 When a pulley is designed by finite element analysis the calculated bending moment applied to the locking element under start-up loads, and the angular distortion of the locking element under start-up loads, must not exceed the recommendations of the locking element suppliers.

4.3.2 Shrink fit shaft attachment:

While the preference is to use keyless locking elements as shaft attachments, when shrink fit shaft attachments are specified, shafts and bosses shall be machined to BS 4500 and shall be a shaft based interference fit. Note that shrink-fit attachments will require the approval of the Engineer.






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4.4 PULLEY SHELLS

4.4.1 Pulley shells shall be manufactured from steel that complies with the requirements of SANS 1431 grade 300 WA or 350 WA.

4.4.2 The shell shall be machined to be concentric with the shaft within the Total Indicated Run-out permitted in SANS 1669-1.

4.4.3 The tolerance on the pulley diameter shall be + 2,0 mm. This tolerance shall be applied to both bare and lagged pulleys.

4.4.4 For pulleys with face width suitable for belt widths up to and including 900 mm, the tolerance on the face width shall be ±3,0 mm. For pulleys with face width suitable for belt width greater than 900 mm, the tolerance on the face width shall be ±6,0 mm.

4.4.5 The shell shall have a minimum thickness after machining as indicated in Table 2. Deviation from the minimum shell thickness after machining shall not exceed 12% of the nominal thickness at any point on the shell.

4.4.6 The preferred shell diameters shall be limited to the range given in Table 3.

4.4.7 Other shell diameters may be submitted for consideration by the Engineer.

Table 3 - Standard pulleys: Shell Diameter

160 630 1250

200 710 1400

250 800 1600

315 900 1800

400 1000 2000

500 1120

4.5 SHAFTS

Table 4 - Preferred Bearing Journal Sizes

50 115 180 260

65 125 190 280

75 140 200 300

90 150 220

100 160 240






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4.5.1 Shafts shall be manufactured from steel that complies with the requirements of BS 970 Part 1 grade 070M20 (EN3A). Shafting of finished diameter less than 130 mm may be supplied as bright shafting. Shafting of finished diameter 130 mm and greater shall be normalised. Steel conforming to grade 080M40 (EN8) and 070M55 (EN9) is not to be used unless approved by the Engineer.

4.5.2 Shafts shall be sized so that at all points the stresses do not exceed 90% of the yield stress under start-up belt tensions and drive torques.

4.5.3 All contact surfaces for hub connections, bearings, seals and couplings shall be machined round to a surface texture not rougher than R0,8 m. Undercuts, reliefs and grooves are not permitted.

4.5.4 The bearing diameter shall be restricted to the range shown in Table 4. Where bearing journals are smaller in diameter than that at the locking element, the shoulder at the turn-

down shall be provided with a fillet, with a radius figured at 2

)(3 dDr

or

r = (0,1·d), whichever is the greater.

Here,

D = major (base) diameter

d = minor (journal) diameter

4.5.5 Where the bore of the coupling, shaft mounted reduction unit or holdback is smaller than the journal diameter of the shaft, the shoulder at the turn-down shall be provided with a fillet in accordance with 5.1.4 above.

4.5.6 When a pulley is not designed by finite element analysis the following rules shall be applied, with the shaft loaded by the shear forces applied by the end discs, but ignoring the moments applied by the discs:

The maximum allowable deflection of the shaft at the centre of the hub connection shall be designed at 14,5 milli-radians ( 0°-5’-0”), in accordance with the suppliers recommendations. These deflection limits are based on the locking element types noted in 4.1.3 Note 2 above. Limits for other locking devices may be submitted for consideration by the Engineer, in order to maintain best practice.

When the proposed design incorporates a reduction in shaft diameter, the stress factors shall be applied to ensure that the stresses at these points do not exceed 55 MPa. All external corners shall be chamfered to 3 mm at 45°.

4.5.7 When a pulley is designed by finite element analysis the following rules shall be applied:

The minimum shaft diameter shall be calculated using the CEMA formula using the running loads and torque. The bending moment on the locking element must also not exceed the manufacturer’s maximum allowable bending moment under start-up loads (see 4.3.1). This may require a different diameter. The maximum of these diameters shall be used, and rounded up to the next standard diameter in Table 2.






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When the design incorporates a reduction in shaft diameter the reduced diameter shall be determined by the CEMA shaft formula, with the shaft step down concentration factors taken into account. This diameter is to be rounded up to the next standard diameter in Table 4.

4.5.8 Flame spraying plating, welding, stray arcing and weld spatter on shafts is not permitted.

4.5.9 Keys and Keyways: keys and keyways shall comply with the requirements of BS 4235, Part 1.

4.5.10 When shrink-fit shaft attachments are used, the keys shall not protrude beyond the outer hub face. Keys and keyways for shaft extensions beyond the bearings shall be provided to suit the attachments required for the application. See paragraph 4.3.2

4.6 BEARINGS AND MOUNTINGS

4.6.1 Bearings shall comply with the boundary dimension requirements of ISO:R15 for radial bearings and shall be referenced by the Purchaser with the relevant AA code (Appendix C).

4.6.2 Bearings shall be of the double row, self-aligning, spherical roller type 222 series for shafts up to and including 140 mm diameter and the 231 series for shafts greater than 140 mm diameter. Bearings shall be designed for a life of 100 000 hours B10.

4.6.3 Lubrication shall be through a circumferential groove and three equally spaced holes in the outer race. The lubricant shall be grease type GPG-2LXEP in accordance with the requirements of AA standard specification 166014.

4.6.4 In all cases, the reference to bearing centres shall be construed as the centre of the bearing housing holding down bolts, where these differ from the actual centre-line of the bearing inside the housing. This normally applies to bearings in housings for shafts in excess of 140 mm. The pulley manufacturer shall therefore mount the bearings on the shafts in such a way that this requirement is satisfied.

4.6.5 Bearing housings: shall be of the horizontally split type in accordance with the requirements of BS 5646 Part 4. Adequate sealing arrangements shall be provided.

4.6.6 Lubrication shall be facilitated by type 21A button head grease nipples in accordance with the requirements of BS 1486 Part 2.

4.6.7 Bearing sole plates shall be in accordance with the requirements of AA standard drawing number Y1315.






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4.7 SHELL CROWNING

4.7.1 Crowning. (see Clause 2.3). If required, crowning shall be arranged either as

4.7.1.1 Edge-crowning, where the outer 1/6 of the pulley face width is tapered at a slope of 1:50, with the centre 2/3 flat. The dimension at the pulley centre shall be the nominal diameter of the pulley. The original material thickness of shell shall be sufficient to allow for machining to end thickness dimensions as specified in Table 2.

or

4.7.1.2 Centre-crowning, where the face of the pulley is tapered at a slope of 1 : 100 with the minor diameter at the ends of the pulley face. The dimension at the pulley edge shall be the nominal diameter of the pulley. The original material thickness of shell shall be sufficient to allow for machining to end thickness dimensions as specified in Table 2.

4.7.1.3 Crowning of pulleys for use with steelcord reinforced belting is generally not preferred.

See SANS 1669:1996

4.8 WELDING

4.8.1 Welding: All welds shall comply with the requirements of AWS D1.1.

4.8.2 Weld procedures shall be submitted for approval at time of tender.

4.8.3 Weld quality: Butt and fillet welds shall have complete penetration and fusion for the full length of the weld and shall be free from undercuts, overlaps or bead surface defects. Finished welds shall be free of cracks, porosity and inclusions.

4.8.4 Weld joint preparation. All weld joint preparation shall be available for inspection by the Quality Assurance Representative before welding is commenced. The weld preparation for butt welding may be modified within the limits AWS D1.1 in order to achieve full penetration welds. Such modification shall be submitted for approval.

4.8.5 Shell butt weld method: The pulley shell butt joint shall be internally welded and shall be dressed to a smooth profile inside and outside the shell.

4.8.6 Air vent

A 4 mm diameter air vent hole shall be provided for pulleys having either shrink fit or keyless locking element shaft attachments in order to prevent 'blow-back' on final seal run and distortion on vulcanising of lagging (if used). The hole shall be located outside of the heat affected zone of the disk-to shell weld.

This hole shall be sealed with a 4 mm diameter parallel dowel pin to DIN 6325 of a length not less than the diaphragm thickness.






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4.9 STRESS RELIEVING AND NORMALISING

NOTE

1. Details of heat treatment furnaces and recording devices shall be submitted for approval.

2. The furnace atmosphere shall be so controlled as to avoid oxidation during the heating and soaking periods. There shall be no direct flame on the treated article.

4.9.1 Stress relieving of pulleys shall be at a temperature of 600/650°C and the heating and cooling cycles shall be as specified in Clauses 4.8.3 and 4.8.4.

4.9.2 Normalising of shafts shall be at a temperature of 880/910°C and the heating and cooling cycles shall be as specified in Clauses 4.8.3 and 4.8.5.

4.9.3 Heating cycle: The temperature of the furnace at the commencement of the treatment cycle shall not exceed 400°C and the rate of increase in temperature above 400°C shall not exceed the following:

4.9.3.1 Not more than 200°C per hour for a thickness of diaphragm plate up to and including 25 mm.

4.9.3.2 Not more than t

5000 °C/ hour for a diaphragm plate over 25 mm in thickness where

t is the diaphragm thickness in mm.

4.9.3.3 When the item has attained a uniform temperature the temperature shall be maintained for a period of one hour for diaphragm thicknesses up to and including 25 mm. For diaphragms over 25 mm thick allow an additional 2 minutes for each mm in thickness above 25 mm.

4.9.4 Cooling cycle, stress relieving: The component shall be cooled in the furnace at a rate not exceeding 250°C per hour for thicknesses of diaphragm plate up to and including 25 mm.

4.9.4.1 For diaphragm plate thicknesses above 25 mm the cooling rate shall not exceed

t

6250 °C /hour where t is the diaphragm thickness in mm.

4.9.4.2 Components shall be removed from the furnace at a temperature of 250°C and cooled in still air.

4.9.5 Cooling cycle, normalising: Shafts shall be cooled in still air from the maximum temperature required in this specification.

4.10 LAGGING

See also SANS 1669-2: 2005






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4.10.1 Lagging type and pattern

The lagging pattern shall be one of the following as specified by the Purchaser.

(a) Plain Non drive bend pulleys.

(b) Chevron Direction of drive to be advised to the Contractor. Note this pattern is not preferred.

(c) Diamond. This pattern may be used on driver pulleys and non-drive pulleys where the contact angle exceeds ±150°

(d) Ceramic tiles both drive and non-drive. note that dimpled tiles are required for drive pulleys.

4.10.2 Lagging material

The lagging material shall be one of the following as specified by the Purchaser.

(a) Natural rubber having a Shore A hardness of 65° - 70° for non flame-retardant applications.

(b) Neoprene having a Shore A hardness of 65° + 5° for flame-retardant applications.

The material shall comply with the requirements of AA specification 171001.

Other lagging materials, such as ceramic tiles, may be submitted for consideration by the Engineer, in order to maintain best practice.

4.10.3 Lagging Thickness

The lagging thickness shall be as specified by the Purchaser and shall be not less than 10mm in the case of chevron or diamond profiled lagging.

4.10.4 Surface Preparation

The surfaces to be lagged shall be abrasive blast cleaned to SA 2½ finish with a surface profile of 40 to 65 microns in accordance with requirements of AA specification 164050.

4.10.5 Curing

Lagging shall be steam cured in an autoclave in accordance with the requirements of SANS 1198.

Where the lagging is applied on site, the adhesive curing times as specified by the suppliers shall be applied.






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4.10.6 Adhesion

An adhesion test shall be conducted on every batch of lagging material in accordance with the requirements of SANS 1198 and SANS 1669t 2. Adhesive used shall be from the same batch as used for the lagging process.

4.11 BALANCING

All pulleys shall be balanced in accordance with SANS 1169.

Note: Welding of fitments to the end disks for balancing purposes is not permitted.

4.12 CORROSION PROTECTION

Prior to painting, all rust, mill scale, grease, oil and other foreign matter shall be removed. The shell, when not lagged, the hubs and end disks and diaphragms shall be primed with one coat of single pack wash primer of not less than 20 m thickness and a single coat of chlorinated rubber, resin based paint of not less than 30 m thickness.

5 QUALITY ASSURANCE PROVISION

The quality management system shall comply with the requirements of SABS ISO 9001.

The requirements of AA STD 100 shall apply.

6 TEST AND INSPECTION METHODS

6.1 NON DESTRUCTIVE TESTING

The hubs and end disks, shell, and shaft shall be non-destructively (U/S and MPI) tested in accordance with the requirements of AA specification 999001 before assembly. Welded regions shall be re-tested after welding.

7 MARKING AND PACKING

7.1 MARKING

The following data shall be clearly and permanently marked on both vertical faces of the shaft and on one end of the shell rim. No marking shall extend into a welded zone.

Contractor's name, trade name or trade mark.

Month and year of manufacture.

QAR's logo.

AA order number.

7.2 PACKING

Immediately after acceptance by the QAR, all exposed shaft surfaces shall be protected against corrosion and accidental damage. Precautions shall be taken by the Contractor to ensure that the pulley assemblies are not damaged during handling and transportation.






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APPENDIX A : RELATED DOCUMENTS

AAC Drawing Y1315 : Standard sole plates for conveyors (dimensions)

AA Specification 164/50 : Corrosion protection of steelwork with coatings

AA Specification 171/1 : Fire resistant elastomers for use underground in fiery mines

AA Specification 999/1 : Non-destructive examination for flat steel components

AA STD 100 : Quality management systems for critical and major material

BS 970 Part 1 : Wrought steels for mechanical and allied engineering purposes.

BS 3100 : Specification for steel castings for general engineering purposes

BS 1486 Part 2 : Heavy duty lubricating nipples

BS 4235 : Metric keys and keyways

BS 4500 : ISO limits and fits

AWS/ANSI D1.1-2006 : Structural welding code - Steel

BS 5646 Part 4 : Specification for plummer block housings

DIN 6325 : Parallel pins, hardened, tolerance zone M6

SANS 1173 : General purpose textile reinforced conveyor belting

SANS 1431 : Weldable structural steel

SANS 1198 : The production and quality of rubber linings on steel pipes, pipe fittings and vessels

SANS 1669 parts 1&2 : Conveyor Belt Pulleys

APPENDIX B : RECORD OF AMENDMENTS

Issue 0 : Based upon AAC Specification 371001 (Issue 10)






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APPENDIX C : BEARING CODING

Bearings listed on AA equipment schedules shall be coded as follows:

xxx C/T L/F (S)

Where: xxx is numeric and is the shaft diameter in mm.

C/T is either C or T and indicates whether the housing is a closed end or through shaft.

L/F is either L or F and indicates whether the bearing is located or floating.

(S) is either present or absent and indicates whether or not a flinger ring is required.

Example

Code 90TL indicates a bearing unit to suit a shaft of 90 mm diameter with the shaft through the bearing and the bearing located in the housing. No flinger is required.

The locating bearing is placed at the coupling side of a through shaft, with the non-driving end floating. Where the shaft has a double extension for a second drive, the locating bearing is placed to best suit the arrangement. For a shaft with a double extension for a holdback device, the locating bearing is placed at the coupling.

Pulley shaft extensions

For the range of bearings permitted by this specification, the values recommended for the extension of the pulley shaft through the bearings of housings with closed ends are as shown in Table 5.

The dimensions shown are given from the centreline of the housing which may differ from that of the bearing. The centreline dimension indicated on the drawing generally is that of the housing or bolt hole centres.

TABLE 5

Shaft dia

Bearing code

Ext Shaft dia

Bearing code

Ext

2 50 CL or F 34 150 150 CL or F 70

65 65 CL or F 42 160 160 CL or F 72

75 75 CL or F 50 180 180 CL or F 88

90 90 CL or F 55 200 200 CL or F 92

100 100 CL or F 60 220 220 CL or F 100

115 115 CL or F 68 240 240 CL or F 108

125 125 CL or F 72 260 260 CL or F 108

140 140 CL or F 85 300 300 CL or F 130

Documents

AA SPEC 371001 - Conveyor Pulleys and Shafts