m13 - materials handling - rev02

Project Standards:

MATERIALS HANDLING AND CONVEYOR BELTING

M13

CONFIDENTIAL Any information contained herein is to be treated as confidential and may not be divulged to any other

party without the prior written approval of Bosch Projects (Pty) Ltd. Page 2

1. CANE SUGAR MATERIALS HANDLING: DESIGN CHARACTERISTICS For materials handling involving sugar products and by- products, density, temperature and combustive design factors shall be taken into account. Conveyor belting and conveyors shall be designed as per CEMA or ISO guidelines. Components shall be manufactured or selected according to relevant ISO dimensional standards. Materials handling equipment sizing or design shall be supplied, and where computer programmes are used to do standard types of calculation, a printout shall be supplied which includes all parameters used in the programme. Care shall be taken to design the materials handling equipment with minimum and maximum product data used where appropriate. I.e. Higher density figure to be used when calculating power requirements.

1.1 Densities

Data concerning average bulk densities varies widely according to the source, degree of preparation, moisture / juice percentage as well as cane quality, therefore the Contractor shall ensure that data used is applicable to the factory in question.

1.2 Temperature

Where high temperatures (> 60 C), such as megasse, bagasse and furfyl residue are expected, cover thickness and carcass tension rating shall be incorporated in the design.

1.3 Spontaneous Combustion

All rubber skirting shall be flame retardant, as per SABS 971.

Product Density range (kg/m)

Average density (kg/m)

Sugar Raw/VHP 850 950 900 Sugar Refined White 800-900 850 Final bagasse 120 - 180 140 Diffuser bagasse 280 - 380 300 Bagasse 200 400 250 Shredded Cane 300 700 400 Knifed Cane 230 480 320 Whole Cane stalks Tangled 160 200 180 Whole Cane stalks Bundled 130 180 150



2. RECOMMENDED CONVEYOR TYPES

The conveyor / carrier types can be determined by the duty of the material to be handled, and are summarised as follows:

Product Recommended Type

Whole cane Heavy duty belt

Knifed cane Belt

Shredded cane Belt or chain and slat

Mill inter carrier Chain and slat, stainless pins & bushes

Diffuser feed & megasse Chain and slat, stainless side plates, pins & bushes Bagasse conveying normal Belt

Bagasse over boiler feeders Chain and slat

Filter cake Belt

Sugar from centrifugals Screw, belt or grasshopper

Wet sugar into drier Screw

Dry sugar Screw or belt

The Contractor shall design the conveyor / carrier according to the product as above, and shall submit all calculations to the Engineer as stated above.

3. DESIGN CONVEYOR SPEEDS

Speed (m/s) Conveyor Type

0.5 Cane carrier

1.5 Knifed cane belt

1.5 Shredded cane belt

0.8 Shredded cane slat conveyor

0.8 Mill intercarrier

0.8 Diffuser feed slat conveyor

0.8 Diffuser megasse carrier

1.5 Bagasse belt conveyor

0.65 Bagasse slat conveyor

1.5 Sugar Raw and Refined



4. DESIGN FACTORS

4.1 Safety Factors for Drives

A run back device shall be fitted to any conveyor or carrier gearbox where it is installed at an inclination, so that the conveyor will not run backwards and discharge the conveyed product when fully stopped. The gearbox can be ordered with a hold-back, or retro-fitted to prevent this safety hazardous occurrence.

4.2 Service Factors for Drives

The required power calculated from standard conveyor design formulae shall be increased by a factor of 1,2 for belt conveyors and 1,5 for chain conveyors. In addition, if the motor is to be driven from a variable frequency controller, the motor size and gearbox ratio shall be chosen so that motor cooling is still effective at the slowest running speeds of the conveyor. The suggested operating speed range for such a motor is 35 to 80 Hz. This is in order to provide adequate cooling at the slower motor speeds.

5. CHAIN SLAT CONVEYORS 5.1 Chain shall be carefully selected for high strength and with a minimum factor

of safety 1,5 times that recommended by conveyor design handbooks.

5.2 Corrosion resistant stainless steel load bearing components shall be considered on conveyor chains from the main cane carrier to the final mill for longevity.

5.3 Chain and component type shall match the conveyor duty. The recommend chain type for cane, megasse and bagasse can be cranked- link rollerless chain, block link chain or Y block chain. The block links shal l be fitted with replaceable bushes, have a m i n i m u m pitch of 152.4mm, and minimum breaking load of 60000 kg.

5.4 5.5 Chain slats may be attached by means of slots in the block links, thus

avoiding welding on the chain links or side plates.

5.6 For lighter duties, roller chain of 152,4mm pitch, with appropriate attachments, with a breaking load of 45000 kg minimum, may be used. In this case the rollers shall be at least 70mm diameter.

5.7 Comprehensive quality assurance and control shall be applied to every stage of chain manufacture, and records and test certificates shall be supplied for all materials and manufacturing processes, including heat treatment. An independent inspection authority shall be appointed to ensure that these quality requirements are followed.



5.8 The slats shall be arranged to slide on adequate wear strips on the deck of the carrier on the conveying run, and on two rails on the return run. In this way the chains do not carry the weight of the slats.

5.9 Adequate length adjustment shall be provided, and also a sufficiently long catenary immediately after the drive sprockets, to ensure natural tensioning.

5.10 Slats for cane, and diffuser conveyors shall be fabricated from carbon steel and approved by the Engineer. In these applications, the use of rake type slats may be preferred.

5.11 Slats for mi l l inter-carriers shall be of hardwood, settl sections, or extruded aluminium sections.

5.12 In the case of mill intercarriers, typical elevations are between 40 and 60. Bagasse shall be conveyed onto the lower deck of the carrier.

5.13 Intercarrier speeds shall, where possible, be limited to between 0.8m/s and 1m/s for reasonable life.

5.14 Overall interacrrier dimensions shall be designed such that sufficient cross section is available to convey bagasse at a usable volume of 60%. Ie, 40% free space.

5.15 Slats for bagasse carriers are preferably made from well-seasoned hard wood.

5.16 Fabricated aluminium slats have been found to be satisfactory in both applications, and economical, even though they are more expensive.

5.17 Slat pitch shall be as close as possible without causing bridging and is usually between six and eight chain pitches.

5.18 Conveyor decks shall be made from 3CR12 for resistance to wear which i s usua l l y a gg ra va te d by co r ros ion .

5.19 Chain conveyor sprockets shall be as large as possible, preferably having a minimum number of teeth of 13 for conventional chain or 7 for block link chain.

5.20 The sprockets shall be made from plate, and may be accurately flame-cut. They shall be in two halves, and securely bolted to hubs, which are keyed to the shafts.

5.21 If Locking Elements are fitted to hubs in place of keys, then the locking element design torque for one hub shall be able to transfer the full torque of the stalled motor. This is required to cater for the scenario of one chain strand breaking, and the conveyor stalling with broken slats etc., and thus the full torque being transferred through one hub. This criterion shall also be borne in mind when sizing the chain. It is also prudent to not over design motors, since this will exacerbate the required design size of the chain and hub locking elements, and increase costs unnecessarily.



5.22 Adequate deflectors shall be provided at all feed points and immediately ahead of the drive sprockets, to avoid material being fed onto the chain.

5.23 The bottom deck shall be approximately 150mm lower than the straight in-line height, so that the chain is lifted from the deck to the sprocket tangent level. This ensures a smooth transition from the deck to the sprocket and vice versa.

6. BAGASSE CHAIN SLAT CONVEYORS

Where bagasse conveyors are implemented to feed boiler chutes, the following shall apply:

6.1 Each boiler feed chute shall be staggered sufficiently across the width of the carrier.

6.2 The conveyor shall be designed such that the bagasse falls about 100mm before reaching the mouth of the chute via a generous lead in ramp.

6.3 Recommended boiler feed chain- slat conveyor design feature are a speed of less than 0.8m/s, the conveyor sliding on slats as opposed to chains, and slat pitch as close as possible without risking bridging between slats.

6.4 Care should be taken where elevations lower than 23 are considered for this conveyor type.

7. BELT CONVEYORS

7.1 All belt conveyors to have high temperature resistant top cover (preferably neoprene) in order to withstand bagasse temperatures of up to 70.

7.2 Troughing idlers shall be 35 normal, and 20 in loading areas.

7.3 Idler spacing shall be according to belt size and material, 1 to 2m (usually 1,2m), and closer at loading points.

7.4 Impact idler spacing to be 0,5 m, and heavy duty, shock-absorbing idlers for cane carriers where cane discharging from a feeder table occurs.

7.5 Return idler spacing shall be 2 to 3m.

7.6 Where material is of a sticky nature, e.g. shredded cane, non-clogging idlers carrying and return shall be used.

7.7 When required, belt training idlers, both carrying and return, shall be positioned 8 to 15m ahead of each pulley and at intermediate points 30m or less apart, with a minimum of one per conveyor.

7.8 To ensure belt alignment, the head pulley shall be crowned.



7.9 Where required by design, the angle of wrap shall be increased with a snub pulley, and/or the head pulley shall be lagged.

7.10 Belt cleaning scrapers of an approved type on inside and outside of the belt and on the tail pulley, shall be included as standard.

7.11 Skirting s e a l i n g a r r a n g e m e n t s s h a l l b e c a r e f u l l y d e s i g n e d a n d constructed. If a rubber seal is used, it shall be made from soft rubber sheeting, and conveyor belting shall not be used.

7.12 Safety guards shall be fitted to the conveyor to prevent any snagging of limbs a t the head and ta i l pu l leys . These shall meet applicable safety standards.

7.13 Pull ropes for emergency stop shall be fitted to both sides of all conveyors.

7.14 Stainless steel or 3CR12 beater plates shall be provided under belt where cutting occurs over the belt, to reduce damage by dislodged knives or tramp iron.

7.15 Adequate adjustment shall be provided at the tail pulley to maintain belt tension. Alternatively, an appropriate belt tensioning device which maintains correct tension and alignment under all operating conditions shall be provided. If space permits, the preferred type is the vertical counter-weighted pulley enclosed in a safety frame to prevent unauthorised access.

8. BELT SPECIFICATION

The following table shall be used as a guideline for the belt specification per product. Food quality belts shall be used where appropriate:

Product Belt Spec Whole stick/ prepared cane, ash, VHP sugar Plylon EP Polyester Nylon grade N covers Megasse, bagasse, furfyl residue Plylon EP Polyester Nylon style 6740 A

covers Combustible bagasse, residue, coal, bagacillo Plylon EP Polyester Nylon style 6075 Food quality products Raw and Refined Sugar PVC Type 300/3 Refined / Raw sugar in bucket elevator PVC Class 800

Maximum recommended belt speeds when conveying bagasse per belt width are as follows:

Belt width mm Maximum Speed m/s Recommended Speed m/s

500 - 600 3.0 1.2 750 - 900 3.7 1.5

1000 - 1500 4.2 1.7



9. SPLICE SPECIFICATION Vulcanised splice specifications:

9.1 Hot vulcanised splice applicable to belts conveying materials above 70C.

9.2 Cold vulcanised splice applicable to belts conveying materials below 70C.

10. SCREW CONVEYORS

Generally, a sugar screw shall meet the following requirements:

10.1 It is of primary importance that the bearings, casing and screw are accurately aligned, particularly when there are three or more bearings on the conveyor. Misalignment causes shaft breakages, excessive wear and unnecessary noise.

10.2 Care must be taken that the shafting is manufactured to a maximum eccentric run out of no more than 0,5mm and that of the helical flights within 1 to 2 mm.

10.3 This can be ensured by machining of the stub-end shafts and landings true to each other only after all welding and fabrication is complete. Under no circumstances will conveyors with shafts out of true be accepted by the engineer.

10.4 The designspeed shall not exceed the manufacturers recommendation, which is typical ly, 40rpm for a 600mm diameter screw.

10.5 The normal screw pitch is 1,0 times the screw diameter.

10.6 The design load factor for raw sugar shall be 25% and for refined sugar 30%.These factors shall be reduced for inclined conveyors and approved by the Engineer.

10.7 The inclination angle shall not exceed 30 for a conventional screw conveyor. If a steeper angle is required, a fully enclosed screw running in a cylindrical casing shall be used.

10.8 The shaft shall be made from heavy carbon steel tubing (e.g. ASTM A106 Grade B, Schedule 80).

10.9 For screw diameters of 450mm and greater, the shaft shall be designed with sufficient rigidity so that no hanger bearing or coupling is required for a length up to approximately 5m.

10.10 Where this length is exceeded and/or couplings and hanger bearings are requ i red , they shall be approved by the Engineer. The coupling shall consist of a shaft fitted into the ends of the tubular screw shaft, which is bored accurately to fit the shaft. The shaft is fixed into the tube using two fitted bolts at right angles to each other, at each end of the shaft.



10.11 Hanger bearings shall be furnished preferably with Diva metal bushes,

(obtainable from Federal Mogul) and adjustable for good alignment. It i s recommended that the shaft be fitted with a disposable sleeve shrunk onto it, for the bearing journal.

10.12 External bearings shall be provided at head and tail, housed in foot mounted plummer blocks on heavy right angle brackets on the end- plates. An opening must be provided between the seal on the endplate and the bearing in order to allow for the escape of any leaked material. The drive end bearing shall be arranged to take axial thrust. The friction grip of a tapered sleeve in the bearing is not suitable.

10.13 End seals shall be accessible from outside the conveyor housing, and shall be split so that they can be replaced without removing the bearing.

10.14 The trough shall be made of 3CR12 with external carbon steel stiffeners, flanges and fittings.

10.15 The flights shall be made of 3CR12.

10.16 Full flights shall be used for normal conveying duties. Where mixing, or load distribution is required, ribbon flights may be considered. The load factor shall then be appropriately reduced.

10.17 Where choking of the conveyor is likely, such as at the discharge from a large batch centrifugal, variable pitch may be preferred. In this case the pitch variation shall be determined by the load rating of the screw.

10.18 The casing sections must be set up in line before the flanges are welded to the casing, in order to ensure that the trough is perfectly straight on final assembly.

10.19 During assembly, the bearings must be accurately lined up using appropriate equipment.

10.20 The screw conveyor must be supplied with adequate covers and inspection hatches, arranged to prevent any access to the inside while the conveyor is running. If removable covers are provided, they shall be interlocked with the drive motor to prevent the conveyor from being started if the cover is open.

11. APRON INTERCARRIER

Where a close configuration of three roller mills occurs, apron intercarriers may be used where there is no enclosed feed chute to the mills. Typically implemented for relatively light duty applications.

11.1 The conveyor slats around the headshaft may act as a fourth or feeder mill.



11.2 Where this is the case, additional support shall be given to the slats around the head pulley, comprising metal ringed discs positioned between the head shaft sprockets.

11.3 Head shaft sprockets shall typically have pitch circle diameters of 600 800mm, depending on the mill configuration.

11.4 Tail shaft sprockets shall have a pitch circle diameter of greater than 500mm to prevent undue chain wear.

11.5 The speed of the carrier shall typically be set to about 10 15% above the maximum surface speed of the following mill speed.

11.6 Apron carriers should not be inclined at an angle of more than 25.

12. AIR CUSHION BELT CONVEYORS Where appropriate, air cushion belt conveyors may be considered. These have several advantages over the conventional type.

13. BELT WEIGHERS

All belt weighers shall have an accuracy of 97.5% or better.

1. Cane Sugar Materials Handling: Design Characteristics1.1 Densities1.2 Temperature1.3 Spontaneous Combustion

2. Recommended Conveyor Types3. Design Conveyor Speeds4. Design Factors4.1 Safety Factors for Drives4.2 Service Factors for Drives

5. Chain Slat Conveyors5.1 Chain shall be carefully selected for high strength and with a minimum factor of safety 1,5 times that recommended by conveyor design handbooks.5.2 Corrosion resistant stainless steel load bearing components shall be considered on conveyor chains from the main cane carrier to the final mill for longevity.5.3 Chain and component type shall match the conveyor duty. The recommend chain type for cane, megasse and bagasse can be cranked- link rollerless chain, block link chain or Y block chain. The block links shall be fitted with replaceable bushes, have ...5.45.5 Chain slats may be attached by means of slots in the block links, thus avoiding welding on the chain links or side plates.5.6 For lighter duties, roller chain of 152,4mm pitch, with appropriate attachments, with a breaking load of 45000 kg minimum, may be used. In this case the rollers shall be at least 70mm diameter.5.7 Comprehensive quality assurance and control shall be applied to every stage of chain manufacture, and records and test certificates shall be supplied for all materials and manufacturing processes, including heat treatment. An independent inspectio...5.8 The slats shall be arranged to slide on adequate wear strips on the deck of the carrier on the conveying run, and on two rails on the return run. In this way the chains do not carry the weight of the slats.5.9 Adequate length adjustment shall be provided, and also a sufficiently long catenary immediately after the drive sprockets, to ensure natural tensioning.5.10 Slats for cane, and diffuser conveyors shall be fabricated from carbon steel and approved by the Engineer. In these applications, the use of rake type slats may be preferred.5.11 Slats for mill inter-carriers shall be of hardwood, settl sections, or extruded aluminium sections.5.12 In the case of mill intercarriers, typical elevations are between 40 and 60 . Bagasse shall be conveyed onto the lower deck of the carrier.5.13 Intercarrier speeds shall, where possible, be limited to between 0.8m/s and 1m/s for reasonable life.5.14 Overall interacrrier dimensions shall be designed such that sufficient cross section is available to convey bagasse at a usable volume of 60%. Ie, 40% free space.5.15 Slats for bagasse carriers are preferably made from well-seasoned hard wood.5.16 Fabricated aluminium slats have been found to be satisfactory in both applications, and economical, even though they are more expensive.5.17 Slat pitch shall be as close as possible without causing bridging and is usually between six and eight chain pitches.5.18 Conveyor decks shall be made from 3CR12 for resistance to wear which is usually aggravated by corrosion.5.19 Chain conveyor sprockets shall be as large as possible, preferably having a minimum number of teeth of 13 for conventional chain or 7 for block link chain.5.20 The sprockets shall be made from plate, and may be accurately flame-cut. They shall be in two halves, and securely bolted to hubs, which are keyed to the shafts.5.21 If Locking Elements are fitted to hubs in place of keys, then the locking element design torque for one hub shall be able to transfer the full torque of the stalled motor. This is required to cater for the scenario of one chain strand breaking, ...5.22 Adequate deflectors shall be provided at all feed points and immediately ahead of the drive sprockets, to avoid material being fed onto the chain.5.23 The bottom deck shall be approximately 150mm lower than the straight in-line height, so that the chain is lifted from the deck to the sprocket tangent level. This ensures a smooth transition from the deck to the sprocket and vice versa.

6. Bagasse Chain Slat Conveyors6.1 Each boiler feed chute shall be staggered sufficiently across the width of the carrier.6.2 The conveyor shall be designed such that the bagasse falls about 100mm before reaching the mouth of the chute via a generous lead in ramp.6.3 Recommended boiler feed chain- slat conveyor design feature are a speed of less than 0.8m/s, the conveyor sliding on slats as opposed to chains, and slat pitch as close as possible without risking bridging between slats.6.4 Care should be taken where elevations lower than 23 are considered for this conveyor type.

7. Belt Conveyors7.1 All belt conveyors to have high temperature resistant top cover (preferably neoprene) in order to withstand bagasse temperatures of up to 70 .7.2 Troughing idlers shall be 35 normal, and 20 in loading areas.7.3 Idler spacing shall be according to belt size and material, 1 to 2m (usually 1,2m), and closer at loading points.7.4 Impact idler spacing to be 0,5 m, and heavy duty, shock-absorbing idlers for cane carriers where cane discharging from a feeder table occurs.7.5 Return idler spacing shall be 2 to 3m.7.6 Where material is of a sticky nature, e.g. shredded cane, non-clogging idlers carrying and return shall be used.7.7 When required, belt training idlers, both carrying and return, shall be positioned 8 to 15m ahead of each pulley and at intermediate points 30m or less apart, with a minimum of one per conveyor.7.8 To ensure belt alignment, the head pulley shall be crowned.7.9 Where required by design, the angle of wrap shall be increased with a snub pulley, and/or the head pulley shall be lagged.7.10 Belt cleaning scrapers of an approved type on inside and outside of the belt and on the tail pulley, shall be included as standard.7.11 Skirting sealing arrangements shall be carefully designed and constructed. If a rubber seal is used, it shall be made from soft rubber sheeting, and conveyor belting shall not be used.7.12 Safety guards shall be fitted to the conveyor to prevent any snagging of limbs at the head and tail pulleys. These shall meet applicable safety standards.7.13 Pull ropes for emergency stop shall be fitted to both sides of all conveyors.7.14 Stainless steel or 3CR12 beater plates shall be provided under belt where cutting occurs over the belt, to reduce damage by dislodged knives or tramp iron.7.15 Adequate adjustment shall be provided at the tail pulley to maintain belt tension. Alternatively, an appropriate belt tensioning device which maintains correct tension and alignment under all operating conditions shall be provided. If space perm...

8. Belt Specification9. Splice Specification9.1 Hot vulcanised splice applicable to belts conveying materials above 70 C.9.2 Cold vulcanised splice applicable to belts conveying materials below 70 C.

10. Screw Conveyors10.1 It is of primary importance that the bearings, casing and screw are accurately aligned, particularly when there are three or more bearings on the conveyor. Misalignment causes shaft breakages, excessive wear and unnecessary noise.10.2 Care must be taken that the shafting is manufactured to a maximum eccentric run out of no more than 0,5mm and that of the helical flights within 1 to 2 mm.10.3 This can be ensured by machining of the stub-end shafts and landings true to each other only after all welding and fabrication is complete. Under no circumstances will conveyors with shafts out of true be accepted by the engineer.10.4 The designspeed shall not exceed the manufacturers recommendation, which is typically, 40rpm for a 600mm diameter screw.10.5 The normal screw pitch is 1,0 times the screw diameter.10.6 The design load factor for raw sugar shall be 25% and for refined sugar 30%.These factors shall be reduced for inclined conveyors and approved by the Engineer.10.7 The inclination angle shall not exceed 30 for a conventional screw conveyor. If a steeper angle is required, a fully enclosed screw running in a cylindrical casing shall be used.10.8 The shaft shall be made from heavy carbon steel tubing (e.g. ASTM A106 Grade B, Schedule 80).10.9 For screw diameters of 450mm and greater, the shaft shall be designed with sufficient rigidity so that no hanger bearing or coupling is required for a length up to approximately 5m.10.10 Where this length is exceeded and/or couplings and hanger bearings are required, they shall be approved by the Engineer. The coupling shall consist of a shaft fitted into the ends of the tubular screw shaft, which is bored accurately to fit...10.11 Hanger bearings shall be furnished preferably with Diva metal bushes, (obtainable from Federal Mogul) and adjustable for good alignment. It is recommended that the shaft be fitted with a disposable sleeve shrunk onto it, for th...10.12 External bearings shall be provided at head and tail, housed in foot mounted plummer blocks on heavy right angle brackets on the end- plates. An opening must be provided between the seal on the endplate and the bearing in order to allow for the ...10.13 End seals shall be accessible from outside the conveyor housing, and shall be split so that they can be replaced without removing the bearing.10.14 The trough shall be made of 3CR12 with external carbon steel stiffeners, flanges and fittings.10.15 The flights shall be made of 3CR12.10.16 Full flights shall be used for normal conveying duties. Where mixing, or load distribution is required, ribbon flights may be considered. The load factor shall then be appropriately reduced.10.17 Where choking of the conveyor is likely, such as at the discharge from a large batch centrifugal, variable pitch may be preferred. In this case the pitch variation shall be determined by the load rating of the screw.10.18 The casing sections must be set up in line before the flanges are welded to the casing, in order to ensure that the trough is perfectly straight on final assembly.10.19 During assembly, the bearings must be accurately lined up using appropriate equipment.10.20 The screw conveyor must be supplied with adequate covers and inspection hatches, arranged to prevent any access to the inside while the conveyor is running. If removable covers are provided, they shall be interlocked with the drive motor to pre...

11. Apron Intercarrier11.1 The conveyor slats around the headshaft may act as a fourth or feeder mill.11.2 Where this is the case, additional support shall be given to the slats around the head pulley, comprising metal ringed discs positioned between the head shaft sprockets.11.3 Head shaft sprockets shall typically have pitch circle diameters of 600 800mm, depending on the mill configuration.11.4 Tail shaft sprockets shall have a pitch circle diameter of greater than 500mm to prevent undue chain wear.11.5 The speed of the carrier shall typically be set to about 10 15% above the maximum surface speed of the following mill speed.11.6 Apron carriers should not be inclined at an angle of more than 25 .

12. Air Cushion Belt Conveyors13. Belt Weighers

m13 - materials handling - rev02

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