Accuweigh Installation Manual Rev.10.1.pdf

7/28/2019 Accuweigh Installation Manual Rev.10.1.pdf

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MANUAL -

ACCUWEIGH

WEIGH FRAMES



ACCUWEIGH - WEIGHFRAME

MANUAL

TABLE OF CONTENTS

DESCRIPTION PAGE

SECTION 1 GENERAL SYSTEM DESCRIPTION 4

A. INTRODUCTION 4

B. GENERAL SYSTEM DESCRIPTION 4

SECTION 2 APPLICATION GUIDELINES 5

A. INTRODUCTION 5

B. APPLICATION GUIDELINES 5

SECTION 3 INSTALLATION INSTRUCTIONS 20

A. WEIGH FRAME WITH OPTIONAL SPEED SENSOR ASSEMBLY

20

B. SPEED SENSOR (WITHOUT OPTIONAL SPEED SENSOR

ASSEMBLY 25

C. (OPTIONAL) MANUALLY OPERATED TEST WEIGHT

MECHANISM 26

D. (OPTIONAL) ELECTRICALLY OPERATED TEST WEIGHT

MECHANISM 27

D. ELECTRICAL INTERCONNECTION 27

SECTION 4 POST INSTALLATION INSPECTION 28

A. INTRODUCTION 28

B. MECHANICAL INSPECTION 28

C. BELT SPEED SENSOR ASSEMBLY 29

D. MANUALLY OPERATED TEST WEIGHT LIFTING MECHANISM

29

E. CONVEYOR 29



TABLE OF CONTENTS

DESCRIPTION PAGE

SECTION 5 CALIBRATION CALCULATIONS 30

THE TEST WEIGHT 30

ACCUWEIGH SCALES 30

ELECTRONIC (RESISTOR) CALIBRATION 33

SECTION 6 ROUTINE MAINTENANCE 35

LUBRICATION REQUIREMENTS 37

SECTION 7 DRAWINGS 38



SECTION 1

GENERAL SYSTEM DESCRIPTION

A. INTRODUCTION

The purpose of this manual is to instruct the user on the installation & maintenancerequirements of the Accuweigh weigh frame. The first section of this manualconcerns itself with system requirements. A separate manual supplements thismanual for the OPERATION functions of the System.

B. GENERAL SYSTEM DESCRIPTION

The ACCUWEIGH Belt Scale is used to totalize the throughput of bulk materialwhile being transported on a conventional (rubber type) belt conveyor.

The belt scale System comprises three (3) parts : the Weigh Frame which is used tomeasure the weight of material on the conveyor belt - the Belt Speed Sensor which isused to measure the travel of the conveyor belt - and the Electronic Transmitter,which operates on the material weight and belt speed signals to compute mass rateand totalization of the material passing over the scale.

The Belt Speed Sensor provides a signal proportional to the speed of the belt acrossthe scale, and the weigh frame provides a signal proportional to the weight-per-unit of length on the belt. These two signals are processed to produce a flow rate.Totalization is accomplished by integration. The totalizer may read out in any desiredunits of weight.

The system can also be used to close the loop with the primary flow control element.This element is typically a DC drive system connected to the conveyor itself, but mayalso be a depth control gate or a pre-feed device such as a screw or vibratory feeder.

10 Oct. 2002 Installation Manual - Accuweigh Weighframe ( Rev. 10.1) Page 4



SECTION 2

APPLICATION GUIDELINES

A. INTRODUCTION

The most important consideration in the use and installation of electro-mechanical belt conveyor scales is the application of the scale to the conveyor. The major causefor poor performance has been the mis-application of the scale to the conveyor.

The key to successfully applying the scale to the conveyor is to avoid locating thescale in any area of the conveyor where it is subjected to excessive belt tension or lifting of the conveyor belt. Always remember that the conveyor belt is an integral

part of the scale and, as such, must remain in contact with the weigh frame at alltimes.

B. APPLICATION GUIDELINES

THE GUIDELINES ON THE FOLLOWING PAGES MUST BE CLOSELYADHERED TO FOR APPLICATIONS REQUIRING A HIGH DEGREE OF

ACCURACY AND REPEATABILITY. ON INSTALLATIONS WHEREACCURACY IS NOT OF PARAMOUNT IMPORTANCE, SOME OF THEREQUIREMENTS MAY BE RELAXED.




SECTION 2

1. Least Tension Area (Fig. 1)

The first general rule that applies is to locate the scale in the area of lowest tension onthe conveyor. This location is normally near the tail pulley of the conveyor. High

belt tension adversely affects the accuracy of the scale.

2. Material Transition (Fig. 2)

The material to be weighed must settle on the belt before it is weighed. This requiresallowing a specified length of conveyor for the material to accelerate up to the speedof the belt. The factors that influence this distance are:

1. Belt Speed

2. Conveyor Angle of Inclination

3. Material Lump Size

4. Type of Transition




SECTION 2

Generally, the following guidelines apply:

BELT SPEED MINIMUM DISTANCE

30 - 90 m/min 1 - 1,5 metres

90 - 140 m/min 1,5 - 2,5 metres

140 - 180 m/min 2,5 - 4 metres

180 - 230 m/min 4 - 4,5 metres

230 - over 6 metres

The distance is measured from the end of the infeed skirt-boards to the idler adjacent

to the weigh frame.

A minimum of three idlers must be installed between the end of the infeed skirt- boards and the first scale idler.

For Certified (Custody Transfer) scale applications the scale shall be so installed that the first weigh idler of the scale is at least 6 metres or 5 idler spaces, whichever the greater, from loading point,skirting, or head or tail pulley in the conveyor. Alsothe distance from the loading point to the scale shall allow for adequate settling time of the material on the belt before it is weighed.

3. Belt Transition (Fig. 3)

On short conveyors, where the scale may be located close to the head pulley, theremust be a minimum number of fixed idlers between the scale weigh bridge and thehead pulley to avoid the lifting effect created by transitioning from the troughingidlers to the flat or crowned head pulley. The higher the troughing angle, the greater the effect and the more idlers needed between the scale and the head pulley.




SECTION 2

4. Belt Take-Up (Fig. 4)

An automatic take-up is recommended to maintain a uniform belt tension. The take-up should not be so heavy as to introduce excessive belt tension, and should bedesigned to allow the addition or removal of weights. A vertical gravity take-up isrecommended for high accuracy installations. It is suggested a conveyor engineeringhandbook (such as the "Goodyear Handbook of Conveyor Belting") be consulted for the derivation of the correct weight. If such a handbook is not available, a general ruleof thumb is: "the take-up weight should be no greater than the weight required to

prevent slippage at the drive pulley when operating the conveyor with the belt fullyloaded. If the sag between the carrying idlers is then greater than 2% of the carrier idler spacing, the spacing between the carrying idlers should be decreased".

If the conveyor is equipped with a manual (screw) take-up, it is recommended the belttension not be increased beyond the value that will produce less than 2% (of idler spacing) sag between carrying idlers.

For Certified (Custody Transfer) scale applications - if the belt length is such that atake-up device is required. this device shall be of the counter-weighted type for either vertical or horizontal travel.




SECTION 2

5. Construction (Fig. 6)

The conveyor structure must be rigid and resist deflection under load. No more than1,0 mm relative deflection between idlers should be allowed. A rigid section with four

(six for assized applications) fixed idlers either side of the scale weigh frame isrequired to eliminate relative deflection.

Expansion joints must not be located in the area of the scale (10 metres either side).

For Certified (Custody Transfer) scale applications the conveyor stringers at thescale and for not less than 6 metres before and beyond the scale shall be continuousor securely joined and of sufficient size and so supported as to eliminate relativedeflection between the scale and adjacent idlers under load. The conveyor stringersshould be so designed that the relative deflection betweem two adjacent idlers

within the weigh area does not exceed 0.6 mm under load.




SECTION 2

6. Conveyor Inclination (Fig. 7)

The conveyor inclination must not exceed the angle at which the material will slide backward and be re-weighed. This critical angle is dependent on the material beingconveyed. Normally, most conveyor manufacturers are aware of this critical angle for the particular application.

The inclination of the conveyor should also be fixed at one angle. Errors will resultwith changes in inclination.

For Certified (Custody Transfer) scale applications the conveyor if inclined, theangle shall be such that slippage of material along the belt does not occur.




SECTION 2

7. Curves - Concave (Fig. 8)

If the conveyor has a concave curve, the scale must be located at least 12 metres (21metres for Certified (Custody Transfer) applications) from the point of tangency, toavoid lifting effects of the belt.

For Certified (Custody Transfer) scale applications there shall be no concave in the

conveyor between the scale and the loading point. A concave curve beyond the scaleshall start no closer than 12 metres from the scale.

8. Curves - Convex (Fig. 9)

If the conveyor has a convex curve, the scale should be located as indicated below for specific troughing angles of the carrying idlers.

20 degrees Idlers: X = 2,5 metres or 2 Idlers

35 degrees Idlers: X = 4 metres or 3 Idlers

45 degrees Idlers: X = 5 metres or 4 Idlers

For Certified (Custody Transfer) scale applications the scale shall be so instqlled that the first weigh idler of the scale is at least 6 metres or 5 idler spaces, whichever

the greater, from any convex curve in the conveyor.




SECTION 2

9. Trippers (Fig. 10)

If the conveyor is provided with a tripper, the scale must be located at a point 12metres from the point of tangency of the belt - with the tripper fully retracted towardthe tail pulley. No trippers allowed for Certified (Custody Transfer) applications.

For Certified (Custody Transfer) scale applications the conveyor shall not incorporate any tripper or moveable head pulleys.




SECTION 2

10. Multiple Feed Points (Fig. 11)

Conveyors with multiple feed points should be avoided when high accuracy isrequired. Single feed points are preferred.

For Certified (Custody Transfer) scale applications multiple feeds points are not permissible.

11. Non-Uniform Loading (Fig. 12)

If the feed to the conveyor is not uniform, ploughs and leveling plates should beinstalled to re-shape and smooth out the load. Apron feeders often create non-uniform loading. Ideally, actual loading should be between 50% - 90% of scalecapacity, with less than a 5% variation in feed rate. The lineal belt loading must beoptimized (by choice of correct belt speed) for optimum performance.

For Certified (Custody Transfer) scale applications the conveyor loading mechanism shall be designed to provide uniform belt loading.




SECTION 2

12. Reversible Conveyors (Fig. 13)

The scale will not weigh accurately in both directions and any performance guaranteewould be based on weighing in one direction. Two complete scales are required for accuracy in both directions.

13. Wind Breaks (Fig. 14)

If the Scale location will be subjected to wind velocities over 8 km/h wind breaksshould be installed.

The wind break should extend 12 metres to either side of the scale, and 1,5 metresabove and below the belt line. The wind breaks should be attached to the sides of theconveyor, and a section should be easily removable for inspection of the scale.

Note: For outside applications, the conveyor must be fitted with a protective cover.




SECTION 2

14. Infeeds

The infeed to the conveyor must be interruptible to allow for empty belt calibration. If a pre-feed device is used, electrical circuitry should be provided to operate the scaleconveyor independently of the pre-feed device. If the conveyor "drags" the materialfrom a storage bin, the bin should be fitted with a cut-off gate.

For Certified (Custody Transfer) scale applicationsthe conveyor loading mechanism shall be designed to provide uniform belt loading. Feeding mechanismsshall have a positive closing or stopping action so that material leakage does not occur. Feeders shall provide an even flow over the scale through the full range of scale operation.

15. Scale Access

The conveyor should be equipped with an adequate platform or catwalk to allowinspection and servicing of the scale. It is recommended that the platform, or catwalks, be erected on both sides of the conveyor in the scale area.

For Certified (Custody Transfer) scale applications the scale shall be readilyaccessible.

16. Belt Flexibility

The belt should have the required flexibility to assure contact with all idler rolls.

17. Troughing Angle

Troughing angle should not exceed 35 degrees (20 degrees preferred).

18. Vibration

Vibration in the scale area should be at a minimum.

19. Conveyor Frame

The conveyor frame should not be directly connected to bins, feeders or other

equipment which may cause conveyor deflections/vibrations.




SECTION 2

For Certified (Custody Transfer) scale applications the conveyor stringers at thescale and for not less than 6 metres before and beyond the scale shall be continuousor securely joined and of sufficient size and so supported as to eliminate relativedeflection between the scale and adjacent idlers when under load. The conveyor stringers should be so designed that the relative deflection betweem two adjacent

idlers within the weigh area does not exceed 0.6 mm under load.




SECTION 2

20. Short Belts

Short belts must be considered by the factory for final approval.

21. Tracking

The belt must track properly if good accuracy is to be achieved.

For Certified (Custody Transfer) scale applications any training idlers shall belocated at least 18 metres from the centre line of the weigh span of the scale.

22. Belt length

The conveyor should not be longer than 600 metres, from head to tail pulley, for assize applications.

For Certified (Custody Transfer) scale applications the conveyor shall be no longer than 300 metres or shorter than 12 metres from head to tail pulley.

23. Belt mass

The conveyor belting should be no heavier than required for the application.

For (Custody Transfer) scale applications the belting shall be no heavier than isrequired for normal use. Under any load, the belt shall contact the center or horizontal portion of the idlers. Splices shall not cause any undue disturbance inscale operation.




SECTION 2

24. Idlers (Fig. 5 & 15)

THESE IDLERS ARE ACCEPTABLE

AVOID THESE IDLERS

Flat single roll, or 3 roll rigid frame, in-line troughing idlers designed for weighing

duty are required on the scale weigh bridge and 3 to 4 idlers either side. The idler rolloperating eccentricity tolerance should be 0,4 mm T.I.R. (Total Indicator Runout) or

better, for high accuracy installations.

The idler sets should be identical. Troughing angles (profiles) should be uniform witha maximum gap of 0.4 mm at the extreme ends, when checked with a template.

The idler rolls should be dynamically balanced to ensure that no vibrations/oscillations will exist on the weigh bridge. This is especially important on high beltspeed applications.

The idler bearings are not to be set in rubber bushes and the wing rolls should not leanforward.




SECTION 2

The idler frame should be carefully engineered for minimum deflection under load soas not to affect the alignment of the weighing platform under loaded belt conditions.This may require special steel sections to suit the application (the factory/supplier can

provide the necessary expertise in this regard).

Additionally the selection of roller diameter and roller shaft diameter should be madeonly after careful analysis of the belt loading, speed etc (the factory can provide thenecessary expertise in this regard).

Catenary or cable idlers must be avoided as well as off-set idlers.

Training idlers must not be located within 12 metres either side of the scale.

For Certified (Custody Transfer) scale applications the scale area and 4 idlers onboth ends of the scale shall be of contrasting colour, or other suitable means shall

be used to distinguish the scale from the remainder of the conveyor installation,and the scale shall be readily accessible. Also the belt shall not extend beyond theedge of the idler roller in the weighig area. Sufficient impact idlers shal be provided in the conveyor under each loading point to prevent the deflection of the belt during the time material is being loaded.




SECTION 3

INSTALLATION INSTRUCTIONS

A. WEIGH FRAME WITH OPTIONAL SPEED SENSOR

ASSEMBLY

1. Prior to installation of the weigh frame the belt should be run empty to study thecontact of the belt to the support idlers in the area of proposed installation. Also tocheck for sufficient clearance between the return belt and weigh carriage (the top of the return belt must be at least 380 mm below the top of the stringer).

2. For location of the scale within the conveyor check the guide lines as detailed insection 2. If "sited" by a Process Automation representative the stringer will be

marked with aerosol paint for the points of location of the flexure supports.3. Unpack the equipment with care and inspect for shipping damage and/or losses.

ANY CLAIM FOR SHORTAGES, ERRORS IN SHIPMENT, ETC., MUST BEMADE WITHIN 30 DAYS OF RECEIPT OF SHIPMENT. If idlers were purchasedwith the scale, skip the next step.

4. Select the idlers (See Item no. 5 of Application Guidelines) that will be installed onthe scale and in the scale area. Modify only the weigh frame mounting idler(s).

If troughing idlers are used, use a template to check the troughing angle and the widthof the "flat" at the bottom of the trough. Adjust troughing angle as required by

building up or grinding under the wing roller supports (if the troughing angle is notadjustable).

Check the T.I.R. (Total Indicated Runout) of the idlers to be installed in the scalearea and if necessary, machine to the specifications shown on the idler modificationdrawing.




SECTION 3

5. At the scale location area, raise the belt off the idlers and remove idlers, as required,to install the scale. Scale idlers and (3) idlers to either side of scale should beconsidered as being in the weighing region.

6. If the conveyor is fitted with a deck plate, remove deck plate as required (from +3idler through -3 idler) to allow installation of scale and Belt Speed Sensor.

Note: Ensure the Deck plate does not form part of the structural support (refer tonotes on the General Arrangement Drawing located at the end of the Manual).

7. Refer to the applicable “General Arrangement” drawing and "Torque transmitter suspension cable and adjustment mechanism" drawing.

8. Establish a reference line along the side of the stringer (using a builders line) parallelto the centre line of the belt. This line should extend from the +6 idler (6th before theweighframe) to the -6 idler (6th after the weighframe).

9. Position the approach and retreat sections of the weigh-frame into the stringers, usingthe idler mounting feet twisted outwards to support the frames from the stringers.Take note of the belt travel direction in relation to the weigh-frame installation.

10. Bolt the flexure mounts (item 9 - two pairs), to the approach and retreat frames.

11. Install support cables (items 6 a and 6 b - 2 pairs) onto torque transmitter item 2.Place the torque transmitter (item 2) into position. Place a 25mm spacer between thetorque transmitter and the approach frame. Couple the support cables (2 off "item 6b")

between the torque transmitter and the approach section of the weigh-frame. Finger

tighten the nuts on both sides of these support cables (item 6b), then slacken the lower nuts off one half a turn (to allow clearance to remove the spacers at a later stage).

12. Place the torque transmitter support (item 11) across the stringers. Couple the supportcables (2 off "item 6a") between the torque transmitter (item 2) and the torquetransmitter support (item 11). The torque transmitter support should be square to the

belt centre line (reference line) and level across the stringers.

13. Bolt loadcell assembly into loadcell support.

14. Place the load cell support in position so as to support the torque transmitter betweenthe loadcell limit stops (adjusting screws attached to the load cell support).

Note:- For scale sizes of 750mm and smaller, the loadcell will have to be coupled tothe torque transmitter in order to support the torque transmitter - care must be takenso that the loadcell is not overloaded.




SECTION 3

15. Adjust the nuts on the studs of the support cables (items 6a) protruding through thetorque transmitter support (item 11) so as to remove all slack on these cables. Check that these cables are perpendicular to the stringers and adjust if necessary by movingthe approach weigh carriage (item 1) in conjunction with the loadcell support (item 7)(This is centre of the the scale).

16. Ensure that the approach carriage (item 1) is square to the belt centre line (referenceline) and level across the stringers. Adjust the loadcell limit stops/loadcell cable to

bring torque transmitter (item 2) to the same incline as that of the stringers and weighcarriage.

17. Tighten the nuts of the support cables (item 6a) protruding through the torquetransmitter support (item 11) such that the torque transmitter is barely raised off the25mm spacers (enough only to allow the removal of the spacers).

18. Remove the 25mm spacers.

19. Lock the two lock-nuts against each other on the bottom of cable "items 6a" and thetop of cable "items 6b" - both sides - (refer drawing EMS-A3-0035). Note:- Ensurethat the "Dimension G adjusting nuts" (items 15) are pulled snugly against the angle

pieces but not pinched against the angle pieces - so as to allow adjustment via theadjusting screws.

20. Move the idler mounting feet back into position such that the approach section is nolonger supported by them.

21. Slack off the loadcell limit stops (adjusting screws attached to the load cell support)for approximately 5 mm free play.

22. Roughly balance the torque transmitter with counter balance weights.

23. Position the loadcell support (item 7), so that the loadcell rope is perpendicular to thestringers.

Note: Do not fix the loadcell rope to the torque transmitter yet.

24. Position the retreat frame such that its nose pieces are aligned with the nose pieces of the approach frame. Install the cables (2 off - item 5) connecting the approach andretreat frames (2 off - item 5). Ensure that the cables connecting the approach andretreat frames are perpendicular to the stringer. Adjust the nuts on both ends of thecables so as to have both approach and retreat frames in the same plane (level). Donot lock the nuts at this time. Level with torque transmitter which is level withstringer.

25. Level the rear of the retreat frame by shimming under the flexure mounts.

26. Check that the retreat weigh carriage is square and parallel to the stringer's, ref. lineestablishment in step 8. Adjust the cables if necessary.

Connect loadcell cable. Make sure the torque transmitter is parallel to the stringer andlevel across the stringer and the loadcell cable is perpendicular to stringer.

27. Re-check that the frame is still square and parallel to the stringer's Reference lineestablishment in step 8.

28. Transfer the mounting holes on the flexure mounts (4 off), loadcell support and torquetransmitter support (16 places) to the stringers and insert bolts. Use taper washers if necessary (if Process Automation installation kit is used, then weld mounting platesonto stringers).

29. Install +3 and -3 idlers such that they are square about the centre line of the belt.Place a spirit level on the flat (centre) roll of the +3 and -3 idlers and shim until theserolls are level). Place all other idlers in approximate position. Use ref, line established

in step 8.




SECTION 3

30. Position the idler on the approach frame closest to the torque transmitter support asthe reference idler, measure the distance from the centre of this idler to idlers on eachside of it up to the +3 and -3 idlers (both sides). Always measure from this referenceidler and not between adjacent idlers. Ensure these distances are identical and equal(or multiples of) Dimensions "H" (See General Arrangement drawing).

31. Run a length of builders line across the centre of the centre roll of the idlers, from the+5 idler to the -5 idler (either side of the weigh frame). Make sure the line is pulledtaut. This is to establish the idler line above which the weighing platform is to be

raised. Adjust (by shimming) the +3 and -3 idlers such that they are 6mm above thisidler line and also that the +3 and -3 idlers are higher than all other idlers betweenthem.

33. Run a length of builders-line, 20 mm in from the outer end of the wing rolls, to the +3and -3 idlers. Do this on both wing rolls. Make sure the line is pulled tight.




SECTION 3

34. Place a narrow 10 mm spacer (M12 nut) under each line at the +3 and -3 idlers.

35. Shim up all idlers between the +3 and -3 idlers until their rollers are all the samedistance from the 3 new lines, i.e. 10mm gap between roller and builder's line.

Note:- The gap between the lines and idler rolls should be 10mm. This should bechecked accurately with a reference spacer or similar.

36. Bolt down or tack weld the idlers permanently. Re-check the squareness of each idler to the stringers and weigh frame. Check the distance between each idler from the +3to the -3 idlers from the reference idler making sure they are the same or multiples of

the specified idler spacing. On Accuweigh scales, cross bracings must be installed togive support to the flexure mounts on both frames.

37. Release the torque transmitter (item 2) from the load cell support limit stops. Place the"Test Weight" in the "ZERO" position and re-balance the torque transmitter (withcounter balance weights).

38. Install 4 safety chains (as per drawing). These chains are to prevent possible damageto the conveyor belt in the unlikely event that any of the suspension cables should fail.

39. Install the speed sensor assembly (optional) on the conveyor per recommendedlocation on General Arrangement Drawing.

Note: The orientation of the belt travel wheel in relation to the direction of the belt

travel. Do not install backwards.

40. Observe the orientation of the speed sensor assembly in the conveyor. The assemblyshould be parallel to the conveyor (belt) line when the belt is in contact with the

wheel. When the belt is lifted, the wheel should be above the belt line by no morethan 20 mm.

Located on the underside of the belt speed sensor is a spring nut. With the beltlowered in place, adjust as required to achieve a tension of the wheel against the beltof no more than 3 kgf (30N).

Adjust the vertical height of the entire assembly, if required.

41. Be sure all fasteners are tight, remove all alignment equipment, and lower the beltonto the conveyor.

42. Check the clearance between the weigh frame(s) and the return belt.

43. With belt running check belt tracking and if possible check belt tracking withmaterial.




SECTION 3

B. SPEED SENSOR (WITHOUT OPTIONAL SPEED SENSOR

ASSEMBLY

The tachometer monitors the conveyor speed. It must be mounted properly so that itcan be driven at the proper speed. User's shaft revolutions per minute (RPM) must bein excess of 24 RPM when belt speed is maximum for the standard model PT-500tachometer or in excess of 1 RPM for the optional model PT-500-LS tachometer designed for slower belt speed applications.

The drive pulley must have positive contact with the conveyor to insure accuratecorrelation of the speed of the tachometer with the conveyor speed.

For accurate operation, select one of the following locations on the conveyor for driving the tachometer:

1. On any close snub pulley where the conveyor has adequate tension andwraparound to prevent slippage.

2. On the tail pulley, making sure that the tachometer will move with anyadjustment of this pulley.

3. For high accuracy applications or for "Assize" installations, the belt speed should be measured adjacent to the weighing area i.e. the belt speed and belt loadingshould be measured at the same place on the belt. (Belt speed errors of 2-5% are

possible due to the effects of belt stretch and/or motor slip).

Conveyor locations not recommended for the positioning of the tachometer includethe following:-

1. Do not use a pulley that is in contact with the side of the conveyor handlingmaterial. Material build-up may cause a decrease in speed which introduces anerror into the system.

2. Do not use a "head" pulley if there is any possibility of slippage. This slippage is prevalent on conveyors that are long, inclined or loaded heavily.

Make the mechanical connections from the drive pulley to the tachometer carefully to prevent any eccentricity of the couplings which could cause the output signal to vary.

When a tachometer drive assembly is supplied, the dimensions of the Tachometer drive unit and installation details are shown in the appropriate drawing in the sectionof the manual covering the PT-500 tachometer.




SECTION 3

C. (OPTIONAL) MANUALLY OPERATED TEST WEIGHT

MECHANISM

Normally the calibration checking of Accuweigh Scales requires that the single OnBoard Test Weight be man handled from it’s Rest or Zero position to the Span

position and back again.When an application requires an On Board Test Weight that is difficult to manhandledue to it’s size and mass, a lifting mechanism is available as an option. This providesa lever mechanism, with appropriate mechanical advantage, to allow the applicationand removal of the Test Weight, to be performed with minimum effort.

Since this Test Weight lifting mechanism only removes or applies the test weight to a particular position on the weigh frame, two (identical in Mass) Test weights c/wLifting mechanism are required on Accuweigh scales.

Follow the installation and set-up instructions on the drawing.




SECTION 3

D. (OPTIONAL) ELECTRICALLY OPERATED TEST WEIGHT

MECHANISM

When an application requires that the On Board Test Weight be operatedautomatically, so as to allow automated calibration checking, this option provides the

solution.These test weight lifting mechanisms are available in either single or dual formats.

SINGLE MECHANISM


position and back again.

This Test Weight lifting mechanism only removes or applies the test weight to a particular position on the weigh frame.


DUAL MECHANISM


position and back again.

Since this Test Weight lifting mechanism only removes or applies the test weight to a particular position on the weigh frame, two (identical in Mass) Test weights c/wLifting mechanism are required on Accuweigh scales equipped with dualmechanisms.


D. ELECTRICAL INTERCONNECTION

The Transmitter Operating manual and Interconnect Drawing(s) therein provideswiring details and specifications for power and signal cables. Cables from certainsensors can be up to 1000 metres long. An armoured and shielded cable is normallyused.

Follow the Interconnect Drawing notes and details on how to make the input andoutput connections.

Note: FOLLOW LOCAL ELECTRICAL CODES FOR ALL NTERCONNECTIONS




SECTION 4

POST INSTALLATION INSPECTION

A. INTRODUCTION

Before initial calibration is attempted, the installation should be thoroughlyinspected, mechanically and electrically, to insure that some frequently madeinstallation deficiencies have not been over-looked.

B. MECHANICAL INSPECTION

Scale/Scale Idlers

- Double check the installation dimensions to ensure the scale is installed per the General Arrangement Drawing.

- Be certain all bolts which secure the scale to the conveyor are tight.

- Check the lock nuts on the scale's cables for tightness.

- All idlers in the scale area must be securely fastened in place. It issuggested their positions be sealed to prevent accidental relocation.

- Check the modified scale supported idler(s) to ensure there is adequateclearance (more than 20 mm between the idler(s) and the stringer(s).

- If the conveyor is fitted with a protective cover, be certain there is adequateclearance between the conveyor covers and the weigh idler(s).

- The return side of the conveyor belt should pass clear of the under-side of the scale. Install a snub pulley if necessary.

- Verify that the "Test Weight" is locked in the correct ZERO (or normaloperating) position. On some models, the test weight is carried on the scaleat all times, and its position is changed for SPAN testing.

- Verify that the conveyor belt is in proper contact with the +3 through -3

idlers at all times.




SECTION 4

C. BELT SPEED SENSOR ASSEMBLY

- Verify the mounting direction.

- Be certain the mounting bolts are tight.- Check the tension in the "following" spring to ensure that the tension

between the belt and the tachometer drive wheel is approximately 3 kgf (30 N).

- Where applicable, check the flexible coupling between the drive wheel andthe tachometer. Be certain the coupling set screws are tight.

D. MANUALLY OPERATED TEST WEIGHT LIFTING

MECHANISM

- Operate each lever mechanism (both Zero and Span Test weight levers),checking that the Test weights do not foul when raised and are fullysupported by the torque transmitter when lowered.

- Ensure the levers are locked in their appropriate positions (lowered for Zero and Raised for Span) after the checking above has been completed.

E. CONVEYOR

- If the conveyor is equipped with a gravity take-up, be certain the take-upcarriage is free.

- Start the conveyor belt, and check the belt tracking (Refer to Appendix E)for information. Do not attempt to track by "knocking" idlers in thescale area!




SECTION 5

CALIBRATION CALCULATIONS

THE TEST WEIGHT

After the initial calibration of the scale it is usually fairly accurate, depending on the

calibration method used. Also, from time to time, the scale has to be returned to it’s

original calibration. For this purpose a calibration reference or standard should be used.

An on board Test Weight provides a quick, easy and low cost calibration reference.

While the (optional) test weight is normally supplied as a movable mass piece, which is

manually placed in the "SPAN" position, a lifting device may be supplied optionally. In

the event a lifting mechanism is provided, it is important to note that the "SPAN" position

is in fact the test weight lifted off the "REST" position.

The following defines the relationship between the Test Weight mass and it’s effect on

the belt scale.

A = Force per idler, due to belt loading, perpendicular to the belt.

=S ⋅ ⋅

[kg/m]Cos Beltloading ϕ

1000

where:-

ϕ = Conveyor incline angle at scale location [degrees].

C = Force on (at) the loadcell [kg].

T W = Test weight mass [kg].

S = Idler pitch [mm].

(%) = Percentage of maximum (calibrated) belt loading, to be represented by the

Test Weight

ACCUWEIGH SCALES

On Accuweigh weighframes, the test weight is standardly supplied as a mass piece,

which is manually moved between the "ZERO" and "SPAN" positions. On occasions an

optional lifting device may be supplied. This may be either for convenience or for

applications where the mass of the test weight is too much to handle. The operation of the

lifting mechanism may be either manual or electrically operated (where this operation isto be automated).

In the event a lifting mechanism is provided it is important to note that the "SPAN"

position may be either; the test weight lifted off the "ZERO" position or the test weight

lifted off the "ZERO" position plus the appication of a (identical) second test weight to

the "SPAN" position.

In order to perform a theoretical calibration using the Test Weight, certain as built

dimensions are required.




SECTION 5

Some of these dimensions are difficult to measure accurately due to lack of access. In

order to accurately determine some dimensions from the scale, used in the theoretical

calibration calculations, it is possible to calculate these dimensions from other (easier to

measure) dimensions viz.;.

Distance - loadcell cable to torque transmitter support cable (left) = K1Distance - loadcell cable to torque transmitter support cable (right) = K2

Distance between torque transmitter support cables (left and right) = N

Distance - torque transmitter support cable to centre line testweight "span" position (left) = L1

Distance - torque transmitter support cableto centre line test weight "span" position (right) = L2

Distance - torque transmitter support cable to centreline, test weight "zero" position (left) = M1

Distance - torque transmitter support cable to centre linetest weight "zero" position (right) = M2

Conveyor incline angle = ϕ degrees

Distance loadcell to torque transmitter support cable = D

Distance torque transmitter support cable to centre lineof test weight SPAN position = E.

Distance torque transmitter support cable to centre line of test weight ZERO position = F

Force at loadcell (C) = Test weight mass x lever ratio x Cos ϕ [kgf]

Now the Equivalent belt loading [kg/m] for the Test Weight T is:-W

ACCUWEIGH TWO

The following defines the relationship between the test weight mass T and it’s effect on

the Accuweigh Two belt scale. The belt loading represented by the Test Weight T is

defined by:-

W

W

Belt loading = A

Cos ⋅ φ

=( ) ( )T E F S H

S G

W ⋅ + ⋅ −⋅ ⋅

2

2

Note: The result of the calculated belt loading is in [kg per idler pitch]. This needs to be

multiplied by 1000/S in order to have the result in [kg/m].




SECTION 5

ACCUWEIGH FOUR

The following defines the relationship between the test weight mass and it’s effect on the

Accuweigh Four belt scale. The belt loading represented by the Test Weight T is

defined by (refer to drawing EMS-A3-0052):-W

Belt loading = A

Cos ⋅ φ

=( ) ( )T E

F S H

S G

W ⋅ + ⋅ −⋅ ⋅

2

4



ACCUWEIGH SIX

The following defines the relationship between the test weight mass and it’s effect on the

Accuweigh Six belt scale. The belt loading represented by the Test Weight T is defined

by (refer to drawing EMS-A3-0051):-W

Belt loading = A

Cos ⋅ φ

=( ) (

( )

)T E F S H

G S

W ⋅ + ⋅ + −⋅ ⋅ +

2 5 250

6 250

.






SECTION 5

ELECTRONIC (RESISTOR) CALIBRATION

C = Force on (at) the loadcell [kg].

K = Load cell sensitivity [mV/V].

R1 = Load cell resistance [Ohm].

RS = Calibration shunt resistor [Ohm].

Wf = Weigh frame factor.

= that fraction of the force, due to load onto the belt, reflected at the

loadcell.

= ( )

2

2

⋅ ⋅

−

S G

H

(

D S for Accuweigh Two scales (the lever ratio is variable on thesescales).

=)

4

2

⋅ ⋅−

S G

D S H

(

for Accuweigh Four scales (the lever ratio is variable on

these scales).

=( )

)

6

2 5

⋅ +⋅ +

G S

D S .

250

250 − H for Accuweigh Six scales (the lever ratio is variable

on these scales).

Where:-

S = Idler pitch [mm].

φ = Conveyor incline angle at scale location [degrees].

F = Force at the loadcell [kgf].

A = Belt loading [kg/m].

Now F A Cos W f = ⋅ ⋅ ⋅φ




SECTION 5

It is possible to simulate load on the loadcell by placing an appropriate shunt resistor

across the loadcell. The effect of the shunt resistor is defined by the following formula:-

F

C

K

R

RS R= +

2

1

2 1

Therefore since F = F

A Cos W C

K

R

Rs R f × × =+

φ2

1

2 1

or the shunt resistor RS required to give a simulated belt loading of A [kg/m].

R

C R

A Cos K W R

s

f =

⋅⋅ ⋅ ⋅

−

1

12

2

φ




SECTION 6

ROUTINE MAINTENANCE

Due to the unique design of the Process Automation Accuweigh weighframe, maintenance

requirements are of a minor nature.

Physical maintenance involves the good housekeeping of the system (weigh frame, loadcellassembly, weigh idlers, tachometer, tachometer drive etc.). The sensors should be kept clean

and free of spillage.

Special care should be taken to ensure that no build-up of dirt occurs between the weigh

frame and any supporting structure which could interfere with the measurement.

As the weigh idlers, tachometer/drive assembly are the only parts making physical contact

with the conveyor belt, the condition of these should be checked frequently. When supplied

with the optional Tachometer Drive Assembly (TDA), the two drive bearings should be

checked and greased (with Lithium based General Purpose grease) at least once, preferably

twice, per annum for normal applications - more often for applications in harsh and/or wet

environments.

The Test Weight and counter balance weights must be securely locked in position.

The idler alignment on the weigh frame should be checked initially three months after

installation, and at least annually thereafter, but preferably every six months if optimum

performance is required.

LOADCELL

The scale force transducer (loadcell) requires little maintenance. The main consideration is

that the steel cable which is connected to the loadcell be plumb so as to transfer a force to the

loadcell which is perpendicular to the loadcell.

On those scale models supplied with a loadcell protection assembly, the gap between the

loadcell and the overload stop should be checked for any dust/dirt build-up. Ensure that

sufficient clearance exists so as to allow a sheet of paper to pass through freely.

Care should be exercised in the handling of low capacity loadcells which may be destroyed

by overloads.




SECTION 6

SPECIAL TOLERANCE (WEIGH DUTY) IDLERS

Weigh duty idlers should not be equiped with grease points as this could affect the operation

of the weighing system. The typical lifespan of weigh duty conveyor idlers (rollers) is from 2

to 4 years. Severe operating conditions could result in a reduction of this time.

Close attention should be given to the idlers on the weigh platform (where the weigh platform is defined as the section comprising the weigh frame with it’s weigh idlers, plus the 3

approach (before) and 3 retreat (after) idlers). These idler rollers should be parallel, round (no

flat surfaces) and should rotate freely. The idlers bases should also be in sound condition,

which may be checked by using lines strung from the +4 idler to the -4 idler, as is done for

their alignment (refer installation manual).

The Total Indicated Run-out (TIR) of any roller - which is an indication of the roller

eccentricity - should be within 0.3 mm across its full face.

Also check the rollers for signs of bearing wear. This may be done by using a vibration

monitor or such similar device.

When an idler roller is found to be faulty, it should be removed immediately and replaced. If

a weigh platform idler is replaced, the idler alignment must be checked as well as the zero

calibration (tare check with auto correction).

CARE OF TEST WEIGHT

Ensure that any Test Weight supplied with the scale, is installed an in the proper location on

the weighframe!

A Test weight, when furnished with the system, is manufactured to simulate a constant and

steady material loading so as to allow for accurate referencing/calibration of the system.

Accordingly, it is of major importance that Test Weight(s) be inspected periodically to prevent any change in the weight of this reference mass piece(s).

WEIGH PLATFORM ALIGNMENT

The scale should be checked for mechanical alignment of the idlers in the weighing area (+3

through -3 idlers).

The frequency of this check is a direct function of the condition of the conveyor into which it

is installed. The more rigid the conveyor system the less frequent needs to be the checks.

In any event it is wise to check the system within three months of initial installation and six

monthly thereafter. Process Automation offer a Maintenance Agreement whereby these andother Maintenance items are checked and adjusted on a routine basis thereby ensuring

optimum performance with a minimum of equipment downtime.

SPEED SENSOR DRIVE ASSEMBLY

When supplied with the optional Tachometer Drive Assembly (TDA), the two drive bearings

should be checked and greased (with Lithium based General Purpose grease) at least once,

preferably twice, per annum for normal applications - more often for applications in harsh

and/or wet environments.

The contact wheel of the Belt Speed Sensor Assembly should be inspected periodically for

build-up of material or wear. Build-up may be found to occur in the tensioning spring




SECTION 6

mechanism, which ensures proper contact between the wheel and the belt, and on the wheel

itself.

If build-up is occurring, a maintenance schedule for cleaning must be implemented. If the

wheel shows signs of wear this should be corrected for by performing a "Speed calibration

check", provided the wear is acceptable. If the wear is excessive the wheel(s) should bereplaced and a "Speed calibration” performed.

The tension of the wheel to the belt should be verified to be approx. 3 kgf (30 N).

Regular visual checks should be made to ensure the wheel is turning and that the spring

loaded carrier assembly is maintaining the wheel's contact with the belt. Applying a bright

colour paint to one spoke on the wheel provides a visual "reference" to detect if the wheel is

"slipping".

The hinge on the tachometer drive assembly should be checked for free play. Material

spillage etc., may cause the unit to jam thereby resulting in (speed) measurement errors.

Also check the rollers for signs of bearing wear. This may be done by using a suitablevibration monitor or such similar device.

Should the application have sufficient water on the bottom of the conveyor belt so as to result

in the slipping of the drive wheel, an optional wet wheel is available. This wet wheel has

machined grooves in the wheel to allow a path for the excess water to be displaced sideways,

away from the wheel, thereby preventing the aqua-planing of the wheel.

Note: Should the amount of water be excessive, the tachometer should be relocated to a more

favourable spot or the cause for the water should be removed.

LUBRICATION REQUIREMENTSThe only equipment requireing lubrication is the optional Tachometer Drive Aseembly

(TDA) used to cou[le the conveyor to the speed sensor (tachometer).

The two drive bearings on the TDA should be checked and greased (with a Lithium based

General Purpose grease) at least once, preferably twice, per annum for normal applications -

more often for applications in harsh and/or wet environments.

The tachometer internal bearings are grease for life and normally require no greasing.




SECTION 7

DRAWINGS

Principle of operation Accuweigh scales EMS-A3-0013

General arrangement drawing - Accuweigh Two scales EMS-A3-0004

General arrangement drawing - Accuweigh Four scales EMS-A3-0002

General arrangement drawing - Accuweigh Six scales EMS-A3-0001

General arrangement drawing - Accuweigh Two scales- Heavy Duty version EMS-A3-0175

General arrangement drawing - Accuweigh Four scales- Heavy Duty version EMS-A3-0177

General arrangement drawing - Accuweigh Six scales- Heavy Duty version EMS-A3-0176

Force calculations Accuweigh Two scales EMS-A3-0194

Force calculations Accuweigh Four scales EMS-A3-0052

Force calculations Accuweigh Six scales EMS-A3-0051

Accuweigh scale torque transmitter suspension cable &adjustment mechanism EMS-A3-0035

Load cell assembly EMS-A3-0011

Drive Assy for PT-500 Tachometer TAC-A3-0018

Integrated Tachometer Drive Assy for PT-501 Tachometer TAC-A3-0040

Manually operated (dual) Test Weight lifting Mechanism EMS-A3-0186

Automatically operated (dual) Test Weight lifting Mechanism – for Accuweigh Scales. EMS-A3-0197

Interconnect diagram - Electrically operated automatic (dual)Test Weight lifting system. WIR-A4-0072




































Accuweigh Installation Manual Rev.10.1.pdf

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