Milltronics MMI-2 User manual

MMI-2
2 IDLER BELT SCALE
Instruction Manual PL-327 January 2001
MMI-2 BELT SCALE
33453270
Rev. 2.3

© Siemens Milltronics Process Instruments Inc. 2001
Safety Guidelines
Warning notices must be observed to ensure personal safety as well as that of others, and to protect the product and the connected equipment.
These warning notices are accompanied by a clarification of the level of caution to be observed.
Qualified Personnel
This device/system may only be set up and operated in conjunction with this manual. Qualified personnel are only authorized to install and
operate this equipment in accordance with established safety practices and standards.
Warning:This product can only function properly and safely if it is correctly transported, stored, installed, set up, operated, and maintained.
Note: Always use product in accordance with specifications.
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Instruments Inc. 2000. All Rights Reserved Disclaimer of Liability
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Inc. will not be responsible for the contents of partial or
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While we have verified the contents of this
manual for agreement with the instrumentation
described, variations remain possible. Thus we
cannot guarantee full agreement. The contents of
this manual are regularly reviewed and
corrections are included in subsequent editions.
We welcome all suggestions for improvement.
Technical data subject to change.
MILLTRONICS®is a registered trademark of Siemens Milltronics Process Instruments Inc.
Contact SMPI Technical Publications at the following address:
Technical Publications
Siemens Milltronics Process Instruments Inc.
1954 Technology Drive, P.O. Box 4225
Peterborough, Ontario, Canada, K9J 7B1
Email: [e-mail]
For the library of SMPI instruction manuals, visit our Web site: www.milltronics.com

TABLE OF CONTENTS
Title Page
ABOUT THIS MANUAL 1
ABOUT THE MMI-2 1
SPECIFICATIONS 2
OPERATION 3
INSTALLATIONPreamble 4
Welding 4
Load Cell Handling 4
Installation Procedure 5
CALIBRATION General 8
Test Load 8
Zero 8
Span 8
Material Test 9
Re-Rating 9
MAINTENANCE AND SPARE PARTS 9
IDLER MOUNTING
Troughed Idler with Channel Spine 10
Troughed Idler with Pipe Spine 11
Flat Idler 12
MSI WIRING 13
OUTLINE DIMENSIONS-CEMA 14
OUTLINE DIMENSIONS-METRIC 15
PL-327 i

ABOUT THIS MANUAL
This instruction manual, PL-327, covers the installation, operation and maintenance of the MMI-2 belt scale.
It is imperative that this manual be read and understood before installation and start up of any component of
the weighing system to which the MMI-2 is being applied. Adhering to the installation and operating
procedures will insure a quick, trouble free installation and allow for the maximum accuracy and reliability of
your weighing system to be achieved.
As the MMI-2 belt scale is used in conjunction with an integrator and optional speed sensor, the instruction
manuals covering these components must be read as well.
ABOUT THE MMI-2
The Milltronics Multiple Idler (MMI-2) is a belt scale application using two Milltronics Single Idler (MSI) belt
scales in succession. The scales are designed to be inserted into belt conveyors for continuous weighing of
dry bulk solids.
Each MSI is comprised of the following: - one weighbridge c/w two load cells with cables run in a
common flexible conduit
- test weight(s)
The addition of an idler (supplied and installed by customer) to each weighbridge completes the weighing
assembly. The MMI load cells provide an electronic signal, proportional to load, which is fed to the Milltronics
CompuScale series integrator. Thus, weighing is accomplished without disturbing the process and without
affecting the process material.
The MMI-2 is used where conveyor belt speeds or belt loading charactistics result in conditions that
necessitate extending the weighing time beyond the capibilities of a single idler scale. It is also well suited for
applications that require higher sustained accuracies, such as production control inventory accountability or
where certification for trade purposes is required.
It is important to understand that the MMI-2 is an accurate and repeatable force sensor. Its performance is
ultimately dependent upon the conveyor system and the quality of the installation and alignment.
PL-327 1

SPECIFICATIONS
Accuracy: » ±0.25% of totalization over 5 to 1 operating range
in factory approved installations
Belt Width: » 18" to 96" in CEMA sizes
» 500 to 2000 mm in metric sizes
» refer to Outline and Dimensions
Belt Speed: » up to 4 m/s (800 fpm)
Capacity: » up to 5000 TPH at maximum belt speed
Conveyor Incline: » ±20°from horizontial, fixed incline
» up to ±30° with reduced accuracy
Conveyor Idler: » flat to 35°
» up to 45°with reduced accuracy
Idler Diameter: » 50 to 180 mm (2 to 7")
Idler Spacing: » 0.5 to 1.5 m (1.5 to 5.0 ft)
Load Cell: » excitation: » 10 V DC nominal
» 15 V DC maximum
» output: » 2 mV / V excitation at rated load cell capacity
» non-linearity: » 0.02% of rated output
» hysteresis: » 0.02% of rated output
» non-repeatability: » 0.01% of rated output
» capacity: » maximum ranges: 50, 100, 250, 500, 750,1000 lb
» overload: » maximum 1000% of rated capacity
» temperature: » – 40 to 85 °C (– 40 to 185 °F) operating range
» – 15 to 65 °C ( 5 to 150 °F) internally compensated
Approvals: › CSA certified for general purpose
Hazardous Locations: › with the use of approved intrinsically safe barrier strips
Weight: › see chart, Outline and Dimensions
PL-327 2

OPERATION
idler frame
scale mounting bracket
dynamic beam
static beam
test weight bar
idler bracket
Force
idler clip
Each MSI weighbridge is designed to react to the vertical component of the force being applied to it. Each MSI
consists essentially of a static assembly and a weighing assembly.
The static assembly is used to mount each MSI between the conveyor stringers and supports the weighing
assembly via its load cells.
The weighing assembly supports the scale idler and transfers the weight of the material to the load cells.
These are the active components in the weighing assembly.
As the material travels along the conveyor, a force is exerted through the suspended idler onto the weighing
assembly. The weighing assembly is forced down proportionally. The movement in each load cell is sensed
by its strain gauges. These modulate the excitiation signal from the electronic integrator to produce a signal
proportional to weight, which is returned to the integrator. The movement in the load cell is limited by the
positive stop incorporated in the design of the load cell.
weigh
bridge
PL-327 3

INSTALLATION
PREAMBLE
The MMI-2 is shipped from the factory, attached to a frame for protection. Each MSI weighbridge must be
removed from its shipping frame and inspected for physical damage.
Insure that the conveyor design meets the installation requirements for the Milltronics MMI-2 scale. The
conveyor stringers must be rigid, straight, parallel to and square with the belt line in the area of the scale
installation. The idlers to be used on the scale and at least the next two approach and retreat idlers must be
of the same style and manufacture and in good condition.
Prepare the site in accordance with the Milltronics drawing(s) provided or by reference to Milltronics
instruction manual PL-328, Applications Guidelines.
WELDING
Extreme caution should be used when arc welding in the area of the belt scale. Insure that no welding current
can flow through the belt scale. Welding currents through the scale are sufficient to functionally destroy the
load cells.
LOAD CELL HANDLING
The load cell can tolerate very little negative displacement, otherwise the load cell will be functionally destroyed.
When handling the individual MSI’s install both shipping stops to their vertical position to protect the load cells.
Do not lift the MSI’s by the weighing assembly or subject it to shock from blows of a hammer when trying to
position it.
DO NOT STAND OR WALK ON THE SCALE.
OVERLOADING, SHOCK AND TWISTING OF THE SCALE CAN ALL
FUNCTIONALLY DESTROY THE LOAD CELLS.
PL-327 4

INSTALLATION PROCEDURE
1. Remove the conveyor idlers currently at the desired points of installation.
2. Remove the foot plates and modify the idler frame at both ends of the idlers as shown .
3. Insert the MSI’s in the place of the removed idlers. The MSI is designed to use the existing holes in the
stringer and should not require further drilling. Install the mounting bolts and nuts, but do not tighten .
Remove the idler clips. Refer to Outline and Dimensions.
Insure that there is sufficient clearance between the return belt and the MSI and test weight (when used
during the calibration procedure).
12.7 mm
(0.5")
before
100 mm
(4")
after
customer’s idler
MSI belt scales
location of
removed idlers
material flow
test weight(s) test weight(s)
PL-327 5

4. Position the individual MSI’s such that they are centered and square to the stringer. Mount the modified
idlers such that they are centered onto the scale using the idler clips. Tighten all mounting hardware.
Refer to Idler Mounting for alternate idler mounting arrangements.
Orient the scale so that the large arrow on the scale mounting brackets is pointing in the direction
of material flow.
5. Release the shipping stops on each MSI in order to free the weighing mechanism. Loosen screws ‘A’ and
rotate both shipping stops inward until the underside slots slide around the shoulder bolts ‘B’. Tighten
screws ‘A’ to secure in place.
idler clips
conveyor stringer
(typical)
‘B’ shoulder bolts shipping stop
shipping stop
‘A’ screws
PL-327 6

6. The idlers in the weighing area must be properly aligned and leveled by shimming the scale idler (S#), the
two approach (A#) and the two retreat idlers (R#) until they are within ±0.8 mm (1/32") of each other.
Be sure to check that the idlers are centered and squared to the conveyor during the shimming process.
7. Precise idler alignment is very important if maximum accuracy of the weighing system is to be achieved.
Misaligned idlers will result in unequal forces being applied on each idler in the weighing area, causing
calibration and measurement errors. Use a good quality wire or string to check for alignment. The wire
or string must be able to withstand sufficient tension as to eliminate any sag. By shimming, make the
necessary adjustments to bring all the rolls of the A2 through to the R2 idlers in line within 0.8 mm(1/32").
S 2
MSI with modified scale idler
R 1
wire or string
(for alignment)
approach idlers
retreat idlers
R 2
A 2
S 1
A 1
CC
idlers must be square to stringers
alignment of idlers
A 2 to R 2 to be within
±0.8 mm (1/32") material flow
Center of
idlers to
be in line
R 2
S 1 R 1
A 2
90°
S 2A 1
PL-327 7