—
A B B M EA SUREM EN T & ANA LY TI CS
Pressductor Pillowblock Load Cells
Vertical Measuring PFCL 201
User manual
3BSE023881R0101 en Rev I
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NOTICE
The information in this document is subject to change without notice and should not be construed as a commitment by ABB
AB. ABB AB assumes no responsibility for any errors that may appear in this document.
In no event shall ABB AB be liable for direct, indirect, special, incidental or consequential damages of any nature or kind arising
from the use of this document, nor shall ABB AB be liable for incidental or consequential damages arising from use of any
software or hardware described in this document.
This document and parts thereof must not be reproduced or copied without ABB AB’s written permission, and the contents
thereof must not be imparted to a third party nor be used for any unauthorized purpose.
The software described in this document is furnished under a license and may be used, copied, or disclosed only in accordance with the terms of such license.
CE-marking
This product meets the requirements
that the installation is carried out in accordance with the instructions given in this manual.
© Copyright 2004- 2020 ABB. All rights reserved.
specied in the RoHS directive 2011/65/EU and EMC directive 2014/30/EU provided
2
Table of Contents
1 Introduction
1.1 About this Manual......................................................................................... 5
1.2 Disposal and Recycling................................................................................. 5
1.2.1 Environmental Policy..................................................................................... 5
1.2.2 Recycling Electrical and Electronic Equipment, WEEE................................... 5
1.2.3 Recycling the Transport Material................................................................... 6
1.2.4 Disposal of the Product................................................................................. 6
1.3 Function and Design..................................................................................... 6
1.3.1 General......................................................................................................... 6
1.3.2 Load Cells PFCL 201.................................................................................... 7
1.3.3 Principle of Measurement.............................................................................. 7
2 Description
2.1 General......................................................................................................... 9
2.2 Technical Data............................................................................................ 10
2.3 Denitions................................................................................................... 11
2.4 Measuring principle of the sensor................................................................ 14
2.5 Mounting Arrangement............................................................................... 14
2.5.1 Coordinate System..................................................................................... 14
2.5.2 Horizontal Mounting.................................................................................... 15
2.5.3 Inclined Mounting........................................................................................ 16
2.6 The Electrical Circuit................................................................................... 17
3 Installation
3.1 General ...................................................................................................... 18
3.2 Unpacking.................................................................................................. 18
3.3 Preparations............................................................................................... 18
3.4 Mounting ................................................................................................... 19
3.5 Cabling for Load Cell PFCL 201CE............................................................. 20
4 Commissioning
4.1 General....................................................................................................... 22
4.2 Preparatory Calculations............................................................................. 22
5 Maintenance
5.1 General....................................................................................................... 23
5.2 Preventive Maintenance.............................................................................. 23
5.3 Spare Parts................................................................................................. 23
6 Fault Tracing
6.1 General....................................................................................................... 25
6.2 Interchangeability........................................................................................ 25
6.3 Fault Tracing Procedure.............................................................................. 25
6.4 Fault Tracing in the Mechanical Installation.................................................. 26
6.4.1 Defective Mounting Surface, Support or Adapter Plates.............................. 26
6.4.2 Force Shunting........................................................................................... 26
6.4.3 Fastening of Load cell and Adapter Plates.................................................. 26
6.4.4 Rolls and Bearings...................................................................................... 26
6.4.5 Driven Roll.................................................................................................. 26
6.5 Fault Tracing of Load Cells, Junction Boxes and wiring............................... 27
A Drawings
A.1 Load Cell PFCL 201C, Dimension Drawing................................................. 29
A.2 Load Cell PFCL 201CE, Dimension Drawing............................................... 30
A.3 Load Cell PFCL 201CD, Dimension Drawing............................................... 31
A.4 Adapter Plate Upper PFCL 201, Dimension Drawing................................... 32
A.5 Adapter Plate Lower PFCL 201, Dimension Drawing................................... 33
Alphabetical index
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
1 Introduction
Introduction
1
1.1 About this Manual
This manual describes the load cells PFCL 201C/201CE/201CD in a Pressductor® Strip Tension
Measuring System.
The purpose of this manual is to describe the general function and design of the load cells and also
to be a guidance at installation, commissioning, preventive maintenance and fault tracing.
1.2 Disposal and Recycling
1.2.1 Environmental Policy
ABB is committed to its environmental policy. We strive continuously to make our products environmentally more sound by applying results obtained in recyclability and life cycle analyses. Products, manufacturing process as well as logistics have been designed taking into account the environmental aspects.
Our environmental management system,
environmental policy. However it is on the customer’s responsibility to ensure that local legislation is
followed.
1.2.2
Recycling Electrical and Electronic Equipment, WEEE
certied to ISO 14001, is the tool for carrying out our
The crossed – out wheeled bin symbol on the product(s) and / or accompanying documents
means that used electrical and electronic equipment (WEEE) should not be mixed with general
household waste.
If you wish to discard electrical and electronic equipment (EEE), in the European Union, please
contact your dealer or supplier for further information.
Outside of the European Union, contact your local authorities or dealer and ask for the correct
method of disposal.
3BSE023881R0101 en Rev I 5
Disposing of this product correctly will help save valuable resources and prevent any potential negative effects on human health and the environment, which could otherwise arise from inappropriate
waste handling.
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
1.2.3 Recycling the Transport Material
ABB designs all transport material to be recyclable where practical. The recycling of the transport
material depends on the material type and availability of local recycling programs.
After receiving the system into the site, the package and the transportation locking have to be
removed. Recycle the transport material according to local regulations.
1.2.4 Disposal of the Product
When the product is to be disposed, it should be dismantled and the components recycled
according to local regulations.
1 Introduction
1.2.4.1
Dismantling and Recycling of the Product
Dismantle and recycle the components of the product according to local regulations.
CAUTION
Some of the components are heavy! The person who performs the dismantling of
the system must have the necessary knowledge and skills to handle heavy
components to avoid the risk of accidents and injury from occurring.
• Load cell: These parts are made of structural steel, which can be recycled according to
local instructions. All the auxiliary equipment, such as cabling or hoses must be removed
before recycling the material.
1.3 Function and Design
1.3.1 General
A complete measuring system normally consists of two load cells, a junction box, one control unit
with two measurement channels and cabling.
6 3BSE023881R0101 en Rev I
SUMMATION A+B
INDIVIDUELL A
DIFFERENS A-B
INDIVIDUELL B
A
Sum A+B
Differential A-B
B
Load cells
Adapter plates
Junction box
Load cell cabling
Control unit
Output signals
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
1 Introduction
Figure 1. Complete Measuring System
1.3.2 Load Cells PFCL 201
The load cells are installed under the roll bearings, where they measure forces at right angles to the
mounting surface.
The reactive force from the strip, which is proportional to the strip tension, is transferred to the load
cells via the roll and the bearings.
The load cells are connected to the control unit via a junction box. The control unit converts the
load cell signals to DC voltages that are proportional to the reaction force. Depending on which
control unit is chosen, it is possible to have the analog signals for the two individual load cells (A
and B), the sum of the load cell signals (A+B), and/or the difference between the load cell signals
(A-B).
1.3.3
Principle of Measurement
The load cell only measures force in the direction FR. The measurement force may be positive or
negative. The load cell is normally installed under the roll bearings. When there is a strip in tension
over the roll, the tension (T) gives rise to two force components, one in the direction of measurement of the load cell (FR) and one at right angles (FV).
The measuring force depends on the relationship between the tension (T) and the wrap angle
formed by the strip around the measuring roll.
3BSE023881R0101 en Rev I 7
F
R
T
T
F
V
Wrap
angle
Wrap
angle
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
1 Introduction
Figure 2. Measuring Roll with Force Vectors
8 3BSE023881R0101 en Rev I
Measurement
direction
Mounting screw hole
Sensor
Connector
Mounting screw hole
Technology
Pressductor
R
Fixed cable connector
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Description
2
2.1 General
The load cell is machined from a single piece of stainless steel. The sensors are machined directly
in the piece of steel and are positioned so that they are sensitive to force in the direction of measurement and insensitive in other directions.
The load cell is mounted on a base with four screws, and the bearing housing is mounted on top
of the load cell with four screws.
Every load cell comes calibrated and temperature compensated.
The load cells PFCL 201C/201CE/201CD are available in four measurement ranges, all variants
have the same external dimensions.
The load cell PFCL 201C is equipped with a connector for the pluggable connection cable.
The load cell PFCL 201CE has a
The load cell PFCL 201CD is provided with an acid-proof cable gland with a xed PTFE- insulated
connection cable.
xed connection cable with protective hose.
Figure 3. Load Cell PFCL 201C
Figure 4. Load Cell PFCL 201CE with protective hose for cable
3BSE023881R0101 en Rev I 9
Figure 5. Load Cell PFCL 201CD with insulated cable connection
2.2 Technical Data
Table 1 Technical Data Load Cell PFCL 201
PFCL 201 Type Data Unit
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Nominal Loads
Nominal load in measuring direction, F
nom
Permitted transverse force within
the accuracy, F
1)
(for h = 300
Vnom
C/CD/CE 5 10 20 50 kN
2,5 5 10 25
mm)
Permitted axial load within the
accuracy, F
(for h = 300 mm)
Anom
Extended load in measuring direction with accuracy class ±1%, F
ext
1,25 2,5 5 12.5
7,5 15 30 75
Max permitted load
In the direction of measurement
without permanent change of data,
2)
F
max
In the transverse direction without
permanent change of data, F
Vmax
C/CD/CE 50 100 200
2
)
12,5 25 50 125
500
3)
kN
(for h = 300 mm)
Spring constant C/CD/CE 250 500 1000 2500 kN/mm
Mechanical data
Length C/CD/CE 450 mm
Width C 110
CD 138
CE 156
Height C/CD/CE 124,6
Weight 37 kg
10 3BSE023881R0101 en Rev I
Pressductor
System
h
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Material C/CD/CE Stainless steel SIS 2387 DIN X4CrNiMo 165
Accuracy
Accuracy class C/CD/CE ± 0,5 %
Linearity deviation < ± 0,3
Repeatability error < ± 0,05
Hysteresis <0,2
Compensated temperature range +20 - +80 °C
Zero point drift 50 ppm/K
Sensitivity drift 100
Working temperature range -10 - +90 °C
Zero point drift 100 ppm/K
Sensitivity drift 200
Storage temperature range -40 - +90 °C
1) Denitions of directions designations “V”and “A” in FV and
FA are given in Section 2.5.1 Coordinate System.
2) F
max
and F
are allowed at the same time.
Vmax
3) Max. permitted load for the load cell is 10 × F
overload capacity for the total installation may be limited by
the screws.
2.3 Denitions
Nominal load
nom
. The
h= Building Height
Nominal load, F
dimensioned to measure within the specied accuracy class. The load cell is calibrated up to F
, is the maximum load in the measurement direction for which the load cell is
nom
nom
.
Sensitivity
Sensitivity is dened as the difference in output values between nominal load and zero load.
3BSE023881R0101 en Rev I 11
Signal
Rated output value
at nominal load
Force
Sensitivity
F
nom
Signal
Force
F
nom
Signal
Force
F
nom
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Figure 6. Sensitivity
Accuracy and Accuracy Class
Accuracy class is dened as the maximum deviation, and is expressed as a percentage of the sensitivity at nominal load. This includes linearity deviation, hysteresis and repeatability error.
Linearity Deviation
Linearity deviation is the maximum deviation from a straight line drawn between the output values
at zero load and nominal load. Linearity deviation is related to the sensitivity.
Figure 7. Linearity Deviation
Hysteresis
Hysteresis is the maximum difference in the output signal at the same load during a cycle from zero
load to nominal load and back to zero load, related to the sensitivity at nominal load. The hysteresis
of a Pressductor transducer is proportional to the load cycle.
12 3BSE023881R0101 en Rev I
Figure 8. Hysteresis
Signal
Force
F
nom
Sensitivity
drift
Zero
point
drift
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Repeatability error
Repeatability error is dened as the maximum deviation between repeated readings under identical
conditions. It is expressed as a percentage of the sensitivity at nominal load.
Compensated temperature range
The temperature drifts of the load cell have been compensated for in certain temperature
ranges. That is the temperature range within which the
zero point and sensitivity drifts) of the load cell are maintained.
Working temperature range
Working temperature range is the temperature range within which the load cell can operate within
a specied accuracy. The maximum permitted temperature drifts (i.e. zero point and sensitivity
drifts) of the load cell are not necessarily maintained in the whole working temperature range.
specied permitted temperature drifts (i.e.
Storage temperature range
Storage temperature range is the temperature range within which the load cell can be stored.
Zero point drift with temperature
Zero point drift is
dened as the signal change with temperature, related to the sensitivity, when
there is zero load on the load cell.
Sensitivity drift with temperature
Sensitivity drift is
dened as the signal change with temperature at nominal load, related to the sen-
sitivity, excluding the zero point drift.
Figure 9. Sensitivity drift with temperature
Compression
Compression is the total reduction in the height of the load cell when the load is increased from
zero to the nominal value.
3BSE023881R0101 en Rev I 13
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2.4 Measuring principle of the sensor
The measuring principle of the sensor is based on the Pressductor® technology and the fact that
the permeability of a magnetic material changes under mechanical stress.
The sensor is a membrane machined in the load cell. Primary and secondary windings are wound
through four holes in the load cell so that they cross at right angles.
The primary winding is supplied with an alternating current which creates a magnetic eld around
the primary winding. Since the two windings are at right angles to each other, there will be no magnetic
eld around the secondary winding, as long as there is no load on the sensor.
When the sensor is subjected to a mechanical force in the direction of measurement, the propagation of the magnetic eld changes so that it surrounds the secondary winding, inducing an alternating voltage in that winding.
The control unit converts this alternating voltage into a DC voltage proportional to the applied
force. If the measurement force changes direction, the sensor signal changes also polarity.
2 Description
Figure 10. Propagation of magnetic eld around secondary winding due to mechanical force on sensor
2.5 Mounting Arrangement
When choosing a mounting arrangement it is important to remember to position the load cell in a
2.5.1
direction that gives
The load cell has no particular correct orientation; it is positioned in the orientation best suited for
the application, bearing in mind the positions of the screw holes. The load cell can also be installed
with the roll suspended under the load cell.
The load cell has the same sensitivity in both tension and compression, so the load cell can be
installed in the easiest manner.
Typical mounting arrangements are horizontal and inclined mounting.
Coordinate System
A coordinate system is dened for the load cell. This is used in force calculations to derive force
components in the load cell principal directions.
sufcient measuring force (FR) to achieve the highest possible accuracy.
14 3BSE023881R0101 en Rev I
R
V
V
R
A
A
R= Measuring direction
V= Transverse direction
A= Axial direction
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Where direction designations R, V and A are recognized as sufxes for force components, F, this
represents the force component in the respective direction. The sufx R may be omitted, when
measuring direction is implied by the context.
Figure 11. Coordinate system dening directions used in force calculations
2.5.2 Horizontal Mounting
In the majority of cases horizontal mounting is the most obvious and simplest solution. Stand,
mounting surface and shims (if required) are simple and cheap to make.
When calculating the force, the equations below must be used:
FR = T × (sin α + sin β)
FRT = Tare
F
= FR + FRT = T × (sin α + sin β) + Tare
Rtot
FV = T × (cos β - cos α)
FVT = 0
F
= FV + FVT = T × (cos β - cos α) + 0 = T × (cos β - cos α)
Vtot
where:
T = Strip tension
FR = Force component from strip tension in measurement direction, R
FRT = Force component from Tare in measurement direction, R
F
= Total force in measurement direction, R
Rtot
FV = Force component from strip tension in transverse direction, V
FVT = Force component from Tare in transverse direction, V
F
= Total force in transverse direction, V
Vtot
Tare = Force due to tare weight
α =
Deection angle on one side of the roll relative the horizontal plane
β = Deection angle on the other side of the roll relative the horizontal plane
3BSE023881R0101 en Rev I 15
Figure 12. Horizontal mounting
2.5.3 Inclined Mounting
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Inclined mounting means arrangements in which the load cell is inclined relative to the horizontal
plane. In some cases this is the only option.
When calculating the force, the equations below must be used:
FR = T × [sin (α - γ) + sin (β + γ)]
FRT = Tare × cos γ
F
= FR + FRT = T × [sin (α - γ) + sin (β + γ)] + Tare × cos γ
Rtot
FV = T × [cos (β + γ) - cos (α - γ)]
FVT = - Tare × sin γ
F
= FV + FVT = T × [cos (β + γ) - cos (α - γ)] - Tare × sin γ
Vtot
γ = 90° - φ
where:
T = Strip tension
FR = Force component from strip tension in measurement direction, R
FRT = Force component from Tare in measurement direction, R
F
= Total force in measurement direction, R
Rtot
FV = Force component from strip tension in transverse direction, V
FVT = Force component from Tare in transverse direction, V
F
= Total force in transverse direction, V
Vtot
Tare = Force due to tare weight
α =
Deection angle on one side of the roll relative the horizontal plane
β =
Deection angle on the other side of the roll relative the horizontal plane
φ= Angle for measurement direction relative the horizontal plane
γ = Angle for load cell mounting surface relative the horizontal plane
16 3BSE023881R0101 en Rev I
F
V
T
are
F
R
T
γ
β
α
T
γ
φ
(signal)
Secondary
circuit
Primary
circuit
C
D
A
B
T
0.5 A/330 Hz
R
1
R
2
Secondary circuit
(signal)
(supply current)
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
2 Description
Figure 13. Inclined mounting
2.6 The Electrical Circuit
The electrical circuit of the load cell is shown in the diagram below.
Figure 14. Load cell circuit diagram
The load cell is supplied with a 0.5 A, 330 Hz alternating current. The secondary signal is calibrated
for the correct sensitivity with a voltage divider R1 - R2, and temperature compensation is provided
by thermistors T.
All impedances on the secondary side are relatively low. The output impedance is typically 9-12 Ω ,
which helps to suppress interference.
3BSE023881R0101 en Rev I 17
Installation
3
3.1 General
The equipment is a precision instrument which, although intended for severe operating conditions,
must be handled with care. The load cells should not be unpacked until it is time for installation.
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
3 Installation
To achieve the
must be installed in accordance with the instructions below. See also 6.4 Fault Tracing in the
Mechanical Installation.
• The foundation for the load cell must be made as stable as possible. A resilient stand lowers
the critical frequency of the measuring roll and bearing arrangement.
• The surfaces closest to the load cell, and other surfaces that affect the t, must be machined
at to within 0.05 mm.
• There must not be any shims immediately above or below the load cell, as this may
adversely affect the atness. Instead, shims may be placed between the adapter plate and
the foundation or between the adapter plate and the bearing housing.
• The screws that secure the load cell must be tightened with a torque wrench.
• The bearing arrangement for the measuring roll must be designed to allow axial expansion of
the roll with changes in temperature.
• Any drive to the roll must be applied in such a way that interfering forces from the drive are
kept to a minimum.
• The measuring roll must be dynamically balanced.
• The mounting surfaces of the load cells must be on the same height and parallel with the
measuring roll.
• In a corrosive environment, galvanic corrosion may occur between the load cell,
galvanized screws and adapter plates. This makes it necessary to use stainless steel screws
and adapter plates of stainless steel or equivalent. See adapter plates in
A Drawings.
specied accuracy, the best possible reliability and long-term stability, the load cells
3.2 Unpacking
When the equipment arrives, check against the delivery document. Inform ABB of any complaint,
so that errors can be corrected immediately and delays avoided.
3.3 Preparations
Prepare the installation in good time by checking that the necessary documents and material are
available, as follows:
• Installation drawings and this manual.
• Standard tools, torque wrench and instruments.
• Rust protection, if additional protection is to be given to machined surfaces. Choose TECTYL 511 (Valvoline) or FERRYL (104), for example.
• Load cells, adapter plates, bearing housings, etc.
18 3BSE023881R0101 en Rev I
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
3 Installation
• Locking uid (medium strength) to lock mounting screws.
• Screws as listed in Table 2. page 19 and Table 3. page 19 to secure the load cell, and
other screws for bearing housings etc.
3.4 Mounting
The instructions below apply to a typical mounting arrangement. Variations may be allowed, provided that the requirements of 3.1 General are complied with.
1. Clean the foundation and other mounting surfaces.
2. Fit the lower adapter plate to the load cell. Tighten the screws to the torque stated in Table 2.
page 19 or Table 3. page 19.
3. Fit the load cell and the lower adapter plate to the foundation, but do not fully tighten the
screws.
4. Fit the upper adapter plate to the load cell, tighten to the torque stated in Table 2. page 19 or
Table 3. page 19.
5. Fit the bearing housing and the roll to the upper adapter plate, but do not fully tighten the
screws.
6. Adjust the load cells so that they are in parallel with each other and in line with the axial direction
of the roll. Torque tighten the foundation screws.
7. Adjust the roll so that it is at right angles to the longitudinal direction of the load cells.Torque
tighten the screws in the upper adapter plate.
8. Apply rust protection to any machined surfaces that are not rust proof.
Table 2 Galvanized MoS2 lubricated Screws according to ISO 898/1
Strength class
(1)
8.8
(12.9)
Table 3 Waxed Screws of Stainless Steel According to ISO 3506
Strength class
(1)
A2-80
(1) Strength class 12.9 is recommended for 50 kN load cells, when large overloads are expected, especially
if the mounting screws are subjected to tension.
Dimension Tightening torque
M16 170 (286) Nm
Dimension Tightening torque
M16 187 Nm
3BSE023881R0101 en Rev I 19
Pressductor
System
Bearing housing
Load cell
Roll
Upper adapter plate
Lower adapter plate
Foundation
Technology
Pressductor
R
Figure 15. Typical installation
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
3 Installation
3.5 Cabling for Load Cell PFCL 201CE
Cabling with protective hose shall be mounted so that the forces related to the weight of the cable/
hose do not act in the measuring direction of the load cell. A cable clamp is therefore necessary. If
the load cell is prevented from movement in the measuring direction- it will shunt force, and the
measured force will differ from the actual.
The favourable direction of the cable/hose is the horizontal direction to the left or right as indicated
in Figure 16. Position of cable from factory page 20. This as possible forces in the longitudinal
direction of the cable/hose due to temperature, will act perpendicular to the measuring direction of
the load cell (the direction in which the load cell is insensitive to loads).
For achievable cable directions, see Figure 17. Possible directions of cable for PFCL 201CE page
21.
The direction of the cable and protective hose can be changed by unscrewing the two screws in
the connection box and turning the cable to a suitable direction. Make sure to re-install the screws
in the connection box.
20 3BSE023881R0101 en Rev I
Figure 16. Position of cable from factory
Technology
Pressductor
R
Pressductor
Technology
R
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
3 Installation
Figure 17. Possible directions of cable for PFCL 201CE
CAUTION
Cable bending is not allowed in the connection
Figure 18. Cable bending, wrong installation
3BSE023881R0101 en Rev I 21
Commissioning
4
4.1 General
The actual procedure for commissioning a load cell is simple, provided that the load cells and
cables have been properly installed. Commissioning of the control unit is described in the relevant
chapter of the control unit manual.
Check the following:
• that the load cells have been correctly installed and aligned
• that all screws have been tightened to the correct torque
• that all cables are correctly installed and connected
• that all connectors are plugged in
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
4 Commissioning
4.2 Preparatory Calculations
To be able to set the correct measuring range, the measurement force per load cell FR/2 at maximum tension T must be calculated. Each load cell is subjected to half the total measurement force
FR. This calculation must be done before commissioning can begin. Calculation of FR is described
in 2.5 Mounting Arrangement.
22 3BSE023881R0101 en Rev I
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
5 Maintenance
Maintenance
5
5.1 General
Strip Tensiometer Systems with Pressductor® load cells are extremely reliable and do not require
daily servicing. As a preventive measure, checks should be done periodically on all parts subject to
mechanical wear.
5.2 Preventive Maintenance
Check mounting screws and tighten if necessary.
The gaps between load cell and plates should be checked to ensure that they do not get clogged
with dirt, causing shunt force past the load cell. Clean the gaps with compressed air if necessary.
The cable between the load cell and the junction box is subjected to possible damage and should
be checked and replaced if necessary.
5.3 Spare Parts
Users are recommended to keep the following spare parts in stock:
• One load cell of correct type and size.
• One connector complete with cable (for PFCL 201C)
Table 4 Ordering numbers for Load Cell PFCL 201
Description
Load cell Load cell PFCL 201C 5,0 3BSE027070R5
Load cell Load cell PFCL 201C 10,0 3BSE027070R10
Load cell Load cell PFCL 201C 20,0 3BSE027070R20
Type Nominal load
(kN)
Ordering numbers
Load cell Load cell PFCL 201C 50,0 3BSE027070R50
Load cell Load cell PFCL 201CE 5,0 3BSE027062R5
Load cell Load cell PFCL 201CE 10,0 3BSE027062R10
Load cell Load cell PFCL 201CE 20,0 3BSE027062R20
Load cell Load cell PFCL 201CE 50,0 3BSE027062R50
Load cell Load cell PFCL 201CD 5,0 3BSE029774R5
3BSE023881R0101 en Rev I 23
Load cell Load cell PFCL 201CD 10,0 3BSE029774R10
Load cell Load cell PFCL 201CD 20,0 3BSE029774R20
Load cell Load cell PFCL 201CD 50,0 3BSE029774R50
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
5 Maintenance
24 3BSE023881R0101 en Rev I
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
6 Fault Tracing
Fault Tracing
6
6.1 General
It is important to be thoroughly familiar with the description of operation in
2 Description before starting fault tracing.
6.2 Interchangeability
The load cells are factory calibrated and can be replaced directly with another load cell of the same
type. The only adjustment required after load cell replacement is zero adjustment in the control
unit.
6.3 Fault Tracing Procedure
The measuring equipment can be divided into four parts:
• The mechanical installation.
• The load cell.
• The junction boxes and the cabling.
• The control unit (see the control unit manual).
The fault symptoms indicate in which part the fault lies.
• Faults in the mechanical installation often result in an unstable zero point or incorrect sensitivity.
If a fault follows something else in the process, such as temperature, or can be linked
to a particular operation, it probably originates from something in the mechanical installation.
• Load cells are extremely robust and can withstand ten times their nominal load in the measuring direction. If a load cell has nevertheless been so overloaded that its data have been
altered, this is probably due to an event in the mill, such as strip breakage. On excessive
overload the
• Problems such as interference or unstable zero point may be caused by wiring faults. Some
malfunctions may be due to the proximity of cables that cause interference. Incorrect installation, such as imbalance in a cable or screens earthed at more than one end may cause the
zero point to become unstable. Cables are subject to mechanical wear, and should be
checked regularly. The junction box should also be checked, especially if it is subject to
vibration.
rst thing that happens is that the zero point shifts.
• A fault in the control unit usually causes intermittent loss of a function. It is unusual for the
control unit to cause stability problems. Faults in connected units may affect the operation of
the control unit. For further details see the control unit manual.
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6.4 Fault Tracing in the Mechanical Installation
There are a number of parts in the mechanical arrangement that can cause faults. The extent to
which these faults are repeatable differs. Possible causes fall into the following groups.
• Defective mounting surface, stand or adapter plates.
• Force shunting.
• Insufcient mounting of load cell and adapter plates.
• Rolls and bearings.
• Driven roll.
6.4.1 Defective Mounting Surface, Support or Adapter Plates
An unmachined or poorly machined mounting surface, which is uneven, may cause bending or
twisting of the load cell. This may result in instability of the zero point.
6 Fault Tracing
6.4.2 Force Shunting
Force shunting means that some of the force is diverted past the load cell. This may be caused by
some kind of obstruction to the force through the load cell. The connecting cables, for example,
have been incorrectly installed and are preventing movement. Another possible cause is that the
roll is not free to move in the direction of measurement, possibly because something is mounted
too close to a bearing housing, or because an object has worked loose and become trapped
between the bearing housing and adjacent parts.
Force shunting causes the strip tension indication to be lower than the actual strip tension.
6.4.3
6.4.4
Fastening of Load cell and Adapter Plates
Screw joints that have not been properly tightened or have lost their pre-tightening force, cause
sliding at the mating surfaces. Fastening of the load cell is especially critical. If a load cell is not
properly secured, the zero point will be unstable. Sliding between other surfaces may cause the
same symptoms.
Rolls and Bearings
An incorrectly designed bearing arrangement may give rise to high axial forces. The roll should be
xed at one end and free at the other.
If both ends are
rising temperature.
Even a correctly designed bearing arrangement may deteriorate with time; bearings become worn,
and so on. This may give similar symptoms, such as slow zero point drift between cold and hot
machine, or sudden jumps in the signal.
xed, there will be a high axial (thrust) force due to expansion of the shaft with
6.4.5
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Driven Roll
A source of error that is seldom suspected is the roll itself. The effect is especially critical when
measuring forces on the load cell are relatively low. Long drive shafts with their associated universal
joints may cause unstable signals if they are not properly maintained. It is important to lubricate
universal joints. Longitudinal expansion of the drive shaft should also be taken into account. Since
Load cell A
Load cell B
Junction box
Control unit
C
D
A
B
C
D
A
B
3
2
4
1
3
2
4
1
Blue
Black
White
Red
Blue
Black
White
Red
Pressductor PillowBlock Load Cells, Vertical Measuring PFCL 201, User Manual
6 Fault Tracing
such expansion is often taken up by splines, these must also be lubricated. The symptoms are
instability of the signal, for instance jumps in the signal during slow running.
6.5 Fault Tracing of Load Cells, Junction Boxes and wiring
The load cell is very robust and can withstand high overloads. The data of a Pressductor load cell
does not change slowly, but in steps, usually in connection with an event in the mill. Excessive
overloading usually results in permanent shifting of the zero point.
Poor contact in the junction box causes intermittent faults. Both sensitivity and zero point may vary.
Check all screw terminals. Do not use pins crimped to the connecting wires, as these often work
loose after a time.
The cabling, especially the cable to the load cell, is the part that is most exposed to damage.
Since the resistance of the load cell windings is low, it is easy to check the load cells and cabling
from the control unit.
Typical readings are 2 Ω for the resistance of the primary winding and 9-12 Ω
for the output impedance of the secondary winding.
Insulation faults in the cabling or the load cell may cause incorrect sensitivity or unstable zero point.
When the load cell circuits have been isolated from earth and from the control unit at the disconnectable terminals, it is easy to measure the insulation from the control unit.
If the cables are not routed correctly, they may pick up interference from other cables.
Figure 19. Typical load cell cabling
For circuit diagram applications, see the manual for the applicable control unit:
Millmate Strip Tension Systems with Millmate Controller 400, 3BSE023139Rxxxx
Web Tension Systems with Tension Electronics PFEA 111/112, 3BSE029380Rxxxx
Web Tension Systems with Tension Electronics PFEA 113, 3BSE029382Rxxxx
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Appendix A Drawings
Drawings
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Appendix A Drawings
A.1 Load Cell PFCL 201C, Dimension Drawing
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A.2 Load Cell PFCL 201CE, Dimension Drawing
Appendix A Drawings
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Appendix A Drawings
A.3 Load Cell PFCL 201CD, Dimension Drawing
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A.4 Adapter Plate Upper PFCL 201, Dimension
Drawing
Appendix A Drawings
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Appendix A Drawings
A.5 Adapter Plate Lower PFCL 201, Dimension
Drawing
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Alphabetical index
accuracy and accuracy class ........................................... 12
compensated temperature range .................................... 13
hysteresis ........................................................................ 12
linearity deviation ............................................................. 12
nominal load .................................................................... 11
repeatability error ............................................................. 13
sensitivity ......................................................................... 11
sensitivity drift .................................................................. 13
with temperature ............................................................. 13
working temperature range .............................................. 13
zero point drift ................................................................. 13
Alphabetical index
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—
ABB AB
Industrial Automation
Measurement & Analytics
Force Measurement
SE-721 59 Västerås Sweden
Tel: +46 21 32 50 00
Internet: www.abb.com/striptension
3BSE023881R0101 en Rev I
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