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Second Edition 03/18/1997 – CSH  (con:K2AA V1.0)  031-300-190014_A.doc 

 

 

LOAD MOMENT INDICATOR

 

 

 

 

DS 50 / 0002

 

 

OPERATOR'S MANUAL 

 

MANITOWOC BOOM TRUCKS, INC. 

 

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Second Edition 03/18/1997 – CSH  (con:K2AA V1.0)  031-300-190014_A.doc 

 
 

NOTICE 

 
 

The information in this document is subject to change without notice. 

 

PAT does not assume any warranty of any kind with regard to this material, including, but not 

limited to the implied warranties of marketability and fitness for a particular purpose. 

 

PAT shall not be liable for errors contained herein or for incidental or consequential damages in 

connection with the furnishing, performance or use of this manual.  

 

This document contains proprietary information, which is protected by copyright. All rights 

reserved.  

 

No part of this document may be photocopied, reproduced, or translated to another language 

without the prior written consent of PAT.

 

 
 

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Second Edition 03/18/1997 – CSH  (con:K2AA V1.0)  031-300-190014_A.doc 

 

TABLE OF CONTENTS 

 
 

 

General Information 

 

 

 

 

 

 

 

 

 

  2 

 
 

2 Warnings 

 

 
 

System Description  

3.1 System 

Function 

3.2 Control 

Identification 

 
 

4 Pre-Operational 

Inspection 

4.1 

Anti two-block devices 

4.2 

Pre- Operation Inspection and Calibration Verification 

10 

 
 

5 System 

Operation 

12 

5.1 

Operating Mode Selection 

12 

5.2 

Selection of the Reeving 

13 

5.3 Data 

Display 

14 

5.4 Error 

Display 

15 

5.5 

System and Display test 

15 

 
 

Service and Maintenance 

 15 

 
 

7 Troubleshooting 

16 

 
 
 
 
 
 
 

 

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Operator's Manual   

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1 GENERAL INFORMATION 

 
The PAT Load Moment Indicator

1

 (LMI) DS 50 has been designed to provide the crane operator with the 

essential information required to enable the machine to be used within its design parameters. 
 
Using different sensing devices, the Load Moment Indicator monitors various crane functions and provides 
the operator with a continuous reading of the capacity of the crane. The readings continuously change as 
the crane moves through the motions needed to make the lift. 
 
The LMI provides the operator with information regarding the length and angle of the boom, working 
radius, rated load and the total calculated weight being lifted by the crane.  
 
If non-permitted conditions are approached, the DS 50 Load Moment Indicator will warn the operator by 
sounding an audible alarm and lighting a warning light.

 

 
 
 

 

 

Always refer to operational instructions and load charts provided by the crane manufacturer for 
specific crane operation and load limits.

 

2 WARNINGS 

 
The LMI is an operational aid that warns a crane operator of approaching overload conditions and warns of 
overhoist conditions which could cause damage to equipment and personnel. 
 
The device is not, and shall not be, a substitute for good operator judgment, experience and use of 
accepted safe crane operating procedures. 
 
The responsibility for the safe crane operation shall remain with the crane operator who shall ensure that 
all warnings and instructions supplied are fully understood and observed. 
 
Prior to operating the crane, the operator must carefully and thoroughly read and understand the 
information in this manual to ensure that he knows the operation and limitations of indicator and crane. 
 
Proper functioning depends upon proper daily inspection and observance of the operating instructions set 
forth in this manual. We draw your attention to section 5 of this manual. 

                                                

1

 

LOAD MOMENT: generally, the product of a force and its moment arm; specifically, the product of the load and the load-radius. Used in the 

determination of the lifting capacity of a crane.

 

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The LMI can only work correctly, if all adjustments have been properly set. For correct 
adjustment, the operator has to set the operating code and the parts of line (reeving) thoroughly 
and correctly in accordance with the real rigging state of the crane. To prevent material damage 
and serious or even fatal accidents, the correct adjustment of the LMI has to be ensured before 
starting the crane operation

 

3 SYSTEM DESCRIPTION 

 
The PAT Load Moment Indicator DS 50 consists of a central micro processor unit with build in length- and 
angle sensor, operating console, pressure transducers, and anti-two block switch(es). 
 
The system operates on the principle of reference/real comparison. The real value, resulting from the 
pressure measurement is compared with the reference data, stored in the central processor memory and 
evaluated in the microprocessor. When limits are reached, an overload-warning signal is generated at the 
operator’s console. 
 
The fixed data regarding the crane, such as capacity charts, boom weights, centers of gravity and 
dimensions are stored in memory chips in the central processor unit. This data is the reference information 
used to calculate the operating conditions.  
 
The length/angle sensor mounted inside the cable reel, which is mounted on the boom registers boom 
length and boom angle. The boom length is measured by the cable reel cable, which also serves as an 
electrical conductor for the anti two-block switches. 
 
Pressure transducers attached to the piston and rod sides of the hoist cylinder measure the crane load. 
 
The console has two functions:  
•  displays information to the operator 

•  input terminal for operating mode and reeving (parts of line) 

 
The operator’s console is mounted in the operator’s field of vision. For a better identification of displays 
and operating elements, they are continuously backlit during operation. 
 

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 DS 50 / 0002 

Fig. 1: Components of the LMI system PAT DS 50 
 

 

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3.1 System Function 

 

 

Upon switching on, the system starts with an 
automatic test of the LMI system, of lamps 
and audible alarm.  

During the test, the LC display shows 

8:88.8.8

 

 

First, the operating mode is determined by 
input of the operating code number 

 

 

System awaits acknowledgment 

 

 

 

 

Next is the selection of the reeving 

 

 

System awaits acknowledgment 

 

 

 

 

Upon acknowledgment of the inputs, the 
system is ready for operation. 

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 DS 50 / 0002 

3.2 Control Identification 

 
This unit contains a display and different controls that are described as follows: 
 
 
Fig. 2: Operating Console 
 

 

 
 

1  LC Display 
2  Load Moment Limit Light 
3  Load Moment Prewarning Light 
4  Alarm Light “Anti-Two-Block” 
5  Button “UP” 
6  Button “DOWN” 
7  Button and Control Light “OK” 
8  Button and Control Light “SELECT OPERATION CODE” 
9  Button and Control Light “SELECT REEVING” 

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 LC-Display 

 

 

The LC Display has five digits. The 
readout depends on the operating modus 
and the operator’s selection.  
Please refer to section 4, Operation of the 
system. 

 

  Load Moment Limit Light 

 

 

The red LOAD MOMENT LIMIT LIGHT (2) warns the 
operator that a rated load condition has been 
reached. It lights up when the load on the crane 
reaches the crane load capacity. The audible alarm 
also sounds when this condition has been reached. 

 

  Load Moment Prewarning Light 

 

 

 

The yellow LOAD MOMENT PRE-WARNING LIGHT 
(3) will light up when the load on the crane reaches 
the defined prewarning area, thus indicating that an 
overload condition is approaching. 
This means for the operator to continue his crane 
operation with extreme caution.
 

 

  Alarm Light “Anti-2-Block” 

 

 

The red “Anti Two-Block Alarm Light” (4) lights up 
when the anti-two-block limit switch contacts open, 
indicating that a two-blocking condition is 
approaching. At the same time, the audible alarm will 
sound, and the telescope out and winch up functions 
are locked out. If machine is equipped with an 
overload shut-off, the boom down function is also 
locked out. 

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 Cursor 

"up" 

 

 

Key for the stepwise increase of the displayed value: 
•  when selecting the operation code 

•  when selecting the reeving 

•  when selecting the geometry data 

(

➭ refer to chapter 5.3) 

 

 

 Cursor 

"down" 

 

 

Key for the stepwise decrease of the displayed value: 
•  when selecting the operation code 

•  when selecting the reeving 

•  when selecting the geometry data 

(

➭ refer to chapter 5.3) 

 

 

 Button 

“OK” 

 

 

Key for acknowledgment of an error message. 

 

 

 
The correct setting of the operation mode and the reeving is of utmost importance for 
the proper function of the system and the crane. Therefore, only operators who are 
thoroughly familiar with use and operation of the system shall set the following buttons: 

 

  Button " set operating mode" 

 

 

Button to start the function "set operating mode ". 
For the proceeding, please refer to 

 

➭ chapter 5.1. 

 

  Button "set reeving" 

 

 

Button to start the function "set reeving" (parts of 
line). 
For the proceeding, please refer to 

 

➭ chapter 5.2. 

 

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4 Pre-Operational Inspection 

 
Prior to operating the crane, the following electrical connections must be checked to ensure that the 
system is properly connected for the crane configuration. 

4.1  Anti two-block devices

 

 

 
If the crane works only with the main boom and without boom extension, check the weight to ensure it is 
attached to the anti two-block switch on the main hoist load line.  
 
Weight installation - The hoist line runs through the A2B weight. With even parts of hoisting line, the weight 
shall be attached to the dead-end line. With odd parts of hoisting line, the weight shall be attached to the 
line of lowest speed. 
 
If an extension exists, install the connecting cables between the boom extension junction box and the 
boom point junction box. Remove the weight from the main boom anti-two block switch and re-attach it to 
the boom extension anti-two block switch on the auxiliary hoist line.   
 

  

 

Failure to position the anti two-block switch weight will prevent the overhoist system from functioning 
properly. No weight shall be on the main hoist anti two-block switch when the boom extension is being 
used. 

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4.2   Pre-Operation Inspection and Calibration Verification 

 
After the electrical connections have been checked to insure that the system is properly connected for the 
crane configuration, the following checks shall be made: 
 
1.  Check the electrical wiring connecting the various parts of the system for physical damage. 
2.  Check the anti two-block switches and weights for free movement. 
3.  Check the spring-loaded cable reel to be sure it is free to rotate, has tension and the cable is reeled 

properly. 

 

 

 
The following tests shall be performed with care to prevent damage to the machine or injury to 

personnel. Proper functioning of the system requires successful completion of these tests 
before operating the machine. 

 
4.  Check the anti two-block alarm light (4) and the audible alarm by performing one of the following tests 

a, b, or c. If the crane is equipped with a boom extension, perform the test procedure on both the main 
boom and boom extension anti two-block switches. 

 
When checking system the operator must use caution. If the operator cannot see the load-handling device 
approaching the boom nose, he/she shall have an assistant (signal person) watch the load handling 
device. The operator shall be prepared to stop the machine immediately should the LMI system not 
function properly. Proper operation will be indicated by: 
•  lighting the red warning light (4) 

•  sounding the audible alarm 

•  locking out of the hoist up and  telescope out functions 

•  and if the overload shutoff option is installed, a lockout of the boom down function will occur 

 
a) By manually lifting the weight attached to the anti two-block switches. When the weight is lifted, the 

audible alarm should sound, the anti two-block alarm light (4) should light. 

b)  Slowly raise the main boom load-handling device to create a potential two-block condition. When the 

load-handling device lifts the weight, the audible alarm should sound, the anti two- block alarm light (4) 
should light and the motion of the load handling device should be stopped. Lower the load-handling 
device slightly or telescope the boom in to eliminate this condition. 

c)  Slowly extend (telescope) the boom to create a potential two-block condition. When the load-handling 

device lifts the weight, the audible alarm (17) should sound, the anti two-block alarm light (24) should 
light and the boom telescope out function should be stopped. Lower the load-handling device slightly or 
telescope the boom in to eliminate this condition. 

 
NOTE: If the crane is equipped with the overload shutoff option, a two-block condition will also lockout the 
boom down function. If operating properly, the lockout feature will always permit operation of the hoist 
down, telescope in, and boom up functions. 
 

 

 

If the light and audible alarm do not function as described and the crane movements are not 
stopped, the system is not working properly. The malfunction shall be corrected before 
operating the crane.

 

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11 

 
5.  Check that the display of the main boom length agrees with the actual boom length. 
6.  Check that the display of the main boom angle agrees with the actual boom angles. 
7.  Check that the display of the operating radius of the crane agrees with the actual radius. 
8.  Check the load display by lifting a load of known weight. The accuracy of the load indication shall be 

within the tolerance of SAE J159. 

 
After being properly checked, the LMI is operational. The operator shall be thoroughly familiar with all 
controls of the LMI before operating the crane (see Section 3.2). Lifting a load of known weight and 
comparing the load to the information displayed on the LMI (see Section 5.2) shall check the proper 
function of the system. 
 
Rated loads include the weight of the hook block, slings, and auxiliary load handling devices. Their 
combined weights shall be subtracted from the listed load capacities as stated on the load capacity chart to 
obtain the net load to be lifted. 
 
 

 

 

If any of the displays reflects a deviation between displayed and actual values, an authorized 
PAT service representative shall be called for repair of the system and/or verification of the 
crane’s LMI calibration. 

 
 
 

 

 
Any structural modifications or changes to the crane shall require verification of the 
LMI calibration of the crane.

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5 SYSTEM OPERATION 

 
The LMI System DS 50 allows the operator to assess and evaluate the lift to meet the manufacturer 
specified load charts for the crane. 
 

 

 
The correct setting is of utmost importance for the proper functioning of the system and the 
crane. Therefore, the crane must not be operated without setting the appropriate operating 
code.

 

 
 

5.1  Operating Mode Selection 

 
 

 
 
  start function: 

(automatically after system start) 
 
•  Manually at each modification of the crane 

configuration by pressing key, 

 

The operating mode key and the cursor keys 
light up. The operating mode selection is 
displayed: 
 

 

 
XX= present operating code 

 

  

select mode:

 

•  use cursor keys 

 and 

 to modify 

the operating code 

 
 

 

confirm 

selection:

 

•  By pressing again, key 

 

The cursor keys and the operating selection 
key go out. 
 
NOTE: If the system is turned off, all 
adjustments remain stored. When the system 
is turned back on, the adjustments can be 

acknowledged by merely pressing key:

  

(if the crane configuration has not been 
modified!). 

 

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5.2  Selection of the Reeving (parts of line) 

 
 

 
 
 

  start function: 

(automatically after finishing operation mode 
selection) 
 
manually upon modification of the reeving by 

pressing key 

 

 

 

The reeving key and the cursor keys light up. The 
reeving selection is displayed: 
 

 

 
XX= present reeving 
 

 

select 

reeving:

 

•  use cursor keys 

 and 

 to modify 

the reeving 

 
 
 

 

confirm 

selection:

 

By pressing again, key 

 

The cursor keys and the reeving key go out. 
 
 

 

NOTE: If the system is turned off, all adjustments remain stored. When turning on again the system these 

adjustments can be acknowledged by merely pressing keys:

 

 and then 

  

Verify the operating mode and reeving displayed with the configuration of the crane.

 

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5.3 Data Display 

 
In case neither the operating mode selection nor the reeving selection are active, the LC display serves as 
data display: 
 

 

 

Press keys 

 and 

 to select the values. There are 9 display positions: 

 

Display Position 

Y 

Displayed Value 

XXXX 

0 error 

message 

main boom length 

main boom angle 

3 radius 

utilization in % 

5 tip 

height 

6 capacity 
7 actual 

load 

8 load 

moment 

 

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5.4 Error Display 

 
In case of operating error or system malfunction an error code is displayed. (for detailed information refer 
to chapter 7 troubleshooting) 
Error messages are given priority on the display: 
 

 XX=error 

code

 

 

Press key 

 to acknowledge an error message (exception: console error messages) 

 
 
 

5.5  System and Display Test 

 

Press keys 

 and 

 simultaneously to select the test function. 

All lamps light up, the buzzer is turned on and the following is displayed: 

 
 

 

 

 

 
 
During the test, the data transmission to the central unit is interrupted so that 2 seconds later approx. the 
cutoff relay is de-energized. 

6  SERVICE AND MAINTENANCE 

 
Daily maintenance of the load moment indicator consists of inspecting: 
 
•  The electrical wiring connecting the various parts of the system.  

If electrical wiring is damaged, it shall be replaced immediately. 
 

•  If the insulation is worn on the length sensor cable or cable guides are damaged, these parts shall be 

replaced. 
 

•  Check the anti two-block limit switches for freedom of movement. 

 

•  The cable reel shall be under tension to operate properly. 

 

•  Check the pressure transducers at the hoist cylinder and the connecting hoses for oil leakage. 

 
 
Other than correcting the problems identified in the Malfunctions Table and replacing faulty mechanical 
parts and cables, no other repairs shall be performed by non-expert personnel. 

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7 TROUBLESHOOTING 

 

General 

 
In case of a malfunction of the system, the display (1) will indicate a code that identifies the system 
malfunction. 
 
The error codes listed in the Malfunction Table will identify various faults that can occur with the LMI. 
Following the Malfunction Table are pages that explain each fault and describe the action that shall be 
taken to correct the fault. 
 
Faults within the electronic microprocessor shall be repaired by factory trained service personnel. When 
these faults occur, the competent service organization shall be contacted. 
 
 

Malfunction Table 

 

Error Code  Error  

E01 

Fallen below the radius or above angle range 

E02 

Radius range exceeded or fallen below angle 
range 

E03 

Boom position is out of the permissible working 
area 

E04 

Operating mode not existing 

E05 

Prohibited length range 

 

NOTE: 

If there is any Error Code displayed on the console which is not listed in the Malfunctions Table 
you shall call the Local Distributor. 
 

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Operating Errors 

 
Malfunctions in the system that are caused by range exceeding or operating errors by the crane operator 
himself are indicated on the display. These error codes are E01, E02, E03, E04, and the crane operator 
himself can normally eliminate E05 and them. 
 

Error 

Code 

Cause Elimination 

 

E01 

Fallen below the minimum 
radius or above the angle given 
in the load capacity chart due to 
luffing up the boom too far. 

Luff down boom to a radius or 
angle given in the load capacity 
chart. 

 

E02 

The maximum radius or 
minimum angle given in the load 
capacity chart was exceeded 
due to luffing down the boom 
too far. 

Luff up boom to a radius or 
angle given in the load capacity 
chart. 

 

E03 

Boom position is out of the 
permissible working area (over 
front). 

Move boom back to the 
permissible working area. See 
lifting diagram in the load 
capacity charts. 

 
 
 

E04 

Operating mode at the console 
incorrectly set. 

Correctly set operating mode to 
the code assigned to the 
operating mode of the crane. 
 

 

Operating mode is not 
permissible with the actual 
crane configuration or boom 
position 

Be sure crane is set up 
according to proper operating 
configurations. 

 
 
 
 
 

E05 

Boom was telescoped too far or 
not far enough, you may only 
operate up to a certain 
maximum or minimum boom 
length or with load curves for 
boom extension where you have 
to telescope the main boom to a 
certain length. 
 

Telescope boom to correct 
length, given in the load 
capacity chart. 

 

Length sensor adjustment 
changed i.e. length sensor cable 
slid off the length sensor drum. 

For elimination, refer to service 
manual. 

 


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