FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Non-Contact Seam Tracking cum Data Logging System"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: Larsen & Toubro Limited
L&T House, Ballard Estate, MUMBAI-400001, Maharashtra State, INDIA
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification
particularly describes the invention and
the manner in which it is to be
performed.

Non-Contact Seam Tracking cum Data Logging System
Field of invention
Present invention relates to welding process monitoring and seam tracking system. Background and prior art for the invention
Outer body of process plant equipments, used in refineries, fertilizer and power plants, is made by joining two or more cylindrical metallic shells. These shells are welded together at seam (Line of joint) by using Submerge Arc Welding (SAW) process. The shells are rotated continuously using a tank-rotator and welding is done from the top keeping a welding torch stationary over the seam. As the shell is rotated, the position of seam may get shifted axially (horizontal direction) due to drift in the job and radially (vertical direction) due to ovality in shells. The position of welding torch needs to be corrected with respect to the seam position for maintaining good welding bead finish. The deviation in position can be sensed using contact-type or non-contact type sensors.
Contact-type sensors need to be mounted ahead of the welding torch and hence it can not give feedback from exact weld position. Secondly, the feedback from contact type sensors get affected by quality of the surface it is tracking. Also, those sensors are prone to maintenance related problems due to wear & tear. It is very difficult to mount them for ultra narrow groove welding. In contact type seam tracking system, there is no possibility for data logging and automatic bead sequencing.
Object of the invention
Object of the invention is to track the seam during circ-seam welding, which is required to maintain correct position of the welding torch for better welding bead

finish, to get weld visual display for monitoring, to have welding related data logging and automatic bead sequencing
Statement of the invention
According to the present invention there is provided a non-contact seam tracking cum data logging system, the system comprising;
a non contact type sensor for sensing position of a welding torch;
a laser displacement sensor mounting on cross-siides;
a software algorithms for correcting the welding torch position according to the non contact type sensor and the laser displacement sensor feedback with an accuracy in the range of 0.3 to 0.7mm;
an analog I/O module for measuring the instantaneous values of welding related parameters, such as like welding current, welding voltage, welding temperature and surface speed;
a computer based system for recording and storing the welding related parameters and transmitting them to a remote computer;
a visual display for display of the welding process; and
a Wi-Fi module for transmitting the images and welding data to remote computer on-line, thereby tacking seam of the welding processes.
Typically, wherein the non-contact type sensors are a digital camera'.
Typically, wherein computer is a personal computer (PC).
Typically, wherein visual display is a colour monitor.
Brief description of the figures
Figure 1 shows General Arrangement of Seam Tracking & Data Logging System;

Figure 2 shows Arrangement of Sensors on Cross-Slides; and
Figure 3 shows Connection Block Diagram Description of present invention
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention as described bellow in the preferred embodiment.
The major components used in the system are - digital camera, laser displacement sensor, Industrial PC (IPC) with analog and digital I/O, cross-slide, PMDC motors, variable speed DC drives, IR sensor for temperature measurement, incremental Encoder for speed measurement, and Voltage & Current transmitters. As shown in Figure 1. the set-up of the entire system is done around the rotating shell. The shell (14) to be welded is kept on a tank rotator (12). The welding torch (10) is mounted on a motorized cross-slide (6). PC based control system (2) along with touch-screen monitor (1) are mounted on the boom / welding platform. Various sensors are mounted on the boom at required position and angle. Welding power source (11) is kept on the floor and welding cables are connected to the torch and the shell.
Figure 2 shows details of camera and laser displacement sensor (8). The details of control system (2) and their interconnections are shown in Figure 3. The control system (2) consists of an Industrial CPU loaded with customized software for the application, DC drives for horizontal and vertical slides, Firewire™ interface module for camera, analog & digital I/O modules, Wi-Fi module with antenna and signal converters.

Operation
The operator will select the mode of operation - Automatic or manual - from the hand-pendant (3). In manual mode, motors for horizontal and vertical slides (4 and 5) can be moved by the operator as and when required using hand-pendant. This mode is used for positioning the welding torch (10) in the groove (15) before starting welding.
After positioning the welding torch, the camera (7) is aligned in such a way that the groove edges are properly detected. This position of the groove is stored in the memory of the control system (2) as a reference. Also, the analog voltage from the laser displacement sensor (8), which is proportional to the distance between the sensor and shell-surface, is stored as a reference value in the memory of control system (2).
Now the operator selects Automatic mode from hand-pendant (3), then starts rotation of the shell (14) and then starts welding operation. During rotation, the camera (7) continuously detects the edges of the groove and feeds to the control system thru Firewire™ cable. The program written in the CPU compares the captured images with the previously stored position. If any deviation is detected, the software will calculate the offset position from the reference and will issue command signal thru analog output module to the DC drive for horizontal slide. The drive, in turn, will rotate the motor (5) for horizontal slide till the original reference position is reached.
Similarly, the output signal (4-20mA) from laser displacement sensor (8) will also vary proportional to the distance between laser displacement sensor (8) and job surface. This output is sent to the control system (2) thru analog input module. The software compares the current value with the original reference value and if any deviation is found, the software will issue command signal thru analog output module to the DC drive for vertical slide. The drive, in turn, will rotate the motor

(4) for vertical slide till the original reference value of laser displacement (8) sensor is reached. This process of capturing, comparing images & values and correcting thru drives is done continuously in Automatic mode. This way, it is ensured that slides, and in turn, welding torch mounted on the slides, are always in track with the groove. By maintaining the position and height of welding torch with respect to the groove, the uniform welding quality is achieved.
In addition to the above main purpose, there are more features in the system.
A) The image of welding process is continuously captured by the digital camera (7) and is displayed on the colour monitor (1) in front of the operator as well as on the monitor of a remote PC of the supervisor using Wi-Fi network. This feature is known as a Weld-Visual Display.
B) The system is used as a data logger for monitoring and recording all welding related parameters. Four parameters related to welding process are captured, transmitted to analog input module, and stored in the PC memory. These parameters are - Welding Voltage and Welding Current captured from Welding power source (II), temperature of the job measured by an Infra-Red sensor (9) and speed of rotation captured by an encoder (13) mounted on the Tank-rotator (12). The signals from these devices like IR sensor. Encoder, Welding machine, etc. are in different types and different ranges of values. Those signals are fed to signal converters kept inside the control system (2) and all of them are converted to equivalent current (4-20 mA) signals. Thereafter, these current signals are red by analog input modules and are converted to original values by software algorithms. These converted values are displayed on the monitor and are stored in the memory for the purpose of data logging.
In addition to these four parameters, software also calculates total productive time and non-productive time based on the signal values. The software plots the measured quantity with respect to time for analysis. Ail the measured parameters

and calculated time values are transferred to a remote server using a Wi-Fi network connection. This feature is known as a weld data logger.
C) By using software algorithms, the system is upgraded for automatic bead sequencing, wherein after one pass of the welding is complete (one rotation of the shell), the slides are automatically moved by required distance to position the welding torch in the groove for the next pass.
Advantages of present invention
1. Accurate seam tracking especially in ultra narrow gap seam welding
2. Display of welding process on remote screen is helpful in monitoring the process online
3. It helps the welder to position the torch accurately in the welding gap before starting welding process
4. Data logging helps to monitor productivity and quality of welding
5. Cycle time improves by automatic bead sequence logic
6. Better position accuracy (0.5mm) than the existing contact type seam tracking system (1.25mm)
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment.
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter.

The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention; which is defined by the scope of the following description.

We Claim:
1. A non-contact seam tracking cum data logging system, the system
comprising:
a non contact type sensor for sensing position of a welding torch with reference to edge of a welding groove;
a laser displacement sensor mounting on cross-slides;
a software algorithms for correcting the welding torch position according to the non contact type sensor and the laser displacement sensor feedback with an accuracy in the range of 0.3 to 0.7mm;
an analog I/O module for measuring the instantaneous values of welding related parameters, such as like welding current, welding voltage, welding temperature and surface speed;
a computer based system for recording and storing fhe welding related parameters and transmitting them to a remote computer;
a visual display for display of the welding process; and
a Wi-Fi module for transmitting the images and welding data to remote computer on-line, thereby tacking seam of the welding processes.
2. A non-contact seam tracking cum data logging system as claimed in claim 1; wherein the non-contact type sensors are a digital camera.
3. A non-contact seam tracking cum data logging system as claimed in claim 1; wherein computer is a personal computer (PC).
4. A non-contact seam tracking cum data logging system as claimed in claim 1; wherein visual display is a colour monitor.

5. A non-contact seam tracking cum data logging system, substantially as described in the description with reference to the diagrams.