NOV CTES has developed a tool which measures the diameter of the coiled tubing string while it is running in or out of the hole. A microprocessor in the digital display unit analyzes the measurements and displays ovality and minimum, maximum, and average diameters. These data are also available through an RS232 interface to our Orion data acquisition system or other computers.

Purpose of the Tool

Economical real-time measurements of coiled tubing (CT) diameter and ovality during CT operations.

• Sensor head with 12 probes
• Dual function cable for power and data transmission
• Operator interface and signal processing module
• Power supply

Principle of Operation

The cylindrical sensor head surrounding the CT contains three rings, each with four eddy current proximity probes in a radial array. The 90º spacing between the radials gives six (6) OD measurements with 30º spacing around the CT circumference. The sensing element of each probe faces the CT in the center of the ring. Each probe measures the distance from its face to the surface of the CT. Two diametrically opposite probes form a measurement pair. For a given measurement pair, the difference between the probe-to-probe spacing and the sum of these gap measurements is the OD. Thus, each ring provides two orthogonal diameters and a measure of the ovality of the CT cross section. Ovality is twice the difference of the two diameters divided by their sum,

2 x (OD max-OD min)/(OD max+OD min).

The cylindrical sensor head splits lengthwise in a manner that allows it to close around the CT. Thus, CTDOG can be installed on the CT between the reel and injector head at any time during CT operations. The sensor head attaches rigidly to the CT reel level wind. A single cable connects the sensor head to the remotely located operator interface and signal processing module.

Operator Interface & Signal Processing Module

• Supply power for the probes
• Convert the analog signal from each probe into a 8-bit digital signal
• Calculate diameters from the probe readings
• Calculate the maximum and minimum OD and the maximum ovality for the scanning interval (usually about 1 second)
• Digital display for calculated values
• Transmit calculated values to external computer via an RS232 interface
• Compare calculated values against user-defined limits and trigger alarms
• User interface for calibrating the sensor head and setting alarm limits

CTDOG Features

• 6 diameter measurements, 30º radial spacing
• Digital display of maximum diameter, minimum diameter, and ovality
• User-defined alarms for diameters and ovality
• Audible alarms for out-of-limit conditions
• Display update once per second
• Key pad user interface
• Field calibration of probe spacing
• RS232 output (character delimited text)
• 110 VAC or 24 VDC power options
• Installation on CT at any time during CT operations
• Bi-directional measurement

For additional information or quotation contact our sales department at (936) 521-2200.

Download a printable CTDOG Brochure

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