26MG Manual

May 30, 2016 | Author: Pramod Athiyarathu | Category: N/A
Share Embed Donate


Short Description

Download 26MG Manual...

Description

USER’S MANUAL

MODEL 26MG Part No. 910-166E

In accordance with European Directive 2002/96/EC on Waste Electrical and Electronic Equipment, this symbol indicates that the product must not be disposed of as unsorted municipal waste, but should be collected separately. Refer to your local Olympus distributor for return and/or collection systems available in your country.

Copyright  2005 by Olympus NDT. All rights reserved. No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without the written permission of Olympus NDT, except where permitted by law. For information, contact us at [email protected]. Other product names mentioned in this document may be trademarks of their respective companies, and are mentioned for identification purposes only. Printed in the United States of America.

01/15/04

910-166E

WARRANTY Olympus NDT guarantees the Model 26MG to be free from defects in materials and workmanship for a period of two years (twenty-four months) from date of shipment. This warranty can be extended beyond the two-year period. Consult us for further details. The warranty only covers equipment that has been used in a proper manner as described in this instruction manual and has not been subjected to excessive abuse, attempted unauthorized repair, or modification. DURING THIS WARRANTY PERIOD, Olympus NDT LIABILITY IS STRICTLY LIMITED TO REPAIR OR REPLACEMENT OF A DEFECTIVE UNIT AT ITS OPTION. The company does not warrant the Model 26MG to be suitable for intended use, and assumes no responsibility for unsuitability for intended use. The company accepts no liability for consequential or incidental damages including damage to property and/or personal injury. This warranty does not include the transducer, transducer cable, or battery. The customer will pay shipping expense to the Olympus NDT plant for warranty repair; Olympus NDT will pay for the return of the repaired equipment. (For instruments not under warranty, the customer will pay shipping expenses both ways.) Olympus NDT reserves the right to modify all products without incurring the responsibility for modifying previously manufactured products. The company does not assume any liability for the results of particular installations, as these circumstances are not within our control. THE WARRANTIES SET FORTH HEREIN ARE EXCLUSIVE AND ARE IN LIEU OF ALL OTHER WARRANTIES WHETHER STATUTORY, EXPRESS OR IMPLIED (INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A MODEL 26MG

i

PARTICULAR PURPOSE, AND WARRANTIES ARISING FROM COURSE OF DEALING OR USAGE OR TRADE.)

01/15/04

910-166E

CONTENTS 1 GENERAL INFORMATION....................... 1 2 BASIC OPERATION ................................. 1 2.1 2.2 2.3

INITIAL SETUP ...................................................... 2 MAKING MEASUREMENTS.................................. 3 LOW BATTERY ..................................................... 4

3 CALIBRATION.......................................... 1 3.1 3.2 3.3 3.4

INTRODUCTION..................................................... TRANSDUCER ZERO COMPENSATION ............ VELOCITY AND ZERO CALIBRATION.................. MATERIAL VELOCITY CALIBRATION ..................

1 2 2 4

3.4.1 UNKNOWN MATERIAL SOUND VELOCITY............ 4 3.4.2 KNOWN SOUND VELOCITY................................... 5

3.5 ZERO CALIBRATION ............................................. 6

4 ADDITIONAL GAGING FEATURES ........ 1 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8

BACKLIGHT............................................................ DISPLAY BLANK OR HOLD.................................. CALIBRATION LOCK ............................................ AUTO SHUT-OFF ................................................... DISPLAY RESOLUTION........................................ GAGE RESET......................................................... UNITS ..................................................................... FAST DISPLAY MEASUREMENT RATE WITH MINIMUM THICKNESS & FREEZE FUNCTION....

2 2 3 3 4 4 5 5

5 SPECIFICATIONS .................................... 1 MODEL 26MG

iii

910-166E

01/15/04

6 THEORY OF OPERATION ....................... 1 7 APPLICATION NOTES............................. 1 7.1 FACTORS AFFECTING PERFORMANCE AND ACCURACY ........................................................... 1 7.2 TRANSDUCER SELECTION.................................. 4 7.3 HIGH TEMPERATURE MEASUREMENTS............ 6

8 MAINTENANCE AND TROUBLE SHOOTING ................................................. 1 8.1 ROUTINE CARE AND MAINTENANCE ................. 8.2 TRANSDUCERS..................................................... 8.3 ERROR MESSAGES ............................................. 8.4 OTHER ERROR OR PROBLEM INDICATIONS.....

1 1 2 2

8.4.1 TURN ON AND LOW BATTERY PROBLEMS.......... 2 8.4.2 SETUP (“D—”) PROBLEMS ..................................... 3 8.4.3 MEASUREMENT PROBLEMS ................................. 3

8.5 BUILT IN TESTS..................................................... 4 8.5.1 DISPLAY TESTS....................................................... 4 8.5.2 KEYBOARD TEST .................................................... 5 8.5.3 PULSER RECEIVER PARAMETER TEST ............... 5

8.6 REPAIR SERVICE .................................................. 7 8.7 REPLACEMENT PARTS AND OPTIONAL PARTS AND EQUIPMENT.................................................. 7

APPENDIX I-SOUND VELOCITIES APPENDIX II – RS232 OPTION

iv

MODEL 26MG

01/15/04

1

910-166E

GENERAL INFORMATION

The Panametrics-NDTTM Model 26MG is a simple to operate hand-held ultrasonic thickness gage designed primarily for corroded metal applications. Although the Model 26MG has many features, it is as simple to use as a basic thickness gage. To measure thickness with a calibrated gage, couple the transducer to the surface of the material and read the thickness. The gage uses dual-element transducers to measure the thickness of corroded, pitted, scaled, granular and other difficult materials from one side only. A full line of transducers are available to measure materials between 0.020" (0.50mm) and 20" (500mm) thickness and between –20oC and +500oC in temperature. The Model 26MG makes full use of its microprocessor to offer selectable advanced measurement features. Moreover, the microprocessor in the Model 26MG continuously adjusts the receiver setup so that every measurement is optimized for reliability, range, and sensitivity. The advanced measurement features of the Model 26MG include the following: • Automatic probe recognition • Quick compensations for transducer temperature changes • Fast scan min hold mode with 20 readings/sec and freeze function. • Selectable Hold or Blank display during loss of signal (LOS) conditions

MODEL 26MG

Page 1-1

910-166E

01/15/04

• LCD with selectable backlight or auto backlight for a highly readable display under all lighting conditions • Selectable English/metric units • Selectable calibration lockout functions to prevent accidental change to calibration • Selectable resolutions .001" (.01mm) or .01" (.1mm) • Easy calibration for unknown material velocity and/or transducer zero. • Automatic power off

Page 1-2

MODEL 26MG

01/15/04

2

910-166E

BASIC OPERATION

The purpose of this section is to demonstrate how basic measurements can be made with the Model 26MG gage. The unit has been shipped from the factory set up with the following conditions. STANDARD RESOLUTION

0.001 in. or 0.01mm

SOUND VELOCITY

0.2322 in./µS or 5.898 mm/µS (Approximate sound velocity for the carbon steel test bar provided with the gage) See Note below

BLANK MODE

Display will blank when not making a measurement

A further explanation of these default conditions may be found in later sections of this manual. They may be changed by the operator after becoming familiar with the more sophisticated features of the gage. These conditions have been selected to demonstrate how simple it is to use the instrument.

Note: The default value for sound velocity is only an approximation of the sound velocity in the test block material. The sound velocity of low to medium carbon alloy steel is typically 0.2322 in/µS or 5.898 mm/µS. Therefore, if you find the default value gives inaccurate results on your material, refer to Section 3 for calibration instructions.

MODEL 26MG

Page 2-1

910-166E

2.1

01/15/04

INITIAL SETUP

Follow this procedure when operating the gage for the first time. 1.

Plug the transducer into the connector at the top end of the Model 26MG case. Note that the transducer cable connector must be oriented with center pin up. When unplugging a transducer, pull ONLY on molded plug, NOT on the cable.

2.

Press [ON/OFF] to turn the gage on. (The transducer should NOT be coupled to the test piece.) The display will now show the message.

Figure 2-1: This means that the gage requires the following transducer ZERO compensation step. 3.

Wipe all couplant from the tip of the transducer.

4.

Press [ZERO].

Page 2-2

MODEL 26MG

01/15/04

910-166E

The display will show:

Figure 2-2: 5.

You are now ready to make measurements. The current units are indicated on the right of the display. Inches (IN) or millimeters (MM) may be changed to the alternate measurement units with the F1 key as described in Chapter 4.

Note: This is not a substitute for doing a proper calibration. For materials other than the included test block, see Note under Section 2.2, Step 3 on next page.

2.2

MAKING MEASUREMENTS 1.

Apply couplant to the test block or material at the spot to be measured. In general, the smoother the material surface, the thinner the couplant may be. Rough surfaces require more viscous couplant such as gel or grease. Special couplants are required for high temperature applications (see Section 7.4).

MODEL 26MG

Page 2-3

910-166E

01/15/04

2.

Press the tip of the transducer to the surface of the material to be measured. Use moderate to firm pressure and keep the transducer as flat as possible on the material surface. See Section 7.1 for further hints on transducer coupling.

3.

Read the material thickness on the gage display.

Note: For highest accuracy both a velocity and zero calibration must be done. Refer to Section 3, CALIBRATION, for this procedure.

2.3

LOW BATTERY

The gage will operate for at least 250 hours on one set of batteries under normal conditions (not in FAST mode, backlight off). The battery symbol in the upper left corner of the display indicates remaining battery life.

Page 2-4

MODEL 26MG

01/15/04

3 3.1

910-166E

CALIBRATION INTRODUCTION

Calibration is the process of adjusting the gage so that it measures accurately on a particular material, using a particular transducer at a particular temperature. The Model 26MG calibration procedure falls into the following three categories: 1. Transducer Zero Compensation: Calibrates for the sound transit time in each of the dual transducer delay lines, which varies from unit to unit and with temperature. This simple off-block procedure must be done when the gage is turned on, when the transducer is changed, and whenever the transducer temperature changes significantly. 2. Material Velocity Calibration or CAL VEL: Done using a thick test block of the measured material with known thickness or by entering the previously determined material velocity manually. It must be performed for each new type of material. 3. Zero Calibration or CAL ZERO: Done using a thin test block of the measured material with known thickness. Unlike the first two calibrations, this procedure is not required unless the best absolute accuracy is demanded (better than +/-004" or +/-10mm). If required, it need only be done once for each new transducer and material combination. It does not have to be repeated when the transducer temperature changes. Transducer Zero Compensation will take care of it.

MODEL 26MG

Page 3-1

910-166E

3.2

01/15/04

TRANSDUCER ZERO COMPENSATION

This step must be done whenever the message “d —” and the ZERO flag are displayed (do ZERO). To do the Transducer Zero Compensation, wipe any couplant from the transducer face, and press [ZERO]. The gage will momentarily display the zero calibration value and then go to the measure mode automatically. When measurements are being made on surfaces that are significantly above or below room temperature, press [ZERO] on a regular basis.

3.3

VELOCITY AND ZERO CALIBRATION

The Material Velocity and Zero Calibration procedures may be combined using a thick and a thin calibration block of the same material. 1.

First update the Transducer Zero Compensation by wiping the transducer face and pressing [ZERO] while in the Measure mode.

2.

Then couple the transducer to the thick calibration block.

3.

Press [CAL].

4.

When the thickness reading is stable, press [VEL].

5.

Uncouple the transducer from the block and use the [

] or

[ ] keys to enter the thickness of the thick block. 6.

Page 3-2

Couple the transducer to the thin block and press [CAL].

MODEL 26MG

01/15/04

7. 8.

910-166E

When the reading is stable, press [ZERO].

] or

Uncouple the transducer from the block and use the [

[ ] keys to enter the thickness of the thin block. 9.

Press [MEAS] to complete the calibration and go to the Measure mode.

Note: Cal Velocity should always be performed on the thick sample and Cal Zero should always be performed on the thin sample. If the message UFLO is displayed when attempting to calibrate on or measure a thin material, then do the following: 1.Carefully repeat the calibration, making sure that the thin calibration block is within the measurement range of the transducer. If the UFLO message is not corrected, then continue with the steps below: 2. Do a Gage Reset. Press and hold [MEAS] and [F1] simultaneously for three seconds to enter into the SET mode. Use the up or down slewing keys until Reset (rSt) is on the display and press [F1] to implement reset.Then press [MEAS] to reset and return to the measure mode. 3. Couple to the thin calibration block. The UFLO message should be replaced by a thickness value. If the UFLO message is still displayed after doing a Gage Reset, then the gage should be checked at the factory.

MODEL 26MG

Page 3-3

910-166E

01/15/04

4. The measured thickness value while coupled to the thin calibration block should be within +/- 0.010 in. or +/- 0.20 mm of the correct thickness. If the indicated thickness is two or more times the actual thickness of the thin calibration block with a good approximate sound velocity, the gage is “doubling”, i.e. measuring to the 2nd or 3rd multiple echo. Do not attempt to do a Zero or a Velocity and Zero calibration under this condition. Doing so will cause the UFLO message to re-appear. Instead, correct the cause of the doubling. Either the calibration block is thinner than the specified capability of the transducer, the transducer is malfunctioning, or the gage is malfunctioning.

3.4

MATERIAL VELOCITY CALIBRATION

3.4.1

UNKNOWN MATERIAL SOUND VELOCITY

To do the Material Velocity Calibration, use a calibration block made from the material to be measured The block should be approximately as thick as the thickest section to be measured and have flat, smooth, and parallel front and back surfaces. The thickness of the block must be known exactly. 1.

Update the Transducer Zero Compensation by wiping the transducer face clean of all couplant and pressing [ZERO] as described in Section 3.2.

2.

Couple the transducer to the block.

3.

Press [CAL].

4.

When the thickness reading is stable, press [VEL].

5.

Uncouple the transducer and use [ thickness of the standard.

Page 3-4

] or [

] to enter the

MODEL 26MG

01/15/04

6.

910-166E

Press [MEAS] to complete the calibration and return to Measure mode.

If the gage double beeps and displays OFLO or UFLO before returning to the Measure mode, then an error has been made in the calibration procedure and the velocity has not been changed. The most likely problem is that the thickness value entered was not correct. Press [VEL] following Velocity Calibration (or at any time from the Measure mode) in order to read and record the material velocity for this particular material.This velocity may be entered by means of the slewing keys in the future when measuring this material, without using the block, as described in Section 3.4.2.

Note: Sound velocity in all materials changes with temperature. For maximum accuracy the calibration block should be at approximately the same temperature as the samples to be measured.

3.4.2

KNOWN SOUND VELOCITY

When preparing to measure a different material, of known sound velocity, the velocity may be entered directly without doing the CAL VEL procedure discussed above. 1.

From the Measure mode press [VEL]. The current velocity will be displayed.

2.

This number may then be changed to the desired value using the

3.

and

slewing keys.

Press [MEAS] to complete the entry and return to the Measure mode. If the gage is turned off before [MEAS] is pressed, the velocity will not be updated to the new value but instead will retain the previous current value.

MODEL 26MG

Page 3-5

910-166E

3.5

01/15/04

ZERO CALIBRATION

To do the Zero Calibration, a calibration block of the material to be measured must be used. The block should be approximately as thin as the thinnest section to be measured. If the surface of the material to be inspected is rough, the surface of the calibration block may be roughened to simulate the actual surface to be measured. Rough surfaces generally reduce the accuracy of measurements but simulating actual surface conditions on the calibration block can help to improve results. The exact thickness of the sample must be known. 1.

First update the Transducer Zero Compensation by wiping the transducer face clean of all couplant and pressing [ZERO] while in the Measure mode.

2.

Couple the transducer to the standard.

3.

Press [CAL].

4.

When the thickness reading is stable, press [ZERO]. The [ZERO] key will not be accepted if the LOS display flag is on.

5.

Uncouple the transducer and use [ thickness of the standard.

6.

Press [MEAS] to complete the calibration and return to the Measure mode. If the gage is turned off before the [MEAS] key is pressed, the Zero value will not be updated to the new value but instead will retain the previous current value.

] or [

] to enter the

If the gage double-beeps and displays OFLO before returning to the Measure mode, an error has been made in the calibration procedure and the Zero value has not been changed. The most likely cause is that the entered thickness was not correct.

Page 3-6

MODEL 26MG

01/15/04

4

910-166E

ADDITIONAL GAGING FEATURES

The Model 26MG has several convenience features in addition to the features discussed in Section 2, BASIC OPERATION. The use of these features is not required for basic operation, however, they make the gage a more versatile instrument. Access the following features through the [F1] key: • Auto Backlight on/off • Hold/Blank • Calibration Lock • Auto Shut-off • Display Resolution • Gage Reset • Measurement Units • Fast/Min Normal Measurement Mode with Freeze To access or change any of these functions, press and hold [MEAS] and [F1] simultaneously for 3 seconds to switch the gage into the Set Mode, then use the [ ] or [ ] slewing keys to advance to the function of interest as described below.

MODEL 26MG

Page 4-1

910-166E

4.1

01/15/04

BACKLIGHT

The display backlight feature internally illuminates the liquid crystal display with a bright uniform light. This allows the display (which has excellent visibility in normal to high ambient light conditions) to be viewed in low to zero ambient light conditions. The backlight is switched on or off by the [lightbulb] key. Additionally, when the backlight is switched on, you may select a power-saving Auto Backlight mode which turns it on only when a reading is being made and turns it off five seconds after LOS. To select Auto Backlight, enter the Set mode by pressing and holding the [MEAS] and [F1] keys, then press [ ] or [ ] until the display reads either “AUtO” for “automatic” or for “LtOn” for “light on” (continuous) (see Figure 41). Press [F1] to toggle between these choices. To return to the Measure mode, press [MEAS]. To access other functions press [ ] or [ ].

4.2

DISPLAY BLANK OR HOLD

The measured thickness display may be made to continuously display the last measured thickness when transducer contact with the material is lost or when there is insufficient signal to make a measurement, i.e. during loss of signal (LOS). This is called the Display Hold mode. In the Display Blank mode the numeric part of the thickness display is turned off during LOS. To change to the alternate display mode from the Measure mode, enter the Set Mode by pressing and holding [MEAS] and [F1] for 3 seconds and then press [ ] or [ ] until the display reads HOLd or bLn (see Figure 4-1). To change the Blank/Hold selection press [F1] again. To return to the Measure mode, press [MEAS]. To access other functions press [ ] or [ ].

Page 4-2

MODEL 26MG

01/15/04

4.3

910-166E

CALIBRATION LOCK

The Calibration Lock feature allows the gage to be set up so that no calibration values, i.e, velocity or zero, which affect the value of the displayed measurement, can be altered (with the exception of transducer zero while the gage is displaying “do—”). However these values can be viewed, and measurement modes can be changed, in the Calibration Lock condition. To set the Calibration Lock, enter the Set mode by pressing and holding [MEAS] and [F1] for 3 seconds, and then press [ ] or [ ] until the lock symbol flashes and the display reads either “On” or” Off" (see Figure 4-1). Press [F1] to select the desired lock condition. To return to the Measure mode, press [MEAS]. To access other functions press [ ] or [ ].

4.4

AUTO SHUT-OFF

Normally the gage turns off automatically after about six minutes if no key has been pressed and no measurement has been made within that time. This is to prevent the battery from running down if the gage is left unattended for a long period of time without being turned off. This shutoff can be disabled if for any reason it presents a problem. To disable or re-enable the auto shut-off mode, enter the Set mode by pressing and holding the [MEAS] and [F1] key for 3 seconds, and the press the [ ] or [ ] slewing key until the display reads “P.AUt” for “Power Auto Shutoff” or “P.On” for “Power Always On” (see Figure 4-1). To change to the alternate power selection, press the [F1] key. To return to the Measure mode, press [MEAS]. To access other functions, press the [ ] or [ ] key.

MODEL 26MG

Page 4-3

910-166E

4.5

01/15/04

DISPLAY RESOLUTION

The displayed resolution for thickness values , i.e. the number of digits shown to the right of the decimal point, may be changed from the keyboard. This may be useful in some applications in which the extra precision of the last digit is not required or where extremely rough outside or inside surfaces make the last display digit unreliable. These two resolutions are selectable; Standard is .001 in. or .01mm, and Low is .01 in. or .1mm. Select choice using [F1]. To change the resolution while in the Measure mode, press and hold [MEAS] and [F1] for 3 seconds to enter the Set Mode (see Figure 4-1). The decimal point will begin flashing, at which point it may be moved by again pressing [F1]. To set the position and return to the Measure mode, press [MEAS]. To access other functions press [ ]or [ ].

4.6

GAGE RESET

A simple key sequence may be used to quickly restore the gage to the default setup shown below. This may be useful to new operators while becoming familiar with the individual feature setups described elsewhere in this section. This may also be useful to experienced operators as an efficient short-cut to a known configuration. • • • •

The default setup established by this reset is as follows: Units in mm. Measure mode with normal display update rate. Material Velocity = 5.898 mm/µS, the approximate velocity of the included test blocks. • Default zero calibration. • Default sensitivity.

Page 4-4

MODEL 26MG

01/15/04

910-166E

• Calibration keys unlocked • Blank display when LOS • Standard resolution (.01mm) • Backlight off • Auto Shut-Off on To perform the Gage Default Setup Reset, enter the Set mode by pressing and holding [MEAS] and [F1] for 3 seconds, then press [ ] or [ ] until the display reads “rSt” (see Figure 4-1). To perform the reset, press [F1]. After resetting, the gage will display the word “dONE." To return to the Measure mode press [MEAS]. To access other functions press [ ] or [ ].

4.7

UNITS

Measured thickness may be displayed in either inches or millimeters. To change from one to the other, enter the Set Mode by pressing and holding [MEAS] and [F1] for 3 seconds and then press [[ ] or [ ] until the units indicator (“IN” or “MM”) begins flashing (see Figure 41). To change units press the [F1] key again. To return to the Measure mode, press [MEAS]. To access other functions press [ ] or [ ].

4.8

FAST DISPLAY MEASUREMENT RATE WITH MINIMUM THICKNESS & FREEZE FUNCTION

The Fast Min Display with minimum thickness mode increases the measurement and display update rate from 4 measurements per second to 20 measurements per second and will highlight the smallest thickness measured during a series of measurements.

MODEL 26MG

Page 4-5

910-166E

01/15/04

This is useful when performing high temperature measurements or when it is important to determine the thinnest reading obtained while making a series of readings on a test piece. The actual measured thickness will display when the transducer is coupled. The minimum thickness will be displayed when the transducer is uncoupled (LOS condition). In addition, while in this mode, the [F1] key acts as a Freeze function. This can be useful in avoiding lift-off error due to couplant while using the fast update rate. If you press [F1], the display will freeze the current thickness value. If you uncouple the transducer (LOS condition) and press [F1] a second time, the display will unfreeze and the minimum thickness held in memory will be recalled to the display. These features allow the benefit of real time thickness readout to be combined with a Minimum Hold and Freeze feature. This may be useful when the thickness profile of the test piece is very irregular, at elevated temperature, or when surface conditions are so rough that thickness cannot be measured at all locations. To obtain good readings quickly, select the Fast Min Display and scan the transducer on the material surface.

Note: The battery charge life is decreased by more than 50% when operating in the Fast Min mode. To select the Fast Display with minimum thickness, enter the Set mode by pressing and holding [MEAS] and [F1] for 3 seconds, and then press [ ] or [ ] until the display reads “SLO” or “F.LO” (see Figure 4-1).

Page 4-6

MODEL 26MG

01/15/04

910-166E

To change display rate, press [F1]. The “SLO” setting is the normal measurement mode.The “FL.O” setting is the Fast with minimum thickness and freeze mode. To return to the Measure mode press [MEAS]. To access other functions press [ or [ ], Once the gage is returned to the measure mode, pressing [F1] will freeze the display. Pressing [F1] again will unfreeze the display and recall the minimum. Pressing [MEAS] will reset the scan.

MODEL 26MG

Page 4-7

910-166E

01/15/04

Figure 4.1- Set Mode Flow Chart

Page 4-8

MODEL 26MG

01/15/04

910-166E

Figure 4-1: (Continued) MODEL 26MG

Page 4-9

01/15/04

5

910-166E

SPECIFICATIONS

THICKNESS MEASUREMENT RANGE

0.02 to 20 in. or 0.5 to 500mm (typical in steel) NOTE: Thickness range depends on material, transducer type, surface condition, surface preparation, and temperature.

THICKNESS DISPLAY RESOLUTION

Standard .01 mm or .001 in. Low .1mm or .01 in.

MEASUREMENT RATE

Standard Mode - 4 measurements per second Fast Min Mode - 20 measurements per second

MATERIAL VELOCITY RANGE

0.0300 - 0.5511 in./µS .0.762-13.999mm/µS

TRANSDUCER ZERO COMPENSATION

Provides zero and temperature compensation for different transducers

DISPLAY

41/2 digit (19999 counts) Liquid Crystal Display (LCD) 0.4" (10 mm) numerals

MODEL 26MG

Page 5-1

910-166E

01/15/04

DISPLAY UNITS, SYMBOLS & FLAGS

IN or MM (Thickness) IN/µS or MM/µS (Velocity) Low Battery Indicator Keyboard Lock LOS flag (Loss of Signal or Coupling) CAL flag (Calibration Mode) ZERO flag (Zero Calibration Mode) VEL flag (Velocity Calibration Mode) MEAS flag (Measure Mode)

RECEIVER BANDWIDTH

1–15 MHz (–3dB)

MEASUREMENT MODE

Time interval from a precision delay after the excitation to the first echo using dual element transducer.

METRIC / ENGLISH MODES

Allows selection between English and metric units via keypad.

POWER REQUIREMENTS

3VDC (supplied from internal batteries)

BATTERY

Two AA Alkaline batteries

BATTERY LIFE

250 hours minimum (measure mode) 30 hours minimum (backlight on)

OPERATING TEMP. RANGE (ELECTRONICS)

–10oC to + 50oC

Page 5-2

MODEL 26MG

01/15/04

910-166E

SIZE

5.05" L x 2.55" W x 1.14" 128.3mm L x 64.8mm W x 29.0mm H

WEIGHT

8.5 oz. (0.24Kg)

TRANSDUCERS

D790, D790SM, D791, D791-RM, D792, D793, D794, D795, D797, D798, D799, and MTD705

:

MODEL 26MG

Page 5-3

01/15/04

6

910-166E

THEORY OF OPERATION

The Panametrics-NDTTM Model 26MG Ultrasonic Thickness Gage operates on the dual transducer “pulse-echo” principal, timing the reflection of high frequency sound waves from the far wall of the test piece. This technique, derived from sonar, has been widely applied to nondestructive testing. The frequency range used by the 26MG does not travel well through air, so a coupling liquid such as glycerine or gel is used between the face of the transducer and the test piece. The sound waves generated by the transmit side of the transducer are coupled into the test piece, travel through it, and are reflected back from the opposite side. The reflected sound waves or echoes are coupled into the receive side of the transducer where they are converted back into electrical signals.The gage precisely measures the time interval ‘t’ between the excitation pulse and the first echo signal and subtracts a zero offset value representing transducer delay. The result is multiplied by the velocity of sound in the test material ‘V’ and divided by two to compensate for the two-way sound path. The final result, ‘X’ is the thickness of the test material. ( t )V X = ---------2 The microprocessor performs the arithmetic described above to produce the thickness value. This value along with various gage status indicators is sent to the LCD display. The microprocessor also directs the Receiver/Detector to identify the transducer type using the I.D. pin of the transducer. Calibration values and gage setups are saved in non-volatile RAM (Random Access Memory). The keyboard informs the microprocessor of user entered changes of mode, values, and related information.

MODEL 26MG

Page 6-1

01/15/04

7

910-166E

APPLICATION NOTES

7.1

FACTORS AFFECTING PERFORMANCE AND ACCURACY

A.

Surface Condition - Loose or flaking scale, rust, corrosion or dirt on the outside surface of a test piece will interfere with the coupling of sound energy from the transducer into the test material. Thus, any loose debris of this sort should be cleaned from the specimen with a wire brush or file before measurements are attempted. Generally it is possible to make corrosion measurements through thin layers of rust, as long as the rust is smooth and well bonded to the metal below. Some very rough cast or corroded surfaces may have to be filed or sanded smooth in order to insure proper sound coupling. It may also be necessary to remove paint if it has been applied in thick coats, or if it is flaking off the metal. While it is often possible to make corrosion measurements through thin coats of paint (on the order of a few thousandths of an inch or 0.1 - 0.2mm), thick paint will attenuate signals or possibly create false echoes, causing inaccurate measurements. Severe pitting on the outside surface of a pipe or tank can be a problem. On some rough surfaces, using gel or grease rather than a liquid couplant will help transmit sound energy into the test piece. In extreme cases it will be necessary to file or grind the surface sufficiently flat to permit contact with the face of the transducer. In applications where deep pitting occurs on the outside of a pipe or tank it is usually necessary to measure remaining metal thickness from the base of the pits to the inside wall.

MODEL 26MG

Page 7-1

910-166E

01/15/04

The conventional technique is to measure unpitted metal thickness ultrasonically, measure pit depth mechanically, and subtract the pit depth from the measured wall thickness. Alternately, one can file or grind the surface down to the base of the pits and measure normally. As with any difficult application, experimentation with actual product samples is the best way to determine the limits of a particular gage/transducer combination on a given surface. B

Transducer Positioning/Alignment - For proper sound coupling, firmly press the transducer against the test surface. On small diameter cylindrical surfaces such as pipes, hold the transducer so that the sound barrier material visible on the probe face is aligned perpendicular to the center axis of the pipe. See the illustration below.

Figure 1-1: It is possible that on some severely corroded or pitted materials there will be spots where readings cannot be obtained. This can happen when the inside surface of the material is so irregular that the sound energy is scattered rather than being reflected back to the transducer. The lack of a reading may also indicate a thickness outside the range of the transducer and instrument being used. Generally, an inability to obtain a valid thickness reading at a particular point on a test specimen could be a sign of a seriously degraded wall which may warrant investigation by other means.

Page 7-2

MODEL 26MG

01/15/04

910-166E

C

Calibration -The accuracy of measurements are only as good as the accuracy and care with which the gage has been calibrated. It is essential that the velocity and zero calibrations described in Section 3 be performed whenever the test material or transducer is changed. Periodic checks with samples of known thicknesses are recommended to verify that the gage is operating properly.

D

Taper or Eccentricity - If the contact surface and the back surface are tapered or eccentric with respect to each other, the return echo again becomes distorted and the accuracy of measurement is diminished.

E

Acoustic Properties of the Material - There are several conditions found in engineering materials that can severely limit the accuracy and thickness range that can be measured. 1. Sound Scattering: In some materials, notably certain types of cast stainless steel, cast irons, and composites, the sound energy is scattered from individual crystallites in the casting or from dissimilar materials within the composite. This effect reduces the ability to discriminate a valid return echo from the back side of the material and limits the ability to gauge the material ultrasonically. 2. Velocity Variations: A number of materials exhibit significant variations in sound velocity from point-topoint within the material. Certain types of cast stainless steels and brass exhibit this effect due to a relatively large grain size and the anisotropy of sound velocity with respect to grain orientation. Other materials show a rapid change in sound velocity with temperature. This is characteristic of plastic materials where temperature must be controlled in order to obtain maximum precision in the measurement.

MODEL 26MG

Page 7-3

910-166E

01/15/04

3. Sound Attenuation or Absorption: In many organic materials, such as low density plastics and rubber, sound is attenuated very rapidly at the frequencies used in normal ultrasonic thickness gauging. Therefore, the maximum thickness that can be measured in these materials is often limited by sound attenuation.

7.2

TRANSDUCER SELECTION

For any ultrasonic measurement system (transducer plus thickness gage) there will be a minimum material thickness below which valid measurements will not be possible. Normally this minimum range will be specified in the manufacturer’s literature. As transducer frequency increases, the minimum measurable thickness decreases. In corrosion applications, where minimum remaining wall thickness is normally the parameter to be measured, it is particularly important to be aware of the specified range of the transducer being used. If a dual is used to measure a test piece that is below its designed minimum range, the gage may detect invalid echoes and display an incorrectly high thickness reading. Table 1(following page) lists approximate minimum measurable thicknesses in steel for the standard transducers used with the Panametrics-NDTTM Model 26MG gage. Note that these numbers are approximate. The exact measurable minimum in a given application depends on material velocity, surface condition, temperature and geometry, and it should be determined experimentally by the user.

Page 7-4

MODEL 26MG

01/15/04

910-166E

Transducer Selection XDCR Part No

Freq (MHz)

Tip Diameter

Potted Cable Connector Style

Temp.Range

Min. Xness

D790

5.0

.434" 11.0mm

Straight Potted

-5o to +932oF

0.040" 1.0mm

.434" 11.0mm

Straight Replaceable

.434" 11.0mm

Rt. Angle Potted

.434" 11.0mm

Rt. Angle Replaceable

.283" 7.2mm

Straight Potted

+32o to +122oF

.283" 7.2mm

Rt. Angle Potted

+32o to +122oF

.283" 7.2mm

Straight Potted

+32o to +122oF

.283" 7.2mm

Rt. Angle Potted

+32o to +122oF

.900" 22.9mm

Rt. Angle Potted

-5o to +752oF

D790SM

5.0

D791

5.0

D791RM

5.0

D792

10

D793

D794

D795

D797

10

5.0

5.0

2.0

MODEL 26MG

-20o to +500oC -5o to +932oF o

o

-20 to +500 C -5o to +932oF -20o to +500oC -5o to +932oF -20o to

+500oC

0o to +50oC

o

o

0 to +50 C

o

o

0 to +50 C

0o to +50oC

-20o to

+400oC

0.040" 1.0mm 0.040" 1.0mm 0.040" 1.0mm 0.020" 0.5mm 0.020" 0.5mm 0.030" 0.75mm 0.030" 0.75mm 0.100" 2.5mm

Page 7-5

910-166E

01/15/04

Transducer Selection (Continued) XDCR Part No

Freq (MHz)

Tip Diameter

Potted Cable Connector Style

Temp.Range

Min. Xness

D798

7.5

.290" 7.4mm

Straight Rt.Angle

-5o to +300oF

0.028" 0.7mm

.434" 11.0mm

Rt.Angle Potted

.200" 5.1mm

Rt. Angle Replaceable

D799

MTD705

5.0

5.0

-20o to +150oC -5o to +300oF -20o to

+150oC

-32o to +122oF 0o to +50oC

0.040" 1.0mm 0.040" 1.00mm

In selecting a transducer for a corrosion application it is also necessary to consider the temperature of the material to be measured. Not all duals are designed for high temperature measurements. The chart above lists recommended temperature ranges for the duals used with the Model 26MG gage. For other transducers, consult the manufacturer’s catalogue or data sheets. Using a transducer on materials whose temperature is beyond the specified range can damage or destroy the transducer.

7.3

HIGH TEMPERATURE MEASUREMENTS

Corrosion measurements at elevated temperatures require special consideration. Keep in mind the following points: A.

Page 7-6

Be sure that the surface temperature of the test piece does not exceed the maximum specified temperature for the transducer and couplant that you are using. Some duals are designed for room temperature measurements only. MODEL 26MG

01/15/04

B.

C.

910-166E

Use a couplant rated for the temperature where you will be working. All high temperature couplants will boil off at some temperature, leaving a hard residue that is not able to transmit sound energy. Panametrics-NDTTM Couplant E (Ultratherm) can be used at temperatures up to 1000oF/ 540oC, although it will boil as the upper limit is reached. Maximum recommended temperatures for Panametrics couplants are in the table below.

Couplant

Type

Maximum Recommended Temperature

A

Propylene Glycol

300oF/150oC

B

Glycerine

200oF/90oC

C

Gel

200oF/90oC

E

High Temperature

1000oF/540oC

F

Medium Temperature

500oF/260oC

Make measurements quickly and allow the transducer body to cool between reading. High temperature duals have delay lines made of thermally tolerant material, but with continuous exposure to very high temperatures the inside of the probe will heat to a point where the transducer will be permanently damaged.

MODEL 26MG

Page 7-7

910-166E

01/15/04

D

Remember that both material sound velocity and transducer zero offset will change with temperature. For maximum accuracy at high temperatures, perform velocity calibration using a section of the test bar of known thickness heated to the temperature where measurements are to be taken.The Panametrics Model 26MG gage has a semiautomatic zero function that can be employed to adjust zero setting at high temperatures. See Section 3 for details.

E.

Using the Fast mode with the Freeze function may help in obtaining measurements as quickly as possible. Refer to Section 4.8 for details.

F.

Note that a corrosion gage is not designed for flaw or crack detection, and cannot be relied upon to detect material discontinuities. A proper evaluation of material discontinuities requires an ultrasonic flaw detector such as the Panametrics Epoch series used by a properly trained operator. In general, any unexplained readings by a corrosion gage merit further testing with a flaw detector. For further information on the use of dual element transducers in corrosion gaging, or for information on any aspect of ultrasonic testing, contact us.

Page 7-8

MODEL 26MG

01/15/04

8

8.1

910-166E

MAINTENANCE AND TROUBLE SHOOTING ROUTINE CARE AND MAINTENANCE

The Model 26MG case is sealed to prevent intrusion of environmental liquids and dust. However, it is not completely waterproof. Therefore, the unit should never be immersed in any fluid. Clean the case, keypad and display window with a damp cloth and mild detergent if necessary. Do not use strong solvents or abrasives.

8.2

TRANSDUCERS

The ultrasonic transducers or probes used with the Model 26MG need not indestructible and a little attention to the following items will result in the longest transducer life: •



The cables can be damaged by cutting, pinching, or pulling. Take care to prevent mechanical abuse to the cables. Never leave a transducer where a heavy object can be placed on the cable. Never remove a transducer from the gage by pulling on the cable. Pull on the molded connector housing only. Never tie a knot in a transducer cable. Do not twist or pull the cable at the point where it connects to the transducer. These precautions are particularly important for all transducers other than the models which have field-replaceable cables. Return other transducers to Panametrics-NDTTM Customer Service Department for repair.

MODEL 26MG

Page 8-1

910-166E



01/15/04

Transducer performance will be degraded by excessive wear at the tip. To minimize wear, do not scrape or drag the transducer across rough surfaces. When a transducer tip becomes too rough, concave, or otherwise non-flat, operation may become erratic or impossible. Although some wear is normal in corrosion gaging applications, severe wear will limit transducer life. A transducer resurfacing procedure can be performed to improve performance of worn transducers. Contact R/D Tech Instruments, Inc. for details.

8.3

ERROR MESSAGES

During the normal gage operation, certain special error messages may display. Usually these indicate a problem with the operating procedure but some may indicate a physical problem with the gage itself. Consult R/D Tech Instruments, Inc. for further information.

8.4

OTHER ERROR OR PROBLEM INDICATIONS

8.4.1

TURN ON AND LOW BATTERY PROBLEMS

The battery symbol will flash when there are only a few hours of battery operating time remaining. If the gage turns off immediately after turn-on, or if it does not turn on at all, then the battery is probably completely discharged and should be replaced. If the unit will still not turn on after replacing the battery, there has probably been a component failure within the gage and it should be serviced.

Page 8-2

MODEL 26MG

01/15/04

8.4.2

910-166E

SETUP (“d—”) PROBLEMS

If the message “do—” will not go away when [ZERO] is pressed, make sure a transducer is plugged in (see Section 3.2). If so, the transducer may be defective – try another one if possible, or try a different cable if it is one of the types that uses replaceable cables. If no transducers will permit the “do—” message to be removed, there is probably a problem in the Pulser/Receiver assembly of the gage. Try the Pulser/Receiver test described in Section 8.7 below.

8.4.3

MEASUREMENT PROBLEMS

If measurements cannot be made and the “MEAS” and “LOS” flags are on, there is either a problem with the transducer, the pulser/receiver assembly, or there is not a large enough echo being returned from the far wall of the material. In order to further diagnose the problem, perform the following procedure: 1.

Wipe off any couplant from the transducer and press [ZERO]. If a number between 2200-2500 and 7500 is displayed along with the “Zero” flag, both the transducer and pulser/receiver assembly are working. Go to step 2. Otherwise go to step 6.

2.

Make sure you have sufficient couplant especially on rough or curved surfaces. See Section 7.

3.

Try the same transducer on a smooth, flat surfaced test sample.

4.

If test 1, 2, and 3 above all pass, but measurements still cannot be made, try a different type of transducer which has greater sensitivity in the thickness range in which you are working. Go to step 6.

MODEL 26MG

Page 8-3

910-166E

01/15/04

5.

If another transducer of the same type is available, use it to make measurements and to do step 1. If this works, then the original transducer is defective. Otherwise the pulser/receiver assembly is probably defective.

6.

If the above tests indicate that there is a problem with the gage or transducer, then the unit(s) may be returned to R/D Tech Instruments, Inc. for repair or replacement. If the above tests indicate that the gage and transducer are working properly, the test material itself probably cannot be measured due to some or all of the following: • Extreme near side or far side surface roughness. • Extremely high sound attenuation or scattering due to graininess, inclusions, voids or, other material properties. • Extreme non-parallelism. • Excessively sharp curvature.

8.5

BUILT IN TESTS

In order to assist in troubleshooting, the gage has built in tests which help to identify the problem.

8.5.1

DISPLAY TESTS

1.

Plug transducer into gage.

2.

Turn the gage on.

3.

Press and hold [MEAS] and [ ] keys down simultaneously for three seconds. The display will show the software version number.

4.

Press [

Page 8-4

] or [

] until the display reads “dtSt,” then press [F1].

MODEL 26MG

01/15/04

910-166E

5.

Observe the following sequence of patterns on the display. Verify that in each image no segments are missing and none are added. Pause or resume the sequence any time by pressing [F1].

6.

Press [MEAS] key to exit from a display test. The display should read “dtSt.”

8.5.2

KEYBOARD TEST

1.

With “dtSt” on the display, press the [ ] key; the display should read “StSt.” Press [F1] for a keyboard test.

2.

Verify by pressing one by one each key except [MEAS] and [ON/OFF]; the gage beeps for each key and it displays only one corresponding segment.

3.

Press [MEAS]. The gage will display the corresponding segment momentarily and it will exit from the keyboard test.

MODEL 26MG

Page 8-5

910-166E

8.5.3

01/15/04

PULSER RECEIVER PARAMETER TEST

1.

Make sure the transducer is plugged into the gage.

2.

With “StSt” on the display, press the [ ] key twice; the display should read “HtSt.” Press [F1] for pulser receiver parameter test.

3.

The [F1] key will cycle through the test result in the order listed in the following table. Compare the number displayed for the different parameter to the range of values shown in the table below.

4.

For the Tx/Rx Test, disconnect the transducer. Press [F1] until the display reads “HtSt.” Continue pressing [F1] until the Tx/Rx test result is displayed. Verify the result.

Test Param.

D790/791/ 799

D792/793

D794/795

D797

D798

MTD705

DXW98

SM790

Pulser Receiver Parameters

Transducer #

01

02

04

06

07

08

10

19

Ref Gain

190240

190240

190240

190240

190240

190240

190240

190240

Tx Delay

200300

150250

150250

300400

100200

150250

150250

200300

Rx Delay

200300

150250

150250

300400

100200

150250

150250

200300

Main Det. Offset

123133

123133

123133

123133

123133

123133

123133

123133

Page 8-6

MODEL 26MG

01/15/04

910-166E

Test Param.

D790/791/ 799

D792/793

D794/795

D797

D798

MTD705

DXW98

SM790

Pulser Receiver Parameters (Continued)

Aux. Det Offset

123133

123133

123133

123133

123133

123133

123133

123133

Threshold

168

168

168

168

168

168

168

168

Gain #

36

46

61

58

36

75

83

36

Tx/Rx Test

2040

2040

2040

2040

2040

2040

2040

2040

To read the software version, press and hold [MEAS] and [

8.6

].

REPAIR SERVICE

R/D Tech Instruments, Inc. will repair any Model 26MG gage. In addition, some local R/D Tech Instruments dealers will be able to do repairs at customer sites or at their own facilities.

8.7

REPLACEMENT PARTS AND OPTIONAL PARTS AND EQUIPMENT

Replacement parts for the Model 26MG as well as additional related equipment is available from Panametrics-NDTTM Customer Service Department. See Appendix II.

MODEL 26MG

Page 8-7

01/15/04

910-166E

APPENDIX I SOUND VELOCITIES The following table provides a list of the ultrasonic velocity in a variety of common materials. It is provided only as a guide. The actual velocity in these materials may vary significantly due to a variety of causes, such as composition, preferred crystallographic orientation, porosity, and temperature. Therefore, for maximum accuracy, establish the sound velocity in a given material by first testing a sample of material. Material

V(in./µsec)

V(m/sec)

Acrylic resin (Perspex)

0.107

2730

Aluminum

0.249

6320

Beryllium

0.508

12900

Brass, naval

0.174

4430

Copper

0.183

4660

Diamond

0.709

18000

Glycerin

0.076

1920

Inconel®

0.229

5820

Iron, Cast (slow)

0.138

3500

Iron, Cast (fast)

0.220

5600

Iron oxide (magnetite)

0.232

5890

Lead

0.085

2160

MODEL 26MG

Appendix I-1

910-166E

01/15/04

Material

V(in./µsec)

V(m/sec)

Lucite®

0.106

2680

Molybdenum

0.246

6250

Motor oil (SAE 20/30)

0.069

1740

Nickel, pure

0.222

5630

Polyamide (slow)

0.087

2200

Nylon, fast

0.102

2600

Polyethylene, high density (HDPE)

0.097

2460

Polyethylene, low density (LDPE)

0.082

2080

Polystyrene

0.092

2340

Polyvinylchloride, (PVC, hard)

0.094

2395

Rubber (polybutadiene)

0.063

1610

Silicon

0.379

9620

Silicone

0.058

1485

Steel, 1020

0.232

5890

Steel, 4340

0.230

5850

Steel, 302 austenitic stainless

0.223

5660

Appendix I-2

MODEL 26MG

01/15/04

910-166E

Material

V(in./µsec)

V(m/sec)

Steel, 347 austenitic stainless

0.226

5740

Tin

0.131

3320

Titanium, Ti 150A

0.240

6100

Tungsten

0.204

5180

Water (20°C)

0.0580

1480

Zinc

0.164

4170

Zirconium

0.183

4650

References 1.

W. P. Mason, ″Physical Acoustics and the Properties of Solids,” D. Van Nostrand Co., New York, 1958.

2.

E. P. Papadakis, Panametrics, Inc. - unpublished notes, 1972.

3.

J. R. Fredericks, ″Ultrasonic Engineeringœ, John Wiley & Sons, Inc., New York, 1965.

4.

D. L. Folds,”Experimental Determination of Ultrasonic Wave Velocities in Plastics, Elastomers, and Syntactic Foam as a Function of Temperature, Naval Research and Development Laboratory, Panama City, Florida, 1971.

5.

“Handbook of Chemistry and Physics” Chemical Rubber Co., Cleveland, Ohio, 1963

MODEL 26MG

Appendix I-3

01/15/04

910-166E

APPENDIX II – RS232 OPTION The 26MG with RS232 option can transmit measurement readings over its RS232 cable to any device with an RS232 serial interface. The gage can be configured to send measurement readings continuously, single send by pressing [F1], or can be turned off. The RS232 port is half duplex (transmit only) and its communication parameters are fixed as follows: BAUD

9600

WORD LENGTH

8

STOP BITS

1

PARITY

N

The output data format is as follows: Thickness Unit Flags “CR” “LF” For example: -- .– MM L 20.49 MM Mm To change to the alternate RS232 transmitting setting, enter the Set mode by pressing and holding [MEAS] and [F1] for 3 seconds. Then press [ ] or [ ] until the display reads “SOFF” (Send OFF), “Son” (Continuous Send) or “SSnd” (Single Send) (see following figure). To change to the alternate selection press [F1]. To return to the Measure mode, press [MEAS]. To access other functions, press [ ] or [ ].

MODEL 26MG

Appendix II-1

910-166E

Appendix II-2

01/15/04

MODEL 26MG

01/15/04

MODEL 26MG

910-166E

Appendix II-3

View more...

Comments

Copyright ©2017 KUPDF Inc.
SUPPORT KUPDF