before corrections are made. Accurate and timely corrosion measurement
is, therefore, an essentialp art of almost all corrosion control programs.
Thet echnologyo fc orrosiond etection andm easurement hasr apidly
advanced in the recent past, so today’s corrosion engineerhas many proven
techniques available for bothl aboratory analysisa nd on-line monitoring
to devise andm anage an effective corrosion control program for his (her)
particular plant process and environmental conditions.
11.1 Measuringa nd Monitoring Corrosion
As used herein, measurement of corrosionrefers to any technique that can be
used to determine the effects of corrosion:
1. While the facilities are in operation
2. During shutdowns
3. Whilet he laboratory analyses arep erformedo utside the
process equipment
Monitoring refers to as pecial group of measurement techniques that are
suitablef or use while the facility is in operation.
Ac omprehensive corrosion control program should includes everal
techniques because no single technique is capable of providing all the
information necessary in at imely manner.A no verview of measurement
techniques is presented below with emphasis on those useful in practical
on-line monitoring.
11.1.1R adiography
Radiography (x-ray) permits two-dimensional viewso ft he piping or
equipment wallsa nd is suitablef or detecting major flaws or as evere
corrosive attackwhen results are compared to an earlier (or baseline) study.
Radiography is not suitable for detecting small changes in residual wall
thickness because of accuracy limitations. Radiography is am easurement
techniquet hatr equires specializede quipment andt rained operators,
usually provided by contractor personnel, and is not currently used in
continuous on-line monitoring.
11.1.2U ltrasonic Measurement
Ultrasonic measurement techniques are similar to radiography in that
specialized equipment is required, and they are almostexclusively used for
measurement rather than monitoring. There are several types of ultrasonic
equipment. Ascan provides asimple depth measurement from the exterior
Corrosion of Linings and Coatings
534
CAT8247—CHAPTER 11—6/10/2006—12:56—SRIDHAR—XML MODEL B–pp. 533–547
is, therefore, an essentialp art of almost all corrosion control programs.
Thet echnologyo fc orrosiond etection andm easurement hasr apidly
advanced in the recent past, so today’s corrosion engineerhas many proven
techniques available for bothl aboratory analysisa nd on-line monitoring
to devise andm anage an effective corrosion control program for his (her)
particular plant process and environmental conditions.
11.1 Measuringa nd Monitoring Corrosion
As used herein, measurement of corrosionrefers to any technique that can be
used to determine the effects of corrosion:
1. While the facilities are in operation
2. During shutdowns
3. Whilet he laboratory analyses arep erformedo utside the
process equipment
Monitoring refers to as pecial group of measurement techniques that are
suitablef or use while the facility is in operation.
Ac omprehensive corrosion control program should includes everal
techniques because no single technique is capable of providing all the
information necessary in at imely manner.A no verview of measurement
techniques is presented below with emphasis on those useful in practical
on-line monitoring.
11.1.1R adiography
Radiography (x-ray) permits two-dimensional viewso ft he piping or
equipment wallsa nd is suitablef or detecting major flaws or as evere
corrosive attackwhen results are compared to an earlier (or baseline) study.
Radiography is not suitable for detecting small changes in residual wall
thickness because of accuracy limitations. Radiography is am easurement
techniquet hatr equires specializede quipment andt rained operators,
usually provided by contractor personnel, and is not currently used in
continuous on-line monitoring.
11.1.2U ltrasonic Measurement
Ultrasonic measurement techniques are similar to radiography in that
specialized equipment is required, and they are almostexclusively used for
measurement rather than monitoring. There are several types of ultrasonic
equipment. Ascan provides asimple depth measurement from the exterior
Corrosion of Linings and Coatings
534
CAT8247—CHAPTER 11—6/10/2006—12:56—SRIDHAR—XML MODEL B–pp. 533–547