Thickness Monitoring Location Guide.pdf

ConocoPhillips Indonesia

Maintenance Engineering & Asset Integrity Manual

TITLE Thickness Monitoring Location Guide

DOCUMENT NUMBER COPI-OPR-OM-MA-00086

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DATE 27 May04

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Maintenance Engineering & Asset Integrity ConocoPhillips Indonesia

TITLE THICKNESS MONITORING LOCATION GUIDE

Manual DOCUMENT NUMBER

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TABLE OF CONTENTS 1.

INTRODUCTION .................................................................................................... 0

2.

PURPOSE .............................................................................................................. 0

3.

SCOPE ................................................................................................................... 0

4.

RESPONSIBILITIES .............................................................................................. 0

5.

PREPARATIONS – GENERAL.............................................................................. 0

6.

PREPARATIONS – PIPING ................................................................................... 0

7.

PREPARATIONS – VESSELS............................................................................... 0

8.

PREPARATIONS – STORAGE TANKS ................................................................ 0

APPENDIX A: DEFINITIONS AND ABBREVIATIONS .................................................. 0




1.


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INTRODUCTION

This document is to provide guidance to the Asset Integrity Engineer or the Inspection Engineer when establishing or reviewing locations of thickness monitoring locations (TMLs). It is applied to any process equipment that is subject to thinning either from corrosion or erosion. It is not applicable to finding damage from other mechanisms such as Stress Corrosion Cracking which requires a substantially different inspection program. Corrosion resistant piping and vessels are generally exempt from thickness monitoring except where erosion is identified as a potential damage mechanism.

2.

PURPOSE

This Thickness Monitoring Location Guide provides instructions for locating sites for performing ultrasonic thickness measurements on piping, pressure vessels and tanks systems when conducting an on-stream thickness survey. The TML locations should be designed to pick up the areas of highest predicted or expected corrosion rates. The intention is to do more thickness monitoring in areas where corrosion is likely and a lesser extent when corrosion is unlikely. To achieve this the Asset Engineer must understand the applicable corrosion mechanisms and the physical features, such as injection points, that might cause localized corrosion. The inspector must also understand that the TML location is only a starting point, if thinning is found then the inspector shall continue scanning outside the TML to characterize the entire extent of thinning.

3.

SCOPE

This procedure applies to ultrasonic thickness measurements taken on piping systems, vessels and tanks at ConocoPhillips Indonesia (COPI).

4.

RESPONSIBILITIES

The Asset Integrity Engineer in cooperation with the Inspection Engineer is responsible for ensuring proper location for ultrasonic measurements in accordance with this procedure and other applicable codes and specifications.

5.

PREPARATIONS – General 5.1

6.

Obtain Process Flow Diagrams, Process and Instrumentation Diagrams and, if possible, System Isometric drawings for piping. Obtain vessel or tank general arrangement drawings as applicable. Identify materials of construction, pipe classes and insulations specifications. Identify sand production that may lead to erosion. Determine predicted corrosion rates for the process fluid.

PREPARATIONS – Piping 6.1

Verify personnel performing Ultrasonic Thickness Measurements are qualified.

6.2

Ensure all instruments to be used have been properly calibrated.





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6.3

Before starting the inspection, the Inspector Engineer should review the results of the previous inspections and check with the operators in order to determine if the equipment has operated under any unusual conditions, such as high/low temperature excursions, overpressure, or any leakage.

6.4

SPECIAL TOOLS AND EQUIPMENT None

6.5

REFERENCES API 570: Inspection, Repair, Alteration, and Rerating of In-Service Piping Systems

6.6

PROCEDURE NOTE

Thickness measurement locations should be identified on the applicable inspection drawing. New locations not previously inspected should be added to the drawing when required. 6.7

Insulated Piping Insulated piping is only separated out from Non-insulated piping because of the need for special inspection “windows” and the need to look for Corrosion Under Insulation (CUI). For each TML a “window” will have to be cut into the insulation. Ideally, a replaceable plug will be inserted into this window to simplify future inspections. If this is not possible the insulation must be restored after inspection. Once the lines have been established to be subject to thinning corrosion, either by the Corrosion Engineer or from a RBI study, TMLs should be established at the following locations: •

On the center line of outer radius of elbows. The inspection point should be in line with the fluid flow and will cover the “target zone” where entrained particles would be expected to strike the inside of the elbow. This is generally the most severely attacked area from both erosion and corrosion. An additional TML shall be located one pipe diameter downstream from the elbow and on the same side of the pipe as the TML on the elbow. In cases where severe erosion is likely, an additional TML on the opposite side of the pipe at the same distance from the elbow should be established.

•

A pipe run in a known corrosive service should have TMLs at least every 5 meters. If the corrosion is known to be due to condensations then it is logical to have TMLs only along the bottom of the pipe but where corrosion is more generalized it is good practice to have TMLs located at 90-degree intervals around the pipe. In cases where severe erosion is likely an additional TML on the opposite side of the pipe at the same distance from the elbow should be established.

•

Measurement points should also be assigned to areas with unusually high historical or predicted corrosion rates.





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•

If further inspection is required due to corrosion rates or if the piping is approaching the retirement thickness, additional inspection holes will need to be provided.

•

Additional inspection windows should be established at low points to look for corrosion from water condensation or drop out and to look at the external condition of the pipe for CUI.

Obtain thickness measurements in accordance with the approved Inspection Procedure for Ultrasonic Thickness Measurement.

6.8

Non-Insulated Piping Once the lines have been established to be subject to thinning corrosion, either by the Corrosion Engineer or from a RBI study, TMLs should be established at the following locations: •

On the center line of outer radius of elbows. The inspection point should be in line with the fluid flow and will cover the “target zone” where entrained particles would be expected to strike the inside of the elbow. This is generally the most severely attacked area from both erosion and corrosion. An additional TML shall be located one pipe diameter downstream from the elbow and on the same side of the pipe as the TML on the elbow. In cases where severe erosion is likely, an additional TML on the opposite side of the pipe at the same distance from the elbow should be established.

•

A pipe run in a known corrosive service should have TMLs at least every 5 meters. If the corrosion is known to be due to condensations then it is logical to have TMLs only along the bottom of the pipe but where corrosion is more generalized it is good practice to have TMLs located at 90-degree intervals around the pipe. In cases where severe erosion is likely an additional TML on the opposite side of the pipe at the same distance from the elbow should be established.

•

Measurement points should also be assigned to areas with unusually high historical or predicted corrosion rates.

•

If further inspection is required due to corrosion rates or if the piping is approaching the retirement thickness, additional inspection holes will need to be provided.

•

Additional inspection windows should be established at low points to look for corrosion from water condensation or drop out and to look at the external condition of the pipe for CUI.

Obtain thickness measurements in accordance with the approved Inspection Procedure for Ultrasonic Thickness Measurement.

6.9

Injection Point Inspection Injection points are generally areas of increased risk of corrosion, either from condensation or incomplete mixing of chemicals. For injection points that use a quill, the TMLs should be located at 2 and 4 pipe diameters away from the pipe in the downstream direction and distributed at 90 degree intervals around the pipe




7.


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PREPARATIONS – Vessels 7.1


7.2


7.3


7.4


7.5

REFERENCES

7.6

API 510: Pressure Vessel Inspection Code, Maintenance Inspection, Rating, Repair and Alteration of Pressure Vessels ASME Boiler and Pressure Vessel Code, Section VIII, Div. 1.

PROCEDURE NOTE

Thickness measurement locations should be identified on the applicable inspection drawing. New locations not previously inspected should be added to the drawing when required. 7.7

Insulated Vessels Where specified in an equipment specific analysis such as a RBI study, the TML locations shall be located per the study. Where no specific studies have been made, one TML minimum should be assigned to each pressure-containing component. For example, each head, each shell diameter transition and all accessible nozzles shall be checked. It is preferred to have a TML in each shell section if accessible. TMLs should also be assigned to areas of known or predicted high corrosion rates. TMLs shall be located on drain nozzles. TMLs shall be located on any water boots on the bottom and at the normal water line. If further inspection is required due to abnormal corrosion rates, or if the vessel is approaching the retirement thickness, additional inspection insulation holes will need to be provided.





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For each TML a “window” will have to be cut into the insulation. Ideally, a replaceable plug will be inserted into this window to simplify future inspections. If this is not possible the insulation must be restored after inspection. 7.8

Non-Insulated Vessels As above, where a specific study provides locations for TMLs then that study shall be followed. Otherwise, one TML minimum should be assigned to each pressure-containing component. For example, each head, each shell diameter transition and all accessible nozzles shall be checked. It is preferred to have a TML in each shell section if accessible. TMLs should also be assigned to areas of known or predicted high corrosion rates. TMLs shall be located on drain nozzles. TMLS shall be located on any water boots on the bottom and at the normal water line.

8.

PREPARATIONS – Storage Tanks 8.1


8.2


8.3


8.4


8.5

REFERENCES API-653 Tank Inspection Code

8.6

PROCEDURE NOTE

Thickness measurement location should be identified on the applicable inspection drawing. New locations not previously inspected should be added to the drawing when required. 8.7

Shell -Course "A" of non-Insulated Tanks Using A Grid System





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NOTE A letter shall designate each course: “A” for the bottom course, “B” for the second course and so on.

All points on shell to be 2” from full seams (partial door sheet and patch plate seams not inclusive, unless through adjoining weld seam). If thickness readings vary more than .01", the area will be scanned and the average thickness will be recorded. 8.7.1

“A” course starting point is, facing tank from outside, left of first vertical weld seam left of the north most plate. (This area is normally identified by a man-way or tank piping.) Pipe+ Data Point Position Description

Location Description

8.7.2

2” left of vertical seam, 2” above chime weld. A1

BTM RT

8.7.3

2" above chime, midpoint left around shell plate. A2

BTM CN

8.7.4

2” above chime, 2” right of next vertical weld seam. A3

BTM LF

8.7.5

2” right of vertical weld, 2” down from top plate horizontal weld. A4

TP

LF

2” below horizontal weld seam, directly below each vertical weld seam from course “B”. **a.m.a.n.

TP

JCT

2” below horizontal weld seam, 2” left of vertical weld seam, above 9.1.2.

TP

RT

8.7.6

8.7.8

8.7.9

Pick up nozzles in this plate, right to left; top to bottom if TP MW vertically aligned. Include nominal size in location description; MTB MW 4NOZ top, bottom, and both sides on thickness on nozzles and on man-ways.

8.7.10 Continue on the next shell plate to the left in successive numbering, as in 9.1.2 through 9.1.7 above. 8.8

Shell -Course "B" of non-Insulated Tanks Using A Grid System NOTE Course “B” starting point is left of first vertical weld seam to left of course “A” starting seam. Pipe+ Data Point Position Description


8.8.1

2” left of seam, 2” above course “A” horizontal weld. B1

BTM RT

8.8.2

2” above course “A” horizontal weld, directly above course “A” vertical junctions. **a.m.a.n.

BTM JCT





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8.8.3

2” above course “A”, 2” right of next vertical weld seam.

BTM LF

8.8.4

Pick up all nozzles in this plate, right to left, and top to bottom if vertically aligned. Include nominal size in location description; top, bottom, and both sides on thicknesses on man-ways and nozzles..

TP BTM BTM MW 4NOZ

8.8.5

Continue on shell plate to left in successive numbering, as in Position Description 9.2.1 through 9.2.3 above.

8.8.6

More data points may be accessible on “B” course as steps are ascended. Effort should be given to obtaining thickness readings at junction welds, when possible.

Additional Shell Courses Course “C” and each succeeding course should have starting points at bottom of respective courses where accessible from steps. Effort should be given to obtaining thickness readings at junction welds, when possible. The top 2” of top course is an area of critical importance on tanks with cone roofs. This area should have data points every two feet (2’), starting nearest steps and continuing around tank, where accessible from, and in direction of, steps. **a.m.a.n. - as many as necessary. Some plates may not have any intersecting welds. Others may have several. Include all horizontal-vertical junctions.

8.9

Cone Roof of Insulated and non-Insulated Tanks Using A Grid System 8.9.1

The roof data points will be designated by a letter; “R”. Critical portions of roof are from platform to gauging hatch where Operations and gauging personnel walk. This area will be inspected on a 2’ grid, or “Walkway”, a minimum of 3 points (4’) wide. Grid starting point is determined by “best fit” of the Walkway from platform to gauge hatch. Each 2’ row of grid will be designated by successive “Steps” (see Attachment B).

8.9.2

Remaining portions of roof shall be shot in an “X” and “0” pattern. This “X” will be in an alignment such that one leg is straight from platform/step attachment over center of roof. The other leg of the “X” shall lay perpendicular to the first. One data point should be defined at each joint junction, i.e., roof course changes, plate changes, or combination of the two (case #1 in Roof Example drawing). If the first “X” lies such that a leg parallels the roof courses, an additional measurement should be taken at center of each plate (case #2 in Attachment B). The “0” pattern should be made at the outer most diameter of the tank roof. This area should incorporate at least two roof patterns wide the full circumference of the roof at the “T” seams of the roof.

8.9.3

The extent of the “X” pattern will therefore be determined by the diameter and alignment of roof to steps and platform. Thickness measurements should be taken on each end of plate as the line passes the course, and each junction near the line.

Pipe+ Data Point Position Description






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(for each data point in grid row titled “STEP”) 1)

2)

2’ off platform. Facing gauge hatch, the left-most point of grid. R1, R2, R3

STEP 1

2’ step toward gauge hatch, the left-most point of grid. R4, R5, R6

STEP 2

3)

Continue on the roof using “X” pattern in successive numbering.

4)

Continue using the “0” pattern starting at the left side of the stairway platform continuing clockwise around the tank. The numbering system should alternate from the outer course “T” seam location to the inner until the complete circumference of the tank has been completed.

8.10

Shell -Course "A" of Insulated Tanks Using A Grid System NOTE Each course is designated by a letter; “A” for bottom course, “B” for second course, etc. All points on shell to be 2” from bottom (chime) weld. “A” course starting point is left of bottom step of ladder when facing tank from outside. For intersecting ladders, start with shell data point to left of ladder attachment point. Continue in clockwise (left) direction. With insulated tanks, shell course sizes might take some guesswork for size, or some preliminary work may need to be done. Since vertical welds are generally not accessible, each course should be graded individually. That is, additional data points may be needed to confirm any variances in measurements. This will be a judgment call of the inspector at time of inspection. The approximate distance between data points will be determined by the inspector, generally not to exceed a maximum of 20° to 30°. The number of measurements on each course should be enough to give representative coverage. Pipe+ Data Point Position Description 8.10.1 2” above chime weld.

Location Description A1

8.10.2 Pick up nozzles in this plate, right to left; top to bottom if vertically aligned. Include nominal size in location description; with top and bottom thicknesses on man-ways.

TP MW BTM MW TP 4NOZ

8.10.3 Continue on the next data point to the left in successive numbering. 8.11

Shell -Course "B" of Insulated Tanks Using A Grid System NOTE Course “B” starting point is above or left of the first data point of course “A”. Pipe+ Data Point Position Description






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8.11.1 2” above course “A” horizontal weld. B1 8.11.2 Include all nozzles in this plate, right to left, and top to bottom if vertically aligned. Include nominal size in location description; - top and bottom thicknesses on man-ways. TP

TP MW BTM MW 4NOZ

8.11.3 Continue on shell plate to left in successive numbering. 8.11.4 Additional data points may be accessible on “B” course as steps are ascended. Additional Shell Courses Course “C” and each succeeding course should have a starting point at bottom of respective courses where accessible from steps. Where accessible, top 2” of top course is an area of critical importance on tanks with cone roofs. This area should have data points every two feet (2’), starting nearest steps and continuing around tank, where accessible from, and in direction of, the steps. 9.0

ATTACHMENTS Attachment A Attachment B Attachment C Attachment D -

Examples Of Shell Location Descriptions Non-Insulated Tanks Examples Of Roof Location Descriptions Insulated And Non-Insulated Tanks Examples of Shell Location Descriptions Insulated Tanks Revision History






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ATTACHMENT A EXAMPLES OF SHELL LOCATION DESCRIPTIONS NON- INSULATED TANKS

A1/BTM RT A2/BTM CN A3/BTM LF A4/TP LF A5/TP JCT A6/TP JCT A7/TP JCT A8/TP RT A9/TP MW A10/BTM MW A11/6NOZ A12/BTM RT . . . B1/BTM RT B2/BTM LF B3/BTM RT . . . B85/BTM RT B86/BTM JCT B87/BTM JCT B88/BTM LF B89/TP JCT . . .






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ATTACHMENT B EXAMPLES OF ROOF LOCATION DESCRIPTIONS - INSULATED AND NON-INSULTED TANKS






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ATTACHMENT C EXAMPLES OF SHELL LOCATION DESCRIPTION - INSULATED TANKS A1 / BTM RT A2 / BTM CN A3 / BTM LF A4 / BTM A5 / 4NOZ A6 / BTM . . . A44 / BTM . . . B1 / BTM B2 / BTM B3 / BTM . . . B27 / BTM B28 / MID . . . C1 / BTM C2 / MID ....





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APPENDIX A: Definitions and Abbreviations TP MW BTM NOZ TML

Top Manway Bottom Nozzle Thickness monitoring location


Thickness Monitoring Location Guide.pdf

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