BASIC

FAMILIARIZATION GUIDE

FOR PIPE COATING

QUALITY CONTROL

TESTING & INSPECTION

PRODUCTION

SPECIFICATIONS

OTHER RELATED ITEMS

INTRODUCTION

Why you need to know about pipe coating? Pipe Coating represents a very large global industry that has expanded 20 fold in the past 20-30 years and is continuing to expand internationally. It provides for a very substantial workforce throughout the world which usually allows for above average remuneration.

To those who are considering this type of a career I will outline some aspects of the pipe coating industry commencing with Quality Control of pipe coating. As the title of this document dictates the document is a "guide only" and is not a basis for gaining accreditation or any form of qualification, it’s purpose is to familiarize you and give you an insight on some aspects pertaining to the pipe coating industry. Should one seriously wish to pursue a pipe coating career I would suggest you participating in one or more of the several professional and well recognized courses e.g. NACE and others, which can provide both training and certification for courses attended.

To go forward, pipe coating has been an substantial industry for nearly a century and spurred ahead at the advent of the Oil & Gas industries back in the 1960’s and in later years the middle east water transmission industry.

Common materials or types of coatings used for pipe coating today include a wide range which I will address as we go through this guide:

Typical Generic Type Applications include:

Reinforced Coal Tar Enamel For external pipe coating

Reinforced Bitumen Enamel For external pipe coating

Liquid Epoxy Coatings For Internal & External pipe coating

Liquid Epoxy Urethane Coatings For internal & external pipe coating

Fusion Bonded Epoxy Coating For internal & external pipe coating

Multi Layer Polyethylene Coatings For external pipe coating

Multi Layer Polypropylene Coatings For external pipe coating

Internal Flow coatings For internal efficiency

Polychloroprene (Rubber) Coatings For external splash zone coating

Internal Cement Mortar Coatings For internal water pipe coating

Concrete Weight Coatings For external stabilization coating

Insulation Coatings For extreme surface temperature conditions

Sacrificial Anodes For cathodic protection purposes

(Manufacture/Installation)

THE GUIDE

I have prepared this guide in modules each module addressing a particular element in regard to pipe coating. In this edition the first five modules will look at quality control aspects of the generic pipe coating activities.

MODULE 1

INCOMING BARE PIPE RECEIVED AT A COATING FACILITY

ELEMENTS IN THIS MODULE:

Pipe receipt

Pipe traceability

Pipe condition

Contamination, Vegetation, Oil

Excessive Corrosion

Bevel damage

Pipe wall defects, Gouges, Pitting, Dents, Out of Round

Chloride/Conductivity testing

1.0 PIPE RECEIPT (Load In to a storage area)

Part “1” describes the requirements for inspecting and recording the identity of pipe when received at a coating facility.

When receiving pipe it is normally expected that the pipe condition and the pipe identity markings are such that the pipe is in a fit condition to be passed through the coating facility and that the pipe identity is correct and is clearly legible.

The pipe shall be free from excessive vegetation and oil contamination and the identity established and verified. Each pipe shall be visually inspected for steel damage which includes bevel damage, gouges, dents, out of roundness and excessive corrosion and/or pitting.

Vegetation type contaminant Oil Contamination

Oil Contamination

Bevel damage

Bevel Damage

Typical Gouges

Typical Pitting

Example Heavy Rust

Example excessive rusting

Example Dents Example

Steel Laminations

Example Out of roundness

REMEDIAL ACTION:

Pipe that do not comply with incoming inspection criterion, shall me marked on the bevel end in accordance with the typical marking legend contained in section 4.0 below. Any defective pipes should be segregated as soon as possible and preferable stored separately. Unresolved pipe defect problems should be subject of a Non conformance report (NCR) until the disposition of the offending pipe is established.

Note: See also item 8 in Module 2

REPORT

Mark the pipe body in accordance with the marking legend example contained in section 4.0 below. Record the type and details of the defect on a designated Quality Control Form. If the pipe is considered to be a permanent steel reject (PSR) the offending pipe shall be subject of a non conformance report (NCR).

2.0 RANDOM SALT CONTAMINATION CHECKS.

It is often a requirement that salt contamination checks are to be carried out during the load in of the bare pipe (as well as in production) to determine the levels of salts that may exists on the pipe and to determine if pre water washing of the pipes is required. The testing for salts is carried out in accordance with an agreed Laboratory practice or method statement.

Typically the equipment used to determine chloride levels on steel substrates is an industry recognized instrument identified as a SCM 400

Using tweezers remove a sample absorbent paper from a protected pack of test papers and inject up to 2 ml of deionised water onto the paper surface using a syringe. Place the wetted paper on pipe and press firmly into the substrate ensuring as much air as possible is excluded.

Note: deionised water is not normal tap water it is specially processed water.

Chloride tester SCM 400

Wetting paper

Placing paper on the pipe

Switch the SCM 400 on by pressing the RED button. Press the button again to start a two-minute cycle timer. After two minutes remove the test paper from the pipe and place over the SCM

Picture showing switching location

Picture showing reading

On completion of test, lift the lid, remove the paper and clean the electrode with a high purity water soaked tissue.

Note; After use, the red button shall be pushed twice to switch off the instrument and the magnetic catch engaged.

REMEDIAL ACTION

Where salt readings are outside of the tolerances specified, the supervisor of the coating line shall be informed of the non conformance who will decide on what corrective action is to be taken.

REPORT

Record all test results on a designated Quality Form.

Record:

Sample Date

Pipe number

Location of tests

Chlorides detected expressed in µg/cm/2

3.0 RESIDUAL MAGNETISM

With some pipe coating projects there is requirement to check the pipe for residual magnetism which can affect welding operations downstream from the coating activity. Residue magnetism is measured in units of Gauss and is detected using an instrument called a Gauss meter.

The type of Gauss meter described in this module is a F.W.BELL 5070GAUSS/TESLAMETER. This is typical of the instrument required for residual magnetism testing.

Test for residue magnetism can also be required on the completion of pipe coating activities to determine if or the extent of residual magnetism being introduced during the coating activity. Prior to using this instrument a calibration procedure is required and the results documented.

Calibration of the Gauss meter

Prepare the probe zeroing, then rotate the function selector to the ZERO position.The “ZERO” legend will flash and actual dc flux density readings will appear on the display. The meter will select the lowest range regardless of which range was in use prior to using the ZERO function.

Recall that the maximum flux density level that can be zeroed is 30mT (300G or 23.88k Am). The meter will switch over to the dc mode of operation during zeroing. Recall that the zeroing operation affects dc errors only.

Press the AUTO push button and the process will begin. The “ZERO” legend will also flash.

Once automatic zeroing begins it must be allowed to complete. During this time all controls are disabled except for the POWER switch. The process normally takes from 5 to 15 seconds.

The meter selects the lowest range and adjusts the nulling signal until the net result reaches zero. The final zero values will remain in effect until the meter and probe are zeroed again, if the probe is disconnected or if the meter is turned off and back on again.

Zeroed

Initial electrical offsets in the probe and meter will be interpreted as flux density signals. To remove these errors place the tip of the probe in the Zero Flux Chamber and press the ZERO push button. Once the zeroing operation has completed, use the MANUAL ZERO mode to make fine adjustment as needed.

Stray magnetic fields from nearby equipment, magnets and the earth will also affect accuracy. To remove these errors place the probe in a fixed position and press the ZERO push button. The ZERO function can be used in static (DC) fields not exceeding the lowest full-scale range.

REMEDIAL ACTION

Gauss readings that do not comply with the tolerances specified shall be reported to the supervisor who will determine what action is to be taken.

REPORT

Report all the Gauss readings as required by the relevant ITP and record calibration details and report on the designated Quality Form.

Record:

Sample Date

Pipe number

Location of tests

Magnetism detected in Gauss

Note: "Be aware" that in checking for residual magnetism one must ensure that the testing racks or adjacent pipes or steel work is not affecting the Gauss readings (hall effect)

4.0 TALLY AND PIPE TRACEABILITY

Each pipe arriving at the coating facility shall be tallied upon reception. It is a "most important" activity that must be carried out in a diligent and accurate manner. All pipes when loaded into the coating facility must be properly identified. Usually the pipe number, heat number and length are to be recorded however in instances more details may be required
.

Legible pipe stencil

illegible pipe stencil

REMEDIAL ACTION:

Pipes that cannot be properly identified (ID is not legible), shall be marked in accordance with the typical marking legend contained in section 4.0 below and quarantined. The details of the problem shall be recorded and passed onto the Tally Coordinator. Unresolved pipe identity problems shall be subject of a Non Conformance Report (NCR)

Note: If a pipe looses its identification (traceability) and cannot be correctly identified it is often the case that the pipe cannot be used by the end user.

REPORT:

Complete record of each pipe shall be recorded on the designated incoming Tally Form.

Record.

Pipe number
Length
Heat Number
Wall Thickness
Weight

Typical colour code charts:

It is normal practice on most projects to have a colour chart included in the Manufacturing Procedure Specification (MPS) See typical chart below

MODULE N0. 2

INCOMING RACK & ABRASIVE BLASTING

ELEMENTS IN THIS MODULE:

Incoming rack traceability

Incoming Rack Inspection

Climatic Conditions

Blast Grade, Profile, Cleanliness

Pipe wall defects, Gouges, Pitting, Dents and Out of Round

Wall Thickness Measurements

Module “2” describes the requirements for inspecting and recording the identity of pipe when pipes are loaded into the coating facility incoming racks.

1.0 INCOMING RACK TALLY & TRACEABILITY

Pipes transported from the pipe storage yard and placed onto the incoming process racks shall be tallied and the pipe identity confirmed as being correct. This usually entails checking the pipe identity to that of the shipping manifest.

When pipes arrive at the incoming rack, they shall be checked for any mechanical damage and/or contamination. Also the pipe number, length and heat number shall be recorded on the relevant Inspection & Tally Forms.

Pipe Conditions:

Oil contamination

General Contamination

REMEDIAL ACTION:

Pipe with excessive damage, contamination or pipe marking irregularities shall be quarantined. A Non Conformance Report (NCR) shall be raised for unresolved damage/marking issues.

REPORT:

The tally and any damage shall be recorded on the relevant incoming rack Tally & Quality Forms and the defects marked up in accordance with the marking legend contained in section 4.0 of Module 1.

2.0 CLIMATIC CONDITIONS

Prior to abrasive blast cleaning a check must be made for the ambient relative humidity conditions at the blasting area. Normally the accepted local Dew Point level is for the pipe temperature to be a minimum of 5° C above Dew Point (DP) although in many instances a minimum of 3° above “local” Dew Point is sufficient. The Relative Humidity (RH) conditions shall be carried out in accordance with an agreed Laboratory Practice/method statement.

The equipment required for checking the relative humidity is a Whirling Hygrometer a two disc calculator and calibrated digital thermometer. The Whirling Hygrometer contains two thermometers, one for wet temperature and one for dry. The hygrometer is swung in the air for approx. 30 seconds, the temperatures are noted and the two disk calculator is used to establish dew point and relative humidity.

Note: As an Alternative to the above, an approved Electronic Dew Point/Relative Humidity Meter can be used. (Where electronic devices are used they shall be suitably calibrated and operated strictly in accordance with the manufacturer’s instruction).

Examples of typical equipment used for checking DP & RH conditions

REMEDIAL ACTION

Where the Dew Point or Relative Humidity criterion is not being met, the process parameters shall be adjusted to correct the irregularity. If these parameters cannot meet the specified tolerances for DP & RH the supervisor shall be informed and the problem resolved before continuing with production.

REPORT

The DP and RH shall be recorded on a designated the incoming rack Tally/QC Form.

Record:

Time

Pipe number

The relative humidity (RH) expressed in percentage

Dew point (DP) expressed in °C above DP.

3.0 ABRASIVE ANALYSIS & CONDUCTIVITY OF ABRASIVE

On a regular basis (once per 8 or 10 hour shift minimum) the abrasives mix used for cleaning shall be analyzed in accordance with an agreed Laboratory Practice/Method Statement to determine:

1.) The amount of fines contained in samples of grit/shot taken from the working mix of the

centrifugal abrasive blasting equipment.

2.) That the working mix is free from unacceptable oily type contaminants.

3.) The conductivity of the abrasives is within the specified limitation.

The equipment required for the various analyses includes: a calibrated weighing balance, a sieve assembly, a sealable container. A conductivity meter and probe and a plastic beaker.

Sieve analysis

From the working mix a 200 gram sample shall be taken for sieve analyses, the sample shall be accurately weighed and the weight recorded. The weighed sample shall then be placed in the sieve assembly; the assembly shall consist of one large mesh sieve 1.18mm, one fine mesh sieve 425 µm. and a bottom pan. The sieve sample shall be shaken in the assembly for a minimum of 30 seconds.

On completion of shaking, the sieve assembly shall be dismantled and the contents of each sieve and the bottom pan weighed. The weight left in each sieve shall be recorded then a calculation shall then be made to determine the amount of fines that is retained in the bottom pan (fines) The acceptance criteria shall be a maximum 16 % fines.

Grit sample

Sieves

REMEDIAL ACTION

Should a higher % of fines than that specified be determined, the working mix shall be topped up with fresh material until an acceptable level of fines can be demonstrated.

REPORT

The abrasive sieve analyses shall be recorded on a designated Quality Form.

Record:

Time

Date

Sieve analyses details.

Pass Yes/No

Contamination

To check the abrasive working mix for contaminants, a 100 gram sample shall be taken from the working mix and placed in a sealed container filled will a sufficient amount of solvent to fully saturate the sample in one third of the total solvent placed in the test container. The sample shall be vigorously shaken then the contents allowed to settle (2 minutes) The solvent in the test container shall then be observed to determine if any oily residue or other substance is apparent (floating at the top of the liquid).

Grit sample (No Contaminants)

Grit sample (With Oily and other Contaminants)

REMEDIAL ACTION

Should the abrasive be contaminated, the supervisor shall be informed and the whole working mix shall be changed.

REPORT

The abrasive contamination shall be recorded on designated Quality Form.

Record:

Time

Date

Pass Yes/No.

Conductivity

For conductivity testing of the abrasive a grab sample of the working mix is placed in a plastic container. Distilled water (which is conductivity calibrated) is then place into the container to fully saturate the abrasives and allow room to cover the holes on the conductivity test probe.

The conductivity probe is then immersed in the solution, making sure that holes are completely submerged. After two minutes the probe is placed on the bottom of the beaker making sure that no air bubbles remain trapped in the sleeve.

The conductivity meter is then switched on by activating the by ON/OFF button. The temperature coefficient knob then set to 2% to compensate for the temperature effect of average solutions. Select the prescribed 19.99 ms/cm range by pressing the appropriate range key and adjust the calibration trimmer located on the side of the instrument using the calibration screwdriver until the display shows “12.88 ms” (i.e the conductivity reading @ 25 ⁰C) All subsequent measurements will be compensated to 25⁰C (77⁰F). If preferred calibration can be compensation to 20⁰C (68⁰F) rather than 25⁰C (77⁰F), to do this adjust the trimmer to read “11.67 ms”. All subsequent measurements will then be compensated to 20⁰C the calibration is now complete and the instrument is ready for use.

Conductivity testing

REMEDIAL ACTION

Should the abrasive conductivity be outside of the specified tolerance, the supervisor shall be informed and appropriate action implemented. If the contamination problem cannot be resolved the whole working mix shall be changed.

REPORT

The conductivity analyses shall be recorded on a designated quality form.

Record:

Time

Date

Conductivity levels expressed in ms/cm

END PLUGGING (Required prior to external blasting only)

Prior to the bare pipe being indexed onto the blast line conveyor, both end of the pipe shall have internal end plugs inserted to prevent ingress of the blasting materials and to protect internal coatings (If applied)

Incorrectly fitted end plugs

Correctly fitted end plugs

4.0 PIPE INSPECTION AFTER BLAST CLEANING

After blast cleaning, all pipes should be visually inspected for steel defects. In cases where defects are deemed to be of a small nature i.e. small burrs, lamination's and/or minor pitting shall be lightly ground out (if required) to remove the defect.

Small lamination's

Minor Gouges

Minor pitting

Defects that are of a more serious nature shall be brought to the attention of the client prior to rectification work being carried out i.e. deep gouges, pits and or lamination's. An agreed procedure to rectify this type of damage must be approved prior to any repair taking place.

Deep gouges

Deep lamination's

Significant pitting

REMEDIAL ACTION

Should the steel defects be outside of the allowable steel defect tolerances the pipe shall be classed as a permanent steel defect (PSR), quarantined and be subject of an NCR’

REPORT

The details of all steel defects shall be recorded on a designated quality form and if necessary photos and sketches should be appended to the report.

Record

Date

Pipe number

Defect type

Location

Status Accept/Hold/Reject

5.0 SURFACE PROFILE

On completion of surface preparation activities, the abrasive cleaning has to be assessed for surface profile in accordance with an agreed laboratory practice/method statement.

Surface profile is defined as the average peak-to-valley depth that is created during surface preparation. It sometimes is referred to as “anchor pattern”, “tooth”, “surface amplitude”. Surface profile when observed under high magnification resembles lunar craters or a series of peaks and valleys in the surface of the steel. These peaks and valleys can be sharp, or “angular,” or they may be rounded or a mixture of both.

Surface profile or anchor pattern is generated by abrasive blast cleaning and by some power tool cleaning methods. The adhesion of the coating system to the underlying steel surface is greatly enhanced by generating this “peak and valley” pattern in the steel, which effect actually increases the total surface area for the coating material to adhere to.

Surface profile is quantified by measuring the depth of the “valleys” in relationship to the top of the “peaks.” Inadequate surface profile depth may not properly “anchor” the coating system (and disbonding may occur), on the other hand an excessive surface profile may cause rogue peaks that can potentially protrude through the coating film and cause pinpoint rusting and/or accelerated corrosion to occur.

There are three methods that are most practical and routinely used (both on the shop floor and in the field) for quantifying the depth of the surface profile after surface preparation.

Method A: Replica Tape
Method B: Surface Profile Depth Micrometer
Method C: Visual Surface Profile Comparator
Method D: Stylus/Rugotest

METHOD A (REPLICA TAPE METHOD)

Burnishing Testex Sample

Measuring Testex Sample

Knuckle Gauge & Testex Burnishing tool

Use of a replica tape in conjunction with a spring-loaded micrometer (Knuckle Gauge). This method of surface profile measurement entails generating an “impression” of the anchor pattern and measuring the impression using a spring-loaded micrometer.

The “Testex” replica tape itself consists of a non-compressible 2-mil-thick polyester film bonded to a compressible layer of foam, which is attached to the underside of the film). On all testx types,the film remains a constant 2 mils, but the amount of bonded compressible foam varies depending on the range of the replica tape. The compressible foam is pressed into the anchor pattern, effectively creating a mirror image of the surface profile in the foam. The peak-to-valley impression is then measured using a calibrated spring micrometer.

Step 1: Selecting the Appropriate Replica Tape

Prior to obtaining a surface profile measurement, select the range of the replica tape to be used. There are four ranges to choose from, including:

“Coarse,” which measures surface profile depth from 0.8 (20 µm) to 2.0 mils
“Paint Grade,” which measures surface profile depth from 1.3 to 3.3 mils (33 to 84 µm)
“X-Coarse,” which measures surface profile depth from 1.5 to 4.5 mils (38 to 114 µm)
“X-Coarse Plus,” which measures surface profile depth from 4.0 to 6.5 mils (102 to 165 µm).

Note: Replica tape typically is selected based on the specified surface profile depth being specified.

Step 2: Preparing the Surface for Measurement

Unlike other methods of surface profile measurement, the replica tape method can be adversely affected by residual abrasive and dust remaining on the abrasive-blast-cleaned surface. Therefore, prior to obtaining a measurement, ensure that the measurement area is free of dust and abrasive debris by lightly sweeping the surface with a clean brush.

Step 3: Preparing the Replica Tape

Remove a piece of the tape selected for use from the roll. Carefully remove the replica tape from the paper backing, this exposes the adhesive on the tape. Discard the paper backing and the small black and white protective circle attached to the paper backing. Ensure that the protective circle does not remain attached to the replica tape. Firmly attach the replica tape to the surface to be measured, leaving one corner folded over to create a pull-tab.

Step 4: Burnishing the Replica Tape

Using the rounded tip of the plastic burnishing stick provided with the micrometer, burnish the white, 3/8-in. (0.6-cm)- diameter circle located in the center of the replica tape until it turns uniformly gray. After verifying that there are no visible white streaks, use the pull-tab to lift the replica tape carefully from the surface.

Step 5: Adjusting the Micrometer

Adjust the micrometer so that the indicator needle rests on “0” with the micrometer anvils closed.

Step 6: Measuring the Replica Tape and Determining the Surface Profile Depth

Insert the replica tape containing the surface profile impression into the anvils of the micrometer and release the lever. This allows the top and bottom anvils to close in the center of the 3/8diameter film/foam circle.

The micrometer indicates both the thickness of the non-compressible 2-mil film and the peak/valley impression in the compressible foam. To determine the surface profile depth you must subtract the 2-mil polyester film thickness from the micrometer reading.

To eliminate the need for constantly deducting the film thickness you can set the micrometer needle on “8” rather than “0” in Step 5. This effectively presets the micrometer allowing for the –2 deduction.

Using the X-Coarse Plus Range of Replica Tape

The X-Coarse Plus replica tape can be used to measure very deep anchor patterns—up to ~6.5 mils or more. To use this tape, confirm that there is sufficient compressible foam mounted to the film before trying to obtain a measurement.

Prepare the tape as described in Step 3. Prior to attaching the tape to the surface, however, set the needle on the micrometer to “8” (effectively –2 mils). Insert the unused piece of replica tape into the anvils of the micrometer and release the lever. The micrometer reading is the maximum surface profile depth that can be measured with that piece of replica tape. Follow steps 4 through 6 above from this point forward.

Step 7: Recording the Measurement

Document the area tested and surface profile measurement on the test tape itself in the sections labeled “No.” and “Reading,” respectively. Always record the surface profile depth after the 2 mils has been deducted for the polyester film. Finally, verify that the recorded surface profile depth falls within the range of the tape chosen for measurement. If it does not, then the reading may be invalid.

Calibration of Surface Profile Measurement Equipment

It is not necessary to calibrate the visual surface profile comparator. If the comparator discs become tarnished, however, they can be difficult to use. A soft pencil eraser can be used to remove the tarnish without disturbing the electroformed pattern on each segment.

Calibration of the surface profile depth micrometer was described earlier. Conduct this “zero-verification/ adjustment” procedure prior to and after each period of use.

Although the replica tape itself needs no calibration, routinely confirm the micrometer’s level of accuracy by inserting shims of known thickness into the instrument and verifying a correct measurement. Plastic shims used to calibrate coating thickness gauges can be used for this purpose. Recognize, however, that these shims may not represent an exact thickness.

METHOD B (The Surface Profile Depth Micrometer)

Method B uses a surface-profile-depth micrometer. For this method, one measures the depth of the “valleys” using a conical-shaped metal tip. The surface profile depth appears on the gauge dial or on the digital display depending on the model.

Step 1: Verification of “Zero”

Before using the depth micrometer, verify the zero reading by placing the micrometer base onto a piece of plate glass. The gauge should indicate “0.” If it does not, adjust the dial gauge or the digital display until attaining a zero reading.

Step 2: Obtaining Surface Profile Measurements

Place the base of the calibrated gauge onto the abrasive-blast-cleaned steel and push downward. Do not slide the gauge as this will dull the protruding pinpoint and affect gauge accuracy. Read the scale or digital display and record the surface profile depth. The gauge reading represents the depth of the valley in a very small area. Therefore, it is important to obtain multiple measurements in a given area and to obtain measurements in multiple areas. Record each individual gauge reading in order to calculate the average and range of the anchor pattern.

Step 3: Re-verification of “Zero”

After using the depth micrometer, verify the zero reading again by placing the micrometer base onto a piece of plate glass. The gauge should indicate “0.” If the zero adjustment is off by a significant amount, it may be necessary to measure the surface profile again.

METHOD C (The Visual Surface Profile Comparator)

Method C uses the Visual Surface Profile Comparator method. For this method, one visually compares the prepared steel surface to an electroformed nickel disc containing known anchor patterns through a 5-power illuminated magnifier.

Step 1: Understanding the Comparator Disc Stencils

Each comparator disc contains five segments. Each segment of each disc is stenciled with a code identifying the surface profile depth, the disc type, and the year that a master disc was generated (the discs are electroformed copies of a master disc; they are not prepared individually by abrasive blast cleaning). The first stencil on each segment indicates the surface profile depth depicted in mils (e.g., 1, 2, 2.5, 3 mils [25, 50, 64, 76 µm], etc.). The second stencil on each segment indicates the abrasive type (S for Sand, SH for Shot, and G/S for Grit/Slag)

Your choice of disc will depend on the abrasive media used to blast-clean the steel surface.

Step 2: Selecting the correct Comparator Disc

Select the comparator disc that matches the type of abrasive used to blast-clean the surface. Use the S disc to compare surfaces that were prepared using silica sand; use the SH disc to compare surfaces that were prepared using steel shot; and use the G/S disc to compare surfaces that were prepared using grit or slag abrasives. G/S can represent a variety of abrasives, some of which include steel grit; copper, coal, and nickel slag’s; garnet; aluminum oxide (Al₂O₃); and others.

Many fabrication shops use an operating mix of steel shot and steel grit in their centrifugal blast machines. Because this is a visual assessment of surface profile depth, the G/S disc likely is the best candidate as it depicts angular peaks and valleys.

Step 3: Attaching the Comparator Disc to the Illuminated Magnifier

Choose the disc that represents the abrasive used to prepare the surface, then attach the disc to the viewing head of the 5X illuminated magnifier (face up, centered). The magnifier head is equipped with a magnetic strip that holds the disc in place during prepared surface examination.

Step 4: Examining the Prepared Surfaces

Turn on the magnifier’s light switch and place the magnifier with the attached disc directly onto the abrasive blast-cleaned steel (Figure 2). The hole in the center of the disc reveals the prepared surface. Compare this surface to each of the five segments and select the segment that is the closest match to the surface profile depth. If the surface falls between two segments, do not interpolate but simply record both segments as a range (e.g., 2 to 3 mils). Record the type of disc used and the surface profile depth (in mils). If the specification refers to surface profile depth in terms of µm (micrometers or microns), convert the surface profile in mils to µm by simply multiplying that amount by 25.4 (e.g., 3 mils is 76 µm). Therefore, accurately assessing the surface profile depth for compliance with the governing specification is paramount to a successful coatings project.

Method D (Stylus/Rugotest)

Surface Roughness can be assessed using electronic and stylus type instruments. Parameters commonly used when these instruments are utilized instruments:

Mean roughness Ra (ISO 4287, DIN 4768) The mean roughness Ra matches the arithmetical mean of the absolute values related to the profile deviation y within the reference length l.

Max. profile valley depth R max (DIN 4768) The max. profile valley depth R max counts for the most significant single roughness depths Zi within the total length lm.

According to ISO 4288 and DIN 4287 - Part 1, this parameter is also specified as Ry max.

Mean roughness depth Rz DIN (DIN 4768) The mean roughness depth Rz is the arithmetical mean of single roughness depths of successive sampling lengths le. According to ISO 4287 and DIN 4762, the parameter Rz DIN is also specified as RY5 .

Since Rz changes its name in both DIN 4768 and ISO 4287, this parameter is also specified as Rz DIN or Rz ISO

If the parameter Rz is measured according to DIN, it is generally admitted that the extreme value specified by ISO is matched providing that Rz ISO does not exceed Rz DIN

REMEDIAL ACTION

Where the surface profile is found to be out with the specified requirements the production line supervisor is to be notified and remedial action to be implemented. Pipe that has been found with profile depth defects shall be rejected and re processed.

REPORT

The surface profile determinations shall be recorded on the designated Quality Form.

Record

Date

Time

Measurements

Method

Average of the measurements expressed in µm.

6.0 BLAST CLEANING STANDARDS

The blast cleaning standard shall be determined in accordance with an agreed Laboratory Practice/Method Statement.

The blast cleaning standard is designated by the letters “Sa” e.g. common standards used are Sa 2.5 or Sa 3

Prior to blast cleaning, any layers of rust shall be removed by chipping. Visible oil, grease and dirt shall also be removed.

After blast cleaning, the substrate surfaces shall be cleaned from loosely adhered dust and residues.

Note: for descriptions of surface preparation methods by blast cleaning, including treatment prior to, and after the blast cleaning process see the relevant industry standard ISO 8504-2

Sa 2 Light blast cleaning

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter. See picture, Pictorial Standard No. 1

Sa 2.5 Thorough blast cleaning

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from most of the mill scale, rust, paint coatings and foreign matter. Any remaining contamination shall be firmly adhering. See picture, Pictorial Standard No. 2

Sa 3 Blast cleaning to visually clean steel

When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and shall be free from mill scale, rust, paint coatings and foreign matter. It shall have a uniform metallic appearance. See picture, Pictorial Standard No. 3

Typical pictorial standard

Pictorial Sa 2

Pictorial Sa 2.5

Pictorial Sa 3

The blast standard is visually monitored on every pipe and is randomly checked throughout the working shift against the relevant pictorial standards.

REMEDIAL ACTION

Where the blast standard is found to be out with the specified requirements the production line supervisor is to be notified and remedial action to be implemented. Pipe that has been found with blast standard defects shall be rejected and re processed.

REPORT

Record the blast grade on the designated Quality Form:

Record

Date

Time

Pipe number

Blast standard observed

7.0 SURFACE CONTAMINATION

The surface contamination shall be determined in accordance with an agreed Laboratory Practice/Method Statement.

To check the level of surface contamination after abrasive blast cleaning apply a suitable size strip of clear plastic adhesive tape on the area of steel substrate to be tested, pressing evenly and firmly onto the pipe and into the profile at the test area.

The tape is then removed carefully and placed (adhesive side to paper) on a white paper background (or pre formatted area of the inspection report).

The amount of contamination is then evaluated after displaying against the industry standard ISO-8502 Standard Chart for surface dust and contaminants.

Tape on pipe

Tape on Report

REMEDIAL ACTION

Where the surface contamination is found to be out with the specified requirements the production line supervisor is to be notified and remedial action to be implemented. Pipe that has been found with contamination defects shall be rejected and re processed.

REPORT

Record the surface contamination on the designated Quality Form:

Record

Date

Time

Pipe number

Contamination level 1-5

8.0 STEEL WALL DEFECTS (After Abrasive Cleaning)

Pipes that are segregated for pipe wall defects that require grinding are usually subject of an

NCR.

Before grinding the wall of a pipe the operator must be in possession of an agreed procedure and have a instruction from the owner of the pipe prior to carrying out the work.. This agreement however can be in the form of an approved action included in an NCR.

ASSESSMENT OF DEFECTS (general)

Pipes stood aside with steel wall defects shall be examined after surface preparation and the defects assessed according to the applicable Inspection and Testing Plan criteria, this criterion is usually in reference to a particular standard for steel pipe. E.g. API

Wall defects, pits, gouges, lamination's etc shall be clearly identified and marked up accordingly. Under some circumstances photographs shall be taken prior to any rectification work is carried out.

GRINDING OF DEFECTS

The grinding of defects shall be carried out using a hand grinder fitted with an appropriate cutting type disc. Care must be taken not to over grind defected areas; excessive over grinding may cause the loss of wall thickness to the extent that the pipe wall thickness no longer meets the requirements of the steel manufacturing specification.

Grinding shall be carried out in stages, a light grind followed by a wall thickness measurement check (Pit Gauge or UT) keep repeating this process and till either the defect is removed or when it is apparent that the pipe wall thickness tolerance will be breached.

REMEDIAL ACTION

Grind areas to remove defects within the pipe wall thickness tolerances. Note where grinding of the parent steel is close to the pipe wall thickness minimum tolerance the grinding shall not continue and the Client shall be informed of the problem.

DO NOT CONTINUE GRINDING

REPORT

The defects shall be recorded on an agreed Quality Form, sketches and photos are to be appended if required.

Record

Date

Type of Defect

Location

Status Accept/Hold/Reject

WALL THICKNESS CHECKS (USING ULTRASONIC THICKNESS and/or PIT GAUGE)

UT GAUGE - The ultrasonic thickness gauge shall meet the following requirements:

Type of instrument shall be approved by the client

Range of measurement: not less than 50mm

Accuracy of measurement: ±0.1mm

Application temperature: 0 ⁰C to + 40 ⁰C

Prior to wall thickness measurement, dust, dirty and rust in area to be measured shall be removed. The area to be measured shall be smooth and free of visible corrosion pitting.

The ultrasonic wall thickness measurement shall be taken according to the following steps:

Note: Measurements shall be taken on clean unaffected (defect free) areas of the pipe wall as close to the identified defect that is practical.

A minimum of two (2) measurements shall be made for each test zone. If slight difference in WT is noted the thinnest WT reading shall be used. If larger difference is noted, the reason shall be established before the unaffected WT is determined

Plug the probe into the UT gauge. Turn on the gauge. Start measurement after the gauge displays no indication of low power, input error etc.

Calibration

The gauge shall be calibrated each time when it is turn on and when the probe or battery is changed. Prior to calibration, reset the gauge to make the gauge into calibration status. Put some coupling agent onto the standard plate. Make the probe vertically and well touched with the plate until the gauge reads 4.mm to finish calibration.

If the gauge does not display expected number, move the probe away. Reset the gauge to make the gauge into calibration status and repeat the above steps until calibration is completed. The tolerance of the UT gauge shall be zeroed during calibration.

Measurement of Steel Pipe Wall Thickness

Evenly spread coupling agent onto the surface of area to be measured. Diameter of the coupling agent shall not be less than 15mm. vertically touch the probe to the surface to be measured. When the gauge is ready and displays a value, read and record the value to finish measurement.

Coupling Agent

To be washed and cleaned, coupling agent shall be of water-based solvent, such as composition glue and detergent. Its viscosity shall meet measurement requirement. Before measurement starts, the coupling agent shall be tested on the standard plate of the gauge, and shall be used only when the test result satisfies calibration requirement.

PIT GAUGE - The Pit Gauge shall be approved by the client.

CALIBRATION

Calibrate (or "zero") the pit gauge dial indicator. Place gauge on a flat reference surface. This surface should be true and without pits or other variations, and gauge should be oriented in a similar manner as surface to be assessed. Loosen locking mechanism, and rotate dial face until "zero" is aligned with large needle. Tighten locking mechanism.

Place gauge on surface to be assessed. "Feet" should be positioned on a true surface and should span the pit. If the feet of the gauge do not span the area being assessed then a bridging bar shall be utilized. Place dial depth surface on the flat surface as shown in figure (glass slide) Twist the movable scale until needle indicator reach to ‘0’ digit Dial depth gauge is ready to use

MODULE N0. 3

APPLICATION of COATING

ELEMENTS IN THIS MODULE:

Internal Flow Coating Application

Asphalt Enamel Application

INTRODUCTION PIPE COATING

Module “3” describes the requirements for inspection and recording the identity of pipes when being processed in anti corrosion coating facilities. Coatings described within this module include Internal Flow Coating and Asphalt Enamel

1.0 INTERNAL FLOW COATING

Internal Flow Coating is usually undertaken using specially formulated water based or epoxy coatings that can be applied to pipe internal surfaces. The coatings are usually applied to improve the flow efficiency of the pipeline rather than a protective coating, although in some instances the coatings are of a dual purpose.

Typical Internal Coating

1.1 MATERIALS:

All incoming materials should be checked against the material manufacturer’s certification and any other specification requirements. The incoming materials receipt report (IRF) must be completed when materials are received.

REPORT

Record

Material certification,

Batch numbers

Date of manufacture.

The form shall also outline the incoming tests required for the material (If required)

Note: All materials shall be stored strictly in accordance with the manufacturer’s instructions

Prior to the commencement of internal pipe coating it is imperative that all the fundamental requirements are assessed and checked out. This includes the testing of the raw materials to verify that they are in compliance to the specified requirements for the particular type of materials used.

The processing system must also be checked out to ensure that the material mixing and metering equipment is correctly calibrated and all application parameters are correctly set.

1.2 INCOMING PIPE

Pipes that are received at the incoming racks shall be inspected for contamination and/or pipe defects that prevents acceptable coating and cannot be repaired at the incoming rack or grinding area. See Module 2

1.3 PREHEAT & BLAST CLEANING:

Prior to abrasive cleaning, the pipes re be pre-heated (if required) to eliminate any moisture from the substrate. The internal surfaces are abrasive blast cleaned to remove rust and mill scale in accordance with the specified requirements for surface preparation. The typical blast standard requirement is a minimum of Sa 2.5.

The pipe surface temperature shall be monitored prior to blast cleaning using a hand held surface contact pyrometer or optical pyrometer. The preheat temperature should be checked as a minimum each hour. The steel surface temperatures to be blast cleaned shall typically be of 3° C above the local dew point, the dew-point should be checked at the commencement and twice per shift. All climatic conditions shall be recorded on an agreed Quality Report.

See Module 2

The blast cleaning is carried out using an internal blast unit that travels through the pipe interior at a controlled even speed that allows for the correct grade and blast profile to be achieved.

Internal Blasting

Pipes Prior to Blasting

Pipe after Blasting

On completion of abrasive blasting, the internally blasted pipe surface is visually inspected for surface imperfections.

Note: Suitable lighting must be available to assist with this inspection.

Where practical access is available, the imperfections shall be removed by hand filing or light grinding in a manner that does not adversely compromise the pipe wall thickness tolerances.

Where surface defects are observed that are not accessible to be repaired the pipe shall be stood aside and NOT coated.

The pipes should also be inspected for both surface cleanliness and surface roughness (Profile). The acceptance criterion and inspection frequency is found within an agreed project inspection plan (ITP)

See Module 2

It is normal practice that salt contamination checks are carried out at the commencement of production followed by two tests daily. The Maximum acceptable salt contamination level and test frequency is contained within an agreed project inspection plan (ITP)

See Module 2

After the inspection process, the cutback ends are prepared by placing self-adhesive masking tape of correct width to the internal cutback sections of the pipe.

Note: Where test panels or slides are required, they shall be affixed (if possible) in the cutback area of the test pipe.

The pipe is then lowered onto an a clean air blow out station where a high pressure air lance travels through the pipe and removes unwanted residue dust and blast media from the pipe internal. After the blow out station the pipe is then indexed to the coating application line and placed upon rotating buggies.

Responsibilities:

The Abrasive Blast Line Supervisor should ensure that the blast boom speed is travelling at the correct rate and that surface amplitude and cleanliness standards are maintained within the specified tolerance. He shall also be responsible for ensuring that all processing is performed in the safest possible manner.

The QC Inspector/Auditor shall be responsible for verifying that the specified climate, salt contamination, cleanliness, surface roughness and blast grade condition are monitored and recorded. He shall also ensure that samples of the abrasive are checked by the laboratory at the test frequency as specified.

The laboratory Technician shall be responsible for receiving the abrasive samples and for performing and recording the required tests.

1.4 MATERIAL APPLICATION

On completion of the surface preparation a counter levered material application boom (fitted with a material application head) travels at a pre determined travel rate within the pipe applying the coating material.

The constituent material components are mixed together (for normal airless application) at the mixing station, the mixed material is fed through the application boom and applied to the internal steel surfaces using an airless application head. ( for plural spray systems the materials are mixed at the application head on the paint boom just before the spray head tips).

The material application takes place whilst the pipe is steadily rotating and whilst the boom supporting the material application head retracts from the pipe at a pre-determined speed. After completion of coating, the freshly coated pipe is checked for the wet film thickness (WFT). The pipe is then rotated for a while at a higher rotation speed to reduce the risk of runs or sags occurring.

Paint Mixing Station

Internal Coating Application

Typical Airless Application

Typical Plural Mixing Head

Immediately after the application of the coating and removal of the cutback masking paper, the pipe is transferred to the post curing station. To accelerate curing of the freshly applied internal flow coating, warm re-circulating air is introduced to the pipe interior.

After the pre curing process, the initially dried coating is visually inspected for uniformity. In the event of bad weather, accepted pipe have their ends temporary covered with clear light gauge plastic sheathing which is perforated to allow egress of the solvents during the curing process. The plastic sheathing also protects the coating from dust and/or moisture while in the pipe storage area.

REMEDIAL ACTION

Non-conforming pipe are typically marked with white paint or applied masking band across the bevel ends to ensure pipe will be re-processed. Any defects (porosity/holidays) disclosed by visual and/or by wet sponge testing and other obvious defects shall be repaired by the applicator.

Pinhole type holidays shall be repaired using material similar to the parent coating materials and shall be touched up by hand using an artist soft brush in accordance with procedures approved by Client.

In cases where the damage coating of a larger nature the area shall be prepared by power wire brushing to ISO St 3. The sound parent coating surrounding the repair area shall be cleaned by removing all surface contaminants and loose or disbonded coating. The surface shall then be wiped clean and touch-up with a premixed material taken from the parent material application tanks.

See typical repair section procedure item 1.7 below.

Internal defective coating (under thickness) or damaged coating due to handling, shall be re coated within the manufacturer’s allowed re-coating time.

Note: Re coating can only be carried out if allowed and approved by the Client. If not approved, the pipe shall be rejected marked up as above and re processed.

REPORT

The coating details shall be recorded on an agreed Quality Form or Forms

Internal blast cleaning report

Internal coating report

Internal coating repair report

Record

Pipe Number

Sequence number (if required)

Pipe Length

Pipe OD

Pipe Wall Thickness

Coating Wet Film Thickness (WFT)

Cut back distance

Pipe Status (Hold Reject etc)

Repairs

Test Pipe YES/NO

Responsibilities

The coating supervisor should ensure that all coating is carried out under controlled conditions. If unsure about the disposition of pipe defects, he should contact the QA department with any queries. He should also be responsible in ensuring that the task is conducted in the safest possible manner.

The QC Inspector should be responsible for recording disposition of pipe exhibiting defects and raising NCR report. He shall also perform periodic testing in accordance with an agreed Inspection Test Plan (ITP)

The Tallyman should ensure traceability of all pipes and correct records of defective pipe movement and disposition.

1.5 INSPECTION AND TESTING

Visual Inspection

On completion of the coating and curing process each pipe are visually inspected. The coating should be a continuous smooth uniform even textured and coloured coating and should be free from runs, sags, pinholes and others imperfections indicative of incorrect coating application.

Cutback

All cutback distances are be checked and no tape residue should remain on the substrate.

Tape Adhesive Contamination

Thickness checks

Check the wet film thickness (WFT) using a comb-type gauge. Check the dry film thickness (DFT) either by using pre-calibrated magnetic lift off device and/or an electronic thickness gauge approved by Client.

Note: The Wet Film (WFT) measurement shall allow for the percentage (%) solids of the material for e.g, a 50% solids material shall have a WFT that is twice as thick of that of the required Dry Film Thickness (DFT)

The dry film thickness shall also be checked on metal test panels (Type B samples) coated within the test pipes and also on significant areas inside the test pipes. See off-line tests below

Holiday Detection

Normally it is a requirement to test significant areas inside test pipes for holidays using a low voltage wet sponge method.

1.6 OFFLINE TESTING

Besides the online testing and inspection requirements there are a series of “Off Line” tests that have to carried out to confirm compliance of the coating system against the specified requirements of the project. Test include the following practices:

Porosity Adhesion

Coating removal resistance

Curing Test

Bend Test

Salt Spray

Water Immersion

Gas Blistering

Typical method of affixing test sample plates to cutback area

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Porosity - API RP 5L2

Porosity Check (wet and dry) - Pinhole Check

Note:This practice may be modified by the requirements of the customer’s specification, see relevant Project Inspection Test Plan (ITP)

Scope

Carry our 100% visual examinations through a glass slides prepared and coated with the pipe during the coating process. Glass slides (Type A samples) both wet and dry shall be prepared and viewed with 100W bulb according to API RP 5L2

Typically a maximum of 5 pinholes shall be allowed on a test slide.

Equipment

Glass slide panel

Cleaning Solvent

100-watt light bulb and test box

Procedure

Attach solvent washed glass panels with roughened surfaces (size approximately 25mm x 75mm x 2mm) to the internal test areas of production pipes used as test pipes. On completion of coating the test pipes the glass slides shall be removed and examined. The panels shall be checked (by naked eye) both wet film and subsequently dry film for pinholes.

No pinholes shall be visible when viewed with the naked eye against the normal sunlight. There shall be no more than 5 pinholes on the glass slides visible when viewed against a 100-watt common household light bulb.

Porosity Checks