Pipecoating Part 3

MODULE 5

Describes Concrete Weight Coating

Sacrificial Anode Installation

INTRODUCTION PIPE COATING

Module “4”” describes the requirements for inspecting and maintaining traceability of pipe when being loaded into and going through a Concrete Weight Coating facility where concrete coatings are applied and Sacrificial Anodes attached.

Concrete Weight Coating is typically applied to pipe by using impingement or wrap on technology. Weight coating is applied to pipes to allow added weight for stabilizing pipe on the sea bed offshore and/or through swamp areas onshore. The coating also allows for protection from trawl board impact offshore and mechanical protection onshore (road crossings and alike).

It is common that the density of concrete required for offshore pipeline activities to be greater than traditional concrete densities. To allow for higher than normal concrete densities, the concrete mix often contains Iron Ore as a constituent part of the concrete mix.

Concrete coating is usually applied to pipes that have already received an anti corrosion coating,  typically coatings are, Asphalt Enamel, Three layer Polyethylene or Polypropylene and to a lesser extent Fusion Bonded Epoxies.

For added corrosion protection, offshore pipelines are also fitted with segmented or bracelet type sacrificial alloy anodes. The anodes are usually fitted to the pipe at the pipe coating facility during the concrete installation process.


1,0         MATERIALS


All incoming materials are checked against the material manufacturer’s certification and other specification requirements and recorded on an Incoming receipt form ( IRF )


Cement


Cement shall conform to ASTM C 150 or BS 12 and to the Project specified the Alkali and C3A content requirements.


Aggregates and Sand


Aggregates and Sand shall conform to ASTM C33. However, where iron ore aggregates are used some aspects of the standard cannot be complied with e,g, the Gradation envelope may not be achievable: in such case a technical query should be raised and agreed to.


Reinforcement


All reinforcement shall meet the minimum specified % cross sectional area (CSA) requirements.

There are commonly two methods of reinforcement; rigid preformed cages (usually manufactured on site using Zublin machines) and wire mesh fabric. On occasions both methods are used simultaneously. (This usually occurs where high thickness concrete coatings are required).

Zublin Machine

Typical Zublin made Cage

Where rigid preformed cage reinforcement is used, the cages are fitted to the pipe prior to the concrete application process. Wire mesh fabric however, is wound into the concrete during the concrete application process. .

Cage reinforcement shall normally be required to meet the requirements of BS 4482, BS4449 or ASTM A615/A615M using wire with typically diameters of 5 mm for longitudinal and 7-8 mm for circumferential.

Welded wire fabric reinforcement shall normally be required to meet the requirements of ASTM A82 for zinc coated drawn wires, Typically one layer of wire is required for concrete thicknesses up to 55 mm above 55 mm concrete thickness two layers minimum are required.

Potable water

Water used for concrete should be clean potable water which is analyzed on a six monthly basis for cleanliness and impurities

Responsibility:

Materials Dept & QC Laboratory are responsible for ensuring that all materials are checked and comply with requirements of the agreed Project inspection Plan (ITP)


2.0        PROCESS DESCRIPTION

Incoming Pipe

At load in to the concrete facility pipes are passed through an “in line” holiday detector where the anti corrosion coating is checked for holidays and/or coating damage.

Holiday Detector

Pipes with holidays detected are isolated for repair and re-holiday detected before further processing.

Pipes that are designated for sacrificial anode installation shall be transported to the designated Anode Installation Rack See Anode Installation Section 9.0

Where rigid cage reinforcement is used, accepted bare and anode pipes are transferred to the caging area where predetermined lengths of caging are fitted. Cages are rigidly held concentric to the pipe at the correct location by electrically insulated plastic spacers. 


The spacers are manufactured to precise dimensions that allows for the reinforcement to be set evenly and at the correct distance from the anti corrosion coating. Whilst at the caging area rubber end rings are fitted at a set distance each end of the pipe. The rings allow for the correct concrete cutback distance to be established during the coating process.

Typical cage and spacers

Typical Rubber End Ring

On completion of the caging process the pipes are indexed to the incoming side of the concrete impingement area where end plugs are inserted to the internal pipe bore at both ends. The plugs prevent ingress of coating materials.


Note: Where no rigid cage reinforcement is required, hooks are attached to the lead end of the pipe which allow for the attaching of the wire mesh fabric reinforcement. The hooks shall be placed on rubber pads to protect the anti-corrosion coating damage and are affixed to the pipe using a strong banding method.


The pipe is then indexed directly to the impingement area.

Typical impingement Area

Responsibilities: 


The Incoming Supervisor shall ensure that the incoming holiday detection, reinforcement installation, fitting of end rings and end plugs are performed correctly. He shall quarantine pipes that are in need of repair and supervise the repair operation. He is also responsible for ensuring that all tasks are conducted in the safest possible manner.


The QC inspector/Auditor shall be responsible for the release or quarantining of the incoming pipe. He shall maintain checks in accordance with function described in an agreed inspection Test Plan (ITP)


The tally man shall be responsible for maintain pipe traceability and recording the disposition of rejected and repair pipes.


3.0        Mixing of Concrete


Prior to concrete coating, the batch plant, cement hopper and water feed systems are calibrated to allow accurate percentages of constituent materials to be delivered to the mixer. Typical constituents of the concrete mix are cement, high-density iron ore, sand and water. The concrete mix design is dependent on the Specific Gravity of materials being used and is proportioned accordingly.

 Typical Batch Plant Calibration Tolerances

Cement	± 2%
Aggregates	± 3 %
Water	± 2%
Whole	± 3 %

Sand/aggregates are typically transported from their respective stockpiles to the Mixing Plant hoppers using rubber tired front end loaders. From the feed hoppers the sand and aggregate are metered into the mixer at the mix design quantities. Cement is typically auger fed from the cement silo into a weigh hopper which weighs off the required amount to meet the mix design requirement.

Note: where aggregates are stored in outside open areas the working face of the stockpiles should be regularly turned over to maintain even moisture mix in the material. It is  inadvisable to take the material from the very bottom of stockpiles where moisture is likely to be exceptionally high,

Typical Batch Plant feed System

After weighing, the cement is added to the aggregate in the mixer. After a period of dry mixing, water is metered by volume into the mixer and the batch mixed for the prescribed mixing time. On completion of the mixing the concrete is conveyed to the short feed hopper. From the hopper the fresh mix is gravity fed onto a short belt which in turn progresses the mix to the concrete application head.


Note: Regular samples of the fresh concrete mix shall be taken from the feed belt to enable moisture content and fresh analyses to be carried out. Also for mix control purposes fresh mix test cube specimens are prepared.

Cube Making

Cube Samples

Responsibilities: 

The Batch Plant Supervisor shall be responsible for batch plant calibration and operation. He is to ensure that the parameters set through batch plant calibration are maintained throughout production. conveying aggregates to and from the correct holding hoppers ensuring that the correct amount of water is added to the concrete mix to provide consistent moisture content of the mix. He shall also be responsible in ensuring that the task is conducted in the safest possible manner.

The QC laboratory Technician shall be responsible for ensuring concrete mix calibrations are carried out correctly, taking samples of the concrete mix for analyzing and preparing samples for testing. He shall also be responsible for consistently reporting test results to the Batch Plant Supervisor, and for logging all test results.


4.0  COATING PROCESS:


From the impingement incoming rack or indexer, pipes are placed on the concrete coating line rotation buggy’s using an overhead crane using a spreader bar and suitably protected hooks. On the rotating buggy’s the pipes are transported past the impingement coating head where premixed concrete is applied at high velocity to the pipe using impingement rollers. The concrete plant operator selects the pipe rotation and forward travel speeds at a setting that allows for the concrete to be applied to the correct concrete coating thickness.


Pipes with anodes fitted are coated as per a plain pipe with the exception that a shadow plate and plastic wrap covering the anode is utilized to prevent excessive concrete covering the anode. After processing the plastic wrap shall be removed and the outer surfaces of the Anodes shall be cleaned and be free of concrete coating materials.


Diameter or thickness of the concrete coating is controlled by measurement using a girth or tree tape and is performed at the coating head and again verified at the weigh station.


Note Where wire mesh fabric reinforcement is used, the wire fabric is fed from a spool tensioning arrangement then travels though guides and onto the rotating pipe as the pipe is being impinged.

Welded Wire Fabric Feed

5.0  CLEANING AND WEIGHING STATION


Upon completion of the concrete coating, the pipe cutback areas are cleaned, the end plugs are removed and any debris in the pipe interior is also removed. The OD of the concrete is again measured: taking six equidistant measurements along the pipe.

 Taking Girth Measurements

Note: The concrete ends shall be finished square to the pipe axis and the crown of the concrete shall be slightly rounded.


When all redundant material has been removed from the coated pipe, the pipe is weighed using a calibrated weigh scale or load cell.


Pipes that are out tolerances for thickness and or weight may be flash coated or scraped to enable correct tolerances to be achieved. This rectification process shall be carried out whilst the concrete is in a green state and only if agreed to by the client.


At the cleaning station continuity (anode to pipe) and isolation (rebar to anode & pipe) and reinforcement position checks shall be performed on pipes in accordance with the agreed inspection frequency included in the Project inspection Test Plan (ITP)

Reinforcement placement check

Note : In the case where welded wire is used for reinforcement, the excess wire on the finish end of the pipe is trimmed back to just below the concrete surface to ensure no protruding wire is on the concrete surface. 

Excess Wire Fabric

When accepted the details of the pipe weight and girth measurements are entered into a pre programmed computer that determines the negative buoyancy (NB) of the pipe.


A typical formula for NB calculation


Weighing devices used to determine the weight of the concrete-coated joints shall be certified in writing to accuracy of 0.5%. The calibration of weighing equipment shall be checked by test weighing method previously approved by contractor unless other procedures have been agreed and confirmed in writing. Calibration of the weighing equipment shall be checked daily.

The unsaturated (as applied) submerged weight per metre (N/m) for each pipe shall be calculated from the pipe weight in air immediately after coating. 

The submerged weight, WSubmerged (N/linear metre), shall be calculated using the following formula:

where:


Mc    = Mass of fresh concrete coated pipe including reinforcement  kg
Dc     = Outer diameter concrete coated pipe m. Average of 6 girth measurements
Ds    = Outer diameter of steel pipe plus twice the anti-corrosion coating thickness, m
P1     = Density of field joint filing materials (assume 1025 )
I       = Cutback of concrete coating from bevelled end, m
L      = Mill length of steel pipe, m
Pw  = Density of seawater (assume 1025 )
SW   = Submerged weight

For anode and crack/buckle arrestor pipes, the specified maximum submerged weight may be exceeded. Variations in buoyancy shall be ignored and the submerged weight value shall be adjusted by using an increased weight in air.  The Principal shall specify the allowable weight variations in the Scope of Work.

The results shall be recorded and tabulated against pipe number and presented to the Principal at the completion of each day’s production. The submerged weight of each coated pipe shall be within the acceptance tolerances stated by the Client in the Scope of Work.

Responsibilities:

The concrete plant supervisor is responsible for ensuring that all equipment and personnel are adequately organized to carry out concrete batching, placement of reinforcement, coating, repairing and checking all coating parameters. He is also responsible in ensuring that the task is conducted in the safest possible manner.  

The concrete plant operator is responsible for maintaining the correct mix design, travel and rotation speeds, placement of reinforcement, end rings and anode protection.

The coating Tally man is responsible for recording the traceability of the coated pipes, the correct recording of pipe weights, pipe lengths, coating diameter, cutback lengths and submerged weight (NB) calculation. He will also keep an ongoing log of running (NB) averages.

The QA inspector/Auditor is responsible for the correct calibration of the weigh scales (NB station), periodic checking of any repairs to anti corrosion coating, the concrete coating parameters, including wash out checks of the reinforcement, overlaps for reinforcement and periodic isolation/continuity checks.


6.0        CONCRETE CURING


From the cleaning area acceptable coated pipes are lifted by overhead crane onto trucks having suitable cushioning and supports that protect the green concrete. The pipes are transported to the curing area where the freshly concrete coated pipes shall be laid out in single layers approximately 250 mm apart on suitable sand berms using either an overhead gantry or mobile crane.

Pipes that are to be cured using the Fog Cure method shall be covered as soon as practical with a tarpaulin and ‘fog’ water spray shall be introduced via water pipes fitted with fine misting nozzles under the covers to maintain a high humidity beneath the covers.

The pipes shall remain in the cure bay until the concrete has achieved a minimum stacking strength of 14 Mpa (as determined by concrete cube strength testing). On completion of the curing process and prior to stacking the cutback end rings shall be removed and any concrete contamination shall be removed from the coating steel cutback and internal bore.

Pipes selected for concrete coupon testing shall be clearly marked and placed on hold in an area suitable for coupon extraction work to be performed. Coupon holes shall be repaired in accordance with the approved Concrete Repair Procedure.

Note: Test cube specimens taken from the fresh mix at the batch plant shall be placed in the curing bay and cured in a manner identical to the pipe.


7.0        REPAIRS

  

Repairs to the coatings shall be carried out in accordance with an approved Repair Procedure. Coated pipes that cannot be repaired shall be rejected, stripped and re coated. Unacceptable pipe shall be marked up with Red/White hazard tape and recorded on the NCR system.

After the completion of acceptable repairs the pipe will then be placed in its allocated storage area. The stacking height for concrete coated pipes shall be in accordance with the approved handling procedure.

Repairs on freshly applied concrete shall be carried out at the coating plant whenever appropriate or at the curing bay.

Typical repair procedure

Upon visual examination, concrete coatings that are damaged, are defective or do not meet with requirements shall be repaired. The circumstances of the damage or defects will dictate the appropriate method of repair.

Repairs Criteria

If the area is less than 0.8m² in any 3 m length of pipe may be repaired by hand patching providing that such repairs are carried out within 4 hours of concrete application.

If the area is more than 0.8m² but less than 25% of total coating repairs shall be made using gunite. The concrete remaining shall be undercut to provide a key lock.

Cracks caused by excessive deflection in handling or storage, with the following criteria shall be repaired by chiseling the crack not less than 25mm and repair shall be made using the same basic material as the coating:-

Cracks in excess of 5mm width and extend over 180° circumferential around the coated pipe.

Cracks which are between 250mm – 1000mm in length longitudinally along the coated with the addition that the ends of each crack shall be drilled with a hole of 10mm nominal diameter to prevent crack propagation. The bottom of these holes shall be 7 -10mm from the anti-corrosion coating.

Cracks extending halfway through the concrete or penetrated to the cage

Longitudinal surface cracks of any width and less than 250mm in length shall not be considered a defect but holes of 10mm nominal diameter shall be drilled at the crack tips to prevent crack propagation.  The bottom of these holes shall be 7 -10mm from the anti-corrosion coating.

Surface damage shall not be considered a defect if :-

The total surface area of damage per pipe is less than 0.1 m², and

Max depth does not exceed  20% of coating thicknesses, and

The remaining concrete is sound.

Damage at the ends of the concrete coating need not be repaired provided that the damaged area is less than one third of the circumference for a length less than 200 mm.

Hand Repairs

Damaged areas may be repaired by hand patching in its ‘green’ concrete state. Patching shall be carried out by removing the defective area down to underneath the reinforcement and undercutting the sides to form a key. The cavity formed shall be filled with a mix similar to that used in the coating process with the addition of just sufficient water to allow hand application. Polythene wrap shall be used to seal the repair before curing. Maximum allowable time between concrete coating and repair of green pipe will be 4 hours.

Core Holes

Prior to filling cores holes, each site will be inspected for damage to the anti-corrosion coating. Damage to this coating will be brought to the attention of QC personnel and the Customer. Core holes shall be repaired using concrete with the same proportion of constituents as the original coating.

Core holes may also be repaired using concrete repair material “Mapegrout Fast-Set” (manufactured by Mapei) or “Certite” or similar product. A slight increase in water content may be considered acceptable to aid cure for some of the materials. The material shall be trowelled in such that the surface level is continuous with the level of the existing coating around the repair.           


Gunite Repair Criteria

Repair on cured concrete coating and large repair areas shall be rectified using the gunite method of repair. The size of the gunite repairs shall be demonstrated and witnessed for suitability as an addendum to the Pre qualification trials for concrete coating. The concrete mix design used for gunite repairs will be of the same constituent make up as that of the parent mix material apart from the use of extra water to assist with the application. Curing of the repairs will be carried out by wrap sealing of polyethylene membrane.


Gunite Repairs


GREEN CONCRETE

Damaged or defective areas shall be prepared by undercutting and exposing the reinforcement throughout the damaged area and removing any loose concrete material. The area shall then be filled by Gunite application until the entire repair area is reinstated to the level of the parent material. The completed repair shall be dressed in a manner that allows a smooth transition to the parent material. Within 30 minutes of the repair completion the green concrete coated pipe shall be placed in the fog cure.

CURED CONCRETE

Shall be performed as that for green repairs with the addition of a water wetting application to the cured concrete coating interfaces prior to Guniting. The repair area shall have a curing membrane tightly affixed and shall stay in place for a minimum of 48 hours to allow sufficient cure.                   

Testing

Repair materials used for concrete repairs shall be tested for compressive strength as determined by 28 day cube strength results. The minimum strength to be achieved shall be that of the strength specified for the parent coating. The frequency of testing shall be at start-up, middle and end of project.  

Responsibility

The repair foreman shall be responsible for coating repairs and shall ensure the correct equipment and repair method is used for coating repair. He shall also be responsible in ensuring that the task is conducted in the safest possible manner.

QC, Inspector/auditor shall be responsible for checking the preparation and the completed repair.

All repairs are to be recorded and inspected for compliance to the repair method statements.

8.0  PIPE MARKING AND IDENTIFICATION

The identity of each pipe shall be established and entered into the pipe tracking system such that traceability is maintained. Accepted pipes will be released for transportation to the stockpiles or other processes.

Typical Marking Requirements

Pipe no

Length

WT

Heat no.

Date of coating

             

Responsibilities

Load out Tally man, shall ensure that the correct pipe markings are applied in accordance with the agreed marking system. He shall also be responsible in ensuring that the task is conducted in the safest possible manner.


QC, Inspector/Auditor shall be responsible for inspecting that the correct colour banding and markings are applied.


9.0  SACRIFICIAL ANODE INSTALLATION


Anode are typically fitted to the corrosion coated pipe prior to caging and concrete coating, however in some circumstances anodes can be retro fitted i.e. after concrete coating.


Process Description

The Coated line pipe shall be positioned on the support racks, over the anode lifting saddle. The pipe will be positioned until the longitudinal seam weld (if any) is located around either the 12 or 6 o'clock position or approximately 150mm of the weld seam. Once positioned the lifting saddle will raise the lower half shell of anode to the stationary pipe and hold it in position. The second half shell of anode shall be offered to the pipe and positioned over the first half shell, by means of crane jib. The two halves shall be carefully aligned and drawn tightly together using webbing tensioners, chain come-along or similar.

The centering of the anode along the pipe shall be in a manner that allows for casing segments to be fed onto the pipes.

Fit Up

Fillet Welding

Welding will be by metal arc process 

Fillet welding shall be carried out continuously around three edges of the overlapping straps of the anode halves. An insulating material shall be placed under the weld area to guard against heat damage to the anti corrosion coating.

Thermit Weld 

Fillet Weld    

 

Electrode Handling

Welding consumables will be SMAW electrodes for carbon steel.

Electrodes shall be baked for 2 hours at 325^o C and held at 150^o C in a suitable holding oven prior to use. Alternatively, follow manufactures instructions. The Welder shall keep electrodes in an approved quiver during use and return unused electrodes to the holding oven when not working.

Pipe Preparation:

Areas of anti corrosion (TLPE) coating are be removed within each gap between half shells, each area of removal shall be as small as practical to accommodate the Thermit Graphite Mould

The removal of coating shall be achieved by using a heated knife and / or a bolster type chisel cutting around the heated area that is to be stripped, following the removal of the coating the steel substrate shall be  power ground  to achieve a bright, clean roughened surface or St 3.

Connecting of Bonding Leads (Electrical Connection):

Each anode is normally manufactured complete with bonding leads; the bonding leads may be cut to size using a cable cutter or hacksaw to remove. The cable should be looped (pig tailed) so as not to be taut after welding.

The end 25mm of PVC/PE sheathing is stripped back to expose clean copper cable. The cable may be cleaned with a wire brush if required.

Cad welding process as follows:

Clean the conductors and position them in the well dry mould;

Place the metal retaining disc in the bottom of the crucible graphite mould;

Pour the welding metal powder into the graphite crucible, spread starting powder onto the graphite mould edge;

Open  the mould lid and ignite the welding powder using a  flint gun by firing the spark onto the starting powder;

The exothermic welding process takes place inside the graphite mould; and finally the exothermic connection is finished.

Clean the mould using scraper and brush and proceed to the next connection cable(s) ready for connection.

After welding, each completed weld shall be tested for electrical continuity and mechanical bonding strength (1 blow with a 1 Kg Hammer)

Electrical Continuity using Ohm meter

Anti corrosion Coating:

Subsequent to the satisfactory completion of anode installation, the anti-corrosion coating shall be reinstated as follows:

The exposed areas of steel substrate around the Cad weld and anode straps shall be wire brushed to a clean finish. All bare steel  shall then be coated using SOLVENTLESS 2 PACK  EPOXY  or other approved repair material.

Anode Completion:

After final inspection, the Anode completion procedure will be carried out, consisting of the infilling of the gaps between anode halves with either a gunite concrete or hot poured marine mastic method.

The reinforcement used during concrete coating shall be trimmed back from the edges of anode  allowing a 25- 50mm gap. Electrical continuity test shall be carried out to ensure that the reinforcement is electrically isolated from the anode/pipe. 

The gaps between the anode and the parent concrete weight coating shall in filled with either a concrete mix similar to that of the parent coating material (by hand or gunite method) Or by other approved in fill methods (for example moulded hot bitumen)  On completion a continuity check between Anode and the steel pipe shall be performed prior to moving the pipe to storage.

Inspection control:

Pre-qualification

The anode installation procedure and inspection shall be pre-qualified prior to the start of production.

The pre-qualification will be limited to anode closure (strap) and Cad welds.

Weld / Welder Qualification

Typically each welder shall perform one fillet weld on a test coupon sometimes supplied by client. The test coupon shall be macro sectioned and tested for hardness. 

All required tests shall be carried out and reported by credited 3^rd Party Inspection Laboratory.

Thermit Weld Qualification

Typically each production welding operative will be qualified by demonstrating their capability to perform a series of Thermit welds on a coupon sample. Each weld shall be mechanically tested by a single blow from a 1kg hammer, aimed at 90 degrees to the sample surface - no lifting or fracturing shall result. Electrical continuity test shall be carried out between pipe and anode

The test welds and coupons shall be sectioned and tested for copper penetration by a third party inspection house

The macro sectioned and hardness and penetration tests reports will be identified by coupon unique numbers.  Test results should meet the following:

Hardness shall not exceed 248 Hv10 when taken at 2mm intervals extending to 10mm either side of the extreme edges of the weld.

No cracks or penetration of alloying elements along grain boundaries by more than 0.5mm or any non-metallic inclusions will be detected at 200X magnification.


10.0      OFFLINE TESTING


Specific Density
Sieve Analysis
Moisture Content
Deleterious Substances
Fresh Analysis
Water Absorption
Compressive Strength Cubes
Compressive Strength Cores
Impact Test
Shear Test


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SPECIFIC GRAVITY - BS 812: part 2 1985


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


Scope


Determination of the Specific Gravity (SG) of Aggregate/Iron Ore

Equipment

Pycnometer

Electronic balance

Gas ring or oven

Procedure

Obtain a sample weighing approximately 2000 grams.Thoroughly wash the sample to remove all material finer than No. 200 Sieve (75micron).Dry the retained sample over the gas ring (or oven) and then allow it to cool  to room (ambient) temperature.

Place 500 g of dry aggregate (Weight, A) into the Pycnometer and fill it with water.  Whilst filling rotate the Pycnometer to eliminate all traces of trapped air within the sample material and allow settling. After settling, top up the Pycnometer with water again to remove any froth from the surface so that the water level in the hole at the to of the cone is flat and level. Dry the exterior of the Pycnometer and weigh (Weight, C).

Empty all the contents of the Pycnometer into a tray, making sure that the aggregate is completely emptied. Refill the Pycnometer to the original level with water (only), dry the exterior and weigh (Weight, B).

The difference in water temperature between the first and second weighing shall not exceed 2°C.

Carry out the test twice.

Evaluation

Calculate the Specific Gravity of the aggregate as follows:

Specific Gravity (SG) = Weight A / ((Weight A + Weight B) – Weight C))


Report

Record  Specific Gravity

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SIEVE ANALYSIS (GRADATION) OF AGGREGATES - ASTM C 33

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

Scope

To establish a Sieve Analysis (Gradation) of aggregates using interlocking, circular sieves of standard aperture sizes
.

Equipment

Nest of certified sieves

Sieve shaker

Calibrated weigh scale

Oven or gas ring

Sampling box

Oven trays

Plastic bucket

Sampling scoop

Procedure

A representative sample of material to be analyzed shall be taken in a proper sapling method. The sample shall be at least 1500 grams.

The sample shall be weighed and the weight recorded. After weighing the sample shall be oven or gas ring dried making sure that none of the sample is spilt from the heating tray.

After drying the sample shall be passed through a set of known mesh size sieves, making sure that all the sample is removed from the heating tray. The sieves shall be interlocked in order of aperture size, starting with the larges mesh size at the top.

The interlocking sieves (including bottom pan) shall be agitated sufficiently (normally with the aid of mechanical vibrator/shaker) for a period of time (usually 4 minutes minimum), to ensure that the material has completely passed through the respective grade sizes.

The aggregate which is retained in each of the sieves and the bottom pan are then individually accurately weighed and the weights recorded.

Calculations

After the mass of aggregate retained on each sieve and in the receiver has been determined, calculations are then carried out. Note that mass retained and mass passing on each sieve are recorded and percentage passing is eventually calculated from the obtained results.

Visual representation of the particle size distribution is carried out be means of gradation graph showing the sieve aperture size against the percentage passing that particular sieve size.

Due to the relative values of the aperture size, it is convenient to plot them to a logarithmic scale.

On completion of plotting, the points of the plot are joined together with straight lines resulting in a graph that is termed the gradation curve.

Evaluation of results

The obtained grading curve should be within the envelope limits drawn by the applicator and approved by the client and/or limits extracted from the ASTM C33 Standard.

Report

The type of aggregate

Results and percentages calculate

                                                 Sieve Analysis

           

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MOISTURE CONTENT OF AGGREGATES

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

Scope

Determination of the mass of water in an aggregate, expressed as a percentage of the mass of the oven-dry, sample material.

Equipment The moisture content can be determined by any one of two methods.

An oven or gas ring

A calibrated weigh scale

Oven pan

“Speedy” moisture content tester (alternative method)   
   

Procedure & Calculation (oven/gas ring dried method)

The sample is weighed, and then, after being oven- dried, it is re-weighed. Weigh the masses before and after drying W1 and W2, respectively, then:

Moisture content, % = (W1 – W2) / W2 x 100

Use of “Speedy” moisture content tester (use only in case of accelerated test)

This is a proprietary device whose action is based on the very rapid absorption of water by calcium carbide. Standardized quantities of aggregate and calcium carbide are mixed by a standard procedure in a hand-held, sealed pressure vessel. Acetylene gas is formed by the action of the moisture on the calcium carbide, and the pressure of the gas is related to the quantity of moisture. The vessel is fitted with a pressure gauge calibrated to give a direct reading of the moisture content.

Note : This test is unsuitable for larger sizes of coarse aggregate.


Report

Moisture Content in %

 Moisture Content

 

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DELETERIOUS SUBSTANCE IN AGGREGATES - ASTM C40-92

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

Scope

To determine the organic impurities, including silt and clay in the aggregates

Apparatus

Glass bottle, 500ml

Sodium hydroxide solution, 3% NaOH

Reference color standards

Procedure (extract from ASTM C40-92)

Preparation of solution :

Dissolve reagent grade potassium dichromate (K2Cr207) in concentrated sulfuric acid (SG 1.84) at the rate of 0.250 g/ml of acid. The solution must be freshly made for the color comparison by gently heating, if necessary, to effect solution
.

Fill a glass bottle to the 130ml level with sample of aggregate to be tested.and add the 3% NaOH solution into the bottle until the volume of the aggregate and liquid after shaking is about 200ml.

Cork the bottle, shake it vigorously and allow it to stand for 24 hours.afterward fill a fresh glass bottle to the 75ml level with reference standard color solution prepared not more than 2 hours earlier per the preparation procedure described in Sub-clause B.3.1

Compare the color of the supernatant liquid of the test sample with that of the reference color solution.

Record the color comparison result to that of the reference standard, e.g. lighter, darker or same color.

Evaluation

If the color of the supernatant liquid is darker than that of the referenced standard, the aggregate tested is considered to contain possible traces of injurious organic compounds. As such perform further tests.

Report


Record

Deleterious  Substances            

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FRESH ANALYSIS

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

Scope

To verify W/C ratio, cement and aggregate content of the concrete mix. This procedure applies to fresh concrete coating drawn from the batching mixer or feed conveyor to the application head. 

Equipment  
    

Set of test sieves

Mechanical sieve shaker

Calibrated Electronic balance to an accuracy of 1.0g

Gas ring (to accelerate drying)

Bucket

Gunny sacks

Procedure

Prior to carrying out a mix analysis, it is necessary to carry out a gradation on a representative sample of each aggregate used in the concrete. It is also necessary to know the nominal mix design in percentage terms.

Obtain a representative sample of at least 2kg of freshly mixed concrete from the feed belt, place in a suitable bucket , cover the bucket with a damp gunny sack and immediately transfer the sample to the laboratory. This test shall be carried out without any delays.

Weigh a 500g sample into a tray and determine the moisture content of the sample.

Weigh a further 1,000g into a 150 micron sieve. Wash this sample carefully under a gentle flow of clean water until the water draining from the sieve is clean and clear. Be very careful to ensure that no material spills over the side of the sieve.

When washing is complete, transfer the cleaned sample onto a tray, using a further quantity of clean water to wash all traces of material out of the sieve and into the tray. Carefully drain off excess water, making sure that no material is lost in the process.

Place the tray over a burner and dry it thoroughly. Ensure that the rate of drying is gentle enough to prevent material being ejected from the tray as the water vaporises, or alternately cover the tray with an identical tray to trap any ejected material.

Once the sample is completely dry, remove from the heat and allow it to cool before transferring to the sieve stack.

When the sample has been placed into the sieve stack close the sieve stack securely and operate the shaker for five minutes. Remove the stack from the shaker. Carefully separate the nested sieves and weigh and record the amount of material retained on each sieve, ignoring the contents (if any) in the sieve pan.

Input the weights into the pre formatted calculation spreadsheet, or alternatively write by hand on a blank fresh mix analysis form. For manual calculation, the procedure is as follows:


Record the weight on each sieve in turn
Determine the cumulative weight retained on each sieve by adding the weights of all
previous sieves in the stack
Determine the dry weight of the 1,000g sample used for each sieve
Calculate the cumulative weight retained as a percentage of the sample dry weight
For each sieve, calculate the percentage of the dry weight passing that sieve by subtracting
the value from the previous step from 100%

The preformatted spreadsheet automatically calculates the mix ratios. To do this manually, the following procedure is used:

Determine the weight of fines ( < 150 micron) particles of each aggregate in the mix sample by multiplying the percentage of that aggregate passing the 150 micron sieve (from the aggregate gradation) by the percentage of that aggregate in the mix by the dry weight of the fresh mix sample.

Example: If 15% of the sand passes the 150 micron sieve in the sand gradation, and the mix design incorporates 20% sand, and the fresh mix sample weighs 1,000g with a moisture content of 6%, then the weight of sand fines in the sample is:-

15% x 20% x (1,000 x 94%), or 0.15 x 0.2 x 1000 x 0.94 = 28.2g

Repeat this step for each aggregate, and total the weights determined in this way. This gives the total weight of fines in the fresh mix sample.

From the fresh mix gradation, calculate the total weight passing the 150 micron sieve by subtracting the cumulative weight retained on that sieve from the dry weight of the sample. This is the apparent weight of cement in the sample.

Note, this weight will include fine particles of aggregate. Subtract from it the total fines weight calculated previously. The result is the corrected weight of cement.

Subtract the corrected weight of cement from the dry weight of the mix sample. The result is the corrected weight of aggregate.

Determine the weight of water in the sample by multiplying the sample wet weight by the moisture content.

The water to cement ratio is given by dividing the weight of water by the corrected weight of cement.

The aggregate to cement ratio is given by dividing the corrected weight of aggregate by the corrected weight of cement.

Report

Record  


Fresh Analysis

Fresh Analysis

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CONCRETE DENSITY

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

Scope

To determine concrete density on removed samples (coupons or cores) removed from a concrete coating.

Equipment

Balance sensitive to 1.0g

Container suitable for transporting coupons to lab/cure bay

Core drilling equipment (core sampling)

Hand tools to assist in removal of samples

Wire cutters (coupon sampling)

Test specimen

Draw specimen (coupon) at production line taken immediately after coating or from a cure pipe (core) dependant on the agreed method of sampling.

Procedure (coupon method)

Brush the sample with a fine bristle brush to remove all loose particles from the sample surface.

Weigh sample and record as Weight A. 

Transfer the sample to pipe curing bay with the pipe and allow the sample to cure for the same period of time as of  the coated pipe (a minimum of four (4) days). Sample may also be oven dried to the constant weight.


Procedure (coupon and core)


After cure immerse sample in seawater filled tank at room temperature for not less than 24 hours. Draw sample from tank, let it surface dry or remove excess surface moisture, weigh and record as Weight B.


Suspend the sample from a wire and weigh it in water and record as Weight C (this is to check bulk density of concrete).


With the weights determined in accordance with the above procedures, calculate the following:


a) Water absorption after Immersion, % = (B – A) / A x 100
b)  Density (Air- dry), Kg/m3        = A / (A – C)
c) Density (Saturated), Kg/m3     = B / (B – C)

Report


Record

Sample ID

Concrete coating date

Sample type

Calculation and results

Density

                                         Density Test

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COMPRESSIVE STRENGTH OF CUBES

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

Scope

Preparation and testing samples of concrete for compressive strength properties using the cube mold method of sampling.

Equipment

100mm Cube Molds

Trowel

Bucket or Container

Vibrating hammer complete with square face (50mm x 50mm) tamping foot

Calibrated Compression Testing Machine.

Procedure

Draw concrete samples of the production working mix from the conveyor during transfer of concrete from the mixer to the application head. Ensure that only freshly mixed concrete is used for the sampling.

Place sample material in a bucket and over the bucket with a moist gunnysack to prevent premature dehydration of the sample.

Prepare the required amount of cubes required for each sampling period plus two extra cubes to used as spares. Make the test cubes as soon as practicable after sampling to avoid dehydration.

Fill each test cube mold with concrete in three layers of 50mm. Compact each layer until refusal using a vibrating hammer equipped with a square faced tamping foot attachment.

On completion of compacting the topmost layer of the sample the surface shall be prepared level with the top edges of the mold using a square edged trowel. Each sample shall be marked with it’s ID and sample number. Also for day night operations the ID should include the letters D/S or N/S

Curing of sample

Immediately after the sample preparation, cover the molds with a moist gunny sack and place the cubes in the fog cure. Check closely that an uninterrupted moist condition exist throughout the curing period.

After overnight curing, the mold screws are loosened, the mold dismantled and cube sample is carefully removed and placed in a water tank. The samples shall remain saturated until required for crushing.

Note : ensure that before placing the samples in the water tank that a correct, legible ID exists on each sample

Compression Testing

The testing machine shall be capable of applying load manually or automatically at the specified rate uniformly without shock. It should be annually (or anytime when anomalies in the results are
observed) be calibrated and certified by 3^rd Party Certifying Agency for compliance.

Prior to testing each sample shall be weighed (in saturated state), in kilograms.The dimensions of the samples shall be measurement in mm.

Determine the density of each test cube either by obtained weight over cube measure or by water displacement method.

After weights, measurements and densities have been determined the test cube shall be placed between the testing machine platens ensuring that all bearing surfaces of the testing machine platens and the sample are wiped free of any debris.

Carefully center the cube on the lower platen, ascertaining that load will be applied to the two opposite cast faces of the cube in a correct and even manner.

Without shock, apply and increase the load continuously at a nominal rate within the range of 0.2 - 0.4N/mm per second until no greater load can be sustained.

Record the maximum load applied to the cube.

Calculation and expression of the results

Calculate the cross-sectional area of the cube face from the checked nominal or measured dimensions.

Calculate the compressive strength of each cube by dividing the maximum load by the cross-sectional area of cube.

Express the results to the nearest 0.5N/mm2 or any otherwise agreed units.

Report

Record
Concrete Compressive Strength (Cube Sample)    




NOTE : The drawing and Test on drilled CORES is in accordance with BS1881 Part 120. Cube: Core Compressive Strength Correlation (if required) is carried out by this standard 


Compressive Strength Cubes


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COMPRESSIVE STRENGTH OF CORES - BS1881

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

Scope

Preparation and testing samples of concrete coating for compressive strength properties using the extracted core method of sampling.

Equipment

Core drill, support stand and correctly sized core bits

Calibrated Compression Testing Machine.

Facing saw                   

External calipers

Acetate film

Capping compound

Bucket, Container or plastic bags

Water & Power source

Procedure

Pipes selected during production for core sampling shall be clearly marked “CORE TEST” and the pipe number and date coated shall be entered into the laboratory “LOG”

After a curing period (minimum 48 hrs) the core test pipe shall be located in the designated area for core drilling. The core drilling equipment shall be checked for good working condition and properly connected to the power source. The core drill bit shall be of a size that will allow 35 – 45 mm diameter cores to be removed. Core diameters shall remain constant throughout the project. Only suitably qualified/trained operators shall perform core drilling.

The core drilling rig shall be firmly located on top of the pipe ( 90°) and the core drilled in a downward direction. Whilst drilling, water shall be used to lubricate the drilling bit and the core rig shall be fitted with a positive stop system to ensure the core bit does not exceed the limitation of penetration (being  7 mm from the PE coating). Core samples shall NOT be taken from the end 300 mm of the concrete coating.

On completion of drilling, the core drill, including core shall be carefully removed from the concrete coating.  The core sample shall then be carefully removed from the drill bit. When removed, all cores from the test pipe shall have a band of electrical tape fastened around them on which the pipe number shall be marked using a ball point pen. The cores shall be placed in unique plastic bag for each test pipe. DO NOT MIX CORES FROM OTHER TEST PIPES. The bag containing the cores shall also be clearly marked with the test pipe number.

When received at the laboratory the cores shall be removed from their respective  bags and checked for condition and quantity. If more cores are required, advise the core man as soon as possible. All cores are to be trimmed and left to dry for 24 hours. When dry, the cores shall be capped (apart from cores that will be used for density and water absorption tests). These cores will be capped later. When capped, each core top cap shall be identified with the date coated and with the letters D (day) or N (night) and placed into the storage tank with the identification facing upward. The same procedure will apply to density and water absorption samples after tests are complete. Cores will be stored in a water tank maintained at 23 ± 2°C.

Crushing

Specimens shall be removed from the curing tank and shall be in saturated condition when tested, ideally removed from the tank approximately 30 minutes prior to crushing.

Select appropriate testing machine platens to suit anticipated compressive force. Clean platen surfaces and ensure absence of extraneous matter. The core-seating rig (if required), fabricated in accordance with BS 1881, is placed in the centre of the location circle and the cores inserted.

Apply the load, without shock, at a nominal loading of 0.2 N/mm2/sec. - 0.4 N/mm2/sec. at a constant rate for cores. Observe the fast advance and ensure seat correctly on the apparatus. Operate the controls as failure is approached to maintain load rate(s) above as far as practicable. When failure occurs the maximum load applied shall be recorded.

Report

Record

The specimen ID

Pipe number

Compressive strength to the nearest 0.5 MPa

Core Samples

Core crushing

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WATER ABSORPTION

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

Scope

Determination of water absorption on sample removed from concrete coating (coupon or core)

Determination of water absorption using a fully coated concrete pipe (full-scale method)

Equipment   
            

Test Sample

Calibrated Balance

Container suitable for immersing sample

Fresh concrete sample (at least 500 grams)

Full Scale

Calibrated weighbridge or load cell

Suitable water tank

Crane

Procedure (Sample testing)

Brush the removed sample (coupon or core) with a fine bristle brush to remove all loose particles

from the sample surface.Weigh dry sample and record as Weight A. 

Transfer the sample (coupon) to pipe curing bay with the pipe and allow curing for the same period of time as the coated pipe.

Immerse sample in seawater tank at room temperature for not less than 24 hours. Remove the sample from the tank, let it surface dry or remove excess surface moisture before weighing and record as Weight B.

Suspend the sample from a wire and weigh it in water and record as Weight C (this is to check bulk density of concrete).

Calculate the water absorption of the sample as follows:

a) Absorption after Immersion, % = (B – A) / A x 100

Calculate the bulk density as follows:

b) Bulk Density (Air- dry),           Kg/m3 = A / (A – C)………  IF REQUIRED

c) Bulk Density (Saturated),       Kg/m3= B / (B – C)……….. IF REQUIRED

Procedure (Full scale method)

Weigh a fully concrete coated pipe that has been cured record as weight A.

Place the pipe in a water tank filled with seawater at room temperature, if fresh water is used a

calculation between sea and fresh water shall be used in the calculation process.

Allow the concrete to fully saturate, normally 24 hrs

After 24 hrs remove the pipe from the water tank and allow all free water to drain off. Weigh the

pipe and record as weight B

Calculate the water absorption of the concrete coated pipe as follows;

Absorption after Immersion, % = (B – A) / A x 100

Report

Record

Sample(coupon)

Full scale water immersion

Water Absorption sample

Water Absorption test

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IMPACT TESTING OF CONCRETE

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

Scope

This procedure applies to concrete coated pipe subjected to repeated Impact simulating the pipe movement during transportation and handling at lay barge during installation.  It is carried out to determine concrete integrity when subjected to high impact energy.

Equipment

Impact testing rig

Test Pipe with concrete coating

Timer

Tape measure

Striker edge: 10mm radius

Hammer Weight 2,680 Kg and/or 1,840 Kg

Camera

Procedure

The test shall be carried out 90° to pipe axis at one location.

The test shall be supported with a minimum of 2M concrete sections on either side of the section under test.  Impact blows (5 times) shall be directed on the same location. Hammer should have a vertical drop of 660mm giving a velocity of impact of 3.60 m/second (7 Knots).

After each impact a photograph of the impact area shall be taken together with a sketch of spalled areas including dimensions of cracks (length and width).

Acceptance criteria:-  Typically

The anti- corrosion coating shall not be visible after impact (5 blows).

Spalling has not occurred further than 300mm from the impact location.

Report

Record
Impact Testing of Concrete

Impact Test Rig Drawing

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SHEAR TEST OF CONCRETE

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

Scope

To evaluate the inter facial shear strength between the anti-corrosion and concrete coating applied to a pipe.

Equipment (typical)

200MT Hydraulic Jack complete with pressure gauge

Supporting fixtures (design to suit testing set-up)

Measuring gauge for displacement of upper platen

Calibrated dial gauge

Procedure

A pre prepared coated section of pipe shall be selected having concrete pipe sections of minimum of 500mm test length. The preferred maturity of the coating is a minimum 7-days after coating.

Oxy cut from a cured concrete coated pipe approximately 900mm concrete coated test pipe. Cut only one test piece from each individual coated pipe. Alternatively, pipe can be coated partly at a section length of 0.50 to 0.90 meter located at one end of pipe (proximity to cutback). This is depending on what fixture is available from the time of carrying out test.

After having cut the test piece, prepare the cross-sectional surface of the concrete at one end so that it is near perpendicular to the axis along the piece length.

Carefully center the test piece on the lower platen of the Hydraulic Jack (Compression machine) unit with the concrete section supported by the appropriate supporting fixtures. Then slowly lower the top platen to just touching the steel pipe end. Without shock, apply and increase the load continuously at a nominal rate within the range of 0.2N/mm2 per second until no greater load can be sustained.

Record the maximum load applied and calculate the surface area (SA) of the anti- corrosion coating surface as follows:

Surface area, mm2 = 3.1416 x d x L

Where,

d  = Pipe OD + anti-corrosion coating thickness

L = Length of concrete coating

Minimum required load (Kg-f) = 0.17N/mm2 x SA / 9.81

Report 

Record
Shear Testing results 
                                                                   Shear Bond Test

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