Pipeline pigging and bolt torquing and tensioning
GAUGING
The purpose of this operation is to prove the continuous diameter of the pipeline, i.e. the absence of any significant dents, ovalities or defects caused during the construction phase. This process also gives a baseline for the pipeline at the date of construction.
After completing the pipeline cleaning operation during which the usually debris (welding rods, mud etc…) have been removed out of the pipeline system, the gauging operation will take place in order to ensure a successful flooding and hydro test operation. In general, the purpose of this operation is to prove the continuous diameter of the pipeline, i.e. the absence of any significant dents, ovalities or defects caused during the construction phase. This process also gives a baseline for the pipeline at the date of construction.
Therefore, the same temporary low pressure header, as used for the cleaning activity previously, will be loaded with a standard bi-directional pig equipped with an aluminum plate (a gauging plate) normally machined to a pre-set tolerance diameter between 95% and 97% of the pipeline inner diameter (ID). The pig and plate have to be uniquely identified and marked (numbered and dated) for direction of travel. Prior to the launching, and upon receipt, the pig will be visually inspected and full details noted on a checklist, which will be submitted for approval to the client.
Any damage to the gauging plate is an indication that there is a reduction of diameter (dent, ovality etc…) in the pipeline system that will need further investigation. In this case, a second gauging run will be carried out to confirm the results from the first run. After the second run and confirmation of damage it may be decided to run a caliper pig to obtain more detailed information regarding the position and nature of the deformation.
CALIPER SURVEY / ELECTRONIC GEOMETRY GAUGING PIG
Geometric deviations of pipe bore are physical defects which have a serious impact on the lifetime and the safe operations of the pipeline. Those deviations are caused in most cases by mechanical impact.
Dents affect the safe operation of a pipeline as they affect the flow of the transported medium and tend to create spot-like formations of sedimentation, turbulence, erosion, corrosion, and hydrates. The pipeline’s service life is shortened further by localized excessive mechanical stress.
Geometric deviations can be located and their dimensions determined by the caliper-tool. Its use now forms an integral part in the acceptance of new pipelines and the monitoring of pipelines in operation. The calliper-tool works during the normal operation of a pipeline and is propelled through the line by the transported medium.
The caliper-tool’s purpose-adapted structure meets even extreme conditions for operation in pipelines. The caliper-tool is able to pass extreme deformations (up to 25 %) and due to the large number of sensing fingers (34), even the smallest dents can be detected. In order to avoid speed cycling, the polyurethane cup sleeves are designed for easy running. For inspection of long-distance pipelines, a large data storage system has been designed for pipelines up to a length of 500 km. A battery life of 500 and more hours together with the sleep mode option also facilitates operation when the caliper-tool has to wait several days either in the launcher before starts of pumping or at any position in the pipeline due to interruption of pipeline operation.
Preliminary data evaluation and listing of the defects will be made with a laptop PC on site immediately after the inspection run to ensure that quick decisions for subsequent actions can be made as quick as possible
PIPELINE PIGS
pipeline pigs for specific applications, such as liquids displacement, cleaning, batching, gauging, and specialty pigs, available in diameters up to 60-inch and ranging in aggressiveness from firm urethane to steel wire brushes. Customization and configuration options ensure tailored solutions for even the most complex pipeline conditions.
The pipeline services provided by ProtechPPS, are applicable for onshore and offshore pre-commissioning, chemical cleaning, caliper survey, leak testing, pipeline inspection, rehabilitation, maintenance and other related services. ProtechPPS is a leading pipeline solutions provider with know-how in engineering, project management & with range of high-performance assets.
Cleaning
After completing pipeline construction works the usual debris (welding rods, mud, etc…) has to be removed from the pipeline system in order to ensure a successful gauging and flooding pig run. Therefore a temporary low-pressure launcher header and a low-pressure receiver header have to be installed or welded to the pipeline ends. Those headers are equipped with back doors which will allow inserting and removing an unlimited number of pigs. This is necessary to ensure a continuous operation. Usually, there are two different kinds of cleaning pigs: brush and magnet equipped bi-directional pigs.
Immediately prior to launching, and upon receipt, each pig will be visually inspected and full details noted on a checklist, which will be submitted for approval to the client. Each pig has to be uniquely identified and marked for the direction of travel. The cleaning pigs will be propelled by compressed air and the runs will be repeated until the debris removed from the pipeline is reduced considerably and accepted by the client. Therefore all debris recovered off the pigs, from the pigs, or within the pig traps shall be monitored, measured, and recorded. The debris removed from the pipeline shall be safely disposed of at the location approved by the client and local authorities.
FLOODING / FILLING
In order to demonstrate the strength and integrity of the pipeline, it is filled with water and pressure tested. The air must be removed so that the line can be pressurized efficiently because, if pockets of air remain these will be compressed and absorb energy. It will also take time to bring the line up to pressure and be more hazardous in the event of a rupture during the test. It is, therefore, necessary to ensure the line is properly flooded and all of the air displaced.
After completing the pipeline cleaning and gauging operations, the usual debris (welding rods, mud, etc…) has been removed from the pipeline system. The flooding operation will start in order to ensure a successful hydro test operation. Therefore temporary high-pressure launcher header and high-pressure receiver header have to be installed (welded or flanged) to the pipeline ends. Usually, those headers are equipped with three bi-directional standard pigs, of which two of them will be used for the flooding operations. The third pig will be used as a contingency pig. The flooding will be performed by using freshwater/seawater. Brackish water which will be chemically treated can also be used to fill the pipeline.
The quality of the filling operation is critical and it usually requires that the fill water is filtered (50micron) and the content of air is less than 0.2% of the pipeline volume after the finish of the flooding operation.
In order to meet those specifications, a filtration unit (20 to 50 microns) will be used. Regarding air content (less 0.2% air), the pig speed is a major consideration of the pipeline flooding. Usually, the pig speed shall be not less than 0.1m/s and sufficient pumps and spare capacities will be required in order to ensure a successful flooding operation.
PIPELINE INSPECTION
The inspection survey shall be conducted to control corrosion growth in the pipeline. Pipeline inspection is carried out by the use of Magnetic Flux Leakage (MFL) and Transverse Flux Induction (TFI) tools.
The MFL inspection tools induce a magnetic field along the pipe by means of permanent magnets, sensors fitted to the tool. Covering the full circumference of the pipe, the magnets and sensors measure and record leakage and disturbances of the magnetic flux induced.
The data recorded is then interpreted using a specific analytical IT software to analyse the position, depth and sizes of pipe anomalies such as:
MFL / TFI Inspection method statement: To complete the pipe inspection by means of intelligent pigging, the process should be completed after the commissioning, as soon as a suitable pressure and flow parameters are available, to allow for a full data collection.
MFL/TFI Run: The MFL / TFI inspection pig will be mechanically and electronically prepared and calibrated at the production base of ROUGE-IP sub-contractor, prior to its mobilisation based upon the pipeline specifications and details supplied by the client.
Upon arrival on site, mechanical checks and commissioning are performed. This sequence is followed by an electronic calibration and commissioning. At this point the pig will be ready to be launched in the pipeline. The MFL/TFI intelligent pig is propelled through the pipeline, at a velocity comprised within a range of 0.5m/sec to 0.9 m/sec, by filtered water as medium.
Following its reception at the end of the line/section, the intelligent pig is moved to a suitable covered area with power supply and is mechanically checked and the data download process is started.
A preliminary review on the data will allow check potential discrepancies between the pipeline specs available information and the data collected by the intelligent pig. Within 36hours following the arrival of the intelligent pig, an inspection run report is issued and signed by Rouge LLC – Pipeline Services infield staff. This report will confirm suitability of data for report production and provide with details of any data loss, mechanical damage, details of distance measured and data quantity. Any missing or degraded data is reported to the client for approval before the drafting of the final report. Data will be dispatched for inspection report production at sub-contractor company headquarters.