GPS control survey for Inertial Measurement Unit (IMU) in pipeline detection tool.

Using GPS, we measure traps, welds and control points along the pipeline in order to correct the IMU drift. This correction is done through in house software. This method will minimise dig time and costs when locating the defects and anomalies.

Merrett Surveys have worked for a wide variety of pipeline inspection companies including GE â?? PII, Baker Hughes (including the former Weatherfordâ??s pipeline division), Rosen and TD Williamson, plus pipeline operators such as BP, Exxon, OPA, British Gas and many more.


Merrett Surveys have vast experience providing GPS surveys for AGM (Above Ground Marker) locations associated with IMU based pipeline mapping. We have skills to optimise the accuracy of your mapping system. Detailed reports enable crews to set out AGM's accurately and swiftly.

Peter Merrett has presented papers at International Pipeline Conferences on the subject of â??Optimising the accuracy of IMU based pipeline mappingâ?. We also provide training courses for data processors on Geodesy and GPS.

Field mapping required before the design of oil, gas and petroleum pipelines is a service we also provide. We can do this using aerial mapping with photogrammetry or airborne laser scanning - Lidar, or ground based in field GPS or DGPS methods.

We use the latest technology such as SmartNet, this Real Time Kinetic Network allows for faster processing times whilst maintaining accuracy. We have experience of using GPS worldwide, our most prestigious project to date has been to assist the UN with defining the International Boundary between Nigeria and Cameroon. We specialise in the provision of GPS and survey support for pipeline mapping projects worldwide.

Prior to (or after) construction of a pipeline, an airborne LiDAR survey allows for the identification of off-line concerns such as rivers, streams, ditches and buildings and provides an accurate portrayal of ground conditions along the pipeline.

We also provide terrestrial laser scanning services, often used in oil and gas plants for clash detection.

GPS services for pipeline mapping

We carry out pipeline asset surveys and can incorporate this data into a GIS for a variety of uses such as class location risk analysis. This work is often generated through pipeline safety regulatory requirements, necessitating in-line inspection, integrity analysis and risk assessment. Many pipeline operators use GIS for managing their assets, planning mitigation strategies, and developing integrity plans. Pipeline mapping provides the data for the GIS, and it is vital that field data collection is completed in a reliable and accurate way.

The pipeline mapping work is a vital part of any pipeline integrity management scheme. For pipeline operators working in USA, it will help compliance with DOT regulations such as "the Pipeline and Hazardous Materials Safety Administration's Rules on Pipeline Integrity Management in High Consequence Areas for Hazardous Liquid Operators (49 CFR Part 195)."

Our in-house software classifies the pipeline automatically using the rules laid out in either 854.1(c) in ASME B31.8 or the UK equivalent, IDE/TD/1. The software solution aids in determining class locations by analysing the number and type of buildings and population density within a certain proximity to the pipeline.

This is an aspect of your integrity management planning where we can streamline your analysis and save you time and money. Our solutions help to enhance safety and environmental protection.

Our class location program segments the pipeline according to the density of inhabited or publicly used structures nearby.

A high number of residences or high-occupancy buildings (such as schools, restaurants, or multi-story buildings) near the pipeline will result in the pipeline segment being given a higher numbered class.

The acceptable limits for numbers of houses and other infrastructure in the vicinity of a pipeline subsequent to initial construction are given in Table 854.1(c) in ASME B31.8 (UK equialent is IDE/TD/1).

The wall thickness and other operating parameters (such as MAOP) will also determine the class assigned to a pipeline segment. A pipeline segment with a high class location is probably passing through a highly urbanized area, and thus it should have a higher wall thickness for example.

Our classification program utilises disparate data sources including:

• PIG data
• Surveyed data
• Paper maps from planning office
• DXF files from planning office
• Satellite / Aerial Photography
  

By using GIS we can help identify parts of your pipeline which are subject to more rigorous regulation â?? helping to keep operating costs low while ensuring that the pipelines are operating as safely as they should.
By classifying the pipeline we can identify areas where pipeline needs to be thickened or diverted. Updating assets and features near to the pipeline provides information to asses the need in some cases to re-route to avoid areas of dense population.

In calculating the design pressure of a pipeline which is being considered for uprating, it is necessary to assess the current Location Class of every point on the line, and to use this Location Class in the calculation of the design pressure, rather than the Location Class at the time of construction. Where the Location Class has altered over time, due to the construction of additional housing or other infrastructure, this may be an impediment to uprating.

We have developed a method of 'mapping' pipelines from the surface without the use of an IMU (Inertial Measurement Unit). Measuring the buried pipe from the surface we can create a full 3D model of the pipe. Using specialist software that we have developed, we can then adjust your MFL inspection data onto the 3D pipe and thus provide every weld, feature and defect of the pipe with full 3D coordinates. This method has proved to be extremely accurate (exceeding IMU accuracies).

Having merged your MFL data to provide accurate co-ordinates of every anomaly and defect, we can then stake out those defects for you - saving time and cost on repair and investigative digs and excavations.

We provide pipeline asset surveys and can incorporate this data into a GIS for a variety of uses such as class location risk analysis.

    
Our surveyors walk the pipeline route mapping features for integration into GIS. Data collected includes:

• Buildings- use, construction materials, occupancy
• Transport features (bridges, roads etcâ?¦)
• Drainage features, erosion featuresâ?¦that pose a risk/threat to the line.
• Information on planned/future developments is obtained through interviews and visits to local planning office.
• Vegetation and other miscellaneous features.
• Each surveyed point has an associated photograph and attributes associated with the point can be assigned. The attributes recorded have an influence on determining the classification of the pipeline.
  

Thorough data collection includes combining surveyed asset information with other data sources such as aerial mapping and three dimensional Digital Terrain Models (DTM).

A three dimensional Digital Terrain Model (DTM) is useful for modelling overland flow in the event of a failure in an oil pipeline. High quality DTM's can be created from an airborne LiDAR survey

A LiDAR survey will provide a DTM with a grid spacing of 0.5-1m allowing for the identification of micro terrain features that may channel the oil flow into a narrow width even on a steep slope. This channeling and modelling thereof is especially useful in determining whether oil flow would infringe upon a High Consequence Area (HCA).

Aerial photography combined with a 3D DTM will provide up to date land classifications, show areas of dense foliage which will reduce oil mass, illustrate areas where oil will pool and even indicate soil type.

Accurate mapping from LiDAR and photogrammetry can provide information for geologists and engineers to add additional data while planning safe and efficient pipeline corridors. High quality, accurate mapping allows our clients to design cost effective access routes.

Accurate Ortho-rectified imagery can aid in understanding location and extent of wildlife habitats, the location of existing roads and tracks, which can aid in ascertaining the optimal location for new construction and maintenance roads.

From the LiDAR we can create 'Bare Earth Models', these can be used to aid in determining the best locations for the pipeline and aid in geotechnical analysis. The elevation map can ensure that the pipeline route is planned to be as level as possible. LiDAR can also be used to understand vegetation and tree height as well as density and proximity to the route of any proposed pipeline route. Some of the LiDAR energy will penetrate the foliage, allowing us to map the ground underneath as well.

LiDAR can aid in the evaluation of prospective sites, a LiDAR survey can include aerial photography and provide digital elevation models, contours, slope and aspect maps that can be incorporated into a GIS package,

LiDAR has the advantage of 'seeing through the foliage' to map the ground even in rainforest. A LiDAR survey can aid in pre-planning, identify staging areas, position construction crews to work in downhill directions, logistic planning and safety planning.

For a large project in Algeria we assisted the client with a LiDAR survey for a seismic project where we delivered seismic line profiles that were used to determine elevation changes and slope.

The video shows a laser scan survey of a storage tank with visible shell deformation. We are able to accurately report and monitor the â??out of roundnessâ?? of the storage tank. 

By â??unfurlingâ?? the tank shell, we can create difference images and contours to show areas of deformation. Dents are coloured blue and bulges are coloured red. Areas where the there is no deformation are coloured green.

Tank settlement can cause various changes to the shape of the bottom shell and can tilt the tank in certain circumstances. Our strapping tables not only incorporate accurate circumference and height measurements but also all internal â??deadwoodâ??. 

Advantages of using laser scanning for complex plant, e.g. offshore platforms, oil and gas, chemical plants, power stations, refineries, storage tanks etc..

â?¢ Carry out comparisons between existing and proposed installations - clash detection analysis
â?¢ Lower design costs
â?¢ Higher level of detail and greater completeness
â?¢ Safer data capture, the scanner can be remotely operated in hazardous environments
â?¢ Unobtrusive (non-contact) data capture
â?¢ Point clouds can be conveniently used and reviewed by others for more efficient project management

Efficient and complete data capture

Traditionally, information would be gathered with manual measurements and reference to original design and construction drawings. This work is time consuming and prone to error. Terrestrial laser scanning can eliminate these problems.

Each laser scan takes between 3 and 15 minutes, data capture is therefore very fast and accurate to millimeters. Traditional surveying is based on discrete data point observation, terrestrial laser scanning captures the complete asset. Thus, there is a significant improvement in the level of detail and accuracy of the raw data plus a more extensive range of possibilities for data analysis and use. The need for return to site visits are also reduced.

Merrett Surveys have wide ranging experience of topographic surveys for new pipeline routes and diversions. This includes river crossings, rainforest, temperate and desert climates.

In preparing a preliminary route map, survey data needs to be gathered in order to produce construction alignment sheets, permit drawings, easement plats and engineering detail design drawings. An as-built survey should be carried out during construction of the pipeline so that the exact location of the pipe can be recorded and the data used to prepare the final as-built drawings.

Merrett Surveys professional surveyors have vast experience in pipeline surveys and use the latest technology, including EDM total stations, double depth pipeline detection equipment, GPS and terrestrial laser scanning. Our experienced surveyors gather survey information and record attributes such that they can be used in any CAD and GIS programs.

We provide:

• GIS asset data collection surveys to aid in determining the route of a new pipeline.
• Airborne LiDAR surveys to collect wide area topographic terrain maps.
• Boundary and topographic surveys.
• As-built surveys and stake out for construction.
• River crossing profiles to monitor erosion rates etc...for hydrographic modelling.