We measure and calibrate tanks of various shapes, sizes and designs,
including tanks that hold crude oil, refined petroleum products, LPG,
LNG and other wet or dry bulk products.
Our comprehensive reporting includes calibration tables, tank
deformation analysis, storage tank tilt, subsidence, volumetric
analysis of containment dykes and more...
Our surveyors use the latest laser scanning technology, providing fast and accurate results.
High accuracy laser scanners and Optical Distance Measuring instruments
From the deserts of Algeria and Oman to snow covered Greenland, we can survey in all conditions.
High accuracy strapping tables & deformation analysis.
We specialise in analysing storage tanks and provide highly accurate strapping tables, shell deformation analysis, surveys for tank bottom and foundation settlement, shell roundness, structural column verticality, and more. By providing a geometric evaluation of the tank in its current state, we can provide 3D models and layout drawings of the floor, shell, roof structure, and attached infrastructure. This data can assist with assessment of tank integrity, risk analysis, design of floating roofs and ensuring they fit, and much more.
Our storage tank calibration services are designed to meet (or
exceed) the standards published by the American Petroleum Institute
(API) or by the International Standards Organisation (ISO).
Volumetric tables can be customised according to your requirements and we can analyse tanks of all shapes and sizes.
We can create the strapping tables using conventional survey equipment, or we can create them using the latest laser scanning instruments. Laser scanning can provide a more complete survey for creating highly accurate strapping tables which not only incorporate accurate circumference and height measurements but also all internal deadwood.
Our bespoke software, developed specifically for creating tank volume tables facilitates the creation highly accurate strapping tables. For high value products, it pays to have accurate volumes.
Storage tanks require periodic surveys to monitor long and short-term movements, settlements of the foundation and other deformations such as tank shell deformation due to oil pressure for example.
The video (left) shows a storage tank that was surveyed with a laser scanner to monitor shell deformation at different levels of fill. The coloured deformation map shows inward and outward deformation (red areas show outward deformation and blue areas show inward deformation). As expected, we can see that the tank shell bows outwards when fully filled with oil. It is necessary to monitor and analyze the deformation so as to ensure safety and security.
The data can be presented in different ways. We can tailor reports to your needs by producing Excel radial displacement graphs, creating cross sections in AutoCAD or issuing deformation image maps. Traditionally, we would monitor the tank by measuring the location of studs positioned around the top and bottom of the tank. The advantage of laser scanning is that instead of measuring a limited number of pre-defined points, the whole surface of the storage tank can be analysed. The completeness of capture means that deformation in the surface of the storage tank will be easier to identify and the analysis is more comprehensive.
We can also report on the tank floor settlement and tank verticality, and can measure deformation of the tank shell from the outside or the inside of the storage tank.
This data can also be used to analyse peaking and banding across the whole tank surface and not just the locations an operator can reach.
We can monitor for subsidence in crude oil storage tanks by the method of precise leveling. A typical monitoring network would consist of control points established about 100m from the tank in an area that is known to be stable. We would then survey studs established at the base of the tank. From the control points, the stud locations area leveled using a high precision digital level.
In order to monitor a larger area around the tank, we can carry out similar monitoring using a laser scanner. Please contact us for more informaton.
With comprehensive laser data across the entire tank wall we can see if the tilt on the tank is uniform or is creating stress in different areas of the tank base or tank wall.
3D modelling of the storage tank and it's surroundings allows us to create a comprehensive dataset that can be used to obtain direct measurements and volumes to ensure that containment dikes for example, satisfy regulatory requirements. Areas of potential concern or failure can be quickly identified and quantified to reduce repair time.
Surveying the storage tanks with a laser scanning instrument allows us to carry out a geometric evaluation of the tank in it's current state. The model can be compared to original design drawings or previous survey datasets. We can generate 3D models of the entire tank, including complex roof structures, floor, shell and apertures. These models can aid in designing floating roofs or replacement floors.
The model can be used to access maintenance data from asset management software, BIM and GIS as well. It can used for training operatives on a virtual site, and for emergency planning.
Over time, a storage tank can deform due to pressure on the tank walls and floors. In the case of floating roof tanks, the roof rim can go out of shape and this can hinder movement of the floating roof. The high pressures exerted on the tank bottom can cause subsidence, resulting in the tank tilting.
We can accurately measure and monitor out of roundness of the tank shell, tank tilt, subsidence and tank floor settlement.
The image (left) shows the floor of a storage tank that has been mathematically compared to a perfectly horizontal datum and differences in elevation derived. The area coloured red shows where the tank floor is higher than it should be and the blue coloured area shows where it is lower. The tank floor here is tilted.
The image also shows clearly the floor plate seams. We can also identify column locations, floor markings and features from the scan data. By analysing the height profile around the perimeter of the tank, it is possible to visualise shell settlement. We are also able to analyse the verticality of the columns within the tank. The data from our analysis can be used in finite element analysis, for example to examine flexural-torsional buckling of beam-column supports.
Laser scanning facilitates a comprehensive analysis of storage tanks. Scanning allows us to monitor the entire tank shell for deformation rather than by surveying a limited number of discrete points.
Traditionally, storage tank survey is carried out using a total station or a simple measuring tape. While these techniques provide the necessary position information, they are generally time intensive when multiple measurements are required. When using a measuring tape, measurements are prone to errors. 3D scanning removes these deficiencies by capturing thousands of points in the same time it takes to capture ten points with a total station.
From the scan data, we are able to provide:
> Difference maps that compare millions of points between scans to highlight areas where change has occurred.
> Radial displacement plots for every degree around the storage tank.
> Diametrical distance analysis so that engineers can understand the variation in verticality of the tank wall.
> Overall verticality analysis
> Tilt/subsidence analysis
We can also capture imagery on site, this visual information provides a record of areas surveyed and could be used for monitoring or for Q/A of work carried out.
The exact roundness of a tank is determined, this ensures that roof fabrication or seal selections match the existing structure. Alternatively, the information can be used to identify areas to be corrected for roundness and to verify repairs before fabrication.
Comparisons of millions of points between two scans over an extended period can highlight areas where change has occurred. Closer inspection or repairs could then be undertaken on the specific areas of concern to avoid costly failures and potential loss of assets.
The Control of Pollution (Oil Storage)(England) Regulations 2001 require that secondary containment (bunds) have the capacity to contain a spill or leak in the event of a faliure. Our surveys confirm that the bund is able to hold the required 110% of the maximum capacity of the largest tank or drum. We can compute the bund capacity and model spill scenarios.
If the survey is extended beyond the bund, using laser scanning, or to a wider area using airborne lidar, we can examine the route any pollutants may take to a watercourse in the event of an accident.
We have surveyed numerous underground storage tanks, sometimes this has required our staff to have confined space training. For many projects we have not needed to enter the storage tank as we have been able to lower the instrument through roof hatches, which is obviously safer than needing to access the tank.
Data for both the tank floor or sump and filling volume are recorded in a single operation, and an estimation of tank thickness is not required as the internal cavity is directly measured. Scanning the interior of a tank is also much faster than by using traditional methods and is therefore safer.
We can apply a variety of surveying technologies to provide topographical survey of green field sites prior to development of a new terminal. This includes aerial lidar, aerial photogrammetry (including using low cost UAV technology), and conventional ground based survey.
For shore based terminals we can add seabed survey using bathymetric and hydrographic methods, plus highly detailed survey of existing berths and jetties using laser scanning methods.
For expansion of existing terminals we can add laser scanning and 3D modelling for pipeline tie-ins to existing plant.
Maintenance of existing plant is enhanced by accessing asset management data via a 3D model of the site. We can generate P&IDs and re-engineer as-built CAD drawings where records of design plans have been lost.
During development of the UK's latest container terminal ( London Gateway ) we surveyed the river Thames inter-tidal zone for DP World, using aerial Lidar and satellite imagery, so they could comply with their Environmental obligations to ensure there were no detrimental affects during the deep channel dredging.
StorageTankSurveys.co.uk is a specialised part of Merrett Survey Limited's worldwide survey services. The company started trading in 1982, so in August 2012 Merrett Survey celebrated 30 years of topographical survey business. Based in the South West of England we have expanded to work throughout the world in over 59 countries including Australia, New Zealand, Algeria, France, Guinea, Bermuda, Philippines and the USA to name but a few.
Merrett Survey was one of the first commercial organisations to invest in GPS technology so we have built up a mass of experience and knowledge. More recently we have been applying the latest surveying technologies including airborne and land based laser scanning ( LIDAR ).
It is the aim of Merrett Survey to meet the needs of our clients by
providing a high quality and cost effective service. We will advise and
put forward innovative ideas and new technology to benefit all parties
by working in Partnership.
Merretts put forward innovative ideas and use new technology. We offer a wide range of survey services.
Our client list includes:-
Oil and Pipelines Agency
GE Oil and Gas
World Bank / Asian Development Bank
Environment Agency (UK)
Ordnance Survey (UK National Mapping Agency)
IGN ( France's National Mapping Agency )
DPWH (Department of Public Works and Highways, Philippines)
UN (United Nations)
""Their deep understanding of GPS & rigid quality controls has particularly impressed us""
""Merretts have shown themselves to be technically very capable, providing a positive professional approach""
"Merretts provided an excellent service when called upon. They were responsive, helpful, innovative and effective and worked well as part of the overall team delivering emergency response to the South West of England."
3, Merlin Business Park, Fairoak Close,
Exeter Airport, EX5 2UL, UK
For UK and 'rest of the world' use-
Telephone +44 (0) 1392 362161
Fax +44 (0) 1392 362289
3, Merlin Business Park, Fairoak Close, Exeter Airport, EX5 2UL, UK
+44 (0) 1392 362161