Above Ground Storage Tanks
TANKPAC™ is not an inspection method, but a maintenance planning and sorting tool. This system can separate good tanks from bad and direct maintenance to where it is most needed.
Highly sensitive acoustic sensors are attached to the wall of the tank being monitored, following a period of conditioning during which valves are closed and heaters/agitators turned off. Any fracture caused by corrosive products is detected, together with leaks which are active during the actual monitoring period.
A percentage of this data is located by triangulation, but the most important information from a maintenance management point of view is the overall condition of the floor which is given a grading on an ‘A’ to ‘E’ scale.
TA-LRUT™ (Tank Annular Long Range Ultrasonic Testing)
A critical part of any storage tank is the annular ring area. Severe damage here can lead to major structural failure with consequent rapid loss of contents. During operation, water can get underneath the annular ring or chine area and may corrode the floor and annular ring undetected, the results of which can be seen during TANKPAC™ in-service floor testing.
In order to get some indication of the severity of the damage the MISTRAS GROUP has developed an automated scanner, software and procedure to assess this area without the tank needing to be removed from service.
Automated UT - B/C Scan
A computer controlled crawler with magnetic wheels allows for millions of ultrasonic thickness measurements to be taken on the tank shell and roof without scaffolding or rope access requirements. The inspection may take place while the tank is still in production without any adverse effects on reading accuracy.
Thickness measurement results may take the form of a B-Scan or C-Scan mapping. B-Scan is a position vs thickness plot of a 10mm wide strip with a linear resolution of 1mm. C-SCAN provides a material thickness map (X and Y vs thickness) allowing for accurate corrosion mapping with a 1mm x 1mm resolution attainable in a 300- 600mm wide strip.
API653/ EEMUA 159
A full external API653 (Sections 6.3 and Annexure C)/EMUUA 159 inspection, including calculations, may be carried out for a comprehensive tank fitness for service study.
Electro Optical Distance Ranging (E.O.D.R) is a rapid vertical, horizontal and spherical storage tank calibration and settlement inspection method which conforms to ISO standards. Currently E.O.D.R is the most accurate ISO recognised technique worldwide. The technique is able to determine and analyse total tank settlement whilst performing tank calibrations.
Online tank settlement covers shell roundness, shell verticality, edge settlement, rigid tilt and differential settlement overlooked by other tank inspections. Due to demand, shell banding and peaking of vertical and horizontal welds is currently under development.
Magnetic Flux Leakage (MFL)
A magnetic field is induced into a material which produces flux leakages over volumetric changes (e.g. due to corrosion) thus identifying areas for follow-up inspection using manual ultrasonic.
Portable equipment is used to obtain an induced pressure differential enabling a fast and cost effective method of through weld leakage inspection on shell, floor and annular welds.
Automated UT – B/C Scan
A computer controlled crawler with magnetic wheels allows for millions of ultrasonic thickness measurements to be taken on the tank floor, shell and roof without scaffolding or rope access requirements.
This utilises zero degree as well as angled probes to evaluate welds and areas of concern such as localised corrosion. Experienced UT technicians are able to accurately size defects normally first discovered by rapid scanning techniques such as MFL, vacuum box testing, MPI etc.
API653 / EMUUA 159
An internal and external API653 (Sections 6.3, 6.4 and Annexure C)/EMUUA 159 inspection including calculations may be carried out for a comprehensive tank fitness for service study.
E.O.D.R is used to determine and analyse total tank settlement whilst performing tank calibrations.
In addition to the tank settlement scope covered in the Online inspection, floor settlement and floor sagging are incorporated.