MFL Tank Floor Scanning 2009
MFL Tank Floor Scanning 2009
MFL Tank Floor Scanning 2009
INTRODUCTION-Floor Map VS
A New generation Magnetic Flux Leakage system for the inspection of Storage Tank bottom floors scanning. Self propelled by a motor run by a sealed lead acid battery. On board computer allows full data acquisition of signals detected by MFL. Mapping of defect indications in the graphical reporting software in a laptop or desktop computer. Grouping of defects according to severity by colour coded bands.
The basic background of MFL The safety related issues The basic functions of the unit How to handle the Equipment How to perform the scanning Data aquisition saving. Importing data to the reporting software Preparation and printing of final report How to perform basic maintenance
MEASURING PRINCIPLE
MAGNETIC SHOE FIELD LINES
HALL SENSOR
GENERAL DESCRIPTIOIN
METHOD OF OPERATION
Before commencing a tank floor inspection with Floormap VS, the operator should ensure the following information is available: a) Floor plate and annular plate thickness. The Floormap VS is limited to 12.5mm floor thickness in mapping mode. b) Any floor coating thickness in excess of 2mm thickness will have to be simulated during calibration. Any non-magnetic material of the correct thickness can be placed over the calibration plate to simulate the coating. c) General condition of the top surface. Floormap VS will produce a colour coded map of the total floor condition not just the under floor condition. d) Presence of heater coils or other obstructions. These may necessitate the use of manual mode rather than mapping or may require the use of Hand scan to cover areas missed by the larger motorised scanner. e) Floor plate numbering system to be used. A set floor plate numbering system must be used while using the data acquisition software, but this
MECHANICAL SET-UP
Sensor Height adjustment in Mapping (Auto) Mode (Floormap VS)
Plate Thick Sensor Gap (coating thinner than 2mm) Sensor Gap Scan width (coating thicker than 2mm) Thick RangeSwi tch
8 mm 10 mm
250mm 250mm
FM FM
12.5mm
250mm
FM
MECHANICAL SET-UP
DETECTION MODE (Manual)
Plate Sensor Gap Thicknes (coating s thinner than 2mm) 8 mm or less 3.5 mm (7shims) Sensor Gap (coating thicker than 2mm) 2mm (4 shims) Scan width Thickness Range Switch -8 +8 if coating is thicker than 2mm +8 +8
300mm
10 mm 12.5mm
2 mm (4 shims) 1 mm (2 shims)
250mm 250mm
i.
Motor driven. Twisting the right hand handle towards the operator causes the motor to turn. To stop the motor, simply twist the handle away from the operator. Hand propelled. By putting a downwards pressure on the handle the drive motor is lifted clear of the floor. The unit can then run on the magnet carriage rollers alone.
ii.
Tank Datum
Vertical
Tank Datum
Horizontal
Numbering Scheme
At present the Floormap VS system supports the use of row / plate co-ordinates only. These are normally numbered from the top left hand corner of the tank.
1/1 2/1
1/2
1/3
1/4
1/5 2/2
3/1 3/3
3/2
4/2
Plate Reference
Floormap allows the operator to start scanning a plate from any 4 corners of a rectangular or square plate. In order to position the defect location correctly it is necessary to identify which corner of the plate scanning started. This corner called the Plate Reference or PR. As with the numbering system the plate reference is identified relative to the Tank Datum which is always positioned in the bottom left hand corner of the tank. Care must be taken identifying the PR, when the operator is looking towards the Tank Datum rather than away as is normal convention, not to become disorientated and put the PR 180 out of phase.
Plate viewed
Plate viewed
3/1 3/3
3/2
plate 1/2 will be classed as vertical and plate 2/2 classed as horizontal.
4/2
Tank Datum
Scanning Modes
The Floormap VS system uses two types of scanning mode: i) Parallel or Uni-directional scanning This involves starting each scan of the plate from the same side of the plate, and is normally used to scan nonrectangular plates. ii) Raster or Bi-directional Scanning This involves starting alternate scans from opposite ends of the plate. This is the most efficient method of scanning but should only be used to scan rectangular plates.
Plate Coverage
The active scanning width of the Floomap VS system is 250 mm (10 inches). To calculate the number of scans required per plate, simple divide the plate width by 250. The reporting software will automatically allow for an overlap last scan if the number of scans required is not a whole number. Plate width / 250 = number of scans 2000 mm / 250 mm = 8 scans 1850 mm / 250 mm = 8 scans