ACFM

Civil Engineering Applications

Introduction

Many civil engineering structures contain or comprise steel frameworks, welded together and painted or galvanized to prevent corrosion, or coated with materials with specific properties, such as intumescent paint for fire control. These are ideal for inspection by ACFM due to its ability to work through coatings.

Many contemporary building designs use exposed steelwork with high quality, decorative and expensive coatings.

 

Other typical structures that are routinely inspected with ACFM include cranes, road and rail bridges, theme park rides and roadside lighting.

Overview

TSC are widely involved in the ACFM inspection of steel constructed buildings, whether in the temporary steelwork phase, lifting or strand-jacking operations, substructures, superstructures or fascia and aesthetic steelwork. In all these areas, ACFM is used to detect inherent or fatigue related cracks, either on the bare steel or through primer or high quality, expensive cosmetic finishes. This rapid, non intrusive operation has saved clients many thousands of pounds and time in categorizing potential or existing defects.

Inspection of this kind is normally carried out against National Structural Steelwork Specification for Building Construction, Issue 4, Annex C specifications.

 

Bridge inspection is another expanding area for ACFM. Road bridges, rail bridges, footbridges and historic bridges are all part of TSC's expertise. From the inspection of mounts, swivels, supports and bearers in the construction phase, through in-service fatigue cracking through paint coatings or corrosion, to historic cast iron bridges under protection or conservation orders – all can be assessed quickly and efficiently with ACFM.

No damage, no coating removal, minimum cleaning and an instant, permanent electronic record.

 

Crane inspection is complex because of the geometries involved, their location, height and the fact that the majority are coated with anti-corrosion paint. All of these factors mean that normal inspection techniques are very difficult to apply. In the absence of a suitable inspection technique, some cranes are removed from service because of their age without knowing the complete condition of the crane. Inspection and confirmation of their structural integrity would elongate their useful life. When conventional inspection is required, a crane can be out of service for a number of weeks while the coating is removed for magnetic particle inspection and then reapplied. TSC have extensive experience of dock cranes, tower cranes and container cranes.

 

The ability to use ACFM with rope access technicians allows inspection in areas of difficult access without the need for scaffolding or other support structure. In addition out-of-service time is reduced as the use of ACFM eliminates the need to remove and reapply paint or other protective coatings.

Projects and Applications

Motorway road bridges  

Project Equipment
Motorway bridge - box girder inspection

U19 AMIGO instrument

40mm 8 channel flat array probe 5KHz

Standard weld probe 5KHz

Encoder weld probe 5KHz

 

 

ACFM inspection was carried out on numerous cross braces on box girder bridge structures on Bescot Viaduct. All inspection was confined space entry, making ACFM an ideal method of inspection.

The scope of the inspection was to provide an engineer, probe operator and equipment to carry out ACFM testing on longitudinal box girder welds at Bescot Viaduct.

Bescot Viaduct is located at Junction 9 on the M6. The structures to be inspected were chosen by the client prior to the inspection.

The purpose of the work was to detect any surface breaking defects (horizontal or vertical) in the weld cap or vicinity of the selected weld and toes.

Civil engineering   

Project Equipment
Pre-lift qualification of temporary steelworks

U19 AMIGO instrument

Standard weld probe 5KHz

Straight long nose probe 5KHz

Right angle mini probe 5KHz

Straight mini probe 5KHz

40mm 8 channel flat array probe 5KHz

 

TSC Inspection Systems worked closely with Watson Steel, the manufacturers of temporary and permanent steelworks at London Heathrow Airport Terminal 5 constructions.

 

Work began to raise the roof in April 2004 when the first of six 2,500 tonne steel sections was lifted. Each 117m arch section was assembled at ground level and the roofing components fitted before being jacked up approximately 40m to their final position.

Assembling the roof at a low level reduced the risks of working at height, and allowed cranes to operate inside the radar zone imposed on the construction team by the airport operations.

The use of TSC's ACFM inspection techniques was effective in quickly and accurately assessing the integrity of the welded temporary steelwork of the jacking beams, through the paintwork, before the first lifts took place.

ACFM inspection was also carried out extensively on the substructure steelwork and critical components on the airside bridges.

All ACFM inspection at T5 was carried out through coatings, whether primer or final intumescent paint, which is extremely difficult to remove. Inspection was far faster than conventional methods, enabling construction to carry on without major delay.

River bridges  

Project Equipment
Motorway bridge - plate inspection

U19 AMIGO instrument

40mm 8 channel flat array probe 5KHz

Standard weld probe 5KHz

Encoder weld probe 5KHz

 

Bray Bridge was constructed in 1961 and carries the M4 over the River Thames at Maidenhead.

ACFM was used in conjunction with Magnetic Particle Inspection (MPI) to check specified welds for defects. All inspection was carried out through the existing paint coating, greatly reducing the amount of inspection time and enabling engineers to have an accurate, permanent record of results that can be used for condition monitoring over a long period.

ACFM inspection was carried out primarily with a single coil standard weld probe as this was most suited to the geometry of the welds to be inspected. A flat 8 channel array probe was used in areas where wider coverage was required (40mm wide strips), and a 3 channel encoder weld probe used on welds where access permitted. The latter gave the advantage of covering an area deeper into the HAZ (Heat Affected Zone) and observe the coil response if a defect was found. A further benefit of using this probe is the position encoding, allowing the pinpointing of defect ends from the start of the scan.

Civil engineering

Project Equipment
Civil engineering site-works

U19 AMIGO instrument

40mm 8 channel flat array probe 5KHz

Standard weld probe 5KHz)

Right angle pencil probe 5KHz

Straight mini pencil probe 5KHz

 

TSC were contracted to carry out ACFM inspection on numerous louvre support column assemblies, louvre roof support columns and base supports at Chiswick Park, London.

 

The purpose of the inspection was to locate any surface breaking defects in the weld caps and weld toes, through the existing paint coating. All butt welds were ground flat and painted to finished standard. An ACFM array probe with width coverage of 40mm was used, one pass either side of the weld centre line to provide total width coverage of approximately 80mm through the full circumference of the weld. Single coil weld probes were used on the base plate fillet welds on the louvre roof support columns and on the circumferential welds on the base stub columns.

 

Use of the array probe provided simultaneous data for both X and Y directions (i.e. longitudinal and transverse to the line of the weld).

Railway Bridge Inspection

Project Equipment
Railway bridge - box gider inspection

U19 AMIGO instrument

40mm 8 channel flat array probe 5KHz

 

Hyde Lane underbridge was constructed in 1969 and carries the two lines of the Bristol and Gloucester line over Hyde Lane one mile south west of the A435 in Cheltenham. It is an early form of the ‘Western Region Box Girder' bridge, constructed from three main box girders, cross girders, deck plate and ballasted track. The superstructure is supported on reinforced concrete cill beams on masonry stone abutments and wing walls.

 

ACFM was carried out using a flat 40mm array probe to investigate the integrity of corners on cross girder webs. Inspection of the up line side was completed in one night shift, with the benefit of only having a partial road closure for 12 hours. The down line side was again completed in a second 12 hour shift.

Historic Bridge Inspection

Project Equipment
Historic bridge inspection - dissimilar metals

U19 AMIGO instrument

40mm 8 channel flat array probe 5KHz

Micro pencil probe 5khz

 

 

Another challenging project TSC has been involved in is the inspection of welds on an historic bridge, constructed in 1867, spanning the river Thames.

 

Longitudinal beam web repairs had been carried out on the bridge, involving joining the original cast iron material with steel insert plates. Time and weather over many years had caused corrosion and degradation of some of the side panels.

 

Tests carried out in TSC's workshop on material samples prior to the inspection resulted in a high degree of confidence in the system for use on what is an unusual combination of welded materials, and the fact that there was a relatively thick primer and paint coating.

 

ACFM inspection was carried out using a hand held array probe with positioning encoder. The advantage of using the array system over single coil probes is that a much larger area can be inspected in one pass of the probe. This situation was ideal as the welds had been ground flat. In practice, an area of approximately 35mm wide was covered, thus inspection of the entire weld face and heat affected zone was accomplished in a single pass with the paint coating completely untouched.

Railway Bridge Inspection

Project Equipment

Rail underbridge

 

 

U19 AMIGO instrument

Standard weld probe 5KHz

Straight pencil probe 5 KHz

 

 

Several major UK based civil engineering contractors were working in partnership on the repair and maintenance of a pair of steel underbridges, just to the north of Oxford Station. The bridges each carry two tracks over a waterway in a single span. The bridge has recently had a new abutment built under the southern end to give it proper support.

The six main girders have between them span cross girders which in turn support rail bearers and the deck plate. A limited amount of ACFM testing was carried out to assess if any fatigue cracking was present. 

Queen Elizabeth Bridge

Project Equipment

Roadside lamp post weld inspection

U19 AMIGO instrument

Standard weld probe 5KHz

 

 

ACFM inspection was conducted on 114 QEII bridge lamp post welds. No cleaning or paint removal was required. Inspection was carried out by rope access technicians and a remote ACFM operator, removing the need for plant, cherry pickers or scaffold.

Crack Detection / Applications / Civil Engineering    1 2 3 4 5 6 7 8 9 10 Next