GB2340576A

GB2340576A - Repair of tubular column using a sleeve

Info

Publication number: GB2340576A
Application number: GB9817849A
Authority: GB
Inventors: Keith Swift
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-18
Filing date: 1998-08-18
Publication date: 2000-02-23
Also published as: GB9817849D0

Abstract

The column, e.g. a steel street column, having corrosion in an given area, is initially cleaned, e.g. wire brushed, to remove surface corrosion, coated with a metal based paint and covered with heavy duty bitumen to arrest further corrosion. A single or two-part sleeve of similar material to the column is placed around the affected area, the sleeve having axially extending end flanges coupled by bolts, the flanges then being covered by a prefabricated elongate cover. The void within the cover is injected with bitumen and all joints between the sleeve and column and the cover have sealant applied.

Description

2340576 Prolposal to ellect the repair of tubular steel columns.

Description.

Emergency safety and repair sleeve incorporating repair procedure.

The device relates to a snap on steel sleeve designed to secure corroded and unsafe steel street columns of any diameter incorporating a permanent repair.

Corrosion above ground level of many steel column structures is common and a problem well-known to local authority and highway engineers who often struggle with manpower and resource shortages, preventing a short- term solution by replacing defective columns.

The objective of the safety sleeve is to immediately make safe the defective column and effect a permanent repair.

Accordingly the sleeve provides immediate public safety and provides a repair equal to the original structural parameters of the column.

The sleeve should be manufactured to steel in accordance with BS4360 grades 43 and 50 or their equivalent. Any welding to the sleeve should be in accordance with BS5135.

The Repair Procedure The repair area.

Fig 1 The corroded or damaged area can span 113 of the circumference before it is discovered but does not usually extend below ground level.

Fig 2 Excavate to expose the base of the column to within approximately 50mm above the cable access void.

Fig 3 It will now be necessary to rotary wire brush the repair area of the column between the access door and the cable access void to remove any surface corrosion.

After cleaning, this area should be coated with a metal based paint. After a suitable drying time the area should be coated with an application of heavy duty bitumen to arrest further corrosion. All coatings should be to customer specification and in accordance with DTP 1900 series.

The Sleeve.

Fig 4 The sleeve should be produced using the same material as used in the fabrication of the onginal structure and fabricated to the the dimensions of the specific column and area to be repaired pre-flanged and drilled. Plate thickness should match that of the column. All corners should be ground to a smooth profile and rounded.

Fig 5 The application of the sleeve to the column is achieved with the aid of a device specifically adapted for this function which operates as a vice, expanding and contracting the sleeve. By using this device the sleeve can be passed over the reduced section of the column, allowing it to be manoeuvred down the column and placed in position over the repair area. Alternatively, the sleeve could be manufactured in two halves to enable even easier application to the column at the repair area, maintaining equal structural values.

Fig 6 The sleeve is mechanically joined by use of high-tensile steel bolts in accordance with BS DIN 933. Hole spacing will be dependent upon the specific dimensions of the sleeve to be fabricated. For the repair of standard size columns of 168min diameter, spacing should be at 50mm.

Fig 7 To prow the flanged joint and fastenings this area is protected by a pre fabricated cover fabricated to the dimensions of the specific sleeve to be used. The flange cover would normally be fabricated in carbon steel but a further consideration could be stainless steel or corrosion resistant plastic. All corners should be ground to a smooth profile and rounded.

Fig 8 The upper bolt hole of the cover should be drilled to a larger diameter than the fastening bolt head to allow it to pass through to the securing bar, located behind the hole, as illustrated. This arrangement will allow access to the inner void of the cover, which should now be injected through the hole described, with heavy-duty bitumen to ensure lasting protection to the joined area.

Fig 9 All areas jointed should now be sealed with an application of Evostik Extra Seal which is highly recommended by the manufacturer and comes with a 30 year guarantee. It can be applied in wet conditions and is highly temperature resistant. Paint coating can be applied immediately after application producing no chemical reaction.

After completion of the repair the rooted portion of the column should be treated with an internal and external application of heavy duty bitumen to a height not less than 25Omm above ground level.

Note It is important to note that the application of a metal based paint and bitumen as described in Fig 3 is an essential inclusion in the repair process as this should minimise the possibility of corrosion spreading in the log term from the internal structure to the repair sleeve.

It is equally important to note, that, as described in Fig 8, the injection of bitumen to the inner void of the flange cover is also an essential inclusion to the repair process, thus preventing any moisture build-up in this area triggering corrosion to the joint and its components.

Claims

Claims.

1 To produce an immediate, safe and long lasting repair.

2 The process can be adapted to any size or shape of column.

3 The repair will not fail before the original column fails at different points of the structure.

4 A standard load bearing test will verify the integrity of the repair and will produce energy value readings equal to standard requirements.

The aesthetic appearance of the repaired structure with the application of the sleeve is considerably improved as the defective area cannot be detected.

6 The application of the repair sleeve does not impede public safety as there are no excessively protruding areas after repair. All comers of the materials used in the repair process are ground to a smooth profile and rounded.

7 The cost of the repair is a fraction of the cost of purchasing and erecting a new column. Almost always a column will fail in the small area described in this documentation a very small area, when the remainder of the structure is engineeringly sound both electrically and structurally which would indicate a substantial waste of resources in purchasing and erecting a new structure when an effective and permanent repair can be achieved at low cost.