Rafferty Steeplejacks have successfully completed inspection and maintenance works on the 2 No. multi flue steel chimneys at the University Hospital of North Staffordshire. With only a handful of chimneys now left in Stoke-On-Trent, Rafferty’s were delighted to be rewarded with this local contract.
Posts tagged "chimney inspection"
Fertiliser Plant UK 2009/2010.
Inspection and Repairs to 56.1m High S1240 Boiler Steel Chimney.
In 2009 Rafferty Steeplejacks successfully tendered for an external and internal inspection of the 56.1m high S1240 boiler steel chimney at a UK fertiliser plant. The internal inspection revealed deteriorated steelwork and holes within the top section of the chimney. As the chimney could only be shutdown for a certain amount of time, any further inspection or maintenance work had to be undertaken externally.
The S1240 steel chimney was manufactured and installed in 1975 making the chimney circa 35 years old. As steel chimney design standards have been revised and improved since original construction, along with the present condition of the chimney following our initial inspection, it was agreed that the chimney should be re-designed and a structural feasibility study should be carried out to CICIND:1999 and the new Eurocodes EN 1991 which will soon replace the present British Standard BS4076;1989 for steel chimneys. The re-design calculations and feasibility study revealed that the design life of this chimney could be substantially extended by over-plating and strengthening works being carried out to various areas of the chimney shell along with replacing the helical strake wind stabilisers at the termination point of the chimney with a modern fluid stabilising damper system to reduce excessive oscillations.
Rafferty’s offered the client a full turnkey project solution to extend the design life of this chimney and such was their faith in Rafferty’s knowledge, experience and capabilities in steel chimney construction and maintenance, the contract was awarded on single tender.
As previously stated, as the client was unable to shut the chimney down for the entire duration of the project, all works had to be approached from an external view point. As the chimney shell is concealed with mineral wool insulation and aluminium cladding externally, the cladding and insulation would need to be removed to enable any repairs to the chimney shell to be carried out.
It was decided that the first area of consideration would be the deteriorated areas of steelwork and holes that were located in the top section of the chimney. To access the full circumference of the chimney, a modular frame scaffold deck was installed directly below the upper most flange at 42.1m above ground level. Following which a multi-lift scaffold arrangement was then erected for a further 8m providing safe working platforms to all elevations of the structure within this area. Further design calculations were carried out which prevented fully scaffolding the top section of the chimney to the termination point as the scaffolding would add additional wind loadings to the already weakened structure. Therefore, the remaining top 6m of the chimney would be accessed by erecting a full circumference modular frame scaffold deck at approximately 2.5m below the termination point and from this a full circumference moveable tirfor platform was utilised to gain access below. This form of access was only installed once the multi lift scaffold arrangement was dismantled. Please see the following photographs showing the scaffold arrangement and click to enlarge.
Utilising the multi lift scaffold arrangement and moveable platform, the aluminium cladding and insulation was removed throughout the full height of the top chimney section. On removal of the cladding numerous defects were located to the chimney shell steelwork. Directly above flange level the original manufactures of this chimney installed a cladding ring throughout the full circumference of the stack. Its purpose was to support the insulation above and prevent it from slipping. As the cladding ring protrudes from the chimney shell, it is considered as an external ‘cold spot’ as it will not be consistent with the operating temperatures of the chimney shell steelwork. These external ‘cold spots’ are where accelerated corrosion and deterioration will form on steel chimney structures should weather penetration occur. Numerous ultrasonic thickness readings were therefore carried out above and below the cladding ring which revealed that the chimney shell had deteriorated far beyond its original corrosion allowance. Further deterioration and holes had also occurred around other external ‘cold spots’ within the top section of the chimney such as the access ladder securing brackets and helical strake securing bosses. Please see the following photographs which show the deterioration identified within the top section of the chimney and click on images to enlarge.
Following the inspection, the areas of the chimney shell requiring maintenance works were plotted and submitted to the client. Extensive over-plating works were then carried out to the chimney shell steelwork with the top section of the stack. Using trained steeplejack coded welders, the cladding ring was removed and the chimney shell at this location was over-plated with 8mm thick mild steel plate for a depth of 1m throughout the full circumference. Extensive patch plating was also carried out around the access ladder securing brackets and helical strake securing bosses at required locations with 8mm thick mild steel plate. Quality procedures were also implemented throughout the duration of the repair work and our workmanship was independently inspected and quality checked by a qualified company who carried out a magnetic particle inspection of the new weld seams. The results of which achieved the complete satisfaction of the client.
The extent of deterioration evident within the top section of the chimney raised serious concern with both ourselves and the client. It was therefore decided that further inspection work should be carried out to the remainder of the chimney. The original manufacturers of the stack had installed cladding rings above each connecting flange. It was agreed that the aluminium cladding and insulation should be removed above each flange level to expose the cladding ring. To remove the cladding and insulation in a safe and controlled manner required access to the full circumference of the chimney. To avoid the use of costly crane hire or extensive scaffolding works, access was achieved by using the full circumference moveable tirfor platform which was originally used within the top section of the chimney. A thorough inspection and extensive thickness tests of the chimney shell could then be carried out in these areas. The chimney shell was also exposed and inspected around each access ladder securing bracket and sample platform securing bracket. Fortunately the defects to the chimney shell were only limited to the top section of the chimney and no further maintenance works were required to the remainder of the stack. Please see the following photographs showing the moveable access platform and inspection of the chimney shell.
The final element of this project was the installation of the new fluid filled stabilising damper system. The original helical strakes were first removed and support brackets were installed to the chimney shell steelwork ready to receive the damper system. Utilising a 220 ton mobile crane the damper system was installed at the termination point of the chimney. Please see the following photographs showing the new stabilising damper being installed and finally in position.
This project was successfully completed without any safety incidents and to the complete satisfaction of the client. Our ability to provide innovative maintenance and access solutions have succeeded in prolonging the design life of this structure without any disruption to the operating conditions of the chimney.
UK Oil Refinery 2009/2010 Shutdown.
Inspection and Repairs to 151.3m High HPBH Reinforced Concrete Chimney.
In 1989 Rafferty Steeplejacks carried out an inspection of the 3 No. brick liners within the 151.3m high HPBH concrete chimney. The inspection revealed that the brick liners were found to be in a structurally poor and unsafe condition and a substantial demolition, engineering and construction project was therefore required. The 3 No. brick liners had to be demolished piecemeal and replaced with new steel liners throughout the full height of the chimney internally. Such was the faith in Rafferty’s construction and engineering capabilities, the client awarded the £1.65 million contract on single tender. All elements of this contract from piecemeal demolition of the original brick liners to the manufacture and installation of the new steel liners was solely carried out by Rafferty’s, offering the client a full turnkey project from start to finish.
Rafferty’s have been involved in every major shutdown on this oil refinery since 1974. In 2009/2010 we were contracted by the client to carry out detailed inspection and maintenance works on the 3 No. steel liners within the 151.3m high HPBH concrete chimney during the 2010 planned shutdown period.
Health & Safety is always the first consideration of every contract undertaken by Rafferty’s. Careful planning and documented method statements and risk assessments were issued to cover all aspects for the safe execution of this contract. To gain safe access to within the concrete chimney windshield there are a series of internal floors and at the top floor level a series of winch arrangements were specifically designed, tested and installed within the chimney windshield. One winch was used to hoist all plant and materials and the other winch was used to hoist our operatives to the top floor level of the chimney windshield. Please see the following photographs below showing the winch lifting arrangement.
Once access was achieved, the inspection works could then begin. Within the concrete chimney windshield at the top floor level, scaffolding was erected and fully boarded out to enable the insulation and cladding to be removed from the steel liners at required locations. A thorough inspection of the liner steelwork could then be carried out. Above the roof of the concrete chimney windshield at 151.3m above ground level, the internal liners protrude for a further 3.7m. The liners above roof level were originally constructed from 316 stainless steel and are wrapped with mineral wool insulation and cladding. A thorough inspection of the liners above roof level was necessary and required the removal of the insulation and cladding throughout the full height of each liner. In order to achieve safe access to the full height and 9.1m circumference of the liners above roof level, a specialised multi lift scaffolding arrangement was specifically designed for this demanding task. Once the scaffold access was in position, the cladding and insulation was removed and a thorough inspection of the liner steelwork was carried out. At the levels inspected the liners were found to be in a poor condition with large areas of metal reduction and perforated steelwork evident. Due to time constraints the replacement of the liner sections was not possible and therefore structrual over-plating works was determined as the only viable option for a suitable repair.
The aforementioned project was successfully completed within the required shutdown period, without any safety incidents and to the complete satisfaction of the client. Please see the following photographs which detail the inspection, defects and repairs carried out the liners above roof level.
UK Oil Refinery 2006/2007 Shutdown.
Inspection & Repairs to 120m High Platformer 3 Concrete Chimney.
Rafferty Steeplejacks have been involved in every major shutdown on this oil refinery since 1974. The major shutdown in late 2006 and early 2007 was no different and we were awarded several chimney inspection and repair contracts during this period. The contract highlighted above was considered the largest and most demanding during this particular shutdown.
A full internal and external inspection of the 120m high platformer 3 reinforced concrete chimney was required, along with possible repair works resulting from the inspection. This work was carried out by erecting traditional steeplejack ladders on one elevation to the termination point of the chimney. At 100m above ground level a safety fan deck scaffolding was erected which ran throughout the full circumference of the chimney. Modular frame scaffolding was then erected at approximately 118m above ground level and ran throughout the full circumference of the chimney to form a working deck. Suitable scaffolding was then erected over the termination point of the chimney to enable an internal inspection of the brickwork lining on all elevations from a man riding winch and steel gondola. An all elevation external inspection of the concrete chimney shell was carried out utilising man riding cradle access. The following photographs demonstrate the scaffolding and access methods utilised for this contract (please click on images to enlarge).
Following the inspection various repair works were carried out both externally and internally.
The external repair works included the following;
1. The existing termination point castings were replaced with a new stainless steel capping arrangement which was designed and manufactured in-house – please view the following images and click to enlarge.
2. Numerous concrete and fracture repairs were carried out throughout the full height of the concrete chimney shell on all elevations.
The internal repair works included the following;
1. Brickwork fracture repairs were carried out throughout the full height of the lining using Sairset acid resistant mortar.
2. The corbelled expansion joints at the top of each brickwork lift underwent repairs and were re-packed with ceramic fibre insulation and rockwool insulation – please view the following images and click to enlarge.
The aforementioned project was successfully completed within the required shutdown period, without any safety incidents and to the complete satisfaction of the client.
AB Mazeikiu Nafta Oil Refinery – Lithuania 2005/2006.
Inspection and repair works to 123.18m High Reinforced Concrete Chimney.
Contract Value £550,000.00
In 2005 and 2006 Rafferty’s specialised steeplejack services were recruited by AB Mazeikiu Nafta on their large oil refinery in Lithuania. In 2005 Rafferty’s carried out an all elevation external inspection of the 123.18m high No. 2 concrete sulphur stack. The top 13.35m of this particular chimney had been recently re-built by others with a moler type brick which was coated with a two part resin coating externally. The detailed inspection we carried out revealed that the outer resin coating and chimney brickwork within the top 13.35m of the chimney was found to be in an extremely poor condition, with large areas of the coating becoming loose and detached from the chimney and ultimately falling to ground level.
Following our inspection of the structure, our experienced management team gave great consideration to how the upper 13.35m of this chimney could be repaired. With no shutdown of the chimney planned for the foreseeable future, it was decided that the only long term and viable option would be to install a stainless steel sheath within the top approximate 14.5m of the chimney. The stainless steel sheath was designed and manufactured in-house and shipped over to Lithuania along with all plant, equipment and materials required to carry out the work.
The site works commenced in August 2006 and a strict time schedule had to be implemented to avoid the harsh Lithuanian winters. In addition to this, the client was unable to shut the chimney down so the entire project had to be undertaken without any disruption to the operating conditions of the chimney. To enable the safe installation of the sheath a modular frame and multi-lift scaffolding arrangement was erected within the top 15m of the chimney. A man riding and materials winch arrangement was installed to enable safe access for our steeplejack operatives and to hoist the sheath sections to the termination point of the chimney. Once in position, the sheath sections were welded together by Rafferty’s coded welders and a combextra sulphur resistant type grout was poured between the stainless steel plates and the existing chimney brickwork. This process was completed until the sheath completely enveloped the top 14.5m of the chimney. Concrete repairs were also carried out to areas of the reinforced concrete chimney shell using cementitious concrete repair mortar.
The aforementioned project was successfully completed on time without any safety incidents or disruption to the operating conditions of the plant. Daily quality checks of our workmanship were also carried out by the client to which we achieved complete satisfaction. The following photogrpahs will give you some indication of the scale of this particular project. Please click on the images to enlarge.