CONCRETE CHIMNEY REPAIR

·         Inspection

·         Visual examination

·         Our visual inspections reveal evidence for the majority of problems in a chimney.  A detailed photographic and video inspection record is made of each chimney inspection.

·         Rebound testing

·         As well as a close visual inspection, the concrete is tapped with a hammer to determine areas of delamination and spalling.  A detailed report is provided showing marked up defective areas.

·         Concrete cores

·         We are able to core drill the concrete windshield utilising rope access.  The cores are then used for further testing such as chloride analysis and compression strength testing.  The cores also provide a visual aid in type, size and scatter of aggregate and size and depth of reinforcement steel.

·         Ultrasonic thickness measurements

·         Our qualified UT technicians can measure the thickness of the steel plate and top cap.  An advantage of ultrasonic thickness gauging is that it only requires access to only one side of the plate.  For powerhouse stacks which are usually insulated the insulation can be removed and replaced when testing.

·         Testing of connecting joint bolts

·         Selective sample bolts are taken and replaced from the connecting joints of steel chimneys and tested for fatigue defects using non destructive testing.  This is highly beneficial and can help determine if there are large amounts of wind loading or vibration in the chimney.

·         Other investigation methods

·         Maintenance and repair

·         After planning and specification from a qualified engineer RAI&M are able to carry out repair work scopes in a methodical and efficient manner using specialist access methods to eliminate down time.  The most common forms of repairs offered are as follows:

·         Steel repairs

·         Steel chimney windshields or flues that have experienced corrosion damage which may affect the structural performance of the chimney are repaired using ‘doubler plates’ predetermined by a qualified engineer who has experience in the design of industrial chimneys.  These plates are installed by qualified welders in conjunction with a suitable crane and advanced rigging equipment.  Often, the steel plate is of a heavy weight and the chimney taller than an available crane.  Here, helicopter assistance or an advanced pulley system with rated lifting gear can be utilised.

·         Concrete repairs

·         Repairs to the outside of a defective concrete windshield use similar techniques and repair materials to those used on other reinforced concrete structures using rope access.  General patch repairs are made using a proprietary polymer-modified cementitious repair mortar system that is applied by trowel and a gloved hand with rope access.  Cracks in concrete windshields can be repaired by means of a flexible sealant or injection if required.

·         In some cases where there is substantial degradation to the top cap RAI&M are able to provide complete top cap rebuilds with the addition of a concrete or steel casing around the outside of the existing chimney windshield after a methodology and design has been approved by a qualified engineer.

·         Brickwork repairs

·         The most common forms of repair are re-pointing brickwork and crack sealing.  However using experienced refractory brick layers RAI&M are able to rebuild sections of the brick flue and top.  During repairs metals components, such as bands, lintels, caps and connections can be assessed and replaced as required.

·         Renewal of paint systems

·         Chimney paint systems require renewal when deterioration is sufficient that corrosion is likely.  Also, it is important to have a chimney looking aesthetic pleasing, as they are often a topic of conversation in environmental discussions.  A good looking chimney is less likely to cause controversy in comparison to a chimney that is in a state of disrepair caused by environmental factors and emissions.

·         BES have experience in painting concrete windshields, both internally and externally.  Paint systems to concrete are important for a number of reasons.  They can seal small cracks and prevent possible water ingress which can lead to corrosion of the reinforcement steel. If required, (particularly in marine environments) we can incorporate an anti-carbonation layer to prevent atmospheric carbon dioxide from entering the concrete and reducing the natural alkalinity of the concrete.

·         At the smoke band BES can apply an acid resistant paint system to protect the chimney structure from acid condensation at the smoke band. This is particularly important in protecting the concrete from residual wash down of flue gases during wind and rain.

·         Repair of low-temperature linings

In some chimneys replacement of special linings such as Teflon sheeting, high-alloy steel or titanium sheet, borosilicate glass blocks or acid-resistant coatings is required at the gas seals.  Deterioration here is often caused when the flue gas is below the acid dew point.  During shutdown periods, it is important to have the seals inspected to confirm and monitor the integrity of the seals especially if the manufacturer has provided any performance guarantees.  The inspections are easily achievable by using rope access