THE PROBLEM
The engine manufacturing plant had two aged concrete hot well tanks dating back to the 1970s. The tanks are below ground and without any secondary containment. They had been identified as a pollution risk due to the poor condition of the existing tank linings.
The water contained within the hot well tanks is contaminated with engine oil, diesel and anti freeze as part of the engine test process. This chemical cocktail operates at a temperature up to 60 degrees centigrade Therefore a highly chemical resistant tank lining was required.
The coating selection was further restricted by the tight time scale for the works to be completed – the whole application including curing of the new tank lining had to be completed in just 8 days. Most conventional epoxy coatings require 7 days to fully chemical cure.
SOLUTION
Originally we had proposed the application of a fast setting polyurea tank lining as this offered the necessary return to service times. As part of our due diligence we produced an immersion sample which was left in the tank for a period of time. Unfortunately the immersion sample did not perform well which forced a change in tank lining selection.
Fortunately we were able to have access to a new product to the UK Market – Raven Lining 405. This is an ultra high solids, fast curing and rapid return to service epoxy tank lining. This revolutionary epoxy tank lining is fibre and ceramic reinforced and can withstand ground water ingress, with an expected service life in excess of 50 years.
Due to the contamination of the tank by engine oil and diesel the first stage of the tank lining process was the thorough decontamination of the concrete. We worked closely with Cleansing Services Group ( https://www.csg.co.uk/) who had been appointed by the client to enable the thorough degreasing of the tanks internals using steam cleaners and degreasing agents whilst the tanker units were on site.
Following cleaning existing failed fibreglass tank lining repairs were removed using mechanical breakers prior to the preparation of the tank internals by method of abrasive blasting.
Following preparation it was evident that degradation of the concrete substrate had occurred through years of exposure to chemical agents. Raven Lining 405 can be applied directly to very poor substrates, however if time permits it is preferable to make repairs prior to the epoxy tank lining application.
Cracks in the substrate were expressed using vacuum controlled diamond saws and made good using a high strength epoxy repair mortar. Areas of exposed aggregates were resurfaced using a polymer modified cementitious fairing coat applied by trowel and allowed to hydrate.
To minimise pin holing in the epoxy tank lining all surfaces were double primed using Raven Lining 175 extremely damp tolerant epoxy primer. The first coat of epoxy primer was thinned 50% as per the manufacturers guidance to enhance penetration into the substrate to offer enhanced adhesion.
Throughout the coating application process climatic control in the form of indirect heating and dehumidification was introduced and maintained to ensure the perfect application parameters for the new tank lining. Raven Lining 405 can be applied to damp substrates and in high humidity, however the better the application conditions the better the adhesion of the new tank lining will be.
Raven Lining 405 was then spray applied using our own plural spray equipment to a minimum thickness of 3mm throughout, with additional thickness applied to corners and cracks. The fibre reinforcement contained within Raven Lining 405 gives it excellent tensile strength, providing fantastic reinforcement to static cracks.
Following application the newly applied epoxy tank lining was checked for pin holing using DC holiday spark testers – a single pin hole is a point of failure, especially in aggressive operating environments such as these hot well tanks.
Once repairs had been made where required the new tank lining was post cured using the previously mentioned indirect oil fired heating and returned to service 24 hours later.
The entire project was completed in 8 days over the Easter shutdown, with Corroless Eastern personnel working in two shifts over 24 hours throughout. If the works had not been completed in time the factory would not have been able to open with delay costs running into millions of pounds each week.
We are proud to say that the client was extremely pleased with the works and our teams performed excellently on site, going over and above to get this challenging tank relining project completed on time.
