Why regular decoking and tube inspection should be part of your health and safety plan
27 April 2020
Fired heaters (or furnaces) are an essential asset in most petrochemical plants and oil refineries. They are used in heating, vaporisation, and thermal cracking processes to separate the product into liquids or gases which can then be used to make many different products. Failure can have major impact on safety, efficiency and finances.
Codes, standards and safety requirements introduced in the late 1990s have brought greater emphasis on safety and have led to changes in fired equipment design, operation and maintenance. Every fired heater must have some type of safety system in place for any potential failures, but the best and most effective measure is the prevention of hazards by way of a maintenance and inspection schedule.
The greatest risk associated with fired heater failure involves explosion or tube ruptures. Even minor incidents can result in severe damage of process units forcing outage, which in many cases means emergency shutdown of the entire plant. In most cases, actual tube failure or even severe tube deterioration are responsible for outage of a fired heater. It is not only an economical concern, but also a matter of health and safety- An unpredicted tube rupture can lead to disastrous explosions and severe human injury and loss of life.
A quick internet search will uncover a huge number of cases of oil refinery explosions that are caused by tube rupture. When a tube ruptures, exposing the media inside, it causes a very combustible combination of process media and air to mix. The smallest ignition will cause a catastrophic explosion. Inadequate awareness or management of corrosion hazards are a contributing factor in many of the cases.
The build-up of coke and scaling in heater tubes is one of the mains reasons for reduced efficiency and dramatically reduces profitability and increases risks of tube rupture. Coke, deposited in the tubes by the heating process, builds up and acts as an insulator, restricting heat transfer to the product and resulting in even higher tube surface temperatures and reduced thermal efficiency. Operating temperatures are increased in an attempt to maintain the output, however the longer the running length of a furnace, the more likely it is that one or more tubes will exceed a critical surface temperature. Over time, this causes overheating in some tubes or “hot spots” which can seriously diminish the life of the tube and cause coke to build up at a quicker rate. Overheating is sometimes a result of flame impingement of the tube from the burner. This is when a flame actually touches or engulfs the tubes or their supports. It can be caused by debris lodged in or around the burner, coke build up on the burner ports, burner misalignment, or deterioration the burner tile block. In refineries flame impingement is a frequent cause of coke build-up. As well as causing blockages, coke can contribute to various corrosion mechanisms, including sulphidation, carburisation, embrittlement and metal dusting. The risk of tube rupture becomes higher and higher within this dangerous cycle.
Preventative maintenance by regular decoking and inspection of furnace tubes is the most effective way to combat these particular risks and should be an integral part of every fired heater safety system.
Mechanical decoking, sometimes known as “pigging”, has become the main means of coke removal and tube inspection in many industries. It is less likely to damage tubing and is more environmentally friendly and cost effective than other methods such as chemical or combustion cleaning.
WORLD-CLASS DECOKING AND INLINE INSPECTION TECHNOLOGY FROM COKEBUSTERS
Cokebusters is an international company specialising in the mechanical decoking and in-line inspection of process piping within fired heaters, steam generation boilers, transfer lines and pipelines. From two headquarters in the United Kingdom and the United States, Cokebusters are able to consistently deliver high quality services to the oil and petrochemical industries worldwide. Teams of highly skilled and experienced operators provide outstanding service with a focus on safety, efficiency and quality.
As well as decoking, Cokebusters offers Coke Removal Verification and Tube Integrity Analysis via the Merlin “Smartpig”. Merlin is a division of Cokebusters, providing inspection technology that is constantly developing in terms of capability and performance.
The “Smartpig” was developed to overcome difficulties with inspecting certain furnace types. Driven by water through the internal passageway of a pass or coil, ultrasound technology is used to internally scan fired heater tubes. Measurements and surface condition data is recorded directly to the pig and downloaded to a laptop for analysis following the inspection. Problems such as material loss, creep, pitting and other irregularities can be detected and highlighted allowing remedial action to be planned and executed to avoid unsafe conditions and process failure.
NEED MORE INFORMATION?
Cokebusters unique combination of new technology, quality, safety and experience results in a safe, environmentally friendly and effective mechanical decoking system and inline inspection service to industrial facilities worldwide. Find out more at www.cokebusters.com