Inspection of Pipes in Furnaces or Heaters and the Evaluation of Remaining Life

As seen in the May / June 2014 volume of the Inspectioneering Journal
Understanding the variations associated with the remaining life analysis of furnace or heater tubes is a critical element for the quality and accuracy of your predictions. Furnaces or heaters are vital equipment, in most plants. A failure in a furnace or heater tube can result in the loss of human lives, millions in production losses and the costs associated with the replacement of failed items. Inspections are usually carried out to obtain data that allows to reduce the variations in the engineering analysis when determining the current level of damage and the remaining life of the equipment, allowing to take appropriate actions, long before reaching a failure in a tube.

Typical inspections include ultrasonic measurement of wall thicknesses, measurement of the circumference (diameter), terrain metallography, replicas, etc. Sometimes, the inspection of a furnace or heater tube is limited, due to its accessibility. The following interview with Rich Roberts, provides answers to some questions that our readers may have, with respect to these small tools (pigs), very specially designed, with non-destructive testing technology, which can inspect practically the entire tube, from inside . We hope you find value in this interview. Please send us an email, if you have additional questions regarding this topic or any other topic related to asset integrity management. We will try to obtain the requested answers. The inspection of a furnace tube or heater is limited, due to its accessibility. The following interview with Rich Roberts, provides answers to some questions that our readers may have, with respect to these small tools (pigs), very specially designed, with non-destructive testing technology, which can inspect practically the entire tube, from inside . We hope you find value in this interview. Please send us an email, if you have additional questions regarding this topic or any other topic related to asset integrity management.

We will try to obtain the requested answers. The inspection of a furnace tube or heater is limited, due to its accessibility. The following interview with Rich Roberts, provides answers to some questions that our readers may have, with respect to these small tools (pigs), very specially designed, with non-destructive testing technology, which can inspect practically the entire tube, from inside . We hope you find value in this interview. Please send us an email, if you have additional questions regarding this topic or any other topic related to asset integrity management. We will try to obtain the requested answers. with respect to these small tools (pigs), very specially designed, with non-destructive testing technology, which can inspect virtually the entire tube, from inside. We hope you find value in this interview. Please send us an email, if you have additional questions regarding this topic or any other topic related to asset integrity management. We will try to obtain the requested answers. with respect to these small tools (pigs), very specially designed, with non-destructive testing technology, which can inspect virtually the entire tube, from inside. We hope you find value in this interview. Please send us an email, if you have additional questions regarding this topic or any other topic related to asset integrity management. We will try to obtain the requested answers. if they have additional queries regarding this topic or any other topic related to asset integrity management. We will try to obtain the requested answers. if they have additional queries regarding this topic or any other topic related to asset integrity management. We will try to obtain the requested answers.

IJ: What are the most recent non-destructive testing techniques (and how are they) helping to deliver critical information for the engineering evaluation of the coils in the furnaces or process heaters?

RR: The inspection of the coils in furnaces or process heaters has historically been a challenge for the owners / operators of them, due to limited physical access, especially in the convective zone. The traditionally available alternatives of non-destructive testing (for example: manual ultrasound), try to inspect from the outer surface of the tubes, but access is normally available only for the radiant section tubes, leaving the convective zone without inspection. Even more important, conventional non-destructive tests require time availability and the results cover only 2 to 3% of the surface of the coils. Engineers who try to perform a “fitness-for-service” evaluation based on manual measurements must assume a large amount of data, to complete the information requirement. The use of the ultrasound-based inspection technology of the “Smart Pig” eliminates the need to assume information, to perform the evaluation, since it provides 100% coverage of both the convective and the radiant tubes. inspection technique, with its higher level of reliability of the analysis of “fitness-for-service” ??, allows plants to operate furnaces or heaters for longer periods and generally, with greater demand.

IJ: How many ultrasonic sensors (UT) are needed in the “Smart Pig” ??, to ensure adequate inspection coverage, when inspecting coils in furnaces or heaters?

RR: The diameter of the coil tubes, should dictate the number of UT sensors that the “Smart Pig” should have, for example, an oven or heater that has 3 “diameter pipes in the coil , must have at least forty-eight (48) sensors on the circumference, while a 12 “nominal diameter tube must have one hundred and sixty-eight (168) readings taken at the circumference. “?? You must take four (4) samples per inch (25 mm) of advance, on the axial axis.

IJ: What is the maximum diameter of the ultrasonic sensor (UT) in the “Smart pig” that ensures at the same time, an adequate resolution and an adequate inspection sensitivity?

RR: The physical dimension of the deterioration mechanisms, such as: pitting, localized corrosion or mechanical damage, can be very small and in positions where manual external ultrasound access is impossible. The “Smart pig” applied from the inner surface must have UT sensors with a maximum of ¼ “diameter (or be smaller), to ensure adequate resolution and sensitivity, to detect these defects. detection, can be compromised if the UT sensors have a larger diameter.

IJ: What better information / data do we need, with this advanced technique of non-destructive testing, so that the engineering evaluations are more adequate, in the coils of the furnaces or heaters?

RR: It is the critical and delicate balance of maintaining both the accuracy and the coverage of the inspection surface. If one or both of these critical elements are not present, the results of the engineering evaluation will be compromised. The mechanisms of deterioration in the coils of furnaces or heaters are generally located in a specific area of ​​the coil and the physical dimensions of the defect (example: sting, dent) can be very small. Without 100% coverage of the inspection, a defect can be undetected, generating a premature failure of the coil.

IJ: What additional development, in non-destructive testing techniques, are required to improve engineering evaluations in furnaces or heaters?

RR: Smart pig technology, designed specifically for the inspection of the coils of furnaces or heaters, has advanced rapidly in recent years and continues to do so today Many furnaces or heaters in the chemical or petrochemical industry , have coils with 2 “nominal diameter tubes, the” Smart Pig “?? for these small tubes are in development process and it is expected to be available in a few months.

IJ: What typical industrial furnaces or heaters justify these complex remaining life analyzes and specialized inspections? Why?

RR: There are many different types of furnaces or process heaters through refineries and chemical plants. Their designs are specific to the process in which they will be used. Many furnaces or heaters operate at elevated temperatures and pressures, making the coils susceptible to both corrosion and creep. The UT technology tool “Smart pig” is able to detect and quantify the damage caused by both, having the ability to import all the inspection data that captured the “Smart pig” ?? to a computer program and from there, perform an engineering evaluation, it is critical to understand the degradation of the coil and its remaining life.

IJ: Should engineering information be submitted in advance, to give the necessary address to create the inspection strategy?

RR: Before starting any inspection, it is critical that the operators of the plant that manages the furnaces or heaters, share information related to alterations in the operation of the furnace or heater, such as high temperatures, operating exits, etc. This ensures that the data analyzer and the engineer, who are working with the inspection data, pay attention and focus on possible damage that could have been caused as a result of the operational history of the asset. Additionally, it is critical that the company that provides the inspection service has a strong engineering and technical knowledge base of the furnaces or heaters, to ensure the customer, that all these elements combined, deliver the best result with respect to the investment made.

IJ: Which dictates the degree of accuracy required in the inspection and in the results?

RR: As the old proverb says “If garbage comes in, garbage comes out.” If the accuracy of the inspection results is questioned, so will the result of the engineering evaluation. tested for accuracy and having repeatable results, it is critical to ensure that engineering recommendations are reliable Many customers nowadays, proactively conduct live assessments of the performance of “Smart Pig” service providers ?? What I believe is essential to qualify both the technology and the capacity of the supplier, before it reaches the field.

 

IJ: What type of access is necessary, considering the different types of tube inspection technologies, in furnaces or heaters?

RR: The designs of the coils in standard ovens or heaters typically have flanges on both ends, which allows for a mechanical cleaning of the interior surfaces. The use of the “Smart Pig” for the inspection of this type of coil design is quite direct, especially that the “Smart Pig” ?? It is sent through the coil directly after the cleaning “pigs” have done their job. More complex furnaces or heaters, which have Common Headers, were a challenge, both for cleaning and for inspection, but with the system of “snorkel (Header Deliver System)” ??, which is available in the market, the cleaning and inspection of these ovens or heaters have become routine.

IJ: How long does an inspection take?

RR: The “Smart Pig” travels at a typical speed of 2 feet per second (0.6 meters per second), providing at the same time, a 100% coverage of the surface, a typical length of a coil, of the order of 366 meters (1200 feet), requires about 10 minutes, to run from one end to the other.

IJ: What are the surface preparation requirements?

RR: The interior of the coils is cleaned regularly (decoded) to ensure efficiency in heat transfer. This cleaning is also a requirement before using the inspection with the “Smart Pig” ?? The technology of the “Smart Pig” ?? It is also able to confirm that all foreign material (example: lamella, coke, etc.) has been removed from inside the coil.

IJ: What is the total cost of implementing the non-destructive test and the engineering evaluation? How much value does it have for the operator?

RR: The cost is handled by several variables such as the complexity and length of the coil, diameter of pipes, etc. An operator interested in knowing the cost of the service must provide plans or detailed drawings of the coils and complete the PJQ (pre-job-questionnaire); these elements will allow the commercial representative of Quest Integrity, calculate the fixed base value for the inspection and for the engineering evaluation. Retro-feed from several customers indicate that the cost of applying the Smart Pig inspection is a small fraction of the cost compared to a failure of the furnace or heater or a catastrophic failure, in the worst case scenario.

IJ: Considering that Smart Pig technology means complex instruments, what kind of formal procedures and technical training should a company deliver to its field staff, in order to ensure accurate results in inspection reports?

RR: Without a doubt, the “smart pigs” have advanced technology, which requires specialized training, to operate them during data collection, formal detailed procedures are a natural requirement of the non-destructive testing community, but even more, the The importance of a well-documented process is essential when applying these complex tools.Most importantly, training the data analyst is critical to ensure that they understand the process and the specific characteristics of the mechanisms of deterioration commonly found in furnace coils. or heaters We have concluded that there is a close relationship between the internal level III staff and the reliability engineers of furnaces or heaters in the plants, when preparing the training plan of the field personnel.We also ask clients to audit vendors of this technology to ensure that they have robust procedures, proper training and examination certificates.

IJ: How do you see the future of the companies that provide inspection services and engineering evaluation services, in furnaces or heaters?

RR: I see a much closer relationship between customers and non-destructive testing companies and engineering services. The creation of relationships with the owner / operator of the furnaces or heaters increases the familiarity with the equipment and the personnel in charge, improving the type of information to be delivered. The relationship also assures the client, access to historical data and engineering evaluations that were provided in the past, which is normally kept by the service provider in archives.