Bluetooth is basically the same with both infinite infrared transmission, but use different frequency bands. The principle is the use of the infrared spectrum than visible red light is not visible, because infrared light is a kind of, it also has the characteristics of light, it can not pass through opaque objects. Not because we do not see infrared, it means it does not exist, we live around the full infrared light, which may be issued from the light, the sun may also be sent, the user does not need to use the license that you can use the infrared.
Infrared Thermography in BP Amoco---Petrochemical Applications John J. Nyholt NDE Corporate Level III, Inspection Specialist BP Amoco Upstream Technology Group ABSTRACT In the late 70’s, Amoco Oil Corp. began using infrared thermal imaging cameras to detect electrical faults in critical equipment and to improve the reliability of fired heaters. Since then, the company has logged an exhaustive list of benefits from the various applications of infrared technology. As plant operations and maintenance departments learn to rely more heavily on thermal imaging to improve plant reliability, the more entrenched the method becomes in the daily production of petrochemical products. The petrochemical industry continues to find new uses for infrared thermal imaging cameras. At BP Amoco, infrared technology continues to provide opportunities to improve plant operating safety, reliability, and cost of operations. In many plants, implementing new infrared programs has become a priority. While many of our plants outsource infrared services, some maintenance, inspection, and reliability personnel have used the high payback and the on the spot need of infrared thermography to justify buying their own infrared thermal imaging camera systems. From my viewpoint as an in-house nondestructive testing consultant, it’s surprising to see how approvals for infrared thermal imaging cameras are granted before those for other categories of testing equipment. As the number of in-house infrared systems grew in the past few years, the need for in-house specifications and best practices became apparent. At a corporate Infrared User Group meeting in 1998, common goals were set by infrared thermal imaging camera users across the corporation: 1. Standardize on one infrared thermography equipment manufacturer and software package. 2. Identify an industry specific infrared thermography level I and II course. 3. Generate in-house infrared thermography procedures and specifications. 4. Create a liaison between equipment manufacturers and the user. 5. Investigate new infrared thermography applications such as active thermal wave imaging. 6. Provide guidance to plants interested in implementing an infrared thermography program. Since the 1998 Infrared User Group meeting, British Petroleum, Amoco, and Arco have merged into one company under the BP logo. This rapid expansion has strained preventive maintenance and inspection resources, including infrared thermography. New challenges lie ahead for what is now the third largest oil company in the world. Keywords: BP Amoco, petrochemical, infrared thermography, user group, active thermal wave imaging, in-house program 1. ELECTRICAL APPLICATIONS Perhaps the most significant cost saving infrared application in the company, electrical fault detection, motor and transformer condition, distribution lines and substation inspections have saved millions of dollars in cost savings and/or cost avoidance. Routine and pre-shutdown infrared surveys have significantly reduced the number of unscheduled shutdowns and catastrophic equipment damage through risk ranked inspection schemes where critical equipment is ranked under consequence and likelihood of failure. When a simple connection fault is detected and fixed, the worst-case scenario is often used as the avoided cost basis (i.e., unscheduled shutdown of the equipment or even the plant). However while cost avoidance is noted as a successful save, it is usually not as attractive to management as an infrared cost saving strategy would be to their cost of operations. For example, using infrared thermal imaging cameras to save the quarterly amperage consumption may be more valuable than proving what might have been if an urgent maintenance order was not performed. Typical electrical anomalies are shown in Figures 1 and 2 below. Figure 1. Poor Electrical Connection Figure 2. Transmission Wiring Hot Spots 2. ROTATING EQUIPMENT Often used in conjunction with vibration analysis, infrared surveys are used to detect faulty shaft coupling alignment, motor/pump bearings, mechanical seal performance, and cooling channel blockage. Rotating equipment engineering uses infrared and vibration analysis data to trend the estimated remaining life of rotating equipment as well as to track the performance of the equipment under normal loads. 3. HEAT AND PRODUCT LOSS Infrared thermography has been valuable in detecting heat loss from leaking steam traps, leaking steam tracing under insulation, and building heat or AC loss. Infrared is typically used in conjunction with air born acoustic emission testing for detecting leaks in steam traps and other flow control devises. In addition to heat loss, fugitive emissions of process liquids and/or gasses are a major concern for both the petrochemical industry and government regulators. Pollution restrictions and the petrochemical company’s desire to restrict product loss and show itself as a “green” steward of the environment have led to a growing role for IR in this area. 4. TANK PRODUCT AND SLUDGE LEVELS The petrochemical industry obviously makes extensive use of above ground storage tanks in various shape, size and purposes. These storage tanks are predominantly governed by API (American Petroleum Institute) codes. Infrared thermography is one tank inspection method useful for detecting or verifying the product level of in tankage. As sludge, water, and other non-soluble materials settle in the storage tank, they form a distinct boundary layer in the vessel. As these materials vary in density and specific heat values (heat capacity), the boundary layer can usually be seen as a thermal gradient at the outside surface of the tank wall. These sludge level measurements can be used to estimate cleaning intervals as well as the cost of removing solids. Deducting the tank sludge levels from the product level inventory also reduces end of the year taxable inventories. Measurements of product levels also assist in verifying level control performance and inventory control. In one instance, thermography prevented a potentially serious safety instance where it detected a hydrocarbon sludge level that exceeded the manway elevation of a tank scheduled to be opened for inspection. This sludge level is shown in the tank image below (Figures 3 and 4). Figure 3. Tank Bottom Sludge Figure 4. Sludge level Exceeds Manway 5. HEAT TRANSFER Infrared thermal imaging cameras are used to estimate the heat transfer performance and efficiency of heat exchangers, air coolers, and cooling towers. Infrared thermal imaging cameras can also evaluate the tower tray performance in process towers. While fouling in heat transfer equipment can be detected by process flow measurements, the area or point of blockage can be visualized with thermography. In the image below (Figure 5), a mole sieve reactor outlet nozzle is surveyed to study the heat transfer rates during the normal thermal cycling of the process. Nozzles in this service were experiencing thermal fatigue cracks. Figure 5. Heat Transfer at Reactor Outlet Nozzle 6. FURNACE RELIABILITY Thermographic furnace inspections are typically performed quarterly. Short wave thermographic imagers with an optional flame filters are used to scan fireboxes for furnace tube hot spots, excessive scale, coking, flame impingement, and burner performance. Thermal images provides a documented visual representation of where energy losses from poor heat transfer or burner performance are occurring. The Estimated tube temperature measurements are used toward estimated remaining life calculations as well as to identify hot spots that could lead to an unexpected tube failure. Infrared is also used to validate burner optimization adjustments and furnace tube cleaning such as steam out and walnut shell blasting of external deposits. When tube thermocouple readings are in question, Infrared is also used to approximate the actual tube skin temperature. Infrared surveys access the firebox metal temperature (refractory condition), stack skin temperature, and the condition of the firebox doors. In Figures 6, 7, and 8 below, a furnace design flaw created too short of a distance between the east burner and the east wall. Flame impingement on the refractory door caused oxidation of the door structure, causing hot gases to escape through the door. Figure 6. Hot Spot on Process Furnace Door Figure 7. Flame Impingement on Furnace Door Figure 8. Furnace Door Damage 7. HOT SPOT CONTROL OF REFRACTORY LINED EQUIPMENT Petrochemical plants, particularly refining, use refractory lined vessels and piping systems in processes that involve temperatures that exceed the design metal temperature of most carbon steel materials. Two design metal temperature limitations occur for each type of carbon steel; one for stress rupture failure, and one for high temperature hydrogen attack. Infrared thermal imaging cameras are crucial to the safe operation of these systems and infrared inspection intervals vary. Many refractory lined reactors and catalytic cracking piping systems are surveyed weekly. Where fast detection of refractory loss is desired, equipment may be painted with a temperature-indicating paint that changes color when a maximum temperature is reached. Follow-up thermal imaging is then performed to confirm the hot spot condition as in the images below (Figures 9 and 10). Figure 9. Refractory lined Reactor Vessel Figure 10. Refractory Loss in Bottom Head 8. INFRARED THERMOGRAPHY PROGRAM Setting up an infrared program in the petrochemical industry is probably similar to doing so in the utilities, automotive and other industries. Perhaps the barriers to a successful company wide program are similar as well. Infrared thermal imaging cameras, software, training, and support are expensive, and the cost of using outside service providers is also higher than most other routine inspection methods. Subsequently, maintenance and inspection personnel interested in starting an in- house infrared program usually have a tough sell with management. Both human and material resources are usually stretched thin, and management tends to be suspicious of schemes that seek additional resources (all capital requests claim a high payback). In BP Amoco, there is a mix of plants that use outside infrared vendors, in-house thermographers, and sites that still seldomly use thermography. However as plants become more educated on extended value of infrared, they tend to purchase their own infrared thermal imaging cameras in order to have them available at all times. With the merging of three major oil companies, defining the size, geographics, and variety of petrochemical plants within the new company can be difficult. Fortunately BP Amoco makes extensive use of electronic networks that identify target audiences and work well for sharing information and resources. As the appropriate people from each company join these networks, an accurate assessment of infrared usage across new organization will occur. One particular benefit of such networks has been accelerated information flow. By networking, the education step for infrared thermal imaging camera approvals appears to have been significantly reduced. The benefits have become well documented. In 2001, a corporate infrared project will be proposed to leverage the resources and knowledge of the entire group towards setting up in-house infrared programs as well as supporting sites that use external vendors. Such leverage is also useful in dealing with infrared equipment and software suppliers. At group rates, we can reduce capitol costs and persuade industry specific product development. infrared supplier alliances also provide for equipment and software standardization, reducing the need to support a wide variety of systems. In our opinion, the following steps are required for an infrared program: 1. Define the goals of the program and issue a mission statement for management approval. Define responsibilities during this stage. 2. Evaluate instruments, tools, other equipment and techniques that will be used. 3. Define and submit funding requirements. Select equipment based on funding approval. 4. Select data collection points. What is the criticality of the equipment? What are the specific consequences of failure? What is the likelihood of failure? 5. Develop reporting practices. What does management need to know to make decisions? Who needs access to the information? 6. Build data bases and track histories. Identify critical equipment information from trending. Establish data acceptance criteria and inspection intervals. 7. Ongoing practice. Recognize that there will be a learning curve that will cause changes to the program. 9. PETROCHEMICAL OPPORTUNITIES FOR INFRARED TECHNOLOGY At a time when the petrochemical industry is striving to improve the safety and reliability of aging assets, cost cutting pressures are straining maintenance and inspection resources. Maintenance and inspection philosophies are turning away from prescriptive scheduling in favor of more risked based maintenance and inspection schemes. These schemes typically reduce and focus resources to exactly where and when they are needed, which in turn will optimize their equipment reliability programs. For each piece of equipment, the consequences and likelihood of failure are risk ranked, and the limited maintenance and inspection resources are targeted on priority equipment. The down side is that these strategies reduce the amount of available downtime for maintenance and inspection, and there is a heavier reliance on the probability of detection (POD) of the inspection methods used. Inspection methods that can inspect equipment on-line are then of particular importance as they are capable of detecting problems during operation, monitor known problems, and prevent unscheduled shut downs. Infrared thermography is among those technologies that could be used as a nondestructive testing measure. To date, infrared applications within BP Amoco have been limited to “passive infrared”; where objects are viewed in the infrared spectrum at their steady temperature without altering the temperature or other attributes of the target for the purpose of extracting further information. However “active infrared” is another area of infrared technology that could also be useful to the petrochemical industry. Active infrared is as a means of extracting sub-surface information of a component by manipulating the steady state temperature of the specimen while observing the infrared response at the object surface. Specialized infrared cameras, equipment, and image enhancement software have advanced and expanded active infrared applications, some of which are capable of determining material properties or flaw detection. All NDE flaw detection methods involve the indirect measurement of material properties or characteristics by exposing the material to some sort of probing medium (sonic energy, radiation energy, magnetic and electrical energy, or other media), obtaining some kind of response of the probing medium to changes in the materials continuity, and interpreting these responses as evidence (or absence) of indications. Active infrared follows this methodology by inducing a change in temperature (delta-T) into the subject material, and observing sequential thermographic images at the material surface as it returns to its steady state temperature. as thermal energy is added (or removed) suddenly, a thermal pulse traverses through the material in accordance with its density and thermal conductivity. When this thermal pulse encounters a planer boundary (back wall, lamination, pitting, etc.), it will reflect and return to the outer surface. When detected by an infrared imager, the time of flight (TOF) may be compared with a standard, or the different thermal transients may be qualitatively compared to that of the back wall. Various material conditions can affect the extent and timing of thermal gradient formation at either surface (front or back) of the test specimen. Passive infrared by itself will only detect these conditions when they are severe enough to provide a delta-T at the steady state (operating) temperature, and only while the equipment is on-line. Material thickness, pitting, or other defects are not likely to be detected. Active infrared could be used as a screening tool that could be applied more globally that pulse-echo ultrasonics. The amount of specimen surface area tested in a single application would be limited to that that could be instantaneously flash heated or cooled and viewed by an infrared imager within a reasonable incident angle to the specimen surface. However active infrared and pulse echo ultrasonics each have advantages and limitations: • Thermal waves are highly attenuated and therefore limited by material thickness (typically 3/8” in steel). • Quantitative wall thickness measurements would not be practical without complex control of test variables and thermal wave imaging equipment and analysis software. • In pulse echo ultrasonic testing, contact with the material surface is required. Temperature limitations that practically do not exist in active infrared would impede or prevent testing. • In most cases pulse echo ultrasonics will not detect ID deposit buildup. The high acoustic impedance between the base metal and deposit would result in nearly 100% reflection of sound at the base metal to deposit interface, which would not indicate the presence of the deposit. By comparison a thermal wave would be absorbed by the deposits, as indicated by an increase in the time required for the outer surface to return to its steady state temperature. • Compared to the Passive infrared method for furnace tubes, active infrared would detect smaller amounts of deposits earlier than Passive infrared. When the furnace is out of service deposits and material thinning could be screened by active infrared, followed by pulse echo measurement of excessive material thinning. Active infrared techniques vary in sensitivity and complexity. The easiest, although least sensitive method is the “Step” method, which is performed as the piping or equipment is brought on line. The process heat provides a delta-T, with higher thermal gradients appearing at thin spots, refractory loss, or heavily pitted areas before appearing at the background (full thickness) area. Localized heavy internal deposits are also detected as they insulate the metal from the heat of the process. The local outer surface of material reaches the steady state temperature after the non-deposit areas. Another version of the step method involves heating or cooling the surface of a specimen without regard to the time or duration of the induced delta-T. In this technique, local heating or cooling from water, steam, vapor mist, or other uniform media produces a delta-T that saturates the full thickness of the material. The source is then removed and the material surface monitored by an infrared imager for thermal gradient patterns. This technique may be the most practical active infrared as it is the most simple to apply and can quickly estimates the material condition for detecting trouble areas that could be followed up by other NDE methods. Recently, hand held magnetic induction heaters have been successfully used to detect corrosion while using standard infrared imagers and without the need for advanced image enhancement software. Step method experiments have successfully detected 25%-75% through wall indications in a .25” thick carbon steel specimen. The most reliable, repeatable, and quantitative active infrared method is the Pulse Echo Thermal Wave Imaging system (PETWI). In this technique, one or more 6000-joule flash lamps are “pulsed” at the specimen. The distribution of the light, source to object distance, and interference from external infrared emitters are controlled by a light box containing the lamps and an infrared imager is incorporated in the rear of the box. A PC utilizing special thermo graphic imaging software controls the heat of the flash, pulse timing, and image capture rate. Precise control of system events, and the use of image enhancement options provide for expanded data collection and analyses techniques. For example, data displayed as energy level histograms provide considerably more data interpretation than is available by simply viewing and interpreting infrared images. The speed of active infrared is faster than that of conventional ultrasonics, but would not match magnetic flux leakage for tank bottom inspection or automated digital radiography for piping. An example of thermal wave imaging of a pipe with internal deposits is shown in Figure 11 below. Figure 11. Thermal Wave imaging While active infrared has yet to prove itself for accurate thickness measurements, the likelihood of its success is increasing. If accomplished, we may be able to take accurate thickness measurements on line, regardless of the objects temperature. For now, current active infrared techniques are capable of making qualitative determinations of thinning, pitting, laminations, deposit build up (or absence), refractory loss, and suspect areas of corrosion under insulation (through detecting soaked or poorly performing insulation). As with any new NDE application, the advantages, disadvantages, and application boundaries for each technique need to be defined, and reassessed as developments occur. 10. CONCLUSIONS Petrochemical maintenance and inspection strategies will continue to discover new applications for infrared thermography. Temperature is often an indicator of material, process, and mechanical conditions. When used in conjunction with an organized infrared program, infrared technology can be properly positioned into each plant’s maintenance and inspection strategy without re-inventing the wheel. In order to reach its full potential in the petrochemical industry, industry specific infrared applications would also have to be defined and studied. For example, active infrared applications for steel and steel alloys need to be refined and their limits of practical use defined, data base technology should be developed for trending the life of refractory lined equipment, and infrared imager technology should be developed with petrochemical needs in mind. Above image used with permission from Thermal Wave Imaging, Inc.
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