Fuel is one of the greatest human inventions since the beginning of time. Fuel propels automotive and locomotives. The natural resource governance institute defines oil and gas as hydrocarbons. These organic compounds that make up the fuel are obtained from the firmness of organic material over millions of years. The method of extracting oil out of the ground and to the consumer is segmented. There are upstream operations and downstream operations which includes exploration, production, refining, marketing, and distribution in the listed operations. The oil and gas national companies play a big role in the economy of a country as opposed to other small players in the market. The oil and gas found in the ground comes in different grades or assets. The primary way to describe the quality of oil is in terms of its sweetness and heaviness. The syrupiness of oil refers to the amount of sulfur in the oil. The less the amount of Sulphur in the oil, the sweeter it is and as a result it requires less processing before use and it proves more valuable to the consumer (Popool, et al., 2013). Lighter crude can be polished into higher value products such as the gasoline or petrol used by car owners. The heftier crude drifts more slowly and has more solicited chemicals that must be refined out. There is a standard degree based importance scale that associates the relative density of the various crudes. The American Petroleum Industry (API) sets grades for light crude at 31.10 and the heavy crude measures at 22.30.
Corrosion and its impact on the industry
Corrosion is a paramount problem encountered in the oil and gas industry. Oil and gas pipelines, refineries and petrochemical plants have serious corrosion problems. Internal corrosion in oil and gas industry is generally caused by water, carbon dioxide and hydrogen sulfide and also can be aggravated by microbiological activity (Papavinasam, 2000). The flow regimes of multiphase fluids greatly influence the corrosion rate. At high flow rates, for instance, flow induced corrosion and erosion corrosion may occur while at low flow rates, pitting corrosion is much more common. Corrosion is related to the amount and nature of the sediments. High velocity flow tends to sweep sediments out of the pipeline, whereas low velocity allows sediments to settle at the bottom, providing sites for pitting corrosion. Corrosion of metal in the presence of water is a common problem across many industries. Most oil and gas production factories have water as a by-product which makes corrosion a pervasive issue across the industry. The age and presence of corrosive materials can demonstrate a huge problem. These industries depend on carbon steel alloys as primary backbone. The stakeholders in the oil and gas industry have taken up measures to combat the corrosion for there are huge economic losses in the industries due to extremely high corrosion (Fink, 2012). The use of corrosion inhibitors has been one of the most commonly used measure. There are several types of corrosion inhibitors. These inhibitors can be classified as anodic, cathodic, or mixed corrosion inhibitors. Some could be organic or inorganic, focusing on their chemical properties. The general inhibition mechanism such as the chemical adsorption of the inhibitor on the surface of the metal and forms a protective thin film which protects the underlying metal from corrosion.
Corrosion of steel is an electromechanical process that involves the transfer of electrons from iron atoms in the metal to hydrogen ions or oxygen in water. The corrosion reaction of iron with acid is as described in the following reaction equations. The consumption of the electrons by the acid generates hydrogen gas which is a cathodic process that results in reduced protons.
Acid is not the only corrodant in the steel pipes used for production and transportation of oil and gas. Another common cathodic process is the reduction of oxygen which can take place at a location different from that of iron dissolution.
Steel is an alloy formed when iron is alloyed with a small percentage of carbon. It is a stronger metal than iron and hence suitable for oilfield use. More components can be added to iron to enhance corrosion resistance properties. The plain carbon steel pipes are processed by annealing, normalizing, spherodizing and quenching (Sabbah, 2016). There is a group of iron-based alloys that contain a minimum of about 10.5% chromium making them have a protective self-healing oxide film, which is the reason why this group of steels have the stainless or corrosion resistance property. There are two types of corrosion experienced in pipes used to transmit petroleum and gas. The internal corrosion of the transmission pipelines occurs when the electrolyte is contaminated by ionic species known as corrodants (Smart & Pickthall, 2004) The corrosion of the pipelines takes place at the rate of the microbial counts and the attributes of water. Corrosion can be encountered on the outer part of the pipelines. This is countered by coating the pipes with alloying materials or other non-corrosive materials (Beavers & Thompson, 2006).
It is the act of measuring the corrosion level of process stream conditions by the use of “probes” which are inserted into the process stream and which are continuously exposed to the process stream condition. The area of corrosion calculation, monitoring, and prevention spans a very large spectrum of technical activities. There are technical options such as the cathodic and anodic protection within the sphere of corrosion monitoring and control. Other means of prevention and control include the selection of material used in the plants or pipelines, the dosing of the chemicals, and the application of the internal and external coating. The corrosion measurement employs a variety of techniques to determine how corrosive the environment is and the exact rate of the loss of metal from the structure is experienced. A quantitative method is employed to perform the corrosion measurement. This method seeks to evaluate the effectiveness of corrosion control and prevention techniques. The method also provides a tone of feedback to advice on the way forward in terms of corrosion control and prevention. Such feedback is needed to ensure that the corrosion control and prevention methods can be optimized or to allow the management make better decisions on the strategies and techniques used in the measurement. There are myriads of techniques employed to measure corrosion and they are categorized as
- Non-destructive testing
- Analytical chemistry
- Operational data
- Fluid electrochemistry
- Corrosion monitoring
Some of the corrosion measurement techniques that are used are on-line and they can be exposed to the process stream. Other measurement techniques seek to provide off-line measurements such as those determined in a laboratory analysis. Some of the methods are in a good place to provide a direct measure of the metal loss or corrosion rate where as others are used to infer that a corrosive environment may exist. Corrosion, as mentioned earlier, is monitored using probes. These probes can be in the form of mechanical, electrical, or electrochemical devices. The corrosion monitoring methods alone tend to provide both the direct and the online measurement of the metal loss or the corrosion rate in the industrial process systems. In practice, these techniques are not employed in isolation. The inspection and maintenance program for a given industrial facility seeks to merge the measurement elements along the line of online, offline, direct, and indirect measurements such that,
- Corrosion monitoring can be direct and online
- Non-destructive testing can be direct and offline
- Analytical chemistry can be indirect and offline
- Whereas operational data is indirect and online
The data obtained from the four sources or combinations listed can be used to draw meaningful conclusions about the corrosion rates in the equipment and various components that form the infrastructure as well as the process system. The data is analyzed in a well-controlled and coordinated program to determine how corrosion can be effectively minimized.
There is a great need for corrosion monitoring. The level of corrosion in the infrastructure of an industrial plant dictates how long any process equipment can be useful and safe to use and operate. In economics, it tends to determine the rate at which the value of the given component, equipment, or infrastructure depreciates. The measurement of corrosion and the action to remedy the high corrosion levels permits the most cost effective plant operation to be achieved while reducing the life-cycle costs associated with the operation. Some of the ways in which performing corrosion monitoring is important are:
- The techniques alert the on-site or off-site engineers and operators that the damaging process conditions exist and they may result in a corrosion-induced failure.
- One can study the correlation of changes in process parameters and determine, from analysis and evaluation, their effect on the system corrosion level.
- There techniques enable an operator to diagnose a particular corrosion problem in the system by identifying the causative agents as well as the rate of control parameters such as flow rate, pH, temperature, and pressure.
- Corrosion monitoring enables one to evaluate the efficiency and effectiveness of a technique as well as determine the optimal applications. Some of the control and prevention techniques are chemical inhibitions.
- By providing the management with information relating to the maintenance requirements and on-going conditions of the infrastructure and industrial equipment.
The corrosion monitoring techniques can be utilized virtually in any industry where the corrosion prevention is a paramount requirement. In the oil and gas production industry, it is implemented in flow lines, water systems, transport pipelines, water injection facilities, vessels, processing, water systems, chemical injection systems, drilling mud systems, water wash systems, desalters, processing, and gathering systems. In practice, it is common to find about two or more of the techniques combined so as to provide a wide base for data gathering. The process of corrosion monitoring seeks to find solutions to extent at which corrosion occurs, its causes, and whether it increases by the day. Such information is important when one needs to qualify the cause of corrosion and perform a quantitative measure on its impact on the industrial processes. Corrosion monitoring is key to fighting corrosion. Consistently monitoring corrosion ensures that there is an economic benefit to the user (Samples, 2007).
The corrosion inhibitors can be acquired commercially and are useful in the oil and gas industry. They are unique mixtures that may contain surfactants, film enhancers, demulsifies, or oxygen scavengers, in addition to the inhibitor moiety. The majority of the corrosion inhibitors used currently have some nitrogen components that contain molecules (Ahmad, et al., 2014). They can be classified as salts of nitrogenous molecules with carboxylic acids, and nitrogen quaternaries. One can also find other non-nitrogenous inhibitors such as Sulphur, oxygen atoms, or phosphoric components being sold commercially. These are, however, less frequently used. Some of the key factors to consider when implementing corrosion inhibitors are:
- Compatibility with the expected environment
- The inhibitor should be economical
- Should provide great protection of the metal
- Must not cause any significant undesirable side effects which may affect the operation or process of transporting or producing the oil and gas.
The properties of a corrosion inhibitor are crucial as from the standpoint of handling the material, the reaction of the inhibitor with other chemical like demulsifies, dispersants, and scale inhibitors. It is vital to consider the thermal stability of the inhibitor and the effect of mixing it with the environment. One can determine the impact by testing its solubility, water tolerance, emulsion & foam formulation.
Corrosion monitoring techniques
There are many techniques employed in corrosion monitoring. Some of the techniques commonly used in the oil and gas industry are:
- Corrosion coupons for weight loss measurements
- Electrical resistance (ER)
- Linear polarization resistance (LPR)
- Galvanic (ZRA)
- Hydrogen penetration
- Sand and Erosion
There are more techniques involved as analysts keep defining newer and better methods of solving certain problems. The ER, LPR and the corrosion coupons are the most commonly used techniques in industries that perform critical corrosion monitoring in their infrastructure. These techniques are easily deployed in the oil and gas industry as they are easy to understand and implement, enable equipment reliability in the field environment over many years of operational application. The provide easy to interpret results and their measuring equipment can be made intrinsically safe for hazardous area operation. The users tend to have experienced significant economic benefit through reduced plant down time and the resultant plant life extension (Samples, 2007).
Internet of Things
The Internet of Things is a trending technology theme that is affecting all the industries in a great way. The oil and gas industry has embraced the technology to enable them improve on a few areas. One of the key areas is tracking the transmission of oil and gas which are transmitted using pipes. These pipelines as discussed earlier tend to corrode and the corrosion needs to be monitored for scheduled or impromptu maintenance. Efficient maintenance guarantees that the oil and gas are transmitted from one point to another successfully. According to Marc Benioff, the IOT tends to be the ground zero of a new phase for the global transformation as powered by technology innovation, that generates the significant economic opportunities and reshaping industries. The Internet of Things (IOT) has the ability to change the capability of businesses in their monitoring and measurement of an unlimited number of items. The use of IOT in the oil and gas industry will aim at overcoming a number of challenges encountered over decades. It is estimated that the next generation of internet users may not be humans but human inventions such as machines and robots. The oil and gas industry will tap into the benefits of using IOT if it seeks to perform remote monitoring and measurement that can help vastly reduce cost. The reduction in cost enables passive monitoring which is an ongoing process. Based on the reports obtained when utilizing the IOT technologies, the human users can intervene and solve major issues promptly.
The natural gas is obtained from natural fossil fuel. The location of such an extraction site is in a remote area away from human settlement. There is critical infrastructure implemented for the extraction process. There is need to monitor the operation of the infrastructure for the maintenance and management of the plants. These plants tend to be located in dangerous, extremely remote environments and a large workforce is deployed to ensure the extraction process is efficient. As a result of the extraction procedures and activities, there are potential explosions anticipated in the risk management portfolio. There could be a sudden release of gas under extreme pressure that can result from normal extraction operations and for other on-site activities. The same plant could introduce an ignition source to the extremely flammable environment. There is need to closely monitor such potentially explosive environments for the presence of flammable substances. The oil and gas industry is monitored by many bodies, both governmental and non-governmental, to ensure that the health and safety practices are upheld. The oil and gas industry has devised many methods to conduct scheduled maintenance, impromptu or on-event maintenance procedures to ensure safety but these methods hardly provide a 100 percent guarantee on safety. The implementation of IOT advances in remote connectivity and innovations in monitoring techniques has significantly improved the efficiency of observation and risk monitoring and management.
Deployment of IOT in the oil and gas industry
Deploying IOT technologies for remote monitoring will effectively perform remote asset management through the interconnected infrastructure. Such a deployment will greatly improve the oil and gas industry operations. Remote monitoring may require laying off of some staff but that greatly cuts on costs which is an economies of scale. The implementation inherently reduces the risk of casualties when an emergency incident occurs. Fewer people are on the ground or exposed to risks and hence the reduction on the risk incurred. The management or operations managers are always seeking to find out if the assets are working well and if there are any malfunctioning assets. This kind of information is key in decision making. The IOT technologies are well implemented to provide for remote asset management and reporting by telemetry. One seeks to check the assets for their working conditions, their costing time and money as opposed to installing a human being or employee in a dangerous environment to do the reporting and logging. The remote monitoring and management reduces costs and improves the organizational risks associated with having employees on the ground.
The technical bit requires that a software be run on a core server of the business. Such a server is mainly installed in the headquarter offices. As a result, employees and site engineers do not need to a have a local copy of the software on their local hosts. Implementing this client-server based system saves the company the cost and necessity of having a human operator on site to manage hardware and related data. The Client-Server model stores data away from the entry point guaranteeing a higher level of security. The plant Information Technology (IT) team can them access and analyze the data using a myriad of devices. All these devices need to be connected to the internet. More than one person can send information on different assets to the server using different platforms despite the geographic disparity. Information on different risks and assets is obtained as promptly as possible, making the decision-making process more efficient and effective. A faulty system would be shut down remotely to avoid explosions or spillage during transmission of oil via pipelines in remote areas. The oil and gas industry has a wide infrastructure coverage for the pipelines. It is very difficult to locate a fault on the pipeline and it could take a very long time to locate an issue. Time spent locating a fault implies economic losses for the company and as a result, the organization may suffer fatal consequences like shutting down operations.
Deploying IOT technologies requires an assortment of different systems that are accurately monitored, tested with high precision before implementation as they provide a large stream of data for analysis and evaluation. Decision making is eased in such an efficient working environment. The system may be designed such that it maintains logs that are remotely monitored. The data collected is periodically transmitted to a cloud platform that hold data for different assets being monitored. The cloud platform is an emerging trend in IT that has attracted large organization that work on full time basis and are not limited by time zones. With cloud based solutions, one can access data from any geographical location, using any digital media as long as they have access to the internet (Fluenta, 2016). Some platforms require a user to have login credentials to access data but others have free access especially if the information stored in a particular segment is not private or confidential. Many industries may implement the IOT communication systems and data storage locations but it is inevitable to eliminate human intervention. The communication system enables information to be stored in the cloud from different remote plants or assets in an industry. The data needs to be analyzed and evaluated so as to make sense. This technique is known as data mining and evaluation. The process produces information that can be used in decision making. The IOT applications are designed to accommodate fail safes that escalate issues with the system to human users for maintenance and ensure there is no point in time where assets are not monitored.
The benefits of implementing IOT applications and communication systems are: -
- Reduction of costs
- Improves the capability of system operations
- It reduces risks that are exposed to humans are the extraction and production plants
- It enables the producers to harness the information obtained and put it to work
- It drives to achieve better decision-making as it exposes inefficiencies and sparks collaboration.
Figure 1 Refinery & Petrochemical: IOM Solution Schneider Electric (Barghouth, 2015)
The best practices towards the IOT integration, especially in the industrial field, requires a translational change to supplement the legacy investments. This is done while delivering important transformation in business processes and results over time. The future of IOT focusses on the mobile applications in IOT. Some of the steps involved in IOT implementation are: -
- Start small with pilot projects and stay focused
- Evaluate the return on investment (ROI) before increasing the project scope
- Perform early strides with energy efficiency and asset management projects
- Move to comprehensive asset coverage within a dynamic network
- Close in the loop with supply and consumer chains by involving them and their profound activities with the industry within the IOT systems and applications.
A number of models have been developed to implement the IOT systems in the currently running legacy systems. The five-stage maturity model incorporates measures and best practice necessary to achieve effective change in both technologies and organizational culture of an industry. Of key concern in this dissertation is the Microsoft Azure which works well as an OT/IT knowledge bridge for industrial operators. The model is implemented using the following stages,
One common case study used to show the use of IOT and cloud based systems in the oil and gas industry is the Hillcorp Energy Company. The company operates oil extraction platforms in the rugged Kenai Peninsula. The extraction site is located of Alaska, USA. The legacy system has had pump controls done using the medium-voltage drives that are remotely managed by virtual support Engineers from an outsourced company. They have implemented a real time monitoring for speeds control and troubleshooting based on the data obtained from the drives and stored in the Rockwell Automation global support center (Allen, 2010). The information is transmitted to the cloud via a wireless connection to the cloud system, application, or database. Storing data in the cloud system ensures that the data is analyzed appropriately and in real time. The analysts can develop algorithms and logic from historical data which is useful in risk management planning and scheduling maintenance programs. Such kind of information ensures less failure and more availability.
Corrosion sensors are devices that show the response that can be recorded once corrosion is experienced in an equipment. Corrosion sensors can be either embedded in the object to be monitored or placed in the environment to be monitored. Ease of handling and corrosion monitoring of inaccessible objects provided by the corrosion sensors is an important advantage of a corrosion sensor. Moreover, low cost, rapidness, reproducibility and sensitivity are some other important disadvantages of corrosion sensors. Considering these, scientists moved towards the production of corrosion sensors, which can be used as systematic corrosion monitoring tools. Corrosion sensors are now used in many instances, where corrosion is a serious concern for the quality or the strength of objects, such as aircrafts, oil refineries, bridges and some buildings made up of concrete. Use of traditional corrosion sensors are still applied, even though there are modern sensing techniques. The simplest traditional corrosion monitoring technique is the use of sacrificial anodes placed at different depths. This is commonly used for corrosion monitoring of reinforced concrete structures, where anodes are externally connected to a suitable cathode and the currents generated are monitored. Ion meters or ion sensitive electrodes placed in the surrounding area of a metallic object is another type of simple and conventional corrosion monitoring technique. Oxygen transport technique which involves the determination of the rate of oxygen transfer on the object is another important sensing technique. Humidity sensors are a different type of traditional sensor which measures the humidity of an
environment in which a metal is corroded. In most cases, these traditional corrosion sensors are used to detect corrosion of metal bars in concrete structures (Broomfield, 2002). With the need of advanced corrosion sensors, more sophisticated methods have been developed which result in modern corrosion sensors. In every year, a number of corrosion sensors are introduced into the market by researchers. These include novel magnetic corrosion sensing methods and fiber optics based sensing methods, which are more efficient than conventional corrosion sensors (Gupta and Verma, 2009). Superconducting Quantum Interface Devices (SQUIDs), hall sensors and magneto-resistive sensors are examples of magnetic corrosion sensing devices.
Most modern corrosion sensing techniques are occupied to monitor corrosion of aircrafts, marine transportation, oil refineries and mineral oil power plants. As the above-mentioned objects are exposed to highly corrosive environments, monitoring of corrosion is a major concern. Corrosion resulted on the wings and the body of aircrafts is more rapid as the aircrafts are subjected to more corrosive medium in the atmosphere (Wilson et al., 2008). Loss of strength of the body of aircrafts results in aging. Therefore, aircrafts may have to be kept out of service even before their expected life time is reached, if corrosion has taken place. Further, many sulphur and chlorine containing compounds are generated among the combustion products of coal and mineral oils, causing oil refineries to undergo severe damages due to corrosion. The damage could be severe that the breakdown of the structure of oil wells is possible. Wireless corrosion sensors have also been developed to monitor corrosion in such situations, especially at places which are not easily accessible.
Remote asset management sensors using IOT
The industry has embraced some smart production processes which put the devices and machines in a position to control and regulate themselves. This is made possible by applying the concept of IOT where the devices are connected to communicate across the internet. The whole idea of implementing IOT applications and cloud based systems eliminates the use of wired communication and implements wireless communication. The wireless communication has a number of merits so as to qualify as the best mode of communication: -
- Reduced costs
- Improved flexibility
- System is easily scalable
- Can accommodate new applications
According to a research conducted by Dag Sjong, it was concluded that there was a possibility to obtain about 10 percent reduced construction costs by utilizing wireless instrumentation in new plants and facilities (Sjong, 2007). Wireless instruments utilized in this kind of communication are mobile devices and most are hand-held devices. New devices can be added to a system running on wireless communication as opposed to the cabled system. The wireless technology greatly reduces the CAPEX associated with instrumentation. The monitoring of the condition and performance of the assets increases the lifetime and maintenance interval. The wireless technology brings about the low cost solutions that enable monitoring of less critical equipment. The mobility of a wireless installation allows for installation in difficult to reach areas. Rotating equipment are difficult to monitor using wired systems hence wireless or radio transmitters are used more efficiently. Some of the key oil and gas wireless technologies implemented are: -
- Wireless sensors that monitor inline process measurements and embrace smart instrumentation
- Wireless Local Area Network to relay the data obtained from the sensors.
- RFID is a crucial wireless device used to track the assets remotely. It could be done by asset tracking or personnel tracking.
- Wi-max is utilized when the relay station or for cloud based systems when the plant or industry wireless devices wish to transmit the data over long range communication and inter platform communication.
One of the wireless remote asset monitoring and control system implemented in the oil and gas industry is the SIGNALFIRE wireless telemetry. The signalfire toolkit is free and has an easy to use PC configuration and diagnostics software. It supports wireless configuration of remote devices. It is described as a robust, short-range mesh network designed toolkit. Its purpose is to provide asset managers access to valuable process data. It is easy to install and sensor diagnostics, the wireless telemetry system can interfere with many sensor types such as flow, level, pressure, and temperature, in controlling devices such as pumps, valves, heaters, fans, and lighting. The remote sensing system is deployed in many fields such as oil and gas fields, irrigation systems, and water treatment areas. The architecture for the signalfire remote sensing system integrates the different sensors in the oil and gas fields to send data to a gateway. The gateway forwards the information to a personal Computer or a programmable logic circuit or any other control systems. The wireless nodes are auto installed into the network configuration. A user can tell if there is a fault on a section of the oil and gas field or the pipeline transportation using offline nodes. A node goes offline to indicate a fault in the device and it alerts the system controller immediately. The nodes, or separate wireless devices in the oil fields transmit diagnostic data to the gateway for upload in the cloud based system.
The architecture is as shown below,
Figure 2 SignalFire remote sensing system (IOT system implementation)
The signalfire wireless sensor nodes perform the following functions when implemented in the oil and gas extraction, processing, transportation, and storage areas: -
- Midstream or pipeline networks
- In the refinery plants
- Temperature monitoring and remote well shutdown
- Tubing, casing, and line pressure monitoring
- Valve positioning monitoring and actuation
- Pump and gas (vented, flared, or biogas) performance monitoring
- Tank level and plunger lift monitoring and control
General electric provides application solutions for the corrosion monitoring in oil and gas industry. The company provides high quality services and applications to ensure high performance during monitoring of corrosion and other aspects such as inspecting welds in the oil and gas fields. It provides solutions for remote visual inspection for the turbine blade viewing in the plants and water piping systems. It uses some robotic crawlers and very high resolution video cameras. The organization provides some specially designed ultrasonic array tests done per phase. The technology is implemented in the reactor vessel and in the piping systems. A number of technologies have been developed to perform corrosion monitoring. These technologies can be implemented in the refineries, extraction plants, and pipelines. In the recent times, more than one technology is being integrated for a complete monitoring strategy.
Monitoring and cloud data transfer – Microsoft Azure
The corrosion monitoring is done using the signalfire wireless sensor which senses corrosion at a short range distance. This means that several nodes are placed over a given spatial distance to avoid colliding with each other and to provide information for a given section of the pipeline. The sensor used in the signalfire sensor system is the Sentinel. It provides power and a wireless link to an industry standard sensor. It has intrinsically safe modules for hazardous areas. It can be solar powered to solve the power issue and cut down on costs. It covers up to half a mile range hence very effective for use. It is easy to install and maintain. The sentinel has solar or battery module for powering up.
The industry suffers significantly and adversely from the effects of corrosion and material degradation. The impact is felt in economic losses as there are increased maintenance costs. It also poses an integrity and safety risk for the plants, refineries, and transportation infrastructure systems. This dissertation addresses the many ways in which the corrosion is addressed using corrosion inhibitors. The mitigation strategies are such as painting, coating, cladding, cathodic protection, and the use of chemicals. The impact of implementing a corrosion protective scheme needs to be verified for feasibility. The health and safety regulations require an industry to use very limited amounts of chemicals for the environmental conservation and to manage the economies of scale. When corrosion is not controlled, there are increased chances of accidents and unplanned stops that may have a serious impact on the economy and environment as well as being a risk for personnel and the surroundings.
Some of the corrosion monitoring technologies and innovations discovered in the IOT age and cloud computing arena have some major benefits and minor caveats. There are intrusive probes used in refineries as well as in upstream oil and gas production. These probes perform electrical resistance and linear polarization resistance calculations. The weight loss coupons are useful for the intrusive corrosion monitoring. The working principle of this coupon implements steel samples prior to transmission of any liquid content or storage of the liquid content in a refinery for a given period. The steel samples are later weighed and cleaned. The weight difference implies the corrosion rate, the deposits, and the tendency to localize attacks on the exposed coupon. The results obtained are calculated and reported. This practice is carried out periodically. The ER probes are based on measuring discrepancies on the resistance obtained from the intrusive probes measurement elements. Corrosion on the metal element reduces the thickness of the steel samples and increases the resistance. Unfortunately, these technologies are local and can only measure intrusive corrosion on the equipment only.
Figure 3 refinery style ER probe with full bore valve and pacting gland
Further advances in technology have shown that there are intrusive corrosion monitors that implement the wireless hart corrosion transmitters. Many industries are now using ultrasonic sensors for high temperature applications. These sensors calculate the pipe wall thickness initially when installed. They have the ability to correctly detect changes in wall thickness on a pipe from which corrosion rates are measured. The sensor accuracy has the precision in the range of 10-100 micrometers. Corrosion on the steel metal for the equipment and the pipelines does not occur uniformly. To take care of the non-uniform corrosion, an array of ultrasonic sensors is utilized. The ultrasonic sensor is implemented with the low installation cost per location. For high temperature applications, the high temperature ultrasonic sensors are in a position to allow for the application of permanent wall thickness monitoring at a high number of selected locations around a plant. These sensors are also compatible with the wireless Hart communication. It implies that the sensor can obtain the data from a given point and send data to a cloud or a remote location instead of the plant systems locally. The transmitter below is used to send the data collected periodically.
Figure 4 Transmitter for installed Intrusive corrosion probes (Emerson, 2015)
The field signature measurements are those measurements taken on the basis of the changes encountered in the wall thickness between a sensing pin installed on a pipe or equipment. An electric current is fed over the monitored area and the measuring changes in voltage drop between pairs of sensing pins caused by changes in pipe wall thickness. The resolution of the measurement tool is the resolution that is set at 0.1% of the pipe wall thickness for uniform corrosion. Unfortunately, this measurement scheme sensor does not allow for wireless communication of the wireless Hart solutions. It only collects data and stores the data locally within the plant or the field computer network systems. The corrosion monitoring exercise is done continuously. The activity increases the amount of data and adds value with respect to correlating corrosion monitoring data with process changes and making the trending of data more accurate. The monitoring continues offline where the data is downloaded at defined intervals. The offline monitoring is much more cost effective than monitoring on site. It is very important to provide quality and valuable data on the corrosion monitoring. In the earlier days, the corrosion monitoring process was carried out using corrosion coupons. In this process, the probes were deployed and queried off line by a portable meter on a weekly, fortnightly, or monthly basis. The use of corrosion coupons demonstrates the simplicity in data acquisition. There are low installation costs in the implementation of intrusive probes. While the installation costs are low, the labor costs tend to be on the rise. The use of the corrosion coupons requires human intervention on the field to access and retrieve the data as the data is not transmitted to a remote server or to the cloud system.
The industry is moving forward and embracing the on-line corrosion monitoring. It allows for frequent data for optimized trending and process correlation, minimized labor for data collection, and real time information to the user. The on-line monitoring has a few caveats in terms of economies. The installation tends to be a little bit more expensive especially if the plant was pre-existing. To overcome this limitation and avoid wired communication, the industries are embracing the wireless communication. Wireless communication guarantees good transmission of the data at an affordable cost. The wireless Hart technology is the most commonly used wireless communication technique. It allows for different monitoring functions to be associated within a single wireless network. The communication is a mesh network system that incorporates different applications and transmits signals as routed at the gateway terminal. The routes are provided by the pre-installed routers and the route is established out of the network through the gateway. As such a user can combine different monitoring techniques in one wireless network system and as a result only uses one gateway to transmit the data. The infrastructure is easy to deploy and it is more mobile. The data in such an interlinked system is sent to the general data management system using a particular software installed in the network.
Figure 5 corrosion transmitters in a wireless hart network with other applications, via the same gateway
The different applications installed for the data acquisition, management, and monitoring can equally transmit their output via the wireless network with little configuration done on the network (Wold, 2011).
The intrusive probes and FSM technology are managed within the Emerson’s fieldwatch software within the Roxar CorrLog wireless system so as to make the correlation and reporting of data more efficient. The Jamnagar refinery is owned by Reliance Industries in Gujarat, India and has an aggregate refining capacity of 1.24 million barrels of oil per day (Wold, 2010). The refinery, the commissioned in July 1999, is one of the largest refineries in the world, and one of the most extensive users of FSM corrosion monitoring. The sensors were mostly installed in process streams in crude and vacuum unit furnace outlet lines, as well as other high temperature sections where the temperature is in the range of 2000 C to 4000C. since 2008, the monitoring at the actual site has continued, and typical data from the online system is presented as shown in the following performance, reliability, resolution and accuracy of the system (Kane & Cayard, 2002). Spike filters are applied and the plot shows general metal loss for all pairs from the beginning of October 2010 to January 2011. The total metal loss in the period is 0.32 mm.
Corrosion is a great challenge in the oil and gas industry but the use of IOT applications and the cloud based system for maintenance and control solves the issues presented. Corrosion poses a great risk for the environment and has a negative impact on the health and safety of the people. Each plant or industry must adopt a corrosion monitoring and maintenance plan to meet the specific needs. A range of intrusive and non-intrusive method exists and have their own benefits and limitations (Board, 2013). A combination of methods gives the best overall monitoring program for a refinery.
The implementation of the wireless communication systems in the plants and fields ensures that data acquisition and transmission from remote locations of plants can be transmitted to a remote server or a cloud location for access of data and analysis.
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