Introduction
Impulse Line Blocking Diagnosis in DP Transmitters
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| Figure 1 Connected to impulse lines |
Differential pressure (DP) flowmeters composed of an orifice plate, a DP transmitter, and other components are widely used in many applications because they are reliable and require no wet calibration. The simple design of orifice plates and modern DP transmitters make them extremely reliable. However, the impulse lines which transmit process pressure to the DP transmitter are vulnerable to blockages caused by fluid condensation, freezing, or corrosion. Impulse line blocking is a problem that must be addressed to ensure efficient operation and maintenance.
Yokogawa's EJX series DP transmitter is equipped with a silicon resonant sensor that can rapidly detect both static pressure and differential pressure. These features enable the development of a diagnostic technique which detects fluctuations in static and differential pressures. By using a digital communications network such as fieldbus, operators can determine whether an impulse line at a specific installation site has been blocked. Such information can significantly reduce maintenance workload and cost.
Expected Benefits
- Informs operators/maintenance engineers that a blockage is forming in an impulse line before the process is disrupted.
- Predicts when the impulse line will be blocked and suggests a corrective action, based on blockage thresholds.
- Blockage thresholds are determined based on blocking substance, flowrate variation, and the time required for taking corrective action.
Impulse-line-blocking Diagnostic Technique
(1) Fluctuation of differential, static pressures
Table 1 Fluctuating component values in impulse lines
Fluctuating components of differential, static pressures generally decrease when an impulse line is blocked.
Fluctuating components are calculated as the square summation of the difference of differential and static pressures that are sampled at very short time intervals. The amplitudes of fluctuating components are derived from the root of the square summation. Since these components are affected by flowrate changes, they are provided as fluctuation components through flowrate compensation.
Table1 shows the value of the fluctuating components when blocking occurs on the Hi-side, Lo-side, and both sides. The values for when no blocking occurs are also shown. When both sides of impulse lines are blocked, all fluctuating components decrease. When one side of an impulse line is blocked, the corresponding fluctuating component decreases. In this case the fluctuating component of differential pressure is larger than when no blockage occurs.
(2) Blocking diagnosis using water flow test rig
Figure 2 Blocking factor F with H and L side blocking
Blocking factor F is determined as the correlation function between the amplitudes of fluctuating components. It approaches +1 for high side blocking and -1 for low side blocking. Figure2 shows the Blocking factor F for each blocking type.
Conclusion
Operators must receive diagnostic information before a line block leads to a malfunction. Yokogawa provides predictive diagnostics based on trend analysis of the blocking factor, which improves maintenance efficiency and reduces maintenance costs.
Note:
This diagnostic function is currently available for low viscous liquids only.
Industries
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Bulk & Petrochemical
Whether you produce petrochemicals, inorganics or intermediates, chemical companies are under cost and margin pressures to deliver products in a timely and efficient manner while maintaining safe and compliant operations. Additionally, chemical companies need to adjust to fluctuating feedstock and energy prices and to provide the most profitable product mix to the market.
Yokogawa has been serving the automation needs of the bulk chemical market globally and is the recognized leader in this market. With products, solutions, and industry expertise, Yokogawa understands your market and production needs and will work with you to provide a reliable, and cost effective solution through the lifecycle of your plant.
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Chemical
Chemical plants rely on continuous and batch production processes, each posing different requirements for a control system. A continuous process calls for a robust and stable control system that will not fail and cause the shutdown of a production line, whereas the emphasis with a batch process is on having a control system that allows great flexibility in making adjustments to formulas, procedures, and the like. Both kinds of systems need to be managed in available quality history of product, and to be able to execute non-routine operations. With its extensive product portfolio, experienced systems engineers, and global sales and service network, Yokogawa has a solution for every plant process.
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Offshore (FPSO FLNG & FSRU)
Offshore exploration and production requires maximum uptime under harsh conditions. Manned and unmanned facilities need reliable integrated control and safety systems (ICSS) with advanced remote monitoring capabilities. Yokogawa has state-of-the-art technology and extensive experience in executing offshore projects of all sizes and automation levels of complexity.
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Oil & Gas
Yokogawa has a wealth of experience in every part of the oil and gas business, from offshore and onshore facilities to pipelines, terminals, and deepwater operations. We provide solutions that enhance safety, ensure accurate and reliable operation, and increase plant efficiency.
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Oil & Gas Downstream
The oil & gas downstream industry has been facing an increasing number of challenges in recent years. These include the changing characteristics of the feedstock to be processed, aging of process facilities and equipment, rising cost of energy, lack of skilled plant operators who can run a refinery safely and efficiently, and the ever-changing requirements from both the market and the customer.
Over the years, Yokogawa has partnered with many downstream companies to provide industrial solutions focused on solving these challenges and problems. Yokogawa's VigilantPlant solutions have helped plant owners to achieve maximum profitability and sustainable safety within their plants.
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Petrochemical
Petrochemical companies’ needs are extremely diverse. To come out ahead in today’s highly competitive marketplace, producers are striving to improve quality and productivity. Yokogawa provides tailor-made solutions for these needs based on its long and wide-ranging experience in this field.
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Refining
In the ever changing marketplace, refineries are seen not only as crude processing units but also as profit centers. At the same time, there is a keen awareness of the need for safety at such facilities. A total production solution that encompasses planning, scheduling, management, and control is required to achieve long-term goals for profitability, efficiency, and environmental protection. With years of expertise in the automation field, Yokogawa can bring you affordable total solutions for improved operability and a cleaner world.
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Specialty & Fine Chemical
Yokogawa has long served customers in the specialty and fine chemicals market. With a market leading batch solution that offers the best in class reliability and flexibility as well as industry experts who understand the complex requirements in designing a batch solution, you can be assured that in your partnership with Yokogawa you will have a system that will enable you to produce products that meet your customers’ needs in the future while maintaining safety and regulatory compliance.
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Upstream
The upstream industry includes offshore and onshore activities including wellhead automation, fractionation, completion, and separation to recover and prepare underground or underwater crude oil and natural gas.
As petroleum is brought to the surface, it must be separated prior to transport. Primary and secondary separation stages commonly distribute gas flow, water flow, and oil flow in three phase separation. Gas movement requires pipeline and can include a fractionation process in the upstream stage prior to movement. Liquids can be placed into a tanks or pipelines and sent for processing, requiring accurate level measurements.
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