|Fig.1: Low Flow Cut-off|
One of the most common applications for differential pressure transmitters is flow measurement. A differential pressure transmitter can be placed across many types of primary flow elements like orifice plates, pitot or venturi tubes to measure flow. Primary flow elements create a pressure drop (square root proportional to flow).
Flow proportional output signals from a differential pressure transmitter are possible through integral square root extraction. The square root function of differential pressure has extremely high gain at low flow rates leading to large output changes representing low changes in flow rate at the bottom end of the measurement range. Output signals can become erratic at low flow rates due to high gain. Host control systems can experience difficulty controlling flow rate based on a highly fluctuating input signal from the square root extracted differential pressure. DPharp differential pressure transmitters have some unique signal conditioning features to eliminate instability at low flow rates.
Flow rates above 20% of maximum flow produce a large square root extracted differential pressure signal for a given change in flow rate. Flow rates around 5% of maximum flow produce a small square root extracted differential pressure signal for a given change in flow rate (See Fig.1). High gain in the low flow rate operating area amplifies any inherent noise or changes in flow rate leading to pressure transmitter output instability.
DPharp has a software capability to stabilize output signals at the low end of a flow measurement range minimizing erratic output signals. An integral low cut mode features a user programmable transmitter output and set point to change the output to a linearto- pressure (Linear) or zero (Zero) status. The flow rate set point at which an output transition occurs is programmable from 0 to 20% of full scale flow. Fig.2 shows Linear and Zero output modes set at 5 % low cut mode.
Hysteresis is incorporated into the low cut mode such that when the actual flow rate is equal to the low cut set point that output oscillation will not occur. Hysteresis is fixed at a nominal 1% of full scale flow. Fig.3 details how the hysteresis affects the pressure transmitter output.
Main Features of DPharp
EJA110A Digital Solution
- Best-in-class performance
- ±0.03% Overpressure calibration protection
- ±0.1% per 5 years long term stability
- 100:1 turndown
- ±0.065% accuracy
EJX110A Premium Value
- ±0.1% per 10 years long term stability
- 200:1 turndown
- Best-in-class high accuracy, 0.04%
- Multi-sensing output
- Multi-variable transmitter as EJX family line-up
- Safety as standard (IEC 61508)
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.
Industrial water is used in all industrial plants such as power generation stations, refineries and petrochemical plants. Yokogawa’s single control platform handles all water and wastewater control processing integrated with the main process.
Iron & Steel
In the iron and steel industry, it is crucial to improve the quality of not only products but also manufacturing and operation technologies, as well as to address environmental and energy-efficiency issues. Yokogawa helps customers to create the ideal plant and evolves with them for mutual growth.
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.
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.
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.
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.
The right pipeline control and instrumentation can make a huge difference in terms of performance and profitability. Yokogawa has dedicated technology that can optimize the performance of all elements of a pipeline solution, including compressors, pumps, valves, and intermediate storage and distribution facilities.
In the mid 1970s, Yokogawa entered the power business with the release of the EBS Electric Control System. Since then, Yokogawa has steadfastly continued with the development of our technologies and capabilities for providing the best services and solutions to our customers worldwide.
Yokogawa has operated the global power solutions network to play a more active role in the dynamic global power market. This has allowed closer teamwork within Yokogawa, bringing together our global resources and industry know-how. Yokogawa's power industry experts work together to bring each customer the solution that best suits their sophisticated requirements.
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.
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.
Thermal power using coal, oil or gas as fuel accounts for the majority of electric generation throughout the world.
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.
Wastewater treatment plants involve many pieces of equipment such as motors, pumps and blowers, which makes it important to reduce their electricity consumption and save running costs. Yokogawa provides optimum control solutions with digital technologies to improve energy efficiency.
Water & Wastewater
Water resources are finite, and therefore contributing to a sustainable water cycle is one of the Sustainable Development Goals (SDGs). Yokogawa has been providing advanced digital control solutions for the stable supply of clean and safe water, wastewater treatment for protecting the water environment, water loss management and optimization of plant operation for reducing CO2 emissions and running costs. With our leading-edge technologies, dependable products and extensive expertise and experience of diverse water projects around the world, we work with you to provide sustainable water solutions that boost your business and add value throughout the plant lifecycle.
Yokogawa supports a wide range of water control applications in both the municipal and industrial water markets.
Yokogawa provides optimum solutions to improve the reliable operation of water treatment plants. These solutions include sophisticated technologies, unsurpassed product quality, and extensive application know-how throughout the lifecycle.
Contact a Yokogawa Expert to learn how we can help you solve your challenges.