Jared Thompson

Furnace & Heat Stack Dampers

Downstream /

Furnace and Heater Stack Dampers Background Furnaces help refineries and petrochemical plants break down and convert hydrocarbon fluids into fuels or chemicals such as gasoline, diesel, ethylene and propylene. As furnaces sometimes account for more than 50% of total plant energy consumption, small improvements in efficiency equate to large financial returns. Refineries and petrochemical plants tend to overlook draft control when making process improvements.  Optimizing the draft in a process heater is easy as there are many types of processes and instruments to choose from. The challenge is safely elevating process fluid temperature to a target level while maximizing thermal efficiency, throughput and reducing O2, CO and NOx emissions. Fast-acting, repeatable and accurate damper positioning enables fine-tuning of modern damper control systems.  Problem Despite the high-level automatic control of instruments running complex loops in refineries and petrochemical plants, many dampers are controlled manually via cable and winch. This type of damper arrangement complicates accurate positioning, leading to poor furnace draft control. More importantly, manual operation of dampers creates a potential safety hazard to personnel – especially during emergency situations.  In an inexpensive attempt to automate a damper, a lot of plants select pneumatically-operated drives. Prone to hysteresis, static friction (stiction), overshoot and instability, pneumatic actuators face increased difficulty making small and controlled position changes. This inability to achieve stiff control limits the combustion process efficiency. Solution Upgrading or automating existing dampers with REXA Electraulic™ damper drives provides immediate benefits – enhancing furnace draft control.  Literature Download the full Furnace and Heater Stack Dampers Application Spotlight! Download

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Compressor Anti-Surge

Downstream, Metals Processing /

Compressor Anti-Surge Background Axial and centrifugal compressors are critical pieces of equipment found at the heart of many industrial processes throughout many industries. Implementing the correct high performance compressor control strategy impacts process control and plant profitability. Responsive and stable process control is imperative to improve yield and ensure maximized compressor availability. One of the main applications to ensure maximized availability and throughput is Anti-Surge Control.  What is Compressor Surge? A compressor surge event is a temporary flow reversal through a compressor. This typically causes a rapid downstream decrease in demand, therefore resulting in a rapid increase in compressor discharge pressure. Eliminating these events is essential since they damage the compressor and cause unwanted process downtime at production facilities.  How can the Compressor Anti-Surge Valve help? The Compressor Anti-Surge Valve (ASV) is a critical component in compressor operation, because if optimally controlled, the ASV can eliminate surge through the compressor. Furthermore, this allows for safe operation while enabling the compressor map area to be increased, maximizing compressor efficiency. The ASV requires high-performance capabilities including minimal dead-time, high-frequency response, rapid stroke speed, and minimal overshoot. REXA Actuators can easily exceed the requirements for 500msec full stroke trip, moving the operating point away from the surge line and back into control. Our actuators provide resolution and repeatability to 0.05% and eliminate overshoot, regardless of the step size. Literature Download the full Compressor Anti-Surge Application Spotlight! Download

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Pump Station Pressure Control Systems Explained

Midstream /

Pump Station Pressure Control Pressure control of incoming and discharge flows at the pump stations directly correlates to overall pipeline safety and security. A critical part of the control systems is pressure control in the pipeline. Pressure control serves two essential purposes. The first is to control the discharge pressure of the pump station to achieve the proper flow rate and to attenuate pressure fluctuations in the transmission to downstream pump stations. The pressure control systems, which include valves and actuators, must ensure the pipeline is operating below the system design pressure. The second purpose of the pressure control system is to ensure that the incoming pressure to the pump station is kept above the NPSH (Net Positive Suction Head) required by the pumps in order to prevent cavitation within the pumps and the possibility of damage that could result from the cavitation. Pressure control is interactive from one pump station to another, which means that pressure fluctuations at one station will affect all of the other pump stations along the pipeline. The control system must be able to provide fast response to pressure disturbances during starts, stops, and flow rate changes. It must also provide fast response to set point adjustments at one station in order to achieve the desired flow rate and pressure at another Literature Download the Pump Station Pressure Control Application Spotlight! Download

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Terminal Inlet Pressure Control

Midstream /

Terminal Inlet Pressure Control Background Pressure control is critical when transferring crude oil and petroleum products from the main line to the terminal. Therefore, reducing the variation in delivery pressure will result in uniform flow rates that provide protection from over-pressure conditions in terminal systems. Installing a terminal inlet pressure control valve in the delivery line reduces pressure variation. The inlet pressure control valve is also known as a “holding pressure” or “delivery pressure” control valve. Achieving Poor valve performance could potentially cause unwanted pressure excursions – leading to unscheduled pipeline shutdowns and unit downtime. Problem High pressure differentials are concerning due to the potential cavitation in the flow through the terminal inlet pressure control valve. Cavitation will occur when the flow stream pressure falls below the fluid’s vapor pressure, therefore forming bubbles which will implode once the fluid pressure recovers. These bubble implosions cause severe damage to the valve and, consequently, to the downstream pipeline itself. Solution REXA Electraulic™ Actuators are the solution for fast response to signal command and precise modulation of the terminal inlet pressure control valve. This ensures proper flow control and stable pressure for safe operation. Literature Download the Terminal Inlet Pressure Control Application Spotlight! Download

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Pump Recycle Control

Midstream /

Pump Recycle Control What is Pump Recycle Control? Pump Recycle Control, also known as pump re-circulation flow control, is one of the most common applications found within the Liquid Pipeline industry. Pump Recycle Control keeps pumps operating at a point on their curve. This preventative measure prevents over-pressure of downstream piping and components. The loop directly controls pressure and (by the nature of the system hydraulics) flow rate.  When selecting control valves for this application, it’s important to understand cavitation and consider designs that will limit it. Globe valve designs are generally preferred for pump recycle control due to their higher cavitation coefficient. Response times should be moderately fast.  Explore the significance of Pump Recycle Control, a crucial application in the Liquid Pipeline industry. Learn how it maintains optimal pump operation, prevents over-pressure, and the importance of selecting appropriate control valves to mitigate cavitation effectively. Literature Download to read the full Pump Recycle Control Spotlight! Download

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Distribution Water Pumping

Pump Stations /

Distribution Water Pumping Water Pumping Background Reliable access to drinking water is an overlooked necessity to the modern world. When using pump stations, it is critical to ensure full capacity is always readily available. Standard design practices were created to promote reliable operation, but the technology available has not always been up to the task. Valve actuation on the discharge side of a pump requires careful consideration. Reliability is critical to ensure full water pumping capacity, especially during high demand periods. Equally important is for any discharge valve actuator to provide a guaranteed fail-safe system to protect the pumps in the event of an emergency (when applicable). Why do other actuation technologies come up short in this application? Water often gets pumped across long distances and elevated terrain. Any failure or emergency condition that halts active pumping can result in a flow reversal where gravity forces the flow back down the line towards the pump. This causes the pump to spin backwards. To prevent this, there is typically a check valve on the discharge side of the pump installation. In some cases, a check valve may be combined with an actuator to serve as both the in-line check and control valve package. Commonly used actuator technologies do not represent the most reliable options available and typically require frequent maintenance. A need exists for a more reliable alternative that requires lower cost of ownership. Pneumatic-based systems employ a central compressor system that generates air pressure fed to multiple pneumatic cylinders driving valves. Air is a compressible medium, so it is not a rigid form of actuation. As such, pneumatic actuators are susceptible to “sticking” and “sliding” (also known as deadtime and overshoot), resulting in poor response and control. Hydraulics also present a new set of concerns regarding the oil medium itself. In any hydraulic system, roughly 80% of all failures are attributed to the breakdown of oil. Maintaining oil within these systems is of critical importance. Hydraulic actuators require periodic oil changes, as well as a method of filtering that also requires periodic attention. This task can be quite burdensome in larger pumping stations where massive volumes of oil may be required in these systems. The REXA Solution REXA offers the most reliable actuator solution for a pump discharge valve service. Individual actuators are supplied for each pump discharge valve, eliminating the single point failure hazard posed by centralized systems. REXA delivers smooth and controlled pump discharge valve operation during both normal and emergency conditions. Any speed requirements can be met to maintain a pump curve while also eliminating water hammer / surges that can damage piping infrastructure. REXA is the most energy efficient actuator available, reducing your power costs. With dramatically reduced oil volumes compared to traditional hydraulic systems, REXA eliminates any environmental contamination or insurance related concerns. Literature Download to read the full Water Pumping Application Spotlight! Download

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Hot Blast Temperature Control

Uncategorized /

Hot Blast Temperature Control Steel production is vital to many industries around the world. Some industries include general construction, machinery manufacturing, automotive, marine, and transportation. The world needs large volumes of high-quality steel to sustain the high demand. This is especially true during times of economic growth.The blast furnace is a key component of many integrated steel mills. A chemical reduction process occurs within the blast furnace. Carbon dioxide converts iron oxides into “pig iron,” an elemental iron with carbon and sulfur containing impurities. Pig iron undergoes additional processing to make a variety of commercial steel products. In Indonesia, a tier one steel producer uses REXA actuators in multiple applications, for the blast furnace. One application is positioning the cold blast mixing valve. This valve’s purpose is to blend cold blast air with hot blast main air, so the feed air temperature is constant. Constant air volume and temperature enables the reactions in the blast furnace to occur in a controlled manner. The outcome is a reliable blast furnace production of pig iron. A simplified process diagram is illustrated in Figure 1. Two or three stoves are used to preheat the air to around 1200°C (2190°F). The stoves are cylindrical steel structures lined with insulation and filled with checker brick. This is where the heat is stored and then transferred to the cold blast air. Air blowers feed 200°C (392°F) air to the ovens. The ovens cycle between preheating the air and being in reheat mode. Air entering a preheated oven exits at higher temperatures that dissipate over time until the next heated oven is utilized. The complex sequencing of the three stoves, switching modes, is illustrated in Figure 2. The actuator needs to position the mixing valve, without delay, so the mixed air has a constant temperature.

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