Process Control Optimization - Basic Tips

There's always a myriad of variables inherent to the process which Instrumentation and Control Engineers have to tackle to optimize their plants. Noise is a troublesome part of the process that system engineers must deal with. There are more effective devices to pick up pump-bearing issues than the discharge pressure sensor. Vibration sensors with more accurate frequency bands can detect unbalanced loads caused by damage in bearings or other rotating parts. Usually, these devices are installed directly on and pick up directly from the bearing. Moreover, these devices also represent an alternate method of measuring fluid density. The denser the fluid is, the lower the vibration amplitude detected by the sensor. They usually make use of acceleration devices in this process. For frequencies up to about 1kHz, micromachined accelerometers are the most suitable. Higher frequencies (up to 100kHz) demand piezoelectric devices. The damping effect is minimal due to their reduced mass.

Figura 1 - Vibration Sensor (Source: https://dc-components.com/product/hs-4200100208-vibration-sensor)

Ultrasonic thickness gauges are adequate for computing the remaining pipe wall thickness than extracting it from pH and other process data. With proper calibration, measuring accuracy ranges from +/- 0.001" or 0.01mm. In some cases, accuracy can approach 0.0001" or 0.001mm.

Figura 2 - Ultrasonic Thckness Gauge - Source: https://www.phase2plus.com/product/ultrasonicthicknessgauges-utg-2900/

Steam trap data is more useful when we add an acoustic sensor and gather information through the analysis of ultrasound waves. The market has diverse sizes available to attend to almost any process need. There are two acoustic sensor types: fixed, consisting of a single piece. Its signal is transmitted through the air or a liquid. And the contactless acoustic sensors. This type of sensor consists of a fixed part (stator) and a moving part (rotor). Rotor and the stator are independent from each other.

Figura 3 - Acoustic Sensor (Source: SIEMENS)

Pressure sensors on the engine can determine whether lube oil pressure is descending more efficiently and precisely. They are also valuable for monitoring pressure data from pressure relief valves. Their positioning dictates the effectiveness of sensors (the nearer they locate to the machining area, the better) and their material composition. For industrial applications, the micromachined silicon diaphragm is the most commonly used to generate electric signals required for communication. Silicon is a semiconductor that integrates the strain gauge and the amplifier on the diaphragm structure's surface. Silicon devices cover a wide operational temperature range (-50ºC to + 150ºC), allowing operation with low leakage and tight tolerances for mass production. A single silicon chip can integrate a myriad of subsystems, enabling a vast amount of devices to incorporate within a single package. Through the process, plugging filters are constantly confused with inaccurate valve settings. DP sensors installed across the filter usually rectify this issue. Temperature sensors are pivotal in optimizing an engine's lifecycle and mitigating downtime.

As the differential pressure increases, the diaphragm expands and deflects inside its capsule. Its deflection depends on its dimensions, elasticity, and thickness. Stainless steel, phosphorated bronze, and iron-nickel alloys are the most common raw materials. Most instruments based on these materials are commercially available with pressure configurations up to 50 psi (350kPA).

Stainless steel, phosphor bronze as well as iron-nickel alloys are used. These instruments usually endure pressure levels up to 50 psi (350 kPa). The sensitivity and the mechanical movement increase when capsules are joined together, as shown in the below pic. These capsules are placed opposite from one another and permit differential pressure measurement. The measuring system uses a closed-loop technique to convert the movement of the arm (pressure) into an electrical signal and maintains it in its neutral position in a force balance system. Pressure changes move the arm, and a linear variable differential transformer (LVDT) or another type of position sensor recognizes this movement. The signal is amplified and drives an electromagnet to pull the arm back to its neutral position. The applied pressure dictates the current needed to drive the electromagnet, and the output signal amplitude is proportional to the electromagnet's current.

Figura 4 - Smart Sensor arquitecture for fluid processing

The smart sensor integrates a sensor with an ADC, a PID processor, a DAC for actuator control, and so forth. Such a setup is shown below for the mixture of two liquids in a fixed ratio. Differential pressure sensors monitor the pressure of both liquids. This is also useful to correct the flow rates for density changes and any variations in the sensitivity of the DP cells. The electronics in the smart sensor integrates the sensor, amplify and condition the signal, and apply proportional, integral, and derivative action (PID). A multiplexer (MUX) selects the desired analog signal from the sensor sequence. Then, an ADC converts it into a digital format for the internal processor. After the processor evaluates the signal, control signals are generated, and the DACs convert these signals to the actuators. Communication between the central control computer and the distributed devices is via a common serial bus. The serial bus, or field bus, is a single twisted pair of leads used to send the set points to the peripheral units and to monitor the status of the peripheral units. The processor in the smart sensor is then able to sensor to receive updated information on factors such as set points, gain, operating mode, and so forth; and to send status and diagnostic information back to the central computer. Smart sensors are available for all of the control functions required in process control, such as flow, temperature, level, pressure, and humidity control. Distributed control has many advantages, as already noted.

Figure 5 - Differential capsule pressure sensor with closed-loop electronic control

Valve position sensors support process operators by ensuring that all valves line up precisely when the pump starts instead of leading them to rely merely on tank levels. The indirect method of gauging the coolant level employing the process pressure measurement is counterproductive. Adding a sensor level directly on the piece radiator establishes a feed-forward process control that better determines whether the coolant level goes down rather than just monitoring the system pressure. Flow readings represent an outdated control strategy for motor windings temperatures. The overheating issue caused by insulation breakdown constantly burdens engine integrity.

Figura 6 - Valve positioning sensors ( Source: ROTORK)

Undeniably, these implementations depend on which enterprise strategy best fits its respective business model. The objectives might include profit maximization, energy consumption minimization, market demands, and quality. These process control optimizers offer a more precise and absolute representation of process variables to maximize process performance 

 Bibliography:

-https://www.directindustry.com/prod/siemens-process-instrumentation/product-18343-934715.html

- performancehttps://www.marposs.com/eng/product/acoustic-sensors

- https://dc-components.com/product/hs-4200100208-vibration-sensor/

-https://www.phase2plus.com/product/ultrasonicthicknessgauges-utg-2900/