Recently, our Service Crew was called to address a critical issue at a Maryland University involving an improper drum pressure reading. The investigation led to the discovery of a damaged transducer, which was unprotected due to the absence of a siphon pigtail. This small yet crucial component plays a significant role in maintaining the reliability and safety of […]
System Reliability at a Maryland University
Our Service Crew was recently called to diagnose an issue with an improper drum pressure reading at a Maryland University. What we found highlighted the importance of a small but crucial component in pressure control systems: the siphon pigtail. The Problem Upon inspection, we discovered that the transducer, responsible for providing accurate pressure readings, had been damaged. The […]
Fuel/Air Cross-Limiting
What is the Application? Steam supply and heating loads in a boiler plant vary throughout the course of the boiler firing cycle. In response to this, the boiler firing rate output % is continuously adjusting to maintain steam or temperature setpoint. This means that the boiler controller’s outputs (typically a fuel valve positioner, air damper positioner, and variable […]
Drum Level Control Essentials
What is the Application? As boilers convert water into steam to supply the plant’s load demand, more water must be supplied to the boiler to maintain the drum level at setpoint. In a modulating PID system, Boiler feedwater flow is controlled by the drum level controller by modulating a feedwater control valve which can be opened to give […]
PID Loops in Boiler Control Systems Part 4: Practical Tuning Techniques
Now that the PID components and type structures have been examined, Let’s get into the process of fine-tuning a PID loop. It is important to remember that in a real-world setting there are many variables that must be accounted for such as the plant process load variations, transmitter calibration and range scaling, control valve stroke, fuel supply pressures, […]
PID Loops in Boiler Control Systems Part 3: Boiler Control Applications and Common PID Loops
As stated in Part 1, PID loops are a central component of a modern boiler control system. In this section, we will examine some of the more common applications of PID loops in boiler control systems. We will look at four types of PID loops: Reverse Acting, Direct Acting, Cascading, and Override. Reverse Acting PIDs The most common […]
PID Loops in Boiler Control Systems Part 2: Expanded Definitions of Proportional and Integral Terms
Now that the basic PID terms have been examined, we can now look deeper into the PID calculations and some less common variations that can be used. Defining KP In the basic definition of the Proportional Term in Part 1, the Proportional Term was calculated by finding the Error (either SP-PV or PV-SP) and multiplying it by a […]
PID Loops in Boiler Control Systems Part 1: The Anatomy of a PID
PID loops are a central component of modulating boiler control systems with applications ranging from basic steam header pressure control to cascading 3-element drum level control. A modern full-metering combustion controller with draft, FGR, VSD, and O2 trim can have as many as 10 PID loops running at once, with some interacting with each other. With this in […]
Choosing Between SIL2 and SIL3: Striking the Right Balance of Safety and Cost
Safety Integrity Levels (SIL) are critical in ensuring the reliability and safety of safety-related systems in various industries, including process automation, transportation, and manufacturing. SIL2 and SIL3 represent two different levels of functional safety, each with their own advantages and trade-offs. When designing safety-critical systems, engineers often face the dilemma of choosing between these two levels. This article […]
Heat Exchangers In Boiler Applications
Howard Wells, Danbury, CT Various heat exchangers are used to capture waste heat contained in boiler exhaust that would otherwise be lost to the atmosphere. These devices are designed to capture the maximum amount of heat possible, resulting in improved fuel efficiency and reduced operational costs. There are three main types of heat exchangers used in boiler applications: […]