Instructor Perspective: Unit Startup Issues

Summary: In this episode I discuss how to troubleshoot unit startup issues with my guest, Juan Roman. Juan is an Industrial Control instructor and unit startup issues are one of the most frequent topics that he is asked about in his classes. He shares his thoughts on how to analyze the common potential causes.

Topics Covered:

  • Most common issues Juan sees when teaching Industrial Control courses
  • Potential causes for unit startup issues
  • Start permissives and their role in troubleshooting
  • Inlet Guide Vane (IGV) and Lube Oil examples
  • Analyzing alarms to determine if issue is process or connection related
  • How controls training and services can help

Guest Bio: Juan is currently a Technical Lead and Instruction Design Lead for Nexus Controls and has over 30 years of experience working with control systems. His past roles include Lead Technical Support Specialist, Senior Training Manager, Remote Services Engineer, Manufacturing Engineer, and serving in the US navy as a Gas Turbine Technician.

Currently, Juan is a training instructor who teaches various control courses to internal and external customers – both remotely and on-site.

The two most common issues Juan sees when teaching Industrial Control courses

  • Lack of knowledge of the control systems. The customer may be running a specific controller for the majority of the plant. However, there are a variety of vendors, controllers, and experiences installed throughout the plant. As a result, a new hire may not necessarily have the breadth of plant experience and background needed to operate those tools.  
  • Lack of familiarity with the on-site equipment. Some personnel may be familiar with the tools, but they need additional, deeper training. They may know how to operate the controls and have experience performing maintenance at the site. However, they need to understand the documentation that directly demonstrates the procedures and parameters of the equipment being used.

This is why Nexus Controls has developed training around these two gaps. Training focuses on demonstrating the controls and using the documentation to improve personnel knowledge and enable improved plant performance.

Potential causes for unit startup issues

Unit startup is the crucial “first step” to operations.  Often times, however, customers cannot start their equipment because they do not have the correct permissions—known as permissives—to run the equipment. Start permissives are safeguards put in place to ensure that the unit can run safely, such as having the right temperature and pressure.  

Start permissives 

Start permissives will prevent a unit from running if certain criteria are not met. To tackle the primary personnel challenge in unit start-up the, start permissives are vital to training curriculum. Areas covered include demonstrating how to monitor the status of the unit before it starts, how to troubleshoot problems, and how to allow the permissives to run a specific unit.

Let’s consider an example of start permissives with gas turbines. At the entrance of the compressor—where air comes into the unit—there are vanes positioned at a specific angle. The Inlet Guide Vane (IGV) position regulates and directs the airflow into the compressor so that combustion can begin. The specific vane angle, determined by the controller, is extremely important and must be highly accurate. Typically, the angle can have no more than a 5% difference. If there is a difference of more than 5% within five seconds, the unit will not run. This is to avoid physical damage resulting from lack of control of the IGV actuator, and could cause Compressor stall or surge. This is due to the high pressure and high speed air coming into the unit. 

The IGV position is the key to regulating air intake and is a common root cause in troubleshooting shutdown or start-up issues. If the vanes are at the wrong angle, the unit will not be allowed to start.  This is triggered by the controller which monitors any differences between the “command” (directive) and the “feedback” (actual unit status). Thus, vane angle is a start permissive, or safeguard for the unit, to ensure air is coming into the compressor the right way by using IGVs. 

Analyzing alarms 

Beyond startup permissives, “unresolved alarms” is another obstacle to proper start up. Whenever there is an issue with equipment, operators automatically and immediately see an alarm. In order to get the unit started, all the alarms must be reviewed for that specific unit.  There are alarms for many types of systems—but operators should focus on one piece of equipment at a time, making sure each alarm is clear. Further, operators should ensure that preventative maintenance is current and any issues have been fixed so that the unit is ready to go before it gets dispatched – or called upon on-demand to meet power needs.  

All power plants have a schedule. However, depending on the price of gas or the demand for electricity, this schedule might change suddenly. It’s important that each unit be prepared to run for an extended period of time, anywhere from a few hours to a few months. As units may need to be dispatched right away depending on market and grid conditions, it’s vital that they are ready to start up at all times.

In other industries, such as refineries, plastics, or steel, redundant systems are typically used. If one conveyor is cycled to run on a set day, maintenance or repairs will be performed on another one during that time. Before a redundant system is taken offline for maintenance or testing, operators have to ensure that the first system is going to run properly at that scheduled time. They have to keep an eye on the status of their unit by looking at all the alarms. Proper training can help operators know what to look for and what to fix before the assigned unit start time.

Often times, more than one alarm can be triggered in association with the same system. For example, in a lube oil (lubrication) system, there is a transmitter that indicates pressure. Let’s assume this pressure transmitter fails. When any transmitter fails, a diagnostic alarm will sound because the reading is out-of-bounds. In addition to the pressure sensor diagnostic alarm, another alarm might go off, indicating the pressure is low. In actuality, the pressure may not be low, instead the transmitter is sending an incorrect signal -- but the controller does not know that. So, the controller displays everything that it scans and triggers a diagnostic alarm for the sensor, indicating that the system is not pressurized. Most often, the local operator can go in and see that the pumps are running and the pressure is up to determine that a sensor failure was the root cause of the alarms.

For operators, there are two keys to optimizing outcomes:

  1. Prevent issues before they happen. By understanding what to do such as preventive maintenance, and the tools needed to proactively achieve healthy operations.
  2. Troubleshooting issues effectively as soon as they occur. Knowing how to manage alarms, trips or shut downs is crucial to maintaining operational performance.

How do you grow these two competencies?  On-going training (throughout your career) to deepen equipment and maintenance knowledge. Students who complete training courses are much better at troubleshooting, operating, and maintaining site operations because they have the tools and knowledge needed to react quickly. Learning how to operate a power plant can take a lifetime. Issues can be prevented by paying attention, learning the tools to discover what is going on, and by participating in ongoing training. 

Training works: A real-world classroom example

Earlier this year, Juan’s team conducted turbine controls training. The advanced class had around 10 people from the same company. The first day of training consisted of basic controls concepts. As the week went on, the training became more in depth. Juan came into the classroom on Wednesday to do his normal audit when he noticed an unusual situation. He saw all the students working on personal computers, as well as the HMIs (human machine interface) running their control simulation, used to train the class on their software. Simultaneously, the instructor was also reviewing the same type of drawings and diving into the logic of the customer’s software. 

The instructor explained that during the training about the students power plant, one of their units tripped. One of the managers taking the class received a phone call from their control room and was trying to provide help. 

On the first day of training, students were learning basic concepts in the classroom and by the third day, they were troubleshooting live events back to the control room at the power plant. The instructor was showing the control specifications and the piping and instrumentation diagram (P&IDs) of the system that he suspected to have tripped the unit.  The students and instructor worked together to fix the unit.

How controls training and services can help

This example demonstrates the power of Nexus Controls’ tailored training using customers’ software and drawings, and customizing each class to specific customer needs. Nexus Controls 

Conducts FATs (factory acceptance testing), provides the necessary software and creates the simulation. Training can be provided onsite as well as remote training and remote services. Experienced instructors can shift between onsite and remote training as needed, with identical training provided in either location. Customers can think of Nexus Controls training facilities as their second office - they are running their equipment at site with Nexus Controls as their backup. 

During a five-day training course, the first day is focused more toward operators, whereas the rest of the training week is dedicated to maintenance people. Instructors are present throughout the sessions, constantly showing techniques, sharing their screens, and allowing students to connect to a simulator while instructing students in real time.

If a customer would like to have a customized class, Nexus Controls can apply customer’s software to a simulation. As a result, when students complete labs and workshops, they are looking at their plant’s actual screens and logic. In addition, students can use their actual drawings and procedures to associate their logic and the signals they see on their operational screens.

As an additional customization, customers can select the content they want to focus on during the training. For example, some customers like to focus more on troubleshooting, while others would like to focus more on modifying logic, adding or replacing cards, or working with signals. The class can be tailored to the specific needs of each unique customer.  


To be effective, operators must understand their control tools. They must understand the techniques to use for all types of troubleshooting. Either before or after an alarm, operators must know what it takes for the system or unit to start properly. These techniques are generally vendor-agnostic, but the tools are vendor-specific. Training is a proven way to enhance outcomes and better equip operators.  Nexus Controls stands ready to educate operators and help enable improved operations.


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