7 Tips for Designing Combustion Control Panels
Developing or specifying standard design panels that can be optimized for specific applications allows oven and dryer OEMs to avoid having to develop custom combustion controls for each heat processing system.
Process heating equipment OEMs that build furnaces, ovens, dryers, kilns and boilers heated by gas burners face challenges related to the development of combustion control panels. While combustion controls are essential for the safe and efficient operation of burners, each customer or project often has its unique requirements. This can lead to many non-standard panel designs, complicating engineering, commissioning, maintenance and service.
Specific end-user requirements also can result in the use of many different control components (i.e., multiple versions of flame safeguards, temperature and limit controllers, fuel-air ratio control subsystems and PLCs). The larger the variety of hardware components used, the harder it is to maintain an inventory of spare parts and deal with warranty issues.
Process heating equipment OEMs can benefit from a standardized, flexible combustion control panel design that:
- Works across many applications with minimal changes.
- Controls burners with different sequencing and fuel-air ratio requirements.
- Uses common hardware.
- Reduces the engineering required for each project.
- Can be monitored remotely to maximize equipment uptime and minimize warranty repair costs.
In this article, I will highlight seven best practices for developing such a solution, from specifying the hardware to designing, implementing and testing it.
This is an example of a secure cellular modem and app that is configurable for the remote monitoring of process heating equipment.
Tip 1: Standardize on a Single Design
Because most projects have a few unique requirements, OEMs can fall into the trap of designing a new combustion control panel for each customer or application. A better strategy is to define one or two standard panel designs that cover around 80 percent of the requirements. For each specific application, this standard design can be amended with the features needed for each customer via configuration.
The specification for the standard panel design should be created by a person or group in the company with the best overall picture of different end-user needs. The standard design should be software- and hardware-configurable so that key parameters can be adjusted for each project. When a customer has specific needs, standardized designs can provide an effective foundation for non-standard projects and, if designed properly, can be modified easily.
By minimizing the amount of engineering time needed, using a standard design will shorten the time required to convert a customer order into a manufactured, tested and commissioned process heater control.
Tip 2: Build Flexibility into the Design
When developing a standard design, think about the requirements users will have for each part of the system. Consider the requirements within each category below to include in a single, standardized design:
- Direct burner ignition, interrupted or intermittent piloting?
- Single- or dual-flame sensing?
- Sequencing options such as valve proving, early spark termination, pilot and main valve timings and pilot valve hold.
Fuel-Air Ratio Control
- Parallel positioning with O2 trim, fully metered air-fuel ratio control and flue-gas recirculation options.
- Number and type of actuators and variable-frequency drives (VFDs).
- Actuator and VFD position and frequency error tolerance settings.
- Number and type of thermocouples, RTDs and 4 to 20 mA transmitters.
- Special logic such as dual-sensor comparisons and sensor averaging.
- Local PID or remote firing-rate control?
- Sensor and control loop accuracy.
- Remote setpoint options.
- User interfaces including panel door-mounted touchscreen HMI, lamps and control buttons, discrete controller and flame-safety displays.
- Ability to connect to an upstream PLC or DCS system, if desired.
In addition to the above components, other best practice requirements to consider include using SIL-rated burner controls. Using such controls means that the design will work for all applications, including those where the customer requires SIL approval. Another best practice is to include first-out annunciation, which often is skipped in cost-sensitive applications. First-out annunciation saves time during the life of the system by making it easier to identify the root cause behind burner faults. In addition, remote monitoring (which will be discussed in more detail) provides a long-term benefit by helping to prevent outages.
A gypsum product manufacturer improved its production line performance and reliability with integrated combustion controls.
Tip 3: Select the Right Hardware
Traditionally, panel hardware consists of:
- Standalone flame safeguard.
- Fuel-air controller.
- Single-loop temperature control.
- High temperature safety devices.
All of these devices are wired together and integrated with an external, upstream process PLC or DCS. This hardware meets system requirements, but it requires the use of different versions of each of these devices depending on project requirements (i.e., a different flame safeguard is needed whenever the safety timing changes). It also is labor intensive due to the intra-device wiring within the panel.
In order to implement a standard combustion control design, companies have to move away from fixed-function hardware to a configurable and programmable system. Integrated combustion-management systems incorporate all the devices mentioned into a modular hardware platform. As a result, the same hardware platform is used in every panel that ships, and the software is configured to control customer-specific requirements.
As an example, some integrated combustion-management systems incorporate burner management, fuel-air ratio control, combustion safety limit control, first-out annunciation and a programmable PLC and user HMI into a single system. All of the combustion-control and burner-management functions are user configurable and agency certified. The hardware design eliminates most internal panel wiring, reducing panel-fabrication costs.
It also is possible to use a SIL-rated PLC and develop a program for combustion management. The downside of using a generic SIL-rated PLC is that the hardware costs can be higher because the generic devices may have features not required for combustion control. Also, engineering time and costs will be higher because the OEM will need to develop programs for burner sequencing and other safety functions and then submit this program logic for agency approval for safety functions like fuel-air ratio and high-temperature limits. With an integrated combustion-management system, the hardware is designed for the application and the program logic is already agency certified.
Tip 4: Establish a Function Block Library
Once the hardware is selected, it is time to program it. A simple, visual way to implement a standard design into hardware is to use function-block programming. Establishing a library of function blocks that support common combustion-control actions allows the company to address multiple applications with little or no additional engineering or programming.
Combustion controls can integrate burner management, fuel-air ratio control, combustion safety limit control, first-out annunciation and a programmable PLC and user HMI into a single system. This system’s hardware design eliminates most internal panel wiring, reducing panel fabrication costs.
Tip 5: Include Remote Monitoring
When a furnace, kiln, fluid heater or boiler is not working, the cost for the end user can be tens of thousands of dollars per hour of lost output. Using a remote-monitoring system in the standard panel design allows the OEM to notify the end user of issues that may lead to an outage and to provide remote assistance in case an outage occurs. It also makes it possible to arm field technicians with details of the problem and necessary spare parts before they travel to the site. Finally, including remote monitoring in the panel allows the OEM to create a preventive maintenance-service package based on actual field conditions.
Remote monitoring requires upfront planning during the design phase. The decision needs to be made regarding which parameters should be monitored for analysis and alarming and who should be notified in case of problems.
Selecting the correct hardware for a remote-monitoring solutions will influence the security of the system and its acceptance by the end user’s IT team. Many industrial plants do not permit remote-monitoring hardware to be connected to the factory control network due to cybersecurity concerns. Using a cellular modem for monitoring the process heating equipment allows it to operate independently from the site’s IT network. Cellular modems can be wired hundreds of feet from the panel and should connect to a secure backend server.
Tip 6: Reduce the Scope if the Design Becomes Too Complex
If the design becomes unwieldy, the functional requirements need to be narrowed or further design added. Two indications of an overly complex design are too many difficult-to-explain configuration parameters and convoluted panel wiring for sensor or control signal options.
By using standardized, configurable combustion control panel designs, process heating equipment OEMs can decrease project engineering time, reduce component inventory, deliver more reliable systems for their customers and provide better service in case of problems.
Tip 7: Allow Adequate Time for Testing
Thorough testing of the complete panel might seem like an obvious step, but it can be time consuming due to the number of configurable functions to test. Performing tests using PLC program-simulation tools and in live-fired environments helps prevent manufacturing delays and identifies design errors before field installation and commissioning.
In conclusion, by using standardized, configurable combustion control panel designs, process heating equipment OEMs can decrease project engineering time, reduce component inventory, create more reliable systems and help companies provide better service in case of problems. With the addition of remote monitoring, OEMs also can create their own preventive maintenance service programs for end users.
Gypsum Product Manufacturer Improves Production Line Performance and Reliability
How does an integrated combustion controls system help an end user? This case study shows how a gypsum products manufacturer used an integrated combustion control system to improve operations.
A gypsum wallboard manufacturer had begun to experience increasing thermal process incidents that posed safety risks to plant personnel and threatened production line reliability. The company’s legacy thermal systems lacked the connectivity and communications capabilities to highlight performance trends, potential failures and error tracking. When issues occurred, plant personnel could not describe them in enough detail for remote support, necessitating costly visits to the site.
The company decided to implement a combustion-management system that combines configurable safety features with programmable logic in a modular burner control platform. The solution reduces control room panel footprint and can be customized for any combustion application. It also included a cloud-based offering to provide access to thermal process data from anywhere. Gypsum company personnel can view alerts and status information on their smart phones or tablets and drill down as necessary.
Following deployment, the combustion-management system helped the gypsum products manufacturer to spot and resolve a kiln interruption that had stopped the production line for hours. The data provided by the control system allowed the gypsum company’s team to find the problem in hours rather than the days it would have taken previously. As a result, the gypsum products maker avoided more than $100,000 in lost production, scrap and emergency plant and third-party services.
Additionally, with the new combustion system, troubleshooting is eased. Maintenance technicians arrive at the plant with the correct tools to repair problems. Plant engineers can stay ahead of issues by using the combustion-management system to identify nuisance fault trends and predict failures.