Dunphy Ratiotronic 6000 Control Upgrade on 20MW Cochran Boiler

AH Control Ltd recently completed a major combustion-control upgrade and recommissioning project on a 20,000 kW (20 MW) Cochran dual-furnace industrial boiler fitted with two Dunphy burners.

20 MW Cochran dual-furnace boiler fitted with Dunphy burners.

The challenge

The existing burner management and combustion control system utilised older Dunphy Ratiotronic 6000 Series equipment. With the original controllers and grey HMI equipment becoming obsolete, the system required upgrading to improve long-term reliability, maintainability and continued safe operation.

Both burners were operating with the older Ratiotronic 6000 arrangement, comprising the base control units and original HMIs. Rather than waiting for an obsolete component to fail, the combustion controls on both burners were upgraded.

Before: original Dunphy Ratiotronic 6000 Series burner controllers prior to the control upgrade.

After: upgraded Dunphy Ratiotronic 6000 Series control interfaces following installation and recommissioning.

Dunphy control system upgrade

AH Control removed the obsolete control equipment from each burner, including both base 6000 units and the original grey HMIs, and installed the updated Dunphy Ratiotronic 6000 Series controls with the new blue HMI interfaces.

This was not simply a component replacement. Following installation, both burner control systems were fully configured and recommissioned, including all relevant operating parameters and options before the burners were returned to service.

Updated burner control panel following the Dunphy Ratiotronic 6000 control upgrade.

Internal control equipment associated with the upgraded Dunphy Ratiotronic 6000 burner control system.

Full combustion recommissioning

Once the new controls had been installed and configured, a complete combustion commissioning procedure was carried out across the full firing range of each burner. The combustion curves were carefully established and optimised to maintain approximately 4% O₂ throughout the firing range.

Maintaining the correct air-to-fuel relationship throughout modulation helps achieve maximum practical combustion efficiency, stable burner operation, reduced excess-air losses, low CO and NOx emissions, reliable flame stability and consistent performance.

Rather than concentrating solely on high-fire figures, the complete firing curve was checked and adjusted to achieve good combustion performance as each burner modulates through its operating range, supporting the site's applicable emissions requirements including the Medium Combustion Plant Directive (MCPD).

Safety and interlock testing

Combustion performance is only one part of correctly commissioning a burner control system. Following setup, AH Control carried out functional testing of the associated boiler and burner safety circuits, interlocks and operating controls to prove that the plant responded correctly under both normal and fault conditions.

The installation was also tested through the site's SCADA system, confirming that the boiler controls responded correctly to the site's remote control requirements. Only once combustion, control and safety functions had been proven was the system returned to normal operation.

The result

The completed upgrade gives the site a modernised combustion-control system while retaining the existing large-scale boiler and burner plant. Both burners now benefit from updated Dunphy control hardware, newly commissioned combustion curves and fully tested safety and control functions.

For the customer, the project provides three particularly important benefits: improved reliability, continued maintainability and optimised combustion performance. On a 20 MW boiler, even relatively small improvements in combustion performance can become significant because of the amount of fuel consumed by the plant.

Specialist industrial combustion engineering

AH Control Ltd provides specialist industrial burner servicing, combustion commissioning, burner control upgrades, obsolete control replacement, combustion optimisation, fault finding, boiler controls, safety and interlock testing and preventative maintenance.

If your commercial or industrial boiler or burner controls are becoming obsolete, AH Control can assess the existing system, identify obsolescence risks and advise on suitable upgrade options. We fix what others can't.