Routine Diagnostics Detects Damper Malfunction and Actuator Leak

A leading, recycled pulp mill in the Midwest.

During a routine valve diagnostic visit on-site at the customer’s production facility, a Novaspect Valve Reliability Specialist discovered a Travel Deviation and a Low Drive Signal for a damper on the boiler’s Nitrogen Oxides (NOx) recirculation line in the Status Monitor and Alert Tab of their online AMS Device Manager software.  AMS Device Manager is used to efficiently manage instrumentation and when utilized in the online configuration it provides real time instrument condition monitoring. 

Dampers play a vital role in optimizing the combustion process in boilers and managing NOx emissions that are regulated by the Environmental Protection Agency (EPA). They ensure that airflow is directed where needed, regulating temperature to prevent overheating, pressure build-up, or other potential hazards that could compromise worker safety and equipment integrity.

Travel deviation refers to the difference between the intended position of the damper and its actual position during operation. Significant travel deviation in the damper can lead to inefficient combustion processes, inaccurate airflow control, and potential emission control problems. In this scenario, the damper was traveling between 42% and 90% and is supposed to turn 90 degrees, but it was only rotating 40 degrees when the alert was created.

A low drive signal indicates that the actuator responsible for moving the damper is receiving a weaker or lower-than-expected signal to initiate movement. It can prevent the damper from reaching the required position, leading to operational inefficiencies, improper airflow control, and potential safety risks.

The customer was not aware of the issues with the damper and actuator, and the equipment was not listed for maintenance on the work order backlog. Upon further investigation, the NOx trend over the previous two weeks was trending higher—a situation that could result in significant fines from the EPA.

To determine the root cause, Novaspect’s reliability technician climbed up a vertical ladder to a remote location of the plant to decouple the damper and position it back to zero. After reassembling the equipment, the technician connected to the damper using Fisher™ FIELDVUE™ ValveLink™ software, ran it through diagnostics, and determined that it wasn’t rotating full travel because the block pilot bearings weren’t greased.

In addition, the technician performed a manual calibration on the actuator and found it was not saturating or making a complete stroke, and it was leaking because the set screws had slipped on to the shaft which was causing the damper to hit the internal stop and limit travel.

Rebuild kits for the obsolete actuator were no longer available, therefore the customer selected a new Bettis RPED-0065 actuator and DVC6200AD positioner.

Novaspect installed the new damper assembly, performed auto-calibration, and it is now operating throughout its full travel range and controls precisely.

By leveraging advanced diagnostic tools and the proven expertise of Valve Reliability Specialists at Novaspect, the customer not only identified the root cause of the problem, but also implemented a solution that restored their system to optimal performance.

Additionally, by detecting and correcting the issues promptly, the recycled pulp mill company averted potential regulatory compliance issues and associated financial penalties of several thousand dollars or more related to the increased NOx emissions.

Don't leave your plant's reliability to chance. Improve reliability by spotting problems with state-of-the-art technology before they affect your process. Contact the experts at Novaspect, your local Emerson Impact Partner, to learn more about how we can help.