How to Listen to Your Mill Equipment’s Warning Signals

In the fast‑paced environment of a pulp and paper mill, subtle clues can signal impending equipment failure. Listening to these signals is essential for maintaining reliability and preventing costly downtime.

Think of a motor that feels sluggish, a pump that leaks, a bearing that hums, or a steam line that coughs. These are not random noises; they are your equipment’s way of communicating distress. Unfortunately, many mill operators become desensitized—what we call “mill blindness”—and these warnings are ignored.

Basic Condition Monitoring

One common example is the leaking rotary joint. In many mills, a leak is considered normal and is only detected after steam escapes the joint. However, leaks usually indicate wear of the carbon ring inside the joint. The carbon ring is designed to wear and then leak after a predetermined amount of use. For instance, a Valmet model requires a carbon ring replacement when the wear distance (see Figure 1) reaches 0.59 inches (15 mm). Many Johnson joints include a pin that marks the wear level. Regular inspection and timely replacement of the carbon ring can prevent larger failures and protect the plant’s steam system.

Stored Items

Spare parts management is another critical factor that can influence equipment reliability. Poor handling of spares can lead to hidden deterioration that only becomes apparent when a failure occurs.

Components such as belts, couplings, and O‑rings are perishable. For example, the popular orange‑peel coupling has a “best before” date. While it is engineered to last five to six years whether in use or in storage, it is not uncommon to find couplings that are five years old or older in inventory, thereby exceeding their useful life.

Bearings should be wrapped and sealed to protect them from contaminants. Yet it is not unusual to discover unwrapped, dusty bearings in storage rooms. In addition, vibrations from nearby equipment can cause fatigue damage when bearings are left stationary. Rotating motor shafts a quarter turn periodically can mitigate this risk.

About the Authors

Torbjörn Idhammar, Vice President, and Michael Lippig, Business Development Manager, lead IDCON Inc., a Raleigh, N.C.‑based consulting firm specializing in reliability and maintenance management. They provide education, training, and implementation of best practices to improve operational reliability. For more information, visit www.idcon.com or email info@idcon.com.