What is the typical acceptable dew point for instrument compressed air in the paper-making industry?

The Importance of Instrument Compressed Air in the Paper Industry

In the papermaking process, instrument compressed air is primarily used to operate various pneumatic control valves, actuators, and precision measuring instruments. Given that paper mills typically operate in high‑temperature, high‑humidity environments, excessive moisture in the compressed air can readily cause internal corrosion of pneumatic components, premature aging of seals, and even pipe freezing during cold seasons, thereby severely compromising the stable operation of the production line. Consequently, stringent control of the compressed air dew point temperature is a critical factor in ensuring the reliability of a paper mill’s instrumentation and control systems.

Acceptable range for the dew point of instrument compressed air

When discussing dew-point standards, it is essential to clarify.Pressure dew pointandAtmospheric dew pointThe distinction. In engineering practice, the pressure dew point is typically used as the evaluation criterion. For instrument compressed air systems in the paper-making industry, the standard acceptable pressure dew point range is generally within-20℃ To -40℃Between.

This standard is based on a fundamental principle: the pressure dew point of compressed air must be lower than the lowest ambient temperature in which the system operates. Under most climatic conditions, the pressure dew point should be maintained between –20°C and – 40℃, which can effectively ensure that, even in extremely low winter temperatures, no liquid water will condense in the pipelines and instruments.

Key factors affecting dew point setting

Although −20°C to −40°C is the industry’s standard range, the specific acceptable dew point value must be assessed comprehensively in light of the following factors:

• Local historical record of the lowest temperatureThis is the most direct basis for setting the dew point. The dew-point temperature must be lower than the lowest recorded ambient temperature in the local historical data; it is generally recommended to set it at least 10°C below that value to allow for a safety margin.
• Pipeline Laying and Working EnvironmentIf the instrument compressed air piping is installed outdoors without insulation, or if certain sections are located in cold, damp, dead‑end areas, a lower dew point will be required to prevent condensation.
• Precision and Sensitivity of Pneumatic ComponentsCertain high-precision proportional valves or precision sensors on paper machines are extremely sensitive to moisture; the compressed air used at such critical points may require more stringent drying treatment.

Potential Risks of Exceeding the Dew Point Limit

If the dew point of the compressed air used by the instrument fails to meet specifications, moisture entering the control system can trigger a cascade of problems. First, moisture will wash away the lubricating oil film inside pneumatic actuators, causing valves to seize and operate sluggishly. Second, moisture combines with airborne impurities to form sludge, which can easily clog the instrument’s tiny air passages, leading to distorted measurement signals. Furthermore, during winter in northern regions, free water freezing at throttling points can directly shut off the air supply, resulting in unplanned shutdowns.

How to ensure the system dew point consistently meets specifications

To keep the dew point of instrument compressed air within acceptable limits, paper mills must establish a robust drying and monitoring system. At the air‑source treatment stage, adsorption dryers are typically used to remove moisture to a deep level. At the end of the distribution network or at critical points of air consumption, it is advisable to install online dew‑point monitors for real‑time surveillance. In addition, regularly replacing the desiccant in the dryer and draining condensate from air receivers and filters are essential routine tasks for maintaining the system’s dryness.