Driving out the dampness

How can you get rid of moisture inside cabinets and enclosures?

11/19/2010


Dear Control Engineering: I was reading the article about cabinet dryers. How does that technology work? The article doesn’t explain it.

Compressed air cabinet dryers.In this particular case, the approach dries out the interior of the enclosure by purging it with very dry air. If you install one, you have to run a compressed air line to the enclosure and install one of the filter setups. The filter is the interesting part. It’s a two stage process: The first part is a normal coalescing filter that removes oil and water droplets in the line. Those are pretty common with air systems. The second filter (the longer vertical section) is a membrane module that consists of a bundle of hollow membrane fibers which are permeable to water vapor. As the air passes through the center of these fibers, water vapor permeates through the walls of the fiber and dry air exits from the other end of the fiber. A small portion of the dry air is redirected along the shell side of the membrane fiber to carry away the moisture which surrounds the fiber and the water vapor is vented to atmosphere. The combination of a coalescing filter and a membrane filter provides air with a dew point of -7 °F (-22 °C) even if the air coming into the system is saturated. That’s really dry air.

In operation, you add some sort of port and bleed this dry air into the cabinet. Any moisture that gets inside will evaporate and be carried out of the enclosure as the dry air leaks out. Since the interior is slightly pressurized, it also reduces the likelihood that dust will get inside, and it makes it harder for water to get in as well. This type of purging technique is also used in explosive environments as a safety measure.

As the article says, no electricity is required, however this approach does consume compressed air. The amount will depend on the size of the cabinet and severity of water leaking. Both types of filters empty accumulated moisture automatically so they require very little maintenance.

Peter Welander, pwelander@cfemedia.com



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
2015 Top Plant: Phoenix Contact, Middletown, Pa.; 2015 Best Practices: Automation, Electrical Safety, Electrical Systems, Pneumatics, Material Handling, Mechanical Systems
A cool solution: Collaboration, chemistry leads to foundry coat product development; See the 2015 Product of the Year Finalists
Raising the standard: What's new with NFPA 70E; A global view of manufacturing; Maintenance data; Fit bearings properly
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again
Migrating industrial networks; Tracking HMI advances; Making the right automation changes
Understanding transfer switch operation; Coordinating protective devices; Analyzing NEC 2014 changes; Cooling data centers
Upgrading secondary control systems; Keeping enclosures conditioned; Diagnostics increase equipment uptime; Mechatronics simplifies machine design

Annual Salary Survey

After almost a decade of uncertainty, the confidence of plant floor managers is soaring. Even with a number of challenges and while implementing new technologies, there is a renewed sense of optimism among plant managers about their business and their future.

The respondents to the 2014 Plant Engineering Salary Survey come from throughout the U.S. and serve a variety of industries, but they are uniform in their optimism about manufacturing. This year’s survey found 79% consider manufacturing a secure career. That’s up from 75% in 2013 and significantly higher than the 63% figure when Plant Engineering first started asking that question a decade ago.

Read more: 2014 Salary Survey: Confidence rises amid the challenges

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.