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



The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by Control Engineering subscribers. Vote now (if qualified)!
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Maximize ROI with integrated control system approach; Microcontrollers vs. PLCs; Power quality; Accelerate and rewire IIoT; Traits for excellent engineers
HMI effectiveness; Distributed I/O; Engineers' Choice Award finalists; System Integrator advice; Inside Machines
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Programmable logic controllers (PLCs) represent the logic (decision) part of the control loop of sense, decide, and actuate. As we know, PLCs aren’t the only option for making decisions in a control loop, but they are likely why you’re here.
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me