Tips for Keeping Your Test Chambers in Tip-Top Shape

November 3rd, 2005

Probably the most enjoyable part of my job is covering advanced technology. Nearly every day something crosses my desk that makes me sit back and say, “How cool”! I know, however, that it’s not always the most advanced technology that gets the job done.

Just as frequently, it’s paying attention to the mundane details that make the difference between a successful test operation and a marginal one. Equipment maintenance is one of those “details” that need attention.

Poorly maintained equipment can cause problems in several ways. First, it can invalidate test results. Say you have to run an engine operating test at –40 deg C. If your chamber has not been calibrated properly, however, the temperature inside the chamber may never get that low even though the controls say it has. Because of this, you may have to throw out the results and re-run the test.

Second, neglecting maintenance can cause premature failures, which can cost a lot to fix and seriously delay projects. Bill Arvo, a sales engineer for Weiss Technology, noted, “A test chamber is like a car—without proper maintenance, you will eventually have problems which can get expensive.”

With that in mind, I asked maintenance experts from several of the leading environmental test chamber manufacturers to give us tips on how to keep your chambers running smoothly. Here’s what they had to say:

1. Keep it safe. Periodically, check all interlocks and safety features for proper operation. Safety should be your primary concern. Large chambers require high voltages and currents, and if the interlocks don’t work properly, they can’t protect your maintenance personnel.
2. Keep on schedule. Establish a regular maintenance schedule, but be flexible. This may sound contradictory, but according to Keith Bauer, technical service advisor for Lunaire, Ltd., Willamsport, PA, maintenance frequency depends on how you use the chamber, the environment in which you use it, and other circumstances. Because of this, it is difficult—and perhaps unwise—to set a hard and fast maintenance schedule. A schedule that is suitable for one user, may be completely inadequate for another.
3. Keep a maintenance log. In the log, record operating notes, pressures, temperatures, and electric readings. The log is valuable because it will help maintenance and service people by documenting long term trends and by showing parameter levels when the chamber is operating properly.

   This log may also be required when applying for certifications, such as ISO 9000 or QS-9000. Consult with your registrar about what types of information to keep in the log and the format for the log.

4. Keep it calibrated. Calibrate temperature and humidity controls regularly. These controls are electronic instrumentation and need calibration just like the multimeters and temperature meters you may use in the lab.

   While you’re calibrating the instrumentation, Arvo also suggests checking the controls, such as the EPR valve, pressure switches, and solenoid valves, as well as the gauges, switches, and lights on the control panel. A malfunctioning LED or light bulb could create a problem if it fails to warn you of an out of spec condition.

5. Keep it clean. It’s hard to keep chambers used for testing vehicles clean, but there are good reasons for doing so. Keeping chambers clean help extend filter life and help maintain a professional appearance. Jeff Earhart, service manager for Cincinnati Sub-Zero, Cincinnati, OH gives the following advice about cleaning:
   • Wipe or vacuum out all debris.
   • Clean interior surfaces with a damp cloth, mild detergent, or stainless steel cleaner. Avoid cleaners that are abrasive or leave a residue. Do not use steel wool.
   • Clean the chamber exterior and door gaskets with a damp cloth or a mild detergent. If a detergent is used, test a small area to make sure it does not damage the finish.

   Bauer also suggests cleaning any dust or dirt around condenser coils (if you have an air-cooled refrigeration system) with a brush or vacuum cleaner.. Dirty condensers reduce the efficiency of the system and may trip circuit breakers if they get dirty enough.

   Also, remember to change your chamber’s air filters when they get dirty. Too much dirt can restrict air flow, which will cause blowers and other motors to run hot, which can lead to premature failures. Restricted airflow will also raise the operating temperature of the electronic controls, which can damage them.

6. Keep cool. All three of our experts suggested periodic checks of the refrigeration system. To ensure that the refrigeration system remains in good working order, first check the compressor oil level and pressure. Look for any oil leaks, which maybe an early indicator of an imminent failure.

   Measure the discharge line temperature. A low temperature is an indication that the unit is not operating properly.

   Inspect the insulation on all refrigeration lines and look for frost on the lines while the compressor is operating. Replace the insulation where necessary. Also, look for abrasion damage caused by excessive vibration. If you find damage, locate the source of the vibration and isolate the lines from it.

   Inspect and clean all blower wheels and fan blades. After cleaning, make sure that they are tight on their shafts and spin freely.

7. Keep the current flowing. In addition to inspecting the refrigeration system, they all also recommended checking the electrical system. For example, Arvo suggests checking the current draw of the compressors, blowers, and fans in the system. By comparing these values to specifications and logging these values in your maintenance log, you can head off a disaster by replacing them before they fail.

   Bauer recommends inspecting the electric heater elements regularly. Look for sagging elements, broken insulators, and other defects. Replace, if necessary.

   Earhart says to inspect all wires for loose connections and burnt or frayed wires. Also, inspect contactors or relays for signs of heat damage. These are indications that electrical circuits are drawing too much current, and the cause of this should be found and fixed before the system fails catastrophically.

Preventive maintenance may be expensive, but Arvo estimates that poor maintenance can account for as many as 50% of environmental test chamber failures. By following these tips, however, you should be able to prevent many of those failures from occurring. And in the end, that will save you both time and money.

Entry Filed under: Environmental/Durability Test