Improved CBA Kit
New and Improved Compressed Breathing Air Analysis Kit
Our Compressed Breathing Air Analysis Kit (CBA Kit) has undergone some changes recently, which have produced a more accurate and easier-to-use format. The kit utilizes a regulator/flow meter assembly and five special detector tubes to monitor for the five substances listed in the Compressed Gas Association’s (CGA) Grade D standard for breathing air. These are carbon monoxide, carbon dioxide, water vapor, oil mist and oxygen. The limits on these five substances are listed below.
The CBA Kit offers a fast and simple means of monitoring for the above substances in compressed breathing air, and the new version of the kit offers several advantages over the old kit. First, with the switch to Kitagawa detector tubes, we have added a test for oxygen, which was not available with the old kit. Second, the kit has been redesigned with a new tube holder and a valve between the flow meter and the tube. The valve will allow more accurate sample times and eliminate flow adjustments during the sample. Third, the flow meter now comes with a factory calibration chart that will improve the accuracy of the flow meter reading.
The new Kitagawa CBA tubes offer a faster package, cutting at least ten minutes off the former total test time. All of the tubes are the length of stain type with printed scales for easy, immediate results. The oxygen test completes the package by adding the test that was missing in the old kit. The specifications on the CBA tubes are listed in the table below.
The hardware modification accommodates the new tubes and improves the accuracy of the sample times. We have eliminated the rubber tube holder that had to be stretched over the tube, and replaced it with a threaded assembly with a clear plastic protective sheath. The addition of the valve provides an instant flow start and stop so that the sample times may be reproduced more closely. Older kits may be upgraded by adding the new tube holder/valve assembly.
The flow meter now comes with a calibration chart prepared by comparing the flow meter to a Gilibrator. Use of the chart will improve the accuracy of the set flows, especially at the lower end of the flow meter scale. The CBA flow meter is a rotameter, which uses a float elevated in a tapered shaft to indicate the airflow rate. As the flow rate increases, the float is raised in the tapered shaft, and the area around the float for air passage also increases. Such devices tend to be more accurate at higher air flows than they are at lower flow rates, and the accuracy specification is usually expressed as a percentage of full scale.
For example, the CBA rotameter scale is marked from 50cc/minute to 500cc/minute and has an accuracy specification of +/- 10% of full scale. Full scale is 500cc/minute, so the accuracy specification is +/- 50cc. At 500cc/minute this is +/- 10% of the reading. At 50cc/minute, the lower end of the scale, it is +/- 100% of the reading.
The Gilibrator, which is a soap bubble flow meter, has an accuracy specification of +/-1% of reading. By comparing the rotameter to the Gilibrator, a correction graph can be produced that improves the accuracy of the CBA reading, particularly at the lower end of the scale. This is significant in this application, because the air flow rates used for the carbon monoxide and carbon dioxide tubes are both 175cc/minute, which is in the lower half of the rotameter scale. New CBA units will come with this chart. Older units may be returned to our service department to receive the calibration for a nominal fee. To use the CBA kit in its new format, follow the steps below:
1. Attach the regulator to an air bottle or adapt it to an air supply manifold
2. Fully open the control valve between the flow meter and tube holder
3. Set the flow rate for the first tube before the tube is installed
4. Close the control valve. Break the tube tips and insert the tube with the arrow pointing down
5. Install the protective plastic sheath over the tube
6. Open the valve to start the test and close it at the end of the allotted time. Read the tube immediately
This procedure applies to all the tubes except the oxygen tube. The oxygen tube requires a kit with a 50cc syringe and a small length of flexible tubing. The tube requires only 50cc of sample air, and the syringe is used to monitor the volume.
To use the oxygen tube, follow the steps below:
Oxygen Tube Instructions
Follow steps 1 through 4 above
Attach the closed syringe to the exit end of the oxygen tube using the small length of tubing
Open the valve. The syringe will begin to open as the air sample passes through the tube. Caution! The tube will become hot to the touch as the reaction occurs
When the syringe has fully extended to the 50cc mark, close the valve. Read the tube immediately. The CBA kit includes the regulator/flow meter assembly with the tube holder and control valve. The tubes, the tube-tip breaker and the oxygen syringe kit are sold separately. There are many different types of breathing air systems, and every user may not want to run all five tests. Consider the following tips in using and applying the CBA kit.
Tips for using the CBA Kit:
Carbon monoxide, if encountered in compressed air, is usually introduced from outside the air compressor (e.g., by vehicle exhaust). Do not omit this test just because a system has an oil-less compressor. (Carbon monoxide monitoring is also required under the OSHA respirator standard).
Some air systems utilize a filtration/purification unit that will include a catalyst to convert carbon monoxide to carbon dioxide in the event of carbon monoxide intrusion. It is important to monitor for both substances in systems that use these catalysts. Water is not monitored as a toxic substance (obviously we can breath in the rain), but it should be minimized to prevent other problems. Water can corrode the air delivery system, it can cause respirator regulators to ice up in cold weather and it can destroy the catalysts used in air purifying systems.
Water also affects the reading on the oil mist tube. The oil mist tube goes from yellow to blue to indicate the presence of oil. Water causes the original yellow color to turn to an orange color, but the tube will still respond properly to oil mist up to a level of 160 mg/M3 of water. High level moisture (i.e., greater than 160 mg/M3) will cause the tube to revert back to yellow and become unresponsive. It is important to know the water vapor level when using the oil mist tube. (Our old oil mist tube had a similar interference problem with humidity).
The oil mist tube responds to petroleum oils and not to synthetic oils. If the compressor uses a synthetic oil, an alternate test method should be used.
Oxygen levels in compressed air should not vary significantly from the level of the make up air, however the quality of the make up air is an issue that should not be overlooked (for carbon monoxide and carbon dioxide as well). In bottled breathing air that is made from reconstituted air (i.e., liquid nitrogen and liquid oxygen re-blended), the testing of the oxygen level is imperative.
For further information on our CBA kit contact our Answer Center at (800) 451-9444 extension 684.