If your recent air sample has failed due to high Water Vapor levels, Analytical Chemists Inc. can assist you in identifying the source of the contamination and provide solutions to correct the issue.
Understanding Water Vapor Contamination in Compressed Air
Water vapor in compressed air is a critical factor that can affect air quality and the performance of your system. High levels of water vapor typically indicate issues with your compressor’s filtration system or environmental conditions.
- Saturated Filter Cartridges: A common cause of high water vapor readings is a saturated filter cartridge. As filters absorb moisture, they become less effective at removing contaminants like carbon monoxide. If your filter is near or past its recommended service life, replacing it can often resolve the problem. Check your maintenance records to see if it’s time to replace the filter cartridge. If the filter is due for replacement, doing so should restore your air quality.
- Temperature and Filter Life: High temperatures at the compressor’s inlet can drastically shorten the life of purification filters. Filters are rated for specific operational hours at or near 70°F. When the inlet temperature exceeds this threshold, filters will degrade faster. Water vapor contamination tends to be more problematic in the summer months when ambient temperatures rise, further exacerbating the issue.
- Issues with Compressor Drainage: If your filter cartridges are not due for replacement, other potential causes of water vapor contamination could be problems with the compressor’s manual or automatic water drain systems, or the priority valve. Additionally, improperly seated filters or damaged filters may not perform as intended, allowing excess water vapor into the air system.
- Additional Factors to Investigate: Consider investigating other elements of your air system, such as recent hydrostatic tests on storage bottles, the use of fill hoses longer than 5 feet, or leaving fill hoses unpressurized and valves open. These factors can contribute to water vapor contamination. It’s also important to consider if the compressor has been recently de-pressurized or relocated, as these changes can affect moisture levels.
Water Vapor Levels and Compliance
It doesn’t take much water vapor to fail an air quality test. For example, 1 milliliter (about 20 drops) of water in a 1.7 cubic foot cylinder at 4500 psig equals 90 ppm of water vapor. Given that the allowable limit for water vapor contamination is often very low, even a small amount of moisture can result in non-compliance.
Onsite Water Vapor Detection and Solutions
To help you quickly identify and address water vapor issues, we offer an onsite detector tube test. This test allows you to perform an immediate check of water vapor levels without waiting for a full lab report, helping to minimize downtime and keep your system running smoothly.
How to Use the Onsite Water Vapor Detector Tube
- Prepare the Detector Tube: Before inserting the tube, break both tips to allow the filler material inside to react with the presence of water. The arrow on the tube should point away from the fitting during testing.
- Run the Test: Set the flow rate to 50 LPM and run the test for 10 minutes. During this time, the yellow filler material inside the tube will change color, indicating the presence of water vapor. If the color change reaches the 200 mark at any point, remove the tube and record the time on the data sheet.
- Reading the Results: After completing the test, identify the farthest color change on the tube between 0 and 200. Refer to the chart provided to locate the corresponding water vapor reading based on the flow rate (between 40 and 60 LPM). This will give you the approximate water vapor level in °F.
For example: If tube showed color change to 50, and flowrate was 50 LPM, the result would be -49°F. The number between 0 and 200 should be written on the data sheet not the dew point from the chart on the next page.
Above area marked “Pass” is for high pressure air used for SCBA; with a -65°F limit per CGA Grade D/NFPA 1989. Refer to your check-list instructions for a complete range of flowrates and further details.
If your recent air sample shows a failure due to water vapor contamination, Analytical Chemists Inc. is here to help you identify the source of the issue and guide you through troubleshooting steps.
Understanding the Pass/Fail Determination for SCBA Air Samples
For high-pressure air used in Self-Contained Breathing Apparatus (SCBA), the allowable water vapor limit is set at a -65°F dew point according to CGA Grade D and NFPA 1989 standards. If your detector tube reading falls within the “Pass” area, your sample meets this requirement. However, if the reading is outside this range, it indicates an issue that requires corrective action.
To resolve the problem, follow the troubleshooting checklist below, take the necessary steps to address the issue, and then retake your sample to confirm the correction.
Troubleshooting Checklist for Water Vapor Contamination
- Purification Filters / Depressurized Filters
- Issue: High ambient air temperatures (above 70°F) can significantly shorten the life of purification filters. Filters degrade over time, especially when exposed to heat.
- Action: Check if it’s time to replace the filters. Regular maintenance and timely filter changes are essential to ensure they continue to remove contaminants like water vapor effectively.
- Manual/Automatic Drain or Priority Valve
- Issue: Malfunctioning drains or valves may lead to excess water in the system, which in turn reduces filter effectiveness.
- Action: Ensure that the drainage system is working properly to remove water from the air supply. If necessary, clean or repair the valves and drains.
- Remote Fill or Hose Reel
- Issue: Long hoses (greater than 10 feet) can accumulate and retain water, which may not be purged by a short 1-2 minute flush.
- Action: Always use a short fill hose (5-10 feet) or sample directly from the containment fill station. If using long hoses, ensure a thorough purge before sampling.
- Recent Hydrostatic Testing
- Issue: After hydrostatic testing, bottles may retain moisture. Without proper drying and pressurization, the moisture can lead to high water vapor levels in the air sample.
- Action: Ensure that bottles are properly dried after testing and immediately pressurized with dry air to prevent water contamination.
- Valves Left Open
- Issue: Leaving valves open allows ambient air, which can contain 10,000-50,000 ppm of water vapor, to enter the system.
- Action: Always purge the system sufficiently to remove any water vapor accumulated from open valves or ambient air.
- Sampling from Storage Tanks
- Issue: If your sample is taken from storage, it may contain water vapor that the compressor is no longer producing.
- Action: Take a sample directly from the compressor to check if it is producing dry air. If the compressor is fine, drain and refill the storage tanks with dry air, which may require 2-3 fills to remove water. You can also request additional detector tubes to perform multiple checks without needing a full air sample.
- Cracked Detector Tube
- Issue: Cracks in the body of the detector tube can lead to unreliable results, as the air may leak out, affecting the test accuracy.
- Action: Ensure that only the tips of the detector tube are broken. A crack along the tube’s body invalidates the test results.
- Wet Tube Fittings
- Issue: If multiple samples are taken in quick succession, water may accumulate in the tube fitting, leading to inaccurate readings.
- Action: Dry the fittings thoroughly between uses to avoid contamination from residual water.
Key Considerations
Water vapor contamination is often subtle—just 1 milliliter of water (about 20 drops) in a 1.7 cubic ft cylinder at 4500 psig can equate to 90 ppm of water vapor. Since the allowable limits for SCBA air are strict, even a small amount of moisture can cause a failure.
Next Steps
Once you have taken corrective action based on the checklist, retake your sample to verify that the problem has been resolved. If the issue persists or you need further assistance, Contact Us or call us at (888) 724-7522. We offer free resampling, and we’ll provide new supplies to help you continue troubleshooting.
Thank you for choosing Analytical Chemists Inc. We appreciate your continued trust in our services for air quality testing. Let us help you maintain the highest safety standards for your compressed air system.
