What are Humidity Indicator Cards and Plugs?
Humidity Indicator Cards and Plugs provide external monitoring of humidity levels inside containers. When used in conjunction with desiccant and breather valves as part of an environmental control system, humidity indicator plugs and cards help to safeguard cargo from the deleterious effects of moisture, which can build up inside of a container.
No two situations are the same in the environmental control industry and, as a result, questions concerning everything from the basic installation of plugs and cards, to developing customized environmental control systems are common.
As Design Engineering Manager, Pat Lane is responsible for supervising AGM’s engineering design department, conducting product research and development, as well as collaborating with the Vice President of Engineering on new product designs. In addition, Lane serves as AGM’s primary contact to customers seeking answers to difficult environmental control questions.
7 Common Questions
1) “I need an indicator that can sense 50 ppm (parts-per million) of moisture. Will your product do that?”
No, you need a humidity measuring instrument (such as a hygrometer), not a humidity indicator. That said, we [AGM] do provide a moisture analysis service, the Hydra20, which is capable of determining the environmental control materials and processes required to maintain a sealed environment at a specific humidity level for any duration.
2) “How low of a humidity can AGM humidity indicator cards sense?”
Standard rectangular cards are available as low as 5% and 8%. Humidity Indicator Plug cards are only as low as 10%. This is because establishing the color of the card in the plug is more difficult than reading a card that is in your hand. The lower 5% and 8% values are difficult to read due to the small amount of chemical present, which results in a very low density coloration. Think of a particular color that has had much more white added to it.
3) “Are AGM Humidity Indicator Cards reversible?”
The reversible ones (which is most of them) are, and the irreversible ones (the Maximum Humidity Indicator cards) are not. This is because Maximum Humidity Indicator cards need to warn of dangerous humidity levels, and therefore serve to indicate the need for desiccant replacement regardless of when they are checked.
4) “Are AGM Humidity Indicator Cards supplied with mounting hardware?”
Again, some are and some are not. In general, they are but for most of them, we shift the part number series by one when they are supplied without mounting hardware. So, a TA356-123P supplied without the nut and nut gasket is a TA357-123P.
5) “Can I mount a Humidity Indicator Plug in my bag?”
Yes, but you will need the mounting nut version to do this.
6) “What pressure can AGM Humidity Indicator Plugs withstand?”
Most units are rated to 10 psig (Pounds-per Square Inch Gage) in the pressure relief direction. This means the higher pressure is behind the window trying to push the window out of the container. The few vacuum direction tests we have run have shown that they TA356 series at least will also hold 10 psig in the vacuum relief direction.
7) “How tight should AGM Humidity Indicator Plugs be tightened?”
Both the flange and the mounting nut are 1-3/8” hex shapes. So any suitable hand tool that is capable of engaging a 1-3/8” hex will work. We recommend tightening the mounting nut to 30-40 in-lbs.