Moisture and liquid indicators MI..SMP / MI..SMPI series

The indicators are classified as “Pressure accessories” in the sense of the PED Directive 2014/68/EU, Article 2, paragraph 5 and are subject of Article 4, paragraph 1, letter (c), of the same Directive. All the product range is suitable for use with refrigerant R744 (CO2), classified in Article 13, paragraph 1, letter (b), of PED Directive 2014/68/EU as part of Group 2, therefore not toxic, not inflammable and not explosive fluid and indicated in A1 Group of Annex E of standard EN 378-1.

The function of humidity indicators is to verify the actual situation of flow and the presence of moisture in the system.


The moisture indicators are characterized by an element sensitive to moisture which changes colour from green to yellow depending on the concentration of moisture in the system and is made by embedding a spyglass directly into the body of hot forged brass EN 12420 – CW617N. This forms a unique compact structure that minimizes the junctions between components, followed by removing possible leakage of refrigerant. To obtain a perfect sealing of glass in all indicators is used a modified Teflon gasket.

  • MI..SMP series: The solder connections are made of copper EN 12735-1 – Cu-DHP.
  • MI..SMPI series: The solder connections are made in stainless steel AISI 304.


During the first start, the colour of the element sensitive to moisture can be yellow, not only because of atmospheric moisture with which the indicator has come into contact but also for the presence of moisture in the circuit. When the moisture content of the refrigerant is normalized through the dehydrator filter, the colour of the element becomes green. The brazing of the indicators to the system shall be done with a low melting point alloy. During this process do not point the flame directly towards the body keeping it cooled in order to avoid compromising the seal of the gaskets.