Useful tips: When selecting instruments for design, how should the protection rating of the instrument enclosure be chosen?

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Industrial instruments are used in various environments, and the conditions in these environments differ. To be suitable for such diverse applications, industrial instruments must possess certain environmental protection capabilities, which are achieved through the design of their enclosures. The same instrument, when housed in different enclosures, will have varying levels of protection. The protection capability of industrial instruments is expressed by the \"instrument enclosure protection rating.\" So how is this protection rating defined? How is the protection rating of the instrument enclosure chosen in practical applications? 1. Protection rating of instrument enclosures. There are mainly two protection standards for industrial instruments in the world: This article was first published on the WeChat official account “Automation Academy”. One of them is the IEC (International Electrotechnical Commission) standard IEC60529, which is primarily used in Europe ； The other is NEMA (National Electrical Manufacturers Association) standard NEMA ICSI-110, which is primarily used in the United States and North America. In IEC standards, the protection rating of an instrument refers to its dust and water resistance at different levels. In the NEMA standard, in addition to dust and water resistance, explosion protection is also included. China’s **standard GB4208 “Enclosure Protection Level” is directly adopted from the IEC standard. In IEC standards and the national standard GB4208, the IP code is used to indicate the protection level of enclosures. The IP code consists of the identifier letter IP (International Protection), a first characteristic digit (indicating dust protection), a second characteristic digit (indicating water resistance; when no such digit is required, it is replaced by the letter X), optional additional letters, and optional supplementary letters. First characteristic digit: 0----No protection ； 1----Prevent solid foreign objects with a diameter of 50 mm or more ； 2----Prevent solid foreign objects with a diameter of 12.5 mm or more ； 3----Prevent solid foreign objects with a diameter of 2.5 mm or more ； 4----Prevent solid foreign objects with a diameter of 1.0 mm or more ； 5----It is not possible to completely prevent dust from entering, but the amount of dust that does get in must not affect the normal operation of the equipment, nor must it compromise safety ； 6----No dust entry. Second characteristic digit: 0----No protection ； 1----Dripping in the vertical direction should have no harmful effects ； 2----When the vertical surfaces of the enclosure are inclined within 15°, vertical dripping should have no harmful effects ； 3----No harmful effects occur when water is sprayed on each vertical surface within an angle of 60° (water resistance) ； 4----Spraying water in all directions toward the enclosure has no harmful effects (splash protection) ； 5----Spraying water in all directions toward the enclosure has no harmful effects (water resistance) ； 6----Forceful water spraying in all directions at the enclosure has no harmful effects (protected against forceful water spraying) ； 7----After being immersed in water at a specified pressure for a defined period of time, the amount of water entering the enclosure does not reach a harmful level (to prevent damage caused by short-term water intrusion) ； 8----Under the conditions agreed upon by both the manufacturer and the user (which should be more stringent than those specified in point 7), the amount of water entering the housing during continuous diving shall not reach a harmful level (to prevent the effects of continuous diving). Additional letters and supplementary letters are not commonly used on instruments; refer to the relevant standards. 2. How to select the protection rating for the instrument enclosure: When choosing the protection rating for an instrument’s enclosure, it is necessary to consider not only whether the instrument will be installed indoors or outdoors, but also the impact of environmental conditions during normal operation of the processing plant or in the event of an accident on the instrument. The following points are provided for your reference: (1) For instruments without electronic components, such as pressure gauges and bimetallic thermometers, an IP54 protection rating is generally suitable. (2) Instruments with electronic components, such as transmitters and electrical valve positioners, generally have a protection rating of at least IP55. (3) The protection rating for electric meters installed in outdoor meter wells should be IP68. To reduce the variety of specifications, most instrument manufacturers specify an IP65 protection rating for electric instruments; there are also models with IP66, IP67, and IP68 ratings. This article is original; please contact us for reproduction.