Protecting electromechanical interfaces against liquids is one of the basic requirements for industrial electronics in automation and process technology. However, the term ‚waterproof‘ is a matter of interpretation. Depending on the respective application, for electrical connection technology, different degrees of resistance to liquids are required.
Waterproof: the colloquial term suggests the total resistance of an object to the effects of humidity – for example in the form of fog or rain – and to immersion in liquids. However, it is already known from everyday experience that there is usually only relative protection, for example of a watch, a camera or a smartphone, whose specifications only permit submersion to a limited depth or a maximum hydrostatic pressure. For users of industrial electrical connectivity products, it is obvious to transfer this experience to the application scenarios for connectors, for example in process technology. Protection of the interfaces against liquids is an essential requirement here, both from a functional and a safety point of view.
In order to ensure the tightness of the overall electromechanical system, connectors are of particular importance in industrial electronics. On the one hand, they must be able to be plugged and unplugged several times; on the other hand, depending on the particular application, the connection must reliably prevent the ingress of liquid media when plugged in.
The degree of resistance required – and thus the correct interpretation of the attribute ‘waterproof’ – is inseparably linked to the circumstances of the application in question: While connectors are not in direct contact with humidity in many automation tasks, there are special applications where they are exposed to splash water or even have to withstand temporary submersion. Particularly in hygienically demanding environments, connectors may be treated under high pressure for cleaning purposes. In such cases, special design considerations are essential to ensure reliable signal and power transmission.
Standardized labelling: protection degree and IP code
The degree of resistance to humidity and liquids is indicated in the product data sheets of the connector manufacturers. The relevant technical specification refers to the so-called protection degree; it determines under which environmental influences – physical touch as well as ingress of particles and water – the respective connector can be used. In accordance with the DIN EN 60529 and ISO 20653 standards, the protection degree is specified by means of an IP code (International Protection), which for connectors is generally valid only when these are mated. The above examples therefore correspond to the protection degrees IP67 – protection against temporary immersion – and IP68/69K – protection against permanent immersion or exposure to high pressure. Since the standards do not define criteria such as ‘temporary’ or ‘permanent’ in a clear and mandatory manner, it is advisable for manufacturers to provide more precise information in practice.
In practice, insufficient knowledge of DIN EN 60529 or ISO 20653 often results in the misleading assumption a high number in the IP code necessarily means better protection. It is therefore important to know that the first digit of the code refers to the ingress of solid particles, such as dust, while the second digit indicates protection against humidity and water. Thus, a product rated IP64 cannot be considered ‘better protected‘ in general compared to an IP55 product. The former may be more exposed to particles, i.e. it is dustproof. However, it can only withstand splashing water, while the second can be exposed to jet water from any angle.
The two digits for particles and humidity/water can be followed by code letters in the third and fourth positions to indicate the protection degree more precisely. For example, a K (as in IP69K) stands for road vehicle equipment; a B for access to hazardous active parts with a finger.
It is important to emphasize that the IP protection degree refers to the protection of equipment and its components only. It does not make any statement about the protection of persons who interact with this equipment. Measures for the safety of users are defined in the so-called protection class, which is not the subject of this article.
Waterproof in an industrial context
In addition to electrical parameters such as rated current and voltage, surge voltage or contact resistance, installation-relevant parameters such as integration density and degree of miniaturization – and consequently the design of a connector – are general selection criteria. Beyond this, however, it is necessary to evaluate the special features of the respective application environment. Is the interface exposed to mechanical loads such as shocks or vibrations? Are precautions to be taken against the influences of adjacent high-frequency electronic assemblies, against the risk of fire or explosion? Or does a connection that has to be mated and unmated frequently require special design considerations in order to endure many mating cycles? The answers to these and similar questions lead the user to product features such as locking system, electromagnetic shielding and contact materials, which necessarily influence the purchase decision.
The fact that connectors must – in an initially undefined manner – withstand the ingress of particles and humidity or liquids is a standard requirement in the industry. But as explained above, the necessary protection degree depends on the details of the application. As these range from interfaces in measurement and control in factory automation, through the Food & Beverage industry, to clinical use of medical instrumentation, the requirements for ‘waterproof’ connectors can vary considerably. Especially in the latter two areas, the products are exposed to a particular humidity load resulting from the cleaning and sterilization processes required here.
Product examples featuring IP67 and IP68/69K
All M12 connectors from binder are resistant to moisture and water in accordance with IP67 standards, and many are also resistant to IP68/69K. Corrosion-resistant variants are equipped with stainless-steel or plastic threaded rings. While IP67 ensures application safety in occasional humidity – without higher requirements – the more resistant products, depending on the protection degree and material, can also withstand weather conditions in outdoor use as well as immersion in greater depths, high-pressure water jets and aggressive cleaning agents.
The IP67 portfolio also includes M12 plugs and sockets that can be assembled. Connection technology with IP67 protection, such as the binder NCC (Not Connected Closed) series 770, are recommended, for example, for use in handheld terminals, medical equipment and LED lighting assemblies. Equipped with a bayonet lock and designed for more than 5,000 mating cycles, these products are characterized by a special design feature. A spring-loaded plastic cover inside their housing encloses the contacts – when unmated – so that they are safe from accidental touch. They are thus protected against particles and splash water, and are also protected against mechanical impact from the outside.
The so-called subminiature and miniature series 620 and 720 – when mated – also meet the IP67 criteria . For this purpose, they are equipped with an O-ring on the female end as well as with a seal in the clamping area. Despite their sensitive snap-in elements, the connectors withstand more than 1,000 mating cycles. They are also suitable for medical equipment; other possible applications include metrology equipment, industrial lighting or the seat heaters in sports stadiums.
All molded cable connectors of the 763 series featuring signal and sensor cables as well as threaded rings made of media-resistant and temperature-resistant plastic are waterproof to protection degree IP68 when mated. Protection to IP68/IP69K is achieved by the outdoor connectors with bayonet quick locking of the HEC series . Application examples include tunnel lighting for very humid environments, underwater metering probes and supply lines for submersible pumps. HEC connectors are also widely used in agricultural machinery and in portable handheld welders. The outdoor and stainless-steel versions of the 713 series also comply with protection degree IP68/69K. The outdoor versions are made of plastic suitable for this purpose and are equipped with protective caps that preserve the signal connectors from the effects of weather in outdoor use. The stainless steel products are particularly resistant to aggressive agents.
Particular Food & Beverage versions of the binder 763 series and the stainless steel variants of the 713 series are protected to IP69K. The M12 connectors are suitable, for example, to connect sensors that monitor process parameters in bottling plants. In general, they are intended to be installed in machines and systems that are cleaned with high-pressure cleaners and aggressive cleaning agents.
Conclusion: application determines the degree of protection
Protecting electromechanical interfaces against the effects of liquids is a fundamental requirement in industry. The degree of resistance required always depends on the specific environmental conditions of the respective application. In the product documentation of the component manufacturers, it is represented by the protection degrees or IP codes. binder offers connection technology in accordance with IP40 to IP68/69K, with a large part of the connector portfolio meeting the requirements of IP67 and above. The binder products are thus recommended, for example, for use in the fields of automation, building, agricultural, food and medical equipment technology.
Waterproof connectivity solutions from binder: special features (INFO BOX)
The circular connector specialist binder from Neckarsulm, Germany, offers waterproof connectors for harsh environmental conditions that have been developed for protection degrees IP67 to IP69K. UV- and temperature-resistant material is used in selected products, and some of the connection technology is suitable for demanding hygiene requirements. In detail, the design has been optimized to prevent dirt deposits on the housings; IP69K connectors can be cleaned with high-pressure jets, special stainless steel variants are resistant to aggressive cleaning agents, and overmolded connectors for the Food & Beverage market segment are also certified according to the specifications of the test service provider Ecolab. A selection of different locking systems and materials is available for various application scenarios – such as M12 threaded rings made of plastic or stainless steel, or bayonet or snap-in mechanisms optimized for applications that require fast and frequent mating. The balance of function and design in product development is worth highlighting. Thanks to special coloring, the connectors meet typical market design specifications, for example for the Food & Beverage segment or for medical technology.