Pneumatic training

Keep in mind: The dew point has to be 15°C under the environmental temperature, otherwise the air will lose its ability to keep the water when being compressed.
Water in the valve / actuator would then freeze and lead to leakage or malfunction. In order to reach the dew point it is important to use an appropriate dryer. We recommend the use of an adsorption dryer. Check the dew point of the dryer which must be at least 15°C under the ambient temperature.

Example:

If we are declaring in our manual / catalogue that the dew point has to be 15° C below the current environment temperature signifies, that the relative humidity of the air-pressure has to be distinctly lower than 100%. As a result freezing as well as spread of condensate is avoided.

Don’t lubricate yourself! As a special lubrication is being used inside the HAFNER low temperature valves, the usage of other lubricants or oils might lead to malfunction. Please note that in most of our low temperature valves we use lip seal rings made from PUR (Polyurethane). Due to the geometry of these seals, the pressure connection is only possible at port 1. We can optionally use a different type of sealing system where pressure can be connected to other ports as well. For further information, please ask the manufacturer. Please note that below -40 °C, the valve leakage may increase to 10 cm3/minute. The HAFNER low temperature valves carry the suffix “TT” or “AIR TT” (optional sealing system):

• BR 311 701TT
• HV 511 701TT
• MH 510 701 GTT
• MNH 510 701TT

In particular, the choice of material for the sealing elements is crucial in low-temperature applications. PUR, silicones and low-temperature NBR are particularly suitable. But not only the material, but also the geometry of the seals plays a crucial role. The components of cold-resistant cylinders are usually stainless steel, anodized aluminium, sintered bronze or brass. Seals are made from polyurethane and NBR. Below -20 °C the NBR gasket hardens and loses its sealing ability, so the cylinder starts to leak. Cylinders used at high temperature are usually made with FKM seals, which however cannot be used below 0 °C. Our air preparation units are generally usable till -10 °C, so it is important to place them in a location that keeps them from getting any colder than this. It is important not to let the moisture collected in the filter cup freeze as the ice may crack the cup. It is therefore beneficial to use the automatic version. Some selected FRL-units are available for -40° C on request. It is important that not only our main components such as valves and cylinders withstand extreme weather, but the 'transmission elements' too. A type of pneumatic tube must be used which due to its material, can withstand minus degrees. The table below illustrates the temperature range for some tubes and fittings.

2. Warm environment

We face the challenge of a warm environment not only in high temperature production processes, but also in hot areas such as the Gulf region or applications with direct sun exposure. Especially the selection of the right rubber and plastic parts is essential for products in hot areas. Pneumatic valves are available with a wide variety of sealing materials such as NBR, PUR, FKM / FPM, EPDM and many more. Seals that perform well in hot environments and are most commonly used are FKM and FPM. These seals are identical in their raw material (fluorine-rubber / fluoroelastomer), the different designations are coming from different standards. While the FPM designation conforms to the DIN-ISO standard, the FKM seal conforms to the American ASTM standard. Remark: Many people use Viton® as a synonym for FKM / FPM, but it is a trademark by DuPont.

Solenoid valves for high temperature applications cause major challenges to manufacturers

Generally it is easier to find pure pneumatic components (no electric components on them) for hot environment than solenoid valves. Most of the solenoid system manufacturers limit their systems to 50°C/+60°C as the electrical actuating of the solenoid is causing additional heat. Hafner however offers their solenoid valves for up to +80°C (DC-versions only) due to a special material selection. Non-electrical valves are available for up to +120°C. In case a solenoid valve is required and the environment exceeds +80°C, an option might be to take the solenoid out of the hot area and only leave a pneumatic valve or actuator in the hot environment.

When building control cabinets, be careful with putting too many solenoid valves into a small cabinet. Solenoids also warm-up the cabinet as most of the power consumption is transformed into heat. Electronic components that are also put into the control cabinet tend to suffer substantially. Adding a ventilation system can help to reduce the heat. When making the specifications for the solenoid valves, the voltage and duty cycle is an important aspect. You can consider as a general rule that AC magnets tend to heat up more than DC magnets. A duty cycle or power cycle is the fraction of one period in which a signal or system is active.

The HAFNER high temperature valves carry the suffix “HT” (solenoid valves) or “VIT” (non-electrical valves):

• MH 311 015HT
• MNH 520 121HT
• P 510 701VIT
• HVR 520 701 VITVIT

3. Wet and polluted environment: the IP protection

When making the specifications for solenoid valves, special attention must be paid to dust and water infiltration. Different electrical components are available based on the requirements. Electrical equipment is therefore categorized in IP-classes. IP stands for International Protection Mark. With this, the protection against environmental influences has been indicated on a protective case (housing) that protects circuits of a technical equipment. The IP classification is described in the IEC 60529:1989 standard.

Some examples based on the IP-list:

• IP65:Fully protected against dust AND protected against low pressure water jets from all directions
• IP66:Fully protected against dust AND strong water jet and immersion in water
• IP67:Fully protected against dust AND immersion in water for a limited time
• IP68:Fully protected against dust AND can be used continuously 1-3 meters under water for 30 minutes (but individually specified by the manufacturer)
• IP69:Fully protected against dust AND can be used continuously for up to 1 hour under water up to 3 meters

Please note: A higher IP-class does not automatically that the “lower” IP-class is covered as well. Example: a valve which is rated for IP67 is not automatically rated for IP66.

IP-protection for Hafner solenoid valves:

HAFNER solenoid valves usually offer IP65 protection. Other protections can be offered as per the following table and on request.

For superior protection in very wet and dirty environments, we recommend the use of non-return valves in all exhaust ports. We offer exhaust protection fittings for the operator tube as well as for the valve exhaust ports:

Protection for the operator tube, type MSR:

Protection for the valve exhaust ports, type ESR: