DIN fittings are the most common metric hydraulic fitting style in Europe, typically specified by DIN 2353, DIN EN 3850 and ISO 8434-1 standards. DIN stands for "Deutsches Institut für Normung", which is the German Institute for Standardization. They are commonly used in oil & gas, construction and industrial hydraulic and pneumatic applications. Sizes range from 4mm to 42mm and are typically made of carbon steel or stainless steel. However, brass and some exotic materials can be used for specific applications, and they are often made by following different manufacturing standards.
Some versions of the German DIN Metric 24° Bite Type incorporate a captured elastomeric seal and metric DIN 20078 series hose fittings, DIN 7631 60° cone, 74234 45° cone and DIN 74233 and are the leading European threads styles for many applications.
The DIN standards are used in connections such as:
- Alternating valves which allow the flow to pass from either inlet 1 or 2 to the outlet port while shutting off the inlet port that’s not in use
- Check Valves
- Compression and hydraulic hose fittings
- Swivel and Banjo fittings
Material
DIN 2353 metric stainless steel 1.4571 (316Ti) is the primary material for excellent corrosion resistance. Stainless steel 316Ti and sometimes other exotic materials are used in conditions with high acidity and elevated salt levels, ch as offshore oil rigs. These materials provide a long service life, reducing the total cost of ownership and leading to lower maintenance costs.
Stainless steel 1.4571 (316Ti) DIN 2353 fittings are ideal for harsh environments, along with Monel and Inconel, and used in extreme conditions such as the presence of:
- Salt spray or saltwater submersion
- Acidic atmosphere
- Extreme heat or cold
- Physical shock
- Vibration
Carbon steel is also applicable in many common applications and provides very good corrosion resistance. For these applications, a specific zinc-nickel plating is applied that exceeds U.S. and international corrosion resistance standards-- such as VDMA 24576 class K5. When tested to 1000 hours of exposure to salt spray zinc-nickel plated carbon steel, they should not show any traces of red or white rust, allowing them to present:
- Good paintability
- High levels of abrasion protection
- Very good temperature stability
- Low corrosion when in contact with stainless steels or aluminum
Applications and Industries
As with other hydraulic fitting thread styles, DIN metric bite-type fittings are widely used in industries and fluid power applications, such as:
- Agricultural equipment
- Construction equipment
- Industrial machines
- Oil & gas
- Drilling platforms
- Hydropower plants
- Railway technology
- Recycling equipment
- Shipbuilding
- Machine tools
- Wind turbines
- Material handling
- Mining equipment and hydraulic supports holding up the mine roof
DIN 2353 Pressure Series
DIN 2353 fittings are available in three different pressure series classifications:
- LL for very light pressure applications
- L for light pressure
- S series used in high pressure systems
Each is identified by measuring the pitch, thread size and tube OD and referring to a pressure guide to confirm classification.
Conclusion
DIN are the worldwide standardized metric thread, and is the most widely used fitting in Europe, surpassing any imperial (inch) thread style.
Many OEMs are increasingly choosing DIN metric (along with O-ring face seal) due to their ability to withstand higher pressure ratings many of today’s applications require. Even the popular JIC fitting is not rated for many of these pressures, particularly applications that experience high vibration.
In fact, with their increased global popularity, many U.S. OEMs are incorporating DIN fittings, particularly in equipment being marketed in Europe. This, along with the rise in equipment being imported from Europe into the Americas, is causing DIN metric fittings to become more common in U.S. MRO applications, thus increasing their presence in “maintenance bins”.
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