Hydraulic Compression Fittings

DIN Type Compression Fittings are made in accordance with DIN 2353/ISO 8434-1 standards. They are also known as DIN Compression Fittings, Bite Type Fittings or Single Ferrule Fittings, and commonly used to connect tubes and hydraulic lines. The use of the proper fittings increases the efficiency of the equipment and creates a smooth flow through the system. Compression fittings adhere to the DIN2353 standards established by the Deutsches Institut für Normung, ensuring product quality and compatibility with other goods. Moreover, they are also often used for hydraulic and lubrication oil, fresh water and sanitary applications. A DIN fitting consists of three components, namely fitting body, nut, and sleeve. The fittings are made in Korea and Germany with the brand Eaton and HSME respectively.

Compression fittings are generally made with three materials: Brass, Steel and Stainless Steel. These materials are utilized in systems that are compatible with one another. To protect fittings from corrosion, an additional process is carried out. The process is passivation for stainless steel, white zinc plating for steel, and acid cleaning for brass. Moreover, there are several differences between the materials used for compression fittings.

• Brass Fittings: Brass is one of the most common materials used in the production of pipes and tubes. It has grown in popularity due to its topical relevance and dynamic traits. The strengths of brass fittings are durability and high corrosion resistance. Brass fittings can withstand high pressures and maintain their structure for a long time. Brass is a metal made up of copper, zinc, and other metals which makes the material corrosion resistant and ideal for the production of a variety of tools, such as compression single ferrule fittings.
• Carbon Steel Fittings: Iron, carbon, manganese, copper, silicon, sulfur, phosphorus, molybdenum, nickel, chromium, and vanadium are all contained in carbon steel. Carbon steel fittings have the high strength quality which is durability due to its chemical composition. Besides, they are resistant to extreme weather conditions and corrosion.
• Stainless Steel Fittings: Stainless steel fittings encompass selenium, aluminium, silicon, nickel, molybdenum, chromium, sulfur, nitrogen, copper and selenium. They are resistant to corrosion and chemical damage as a minimum of 11% chromium is present in stainless steel. Stainless steel fittings are readily accessible in the market.

Compression fittings are available in three series, which is LL series, L series and S series. The available sizes depend on tube outer dimensions (OD) which ranges from 4MM OD to 42MM OD.

Pressure rating varies for each series. For LL series, the maximum working pressure is 100 Bars. For L series, the highest pressure rating is 315 Bars, and for S series, the highest pressure rating is up to 630 Bars.  However, take note that the pressure rating of the fittings is also affected by the sizes. In general, larger sizes will have lower working pressure.

You must be sufficiently prepared for the process before connecting fittings to tubes or pipes. More importantly, the components that will be connected must be easily available and properly selected. To prepare your components, there are three steps as following:

Step 1: Tubes

Before purchasing tubes, you should be aware of the significance of material compatibility. Choose the tubes based on the working pressure, chemical composition, size, temperature range, and etc.

Step 2: Fittings

Choose your desired fitting configuration. Fittings are critical components that determine the flow direction based on their shape. You can use a union coupling, a tee, a 90D, an elbow, or any other form of fitting.

Step 3: Tools

When selecting tools, kindly consider the outer diameter of the tubes you'll be purchasing. The appropriate tools will make the installation procedure run quickly and smoothly.

These fittings come in a variety of configurations and hence, they need to be adaptable to a variety of conditions. Straight fittings are the most popular that are used to join straight pipes and hoses. Moreover, there are other configurations which are available for more delicate and specific situations. For instance, tees, crosses, caps, plugs and nuts.

For more information about DIN fittings, please refer to en.wikipedia.org/wiki/Cutting_ring_fitting

Lubrication of threads of union nut

Before assembling DIN fittings with tubes, we need to put attention on some details. The material of fittings and tubes must be similar, except for copper tubes, which are used together with brass fittings. Saw machines are recommended for sawing off tubes. After sawing off the tube, do use deburring tools to lightly deburr the inner and outer diameter of the tube ends.

We also need to lubricate the threads of the nut and the body of the fittings, the cutting ring and the 24˚ cone using a suitable lubricant like anti-bloc fett. Please note that normal grease is not recommended for lubrication.

To assemble the fitting with the tube, first, place the pre-oiled nut and cutting ring over the tube in the right direction. Then, insert the tube into the fitting body, up to fitting stopper with nut and cutting ring. Then, hand-tighten the nut, and the wrench tighten 1 1/4 turns, by holding the fitting body with a second wrench, for final assembly. Please note that we should turn the nut instead of the fitting body. After that, check the penetration of the cutting ring.

The pressures specified are in accordance with DIN 2401 part 1 draft. The pressure has a safety factor of 4 times according to DIN 3859 standards.

Compression Fittings temperature ratings vary in accordance to the body material as per below:

Body Material Temperature Rating:

When combing seal material, the temperature rating of seal may become the limiting factor on the fitting's temperature rating. Kindly refer to the temperature rating below:

Elastomer's Temperature Rating:

There are reductions in the nominal pressure (PN) caused by the temperature of the fluid medium or surroundings. Please refer to the table below:

Pressure Reduction in Temperature: