Main characteristics of our pipe connections and accessories

Our carbon steel range, applications, temperatures, pressures, final finishes,…

Description of screwed pipe connections

The NEXO FITTINGS’s product range is closely aligned with the market requirements and contains an extensive range of tube connectors made of carbon steel for metric tubes with outer diameters ranging from 4 to 42 mm in accordance with ISO 8434-1 / DIN 2353.

Doble-edge cutting ring screw connection

The use of a double-edge cutting ring offers advantages for most requirements.

When the union nut is tightened, first the front cutting edge and then the second edge cuts into the pipe when the union nut is tightened further. The cutting depth is limited by the cutting ring design.

At the same time, the ring has become wedged between the pipe and the connection piece. Positive locking of the components is attained in this case in both radial and axial directions.

Due to the profile shape and highly positive locking, forces applied to the connection are distributed over the entire length of the cone. This provides optimum protection against vibrations, alternating bending stress and fluctuations in pressure and temperature.

Before the union sut is tightened

Before the union sut is tightened

After the union nut is tightened

After the union nut is tightened

Flatered Tube Fiting

The flared connection provides a secure connection between connection pieces with bore hole shape W, DIN 3861 and 37º flared pipe ends. Assembly is easy and can be repeated as often as required. The tapered ring (with inserted O-rings) is inserted into the connection piece until the stop is felt. Due to the shape of the tapered ring, it is lightly wedged into the connection piece. When the union nut is tightened, the thrust collar presses against the preformed flare of the pipe, which in turn presses against the 37º taper of the tapered ring. Extremely reliable function is ensured by the metallic/elastomer seal. The entire screwed connection can withstand high loads and absorbs alternating bending moments and vibrations. Greater fluctuations in temperature do not influence function.

Welding cone Screw Connection

Screwed pipe connections employing welding cones is a logical supplement to the cutting ring screw connections. The same connection pieces with bore hole shape W, DIN 3861 and the corresponding union nuts are used, resulting in the same overall height. A reliable, tight connection between welding cone and connection piece is provided by the metallic seals and additional O-rings.

Such connections withstand extreme loads, including pressure impacts, vibrations and fluctuations in temperature.

Attention!
Due to the high temperatures used, the welding cone must be welded to the pipe before the O-ring is inserted.

Tapered Fittings /
Swivel Connections

Due to the connecting cone (24º) used, a standardized screwed connection using connection pieces (bore hole shape W acc. to DIN 3861) is possible. The O-ring additionally inserted in the cone results in a metallic/elastomer seal which provides excellent protection against leakage. This connection is resistant to pressure impacts and vibrations even under high loads. The dimensions are identical to screwed connections according to DIN 2353, ISO 8434. Either cutting ring, flared or welding cone screw connections are possible for pipe connection.

Criteria of Use

In order to choose the best suited screwed pipe connection, a few basic criteria must be taken into consideration. Depending on the given circumstances, specific requirements and expectations must be defined which the srewed connection must fulfil. In the selection of screwed connection types, maximum possible safety should be given priority.

The following criteria must be given special attention:

  • Max. resistance to pressure loads (in reference temperature dependent pressure reductions)
  • Temperature sensitivity of material (the tolerance of, for example, FPM lies between -25 and +200 ºC)
  • Dimensions
  • Service life, also in case of repeated assembly

Standards

Nexo Fittings standard tube connection program complies with DIN 2353 and ISO ISO 8434-1:

  • 24° cone connectors – DIN 2353 / ISO 8434-1: As standard supplied with double edge cutting ring (PDR).
  • 24° tube connection cutting rings – DIN 3861 / ISO 8434-1
  • 24° weld and swivel stud connectors – DIN 3865 / ISO 8434-1
  • 37° flared tube connectors – SAE 514 / ISO 8434-2: With or without O-ring seal on 37° taper
  • Metric and BSP stud ends: DIN 3852-1+2+11; ISO 1179-2+3; DIN ISO 6149-2+3
  • UN/UNF stud ends – SAE J 514; ISO 11926-2+3
  • Seals: FPM (e.g. Viton), on request PTFE (e.g. Teflon) and NBR.

Pressures

All pressures are in bar in acc. with DIN 2401. Temperatures, where stated are in °C. Pressure ratings are devided into nominal pressure (PN) and working pressure (PB). In this context the information provided in the chapters “Temperatures” and “Pressure reductions” should be taken into account.

Nominal pressure (carbon steel)

Nominal pressure is a common rounded value relating to static pressure (DIN 2401). Below table indicating 4-1 safety factor for relevant dimensions.

Temperatures

Nexo fittings are manufactured from rolled or forged steel protected with ZnNi coating (Zinc and nickel). The operating temperature for this material is between -20°C and +120°C

  • FPM (e.g. Viton®) -25°C to +200 °C
  • PTFE (e.g. Teflon®) -60°C to +200 °C
  • NBR (e.g. Perbunan®) -30°C to +100 °C

Pressure reductions

Pressure reductions should be made for Nexo Fittings where high operating temperatures are expected.