Fittings: international differences and standards

Stucchi’s innovative flat-face quick coupling design makes it possible to connect and disconnect hydraulic lines easily and quickly, without the need to use tools while ensuring a leak-free connection, without pressure drops or risks to the operators.

However, these advantages apply only if the male and female are properly fixed at the ends of the pipe: it is clear that if leaks occur at those points of connection, the technical excellence of the quick coupling will not be adequately taken advantage of.

In choosing the quick couplings, it is therefore essential to evaluate also the most suitable fittings.

Fittings consist of two elements:

  • a threaded section, which makes it possible to connect the coupler and the pipe;
  • a sealing system, which ensures that there are no leaks.

In turn, the sealing system can employ one of these three different technologies:

  • with seal;
  • with threaded cone and hydraulic tape;
  • with interlocking between two parts with specific geometries.

The fittings are divided according to different rules and classifications that vary from country to country: only in the US there are several standards, which also take into account the sealing technology used (such as NPT, National Pipe Taper fitting for hydraulic tape, or ORFS, or Ring Face Seal, for fitting with seals); in the European Union, ISO prevails in order to provide a more general framework, even if Germany and Great Britain have their own specific regulations.

In addition to indicating regional differences in the manufacturing process, these different classifications provide information about the applications for which the type of fitting is predominant (such as SAE for automotive use).

The most common types of fittings are:

  • NPT, or the U.S. National Pipe Taper, which uses an insulating tape wrapped around the conical thread to couple the male and female taking advantage of the principle of roundness;
  • BSP, or the British Standard Pipe, which uses a threaded section with a constant size (BSPP) or a variable one (BSPT);
  • SAE, the U.S. Society of Automotive Engineers, which uses different types of couplings, according to the type of application in the automotive sector.

Understanding the reference standard used is of critical importance, because it is on that basis one determines the compatibility of the connection with the pipe on which the quick coupling will be installed: it is necessary to make sure that the diameter of the point of connection (indicated on the technical data sheet) and the type of threading are the same.

Otherwise, the joint will be inadequate, causing leaks, pressure drops and potential risks to personnel, or it will not be possible to fully connect the pipe and the quick coupling.

Stucchi offers a wide variety of solutions for many sectors that use pressure circuits, the result of 60 years of experience in this field: our quick couplings are modular and equipped with the main standards required by the market, as well as being available in many sizes.

Contact us now to learn more.

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