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The fitting (from English , here: 'fitting', 'fitting', 'connecting piece', 'accessories', 'accessory'; German plural: fittings ) is a generic term for precisely fitting and often standardized connecting and accessory parts in assembly technology . In larger dimensions or when the accuracy of fit is less demanding, they are also referred to as fittings .

Fittings are used in particular to make pipe connections.


The connection piece in pipeline construction, now understood as a fitting, was forged until the invention of malleable cast iron . In Europe, the technique of malleable cast iron for fittings - the so-called malleable cast iron fitting - was introduced by Georg Fischer II in 1864 . The Polytechnisches Journal ruled as early as 1860: "For a little longer than a year, the Fischer establishment in Schaffhausen, which is well-known for its excellent steel products throughout the technical world, has also started the manufacture of hammerable and weldable castings." The product caught on right from the start because this invention was superior in terms of both quality and price.

In the beginning, these fittings were mainly used for gas pipes with dimensions of ¼ to 2 inches , but in the first few years they were also used for water and steam pipes. The term fitting appears for the first time in the product catalogs of Georg Fischer AG (GF) in the 1870s .

Plastic as a material for fittings emerged in the mid-1950s to connect the plastic pipes that had come onto the market at the beginning of this decade. The GF first attempts were made in 1953 at the Schaffhausen plant, in 1955 PVC fittings could be presented at a trade fair and from 1957 these went into series production.

Pipe fittings

Fittings made of copper for capillary soldered connections
PVC fittings for push-in and flange connections

Fittings or molded parts are used in pipeline systems to connect straight and bent pipe sections to one another and to pipe fittings ( valves , cleaning openings, seals , thermometers , pressure gauges , etc.).

The connection can be made by screwing , flange , soldering , clamping, crimping, plug, press or adhesive connection. The term is used everywhere in pipeline planning and also in building services .

Fittings are available for various nominal widths and nominal pressures .

Due to the time savings and simpler application, the use of fittings in domestic installation technology has almost replaced the manual bending, widening, necking and fitting-free hard soldering of copper or welding of so-called black steel pipes.


For the production of complex, branched pipeline networks , connecting pieces of different types and dimensions are offered, which, depending on the type, fulfill the following functions, for example:

  • Straight connections with long or short sleeves , double nipples and couplings
  • Change of direction through angles (with a small radius) or arcs (with a larger radius)
  • Diameter change through reducers (reducers)
  • Branches through T-pieces (3-armed) and crossings (4-armed)
  • Connection to built-in parts, for example by flanges or screw connections ( nipples )
  • Connection of different pipe materials , to avoid corrosion elements, insulating pieces should be used when connecting different metals or combination rules should be observed. For example, brass or better gunmetal fittings are used between steel and copper pipes .
  • Separation points and cleaning and Inpektionsöffnungen for assembly and maintenance, eg. B. by screw connections

Use of the terms in chemical plant construction

When planning chemical plants, fittings are also used in the pipelines. This is the generic term for the route functions in the lines mentioned above, but it is more narrowly defined. There are different groups formed for fitting (engl. Fittings ), joints ( joints u. Unions ), flanges ( flanges ), tube ( tube, pipe ) and valves ( valves ). In German there is still the generic term fittings for all control and monitoring parts built into pipelines (valves (manual or motorized), sight glasses, sieves, non-return valves, etc., but no measuring and regulating equipment). The collective term fitting is not known in English and everything is slammed shut . In the English partner page on fittings, valves are listed under fittings , but that is an incorrect integration. It does not correspond to the international practice of plant engineering.

Most of the named parts are defined in terms of their dimensions by standards (EN, ANSI, GHOST ...) and can therefore be purchased from a wide variety of manufacturers, provided the appropriate material is used. As fittings only special parts with fitting character are called, which are produced as a single construction and -anfertigung because their function can not be covered by standard parts.


galvanized 90 ° inner / inner screw fitting made of malleable cast iron; on the left bead can be seen marks that when screwing the fitting with a pipe wrench emerged

There are fittings made of stainless steel ("stainless steel"), malleable cast iron , brass , gunmetal , copper , steel and plastics .

Fittings made of plastic, brass, gunmetal or white malleable cast iron are used for screw connections. Malleable cast iron fittings are subjected to a special heat treatment in order to increase the toughness of the originally brittle cast material.


Change of direction, offset and adjustment of pipe center distances by means of pipe bends

The shape and dimensions of pipe fittings are regulated by standards ( DIN , EN , ANSI ).

The diameter of the flow openings are usually given as nominal widths (DN, NB (nominal bore) or NPS (nominal pipe size) ).

All fittings that are used for water and gas installations, like pipes, should be marked with the letter combination “ DVGW ”.

New joining techniques

Traditional pipes by screwing, soldering and welding connected . Modern techniques are plugging, clamping, pressing, gluing and welding plastic pipes. In contrast to welded and soldered connections, these can also be used in areas where there is a risk of fire and explosion. In the case of plug, clamp and press connections, the connection is usually sealed using a sealing ring ( O-ring ) that is inserted into a groove in the fitting. A little more space is required to apply the press jaws when creating a press connection than to turn the screw fittings on threaded pipes . The devices for heating element socket and butt welding of plastic pipes also require a certain working space. In contrast, soldering, gluing, plug-in and clamping connections, as well as heating element welds, can generally also be carried out under cramped conditions.

Copper solder fittings

Fittings for capillary soldering of copper pipes are standardized according to DIN EN 1254 (formerly DIN 2856). The fittings are identified by a type number.

Type series 5000: solder fittings made of copper according to DIN EN 1254   
number image designation
5001A Cu fitting type 5001A (15 mm, 90 degrees, bend, outside + inside) .jpeg 90 ° elbow with internal and external soldering end
5002A 1-1111 CU-solderfitting-type 5002-18.jpg 90 ° elbow with internal soldering ends
5002 L Long elbow 90 ° with internal soldering ends
5040 1-1111 CU-solderfitting-type 5040.jpg 45 ° elbow with internal and external soldering end
5041 1-1111 CU-solderfitting-type 5041.jpg 45 ° elbow with internal soldering ends
5060 Double bend 180 ° with internal soldering ends
5085 Skip bend with inner soldering ends
5085 Skip bend with inner soldering ends
5086 Skip bend with inner and outer soldering ends
5090 90 ° angle with internal soldering ends
5090R Reduced angle 90 ° with internal soldering ends
5092 90 ° angle with internal and external soldering ends
5130 1-1111 T-piece copper type 5130.jpg T-piece with internal soldering ends
5130 R Reduced T-piece with internal soldering ends
5180 R Cross piece with inner soldering ends
5240 1-1111 CU-solderfitting-type 5253-28x15.jpg Reducing sleeve with internal soldering ends
5240G Half screw connection with inner soldering end, union nut, flat sealing
5243 Reducing nipple with internal and external soldering ends
5243G Reducing nipple with internal soldering end and external thread
5246G Transition socket nipple with internal thread and external soldering end
5270 1-1111 CU-solderfitting-type 5270.jpg Sleeve with pipe stop and inner soldering ends
5270 G Transition sleeve with internal soldering end and internal thread
5270S Sliding sleeve without pipe stop with inner soldered ends
5280G Double nipple with inside and outside soldering end
5290 Plug
5301 1-1111 CU-solderfitting-type 5301.jpg Cap with inner soldering end
5340 Screw connection, conical (metallic) sealing
5340G Screw connection, on the one hand internal thread, conical (metallic) sealing
5340G Screw connection, on the one hand external thread, conical (metallic) sealing
5359G Half screw connection, flat sealing with union nut
5870 Expansion arc

Push-in fittings

HT pipe with sleeves for plug-in connection

Plug connections are used for sewage pipes made of ceramics, concrete, as well as HT and KG pipes .

Push-in fittings for copper and steel pipes are also available, which can be used without the use of tools and, depending on the system, can be loosened again with special pliers. The tensile strength connection is usually made by a thin, laminated ring made of spring steel . The sharp-edged lamellar wings of the ring allow the tube to be inserted and, when tensile forces occur, claw like barbs on the outside of the tube. Due to the high price, these pressure-resistant push-in fittings are only used in special cases. A well-known brand name is Tectite .

Press fittings

T-pieces for multi-layer composite pipe
Built-in copper press fitting with 90 ° bend in 15mm pipe

Pressing is now the predominant connection technology for heating and sanitary installations in the professional sector.

Press fittings are pressed onto copper , steel or multi-layer composite pipes with hand-operated pressing tongs or electric pressing machines . These fittings are still relatively expensive; advantages result in particular from the rapid assembly. Pressing tools can often be rented from hardware stores and specialist companies.

Press tools for the various systems are often not compatible with one another. They are also known as press jaws or press tongs. Alternatively, press rings with (joint) clamping jaws are used. For larger pipe diameters there are press chains with clamping jaws or press slings. Special pressing tools are sometimes required for pressing gas installations. The different embossing patterns of the tools are called contours .


  • faster processing
  • no risk of fire or smoldering of the surroundings due to soldering and welding work
  • no use of heavy gas cylinders or welding equipment
  • clean appearance without rework


  • The fittings are comparatively expensive
  • It is difficult or impossible to bring the pressing tool towards narrow spaces
  • After being plugged together, the connections are often tight even without pressing the sleeves. Inadvertently unpressed connection points slip apart after a while, which can have catastrophic consequences, especially with gas and water pipes, if the leak is not noticed immediately. Most manufacturers therefore now equip their press fittings with O-rings, whose specially shaped constrictions allow the medium carried in the pipeline to escape in a controlled manner as long as the connections have not been pressed ("unpressed, leaking").
  • The manufacturers usually give a 5-year guarantee on their products. Since there is no long-term experience with the behavior of the material of the sealing rings, it is not known whether the durability of the long-established pipe connections can be achieved. The tightness should therefore be checked at certain intervals (problematic with flush-mounted installation).

The suitability of the pressing tools is generally determined by the manufacturers of the pressing tools themselves. In addition, some system manufacturers or providers or independent technical test centers confirm the suitability. The test is carried out in accordance with DVGW rules W 534 and VP 614 by an approved testing institute.

List of available press fittings   
End of connection Press end External thread inner thread Valve connection Flange end Clasp
Bend 90 ° I / I

Elbow 90 ° I / A Elbow 45 ° I / I Elbow 45 ° I / A Press socket I / I Sliding socket I / I T-piece (reduced) Reducer through connection Press socket jump bend

Transition angle 90 ° AG

T-piece AG Transition piece AG Through screw connection AG Male end AG

Transition angle 90 ° IG

T-piece IG transition socket IG through screw connection IG jump bend

3-part press end Transition flange Sealing plug

Press fittings for copper, stainless steel and carbon steel

Press fittings for pressing metal pipes have molded socket ends with a clearly visible bead in which an O-ring is inserted from the inside to seal the annular gap. They are pressed in circumference with radial presses in such a way that, on the one hand, the O-ring is compressed around the circumference and, on the other hand, a form fit is produced through the joint deformation of the pipe and socket of the fitting . Usually, the originally circular cross-section is converted into a hexagonal shape.

When using ordinary O-rings, the pipe connections are usually tight after they have been put together, even without pressing. Unpressed connection points are therefore not noticed during the mandatory pressure test. However, since unpressed connections often slip apart after a while in regular operation, devastating water damage was more common. Most manufacturers now offer specially shaped O-rings that ensure that the connections are “leaky when not pressed” and can thus be identified in good time. Viega and Nussbaum use the designation SC-Contur or SC-Contour for unpressed, leaky press connections , Seppelfricke and VSH use the term LBP or 'Leak Before Pressed' , Eurotubi '' leak path ''.

In addition, some manufacturers provide the fittings with colored plastic rings, which loosen when pressed. This makes it easy to check whether the pressing has already been carried out.

The durability of the O-ring is critical to the life of the system.

  • For heating, cooling and drinking water installations as well as sprinkler systems, black colored EPDM sealing rings are usually used.

In connection with carbon steel and stainless steel fittings, operating temperatures of −35 ° C to 120 ° C or 135 ° C and briefly up to 150 ° C are provided at a pressure of up to 16 bar. With copper fittings, temperatures between −20 ° C and 110 ° C and briefly 130 ° C are provided for the same pressure. Higher pressures and vacuum down to −0.85 bar are possible. The volume fraction of antifreeze is occasionally limited to 50%.

  • For solar systems with operating temperatures of −20 ° C to 180 ° C or 200 ° C and briefly up to 230 ° C, sealing rings made of FKM ( Viton ) or FPM , which are often green ( VSH / Seppelfricke ) or blue, are used. An operating pressure of 16 bar is provided for stainless steel pipes and press fittings, and 10 bar for semi-hard and hard copper pipes. Sealing rings made of FPM are generally not allowed to be used for drinking water installations.
  • Sealing rings made of FKM , which are often green ( VSH / Seppelfricke ) or blue, are used to transport hydrocarbons (e.g. oils) .
  • For gas installations with copper fittings, yellow-colored NBR sealing rings are used, which can be used up to 5 bar overpressure and operating temperatures from −20 ° C to 70 ° C. In connection with stainless steel fittings, yellow-colored sealing rings made of HNBR are used, which should also guarantee tightness at a temperature of 650 ° C for 30 minutes in the event of fire.
  • For compressed air with operating temperatures of −20 ° C to 85 ° C, EPDM sealing rings up to a water content of 7800 mg / m³ (class 5, ISO 8573 part 1) and oil content of 25 mg / m³ (class 5, ISO 8573 part 1) used. If the water or oil content is higher, sealing rings made of FKM ( Viton ) are used.
    For carbon steel pipes, the water content may be 880 mg / m³ (class 3, ISO 8573 part 1) and the oil content 25 mg / m³ (class 5, ISO 8573 part 1). Above that, pipes made of copper or stainless steel should be used.
  • For steam up to a pressure of 9 bar and operating temperatures from −20 ° C to 175 ° C and briefly up to 190 ° C, special sealing rings made of FKM are used. B. are colored gray ( VSH / Seppelfricke ).
  • In order not to damage the O-ring when inserting the pipe or the spigot end of a fitting, it is occasionally recommended to wet it.

In the case of fittings with an M-contour or M-profile , the bead is located at the outer end of the fitting. The bead is compressed on all sides during pressing. This deforms the inserted O-ring and rests against the inserted pipe. In order to achieve a torsion-proof and tensile connection ( toothing ) between the fitting and the pipe, the sleeve is embossed in several places next to the bead.

In the case of fittings with a V-contour or V-profile , the bead is located in front of the end of the fitting. The socket is embossed by the pressing tool in several places in front of and behind the bead and thus pressed with the pipe.

Press systems for pressing with M-contour :

  • Geberit Mapress press fittings
  • Inoxpress
  • GdPress
  • X-Press
  • VSH (Seppelfricke) Xpress - Press connectors made of copper, carbon steel and stainless steel for pipes with an outside diameter of 76.1 - 108 mm
  • Eurotubi manufactures press fittings from [1.4404] (AISI 316L) steel
  • Sanha fittings are predominantly approved for pressing with both M and V contours .
  • Pressing devices and tools are manufactured by Novopress , Rems , Roller , Ridgid and Rothenberger , among others .

Press systems for pressing with V-contour :

  • Viega uses the term SC-Contur for fittings that are "leaky when not pressed," but pressing is carried out with tools with a V-contour . The mounting of the tools in the press machine was formerly known as "SOM". "PT2" and "Picco" recordings are now being used. Older Nussbaum and Novopress machines cannot be used with PT2 tools. Picco recordings only fit in Picco machines.
  • Profipress offers press connectors made of copper, gunmetal or silicon bronze, tested according to DVGW worksheet W 534
  • VSH (Seppelfricke) Sudopress manufactures press connectors made of copper, carbon steel and stainless steel for pipes with an outer diameter of 12 - 54 mm
  • Connex Bänninger (IBP Group) manufactures the> B <press system and accordingly designates the contour as the B contour and the tool holder as KSB4.
  • Eurotubi
  • Sanha press fittings are generally approved for pressing with M and V contours .
  • Rothenberger manufactures pressing devices and also names pressing tools for pressing fittings with a V contour as SV contour tools
  • Pressing devices and tools are manufactured by Klauke, Novopress, Nussbaum, Ridgid, Rems, Roller and Rothenberger, among others.

In the case of drinking water installations that are not exposed to major temperature differences and where the maximum permissible pressure is not used, no damage is often to be expected if connections with the wrong contour are pressed. If the wrong press contour is used, worn press jaws and press tools that are too weak or poorly maintained, the maximum possible pressure and the pull-out strength of the connections are generally reduced. The torsional strength can be significantly reduced (however, this also depends on the press system used and the design and material thickness of the fittings). In the case of hot water pipes, heating circuits and other pipe systems in which the pipes are regularly subjected to mechanical stress due to thermal expansion or the like, it is possible in exceptional cases that connections that have been pressed inappropriately can slide apart over time.

Press fittings for PE and multilayer composite pipes

Press fittings for plastic pipes are usually equipped with molded support sleeves, which are inserted into the pipe and prevent the pipe from deforming too much during compression. The pressing then takes place either through the radial pressing of a metallic sleeve, which is also part of the fitting, or through the axial pushing on of a sleeve made of metal or plastic, which has to be pushed onto the pipe beforehand.

Stainless steel threaded and weld fittings

Stainless steel threaded fittings and threaded pipe parts DIN / EN 150 Lbs (10 bar)

Unlike in the USA, where threaded fittings and threaded pipe parts are standardized according to the MSS SP114 standard, dimensions for fittings in Europe are left to the suppliers. Most manufacturers such as Starfit, Aperam, Thyssen Krupp, Kohler AG, Hage Fittings and Flanschen produce the fittings in Asia, as the manufacturing costs are significantly lower than in Europe. Hage fittings and flanges were the last manufacturers of threaded fittings using the investment casting process in Germany and were acquired by Aalberst Industries in 2003 . Threaded fittings in special lengths from pipes, such as pipe double nipples, weld nipples and pipe nipples (with a continuous thread) are still partly manufactured in Germany.

Threaded fittings made of stainless steel are mainly manufactured using investment casting processes and then machined with CNC machines. Threaded pipe parts are cut from stainless steel pipe and then provided with a thread. The threaded fittings and threaded pipe parts for the European market have an ISO7-1 thread as standard , while the fittings for the North American market have an NPT thread. Standard thread sizes for threaded pipe parts and threaded fittings made of stainless steel are 18 ″, 14 ″, 38 ″, 12 ″, 34 ″, 1 ″, 1 14 ″, 1 12 ″, 2 ″, 3 ″, and 4 ″. Most of the stainless steel fittings are made in 1.4404 (316L, V4A), 1.4408 or 1.4571 (316Ti), but there are also cheaper versions in 1.4307 (304L, V2A ).

According to the "Assessment basis for metallic materials in contact with drinking water" in the context of the Drinking Water Ordinance, stainless steels (stainless steel) can be used in the passive state for all product groups A to D. In contrast to copper fittings and malleable cast iron fittings, stainless steel fittings can also be used without a DVGW approval in Germany for the extraction, treatment or distribution of drinking water.

List of available stainless steel threaded fittings   
End of connection Thread end Welding end Hose connection Clasp
Thread end

Bend A / A * (outside / outside),
angle 90 ° I / I (inside / inside; also as reducing
angle and ceiling angle or wall panel), angle 90 I / A (inside / outside; also as reducing
angle ), angle 45 ° I / I,
angle 45 ° I / A,
T-piece (also as reducing T-piece),
cross piece ,
double nipple (also as reducing nipple or offset nipple),
pipe nipple *,
pipe double nipple *,
cast socket (also as reducing socket and reduced Socket nipple),
socket seamless *,
screw connection,
tap extension,
reducers : reducing nipple (offset nipple), reducing socket, reduced socket nipple ("reduction")

Thread adapter NPT (AG) / Rp (IG), thread adapter R (AG) / NPT (IG)

Welding nipple *

Screw connection con./fl. Weld-on welding screw connection con./fl.

Hose nipple with thread *

Hose nozzle

Hexagon plug

Square plug screw plug DIN 910 round cap hexagon cap

Welding end Hose nipple with welding end *
* Threaded pipe part

Stainless steel weld fittings unprocessed / processed

In addition to weld fittings with an unmachined surface, weld fittings with a polished surface are installed in the food industry in particular. The fittings are formed from either welded or seamless stainless steel tubing. In Europe, weld fittings are standardized according to DIN, while in the USA the ASTM / ASME standard is used.

Following complaints from European pipe elbow manufacturers, an anti-dumping proceeding was carried out against stainless steel welding fittings from China in the EU. After reviewing the manufacturing costs of Rohrbogen AG, Erne Fittings, Swiss Fittings, Acrus, OSTP, Ta Chen (China), King Lai (China) and Jndia, import duties were introduced to allow fair competition

See also


  • Kurt Kassler: Copper as a building material for water pipes. 1st edition. Salzwasser Verlag, 2012, ISBN 978-3-86444-830-0 .
  • Johann Mutschmann, Fritz Stimmelmayr: Pocket book of water supply. 13th, completely revised edition. Vieweg Verlag, Wiesbaden 2002, ISBN 3-663-12398-7 .
  • Stefan Wirth: Connecting pipes with press fitting systems. 1st edition. Grin Verlag, Norderstedt 2009, ISBN 978-3-640-41093-4 .

Individual evidence

  1. fitting ( Memento from January 29, 2016 in the Internet Archive ) In: Merriam-Webster. "Fitting the, ↑ fitting". In: Meyer's large pocket dictionary. 1998; "Fitting [engl.] N. 9 connection piece (joint, etc.) in pipelines". In: The German spelling. Bellavista 2004.
  2. ^ The change to industry (1855–1887). Georg Fisch II. In: Swiss pioneers in business and technology. Association for economic history studies Meilen, 2002, ISBN 3-909059-24-4 , p. 47.
  3. GF Piping Systems: 150 years of pipe connectors made of malleable cast iron. Traisen, January 2014.
  4. ^ Franziska Eggimann : Living Industry. View of the corporate archive of Georg Fischer AG. Hier und Jetzt, Baden 2018, ISBN 978-3-03919-427-8 , p. 100.
  5. including Perry, Chilton: Chemical Engineers' Handbook, various editions
  6. Tool systems , In:
  7. Confirmation of suitability , PDF document at
  8. a b Tool use with Connex Bänninger> B <Press systems , In:, IBP Group
  9. Optipress-Aquaplus , press system with stainless steel and gunmetal fittings for stainless steel pipes; Optipress-Therm , press system with zinc-nickel-coated fittings for carbon steel or precision steel pipe and Optifit-Press , press system with zinc-nickel-coated fittings for threaded pipe and boiler pipe , R. Nussbaum AG, Olten, Switzerland
  10. a b c d e f g Technical instructions for V-profile fittings , In:, March 2015.
  11. a b c d e f VSH Technical Manual XPress
  12. Representation of M and V contour in comparison , In:
  13. Characteristics of Eurotubi Fittinge , In:
  14. a b Technical Catalog 2.0 , In:
  15. ^ Aalberts Industries. Retrieved November 25, 2017 .
  16. ICZ HOUSE TECHNOLOGY. Retrieved November 25, 2017 .
  17. Home - ESTHO Edelstahl GmbH & Co. KG. Retrieved February 11, 2019 .
  18. Drinking Water Ordinance (TrinkwV), published on March 26, 2018 by the German Federal Environment Agency
  19. Federal Environment Agency: Basis of assessment for metallic materials in contact with drinking water (basis of assessment of metals) 1. (PDF) In: Federal Environment Agency, March 26, 2018, accessed April 6, 2018 .
  20. Case AD622 - Tubes and pipe fittings of stainless steel (butt-welding fittings) - Trade - European Commission. Retrieved November 28, 2017 .
  21. Implementing Regulation (EU) 2017/141 of the Commission of 26 January 2017 certain imposing definitive anti-dumping duties on imports of tube or pipe fittings, pipe plugs and pipe fittings of stainless steel for butt welding, as finished products, originating in the People's Republic of China and Taiwan retrieved on November 28, 2017 In: Official Journal of the European Union . January 26, 2017.

Web links

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