Versatile: 7 facts about solder fittings
In many areas today, installers rely on press connections, which can be made quickly and reliably. However, solder fittings are still used time and again and, in some areas such as food, medical gases or high-pressure applications, are the superior technology. By soldering the solder fitting to the pipe using heat or a soldering agent, a pipeline becomes permanently tight.
We not only offer you a wide range of dimensions and shapes of solder fittings in high quality from our own factories, but also support you if there are questions about the connection technology "soldering", the suitable solder or our planning service.
1. What is capillary soldering technology?
The capillary soldering technique makes use of the effect of the same name known from physics: In a capillary (=hair tube), liquids rise - due to adhesion forces (forces of attraction between different substances) - against the force of gravity until a balance of forces between
- the weight of the liquid column and
- the capillary force resulting from the capillary filling pressure,
The principle is reminiscent of a sponge placed in water. The following applies: The narrower the capillary, the higher the liquid column rises.
2. Areas of application of solder fittings
Capillary solder fittings consist of
- deoxidised copper Cu-DHP (CW024A, min. 99.90 % CU)
- Copper alloys such as brass (Cu-Zn39Pb2, Cu-Zn40Pb2)
- gunmetal (CC499K, CuSn5Zn5Pb2-C) as well as,
- especially for high-pressure brazing applications in the transcritical range, made of copper-iron alloy CuFe (CuFe2P, CW107C).
Brazing fittings for hard or soft soldering, such as the 5000 series, comply with EN 1254 and can be used in heating, solar and compressed air systems, as well as (as CuFe alloy) in high-pressure applications such as cooling and refrigeration circuits. These fittings are metric, i.e. the dimension is given in millimetres.
In principle, it is also possible to use soldered fittings in drinking water applications, provided the relevant certifications are available, as the materials are included on the positive list of the German Federal Environment Agency. However, according to DVGW worksheet GW 2, only soft soldering is permitted in drinking water installations. In this particularly health-relevant area, we generally recommend using press fittings made of lead-free materials such as stainless steel or silicon bronze CuSi.
The soft-soldered connection can only be used up to operating temperatures of max. 110 °C. Brazed joints in gas, liquid gas and oil lines, on the other hand, may only be made as hard soldering. Since standstill temperatures of more than 110 °C can occur in the collector circuit of solar thermal systems, brazing should also be selected for soldered joints there.
3. Solder fittings for industry, medical gases and more
Due to their high material resistance, solder fittings can withstand many aggressive fluids and are therefore not only suitable for the installation of copper pipes in "normal" building services, but are also suitable for many industrial requirements.
SANHA 4000 and 5000 series solder fittings can also be used for medical gases. The quality is ensured by independent tests and certifications, such as the Gütegemeinschaft Kupferrohr. The solder fittings are suitable for degreased copper tubes according to EN 13348 and EN 1057 and are characterised by optimum corrosion resistance and a low carbon content.
Typically, a solder fitting can withstand an operating temperature of 110 °C and a pressure of up to 40 bar. The permissible operating pressures for copper pipelines with capillary solder fittings are described in EN 1254-1. They depend on the operating temperature and the outer pipe diameter. These pressures are perfectly adequate for the usual applications such as drinking water, gas or heating installations. However, SANHA capillary solder fittings can be subjected to much higher loads. SANHA® capillary solder fittings up to d = 159 mm are suitable for use in the refrigeration/air conditioning sector. In accordance with the Pressure Equipment Directive 97/23/EC, the operating pressure is max. 45 bar when installed correctly and using brazing alloys containing silver in conjunction with suitable fluxes (see table below).
4. Special case of cooling and refrigeration lines in transcritical areas
Nowadays, CO2 (R744) is increasingly used as a refrigerant in cooling and refrigeration circuits. CO2 is a climate gas, but in some cases it is up to 11,000 times less harmful (according to IPCC AR 5, based on 20 years) than conventional refrigerants (e.g. CFCs). In this case, the pipelines and fittings must withstand very high operating pressures over the long term. Special high-pressure fittings made of CuFe (RefHP, series 29000) are available for this purpose. These solder fittings can be used up to 130 bar operating pressure. The dimensions of these high-pressure fittings are given in inches.
Maximum permissible operating pressures for copper piping with SANHA® capillary solder fittings
|Connection type||Operating temperature||Outside pipe diameter|
|6...28 mm||35...54 mm||64...108 mm|
|Soft soldering||30 °C||25 bar||25 bar||16 bar|
|65 °C||25 bar||16 bar||16 bar|
|110 °C||16 bar||10 bar||10 bar|
|Hard soldering||30 °C||25 bar||25 bar||16 bar|
|65 °C||25 bar||16 bar||16 bar|
|110 °C||16 bar||10 bar||10 bar|
Thread design: Pipe thread: R/Rp thread according to EN 10226, Fastening thread (ÜWM): G-thread according to ISO 228
Use in the refrigeration and air-conditioning sector
SANHA® capillary solder fittings are suitable for use in the refrigeration and air-conditioning sector. In accordance with the Pressure Equipment Directive 97/23/EC, the operating pressure is max. 45 bar at an operating temperature of max. 120 °C when properly installed and using silver-containing brazing alloys in conjunction with suitable fluxes up to 54 mm - in this case or for other areas of application, please contact our Technical Application Advice at email@example.com or +49 2054 925 170.
5. solder fittings in all sizes and shapes
There is a large selection of different solder fittings. In addition to 90° elbows, T-pieces, transition nipples and screw fittings, matching wall washers, screw-in parts or insertion pieces are offered, for example. Capillary solder fittings are standardised in EN 1254-1. SANHA capillary solder fittings made of copper (series 5000) or for transitions to threaded connections made of gunmetal (series 4000) fulfil the requirements specified therein in all points. The manufacturing quality is constantly monitored.
However, not only the quality of the articles, but also the effectiveness of the ongoing quality controls are regularly checked by neutral testing institutes according to the strict rules of the Gütegemeinschaft Kupferrohr e.V. and the DVGW. The capillary solder fittings therefore carry both the quality mark of the Gütegemeinschaft Kupferrohr e.V. and the DVGW mark.
6. What must be observed when soldering
Soft solders are standardised in EN 29453. According to DVGW-GW 2, the following may be used for drinking water installations:
- S-Sn97Cu3 (soft solder with 97 % tin and 3 % copper, melting range 230 °C ... 250 °C, catalogue no. 4933),
- S-Sn97Ag3 (soft solder with 97 % tin and 3 % silver, melting range 220 °C ... 230 °C, catalogue no. 4934).
A soft solder flux according to EN 29454-1 is always required so that the soft solder can wet and bind. Fluxes must be soluble in cold water and rinsable. This is given if the fluxes are certified according to GW 7 and bear the DVGW mark. Flux should only be used sparingly and only applied to the outer soldering end (pipe end), which has been cleaned with metal-free fleece, and then inserted into the inner soldering end (fitting sleeve), which has also been cleaned, e.g. with an internal cleaning brush (Catalogue No. 4974). In this way, no flux can penetrate the inside of the cable (beyond a technically unavoidable level).
The use of soft solder pastes (flux-solder mixtures) is particularly popular. These consist - if they bear the DVGW mark - of at least 60 percent by weight solder powder, the rest soft solder flux. As soon as the working temperature - at which the solder can wet and bind - is reached, the solder portion in the paste melts. This is - easily recognisable by a silvery shiny appearance - the point at which the additional solder must be applied to fill the solder gap. This means that the danger of burning (the flux would then naturally become ineffective) no longer exists.
For drinking water installations, soft solder pastes - such as the SANHA® soft solder paste (catalogue no. 4943) - should also carry the DVGW mark. Soft solder pastes are to be used like fluxes, i.e. they are also to be applied only thinly to the cleaned outer solder end. When soft soldering, the entire solder joint must be heated to working temperature. The soft solder should then be applied to the end of the soldering gap without direct flame exposure and melted off. Soft soldering requires experience in temperature and flame control for dimensions over 42 mm outer diameter. For these dimensions, brazing is therefore recommended for soldered joints.
Brazing alloys for solder fittings are standardised in EN 1044. According to DVGW-GW 2, the following brazing alloys may be used for drinking water installations from 35 mm outer diameter:
- CP 203, brazing alloy with 94 % copper and 6 % phosphorus, melting range 710 °C ... 890 °C, catalogue no. 4939),
- CP 105, brazing alloy with 92 % copper, 2 % silver and 6 % phosphorus, melting range 645 °C ... 825 °C, catalogue no. 4936).
These phosphorus-containing brazing alloys should be processed without flux when connecting copper to copper. The phosphorus contained in the solder takes over this function. However, if one of the two components is made of a copper alloy (brass or gunmetal), a brazing flux should be used:
- AG 104, brazing alloy with 27 % copper, 45 % silver and 3 % tin, melting range 640 °C ... 680 °C, catalogue no. 4937),
- AG 106, brazing alloy with 36 % copper, 34 % silver and 3 % tin, melting range 630 °C ... 730 °C,
- AG 203, brazing alloy with 30 % copper and 44 % silver, melting range 675 °C ... 735 °C.
These high-silver brazing alloys must always be processed with flux. For copper pipe installations, a high-silver brazing alloy (e.g. AG 104, catalogue no. 4937) must generally be used in rooms with atmospheres containing ammonia and/or hydrogen sulphide to prevent corrosion damage.
7. Correct solder joint preparation
The surfaces to be joined must be made metallically bright (free of dirt and oxide) for both soft soldering and hard soldering. For this purpose, a metal-free fleece (catalogue no. 0961) should preferably be used for the outer soldering surfaces (tube ends). For cleaning the inner soldering ends (fitting sleeves), it is recommended to use an inner cleaning brush (Catalogue No. 4974) adapted to the dimensions, especially for the smaller dimensions. If flux is required (see above), it should only be applied thinly to the outer soldering end. Soft copper tubes (ring tubes) generally have a non-circular cross-section. In order to create the capillary gap required for a perfect solder joint in connection with a circular fitting sleeve, soft copper tubes must be made circular again by calibrating before soldering. The calibrating mandrel and calibrating ring must be driven into or onto the tube end one after the other - not at the same time.
Do you have any questions about a specific solder fitting or the corresponding soldering process? Then please contact our technical application advice on 01628 819 245, firstname.lastname@example.org or email@example.com! We will be happy to assist you with your specific application.
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