Which pipe fits which connection?
The pipe must have the correct dimension for the valve, otherwise coupling pieces must be used. Depending on the type of connection (welding or brazing), the inside or outside diameter of the connection is decisive; if necessary, there is an additional step on the inside.
Exemplary sketch of a shut-off valve, showing the dimensions that are relevant for connection to the piping:
A: Outside diameter at pipe insertion end
B: Inside diameter at pipe insertion end
C: Pipe stop diameter, stepped
This is an example. The 1 .. 2 maintenance connections can be located at the top or on the side, or they can be omitted. The connection to the compressor, pressure vessel etc. (bottom) can be a flange or Rotalock connection.
A: Outside diameter at pipe insertion end
B: Inside diameter at pipe insertion end
C: Pipe stop diameter, stepped
D: Largest diameter at sealing surface, connection diameter to compressor, pressure vessel etc.
A: Outside diameter at pipe insertion end
B: Inside diameter at pipe insertion end
C: Pipe stop diameter, stepped
D: Largest diameter at sealing surface, connection diameter e.g. to compressor, pressure vessel or valve
Depending on the available specifications on the connection or pipe, a conversion between mm and inches ('') is necessary (see EN 12735-1:2020). The following generally applies:
1 mm = 0,03937'' (inches)
1'' (inch) = 25,4 mm
The inside diameters of the connections are usually designed to fit standard diameters of "imperial" pipes.
Taking valve Di22/Da30/S/Tx as an example:
- Brazing: The determining factor is the inside diameter of the valve connection: 22,35 mm. Suitable pipes are:
- "Imperial" pipes with an outside diameter of 7/8" (= 22,23 mm)
- "Metric" pipes with an outside diameter of 22 mm
- Butt-welding ("edge to edge"): The determining factor is the outside diameter of the valve connection: 30 mm. Suitable pipes should have the same outside diameter or be fractionally smaller, e.g. 26,9 mm (DN20).
Brazing connections
Inside diameter of connection (if applicable, stepped) | Outside diameter of pipes suitable for brazing |
|---|---|
10,1 mm | 3/8'' // 10 mm |
12,8 mm | 1/2'' |
15 mm | 15 mm |
16 .. 16,1 mm | 5/8'' // 16 mm |
19,15 mm | 3/4'' |
22,35 mm | 7/8'' // 22 mm |
28,2 mm | 28 mm |
28,6 .. 28,8 mm | 1 1/8'' |
35,2 mm | 1 3/8'' // 35 mm |
41,4 mm | 1 5/8'' |
42,2 mm | 42 mm |
54,2 mm | 2 1/8'' // 54 mm |
64,3 mm | 64 mm |
67 mm | 2 5/8'' |
76,3 mm | 76 mm |
79,6 mm | 3 1/8'' |
89 mm | 3 1/2'' |
89,3 mm | 3 1/2'' // 89 mm |
105 mm | 4 1/8'' |
108,3 mm | 108 mm |
130,5 mm | 5 1/8'' // 130,2 mm |
134 mm | 5 1/4'' |
Welding connections
Outside diameter of connection | Outside diameter of pipes suitable for welding |
|---|---|
14 mm | 13,5 mm (DN8) |
17,2 mm | 17,2 mm (DN10) |
21,3 .. 25,4 mm | 21,3 mm (DN15) |
27 .. 30 mm | 26,9 mm (DN20) |
33,7 .. 37,7 mm | 33,7 mm (DN25) |
37,8 .. 45,5 mm | 42,4 mm (DN32) |
48 .. 49 mm | 48,3 mm (DN40) |
60 mm | 60,3 mm (DN50) |
76 mm | 76,1 mm (DN65) |
89 mm | 88,9 mm (DN80) |
112,5 .. 114,8 mm | 114,3 mm (DN100) |
139,7 mm | 139,7 mm (DN125) |
168,3 mm | 168,3 mm (DN150) |
219,1 mm | 219,1 mm (DN200) |
Depending on the expected pressure, ensure that the wall thickness of the pipes is suitable and sufficient! Pipes made of unalloyed black steel are ideal for welding, as the connections are also made of black steel. If stainless steel pipes are to be used, the welding rod must be suitable for this combination.
Nominal diameters (DN) are not actual dimensions!
The nominal diameters DN10 .. DN200 only indicate ranges! The number is not a quantifiable unit, it is only indirectly related to the diameters of the connections and should not be used in calculations.
Connections with the same dimensions are not necessarily interchangeable!
There are often bushes, flanges, pipe connections or valves with similar dimensions, but they cannot necessarily be used with the same products (compressors, pressure vessels etc.)! Which connections are available for which product is listed in the corresponding tables.