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A.0500.501 – IM-TGGS/05.01 EN (03/2013)
3.21.7 Designation of threaded connections.
To make clear what sealing type of threaded connection is provided we denominate them according to
standards ISO 7/1 and ISO 228/1 as follows.
3.21.7.1 Threaded connection Rp (example Rp 1/2)
If no flattened sealing face is provided we call the connection Rp accordingly ISO 7/1. This
connection has to be sealed in the thread. The plugs or pipe connections must be provided with
conical thread according to ISO 7/1 external thread (example ISO 7/1 – R1/2).
3.21.7.2 Threaded connection G (example G 1/2)
If the threaded connection is provided of a flattened sealing face we call it G according ISO 228/1.
This connection can be sealed by a gasket. The plugs or pipe connections must be provided with a
sealing collar and cylindrical external thread according to ISO 228/1 (Example ISO 228/1 - G1/2).
Plugs or pipe connections provided with conical thread according to ISO 7/1 external thread
(example ISO 7/1 – R1/2) can also be used.
ISO 7/1
Type
Symbol
Example
Internal
thread
Cynlindrical (parallel)
Rp
ISO 7/1 – Rp 1/2
External
thread
Always conical
(tappered)
R
ISO 7/1 – R 1/2
ISO 228/1
Clearance class
Symbol
Example
Internal
thread
Only one class
G
ISO 228/1 – G 1/2
External
thread
Class A
(standard)
G
ISO 228/1 – G 1/2
Class B
(extra clearance)
G...B
ISO 228/1 – G 1/2 B
ISO 7/1
Type
Symbol
Example
External
thread
Always conical
(tappered)
R
ISO 7/1 – R 1/2
Conical plug
ISO 7/1 - R1/2
Conical pipe end
ISO 7/1 - R1/2
Plug with collar
ISO 228/1 - G1/2
Conical pipe end
ISO 7/1 - R1/2
