WIKA 233.50 - Manual (Page 12)

GB
2080268.06 02/2013 GB/D/F/E
WIKA operating instructions pressure gauge, model 2 per ATEX 12
Installation with
spanner
Spanner flats Sealing in
the thread 
Sealing face 
6. Commissioning, operation
6. Commissioning, operation
Mechanical connection
In accordance with the general technical regulations for pressure
gauges (e.g. EN 837-2 "Selection and installation recommendations for
pressure gauges").
When screwing gauges in, the force required for this must not be
applied through the case, but rather through the spanner flats (using a
suitable tool) provided for this purpose on the square shaft of standard
connections.
Correct sealing of pressure gauge connections with parallel threads 
must be made using suitable sealing rings, sealing washers or WIKA
profile seals. The sealing of tapered threads (e.g. NPT threads) is made
by providing the thread  with additional sealing material such as, for
example, PTFE tape (EN 837-2).
The torque depends on the seal used. Connecting the gauge using
a clamp socket or a union nut is recommended, so that it is easier to
orientate the gauge correctly. When a blow-out device is fitted to a