Dear all,
does a jacketed pressure vessel with internal pressure of +0,9 barg and jacket internal pressure of -0,5 barg fall into the scope of Section VIII-1?

In my opinion it does not, see U-1(c)(2)(h):
The pressure vessel does not have an internal or external operating pressure of 100 kPa; only the differential (design) pressure exceeds 100 kPa.

What´s your opinion?

Jürgen

Jürgen,
It's a combination unit. In my opinion, whether or not it falls within the scope, should be considered in context of UG-19(a).

Konrad

Also read 9-1(c)

Konrqad

Jürgen,
Hereby App. 9, 9-1(c) which is indeed giving the answer "Where the internal pressure is 15 psi (100 kPa) or
less, any combination of pressures and vacuum in the
vessel and jacket which will produce a total external
pressure greater than 15 psi (100 kPa) on the inner vessel
wall, the entire jacket shall be interpreted as within the
scope of this part."