Hi all.
how understand the notation in the api610 p.No. 5.3.3. When we wat to design api pump eg. OH2 we have to assumed 4MPa or 5MPa (PN50; ISO 7005-1) pressure in casing?
thx for answer

any suggestions?

fyi, next time, specify which edition of 610 you are referencing.  the 11th edition does not have 5.3.3.  10th edition 5.3.3 is same as 11th edition 6.3.3.

11th edition 6.3.3.

6.3.3 The pressure casing shall be designed to
a) operate without leakage or internal contact between rotating and stationary components while subject simultaneously to the MAWP (and maximum operating temperature) and the worst-case combination of twice the allowable nozzle loads of Table 5 applied through each nozzle;
b) withstand the hydrostatic test (see 8.3.2).
NOTE The twice-nozzle-load requirement is a pressure-casing design criterion. Allowable nozzle loads for piping designers are the values given in Table 5, which, in addition to pressure casing design, include other factors that affect allowable nozzle loads, such as casing support and baseplate stiffness.

what is the system MAWP, 4MPa or 5MPa?  that is the casing design pressure and at maximum temperature of the fluid.

hope this helps.  good luck!
-pmover

THX, everything what You write it is fackt and
I know it. I would like to understand what value of pressure I heve to assumed when I designed pressure casing? Point 5.3.5 API610 10th "minimum  gauge pressure rating of 40bar or at least ISO 7005-1 PN50"
Which pressure 40bar or 50bar?
Sorry maby I don't understand this but it isn't clear to me.