If the sump is open to atmosphere then you have around 10 m NPSHa before you start. How deep is this sump? With the low flow high head you are talking about you will need a positive displacement pump. How about reading this thread, sounds suspiciously remarkably similar.

Remember again that acceleration head could be many times larger than friction head losses when calculating NPSHa and must be considered carefully when using reciprocating pumps.

You say "can type pump", what exactly do you invisage? Again, how deep is the sump and what is your space constraint?

This is basicaly a tank which collects the open drains and is located in our deck( This is an offshore platform). We have hardly an elevation of 350mm from drain nozzle(which will be the proposed pump suction) to the deck level.Tank is at atmospheric pressure and will be drained frequentlly.

You then have about 9.65 m NPSHa (unless I am not understanding you correctly).

Remember that NPSH is in absolute terms, so you start off with around 10m HPSHa just for atmospheric pressure.

For your duty the 30 bar discharge pressure sounds much too high, what are you pumping this stuff into?

If the pressure were much lower, around 8 bar or so then it would be a job for an air operated diaphragm pump. Wilden or similar. If 30 bar is correct then you are looking at a reciprocating pump or a progressive cavity pump.

However they will not do the 30 bar different