How to Select Valves

I'd start by doing an internet search:

Valve Selection Guide

It must be remembered that valves are fitted in a system for a purpose, not to be a pain in the backside.

As "a rule of thumb" valve selection is based on the type of valve and the particular system the valve is going to be installed in, and where that system is fitted, e.g. machinery spaces. Ideally we should not have valves with "rubber" or "plastic" components in machinery spaces, because of the danger of fire, and the damage it could cause to those valves.

We have valves that are fitted to prevent return of flow in a system to protect equipment or prevent backflooding.........these valves can be non-return or check valves or SDNRV's, the latter being used in bilge suction valve chests and all fire hydrants (and garden taps).

There are valves used for isolating only such as gate valves, ball valves.........then we have those that can be used for isolation or regulating flow, e.g. butterfly valves (certainly not to be recommended in any marine system), SDSLV's (or globe valves), short and long taper valves (for precise regulation of flow), and diaphragm valves.

For general regulation of flow and isolating valves or sea cocks you cannot go past the SDSLV's. Gate valves also make reasonable sea cocks..........particularly in machinery spaces.

This gives you a brief outline of some valves and their uses...........it is also important to remember to select correct materials of all valve components for sea water systems.......there are some very cheap and nasty valves available, that if used in marine applications could put vessels and crews at risk.

SDNRV's...........screw down non-return valves

SDSLV's..........screw down screw lift valves