All pressure gauges and other similar instruments in oil
systems should wherever possible be fitted with an isolating valve
or cock at the connection to the pressure take off point. The number
of pressure take off points should be kept to a minimum and gauge
piping runs should be as short as practicable. Copper pipes may be
joined by brazing but soldered connections should not be used in oil
systems.
Temperature gauges in oil systems should be fitted into
a fixed pocket (thermowell).
Oil level gauges should be of a design which is approved
for the intended service. The installation of level gauges into the
lower part of oil tanks is prohibited under SOLAS for passenger ships,
and is discouraged for cargo ships. Suitably protected gauges having
heat resistant flat glass of substantial thickness and self-closing
fittings at each tank connection may be fitted to oil tanks in cargo
ships. Round gauges glasses are not permitted.