In a sampler for sampling a first portion of a liquid flow, the liquid
flow enters at a sampler inlet (12). The sample passes through a valve
(30) into a sample chamber (8) and then the valve closes, diverting the
remainder of the liquid flow to a sampler overflow (6). The valve
comprises a valve inlet (24) coupled to the sampler inlet, a valve outlet
(38, 36) opening into the sample chamber and positioned, in use,
substantially below the valve inlet, a shut-off chamber (32) separating
the valve outlet from the valve inlet, and a valve overflow (34) leading
from the shut-off chamber to the sampler overflow (6). When the liquid
level in the sample chamber rises to a predetermined level it disrupts
the flow of liquid through the valve outlet and diverts later flow
through the valve inlet into the shut-off chamber and through the valve
overflow.