IMPROVEMENTS IN OR RELATING TO LIQUID FLOW SYSTEMS
A liquid flow system comprising conduit means through which liquid is pumped in normal use, and including means to determine the level of particulate contamination within that liquid, comprising: a valve in communication with the conduit means and comprising a valve member (1) moveable relatively to a valve housing (4), in which the member can be set relative to the housing to define a narrow clearance (20) through which flow takes place; means to interrupt the normal pumped flow of liquid through the system and, when it is so interrupted, to cause liquid to flow instead through the said valve clearance, and means to monitor the volume of liquid so passed, and thereby to derive a measure of the degree of contamination of the liquid in the system characterised in that the flow through the said narrow clearance is in a direction substantially at right angles to that of the said relative movement of the valve member and valve housing.