The complete unit may include automatic devices, by-pass valves, flow-restrictors, etc., provided that each test circuit between the meters to be verified and the control tanks is clearly defined and that it is possible to check the internal pressure tightness of the circuits at any time. ...
If a control tank is divided into several chambers, the separating walls must be sufficiently rigid to ensure that the volume of a chamber does not vary by more than 0 72 % according to whether the adjacent chambers are full or empty.
