• Figures 1 and 3 - indicate the position of both the pressure and vacuum pallets, when tank and atmospheric pressure are equal. i.e. both pallets are fully seated.
• Figures 2 - shows the position of both pallets, as set pressure is reached, with escaping vapour lifting the pressure pallet and holding the vacuum pallet closed.
• Figures 4 - shows the position of both pallets, as set vacuum is reached, with atmospheric pressure lifting the hinged vacuum pallet to allow ingress of air into the tank, whilst holding the pressure pallet closed.