Model 770

Float Switch, External Cage, Vertical, multipoint

The Delta Controls Model 770 Float Switch provides up to four switching alarm contacts at varying liquid levels. The unit features an externally mounted caged float outside the process vessel. This design minimizes process turbulence effects and in order that the level control may be valved off from the process vessel and depressurized for maintenance without disturbing the operation of the process.

The output of the control consists of switching action as the liquid level varies with up to four switch stations operating. Action occurs as the attractor arrives at each switching station. The switch stations are on the outside of the barrier tube which isolates them from the process liquid. Each is equipped with a magnet whose lines of force pass through the nonmagnetic barrier tube. The magnet is pulled in against the outside of the tube when the attractor is lifted into the magnetic field inside the tube. The liquid level rises and the float lifts the attractor in front of each switch station magnet. The magnet pulls in and its output switch is actuated. Each magnet pulls in sequentially as the liquid level continues to rise, and stays in as long as the liquid level is above that point. Decreasing liquid level moves the float/rod/collars/attractor downward.

Each output switch remains actuated until the attractor is pulled out of its magnetic field—it then deactuates. The 770 is to be mounted vertically near the process vessel containing the liquid level to be monitored. It should be positioned so that the desired switching points are located between the upper and lower process connections on the element body. Long lines connecting the process vessel to the element chamber should be avoided; but when necessary, they should be sloped one inch per foot towards the process vessel to limit sedimentation buildup. The 770 provides switching alarm contacts at four elevations of a varying liquid level. The switching alarm points are separated from each other by approximately one and one half inches.