Model 770
External Cage Level Switch Vertically Rising Float
Download the Series 700 Detailed Datasheet in Acrobat Format
Download the Series 700 Detailed Datasheet in Acrobat Format
Operation:
A float with a long stroke action moves up and down as the liquid level
varies. Switching occurs at up to four separate points.The Delta Controls Model 770 provides switching alarm contacts at up to four elevations of a varying liquid level. The unit has its float mounted outside the process vessel in a cage. The external cage design is utilized to minimize 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. Up to four switch stations are operated. 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 Delta Controls Model 770 should 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 1" per foot towards the process vessel to limit sedimentation buildup.The Delta Controls Model 770A provides switching alarm contacts at four elevations of a varying liquid level. The switching alarm points are separated from each other by approximately 1.5 inches.
The Delta Controls Model 770B provides switching alarm contacts at three elevations of a varying liquid level. The switching points are separated from each other by approximately 2 inches.
The Delta Controls Model 770C provides switching alarm contacts at two elevations of a varying liquid level. The switching points are separated from each other by 4 inches.
The Delta Controls Model 770D provides switching contacts at two elevations of a varying liquid level. One switch station is operated with adjustable wide switching differential.
The liquid level rises and the float lifts the attractor in front of the switch station magnet. The magnet pulls in, the output switch is actuated, and the attractor is "captured" and held in place.
Decreasing liquid level moves the float/rod/collars downward. The attractor stays in place and the output switch remains actuated until the top collar moves down against the attractor and pulls it out of the magnetic field. The attractor falls down against the lower collar by gravity and the output switch is deactuated.
The spacing between the top collar at its maximum elevation and the attractor determines the amount of liquid level differential between output switch actuation and deactuation. Lowering the top collar decreases differential. Access to the collars is achieved by depressurizing the unit and removing the barrier tube.
The on/off differential switching points are separated by a maximum of 5.5 inches.
OPERATION
The Delta Controls Model 770E provides two on/off differential switching contacts as a liquid level varies. The liquid level rises and the float lifts the attractor in front of the switch station magnet. The magnet pulls in, the output switch is actuated, and the attractor is "captured" and held in place.
Decreasing liquid level moves the float/rod/collars downward. The attractor stays in place and the output switch remains actuated until the top collar moves down against the attractor and pulls it out of the magnetic field of that switch station. The output switch is deactuated. The attractor falls down against the lower collar by gravity when pulled out of the magnetic field of the bottom switch station.
The spacing between the top collar, at its maximum elevation, and the attractor determines the amount of liquid level differential between output switch actuation and deactuation. Lowering the top collar decreases differential. Access to the collars is achieved by depressurizing the unit and removing the barrier tube.
The switching points are separated by about 4" and have approximately a 2" differential between actuation and deactuation of the output switch.
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