MODEL 767 EXTERNAL CAGE FLOW SWITCH
WITH WIDE SWITCH ACTION SPACING
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. - Switching Stations: 1 to 4; alarm and/or differential
- Differential: up to 72"
- Specific Gravity: 0.4 to 2.4
- Temperature: -20 to 750°F
- Pressure: -15 to 2200 PSIG
- Process Connection: Same as type 760
Model
767A External Cage Level Alarm
Two Widely Spaced Adjustable Points
OPERATION
The Delta Controls Model 767A provides switching action at two field selected liquid level elevations. The unit has its element mounted outside the process vessel. The external cage design, with flanged cage closure, 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 setpoint adjustment or maintenance without disturbing the operation of the process. Two switch stations are operated as the liquid level varies. Action occurs as the attractor moves in front of each switching station magnet. The barrier tube isolates the switch stations from the process liquid.
SETPOINT COLLAR ADJUSTMENT
The setpoint collar is locked in place by a socket head setscrew. The collars may be repositioned as required to achieve switching action at various fluid elevations.
SUPPORT SPRING
The spring supports the weight of the attractor/stroke rod assembly in the middle, or neutral position. The position of the spring collar is adjusted so that the attractor is positioned in the center of its travel when the float is floating on the liquid surface and is not in contact with either setpoint collar.
SLIDING FLOAT
The float has a hollow tube through its centerline. The tube is generously larger than the stroke rod which passes through the tube and maintains the float's horizontal position. The float is normally supported by the liquid and moves up and down on the stroke rod as the liquid level varies. An "upper" and a "lower" setpoint collar are positioned on the stroke rod. The float pushes against one of the collars when the fluid level rises or falls to that setpoint elevation. The force produced by the float moves the stroke rod and positions the attractor in front of a switch station magnet. The magnet is attracted and that output signal switch is operated.
ALARM ACTION
Two independent switch stations are mounted on the barrier tube. On/Off switch action occurs as the float contacts the upper or lower collars and moves the attractor in front of the switch station magnet.
INSTALLATION
The Delta Controls Model 767A should be mounted vertically near the process vessel containing the liquid level to be monitored. It should be positioned so that the desired switching point is 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 process isolation valves and drain system should be in accordance with the governing codes. The Model 767A can be quite heavy. Suitable additional supports should be provided when needed.
Model 767D External Cage Level Control
On/Off with Wide Adjustable Spacing Between Action Points
OPERATION
The Delta Controls Model 767D provides switching action at field selected liquid level elevations. The unit has its element mounted outside the process vessel. The external cage design, with flanged cage closure, 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 setpoint adjustment or maintenance without disturbing the operation of the process. The output of the control consists of on/off switching action with wide spacing between switch actuate and deactuate elevations. The switch station is actuated as the attractor moves in front of the switching station magnet. Deactuation occurs when the attractor is pulled out of the magnetic field. The barrier tube isolates the switch station from the process liquid.
SETPOINT COLLAR ADJUSTMENT
The setpoint collar is locked in place by a socket head setscrew. The collars may be repositioned as required to achieve switching action at various fluid elevations.
SUPPORT SPRING
The spring supports the weight
of the attractor/stroke rod assembly, in the middle, or neutral position.
The position of the spring collar is adjusted so that the stroke rod is positioned
in the center of its travel when the float is, floating on the liquid surface
and is not in contact with either setpoint collar.
SLIDING FLOAT
The float has a hollow tube through its centerline. The tube is generously larger than the stroke rod which passes through this tube and acts to maintain the floats horizontal position. The float is normally supported by the liquid level and moves up and down on the stroke rod as the liquid level varies. An "upper" and a "lower" setpoint collar are positioned on the stroke rod. The float pushes against one of the collars when the fluid level rises (or falls) to that setpoint elevation. The force produced by a rising level moves the stroke rod up and positions the attractor in front of the switch station magnet. The magnet is attracted and the output switch is operated.
ADJUSTABLE DIFFERENTIAL ACTION
The attractor is free to slide on the stroke rod. 0.75" of space is adjusted between the top of the attractor and its upper positioning collar. The attractor is carried up into the field of the station magnet when the float lifts the top setpoint collar up. The switch station magnet is then pulled in and the attractor is "captured" and supported by the station magnet. The station remains actuated until the float reaches the lower setpoint collar and pushes it down. The upper attractor positioning collar moves down against the attractor and pulls it out of the field of the switch station magnet. The attractor then falls against its lower positioning collar and the switching station deactuates. In summary, after being actuated by the float pushing the upper setpoint collar up, the switch station remains actuated until the float pushes the lower setpoint collar down.
INSTALLATION
The Delta Controls Model 767 should be mounted vertically near the process vessel containing the liquid level to be controlled. It should be positioned so that the desired switching point is 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. Process isolation valves and drain system should be in accordance with the governing codes. The Model 767 can be quite heavy. Suitable additional supports should be provided when needed.
