4
Section 1
Model 351/352/353 Liquid Level Systems
Product Description
Model 351 Liquid Level System
The Model 351 consists of a
single reference sensor
connected by capillary
tubing to a Barton Differential Pressure Unit (DPU). Hydraulic fluid is sealed
inside the sensor and the capillary tubing, eliminating the need for additional
piping.
The Model 351 system, as shipped from the factory, needs only to be mount-
ed on the vessel to provide continuous level measurement when used with a
Barton readout instrument. The sensor can be installed on vented or sealed
process vessels. The readout instrument (DPU, for example) can be installed
at various elevations (i.e., below the vessel, at the vessel upper connection or
above the vessel ) as long as the instrument calibration considers the elevation
difference between the instrument and the sensor.
Model 352 Liquid Level System
The Model 352 consists of
two reference sensors
connected by capillary tub-
ing to a Barton DPU.
Unlike the Model 351 system, the process media does not come into contact
with the DPU, making the model ideal for applications involving corrosive
liquids or tank temperatures above 200°F (95°C).
The DPU can be mounted up to 50 ft (15 meters) away from the vented or
sealed process vessel and at ele vations up to 30 ft (9 meters) above the lowest
sensor. Elevation of the readout instrument (DPU) with respect to the sensors
is essentially unlimited as long as the instrument calibration considers the
elevation difference between the two sensors.
Model 351/352 System Sensors
A Model 351 or Model 352 system can include any of three sensor types,
depending on the pressure rating required:
•
500-psi SWP sensor (referred to as Model 351 sensor throughout this
document)
•
3,000-psi SWP sensor (referred to as Model 351 sensor throughout this
document)
•
No-pressure-rating sensor (referred to as Model S048 sensor throughout
this document)
All three sensor types contain a 3.75” (95 mm) bellows that functions as a
seal. As pressure on the bellows varies due to changes in liquid level and/or
process system pressure variations, these pressure variations are transmitted
through the liquid filled sensor and capillary tubing to the readout instrument.
