Proper Installation Practices for 2250 and 2450 Pressure Sensors
The 2250 Hydrostatic Level Sensor and the 2450 Pressure Sensor are gauge pressure sensors. Gauge pressure sensors measure the difference in pressure between the process on one side of a diaphragm and the atmospheric pressure on the opposite side of the diaphragm (Fig 1). A tiny capillary tube inside the sensor body is used to ensure that the back of the diaphragm remains at atmospheric pressure. The capillary tube must be free from water and/or dirt for the sensor to measure pressure accurately.
Installation tips for all pressure sensors (2250 and 2450):
• Always calibrate the sensor at the installation site prior to installing into the application.
This will ensure that the 0 psi value is matched to the ambient air pressure.
• Do not use the 2250 or 2450 sensor if the temperature difference (Delta) between the fluid being measured and the surrounding environment temperature is greater that 10°F (5.5°C). Greater temperature disparity will create condensation inside the capillary tube.
Costly Error (Fig 2):
Fig 2 shows a pressure sensor installed through the wall an outdoor tank. Consult the manual for instructions on calibrating the offset caused by this type of installation.
The cable was spliced here and the capillary tube was exposed to the elements.
Fig 3 is a microscope photo showing rust-colored dirt inside the capillary tube.The sensor failed two months after commissioning. Because there is no practical way to clear the capillary tube, the sensor had to be replaced.
Figure 2
Figure 3
In-line installation (Fig 4):
• Always use a Georg Fischer ball valve to isolate the sensor so it can be removed for service.
• Avoid pipe applications that are prone to water hammer.
Figure 4
Side-tank installation with 3-2450 Pressure Sensor (Fig 5):
• Terminate the capillary inside a 3-8052-1 junction box.
The signal cable can be extended up to 1000ft (300 m) to the transmitter or data collection point.
• Install a ball valve to allow the sensor to be removed for service.
Tank lid installation with 3-2250 Hydrostatic Level Sensor (Fig 6):
• Terminate the capillary inside a 3-8050-1 junction box. The signal cable can be extended up to 1000ft (300 m) to the transmitter or data collection point.
• When manufacturing the stand pipe assembly, use a waterproof sealant to fill the space behind the sensor assembly.
