VEGA VEGADIF 65 Chemical seal CSB - Manual (Page 14)

14
3 Planning instructions for isolating systems
Chemical seal CSB • for VEGADIF 65
36133-EN-130417
= -51.80 mbar
Hence a 100 mbar measuring cell is required for this application
example.
3.6 Calculation of the temperature error
With double-sided mounting of chemical seals, the total temperature
influence is composed of the following:
•
Influence of the process temperature on the chemical seal
(TK
Process
)
•
Corrective factor with special materials (with Tantalum, Hastelloy:
1.5; with PTFE coating: 1.8)
•
Corrective factor for filling oil
•
Influence of the ambient temperature on the transmitter (TK
Ambient
)
The calibration temperature of the isolating system is 20 °C.
The TK
Process
of the respective chemical seal is listed in the charts in
chapter "Dimensions and weights". The corrective factor with special
materials is available on request. The corrective factor for the filling
oil is listed in chapter "Filling oils". The thermal change of zero signal
and span is specified in chapter "Technical data" of VEGADIF 65. The
calculated influencing factors must be summed geometrically.
•
Process temperature: 100 °C
•
Flange isolating diaphragm DN 80 PN 10-40
•
Capillary length: 4 m
•
Filing oil silicone, correction factor 1
•
Diaphragm material.: Tantalum, correction factor 1.5
•
Ambient temperature TU: 40 °C
TK
chemical seal
= 0.3 mbar/10K
ΔT Process temperature-Reference temperature chemical seal
= 100 °C - 20 °C = 80 K
Number of chemical seals = 2
Corrective factor diaphragm material = 1.5
Error calculation
Δp
chemical seal
= (0.3 mbar/10K) • 80K = 2.4 mbar • 2 = 4.8 mbar
= 4.8 mbar • 1,5 = 7.2 mbar
With double-sided mounting of chemical seals, the total temperature
influence is 7.2 mbar
Example of double-sided
chemical seal: