Endress+Hauser Deltabar S FMD 77 - Ambient Temperature Range; Response Time

Deltabar S
Endress+Hauser 49
Ambient temperature range The filling oil, capillary length, capillary internal diameter and the diaphragm diameter of the diaphragm seal
have an influence on the ambient temperature operating range of a diaphragm seal system.
Note!
For further information and comprehensive diaphragm seal system designs, please see your local
Endress+Hauser Sales Center.
Response time The viscosity of the filling oil, the capillary length and the capillary internal diameter influence the frictional
resistance. The greater the frictional resistance, the longer the response time.
Furthermore, the volume change of the measuring cell influences the response time. The lower the
volume change of the measuring cell is, the less filling oil has to be shifted in the diaphragm seal system.
The following diagram shows typical response times (T90%) for the various filling oils dependent on the
measuring cell and the capillary internal diameter. The values given are in seconds per metre of capillary length
and must be multiplied by the actual length of the capillary. The rise time of the transmitter must also be taken
into consideration.
P01-FMD78xxx-05-xx-xx-xx-000
Minimize temperature effect by Comment
Smaller capillary internal diameter The response time increases with decreasing diameter.
Shorter capillary –
Diaphragm seal with larger diaphragm diameter –
Filling oil with a smaller coefficient of thermal expansion – Observe compatibility of the filling oil with the fluid.
– Observe the filling oil operating limits.
Optimise ambient temperature operating range
by
Comments
Shorter capillaries –
Smaller capillary internal diameter The response time increases.
Diaphragm seals are used with the following capillary
internal diameters as standard:
– ≤ 2" (DN 50): 0.04" (1 mm)
– > 3" (DN 50): 0.08" (2 mm
Filling oil with smaller coefficient of thermal expansion – Observe compatibility of the filling oil with the fluid.
– Observe the filling oil operating limits.
Diaphragm seal with larger diaphragm diameter –
0
7
13
20
26
0.04” (1 mm) 0.04” (1 mm)
3” (DN 80) 3” (DN 80)
0.08” (2 mm) 0.08” (2 mm)
200 inH O (500 mbar)
2
2” (DN 50) 2” (DN 50)
45 psi (3 bar)
Silicone oil
High temperature oil
Vegetable oil
Inert oil
Nominal diameter
Capillary internal diameter
Measuring cell
Response time (T90%) [sec/ft]
Ambient temperature range = 68°F (20°C)