Siemens SITRANS P Manual de usuario descargar pdf (Pagina 156)

SITRANS P measuring instruments for pressure

Remote seals for transmitters and pressure gages

Technical description

2/156

Siemens FI 01 · 2009

Calculation of the temperature error

The following equation is used to calculate the temperature er-

ror:

Example of temperature error calculation

Dependence of temperature error on diaphragm material

The temperature errors listed in the previous table are based on

the use of stainless steel as the diaphragm material. If other dia-

phragm materials ar

e used, the temperature err

ors change as

follows:

Maximum temperature of medium

The following maximum temperatures of the medium apply de-

pending on the material of the wetted parts:

Maximum capillary length for diaphragm seals (guidance

values)

dp = (ϑ

– ϑ

Cal

) ⋅ f

+ (ϑ

Cap

– ϑ

Cal

) ⋅ l

Cap

⋅f

Cap

+ (ϑ

– ϑ

Cal

) ⋅ f

dp Additional temperature error (mbar)

Temperature on remote seal diaphragm (generally

corresponds to temperature of medium)

Cal

Calibration (reference) temperature (20 °C (68 °F))

Temperature error of remote seal

Cap

Ambient temperature on the capillaries

Cap

Capillary length

Cap

Temperature error of capillaries

Ambient temperature on pressure transmitter

Temperature error of the oil filling in the process

flanges of the pressure transmitter

Existing conditions

SITRANS P pressure transmitter for

differential pressure, 250 mbar, set

to 0 ... 100 mbar, with DN 80 remote

seal diaphragms without tube, dia-

phragm made of stainless steel,

mat. No. 1.4404/316L

= 0.1 mbar/10 K

(0.0014 psi/10 K)

Capillary length l

Cap

= 6 m (19.7 ft)

Capillaries fitted on both sides f

Cap

= 0.07 mbar/(10 K ⋅ m

Cap

)

(0.001 psi/(10 K ⋅ m

Cap

))

Filling liquid silicone M5 f

= 0.07 mbar/10 K

(0.001 psi/10 K)

Process temperature ϑ

= 100 °C (212 °F)

Temperature on the capillaries ϑ

Cap

= 50 °C (122 °F)

Temperature on pressure transmit-

ter

= 50 °C (122 °F)

Calibration temperature ϑ

Cal

= 20 °C (68 °F)

Required

Additional temperature error of

remote seals

Calculation

in mbar

dp = (100 °C – 20 °C) ⋅ 0.1 mbar/10 K + (50 °C – 20 °C) ⋅ 6m ⋅

0.07 mbar/(10 K ⋅ m) + (50 °C – 20 °C) ⋅ 0.07 mbar/10 K

dp = 0.8 mbar + 1.26 mbar + 0.21 mbar

in psi

dp = (212 °F – 68 °F) ⋅ 0.0014 psi/10 K + (112 °F – 68 °F) ⋅ 19.7 ft ⋅

0.001 psi/(10 K ⋅ 3.28 ft) + (112 °F – 68 °F) ⋅ (0.001 psi/10 K)

dp = 0.012 psi + 0.018 psi + 0.003 psi

Result

dp = 2.27 mbar (0.033 psi) (corresponds to 2.27% of set span)

Note

The determined temperature error only applies to the error resulting

from connection of the remote seal.

The transmission response of the respective transmitter is not

included

in this consideration.

It must be calculated separately, and the resulting error added

to the

error determined above from connection of the remote seal.

Diaphragm material Change in temperature error of

remote seal

Increase in values by

Stainless steel See previous tables

Hastelloy C4, mat. No. 2.4610 50%

Hastelloy C276, mat. No. 2.4819 50%

Monel 400, mat. No. 2.4360 60%

Tantalum 50%

Titanium 50%

PTFE coating on stainless steel dia-

phragm

80%

ECTFE coating or PFA coating on

stainless steel diaphragm

100%

Gold coating on stainless steel dia-

phragm

40%

Material p

abs

< 1 bar

(14.5 psi)

abs

> 1 bar

(14.5 psi)

°C (°F) °C (°F)

Stainless steel, 316L 200 (392) 400 (662)

PTFE coating 200 (392) 260 (500)

ECTFE coating 100 (212) 150 (302)

PFA coating 200 (392) 260 (500)

Hastelloy C4, mat. No. 2.4610 200 (392) 260 (500)

Hastelloy C276, mat. No.

2.4819

200 (392) 400 (662)

Monel 400, mat. No. 2.4360 200 (392) 400 (662)

Tantalum 200 (392) 300 (572)

Nom. diam. Max. length of capillary

Diaphragm seal Clamp-on seal

m (ft) m (ft)

DN 25 (1 inch) 2.5 (8.2) 2.5 (8.2)

DN 32 (1¼ inch) 2.5 (8.2) 2.5 (8.2)

DN 40 (1½ inch) 4 (13.1) 6 (19.7)

DN 50 (2 inch) 6 (19.7) 10 (32.8)

DN 65 (2½ inch) 8 (26.2) 10 (32.8)

DN 80 (3 inch) 10 (32.8) 10 (32.8)

DN 100 (4 inch) 10 (32.8) 10 (32.8)

DN 125 (5 inch) 10 (32.8) - -

1 2 ... 151 152 153 154 155 156 157 158 159 160 161 ... 233 234

Comentarios a estos manuales

Sin comentarios

Siemens SITRANS P Manual de usuario Pagina 156

Comentarios a estos manuales

Relacionado con productos y manuales para Los Componentes Del Dispositivo De Seguridad Siemens SITRANS P