Rosemount 1495, Руководство по установке и эксплуатации

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Reference Manual
00809-0100-4792, Rev CA
August 2010
Rosemount 1495, 1496
B-2
NOTE 1
The minimum straight lengths required are the lengths between various fittings located upstream or downstream of
the orifice plate and the orifice plate itself. Straight lengths shall be measured from the downstream end of the
curved portion of the nearest (or only) bend or of the tee or the downstream end of the curved or conical portion of
the reducer or the expander.
NOTE 2
Most of the bends on which the lengths in this table are based had a radius of curvature equal to 1.5D.
a S is the separation between the two bends measured from the downstream end of the curved portion of the upstream end to the upstream end of
the curved portion of the downstream bend.
b This is not a good upstream installation; a flow conditioner should be used where possible.
c The installation of thermometer pockets or wells will not alter the required minimum upstream straight lengths for the other fittings.
d A thermometer pocket or well of diameter between 0.03D and 0.13D may be installed provided that the value in Columns A and B are increased to 20
and 10 respectively. Such an installation is not, however, recommended.
e Column A for each fitting gives lengths corresponding to “zero additional uncertainty” values (see 6.2.3).
f Column B for each fitting gives lengths corresponding to “0.5% additional uncertainty” values (see 6.2.4).
g The straight length in Column A gives zero additional uncertainty; data are not available for shorter straight lengths which could be used to give the
required straight lengths for Column B.
h 95D is required for Re
D
> 2 x 10
6
if S < 2D.
Diameter
Ratio,
Upstream (inlet) side of orifice plate
Concentric
reducer 2D to D
over a length of
1.5D to 3D
Concentric reducer
0.5D to D over a
length of D to 2D
Full bore ball
valve or gate
valve fully open
Abrupt symmetrical
reduction
Thermometer pocket
or
well
c
of diameter

0.03D
d
Fittings (columns 2
to 11) and the
densitometer
pocket
1 9 10 11 12 13 14
-- A
e
B
f
A
e
B
f
A
e
B
f
A
e
B
f
A
e
B
f
A
e
B
f

0.20 5
g
6
g
12 6 30 15 5 3 4 2
0.40 5
g
12 8 12 6 30 15 5 3 6 3
0.50 8 5 20 9 12 6 30 15 5 3 6 3
0.60 9 5 26 11 14 7 30 15 5 3 7 3.5
0.67 12 6 28 14 18 9 30 15 5 3 7 3.5
0.75 13 8 36 18 24 12 30 15 5 3 8 4
Table B-2. Permitted range of straight lengths between an orifice plate and a 19-tube bundle flow straightener
(1998) downstream of fittings located at a distance, L
f
, from the orifice plate
Values expressed as multiples of internal diameter, D
Diameter
Ratio,
Single 90° bend
b
Two 90° bends
b
in perpendicular planes
(2D

S)
a
Single 90° tee
30 > L
f

18 L
f

30 30 > L
f

18 L
f

30 30 > L
f

18 L
f

30
1 2 3 4 5 6 7
-- A
c
B
d
A
c
B
d
A
c
B
d
A
c
B
d
A
c
B
d
A
c
B
d

0.20 5 to 14.5 1 to n
e
5 to 25 1 to n
e
5 to 14.5 1 to n
e
5 to 25 1 to n
e
5 to 14.5 1 to n
e
1 to 25 1 to n
e
0.40 5 to 14.5 1 to n
e
5 to 25 1 to n
e
5 to 14.5 1 to n
e
5 to 25 1 to n
e
5 to 14.5 1 to n
e
1 to 25 1 to n
e
0.50 11.5 to
14.5
3 to n
e
11.5 to
25
3 to n
e
9.5 to
14.5
3 to n
e
9 to 25 1 to n
e
11 to 13 1 to n
e
9 to 23 1 to n
e
0.60 12 to 13 5 to n
e
12 to 25 5 to n
e
13.5 to
14.5
5 to n
e
9 to 25 1 to n
e fh
7 to n
e
11 to 16 1 to n
e
0.67 13 7 to n
e
13 to
16.5
7 to n
e
13 to
14.5
7 to n
e
10 to 16 5 to n
e f
8 to n
e
11 to 13 6 to n
e
0.75 14 8 to n
e
14 to
16.5
8 to n
e f
9.5 to n
e
12 to
12.5
8 to n
e f
9 to n
e
12 to 14 7 to n
e
Recom-
mended
13 for

0.67
13 for

0.75
14 to
16.5 for

0.75
14 to
16.5 for

0.75
13.5 to
14.5 for

0.67
13.5 to
14.5 for

0.75
12 to
12.5 for

0.75
12 to
12.5 for

0.75
13 for

0.54
13 for

0.75
12 to 13
for

0.75
12 to 13
for

0.75

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