Mounting and commissioning
22
Bourdon tube, capsule, diaphragm, spring diaphragm pressure gauges
Preparing mounting
The pressure gauge must be mounted in such a way that it is not
subjected to shocks and vibrations.
The pressure gauge must be easy to read. Avoid parallax errors
when reading the pressure gauge.
In order to obtain a position of the pressure gauge that allows for
easy reading, threaded connections should be made by means of a
female/female connection or a union nut.
Arrange the pressure gauge in such a way that the operating tem-
perature never exceeds or falls below the permissible values. Ac-
count for the influences of possible convection or heat radiation.
A height difference between the pressure tap piece and the pressure
gauge causes a shift of the initial value if the fluid in the measuring
line does not have the same density as the ambient air.
The shift of the initial value
∆
p = 10 - 5 (
ρ
M -
ρ
L)
•
g
•
∆
h [bar]
(
ρ
M-
ρ
L)
= Difference in density
ρ
M
= Density of measured fluid
[kg/m³]
ρ
L
= Density of air (1.205 at +20 °C)
[kg/m³]
g
= Gravitational acceleration (mean
value 9.81)
[m/s²]
∆
h
= Height difference
[m]
The displayed value is reduced by ”p if the pressure gauge is at a
higher level than the pressure tap piece, it is increased by ”p if the
pressure gauge is at a lower level.
If a static liquid column acts on the pressure gauge, verify cor-
rect adjustment of the pressure gauge and ensure that the ad-
justment is shown on the dial.
If the pressure gauge is at a lower level than the pressure tap
piece, flush the measuring pipe prior to commissioning in order
to remove external matter.
It is advisable to install a shut-off unit to facilitate the disassembly of
the pressure gauge for maintenance purposes, see chapter 9.1,
page 33.
Bourdon tube pressure gauges with measuring ranges of d 25 bar
have a pressure relief opening (blow-out) at the top of the housing.
These pressure gauges have appropriate warning labels fitted. For
liquid filled gauges with lateral connection, special housings are used
and the pressure relief opening (blow-out) is located at the top of the
housing with the gauge in its installed position.
