Selection criteria
Bourdon tube, capsule, diaphragm,
spring diaphragm pressure gauges
11
4.1
Range
Select the range in such a way that the maximum pressure load
does not exceed 75 % of the full scale value in the case of static
load and 65 % of the full scale value in the case of dynamic
load. This prolongs the service life of the pressure gauge (see
EN 837-2).
4.2
Properties of the media
Pressure surges
Pressure surges must not exceed the application range of the pres-
sure gauges. The measuring element must not be subjected to pres-
sure surges or sudden pressure changes. Such changes considera-
bly reduce the service life of the pressure gauge. For example, such
changes occur if the pressure gauge is mounted to a pump, as indi-
cated by major oscillations of the pointer.
Reduce such pressure surges by installing a damper or an over-
load protection device between the pressure source and the
elastic measuring element.
Throttle elements considerably reduce the inlet cross section which
leads to a delay of the pressure change in the measuring element.
The susceptibility to dirt is a disadvantage of such arrangements.
Damping elements at the movement delay the pointer motion and
cause increased wear of the movement.
Liquid filling cause a damping of the measuring element and de-
creases the wear of the moving parts.
Excessively high temperatures of the fluid in the case of Bour-
don tube pressure gauges
Install a siphon (see chapter 9.3, page 34) or a chemical seal
(see chapter 9.4, page 34) to help protect the pressure gauge
from the hot fluid.
In the case of capsule type pressure gauges and spring diaphragm
pressure gauges, the temperature of the fluid must not exceed the
permissible operating temperature.
Corrosive media
Standard pressure gauges may be used if corrosive media can be
kept away from the measuring device by means of separating ele-
ments. If this is impossible, the material most suitable for the fluid to
be measured and its pressure must be selected.
1.
Provide the manufacturer with all information on the materials
that are compatible with the fluid to be measured under the spe-
cific measuring conditions.
