Yokogawa PK200 - Manual (Page 30)

IM 21B03D01-01E A-2
Appendix A. AIR SUPPLY SYSTEM
(2) Example for Field-Mounting Instru-
ments
Figure 2 shows an air-supply system for service point
with respect to field-mounting instruments (individu-
ally installed instruments).
Securely install a filter and reducing valve in air supply
piping that is nearest to an instrument. (These devices
are not required if the instrument has a filter and
reducing valve.)
Also, it is recommended that a shut-off valve be
installed in the air supply pipe to allow removal of
individual instruments without cutting off the entire air
supply system.
F0A02.EPS
Air supply pipe
Shut-off valve
Air header pipe
Air filter
Supply Regulator
Unregulated air supply
Samp
To instrument
Figure 2 Example of Air Supply System (for Field-
Mounting Instruments)
(3) Air supply System for Field-Mounted
Instruments
• Supply Air
Clean, dry air is required. An aftercooler, filter, air
drier are used to eliminate water, oil, and other
contaminants.
• Air Supply Header (Air Header)
The air header that supplies air to a series of
instruments is installed with a minimum downward
pitch of 10 mm/m (1/100) so that moisture and oil
entrapped in the header can be discharged.
• Air Supply Piping
An air supply pipe connected to an instrument is
branched from the upper part of an air header to
prevent moisture entry. Even if this is not possible,
an air supply pipe should be branched from the side
of the air header, i.e., it must not be branched from
the bottom part of the header.
It is recommended that an air supply pipe be
provided with a shut-off valve so that individual
instruments can be removed.
• Air Filter
A filter removes moisture, oil, and other contami-
nants that cannot be removed by the main air supply
system. In general a cock installed at the bottom of
a filter is opened to discharge moisture, oil, and
other contaminants. If the amount of moisture and
oil is large, increase the number of draining times.
The above-noted methods and units are an example and
there are other various methods and units. Use a
method and units suitable for the process type to
supply clean, dry air to instruments.