Shaw SDHmini - Piping Schematic Component Index; Purging the Sample Connection

3.4 Piping Schemac Component Index
Sample Isolaon Valve - This is a recommended item as it allows access to
the sample system without interrupng the main process line.
Filter Unit – A lter unit is recommended when the samples are likely
to contain parculate maer. If the air/gas sample contains heavy
hydrocarbon condensate, the lter must be of the coalescing type with a
drain. The lter unit should be posioned as close to the sample point as
praccal.
Sample Tube – This should be stainless steel for dry air or gas applicaons
but copper or carbon steel can be used where weer gases are to be
measured. If any secon of the sample tube must be exible then PTFE
should be used. In most cases, 3 mm OD (⅛”) is sucient as it provides
good system response me with minimum ow. 6 mm OD (¼”) tube can
be used where pressure drops across the 3 mm tube are too high.
Pressure Reducon Valve or Pressure Regulator – the sample is measured
at atmospheric pressure requiring that valve 4 is ed to the system.
Flow Control Valve.
Sample Connecon.
SDHmini.
Flow Indicator – The recommended sample ow is 2 to 5 L/min.
Sample Exhaust – The exhaust is vented to atmosphere or returned to an
atmospheric pressure line.
3.5 Purging the Sample Connecon
Refer to the Piping Installaon Schemac in secon 3.3.
It is advisable to carry out an inial purge of the sample loop without connecng
the instrument, in order to avoid the possibility of sensor damage on start-up.
Open the sample isolaon valve (1) slowly, unl there is a small ow of air/gas at
atmospheric pressure from the pressure reducon valve (4). Allow the air/gas to
exhaust through the sample connecon (9).
Connue this for two minutes to remove any residual moisture from the sample
pipe work and components. Check that no liquid or parculate contaminaon,
which could damage the sensor, is passing through the sample pipe. Direcng the
sample onto a piece of white paper (such as a lter paper) will make it easier to
see any dust or oil mist in the sample.
1.
2.
3.
4.
5.
6.
7.
8.
9.
9