Shaw SDHmini Bl, Инструкция по эксплуатации

Страница: 9 / 28

3.3 Piping Schematic Component Index
Sample Isolation Valve - This is a recommended item as it allows access
to the sample system without interrupting the main process line.
Sample Tube – This should be stainless steel for dry air or gas
applications but copper or carbon steel can be used where wetter gases
are to be measured. If any section of the sample tube must be flexible
then PTFE should be used. In most cases, 3 mm OD (⅛”) is sufficient as it
provides good system response time with minimum flow. 6 mm OD (¼”)
tube can be used where pressure drops across the 3 mm tube are too
high.
Filter Unit
– A filter unit is recommended when the samples are likely
to contain particulate matter. If the air/gas sample contains heavy
hydrocarbon condensate, the filter must be of the coalescing type with a
drain. The filter unit should be positioned as close to the sample point as
practical.
Pressure Reduction Valve or Pressure Regulator – the sample is
measured at atmospheric pressure requiring that valve 4 is fitted to the
system.
Flow Control Valve.
Sample Connection.
SDHmini.
Flow Indicator
– The recommended sample flow is 2 to 5 L/M.
Sample Exhaust – The exhaust is vented to atmosphere or returned to an
atmospheric pressure line.
4.0 Purging the Sample Connection
Refer to the Piping Installation Schematic in section 3.2.
It is advisable to carry out an initial purge of the sample loop before connecting
the SDHmini, in order to avoid the possibility of sensor damage on start-up.
Open the sample isolation valve (1) slowly, until there is a small flow of air/gas
at atmospheric pressure from the pressure reduction valve (4) into SDHmini line.
Allow the air/gas to exhaust through the sample connection (9).
The SDHmini is not flow sensitive, however, the sample flow needs to be
enough to purge the sensor head effectively, so anything less than 1 litre/min
would mean that the instrument would take too long to settle to a stable
1.
2.
3.
4.
5.
6.
7.
8.
9.
9