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Semi-Portable Monitor Technical Specification

Instrument Specification and Design

STS Semi Portable Siloxane Monitor

The STS Semi-Portable monitor is a variant on the fully installed GRP package. The monitor itself is identical to the fixed monitor but it is housed in a more portable wheeled pelicase enclosure. This package lends itself to be moved between sites where shorter term monitoring can be carried out to establish the status of carbon filters. This means that users who may have smaller filters where a permanent monitor may not be so cost effective can now split the cost of the monitor across several sites and gain efficiencies at them all.


STS Instruments - Portable Siloxane Monitor Specification


The STS Siloxane Monitor is CE certified and complies with IGE SR25 requirements.


The Siloxane monitor has the following requirements:

  1. 110V 6A – (IEC rear connector) wired to flex outlet from Distribution box.

  2. N2 carrier gas line: ¼” Nylon/PTFE/SS piping (1/4” Swagelok connector supplied) Set at 1Bar at cylinder regulator Technical Grade 99.999%.

  3. Biogas feed line - ¼” PTFE/SS piping (1/4” Swagelok connector supplied) Maximum 1Bar input pressure.

  4. Vent line - ¼” PTFE/SS piping (1/4” Swagelok connector supplied) Vented ~3m high , end of Line flame arrester to be fitted.


Biogas Flow rates:

The instrument samples approx. 2L of biogas during a 20minute window every 1hour, at a flow of approx. 100ml/min. This is passed through the instrument then vented to atmosphere.


N2 Flow rate:

The instrument consumes approx. 4L of N2 every hour. Resulting in 0.1m3 of N2 per day. This is passed through the instrument then vented to atmosphere.

STS recommend using the largest N2 cylinder to avoid regular replacement.

Air Products: X47S: 80kg 200bar 8.9m3. Technical Grade.

Regulator : BOC 8500 or similar, 300Bar inlet , 0-4 bar outlet.

This should last approx. 90days, 3 months.


The water Traps require the following:

  1. Auto drain traps with float activated drain lines on each sample line -powered by 24V supplied from instrument.



The case will has 8 external connections:

  1. Biogas IN 1

  2. Biogas IN 2

  3. N2 IN

  4. Vent OUT

  5. Drain OUT

  6. Data comms Out

  7. 110V supply IN.

Biogas Supply:


Regulated in the kiosk to 35mbar, normal inlet pressure to the regulators should not exceed 350mbar.  If a higher pressure is present, the regulator will require re-specification.


The electrical supply:

A 110V earthed connection is required to the externally mounted switch.



  1. The instrument uses an air purge system to ensure safe operation, this is achieved with 2 high capacity fans mounted in the instrument which force a constant stream of air through the case. The flow of air through the instrument ensures that even in a catastrophic joint failure that the LEL of CH4 would not be exceeded. The purge fans are monitored so that if they are inactive the instrument will be placed into “Safe Mode”


  1. The instrument has an on-board methane sensor which will place the instrument into “Safe Mode” if it exceeds 10% of the LEL.  An on-board temperature sensor will place the instrument in “Safe Mode” if the temperature in the cabinet exceeds 55C. 


  1. Incoming bio-gas lines are controlled by Solenoid valves in the Pelicase which are in the Normally Closed position unless activated, the internal instrument also has a solenoid valve on the incoming biogas line which is Normally Closed, any power failure will therefore close these valves stopping gas flow.  “Safe mode” shuts the incoming gas valves, turns off all heaters and runs the case fans to vent.


  1. The Case itself is force cross ventilated by 2 high capacity fans which draw and purge air through the case.


The Siloxane Monitor & Kiosk is not EX or ATEX rated and as such should be sited outside of any zoned area.

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