Technical Manual Page 11 CODEL
OPS.080 Issue : C Rev. : Date : 16/7/08 Doc. i/d : 0080/6 Ref. : 080040
4. Installation
PLEASE BE SURE TO READ SECTION 3. Preparing for Installation BEFORE PROCEEDING
Installation of the several units that make up a 4000 Series analyser may be carried out in any order. However,
the recommended order, reflected in this manual, is:
- Selection of measurement position
- Installation of the stub-pipe and mounting flange
- Installation of purge air supply
- Fitting of transceiver
- Installation of GCU and CDC
- Installation and connection of cables
- Installation of normalising measurements and input connections to the GCEM4000
- Installation of span verification gases
4.1. Selection of Measurement Position
This analyser measures the average concentration of gas across a significant proportion of the width of the
stack or duct. Measurement position is therefore not as critical as with single point measuring systems, where
consideration must be given to ensuring representative results. Nevertheless, positions where significant
stratification might occur are best avoided. On most combustion plant, flue gas homogeneity can be guaranteed
after the ID fan, so from this point of view, the selected position could be anywhere in the ductwork after the ID
fan or in the stack.
The next factor to consider is that of flue gas pressure. Choosing a position where the flue gas is at negative
pressure, compared with ambient pressure, is not as important as it is for conventional open path cross-duct
analysers. However, it is advantageous in reducing pressure and flow requirements, to ensure complete
flooding of the measurement cell, of both zero and calibration gases. Under normal operating conditions
negative flue gas pressure exists from 10-15m after the ID fan outlet to stack exit. If possible, open any existing
port near the selected measurement position to confirm.
Take care in doing this. Use suitable protective clothing, including eye protection. Positive
pressure in the duct will cause hot flue gases to be vented from the open port.
Take care also to ensure that duct vibration at the selected mounting point is kept to a minimum. Severe
vibration may cause malfunctioning of the instrument or at worst a catastrophic failure of the duct. Take in to
consideration the total weight of the instrument when selecting the mounting position and the effect that this may
have on duct vibration.
The final factors to be considered in selection of measurement position are those of convenience and cost of
installation. Access from existing platforms or walkways and proximity of existing services are obvious
advantages, both for installation and subsequent commissioning and servicing. Drilling holes in metal ductwork
or flues is easier than drilling concrete stacks. Also ensure that there is enough space between the duct or stack
and any other obstruction to allow installation of the transceiver and probe. A minimum clearance of 2.25m is
required from the mounting flange. Ensure that there is space to manoeuvre the tube in to position ready for
insertion (see Figure 9).
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