Installation, Operation & Maintenance Manual Merlin Detector i-S
Iss: 1 170322
4
Installation
Typical Application & Location
Installation must be carried out by a licenced, insured contractor!
Ensure that detectors are not exposed to liquid or dust contamination!
Detectors and cables must be protected against mechanical damage!
Avoid conditions of any other environmental factors outside of the specification that could potentially impede the accuracy
and operation of the detector such as condensation; vibration; temperature, pressure, the presence of other gases,
electromagnetic interference, and draft zones!
The target gas will only be identified when contact is made with the sensing element itself!
Gas detectors should be installed in areas at risk of gas leaks e.g., near boilers, valves, or meters, located in positions
determined by those who have knowledge of gas dispersion, the process plant system and equipment involved, and
in consultation with both safety and electrical engineering personnel.
Take in to account the design of the air flow patterns within the area. Detectors should be installed in the correct
orientation, as recommended, and ease of access should be accounted for to allow for any bump tests and other
forms of maintenance throughout its operating life.
There are no official figures of the area coverage of a gas detector; however, 50m
2
per detector is a reasonable
general guide therefore multiple detectors may be required to adequately protect property and persons.
There are no specific standards governing gas detector location (unlike fire detection systems); there are, however,
general guidance documents. The most relevant being
IEC 60079-29-2: Explosive Atmospheres
–
Part 29: Gas
detectors
–
Selection, installation, use and maintenance of detectors for flammable gases and oxygen
. Much of what it
covers is also relevant to toxic gas detection.
Recommended heights may vary based on air flow and temperature conditions in addition to the proposed application
and location. Locations for detectors will vary based on the intended application and target gas, they should be
located near identified sources of a potential gas leaks/pockets where gas could quickly accumulate and areas of
identified consequential risk to detect gas. The composition of the target gas and its density relative to air are used as
the basis for the recommended height of sensors. Generally, the installation height of a sensor for a heavy gas (such
as propane) would be close to the lowest point in the area, and for a light gas (such as methane) would be close to
the highest point in the area.
These typical positions may vary based on air flow and temperature conditions in addition to the proposed application
and location
–
this is particularly apparent with oxygen depletion sensors, and the target gas that they are used for.
Target Gas
Typical Position
Natural Gas/Methane (NG)
High Level - 300mm (1ft) from ceiling
Liquid Petroleum Gas (LPG)
Low Level - 300mm (1ft) from ground level
Carbon Monoxide (CO)
Breathing Zone - 17
00mm (5ft 6”) from ground level
Carbon Dioxide (CO
2
)
Breathing Zone -
1700mm (5ft 6”) from ground level
Hydrogen (H)
High Level - 300mm (1ft) from ceiling
Nitrogen Dioxide (NO
2
)
Low Level - 300mm (1ft) from ground level.
Oxygen (O
2
)
*Breathing Zone - 1000-1500mm (3 - 5ft) from ground level
* If you are installing and monitoring oxygen depletion monitors
–
consider the density of gas for its application and
position the detector accordingly i.e., ground level for high density gases.
Detectors should be mounted where a potential hazard of gas is most likely to be present. The following points should
be noted also when locating gas sensors. When locating detectors consider
•
The possible damage caused by natural events e.g., rain or flooding.
•
Ease of access to the gas detector for functional testing and servicing.
•
How gas may behave due to natural or forced air currents.
