Introduction
Manual CWD 2005
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Manual CWD2005.doc
provides a series of removable terminal strips where the 0-20 or 4-20 mA DC isolated
outputs (proportional to the measuring range) and eight user programmable alarm
contacts are available for customer connection. See section 10.2 for details.
The combustion calorimeter is designed to measure very small temperature changes.
When selecting a suitable location, avoid dusty areas, locations with strong drafts,
rapid temperature changes, direct sunlight or other sources of thermal radiation.
T
RE
- 7°
C
<
T
R
<
T
RE
+ 7°
C
where
hour
C
dt
dT
R
2
T
R
Room temperature
T
RE
Room temperature during calibration
2.2.
Available measurement ranges
Normally 40 - 100 % of the full- scale range can be utilized depending on the gas
composition. The measurement range can be wider for gases with a very high flame
speed and the analyzer is designed for a second measuring range, which can be
supplied as an option. This dual range option can extend the measurement range
from 20 to 100 % and moving from one measuring range to the next provides a step-
less transition, and is displayed as one continuous output. Two calibration gases are
required for the dual range option. If one calibration gas is in the transition zone from
one measuring range to the next, a single calibration gas can be sufficient for both
measuring ranges. This must be tested on an application basis by the factory.
Measuring ranges that are too far apart or contain vastly different components can
only be combined into a single measuring range under very specific circumstances.
Another more radical triple range option is available for process gas streams with
very wide ranges. A carrier gas option can provide a usable range of 0
–100%
displayed as one continuous output (a continuous supply of Natural Gas or Hydrogen
is required for this option).
2.3.
Response times
Dead time
3 sec
50% time
7 sec
90% time
20 sec
99% time
45 sec
Response times are measured when the new gas reaches the burner and the values
shown above were measured using Methane. Gases with other specific gravities and
flame speeds generate different response times, some faster and some slower,
depending on the properties of the gas. In addition to the dead time and response
time, the sample lag time for the flow of sample gas through the supply tube and
fittings installed upstream of the unit must be added. The gas consumption is based
on the total sample volume up to the burner and by using the formula in section 3.3 it
is possible to calculate the total installed response time. A fast loop is recommended
on long sample lines, see section 4.5.4.