Page
10 D-LX
100
7.5. D-ZS 087-20 Digital Display Unit
By connecting the D-ZS 087 display unit, the flame intensity can be displayed as a pulse signal, from
0 - 4095 pulses. Furthermore, the minimum and maximum values are stored, and the thresholds for
the flame ON and flame OFF ranges are calculated. This allows the operator to determine the optimal
threshold between ambient light (relay must remain in the OFF position) and flame (relay must remain
in the ON position, even if flame intensity is minimal).
8. Safety Time
The safety time is the response time of the flame scanner to the outage of the flame signal (pulse
frequency of the integrated flame scanner) and the resulting shut-off of the relay contact for the flame
ON signal.
The D-LX 100 has a standard safety time of 1 s. Safety times of 3 and 5 s are available upon request.
Should the safety time need to be changed, the following steps must be followed:
9. Integrated Flame Scanner
In order that the flame scanner can be used in burner applications with the widest variety of fuels, 3
UV and 2 IR flame scanner models are available. All flame scanners with a semiconductor photo
element have the same electronic shutter in common. The scanners use this shutter to perform a
continuous check of the internal signal amplifier and filter. The signal amplifier can be set to one of
two levels. Amplification level V2 is higher than V1 by a factor of three. The scanner comes from the
factory having been set to V2.
DURAG also offers a UV flame scanner with a UV photocell. For performing self-checks, the scanner
is equipped with a newly developed, long-lasting shutter which interrupts the path to the photocell.
Because of the way the UV cell operates, it is not possible, or required, to switch from one
amplification level to another since no saturation will occur.
9.1. Ultraviolet Flame Scanner
The UV zone of a flame is in general considerably smaller than the IR zone. Moreover, boiler walls
and components do not radiate any dynamic UV energy. UV flame scanners are therefore very
selective and not sensitive to ambient light.
The D-LX 100 UL uses a photocell with a spectral sensitivity of
λ
= 185 nm to 260 nm. Because this
spectral range is so narrow and distant from that of daylight, it is permissible to evaluate both the
dynamic and static energy of the flame. This important advantage makes the D-LX 100 UL a highly
sensitive flame scanner, with excellent selectivity for all flames releasing energy in the UV-C range,
e.g., gas and oil flames.
A semiconductor photo element with a spectral sensitivity of
λ
= 190 nm to 520 nm is employed in the
D-LX 100 UA. The integrated flame scanner acquires the dynamic blue-to-transparent range of gas,
oil and coal flames, without suffering signal collapse due to water vapor, recirculation gas or similar
UV-absorbing gases.
In the D-LX 100 UAF, the photo element from the D-LX 100 UA is used with a filter. Because of this
filtering, a reduced spectral range of
λ
= 280 nm to 410 nm results. This delivers better results in
cases of very intense UV radiation or if higher selectivity is required.
Note:
in the visible spectral
range the filter does not appear transparent—it appears black to the human eye. The photo element
is, however, visible through the lens of the flame scanner.