SGB VL 230, Документация

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APPENDIX W
VACUUM
LEAK DETECTOR VL ..
20/07/2010 - W-1 -
Using the VL .. underpressure leak detector on tanks which have been allowed to
warm up
The following example applications are described in this appendix:
W.1: Tank for storing liquids which are viscous or have a tendency to solidify at ambient tem-
perature (temperatures >50°C and <150°C), and where a sufficient length of the measu-
ring line has been routed inside the tank insulation, or for tanks used to store liquids
which remain thin at ambient temperature.
W.2: Tank for storing liquids which are viscous or have a tendency to solidify at ambient tem-
perature (temperatures >50°C and <150°C), and where only a short length of the mea-
suring line has been routed inside the insulation.
W.3: Tanks which are filled with hot product quickly; in other words, the temperature of the
filled product is more than 25°C higher than the temperature of the tank (worst case
scenario), introducing the risk of false alarms.
The design and dimensioning of the leak detector for a heated tank (chapters W.1 and W.2) is
significant on account of the temperature resistance of the leak detector components used. In
these applications, either a sufficient cooling section or a system of leak sensors in conjunction
with solenoid valves (instead of a liquid stop valve) needs to be used in order to ensure that
alarms will be triggered correctly.
Tanks which are filled with hot products (chapter W.3) experience a change in temperature in
the interstitial space and therefore a change in pressure (drop in underpressure). False alarms
which might be triggered due to this rise in pressure need to be avoided if at all possible.
Both aspects can even be significant simultaneously (particular care must be taken to monitor
the leak detector system especially when heating or filling a tank for the first time)
1
.
The interstitial spaces of the above tanks should be dry prior to starting up the leak detector (if
they are not, they should be dried in order to ensure that the leak detector will function correct-
ly).
W.1 Tanks with heating (and insulation) at temperatures > 50°C and < 150°C (de-
sign with cooling section)
(1) This design requires that the parts of the interstitial space which are used for pressure re-
duction
2
are sufficiently heated or that the product inside the tank remains sufficiently thin
at ambient temperature.
(2) Check whether special switching values might be necessary (see W.3).
(3) A cooling section approx. 3 m in length (spiralled pipe) is installed between the mounting
set and the liquid stop valve in order to prevent impermissible increases in temperature at
the liquid stop valve. In most cases the liquid stop valve is then installed underneath the
leak detector.
(4) Metal pipes have to be used for reasons associated with temperature.
W.2 Tanks with heating (and insulation) at temperatures > 50°C and < 150°C (de-
sign with sensor in suction line)
(1) Check whether special switching values might be necessary (see W.3).
1
Cases have even been known of overpressure caused by heat rise, introducing the risk of damage to
the interstitial space.
2
Volume displacement in the event of a liquid leak in the interstitial space/measuring line.