Thermal measuring and testing – Leak or flaw detection
Patent
1982-04-06
1985-08-13
Goldstein, Herbert
Thermal measuring and testing
Leak or flaw detection
374142, 340605, G01M 300
Patent
active
045346623
DESCRIPTION:
BRIEF SUMMARY
The present invention is with respect to a device for detecting steam leaking from hollow bodies, more specially pipes.
The invention is more specially important for keeping a watch on superheated steam ducts, more specially in nuclear power plant. In the prior art, there have been three ways of doing this so far: all the time and without danger, in nuclear plant, to those inspecting. detected and changes in pressure caused by other effects than leaks give a false alarm. However, the radio activity of the steam is not constant so that false alarms are produced. Furthermore, this method is not very sensitive.
The present invention is based on the fact that the development of the start of a sub-crititcal steam pipe crack into a full burst takes a long time, for example 60 minutes, long enough for shutting down the steam pipe in danger. However, it is necessary to have some way of quickly detecting the start of a cracking process, which will be marked by the leaking of steam out of the pipe.
The purpose of the invention is to make this possible. Furthermore, false alarms are to be stopped as far as possible.
This purpose is effected by the invention as made clear by the following description and claims.
In the invention two different physical effects are measured, namely on the one hand a leaking of steam out into the measuring space and on the other hand a temperature drop in the same. On steam under gage pressure in the pipe or other hollow body making its way out through a leak, there will be expansion and a fall in temperature of the steam, the degree of such a temperature drop giving a certain and safe measurement. By measuring the two different effects, it will generally not be possible for false alarms to be produced, the device only producing an output signal, such as an alarm signal, on the two effects taking place at the same time.
The useful effects of the invention are: full-time monitoring of the system. Monitoring may be undertaken from a great distance away so that there is no danger to workers. Furthermore, low rates of leaking may be safely detected. Because of the high sensitivity, sub-critical leaks may be detected so early on that there is enough time for shutting down the part of the plant in question, that is to say it is not necessary for the plant to be very quickly shut down as an emergency in a power plant for example. The device is low in price and upkeep is simple.
Using the further development of the invention, the position of a leak may be made out without any trouble so that, once the fact that a leak is present has become clear, the discovery of its position without much time being necessary for looking for it will be possible.
Using the still further development of the invention, a number of measuring points may be spaced out along each length so that near each point, at which a leak is likely, there will be at least one measuring point. Having a number of like measuring feelers on each length makes operation safer. Furthermore, a reading is quickly produced.
The system is very simple and, for this reason, low in price.
A further development gives a high reading sensitivity and makes it possible for the position of damage to be made out.
Further with respect to different feelers for temperature and steam, all give a sensitive and quick reading.
An account will now be given of embodiments of the invention using the figures.
FIG. 1 is a perspective view and part axial section of a coaxial form of steam detector.
FIG. 2 is a view on the same lines of a steam detector in the form of a with parallel electrodes and a steam inlet pipe next thereto
FIG. 3 is a view of a further form of a steam detector as in FIG. 2.
FIG. 4 is a perspective view of a piece of steam piping with parts of two insulating cases, a temperature feeler and two steam detectors.
FIG. 5 is a view of other steam detectors, the general system being in other respects as in FIG. 4.
FIG. 6 is an exemplary warning instruments.
In the embodiments of FIGS. 1 and 2 there is, in each case, a housing 2 having a pipe 4, the
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