Cleaning and liquid contact with solids – Processes – Hollow work – internal surface treatment
Patent
1988-10-26
1990-12-04
Pal, Asok
Cleaning and liquid contact with solids
Processes
Hollow work, internal surface treatment
134 2218, 1510407, 15316R, B08B 312, B08B 500
Patent
active
049746170
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a process making it possible to remotely clear or unblock a liquid-filled pipe, as well as to an appartaus for performing this process.
In numerous industrial installations, particularly in the chemical and nuclear industries, there are pipes in which solid particle-containing liquids circulate. These particles create deposits on the walls of the pipes and frequently lead to the formation of plugs.
When the plug has formed in an accessible part of the pipe, the disintegrating of the plug can be brought about by introducing a mechanical member, generally called a ferret into the pipe. However, this method cannot be used when the plug has foamed in an inaccessible part. Moreover, in the nuclear industry, it is not satisfactory because it leads to a direct contact between the clearing member and the generally radioactive products contained in the pipe.
Another known clearing or unblocking method consists of pressurizing the blocked part of the pipe, by directly connecting the latter to the discharge orifice of a test pump. Although this method does not suffer from the disadvantages of mechanical clearing, it sometimes leads to the reverse effect from that which is desired. Thus, in certain cases, the pressurizing of the pipe has the effect of compressing the plug, which makes it virtually impossible to clear by known methods.
The present invention relates to a novel process making it possible to remotely clear a liquid-filled pipe, no matter what the location where the plug has formed and without any risk of compressing said plug.
To this end and according to the invention, a process for the remote clearing of a liquid-filled pipe is proposed, which is characterized in that to one end of the pipe is applied harmonic-rich longitudinal pressure waves at an exciting frequency f.sub.e equal to the natural frequency (harmonic 1) of the incompressible mode of the system, in such a way that the harmonic n of said frequency is at the natural frequency (harmonic 1) of the compressible mode of the system, n being an integer at least equal to 1.
This adaptation of the compressible and incompressible modes is obtained by varying the compliance of the liquid-pipe system.
Preferably, the pressure waves used are formed by low frequency, periodic, harmonic-rich pulse trains (frequency preferably below 20 Hz).
The compliance of the system is regulated in such a way that the harmonic 1 of the resonant frequency of the incompressible mode has a harmonic of frequency equal to the frequency of harmonic 1 of the resonant frequency of the compressible mode. In this case, the ratio between the duration I of a pulse and its period T is adjusted to a value for which the coefficient of the harmonic 1,2 or 3 of the development in the Fourier series of the pulse train is at a maximum.
The invention also relates to an apparatus making it possible to perform the remote clearing process as defined hereinbefore.
According to the invention, said apparatus comprises a clearing jack, whereof one chamber can be connected to the pipe, said jack having a piston performing a reciprocating movement which is imparted thereto by a motor jack, via a mechanical link, said movement having the effect of producing pressure waves in the system, the motor jack being supplied by a hydraulic pressure source, via a servovalve controlled by a regulator sensitive to the output signals supplied by at least one transducer connected to the motor jack and input signals supplied by a signal generator, in order to give the pressure waves in the chamber of the clearing jack the form of harmonic-rich waves.
In order to permit the regulation of the compliance of the pipe, said apparatus also comprises a regulatable compliance device communicating with the chamber of the clearing jack.
According to another aspect of the invention, in order to avoid any risk of the pipe bursting or fracturing, safety means are provided for interrupting the supply of the motor jack when a detector sensitive to the pressure in the chamber of the c
REFERENCES:
patent: 2351163 (1944-06-01), Thomas
patent: 2560728 (1951-07-01), Lee
patent: 4645542 (1987-02-01), Scharton et al.
Cogema (Compagnie Generale des Matieres Nucleaires)
Pal Asok
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