Fluid handling – With cleaner – lubrication added to fluid or liquid sealing... – Cleaning or steam sterilizing
Reexamination Certificate
2000-06-01
2002-12-31
Walton, George L. (Department: 3753)
Fluid handling
With cleaner, lubrication added to fluid or liquid sealing...
Cleaning or steam sterilizing
C073S029010, C073S029020, C134S094100, C134S098100, C134S099100, C134S16600C, C134S171000, C137S015040, C137S597000, C141S004000, C141S066000, C141S089000
Reexamination Certificate
active
06499502
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject of the present invention is a method and a device for filling a distribution line with corrosive gas. The subject of this invention is more specifically a method and its associated device for filling with gas, with passivation, a line for distributing corrosive gas; the said line being intended to distribute the said corrosive gas to a system located immediately downstream of this line and the said corrosive gas being capable of passivating it.
2. Description of the Related Art
The technical problem of obtaining good passivation of such corrosive-gas distribution lines with a view to, on the one hand, obtaining effective protection against corrosion of the said lines and of the said system supplied with the said gases by the said lines and, on the other hand, distribution of ultra-pure corrosive gases, is known to those skilled in the art.
To date, no truly satisfactory solutions to the said technical problem have been proposed (in particular, there are still problems with corrosion in the line and in the downstream equipment); the operation of filling with gas conventionally being performed in the following successive steps:
a first step of conditioning the line: this first step comprises at least one purge and a leak test. It generally comprises successive sequences of purging using one and the same inert gas, one and the same mixture of inert gas or several gases or mixtures of inert gases so as:
to eliminate impurities, particularly water, adsorbed onto the interior wall of the line (the said water accelerating corrosion in the presence of corrosive gas);
to check the tightness and integrity of the said line using conventional methods known to those skilled in the art;
and possibly, to analytically monitor the integrity parameters of the said line, such as the hygrometry, the oxygen content, the number of particles carried by the purge gas and supplied by the said line (the said purging gas obviously being clean and “free” of water, oxygen and particles).
On completion of this conditioning of the said line, the inert gas (or mixture of inert gases) contained therein is or are removed (purged). The said inert gas (or mixture of inert gases) is or are generally pumped, to remove it, via the equipment located at the end of the line;
a second step of filling the said line with active gas: the line is filled with the active (corrosive) gas. The said gas is thus made available to the equipment.
The amount of active gas introduced into the said conditioned line for filling the said line with gas (for the “first fill” of the said line with the said active gas) is thereafter generally left in this line and then, when the said line enters service, delivered downstream into the equipment to supply the said equipment with active gas. This amount of active gas, although limited but not in any way negligible, and in any event proportional to the length and square of the diameter of the line concerned, may be referred to as the priming, start-up, or “going live” quantity.
The Applicant should be given due merit for having clearly established, in a way which was not obvious, that this amount of active gas used for filling the line with active gas, and more generally the initial quantities of active gas delivered, were liable to generate the corrosion problems mentioned hereinabove and that this was true regardless of the rigour with which the prior conditioning of the said line was performed. Specifically, the Applicant has clearly established (see
FIG. 2
appended to this description) that the corrosive gas, in generating the passivation layer from the surface layer of oxides in the said line during its “first passes” down the line, also generates water, the said water making the said gas more corrosive and being liable, on the one hand, to detract from the formation of the said passivation layer and, on the other hand, to adversely affect the said passivation layer formed. Thus, regardless of the rigour of the prior conditioning, with reference to the hygrometry parameter, there is always the in situ generation of water after the said conditioning. For example, on the interior walls of a steel or iron pipe there is inevitably contact between gaseous HCl (corrosive gas) giving rise to the following chemical reaction:
Fe
2
O
3
+6HCl→2 FeCl
3
+3H
2
O.
Reactions of this type, known per se, were never alluded to within the particular context of the filling of distribution lines with corrosive gases. It is to the Applicant's credit that the link has been established.
In the context of the present invention, the Applicant therefore recommends limiting the harmful effects of the water generated in situ during the formation of the passivation layer as far as possible. To this end, it recommends an original and particularly effective (from the point of view of the desired passivation and the corrosion caused) method for filling a distribution line with corrosive gas; the said line being intended to distribute the said corrosive gas to a system (generally an item of equipment) located immediately downstream of the said line. The components of the said system will be all the more reliable (in other words, the risk of the system malfunctioning will be all the lower) if the aggressiveness of the gas has been minimized, and if the presence of water within the said gas has been minimized.
The said line supplies the said system with the said gas directly. Its supplies the said gas to the inlet of the said system. The whys and wherefores of locating the system that is to be supplied with gas immediately downstream of the line will be understood from studying the considerations hereinabove about the methods of conditioning, and from the description hereinbelow of the method of the invention. In effect, the issue is obviously not one of carefully preparing a line “far” upstream of the system that is to be supplied so as to then use the said prepared line and an extension thereof or some other line, which has not been prepared, immediately upstream of the said system for supplying this system. The problems mentioned hereinabove would inevitably be encountered in the unprepared part, and this would, just as inevitably, cancel the effects of the preparation in the portion “far” upstream.
SUMMARY OF THE INVENTION
The method of the invention is thus generally performed on the entire active-gas distribution system. It may, however, obviously be performed only on part of this system, in instances where a new line or an extension of a line is or are added to a network, the upstream part of which has already been “treated” within the meaning of the invention.
The method of the invention comprises, in succession, the conventional steps of the method of the prior art, namely:
prior conditioning of the said line (conditioning as described in the introduction of the present description, on completion of which the said line is dry, clean and empty of any gas);
the actual filling of the said line with the said corrosive gas known as an active gas.
It is characterized by an original way of performing the second of the said steps. Specifically, according to the invention, the said actual filling with gas comprises:
at least one cycle of filling the said line with active gas as far as immediately upstream of the system and of removing the said active gas thus introduced into the said line; the said removal being performed without the said active gas passing through the said system;
followed by the final filling of the said line with gas so as to make the said gas available to the said system.
Thus, characteristically, according to the method of the invention, the first quantity (quantities) of active gas introduced into the said line (at least the said first quantity, referred to hereinabove as the start-up or priming quantity) is (are) removed from the said line without being delivered downstream into the system. The said system is thus spared from any contact, or any reaction with the said water-laden first quantity (quantities) of gas
Duchateau Eric
Girard Jean-Marc
Lefevre Bertrand
McAndrew James
Burns Doane Swecker & Mathis L.L.P.
L'Air Liquide - Societe Anonyme a Directoire et Counseil de
Walton George L.
LandOfFree
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