JP3140216B2 - Ultra-high purity gas piping equipment and method for measuring particles generated from welds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing particles generated inside an ultra-high purity gas piping at the time of operation thereof and particles such as dust generated from a welded portion at the time of welding of the piping with high precision. The present invention relates to a method for measuring dust particles, which can be easily measured by using the method.

[0002]

2. Description of the Related Art In a plant using an ultra-high purity gas, such as a semiconductor manufacturing plant, a gas pipe is generally formed by using a stainless steel pipe (SUS316L) subjected to electrolytic polishing. For connection, union type joints with special structures (fitting type non-welded joints) are often used. However, the fitting-type non-welded joint has a problem that the structure is complicated and expensive, and gas leakage is apt to occur due to deterioration of the sealing material. Further, in the non-welded joint, there is a problem that a concave portion is unavoidably formed on the inner wall surface of the joint part due to its structure, and the gas replacement property of the pipe is deteriorated, so that it is difficult to obtain high cleanliness. Therefore, in recent years, even in this kind of ultra-high-purity gas piping, connection of pipes by welding is being adopted, and automatic butt welding by a so-called TIG welding method or a special welding joint (for example, a welding collar or the like) is used. Automatic welding methods have been developed.

[0003] In the welding of ultra-high purity gas piping, the mechanical strength of the welded portion and the flatness of the inner surface of the welded portion are of course a problem. Is an essential requirement that it does not become a source of contamination of the pipeline, that is, a source of particles. In other words, in the development of this type of welding method for ultra-high-purity gas piping, in addition to measuring the mechanical strength of the weld and the flatness of the inner surface, the generation of dust particles during welding is easier. In addition, it is necessary to perform the measurement with high accuracy.

In this type of ultra-high-purity gas piping, it is necessary to reduce the number of particles generated when devices such as a control valve provided in the piping system are operated.
For that purpose, it is necessary to be able to easily and accurately measure particles generated from inside the control valve or the like when the control valve is operated.

FIG. 3 shows a conventional method for measuring particles generated from the control valve V. A sampling pipe C of a particle counter E is inserted into a pipe W, and the valve V is opened and closed to open a gas D to be measured. Counts the number of particles emitted to However, in the method as shown in FIG. 3, the flow rate of the gas D to be measured changes with the opening and closing of the valve V, the gas velocity distribution in the pipe W also changes, and the number of particles in a part of the gas D to be measured is reduced. There is a problem that the number of particles cannot be measured quickly and accurately due to the need for correction for measurement and the like.

FIG. 4 shows an example of a conventional method for measuring particles generated from a welded portion of the pipe. The tip of a pipe B downstream of a welded portion A is sampled by a sampling pipe C of a laser particle counter E. By introducing the gas to be measured D emitted from the opening at the tip of the pipe B into the laser particle counter E, particles generated from the welded portion A during welding are counted.

More specifically, the pipe B has an outer diameter of 6.35.
mmφ, 1 mm thick stainless steel tube (SUS316L)
After welding pipe A, pipe B was cut to a certain size with a pipe cutter, and the end face was machined while purging with nitrogen gas at 40 L / min, and then with high-pressure nitrogen gas at 7 to 9.5 kg / cm ² . After purging for 2 seconds, both ends of the pipe are pressed lightly and concentrically butted so that the gap is not visible. The automatic welding apparatus F includes an automatic TIG welding apparatus (CA150P manufactured by Astroark Co., Ltd.).
The welding conditions are as follows: the outer diameter of the tungsten electrode is 1.0 mmφ, the electrode tip angle α = 15 °, the distance between the electrode and the groove is 0.8 mm, the flow rate of the arc gas (argon) is 8 L / min, Shielding gas (argon) flow rate 6 L / min, electrode rotation speed 7.9 sec / rotation, peak current 21 A, base current 20 A, electrode rotation frequency 2.5
Time, the time from the start of the arc to the start of the electrode rotation (delay time) 2 sec, the time from the start of reducing the welding current value to the stop of the arc (down slope time)
Each is set to 4.2 sec. The arc gas (argon) is supplied from the liquefied argon gas container to the automatic welding device through the vaporizer, and is continuously pre-purged at a flow rate of 8 L / min from before the arc start.
Post-purge for 20 seconds after arc stop,
In addition, immediately after setting both stainless steel tubes, the back shield gas (argon) continuously flows inward from the opening at the end of the tubes.
It is released at a flow rate of L / min. Further, the laser particle counter E has a rated suction flow rate of 28.3 L /
min. Hitachi TS-3700 type is used, and the tip of the pipe B downstream from the welded portion A is inserted into a sampling pipe C having an outer diameter of 9.52 mm x a thickness of 1 mm to be measured. Gas D is introduced into sampling pipe C. Note that the laser particle counter E is provided with seven measurement channels (Ch), 0.1 to 0.2 μm for Ch1, and 0.1 for Ch2.
2 to 0.3 μm, Ch3: 0.3 to 0.5 μm, Ch
4 is 0.5 to 1.0 μm, and Ch5 is 1.0 to 2.0 μm.
μm, Ch6 particles and particles of 2.0 μm or more
At h7, the total number of particles was measured.
In addition, the cleanness of welding is 0.1 μm standard class 1
(Particles exceeding 0. 1 [mu] m is 1 ft ³ per
The measurement of particles by the laser particle counter E is started from 5 minutes before the start of welding and continuously performed until 5 minutes after the end of welding, and thereafter, the change of the measurement output is performed. , The output area during the welding time is specified, and the number of particles measured during that time is calculated.

In the measurement of the number of particles, the particles are measured in an atmosphere having an extremely high degree of cleanliness, and the particles are discharged through the rated suction capacity of the particle counter E and the opening at the end of the pipe B. When the flow rate of the gas D to be measured is substantially equal, particles can be measured with relatively high accuracy. However, as shown in FIG. 3, the rated suction capacity of the counter E was 28.3 L /
min (1 cubic foot / m ³ )
Is relatively low at 6 to 7 L / min, the room atmosphere R is sucked into the sampling pipe C through the gap, and the suction state of the gas to the counter E is so-called constant-speed suction. Therefore, the number of particles contained in the room atmosphere R is inevitably counted. Therefore, the flow rate (L / min) of the sucked indoor atmosphere R
In general, a method of calculating the number of particles for the room atmosphere R from the number of particles in the room atmosphere R (particles / m ³ ) and correcting the count value using the calculated number is generally performed. However, with such a method, although the total correction of the count value is possible to some extent, it is impossible to correct the count number for each particle size of the particles, that is, the count number for each channel of the counter E,
There is a drawback that accurate measurement cannot be performed. In addition, in order to perform accurate measurement, it is necessary to maintain the atmosphere R at a considerable purity, and this is subject to many restrictions. In addition, according to the test results, even if the total number of the measured particles is corrected, it is clear that the error actually includes a considerable error, and the difference between the rated suction capacity of the counter E and the gas flow rate to be measured. There is a difference between them,
Alternatively, when the purity of the atmosphere R is low, there is a problem that a large error occurs in the measurement.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for measuring particles generated from a welded portion or the inside of a conventional ultra-high-purity gas piping when welding or operating equipment in the piping. Such a problem, that is, it is difficult to measure the particles with high precision by measuring the particles from the equipment in the pipe. In the case of measuring the particles from the welded portion, the difference between the rated suction flow rate of the particle counter E and the flow rate of the gas to be measured from the pipe opening is measured. In the case where there is a difference in the flow rate or the purity of the measurement atmosphere is low, the problem that high-precision particles cannot be measured is solved. A method for measuring dust particles that can always measure particles with high accuracy, even if there is a difference from the rated suction flow rate of E or in an atmosphere with low purity. It is intended to provide.

[0010]

According to the present invention, a plurality of particle sizes are provided.
Count the number of dust particles belonging to each particle size range for each range.
In the method of measuring the number of dust particles generated in the welded portion or the device at the time of welding the pipe or operating the device interposed in the pipe by the particle counter configured to measure the gas to be measured (23) Opening of gas discharge pipe (11) from which gas is discharged and particle counter (13)
The base opening of the gas introduction pipe (12) connected to the inside of the outer pipe (10) is concentrically opposed inside the outer pipe (10).
Open the distal end of the outlet pipe (11) to the proximal end of the gas inlet pipe (12).
Insert the inside of the mouth and one side of the outer tube (10)
Et supplied by circulating the the same direction the measurement gas (23) to clean up gas (21) to its inside, the refill gas
(21) is replaced with the gas outlet pipe (11) and the gas inlet pipe (1).
2) into the gas inlet pipe (12)
The flow rate of the suction gas (22) flowing through the gas introduction pipe (12) is controlled by the particle counter (13).
The basic structure of the present invention is to make the suction flow rate substantially equal to the rated suction flow rate.

[0011]

When the suction pump of the particle counter 13 is operated, the gas to be measured 23 released from the distal end opening of the gas outlet pipe 11 is concentrically opposed to the gas introduction pipe 12 which is disposed. The whole amount is sucked into the gas introduction pipe 12 through the base end opening. Further, a part of the clean replenishment gas 21 released into the outer pipe 10 is sucked into the gas introduction pipe 12 through a gap between the base end opening of the gas introduction pipe 12 and the distal end opening of the gas outlet pipe 11. As a result, the suction gas 22 having a flow rate substantially equal to the rated suction flow rate of the counter 13 flows through the gas introduction pipe 12. On the other hand, the replenishment gas 21 sucked into the gas introduction pipe 12 is a clean gas whose particle background is almost zero, and thus the number of particles in the suction gas 22 in the gas introduction pipe 12 is The counter 13 counts the number of particles in the gas 23 under measurement at the rated suction flow rate and without the need for calculation correction by the suction ratio of the supplementary gas 21 and the like. Display correctly.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a method for measuring the number of particles generated from a welded portion at the time of welding a pipe according to the present invention. In the figure, 1 is a liquefied argon container, 2 is an aluminum evaporator, 3 is Manifold pressure reducing valve, 4 is a flow meter,
5 is a metal type filter, 6 is an automatic TIG welding device, 7
Is a pressure reducing valve, 8 is a flow control valve, 9 is a filter, 10 is a stainless steel outer pipe, (19.5 mmφ), 11 is a stainless steel gas outlet pipe (6.35 mmφ), and 12 is a stainless steel gas inlet pipe (9. 52), 13 is a laser particle counter, 14 is a stainless flexible tube (9.52mmφ), and 15 is a metal (stainless) tube (6.35mmφ). Also, in FIG.
16 is a stainless steel tube whose inner wall surface is polished by electrolysis or the like (S
US316L, outer diameter 6.35mmφ, wall thickness 1mm), 1
7 is a tungsten electrode rod (1.0 mmφ, tip angle α =
15 °, distance between electrode and groove L = 0.8 mm), 18
Is an arc gas (argon, flow rate 8 L / min), 19 is a back shield gas (argon, flow rate 6 L / min),
20 is a back shield gas limiting device (orifice), 2
1 is a supplementary gas (N ₂ ), 22 is a suction gas, and 23 is a gas to be measured. The automatic TIG welding device 6 includes an astro-arc type automatic welding machine (CA150 manufactured by Astro-Arc Co., Ltd.).
P) is used, and the welding is completed when the electrode rod 17 rotates 2.5 times around the conduit 16 at a speed of 7.9 sec / rotation. The automatic TIG welding device 6
The arc gas 18, the back shield gas 19, which is supplied inside the conduit 16, and the replenishment gas 21, which is supplied into the outer tube 10, are the filter 5 a attached to the automatic TIG welding device 6 and the metal type. Filter 5 and Filter 9
And the number of particles corresponding to the background in the gases 18, 19 and 21 is almost zero.

As the laser particle counter 13, a counter having a rated suction flow rate of 28.3 L / min (TS-3700 manufactured by Hitachi Electronics Co., Ltd.) is used.
Outer pipe 1 through pressure reducing valve 7, flow regulating valve 8 and filter 9
The nitrogen gas is discharged at a flow rate of 50 L / min into the laser particle counter 0, and the laser particle counter 13 outputs the rated flow rate (28.3 L).
/ Min) can be sucked through the gas inlet tube 12. In other words, the base opening of the gas inlet tube 12 and the distal end opening of the gas outlet tube 11 are made to face each other inside the outer tube 10, and the supplementary gas 21 is sucked into the gas inlet tube 12 from the gap therebetween. Then, a suction gas 22 having a rated flow rate is sucked into the counter 13 through the gas introduction pipe 12.

The measurement of particles generated from the welded portion by the laser particle counter 13 is performed 5 minutes before the start of welding (the arc gas 18 is sucked into the automatic TIG welding device 6 and the back shield gas is continuously supplied at a flow rate of 6 L / min). At the same time, the replenishment gas 21 is continuously supplied at a flow rate of 50 L / min), and the particles are continuously measured until 5 minutes have passed since the completion of welding. Further, an output area corresponding to the measurement output during the welding process is specified from the measurement output of the counter 13 (output area from the start of welding to the end of welding), and the number of particles counted during that period is calculated. The arc gas 18 is free-purged at a flow rate of 8 L / min for 20 seconds from the start of welding (welding power supply is turned on). Thereafter, the arc gas 18 is continuously supplied at the same flow rate while the arc is turned on. Subsequently, post-purge is performed at the same flow rate for about 20 seconds.

Table 1 shows the measured values of the particles from the welded portion when measured according to the present invention (tests NO1, NO2,
NO3) and the measured values of the particles from the welded part when measured by the conventional method (tests NO1 ', NO2',
No. 3 '), and the method of forming the welds in the tests NO1 and NO1', NO2 and NO2 ', and NO3 and NO3' is the same. As is clear from Table 1, in the case of the measurement method according to the present invention, even if there is a difference between the flow rate of the exhaust gas 23 and the suction capacity of the laser particle counter 13, the measurement is performed by the test atmosphere to be sucked. Since the value is hardly affected, the number of particles can be measured very accurately. In Table 1, since the test atmosphere has a relatively high purity, there is no large difference in the measured values. However, when the purity of the atmosphere is reduced, the difference between the measured values becomes remarkable.

[0016]

[Table 1]

FIG. 3 shows a case of measuring particles generated inside a control valve provided in an ultrahigh-purity gas piping system when the control valve is operated according to the present invention. That is, N ₂ having a substantially zero background value of particles is supplied to the control valve 24 through the pressure reducing valve 27, the flow control valve 26, and the filter 25.
The gas 28 is supplied, and the background value of the particles is supplied to the outer tube 10 as a supplementary gas (N ₂ gas) 2 which is almost zero.
By supplying 1, the flow rate of the suction gas 22 sucked into the counter 13 can be the rated suction flow rate of the counter 13.

[0018]

According to the present invention, the gas inlet pipe 12 connected to the laser particle counter 13 and the leading end opening of the gas outlet pipe 11 from which the gas to be measured is discharged in the outer pipe 10 having a large diameter. A concentrically opposed base end opening, and a clean replenishment gas 21 is supplied into the outer tube 10;
Since the replenishment gas 21 is made to flow in the same direction as the gas 23 to be measured, even if the flow rate of the gas 23 to be measured and the rated suction flow rate of the laser particle counter 13 are different, the gas is sucked into the counter 13. The flow rate of the suction gas 22 automatically becomes the rated suction flow rate, the entire amount of the gas to be measured is sucked into the counter 13, and no particles contained in the external atmosphere enter the suction gas 22 at all. As a result, the particles in the gas to be measured 23 can be easily measured extremely accurately and without requiring special calculation for correction, and the measurement accuracy of the particles is greatly improved. Further, since the measurement of particles can be performed regardless of the external atmosphere, it is extremely convenient in practice.

[Brief description of the drawings]

FIG. 1 shows a case where particles generated from a welded portion of a pipe during welding are measured according to the present invention.

FIG. 2 shows a case where particles generated from inside the control valve when the control valve is operated are measured according to the present invention.

FIG. 3 shows a case where particles generated when a control valve is opened and closed are measured by a conventional method.

FIG. 4 shows a case where particles generated from a welded portion at the time of welding a pipe are measured by a conventional method.

[Explanation of symbols]

1 is a liquefied argon gas container, 2 is an aluminum evaporator, 3 is a manifold pressure reducing valve, 4 is a flow meter, 5 is a metal type filter, 6 is a TIG automatic welding device, 7 is a pressure reducing valve, 8 is a flow control valve, 9 Is a filter, 10 is an outer tube, 11 is a gas outlet tube, 12 is a gas inlet tube, 13 is a laser particle counter, 14 is a flexible tube, 15 is a Teflon tube, 16 is a stainless steel tube, 17 is a tungsten electrode rod, and 18 is an arc gas. , 19 is the back shield gas,
20 is a back shield gas discharge restricting means, 21 is a supplementary gas, 22 is a suction gas, 23 is a gas to be measured, 24 is a control valve, 25 is a filter, 26 is a flow control valve, 27 is a pressure reducing valve, and 28 is N ₂ gas. It is.

Continuation of the front page (56) References JP-A-56-132545 (JP, A) JP-A-56-130640 (JP, A) JP-A-5-38574 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) G01N 15/00-15/14

Claims (1)

(57) [Claims] 2. A method according to claim 1 , wherein each of the plurality of particle size ranges belongs to each particle size range.
A particle counter configured to measure the number of dust particles is used to measure the number of dust particles generated in the welded portion or the device at the time of welding a pipe or operating a device interposed in the pipe. In the method, the gas to be measured (2
The opening at the distal end of the gas outlet pipe (11) from which 3) is discharged and the opening at the proximal end of the gas introduction pipe (12) connected to the particle counter (13) are concentric within the outer pipe (10). And the tip opening of the gas outlet pipe (11) is
When inserted inside the proximal opening of the gas introduction pipe (12),
Then, a clean supplementary gas (21) is supplied from one side of the outer tube (10) to the inside thereof and flows in the same direction as the gas to be measured (23), and the supplementary gas (21) is supplied to the gas. Outgoing pipe
Gas introduction through the gap between (11) and gas introduction pipe (12)
By flowing into the inside of the pipe (12), the gas introduction pipe
(12) The flow rate of the suction gas (22) flowing through the inside is made substantially equal to the rated suction flow rate of the particle counter (13). How to measure dust particles.