JPH06129977A - Ultra high purity gas piping equipment and method for measuring dust particles from welds - Google Patents

Abstract

(57) [Summary] [Purpose] To be able to accurately measure the number of dust particles generated inside the equipment or at the welded portion during operation of equipment used for high-purity gas piping and welding of piping. [Structure] A tip end opening of a gas outlet tube from which a gas to be measured is discharged and a base end opening of a gas inlet tube connected to a laser particle counter are concentrically opposed to each other inside the outer tube, and By supplying a clean replenishment gas into the pipe and circulating it in the same direction as the gas to be measured, the flow rate of the suction gas in the gas introduction pipe is made substantially equal to the rated suction flow rate of the laser particle counter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a high accuracy for particles generated inside an equipment or the like installed in an ultra-high purity gas pipe when operating, and particles such as dust generated from a welded portion during welding of the pipe. The present invention relates to a method for measuring dust particles that can be easily measured with.

[0002]

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

By the way, in the welding of ultrahigh-purity gas piping, it goes without saying that the mechanical strength of the welded portion, the flatness of the inner surface of the welded portion, etc. become a problem. It is an essential requirement that is not a pollution source of the pipeline, that is, a generation source of particles. In other words, in developing the welding method for this kind of ultra-high purity gas piping, in addition to measuring the mechanical strength of the weld and the flatness of the inner surface, it is easier to generate dust particles during welding. In addition, it is necessary to measure with high accuracy.

Further, in this type of ultra-high purity gas system piping, it is necessary to reduce the number of particles generated during the operation of equipment such as control valves provided in the piping system.
For that purpose, it is necessary to be able to easily and accurately measure the particles generated from the inside of the control valve or the like when it operates.

FIG. 3 shows a conventional method for measuring dust particles from the control valve V, in which the sampling pipe C of the particle counter E is inserted into the pipe W and the valve V is opened / closed so that the inside of the gas to be measured D is measured. The number of particles emitted to is counted. However, in the method as shown in FIG. 3, the flow velocity of the gas to be measured D 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 to be measured D is changed. There is a problem that the number of particles cannot be measured quickly and accurately because of the necessity of correction for the measurement.

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

More specifically, the pipe B has an outer diameter of 6.35.
mmφ, 1 mm thick stainless steel tube (SUS316L)
The welded portion A was processed by cutting the pipe B to a certain size with a pipe cutter, processing the end face while purging with nitrogen gas at 40 L / min, and then using high pressure nitrogen gas at 7 to 9.5 kg / cm ² . After purging for 2 seconds, both end faces of the pipes are lightly pressed and concentric with each other so that no gap can be visually observed. In addition, the automatic welding device F includes an automatic TIG welding device (CA150P manufactured by Astroarc Co., Ltd.).
Type) is used, and the welding conditions are as follows: outer diameter of tungsten electrode 1.0 mmφ, electrode tip angle α = 15 °, distance between electrode and groove 0.8 mm, arc gas (argon) flow rate 8 L / min, back Shield gas (argon) flow rate 6 L / min, electrode rotation speed 7.9 sec / revolution, peak current 21 A, base current 20 A, number of electrode rotations 2.5
Times, time from arc start to electrode rotation (delay time) 2 sec, time from starting to decrease welding current value to arc stop (down slope time)
Each is set to 4.2 sec. In addition, the arc gas (argon) is supplied from the liquefied argon gas container to the automatic welding device through the vaporization device and continuously pre-purged at a flow rate of 8 L / min before the arc start, and
Post-purged for 20 seconds after arc stop,
In addition, back shield gas (argon) was continuously fed inward from the tip opening of both tubes immediately after setting both stainless 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 /
A Hitachi Electronics Co., Ltd. TS-3700 type is used, and the tip of the pipe B on the downstream side of the welded portion A is inserted into a sampling pipe C having an outer diameter of 9.52 mm and a wall thickness of 1 mm to be measured. The gas D is introduced into the sampling pipe C. 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, and for 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: 2.0 μm or more particles and C
At h7, the total number of particles was measured.
Also, the cleanliness of welding is 0.1 μm standard class 1
(The number of particles exceeding 0.1 μm is 1 per 1 ft ^3.
(Less than or equal to one), and the particle measurement by the laser particle counter E is continuously performed from 5 minutes before the start of welding to 5 minutes after the end of welding, and then the change of the measurement output. The output area during the welding time is specified from, and the number of particles measured during that time is calculated.

Thus, in measuring the number of particles, the particles are measured in an atmosphere of extremely high cleanliness, and moreover, the particles are discharged from the rated suction capacity of the particle counter E and the tip opening of the pipe B. When the flow rate of the measured gas D is almost equal, the particles can be measured relatively accurately. However, as shown in FIG. 3, the rated suction capacity of the counter E is 28.3 L /
Measured gas D for min (1 cubic foot / m ³ ).
Is relatively low at 6 to 7 L / min, the indoor 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 velocity suction. The number of particles contained in the indoor atmosphere R is necessarily counted. Therefore, the flow rate of the suctioned indoor atmosphere R (L / min)
A method is generally used in which the number of particles in the room atmosphere R is calculated from the number of particles in the room atmosphere R (particles / m ³ ), and the count value is corrected using the calculated number. 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 of each particle size of particle, that is, the count number of each channel of the counter E.
The problem is that accurate measurements cannot be made. Further, in order to perform accurate measurement, it is necessary to maintain the atmosphere R at a considerable degree of purity, and this also imposes many restrictions. According to the test results, it is clear that even if the total number of measured particles is corrected, a substantial error is actually included, and the rated suction capacity of the counter E and the measured gas flow rate are There is a difference,
Alternatively, if the atmosphere R has a low purity, there is a problem that a large error occurs in the measurement.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been described above in the case of measuring particles generated from a welded portion or the inside of a device during welding of an ultrahigh-purity gas system pipe or during operation of a device inside the pipe. Such a problem is that it is difficult to measure the particles from the equipment in the pipe with high accuracy. In the measurement of the particles from the welded portion, there is a difference between the rated suction flow rate of the particle counter E and the measured gas flow rate from the pipe opening. If there is a difference in temperature or the purity of the measurement atmosphere is low, the problem that high-precision particle measurement cannot be performed will be solved, and the flow rate of the measured gas D from the opening end of the pipe and the counter. Even if there is a difference between the rated suction flow rate of E, or even in an atmosphere of low purity, a method for measuring dust particles that can always measure particles with high accuracy It is intended to provide.

[0010]

According to the present invention, in a method for measuring the number of dust particles generated in a welded portion or equipment during welding of piping or operation of equipment by a pulse counter, the measured gas 23 is The tip end opening of the discharged gas lead-out tube 11 and the base end opening of the gas introduction tube 12 connected to the particle counter 13 are concentrically opposed to each other inside the outer tube 10, and into the outer tube 10. The invention is such that a clean replenishment gas 21 is supplied and circulated in the same direction as the gas to be measured 23 so that the flow rate of the suction gas 22 in the gas introduction pipe 12 becomes substantially equal to the rated suction flow rate of the particle counter 13. The basic configuration of

[0011]

When the suction pump of the particle counter 13 is actuated, the gas to be measured 23 discharged from the tip opening of the gas outlet pipe 11 is arranged so as to concentrically face the gas to be measured 23. The entire amount is sucked into the gas introducing pipe 12 through the proximal end opening of the. Further, a part of the clean replenishing gas 21 released into the outer pipe 10 is sucked into the gas introducing pipe 12 through the gap between the base end opening of the gas introducing pipe 12 and the tip opening of the gas introducing 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 in the gas introduction pipe 12. On the other hand, since the replenishment gas 21 sucked into the gas introduction pipe 12 is a clean gas having a particle background of almost zero, the number of particles in the suction gas 22 in the gas introduction pipe 12 is the measured gas 23. Therefore, the counter 13 calculates the number of particles in the measured gas 23 at the rated suction flow rate without requiring calculation correction by the intake ratio of the replenishment gas 21 or the like. Display accurately.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a method of measuring the number of particles generated from a welded portion during welding of a pipe according to the present invention. In the figure, 1 is a liquefied argon container, 2 is an aluminum evaporator, and 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 rate adjusting valve, 9 is a filter, 10 is a stainless steel outer tube (19.0 mmφ), 11 is a stainless steel gas outlet pipe (6.35 mmφ), and 12 is a stainless steel gas introduction pipe (9. 52 mmφ), 13 is a laser particle counter, 14 is a stainless flexible tube (9.52 mmφ), and 15 is a metal (stainless) tube (6.35 mmφ). In addition, in FIG.
16 is a stainless steel tube whose inner wall surface is polished by electrolysis (S
US316L, outer diameter 6.35mmφ, wall thickness 1mm), 1
7 is a tungsten electrode rod (1.0 mmφ, tip angle α =
15 °, distance L 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
Reference numeral 1 is a supplementary gas (N ₂ ), 22 is an intake 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 by rotating the electrode rod 17 around the conduit 16 for 2.5 turns at a speed of 7.9 sec / rev. In addition, the automatic TIG welding device 6
The arc gas 18 supplied to the pipe 16, the back shield gas 19 supplied to the inside of the pipe 16, and the supplementary gas 21 supplied to the outer pipe 10 are both the filter 5a 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 (TS-3700 type manufactured by Hitachi Electronics Co., Ltd.) having a rated suction flow rate of 28.3 L / min is used.
Outer tube 1 through pressure reducing valve 7, flow rate adjusting valve 8 and filter 9
Nitrogen gas is discharged into the chamber at a flow rate of 50 L / min, and the laser particle counter 13 outputs the rated flow rate (28.3 L).
/ Min) of the suction gas 22 can be sucked through the gas introduction pipe 12. That is, in the inner side of the outer pipe 10, the base end opening of the gas introduction pipe 12 and the front end opening of the gas lead-out pipe 11 are made to face each other, and the replenishment gas 21 is sucked into the gas introduction pipe 12 through the gap between them. The suction gas 22 having the rated flow rate is sucked into the counter 13 through the gas introduction pipe 12.

The measurement of dust particles 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 supply gas 21 is continuously supplied at a flow rate of 50 L / min), and the particles are continuously measured until 5 minutes have elapsed after the completion of welding. Further, the output area corresponding to the measurement output during the welding process is specified from the measurement output of the counter 13 (output area from welding start to welding end), and the number of particles counted during that time 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 source is on), then continuously supplied at the same flow rate while the arc is on, and even after the arc is turned off. Subsequently, post-purging is performed at the same flow rate for about 20 seconds.

Table 1 shows the measured values of particles from the welded portion (tests NO1, NO2, NO2) when measured according to the present invention.
NO3) and the measured values of particles from the welded portion when measured by the conventional method (test NO1 ′, NO2 ′,
No. 3 ') is shown for comparison, and the method of forming welds in each of the tests NO1 and NO1', NO2 and NO2 ', and NO3 and NO3' is under the same conditions. As is clear from Table 1 above, in the case of the measuring 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 according to the suctioned test atmosphere. Since the value is hardly affected, the number of particles can be measured extremely accurately. It should be noted that in Table 1, since the test atmosphere has a relatively high purity, a large difference does not occur in the measured values, but when the purity of the atmosphere decreases, the difference in the measured values becomes remarkable.

[0016]

[Table 1]

FIG. 3 shows a case where particles generated inside the control valve provided in the ultra-high purity gas piping system are measured according to the present invention. That is, through the pressure reducing valve 27, the flow rate control valve 26, and the filter 25 to the control valve 24, N ₂ having a background value of particles of substantially zero.
A supplementary gas (N ₂ gas) 2 whose background value of particles is almost zero is supplied into the outer tube 10 while supplying the gas 28.
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 tip opening of the gas outlet pipe 11 through which the gas to be measured is discharged in the outer pipe 10 having a large diameter. And a clean replenishing gas 21 is supplied into the outer tube 10 while concentrically facing the base end opening of the
Since the replenishment gas 21 is made to flow in the same direction as the measured gas 23, even if the flow rate of the measured gas 23 and the rated suction flow rate of the laser particle counter 13 are different, they are 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 measured very accurately and easily without requiring calculation for special correction, and the particle measurement accuracy is significantly improved. In addition, since particles can be measured regardless of the external atmosphere, it is extremely convenient in practice.

[Brief description of 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 the inside of a control valve are measured when the control valve is operated according to the present invention.

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

FIG. 4 shows a case where particles generated from a welded portion are measured when a pipe is welded 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 rate adjusting 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 tube, 17 is a tungsten electrode rod, and 18 is an arc gas. , 19 is back shield gas,
20 is a back shield gas discharge limiting means, 21 is a replenishing gas, 22 is an intake 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. Is.

Claims (1)

[Claims] 1. A method for measuring the number of dust particles generated in a welded part or equipment during welding of pipes or operation of equipment by means of a pulse counter, in which a gas to be measured (23) is discharged. The front end opening of (11) and the base end opening of the gas introduction pipe (12) connected to the particle counter (13) are concentrically opposed to each other inside the outer pipe (10), and the outer pipe ( 10) A clean replenishing gas (21) is supplied into the gas supply pipe (12) to flow in the same direction as the gas to be measured (23), and the flow rate of the suction gas (22) in the gas introduction pipe (12) is adjusted to the particle counter (13). The method for measuring dust particles from equipment and welds of ultra-high purity gas piping is characterized in that it is made substantially equal to the rated suction flow rate.