Patent Grant
10354853
This application is a National Stage of International Application No. PCT/JP2016/068762 filed Jun. 24, 2016, claiming priority based on Japanese Patent Application No. 2015-251434 filed Dec. 24, 2015.
The present invention relates to an ICP mass analysis device (also known as ICP-MS) which performs mass analysis by ionizing a sample by means high frequency inductively coupled plasma.
ICP mass analysis devices are widely known as analyzers capable of performing high sensitivity multi-element analysis, and are used for elemental analysis in a broad range of fields (for example, see Patent Literature 1).
ICP mass analysis device 100 mainly comprises a plasma torch 11, a high frequency power supply 12, a sample introduction unit 13, a mass analysis unit 14 comprising a mass analyzer, a gas flow rate control unit 15, and a device main body control unit 16, which make up a device main body unit 1. A cooling water system 2 and an Ar gas supply system 3, which are necessary when using the ICP mass analysis device 100, are furthermore connected to the device main body unit 1.
The device main body unit 1 of the ICP mass analysis device 100 will be described in detail. The gas flow rate control unit 15 performs flow rate control of sample gas supplied from a nebulizer 19, Ar gas for plasma generation supplied via gas pipe 31 from the Ar gas supply system 3, and the like. The plasma torch 11 comprises a multiwall cylindrical reaction tube 17 to which plasma gas (Ar gas) and sample gas are supplied under flow rate control by the gas flow rate control unit 15, and a high frequency coil 18 wound onto the outer circumference of the reaction tube 17.
The high frequency power supply 12 is connected to a high frequency coil 18, and plasma is generated to ionize the sample gas by applying high frequency voltage to the high frequency coil 18 in a state where plasma gas and sample gas have been introduced into the plasma torch 11.
The sample introduction unit 13 is kept in a reduced pressure state by means of a vacuum pump (not illustrated) and is designed to draw in ions of the sample, which has been ionized by the plasma torch 11, along the central axis of a sampling cone 13a through a sample introduction orifice. The mass analysis unit 14 is maintained at a higher vacuum than the sample introduction unit 13, and performs mass separation of the sample ions, which have been draw in from the sample introduction unit 13, by means of a quadrupole 14a or the like, and further performs mass analysis by means of an ion detector 14b.
The device main body control unit 16 is composed of a computer device comprising an input device (keyboard, mouse, etc.), display device (liquid crystal panel, etc.) and input/output interface, and performs configuration, command input and control of the various units of device main body unit 1, and also performs processing of data detected by the ion detector 14b.
In this sort of ICP mass analysis device 100, the reaction tube 17 of the plasma torch 11 which generates plasma is brought to a high temperature through induction heating, and in addition to that, the sample introduction unit 13 located opposite the plasma torch 11, the high frequency coil 18 and the high frequency power supply board 12a contained within the high frequency power supply 12 also reach a high temperature.
Thus, excluding the reaction tube 17 of the plasma torch 11, cooling is required for the sample introduction unit 13, high frequency coil 18 and high frequency power supply 12, and cooling water is supplied from a cooling water system 2 in order to prevent corrosion and melting of the copper sampling cone 13a of the sample introduction unit 13 and of the copper high frequency coil 18, and to prevent breakdown due to heat generation of the high frequency power supply board 12a contained within the high frequency power supply 12.
Flow passage (bypass flow passage) 23 and flow passage (high frequency power supply cooling flow passage) 24 are used by switching between them so as to prevent condensation from forming on the high frequency power supply 12, and are controlled such that the flow passage 24 side is opened when the high frequency power supply is in an ON state and requires cooling, and the flow passage 23 side is opened when the high frequency power supply is in an OFF state and does not require cooling. This flow passage switching control is performed by the device main body control unit 16 in a manner interlocked with the turning on and off of the high frequency power supply 12, with control being performed such that when one is opened, the other is closed, so that cooling water is always flowing.
Flow passage 23 and flow passage 24 merge into flow passage 25, which then again branches into two and is connected to a flow passage (sample introduction unit cooling flow passage) 26 which cools the sample introduction unit 13 and a flow passage (high frequency coil cooling flow passage) 27 which cools the high frequency coil 18. After cooling the sample introduction unit 13 and high frequency coil 18, the flow passage 26 and flow passage 27 merge again into flow passage 28, and flow passage 28 is recirculated to the chiller 20.
The portions of device main body unit 1 which require cooling by the cooling water system 2 will be referred to as “cooled structures.” Among the three cooled structures consisting of the high frequency power supply 12, sample introduction unit 13 and high frequency coil 18, in the sampling cone 13a of the sample introduction unit 13, the orifice diameter of the central sample introduction orifice gradually widens due to aging degradation, which has an effect on analysis results, so the sampling cone 13a is made replaceable as a consumable part.
When the sampling cone 13a is to be replaced, the replacement is made from the cooling jacket 13b, and thus when the cooling jacket 13b is detached from the sample introduction unit main body 13c, the cooling water flow passage is opened at the interface between the connecting flow passage 13e and cooling flow passage 13d.
If the cooling jacket 13b is to be detached in order to replace the sampling cone 13a after cooling water has been fed into the cooling water system 2, it is necessary to stop the supply of water by closing the master valve V0, and to perform purging in order to drain the residual water remaining in the various flow passages past the master valve V0. For this purpose, a flow passage for supplying purge gas is formed in the cooling water system 2.
Namely, as shown in
When the cooling jacket 13b of the sample introduction unit 13 is to be replaced, first, the master valve V0 is closed, after which the purge valve V1, first intermediate valve V2 and second intermediate valve V3 are all opened simultaneously, residual water is drained by introducing Ar gas from purge gas flow passage 32 into flow passages 22 through 28, and then the cooling jacket 13b is removed.
Similar Ar gas purging is also performed when performing maintenance operations of the cooling water system 2 besides the sample introduction unit 13. Furthermore, a similar draining operation using Ar gas purging is performed not just during maintenance operations but also in order to prevent corrosion due to residual water when the device is stopped for a long period of time.
Patent Literature 1: Japanese Unexamined Patent Application Publication 2014-85268
However, the water cooling piping of the cooling water system 2 has a large pipe diameter and relatively low pipe resistance, so if purging with Ar gas is continued in order to drain the residual water, the amount of Ar gas consumption will become extremely high.
Furthermore, the same Ar gas that is used for purging the cooling water system 2 is also used in the ICP mass analysis device 100 as the plasma gas (Ar gas), as the carrier gas for nebulizing the sample, etc., and is supplied via the Ar gas supply system 3 from an Ar gas source consisting of a single gas bottle (or liquid bottle).
At sites such as research facilities or factories where ICP mass analysis devices are installed, the Ar gas source is in nearly all cases used not just for a single ICP mass analysis device but is rather shared among multiple devices (other analytical devices, film growing devices, etc.).
For example, as shown in
In such an environment, when Ar gas purging is performed on the cooling water system 2 of the ICP mass analysis device 100 as described above, Ar gas will continuously flow into the water cooling piping at a larger flow rate compared to when Ar gas is supplied from the Ar gas flow passage 31 to the gas flow rate control unit 15, and so the supply pressure of the Ar gas source will gradually decrease. Specifically, it has been confirmed that Ar gas supply pressure which is normally maintained by means of a regulator at 480 KPa may drop to 400 KPa or less.
Therefore, there is an adverse effect upon the operation of other devices to which Ar gas is supplied from the same Ar gas source. In an environment where two ICP-MS devices 100 and 101 are connected to a common Ar gas source as shown in
It is therefore an object of the present invention to provide an ICP mass analysis device which makes it possible to reduce the Ar gas consumption rate when performing Ar gas purging of the cooling water system of the ICP mass analysis device, while allowing residual water to be effectively drained.
It is a further object of the present invention to provide an ICP mass analysis device capable to reducing fluctuation in the supply pressure of the Ar gas source when Ar gas purging of the cooling water system is performed.
The ICP mass analysis device of the present invention, made to resolve the aforementioned problem, comprises: a device main body unit which supplies Ar gas for plasma generation and sample gas, via a gas flow rate control unit which controls gas flow rate, to a reaction tube of a plasma torch, ionizes the sample gas by applying a high frequency voltage from a high frequency power supply to a high frequency coil of said plasma torch, and draws in generated sample ions through a sample introduction unit to a mass analyzer to perform mass analysis; a cooling water system in which water cooling piping is connected as a flow passage to cooled structures which require cooling, including said high frequency power supply, said high frequency coil and said sample introduction unit, and which supplies cooling water from a water source to said cooled structures; and an Ar gas supply system in which gas piping is connected as a flow passage to said gas flow rate control unit and which supplies Ar gas from an Ar gas source; wherein, in said cooling water system, there is provided a master valve (V0) which is connected as a flow passage on the upstream side of said water cooling piping, a purge gas flow passage which branches from said gas piping and is connected as a flow passage via a purge valve (V1) at a location downstream of said master valve (V0) so as to merge into said water cooling piping, and an intermediate valve (V2, V3) which is connected as a flow passage to said water cooling piping downstream of the merging point of said purge gas flow passage; said cooled structures are connected as a flow passage to said water cooling piping downstream of said intermediate valve (V2, V3); a valve control unit is provided, which performs interlocked opening/closing control of said master valve (V0), said purge valve (V1) and said intermediate valve (V2, V3); and said valve control unit, when said master valve (V0) is placed into a closed state and said purge valve (V1) is placed into an open state and Ar gas is fed via said purge gas flow passage, performs intermittent purge control whereby said intermediate valve (V2, V3) is intermittently opened and closed to repeat pressure accumulation and release of Ar gas upstream of said intermediate valve (V2, V3).
According to the present invention, when draining of residual water of the cooling water system is to be performed for maintenance operations, etc., the valve control unit closes the master valve and places the purge valve into an open state to feed purge gas into the cooling water piping via the purge gas flow passage, at which time the valve control unit performs control whereby the intermediate valve is intermittently opened and closed.
As a result, intermittent purging is performed, whereby pressure accumulation and release of Ar gas are intermittently repeated upstream of the intermediate valve.
Therefore, it becomes possible to perform purging by intermittently flashing with Ar gas whereof the pressure has accumulated in the piping upstream of the intermediate valve (which is at about the same pressure level as the supply pressure upstream of the purge valve), making it possible to effectively drain residual water with a smaller quantity of Ar gas.
Furthermore, since there is no need to continuously (rather than intermittently) release Ar gas as in the prior art, the total consumption of Ar gas consumed during draining can also be reduced.
In the invention as described above, it is preferable to provide, in the purge gas flow passage downstream of the purge valve, a pipe resistance comprising a pipe of the same diameter as or narrower diameter than the pipe diameter of the purge gas flow passage.
As a result, even when the purge valve is placed into an open state, it is possible to suppress sudden inflow of Ar gas into the purge gas flow passage, so the fluctuation in the supply pressure upstream of the purge valve can be kept very low. It will be noted that in the case of the same diameter, pipe resistance can be increased by providing a longer flow passage length.
While the effect of reducing fluctuation in supply pressure here becomes greater with a greater pipe resistance, since the rate of inflow via the pipe resistance decreases, the pressure of inflowing gas downstream of the pipe resistance will drop. If purging is performed in a state of free discharge as in the prior art rather than performing intermittent purging, depending on the magnitude of the pipe resistance, the downstream gas pressure of the purge gas will drop, and if the flow resistance of cooling water is high, it will become impossible to drain residual water.
In response to this, in the present invention, by ensuring adequate time for accumulating pressure of Ar gas in accordance with the magnitude of pipe resistance in the flow passage up to the intermediate valve when the purge valve has been placed into an open state, the pressure of Ar gas accumulated upstream of the intermediate valve can be restored to about the same level as the pressure in the piping upstream of the purge valve, so even if the pipe resistance is increased, the operation of purging residual water can be effectively performed with the accumulated pressure.
Namely, not only can the fluctuation in supply pressure upstream of the pipe resistance be reduced, but residual water can be effectively drained with a smaller amount of Ar gas by performing purging by flushing with Ar gas whereof the pressure has accumulated upstream of the intermediate valve (to a pressure equal to the pressure inside the piping upstream of the purge valve).
Furthermore, in the present invention as described above, a configuration may be adopted wherein the water cooling piping of the cooling water system branches, downstream of the merging point of the purge gas flow passage, into a bypass flow passage having a first intermediate valve, and a high frequency power supply cooling flow passage to which a second intermediate valve and the high frequency power supply are connected as flow passages in series in that order; the sample introduction unit and the high frequency coil are connected as flow passages downstream of the bypass flow passage and the high frequency power supply cooling flow passage; and the valve control unit, when performing intermittent purge control, performs control whereby the first intermediate valve and the second intermediate valve are simultaneously placed into an open state, and the bypass flow passage and high frequency power supply cooling passage are simultaneously purged.
Furthermore, instead of this, a configuration may be adopted wherein the valve control unit, when performing intermittent purge control, performs control whereby the first intermediate valve and second intermediate valve are alternately placed into an open state one at a time, and the bypass flow passage and high frequency power supply cooling flow passage are purged one at a time.
In the ICP mass analysis device of the present invention, in order to prevent condensation on the high frequency power supply, the flow passage of the cooling water system is connected so as to branch into a bypass flow passage and high frequency power supply cooling passage, a first intermediate valve is arranged in the bypass flow passage, and a second intermediate valve and the high frequency power supply are arranged in the high frequency power supply cooling flow passage. This first intermediate valve and second intermediate valve are configured such that when the high frequency power supply is off, the first intermediate valve is opened and the second intermediate valve is closed, and when the high frequency power supply is on, the first intermediate valve is closed and the second intermediate valve is opened, so that only one of the flow passages is in an open state and has cooling water flowing through it, thereby preventing the occurrence of condensation.
In the present invention, the first intermediate valve and second intermediate valve that are used for switching the flow passage in interlocking fashion with the turning on and off of the high frequency power supply for the purpose of preventing condensation, are also utilized for pressure accumulation for the purpose of draining residual water.
Namely, independently of the primary opening/closing control that is interlocked with the operation of the high frequency power supply, when the valve control unit performs intermittent purge control, control is performed whereby the first intermediate valve and second intermediate valve are simultaneously placed into an open state, and the bypass flow passage and high frequency power supply cooling flow passage are simultaneously purged. Alternatively, when performing intermittent purge control, the valve control unit performs control whereby the first intermediate valve and second intermediate valve are alternately placed into an open state one at a time.
According to the present invention, effective draining becomes possible simply by adding an intermittent purge control flow (intermittent purging sequence) using the valve control unit.
Embodiments of the present invention will be described below using the drawings.
In the ICP mass analysis device A according to the present invention, the device main body control unit 16 composed of a computer device as in the conventional ICP mass analysis device 100, is provided with a valve control unit 35 which performs execution of a valve control program which implements Ar gas purging based on opening and closing of a master valve V0, purge valve V1, first intermediate valve V2 and second intermediate valve V3.
This valve control unit 35, when draining of the cooling water system 2 is to be performed, as a maintenance mode, performs intermittent purge control in which the master valve V0, purge valve V1, first intermediate valve V2 and second intermediate valve V3 are operated according to an operation flow as described below. Namely, when master valve V0 is placed into a closed state and purge valve V1 is placed into an open state and Ar gas is fed into the cooling water system 2 via the purge gas flow passage 32, the first intermediate valve V2 and second intermediate valve V3 are maintained in a closed state until the time necessary for pressure accumulation (pressure accumulation time T) has elapsed and are then placed into an open state, after which they are again placed into a closed state, which is maintained until pressure accumulation time T has elapsed, after which the valves are placed into an open state. The operation of opening and closing intermittently in this manner is repeated to perform control for repeating the pressure accumulation and release of Ar gas.
Furthermore, in the present embodiment, a pipe resistance 36 which restricts inflow of gas is provided in the purge gas flow passage 32 downstream of the purge valve V1. The pipe resistance 36 is selected to have a magnitude of resistance sufficient to prevent sudden pressure fluctuation upstream of the purge valve V1 when the purge valve V1 is opened.
Specifically, in the middle of the purge gas flow passage 32 formed from gas pipe with an inside diameter of 4 mm, a pipe with a narrower inside diameter of 0.5 mm is connected as a (coiled) pipe resistance 36 with a length of 1 m, thereby increasing the pipe resistance of the purge gas flow passage 32.
Connecting the pipe resistance 36 causes the gas flow rate downstream of the pipe resistance 36 to decrease, so the time required for pressure accumulation in the intermittent purge control described above (pressure accumulation time T), i.e. the waiting time until the accumulated Ar gas pressure becomes about the same as the pressure upstream of the purge valve V1, is preset in accordance with the magnitude of the pipe resistance 36 on the basis of preliminary experiments. Furthermore, the time during which the intermediate valves V2, V3 are opened (opening time F) is also set in advance. The description here will assume that the pressure accumulation time T has been set at 10 seconds and the opening time F has been set at 5 seconds.
Furthermore, the purge count n (used as the argument n in the operation flow described later) is also set in advance. In the following embodiment example, it will be assumed that this was set so as to perform five purges (n=5).
Next, the gas purge operation flow under the aforesaid conditions will be described.
(Operation Flow-1)
When an input operation is performed to start maintenance mode with the input device of the device main body control unit 16 in order to perform draining of the cooling water system 2, the parameter n which counts the number of purges is set to the initial value 0, the master valve V0 closes, and the first intermediate valve V2 and second intermediate valve V3 are closed nearly simultaneously. It will be noted that the purge valve V1 is closed to begin with (ST101).
Next, the purge valve V1 is opened and the open state is maintained until a preset pressure accumulation time T (10 seconds) elapses. As a result, the Ar gas of the purge gas flow passage 32 is accumulated until its pressure reaches the same level as the pressure upstream of the purge valve V1 (ST102). The first time, since cooling water remains downstream of the check valve GV, by way of exception, Ar gas is accumulated in the pipe only up to the check valve GV, but in the second and subsequent pressure accumulation described below, pressure accumulation occurs also downstream of the check valve GV.
Next, the first intermediate valve V2 and second intermediate valve V3 are opened for a preset opening time F (5 seconds) to perform purging. During this time, the purge valve V1 is maintained in an open state, and Ar gas which has accumulated in the purge gas flow passage 32 is released and flows downstream, draining the residual water in the downstream direction.
At this time, 1 is added to the purge count parameter n (ST103).
Next, the current purge count is checked on the basis of the parameter n (ST104). If the purge count parameter n is less than 5, the processing of ST102 through ST104 is repeated.
Once parameter n becomes 5, control proceeds to ST105.
After confirming that the set number (n=5) of purges has been carried out in ST104, the master valve V0 and purge valve V1 are closed (ST105). Purging is thereby ended.
The first intermediate valve V2 and second intermediate valve V3 are then also closed (ST106). Device operation is thereby completed.
According to the above procedure, draining can be efficiently carried out through gas purging while reducing the consumption of Ar gas.
(Operation Flow-2)
When an input operation to start maintenance mode is performed using the input device of the device main body control unit 16, the parameter n which counts the number of purges is set to the initial value 0, the master valve V0 closes, and the first intermediate valve V2 and second intermediate valve V3 are closed nearly simultaneously. It will be noted that the purge valve V1 is closed to begin with (ST201).
Next, the purge valve V1 is opened and the open state is maintained until a preset pressure accumulation time T (10 seconds) elapses. As a result, the Ar gas of the purge gas flow passage 32 is accumulated until its pressure reaches the same level as the pressure upstream of the purge valve V1 (ST202). The first time, since cooling water remains downstream of the check valve GV, by way of exception, Ar gas is accumulated in the pipe only up to the check valve GV, but in the second and subsequent pressure accumulation described below, pressure accumulation occurs also downstream of the check valve GV.
Next, the first intermediate valve V2 is opened for a preset opening time F (5 seconds) to perform purging. During this time, the purge valve V1 is maintained in an open state, while the master valve V0 and second intermediate valve V3 are maintained in a closed state. As a result, the Ar gas which has accumulated in the purge gas flow passage 32 is released and flows downstream, draining the residual water in the downstream direction. At this time, 1 is added to the purge count parameter n (ST203).
Next, with the purge valve V1 remaining open, the first intermediate valve V2 is closed, and the open state is maintained until a preset pressure accumulation time T (10 seconds) elapses. As a result, the Ar gas of the purge gas flow passage 32 is accumulated until its pressure reaches the same level as the pressure upstream of the purge valve V1 (ST204).
Next, the second intermediate valve V3 is opened for a preset opening time F (5 seconds) and purging is performed. During this time, the purge valve V1 is maintained in an open state, while the master valve V0 and first intermediate valve V2 are maintained in a closed state. As a result, the Ar gas which has accumulated in the purge gas flow passage 32 is released and flows downstream, draining the residual water in the downstream direction. The purge count parameter n remains unchanged at this time (ST205).
Next, the current purge count is checked on the basis of the parameter n (ST206). If the purge count parameter n is less than 5, the processing of ST202 through ST205 is repeated.
Once parameter n becomes 5, control proceeds to ST207.
After confirming that the set number (n=5) of purges has been carried out in ST206, the master valve V0 and purge valve V1 are closed (ST207). Purging is thereby ended.
The first intermediate valve V2 and second intermediate valve V3 are then also closed (ST208). Device operation is thereby completed.
According to the above procedure, draining can be efficiently carried out through gas purging while reducing the consumption of Ar gas.
(Reference Operation Flow)
Two operation flows constituting embodiments of the present invention were described above. The above-described operation flows-1 and 2 make it possible to achieve a reduction in Ar gas consumption and a reduction in supply pressure fluctuation of the Ar gas supply system, which are the two object of the present invention.
By contrast, when the object is only the latter—reduction in supply gas fluctuation, if the flow resistance of cooling water flowing through the water cooling piping is low and draining is possible with the pressure of the purge gas which has passed through the pipe resistance 36, the device configuration can be simplified.
Namely, it is possible to reduce supply pressure fluctuation simply by using the pipe resistance 36 of the purge gas flow passage 32, without performing intermittent purge control. The reference operation flow for this case is shown in
When an input operation is performed to start maintenance mode with the input device of the device main body control unit 16, the master valve V0 closes, and the first intermediate valve V2 and the second intermediate valve V3 are closed nearly simultaneously. It will be noted that the purge valve V1 is closed to begin with (ST301).
Next, the purge valve V1, first intermediate valve V2 and second intermediate valve V3 are opened simultaneously, and the open state is maintained until a preset opening time F (for example, 30 seconds) elapses (ST302). The master valve V0 is maintained in a closed state. At this time, Ar gas flows in continuously, but the inflow of gas is restricted due to the existence of the pipe resistance 36, so the supply pressure does not drop significantly, making it possible to prevent adverse effects due to pressure fluctuation upstream of the purge valve V1.
Next, after the opening time has elapsed, the master valve V0, purge valve V1, first intermediate valve V2 and second intermediate valve V3 all close, whereby operation of the device is completed (ST303).
Embodiments of the present invention have been described above, but the present invention is not limited to these embodiments and of course includes various other configurations that do not depart from the gist of the present invention.
For example, in the embodiments described above, a structure involving switching the first intermediate valve V2 of flow passage (bypass flow passage) 23 and the second intermediate valve V3 of flow passage (high frequency power supply cooling flow passage) 24 was employed, but the invention can also be applied with a cooling water system of a simpler structure in which no bypass flow passage is provided and only a single intermediate valve is arranged in a single flow passage.
Furthermore, in the embodiments described above, a pipe resistance 36 was provided in the purge gas flow passage 32 to reduce pressure fluctuation on the upstream side, but if instead no pipe resistance 36 is provided and only intermittent purge control is performed using the valve control unit 35, intermittent pressure fluctuation of upstream supply pressure will occur, but this is still effective because the magnitude of supply pressure fluctuation can be reduced as compared to the free-flowing state of the prior art.
The present invention can be employed for ICP mass analysis devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-251434 | Dec 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/068762 | 6/24/2016 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2017/110118 | 6/29/2017 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5741710 | Ek | Apr 1998 | A |
| 6239038 | Wen | May 2001 | B1 |
| 7518108 | Frey | Apr 2009 | B2 |
| 20050109374 | Letessier | May 2005 | A1 |
| 20060285108 | Morrisroe | Dec 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 2014-085268 | May 2014 | JP |
| 2014085268 | May 2014 | JP |
| Entry |
|---|
| International Search Report for PCT/JP2016/068762 dated Aug. 16, 2016. |
| Number | Date | Country | |
|---|---|---|---|
| 20190013192 A1 | Jan 2019 | US |
