JPS58192995A - Scroll pump - Google Patents

Abstract

PURPOSE:To make the flow of liquid in a low flow speed part active and prevent generation of corrosion near the pump shaft of a pump casing by a method wherein a liquid path, passing from the center of a packing for a rotary body including an impeller to the low-pressure part of a pump chamber, is provided. CONSTITUTION:High-pressure liquid in a scroll chamber 18, which is increased in the speed and the pressure thereof by an impeller 4, is passed through the back side of an impeller main plate 9, is injected from a gap between a linering 8 and a wearing part, collides against the wall surface 16 of an intermediate casing 2 as shown by arrow signs 17, is sucked out of a balance hole entrance 113A at a shaft packing side of a part near the center of the rotary body including the impeller 4 to the suction side low-pressure part of a pump chamber through a balance hole 113, and thereby balancing the impeller 4. Accordingly, the surface facing to the vicinity of the pump shaft 3 in the back chamber 10 for the impeller in a shaft packing house 11 is contacted by high-speed current shown by the arrow sign 17', therefore, the flow in the low-speed part is made active and the corrosion of said part may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump that handles body fluids, particularly pumps that handle electrolyte bath fluids such as seawater.

For example, in a pump that handles seawater, corrosion preferentially progresses in and around the casing tongue, or in the vicinity of the casing shaft, which can shorten the life of the pump.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pump that handles electrolyte solutions such as seawater, in which corrosion in the vicinity of the pump shaft of the pump casing is prevented.

Corrosion of the casing tongue and its vicinity is understood to be accelerated due to erosion, since this is the area where high-velocity fluid collides.

By the way, when corrosion progresses in an oxygen-consuming manner, generally speaking, the higher the flow rate, the more dissolved oxygen spreads to the metal surface.

Dispersion becomes faster and corrosion increases.

The preferential corrosion seen near the pump shaft of the pump casing is a phenomenon that is difficult to understand because this is the area where the flow velocity is slow, and there is a general tendency that the slower the flow velocity, the less corrosion there is.

Therefore, the inventors discovered the following five reasons why areas of the pump casing where the flow velocity is slow, such as near the pump shaft, preferentially corrode.
I guessed that.

Inside the pump during operation, there are inevitably locations where the flow velocity differs, and the potential differs at each location due to the difference in flow velocity. Points with different potentials are connected by a conductor called the pump, so they form macrocells in electrolyte solutions such as seawater, so the corrosion distribution inside the pump is a flow rate-corrosion phenomenon that occurs independently at different flow rates. It no longer follows the relationship of quantity. In the above-mentioned macrocell, the part where the flow is fast is the cathode, and the part where the flow is slow is the anode, which accelerates corrosion near the casing axis where the flow is slow.

In order to support the above speculation, the inventors measured the macrocorrosion current near the pump shaft of the pump casing during operation. The inventors measured and clearly determined the macrocorrosion current of the pump casing during operation for the first time.

The following is a method devised and implemented by the inventors in order to actually confirm the formation of macrocells inside the pump casing during operation and to measure the macrocorrosion current flowing therein.

That is, the pump casing was cut and divided, and reassembled with the pump casing in the vicinity of the pump shaft insulated from the portion of the pump casing other than the vicinity of the pump shaft. Lead wires were soldered to each part in advance and led to a non-resistance current needle, and the macrocorrosion current flowing between the two was measured. The density of the macrocorrosion current flowing in the wetted part of the pump casing near the pump shaft is obtained by dividing the macrocorrosion current by the wetted area of the pump casing near the pump shaft, which has been measured in advance.

Figure llI & 1 is a vertical cross-sectional view of a single suction inner liner ring used as a conventional example.

The pump casing consists of the suction side casing l and the pump shaft 3.
The intermediate casing on the driving side is fitted and fastened, and the impeller, which is fixed to the pump shaft JK supported by a bearing (not shown) of the intermediate casing body, has cylindrical wear rings on both sides. The liner ring 7 press-fitted into the casing l and the liner ring t press-fitted into the intermediate casing co are arranged with a gap between them, and the impeller main plate 9 is balanced at a position 11 points away from the center of the impeller da. A hole 13 is provided. And the impeller main plate of the liner ring l, wear ring part 6, p pump shaft 3 @? The space between and the intermediate casing is the back chamber lO of the impeller.

The vicinity of the pump shaft of the pump casing, which was cut and divided for macro-corrosion current measurement and assembled insulated from the casing body, is the part on the pump shaft side as well as point A in FIG.

FIG. 1 shows the change over time in the corrosion current density in the vicinity of the pump shaft of the pump casing as a curve /11. The vertical axis shows the corrosion current density μA2i, and the horizontal axis shows the pump operating time.

Operating conditions are rotation speed/j00min-', flow rate 80@'
/m to i, pump material is cast iron (rI8 FC
-〇), the incorrect solution is 3-saline solution.

As is clear from the figure, macrocells are formed within the pump casing due to the difference in flow velocity, and macro anode current flows near the pump shaft of the pump casing where the flow velocity is slow, promoting corrosion in this area. .

After operating the test pump for three months, it was cut off and the corrosion near the pump shaft of the pump casing was investigated, as shown in Figure 3.

Fl? ! As shown in IIK, the pump shaft 3@ of the shaft sealing hub 1/, that is, the end surface is facing the end surface of the boss 1 of the impeller q is approximately 1%, and the portion shown using the diagonal cross-sectional line in the upper right corner. is corroded, and the corrosion gradually decreases toward the outer periphery of the wall surface lO of the intermediate casing facing the back chamber lO of the impeller.

Figures 1 and 3 show that in pumps that handle electrolyte liquids, there is a phenomenon in which parts of the pump casing where the flow rate is low, such as near the pump shaft, corrode preferentially, and the cause is:
It was found that this was caused by macrocells formed due to the difference in flow velocity.

As described above, the inventors of the present invention determined through experiments and considerations the cause of preferential corrosion near the pump shaft in single-suction centrifugal pumps that handle electrolyte liquids.

As stated in the introduction, the purpose of the present invention is to prevent corrosion near the pump shaft of a pump casing that handles electrolyte such as seawater. By providing a fluid passage leading from the center portion of the shaft sealing portion to the low pressure portion of the pump chamber, the flow in the low flow rate portion is made more active.

Note that while conventional balance holes exist solely for the purpose of balancing the thrust load generated by the rotation of the impeller, the fluid passage according to the present invention has the function of balancing the thrust load as well. However, since the shaft center is actively moved closer to the shaft center, it brings about a completely new effect of preventing corrosion of the pump casing near the pump shaft.

The present invention will be described in detail below with reference to the drawings.

Ipc4I- is a vertical sectional view of a pump showing an embodiment of the present invention. The structure of the pump is the same as in Figure 1, and the pump casing is made of cast iron. In FIG. 1, only the reference numerals are shown for the parts explained in FIG. 1, and their explanation will be omitted.

The balance hole l13 has an opening end on the back chamber 10 side of the impeller close to the pump shaft 3, and a boss l13 toward the pump chamber low pressure part.
- Provided with pages running through the inside.

The shaft sealing house // has a conical end toward the balance hole // and the inlet //3 of the balance hole to improve the flow of the handled liquid.

In Figure D, when the impeller rotates, the liquid sucked in from the suction port as shown by arrow /7 (indicated by a thin line) is accelerated and pressurized by the impeller and exits from the volute chamber /II/C. The liquid is discharged from a discharge port following a spiral chamber ljK (not shown). The high-pressure liquid in the volute chamber/1 passes through the back side of the impeller main plate D and is ejected from the gap between the liner ring T and the wear ring part 6.
Liquid is an arrow / ? 'Intermediate casing-wall WJ
1611C, from the balance hole inlet //3 through the balance hole //, 7, it is sucked out to the pump chamber suction low pressure section, and the axial balance of the blade is maintained. Therefore, the surface facing the vicinity of the pump shaft 3 of the back chamber 10 of the impeller of the shaft sealing house // is in contact with the high-velocity flow indicated by the arrow /71. It is a diagram showing density. The vertical axis shows the corrosion current density μm A-, and the horizontal axis shows the pump operating time (months). 111/l shown by the dotted line is the change over time of the corrosion current density in the present invention, +111-〇 shown by the solid line. shows the corrosion current density of the pump casing with the conventional balance hole shown in FIG.

As is clear from the figure, in the conventional example 1, a large macroanode current flows near the pump shaft of the pump casing, but in the case of the present invention, a macroanode current of only 94% flows, and corrosion hardly progresses. I can hope that there will be no.

FIGS. 6 to 10 are longitudinal sectional views showing only essential parts of other embodiments of the present invention.

Figure 6 shows a short dead-end hole //3B drilled in the axial direction in the boss L of the impeller bow from the shaft seal side, and a hole //JCj diagonally directed from the pump chamber low pressure section toward the hole 1t3BK. It is something.

Figure 7 shows a hole in the impeller boss/JK axis direction//JD, which has the advantage of being easy to process.

Figure 1 shows the impeller boss/JK hole 3Ie (stopped in the axial direction from the side of the shaft sealing part) inserted deeply, and the hole //311 made from the pump chamber low pressure part side at the end and connected. be.

In the figure, a key groove l is provided in addition to the key groove that engages with the pump shaft 3 through a key in the hole into which the pump shaft 3 of the impeller boss l- is inserted, and grooves are provided in the radial direction on both end surfaces of the boss saw. This is what we set up here. This key #1 is provided on the boss l-, but a keyway is provided in addition to the keyway into which the key for transmitting rotational force is inserted into the pump shaft 3, and the grooves on both ends of the boss l- may be made to match.

Figure 10 shows a hole extending radially from the outer periphery of the pump shaft 3 that appears between the shaft sealing house and the end face of the impeller boss.
J is provided, and the center of the impeller l of the pump shaft 3 is connected to the VC6-shaped hole J4I so as to face the end in the axial direction, and the holes 3 in the radial direction are equally spaced. In this case, the flow indicated by arrow Cj is spirally radial along the end face /JK of shaft sealing house l/, at the entrance of hole 3 //, ? Liquid will flow in. Then pass through the hole in the center and exit from the center on the suction side of the pump chamber.

The back chamber of the impeller of the coaxial sealing house // in each of the above embodiments is 1 or
Since the fluid flows at a high speed on the wall surface facing 1c, corrosion in this part is not promoted by the flow rate difference macrocell, and instead tends to be cand, and corrosion is prevented.

Incidentally, each of the embodiments has the function of a balance hole, but when the balance force is insufficient, there is no problem in using a conventional balance hole in combination.

In each of the above embodiments, the holes for causing liquid flow in the vicinity of the pump shaft of the pump casing may be provided by casting or may be provided by machining.

In addition to the above, the present invention solves the phenomenon in which macrocorrosion current is generated due to the formation of flow velocity differential macrocells, which is the cause of rapid corrosion of conventional pump casings near the pump shaft in electrolyte bath liquids such as seawater. Therefore, in order to increase the flow rate of the handled liquid near the pump shaft of the pump casing, a liquid inflow passage inlet is provided on the shaft sealing side of the part near the center of the rotating body including the pump impeller, thereby reducing the pump chamber's low pressure. Since it penetrates into the pump shaft, corrosion of the pump casing near the pump shaft is eliminated, and the life of the pump can be significantly extended.

[Brief Description of the Drawings] Fig. 1 is a vertical cross-sectional view showing 9 parts of a conventional centrifugal pump, Fig. 2 is a diagram showing changes over time in the corrosion current density of the pump casing of Fig. 1, and Fig. 3 The figure is a longitudinal sectional view showing a part of the casing of the pump shown in Fig. 1, Fig. 1 is a longitudinal sectional view of an embodiment of the centrifugal pump of the present invention, and Fig. 3 is the corrosion current density of the casing of the pump shown in Fig. 6 to 10 are longitudinal sectional views showing other embodiments of the present invention. l...Casing Co...Intermediate casing 3...Pump shaft Da...Impeller j, 6...Wearing part?・・・
Impeller main plate lO・・Back chamber of impeller //・・Shaft sealing house Saw/boss /, 7. //, 7・@Balance Hall //3mu・Entrance of Balance Hall //, 7B
, //, 70. //, 7D. ti, yE, ii, yv-・hole /41・・song, I!
is... end face 16... wall surface /ri /71am arrow 15... spiral chamber /9. -〇...line here key groove here...groove 3. Koda...hole Ko1-arrow. Patent Applicant Ebara Corporation Agent Arai - Department Figure 1 Time (month) Figure 3 Figure 4 Figure 5 Daily MCFA) Figure 6 Figure 7v11 1 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] l In a single-suction dual-cabinet pump with a water seal ring between both sides of the impeller and the pump casing, there is a water seal between the back of the impeller and the water seal part of the pump casing at the center of the rotating body including the impeller. A centrifugal pump characterized in that a fluid passage is provided toward a low-pressure part of the pump chamber so that there is an inlet opening in the chamber on the horizontal axis side and into which liquid flows into the chamber, thereby preventing corrosion near the axis of the pump casing. .