JPS58138281A - Pump subject to external pressure - Google Patents

Abstract

PURPOSE:To prevent corrosion, burning, abrasion, etc. by making a piston and cylinder with sintered tungsten carbide or copper alloy or stainless steel flame coated with tungsten carbide. CONSTITUTION:In a pump to be applied with external pressure by corrosive liquid such as water or sea water intruding into minute gap between a piston 7 and a cylinder 10, the piston 7 and the cylinder 10 is made of sintered tungsten carbide or copper alloy or stainless steel flame coated with tungsten carbide. Since the sintered tungsten carbide or the flame coated produce is higly corrosion resistant, the abrasion, corrosion, burning, etc. of the piston 7 and the cylinder can be prevented resulting in the stable pump performance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump that receives external pressure and is applicable to water or seawater pumps.

One conventional example of a water or seawater pump is shown in the drawing. The pump in the drawing is a crank type radial piston pump. In the figure, (1) is a casing, and the rotational movement of the crankshaft (4) supported by the casing (1) is
It is transmitted to the piston (7) via the connecting rod (3), pin (5), and os head (6), and the piston (
7) performs reciprocating motion, and the tip of the piston (7) projects into the valve chamber (11α) of the pulp block αυ.

Now, as mentioned above, when the piston (7) is reciprocally driven and first descends, the liquid flows into the suction port (ll) of the pulp block Ql.
j) is sucked into the valve chamber (11α) via the suction valve α. Next, the movement of the piston (in the upward direction of force) causes the valve chamber (11
When the tip of the piston (7) protrudes into (L), the pressure is increased and is discharged from the discharge port (llC) via the discharge valve 03).

Inside the crank chamber (2) is a crank main bearing (not shown),
It is filled with lubricating oil to lubricate the sliding surfaces of the bearing rod (3), pin (5), and crosshead (6), and the oil in the crank chamber (2) is released from the seal a to the outside. or conversely, leakage of external water or seawater (hereinafter referred to as pump peripheral water) into the crank chamber (2). Further, a cylinder 〇〇) fitted in the outer cylinder (9) is attached to the outer periphery of the piston (7).
) and the cylinder (1) to form a clearance seal.

In the discharge stroke, the water around the pump in the valve chamber (11 → leaks into the pump outside water chamber αe through the small gap between the piston (force) and the cylinder α1.Next, in the suction stroke, the water around the pump reaches the water velocity at the outside of the pump. It flows into the valve chamber (11→) through the through hole a!9 and the pump outer ice chamber 0Q. However, the amount of leakage is due to the minute gap between the piston (7) and the cylinder α, and the adjustment of the cylinder length. It is possible to make it below the allowable value. Note that αη is a convencator, and (17α) is a spring.

However, in the case of the water or seawater pump shown in the drawings, the piston (7) and cylinder (10) are directly exposed to water or seawater, that is, the pump's circumferential water, resulting in the following problems. That is, l) The water surrounding the pump, such as water or seawater, has a corrosive effect;
Seawater is particularly corrosive.

2) Water around the pump, such as water or seawater, has a much lower lubricating ability than oil and is more likely to cause wear and seizure of the piston (power and cylinder).

3) If foreign matter, especially sand and mud, contained in the water surrounding the pump such as water or seawater enters between the piston (7) and the cylinder a1, it will cause large upheaval wear.

Conventionally, piston materials and cylinder materials have been selected in consideration of such problems.

Conventionally used materials for cylinder materials are copper alloys and fired ceramic crystals such as alumina oxide. The piston materials used include copper alloys such as aluminum bronze, copper alloys, stainless steel, and ceramic sprayed materials such as alumina oxide and chromium oxide. However, these combinations could not solve all of the problems 1), 2), and 8) above.

If corrosion-resistant copper alloy is used for the cylinder material,
Although the same alloy has better anti-seizure performance, the wear due to contact with the piston (7) and wear due to sand and mud is large, and the piston (
7) and the cylinder (10) becomes larger,
This had the disadvantage that the amount of leakage increased and pump performance deteriorated.

In addition, the rigidity of the copper alloy cylinder has a small Young's modulus, so
When the ambient pressure of the water around the pump is high or the discharge pressure is high, the cylinder deforms greatly due to the water pressure around the pump.
If the minute gap expands or water pressure is applied to the back of the cylinder, the minute gap becomes smaller and smaller, which has the disadvantage of causing contact with the piston (force).

Further, when a fired ceramic crystal such as alumina is used for the cylinder material, it is necessary to use ceramics for the piston material as well, considering the wear resistance of the piston (7). Ceramic fired crystals such as alumina and chromium oxide are susceptible to bending failure and are not suitable for long and slender piston materials. Therefore, piston materials are usually made of copper alloy or stainless steel, which have excellent corrosion resistance, as a base material to ensure strength, and ceramics are sprayed onto the base material.

Ceramics themselves have high corrosion resistance, but when thermally sprayed, the corrosion resistance of the bonding surface between the thermally sprayed ceramic layer and the base material decreases, and especially in the case of highly corrosive liquids such as seawater, corrosion can occur. It progresses and has drawbacks such as hakusu. Additionally, the surface hardness of a ceramic sprayed layer is generally lower than that of a sintered product. Therefore, the hardness of the ceramic sprayed piston is lower than that of the ceramic sintered cylinder. Therefore, due to the surface roughness of the ceramic sintered cylinder,
The disadvantage was that the piston surface was scraped and the piston was prone to wear.

The present invention has been proposed in order to solve the above-mentioned conventional drawbacks, and the piston and cylinder are made of sintered tungsten carbide or a thermally sprayed layer of tungsten carbide sprayed onto a base material such as copper alloy or stainless steel. The present invention aims to provide a pump whose pistons and cylinders are subjected to external pressure without problems such as corrosion, seizure, and wear.

The present invention will be described in detail below. As shown in the drawings, the piston (
In a pump that receives external pressure, a corrosive liquid such as water or seawater enters a minute gap between the piston (7) and the cylinder α0).
The material of IOl is a sintered product of tungsten carbide, or a thermally sprayed layer formed by thermally spraying tungsten carbide using a copper alloy or stainless steel as a base material.

The sintered crystal of tungsten carbide has a transverse rupture strength of 180 k.
g/in' or more, Vickers hardness 1800I19/mm
', and Young's modulus of 5.4xlO'IIg/-.

Corrosion resistance against pump peripheral water such as water or seawater varies depending on the type of binder, but if nickel is used as the binder, for example, sufficient corrosion resistance is achieved.

On the other hand, if a base material with excellent corrosion resistance is used, a tungsten carbide sprayed layer will have superior corrosion resistance compared to a ceramic sprayed layer such as alumina, and will corrode more rapidly than the joint surface between the sprayed layer and the base material. There is no progress. In addition, the shearability of tungsten carbide in water is
Tungsten carbide has the above-mentioned characteristics, and is used in sliding rings of mechanical seals, etc., and is almost as good as ceramic materials. By using it for piston and cylinder materials for seawater pumps, the following effects occur.

l) Even in water or seawater (water around the pump),
There are no problems with corrosion of the piston or cylinder.

2) Both the piston and cylinder are hard, so
Even if the piston and cylinder come into contact, there is little wear. In addition, since tungsten carbide is harder than the sand and mud contained in water and seawater (water around the pump), there is no wear due to sand and mud, and the gap between the piston and cylinder increases due to wear, which reduces performance. Never.

8) Also, since tungsten carbide has a large transverse rupture strength, a piston can be made by sintering, and it can be manufactured from the same material as the piston and cylinder.

Even in the case of the same type of material, only one side of the piston or cylinder will not be scraped by the surface roughness of the other side.
They will wear together and you can expect good staining.

4) Tungsten carbide has a Young's modulus of 2 compared to steel.
Even in the case of ultra-high pressure discharge pumps, the deformation of the cylinder is small, and it is easy to secure a small gap between the cylinder and the piston. ) Stable pump performance can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawing is a longitudinal sectional view of a conventional general water or seawater pump. Explanation of the main parts of the diagram? ...Piston lO...Cylinder patent
Applicant: Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] In pumps that are exposed to external pressure, where corrosive liquids such as water or seawater enter the minute gap between the piston and cylinder, the piston and cylinder are made of sintered crystal tungsten carbide, or a base material such as copper alloy or stainless steel. A pump that receives external pressure and is characterized by being a thermally sprayed product coated with tungsten carbide.