Backflow channel arrangement in screw pumps

Abstract

The present invention relates to screw pumps, particularly to a backflow channel arrangement in screw pumps for discharging fluid accumulating in the sealed area separated from the high-pressure zone by a mechanical seal to the low-pressure pump suction side of the screw pump. More specifically, the invention proposes a screw pump (17), comprising a fluid inlet through which fluid is allowed to reach a low pressure suction side (21) of the screw pump (17) such that fluid is transferred to a high pressure zone (18) by rotation of a pump screw (24) and thereout to an outlet of the screw pump (17), said screw pump (17) further comprising a mechanical seal (19) to a sealed area (20).

Description

[0001] BACKFLOW CHANNEL ARRANGEMENT IN SCREW PUMPS

[0002] Technical Field of the Present Invention

[0003] The present invention relates to screw pumps, particularly to a backflow channel arrangement in screw pumps for discharging fluid accumulating in the sealed area separated from the high-pressure zone by a mechanical seal to the low-pressure pump suction side of the screw pump.

[0004] Background of the Present Invention

[0005] It is known that in screw pumps, the fluid being pumped which may leak from the high pressure zone through the mechanical seal to the sealed area should not accumulate in this area and cause high hydrostatic pressure. For this reason, the leaking fluid accumulating in the sealed area needs to be discharged on most practical way from this area and preferably to be transferred to the low pressure pump suction side of the pump.

[0006] According to a current practice in the technical field of screw pumps, for discharging the fluid leaking from the high pressure zone through the mechanical seal and accumulating in the sealed area, drilled through holes are provided, extending between the sealed area and the outside. In this case the fluid leaking through the mechanical seal in the sealed area will be discharged to the environment, which may cause undesired situations for example by dangerous fluids.

[0007] In another approach according to a vertically operating prior art plunger type model of the same product, the through hole has an extension which plunges in the fluid to be pumped, in this case oil, wherein the leaking oil flows from the sealed area to the oil tank with free flow. This solution is only applicable to vertically operating plunger type screw pumps.

[0008] According to another approach in a prior art screw pump, a connection duct is provided from the sealed area to the low pressure pump suction side, for being able to transfer the leaking fluid back to the pump suction side. This connection duct is a succession of channels in different directions, drilled in various materials of the screw pump body. It is worth noting that it is associated with additional production steps and assembly difficulties resulting in high effort and costs.

[0009] Yet according to another approach in a prior art embodiment, an external conduit is provided, from which the first end is connected to the aforementioned through hole between the sealed area and the outside and the other end to the low pressure pump suction side. The combination of the through hole, two connection mechanisms and the conduit is also associated with complex production steps and assembly difficulties resulting in high effort and costs. Additionally, this solution of an external conduit is less secure than a solution with internal channel.

[0010] One of the prior art documents available in the present technical field is CN 212985750 U disclosing a hollow screw, which is formed by sequentially connecting a tightening head part, a polished rod part and a screw rod part. The tightening head part, the polished rod part and the screw rod part are provided with axial through central holes, a spiral groove is formed in the outer surface of the polished rod part, and the groove bottom of the spiral groove penetrates through the hole wall of the central hole.

[0011] CN 201574941 U discloses a hollow single screw pump in which the screw has a through hole. In this document the only and main purpose of the hole is reducing the production effort and costs for the screw. In order to provide sealing of the high-pressure end and the low-pressure end, two sets of O-rings are arranged on both ends of the screw.

[0012] The present invention, on the other hand, utilizes the core concept that the shortest and most direct route that can be obtained from the sealed area to the low pressure suction side shall pass through the screw itself, particularly because this part already passes through the mechanical seal and extends from sealed area until the low pressure suction side. For this purpose, it is preferable to provide a through hole in the screw.

[0013] The invention not only solves the problem in the prior art, of discharging fluid leaking from the high-pressure zone through the mechanical seal in the sealed area with very practical and critical modifications and elements, but it contributes to important cost and effort savings with the additional benefits of lighter and better screw structure. The present invention proposes a system according to which, the fluid leaking / escaping from the high-pressure zone through mechanical seal and accumulating in the sealed area is transferred to the low-pressure suction side in a simple and economical way. In this way, the screw pump can work on both ways, namely as horizontal or vertical screw pump in the atmospheric environment and as a vertical plunger pump on a fluid surface with the pump part in the liquid. It is noted that in other known products, it is necessary to make changes for these two applications, while the screw pump of the invention is suitable for use in both ways.

[0014] According to the invention, also the need is eliminated, to provide an additional hole in the pump suction side for an inlet for discharged fluid.

[0015] Objects of the Present Invention

[0016] The aim of the invention is to improve the discharging of the fluid leaking from the high-pressure zone through the mechanical seal and accumulating in the sealed area in a practical manner with a novel approach using the best possible route between the sealed area and the low-pressure suction side.

[0017] Within this aim, an object of the invention is to provide a system according to which, the fluid escaping from the high-pressure zone through the mechanical seal and accumulating in the sealed area is transferred to the low-pressure suction side in a remarkably simple and economical way, namely through the pump screw itself.

[0018] Yet another object of the invention is to provide a screw pump which can work without essential modifications on both ways, namely as horizontal or vertical screw pump in the atmospheric environment and as a vertical plunger pump on a fluid surface with the pump part in the fluid.

[0019] Brief Description of the Technical Drawings

[0020] Accompanying drawings are given solely for the purpose of exemplifying a backflow channel arrangement in screw pumps, whose advantages over prior art were outlined above and will be explained in brief hereinafter.

[0021] The drawings are not meant to delimit the scope of protection as identified in the Claims, nor should they be referred to alone in an effort to interpret the scope identified in said Claims without recourse to the technical disclosure in the description of the present invention.

[0022] Figure 1 demonstrates a prior art application according to which a drilled hole is provided, extending between the sealed area and the outside,

[0023] Figure 2 demonstrates another prior art application in which the through hole has an extension which plunges in the fluid to be pumped, in this case oil.

[0024] Figure 3 demonstrates another prior art application according to which a connection duct is provided from the sealed area to the low-pressure pump suction side, for being able to transfer the leaking fluid back to the pump suction side,

[0025] Figure 4 demonstrates another prior art application in which, an external conduit is provided, from which the first end is connected to a through hole between the sealed area and the outside and the other end to the low-pressure pump suction side.

[0026] Figure 5 demonstrates an inner view of a screw pump according to a preferred embodiment of the present invention.

[0027] Figure 6 demonstrates a perspective cut-out view of a screw pump according to a preferred embodiment of the present invention.

[0028] Detailed Description of the Present Invention

[0029] The following numerals are referred to in the detailed description of the present invention:

[0030] 10 Radial rotor housing

[0031] 11 Rotor set

[0032] 12 Venting plug

[0033] 13 Pressure housing

[0034] 14 Key

[0035] 15 Non-return valve

[0036] 16 Flow direction

[0037] 17 Screw Pump

[0038] 18 High pressure Zone

[0039] 19 Mechanical seal

[0040] 20 Sealed area 21 Pump suction side

[0041] 22 Backflow channel (through hole)

[0042] 23 Backflow fluid

[0043] 24 Pump screw

[0044] 25 Safety valve

[0045] 26 First end

[0046] 27 Second end

[0047] 28 Pump outlet

[0048] Figure 1 demonstrates a prior art application according to which drilled through holes are provided, extending between the sealed area and the outside, for discharging the fluid escaping from the high-pressure zone through the mechanical seal and accumulating in the sealed area. The embodiment in Fig. 1 demonstrates a radial rotor housing (10), rotor set (12), a venting plug (11), a pressure housing (12), a key (13) and a non-return valve (13), also indicating flow directions (16).

[0049] Figure 2 shows another approach for a vertically operating prior art plunger type model of the same product, in which the backflow channel in the form of through hole has an extension which plunges in the fluid to be pumped, in this case oil, wherein the leaking oil flows from the sealed area to the oil tank with free flow.

[0050] Figure 3 shows another approach in a prior art screw pump, wherein a connection duct is provided from the sealed area to the low-pressure pump suction side, for being able to transfer the escaping fluid back to the pump suction side.

[0051] Figure 4 shows another approach in a prior art embodiment, wherein an external conduit is provided, from which the first end is connected to a through hole between the sealed area and the outside and the other end to the low- pressure pump suction side.

[0052] As known to the skilled reader, the fluid leaking from the high-pressure zone in screw pumps by passing through the mechanical seal should not accumulate in the sealed area for avoiding high hydrostatic pressure. Accordingly, it is desirable to transfer the fluid accumulating in this area to the low-pressure suction side of the screw pump. It is to be noted that all of the aforementioned examples of the prior art address this type of problem of discharging the fluid and / or transferring it to the suction side in their own way, whereas the invention presents an actual improvement for transferring the fluid from the sealing area to the low pressure suction side which brings a substantial difference in practice.

[0053] Figure 5 shows the preferred embodiment of the invention in which the reference numeral (17) refers to the screw pump according to the invention. In addition to the known parts of the screw pump (17), a backflow channel (22) in the form of through hole is provided, extending from the sealed area (20) to the low-pressure suction side (21) of the screw pump (17). The fluid being pumped usually enters the screw pump (17) through an inlet, reaches the low-pressure suction side (21) and is transferred to the high-pressure zone (18) by the rotation of the pump screw (24) and thereout to the outlet of the screw pump (17). As a result of the high pressure prevailing in the high- pressure zone (18) some amount of the fluid being pumped may leak through the mechanical seal (19) to the sealed area (20). In any case, it is necessary to discharge the fluid accumulating in the sealed area (20) in order to prevent building of hydraulic high pressure in this area.

[0054] The invention provides that the fluid leaking from the high-pressure zone (18) by passing through the mechanical seal (19) and accumulating in the sealed area (20) is transferred to the low-pressure suction side (21) in a simple and economical way. The backflow channel (22) in the form of through hole provided in the pump screw (24) body, which may be formed during casting of the same or obtained by machining as known in the prior art, provides a linear connection between the sealed area (20) and the low pressure suction side (21).

[0055] In an embodiment of the invention, a unidirectional safety valve (25) is provided on a first end (26) of the backflow channel (22) opening in the sealed area (20). When the pressure in the sealed area (20) rises, the safety valve (25) opens, allowing the fluid to pass to the suction side (21). In other embodiments, the safety valve (25) is located on a second end (27) of the backflow channel (22) opening in the low-pressure suction side (21). A flow from the suction side (21) to the sealed area (20) for any reason is thus precluded.

[0056] The invention solves the problem of discharging the fluid leaking from the high pressure zone (18) through the mechanical seal (19) and accumulating in the sealed area (20) and transferring the fluid to the low pressure suction side (21) in an improved and efficient manner, such that the screw pump (17) can work both as horizontal or vertical screw pump in the atmospheric environment and as a vertical plunger pump on a fluid surface with the pump part in the fluid.

[0057] Therefore, the most important advantage of the invention is that the fluid can be discharged from the sealed area (20) through a backflow channel (22) without the need for additional processing in the body or casing of the screw pump (17), which conveniently results in a lower cost with shorter manufacturing and assembly time; therefore ensuring a manufacturing process that is more reliable compared to applications involving processing from outside the body. In a nutshell, the present invention proposes a screw pump (17), comprising a fluid inlet through which fluid is allowed to reach a low pressure suction side (21) of the screw pump (17) such that fluid is transferred to a high pressure zone (18) by rotation of a pump screw (24) and thereout to an outlet of the screw pump (17), said screw pump (17) further comprising a mechanical seal

[0058] (19) to a sealed area (20).

[0059] According to an aspect of the invention, a backflow channel (22) in the form of through hole is provided, extending from said sealed area (20) to said low pressure suction side (21) of the screw pump (17) whereby any amount of fluid escaping through the mechanical seal (19) and accumulating in the sealed area

[0060] (20) as a result of the high pressure prevailing in the high pressure zone (18) is discharged buildup of hydraulic high pressure is prevented.

[0061] According to another aspect of the invention, said backflow channel (22) is configured to transfer the fluid escaping from the high-pressure zone (18) by passing through the mechanical seal (19) and accumulating in the sealed area (20) to the low-pressure suction side (21) of said screw pump (17).

[0062] According to another aspect of the invention, said backflow channel (22) is configured in the form of a through hole provided in the pump screw (24) body.

[0063] According to another aspect of the invention, said backflow channel (22) is formed during casting.

[0064] According to another aspect of the invention, said backflow channel (22) is configured to provide a linear connection between the sealed area (20) and the low-pressure suction side (21).

[0065] According to another aspect of the invention, said screw pump (17) comprises a unidirectional safety valve (25) such that when the pressure in the sealed area (20) rises, the safety valve (25) opens, allowing the fluid to pass to the suction side (21).

[0066] According to another aspect of the invention, said safety valve (25) is located on a first end (26) of the backflow channel (22) opening in the sealed area (20).

[0067] According to another aspect of the invention, said safety valve (25) is located on a second end (27) of the backflow channel (22) opening in the low-pressure suction side (21).

[0068] According to another aspect of the invention, said screw pump (17) is configured to work both as horizontal or vertical screw pump in the atmospheric environment and as a vertical plunger pump on a fluid surface with the pump part in the fluid.

Claims

CLAIMS1) A screw pump (17), comprising a fluid inlet through which fluid is allowed to reach a low pressure suction side (21) of the screw pump (17) such that fluid is transferred to a high pressure zone (18) by rotation of a pump screw (24) and thereout to an outlet of the screw pump (17), said screw pump (17) further comprising a mechanical seal (19) to a sealed area (20) characterized in that; a backflow channel (22) in the form of through hole is provided, extending from said sealed area (20) to said low pressure suction side (21) of the screw pump (17) whereby any amount of fluid escaping through the mechanical seal (19) and accumulating in the sealed area (20) as a result of the high pressure prevailing in the high pressure zone (18) is discharged buildup of hydraulic high pressure is prevented.2) A screw pump (17) as set forth in Claim 1, wherein said backflow channel (22) is configured to transfer the fluid escaping from the high pressure zone (18) by passing through the mechanical seal (19) and accumulating in the sealed area (20) to the low pressure suction side (21) of said screw pump (17).3) A screw pump (17) as set forth in Claim 1 or 2, wherein said backflow channel (22) is configured in the form of a through hole provided in the pump screw (24) body.4) A screw pump (17) as set forth in any preceding Claim, wherein said backflow channel (22) is formed during casting.5) A screw pump (17) as set forth in any preceding Claim, wherein said backflow channel (22) is configured to provide a linear connection between the sealed area (20) and the low-pressure suction side (21).6) A screw pump (17) as set forth in any preceding Claim, wherein said screw pump (17) comprises a unidirectional safety valve (25) such that when the pressure in the sealed area (20) rises, the safety valve (25) opens, allowing the fluid to pass to the suction side (21). 7) A screw pump (17) as set forth in Claim 6, wherein said safety valve(25) is located on a first end (26) of the backflow channel (22) opening in the sealed area (20).8) A screw pump (17) as set forth in Claim 6, wherein said safety valve (25) is located on a second end (27) of the backflow channel (22) opening in the low-pressure suction side (21).9) A screw pump (17) as set forth in Claim 6, wherein said screw pump (17) is configured to work both as horizontal or vertical screw pump in the atmospheric environment and as a vertical plunger pump on a fluid surface with the pump part in the fluid.

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