US20080003117A1

US20080003117A1 - Gas-operated diaphragm dosing pump

Info

Publication number: US20080003117A1
Application number: US11/808,779
Authority: US
Inventors: Nils Kohlhase
Original assignee: Individual
Current assignee: Lewa GmbH
Priority date: 2006-06-12
Filing date: 2007-06-12
Publication date: 2008-01-03
Also published as: CA2591378A1; DE102006027208A1

Abstract

A diaphragm dosing pump with a gas-operated drive, in particular for adding in a dosed manner adjuvants into gas pipelines, for example a natural gas well, having a drive head for the diaphragm dosing pump, a drive rod moving back and forth in a cylinder chamber of the drive head, which carries a drive part separating the cylinder chamber into two chambers and is effectively connected to a piston rod of the diaphragm dosing pump. A feeding pipeline is connected to the cylinder chamber of the drive head for pressurized gas from the gas pipeline. A control valve is located between the gas feeding pipeline as well as an outlet for the relaxed gas to return to the gas pipeline. The arrangement is made such that the drive head of the diaphragm dosing pump is embodied as a simple operating gas drive such that only the pressure stroke side of the drive head is connected via the control valve to the pressurized gas feeding pipeline while the suction stroke side of the drive head is connected at all times to the gas outlet and that on the suction stroke side of the drive head a spring is provided, which acts upon the drive part in the direction of the suction stroke.

Description

FIELD OF THE INVENTION

The invention relates to a diaphragm dosing pump with a gas-operated drive, in particular for dosing adjuvants in gas pipelines, for example a natural gas well.
The invention also relates to a method for controlling the gas-operated drive.

BACKGROUND OF THE INVENTION

Dosing pumps with gas-operated drives have been known for quite some time and are preferably used for dosing adjuvants, e.g., corrosion inhibitors, in gas pipelines near or at a natural gas well. Gas wells sometimes have low production and are dispersed over remote areas, so that electric energy for driving a dosing pump can only be provided at great expense. Therefore, preferably the gas of the gas well is used as the pressure medium for driving the dosing pump. In the past, the used gas was usually blown off into the environment, which is undesirable, of course, for economic reasons as well as for pollution.
In order to avoid this it has been known (U.S. Pat. No. 6,694,858) to provide a gas drive as the drive used for an oscillating displacement pump, in which the pressurized gas taken from a gas pipeline is fed via an appropriate control valve to the displacement pump such that the gas alternatingly impinges both sides of the displacement piston and/or operates both in a pressurized stroke direction as well as in a suction stroke direction, after which the pressurized gas is returned to the gas pipeline at a low-pressure side.
For this purpose it is necessary for a certain pressure difference to be present in the gas pipeline, e.g., at a constriction of the pipeline or at a flow meter created, for example, in the form of a metering orifice, or that the pressure difference is artificially created by the use of a throttle.
This known gas drive is disadvantageous, though, in that the entire construction including the associated control is designed rather expensively and the gas consumption is very high.

SUMMARY OF THE INVENTION

The present invention is therefore based on the object to provide a diaphragm dosing pump of a generic type for avoiding the disadvantages shown such that the gas drive is designed in a very simple constructive manner and only uses low gas consumption. Additionally, a simple method is provided to control such a drive.
The invention is based on the idea to embody the drive head of a diaphragm dosing pump as a simply operating gas drive, namely such that only the pressure stroke side of the drive head is connected to the feeding pipeline of the pressurized gas via a control valve, while a spring is attached on the suction stroke side of the drive head, which affects the drive part in the direction of the suction stroke. Additionally, the suction stroke side of the drive head is connected at all times to the pressurized gas outlet, i.e., to an area of a lower gas pressure. This way an essential advantage results in that the drive can be operated independently of the amount of pressure in the pipeline.
In one embodiment according to the present invention the control valve is designed such that it opens a feeding pipeline of a pressurized gas flow towards the pressure stroke side of the drive head for performing the pressure stroke of the drive head, while the suction stroke for removing the gas is then relaxed causing the gas output to be opened.
This means that, in the sense of the invention, the oscillating motion of the gas drive occurs in a very simple manner, preferably controlled mechanically, by switching on the influx of pressurized gas for the pressure stroke of the drive head. In contrast, in an extraordinarily simple constructive manner the spring force is used for the suction stroke of the drive head, which then returns the now relaxed gas located in the cylinder space of the drive head at the pressure stroke side into the gas pipeline, namely at the low-pressure side.
Preferably, a diaphragm pump head with a hydraulic diaphragm drive is used as the dosing unit. This provides two essential advantages, namely that, on the one hand, the dosing occurs leak-free and, on the other hand, the piston moving back and forth in the hydraulic oil operates almost without any friction.
Therefore, only the pressure stroke of the drive head and thus also the diaphragm pump head requires only a certain low pressure force to overcome the spring force. Therefore, in addition to this pressure force, practically no additional forces are to be considered or to be overcome, because the friction force is negligibly low in reference to the pressure force.
For this reason it is possible to operate the diaphragm dosing pump by the gas-operated drive according to the invention even when there is a very low pressure difference in the gas pipeline, for example, less than 0.5 bar.
The gas-operated drive according to the invention therefore uses the energy of the gas transported in the gas pipeline for only the pressure stroke of the drive head. In contrast thereto, the suction stroke occurs via spring force. This way the overall control is designed much simpler and more cost-effective than the known drives using a dual-action drive.
In another embodiment of the invention it is advantageous for the drive head to be embodied as a diaphragm drive, with its drive part being a diaphragm member. This way the friction loss can be reduced to a minimum so that the drive can be operated under an even lower pressure difference in the gas pipeline.
The diaphragm member of the gas-operated diaphragm drive can be a single diaphragm, a dual diaphragm, or a roller diaphragm.
Instead, it is also possible to provide a piston drive as the drive head, with its driving part being a piston.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the following drawings, the invention is explained in greater detail:
FIG. 1 schematically illustrates, in cross-section, a diaphragm dosing pump with a very simple operating gas drive in the form of a drive head, which is embodied as a diaphragm drive having a single diaphragm,
FIG. 2 is a modified embodiment with a simple operating gas drive in the form of a diaphragm drive having a dual diaphragm, and
FIG. 3 is another modified embodiment with a gas drive in the form of a piston drive.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As discernible from FIG. 1, a diaphragm dosing pump 1 is provided, which in the exemplary embodiment shown is embodied as a diaphragm pump with a hydraulically operating diaphragm drive. For this purpose the diaphragm dosing pump 1 is provided with a piston rod 3, moving back and forth in a pump body 2, which acts upon an operating chamber 4, filled with hydraulic oil and formed in a pump body 2, in the sense of a pressure stroke—in FIG. 1 in the movement towards the left, and/or a suction stroke, in FIG. 1 in the movement towards the right.
The pump body 2 is closed by a pump lid 5, in which a conveying space 6 is formed for conveying a dosing medium via an inlet valve 7 as well as an outlet valve 8.
The operating chamber 4 and the conveying chamber 6 are separated by a diaphragm 9, which is stretched between the pump body 2 and the pump lid 5 and which is operated via the piston rod 3 moving axially back and forth in the hydraulic oil located in the operating chamber 4 in the sense of a pressure stroke as well as a suction stroke.
The piston rod 3 of the diaphragm dosing pump 1 is mechanically operated, namely by a gas-operated drive 10, which is embodied as a simple operating gas drive. For this purpose a drive head 11 is provided, which encloses a cylinder chamber 12. Here, a drive rod 13 is mobile back and forth, which on the one side at its end protruding from the cylinder chamber 12 of the drive head 11 is connected to the piston rod 3 of the diaphragm dosing pump 1 and/or embodied with it in one piece and on the other side it carries a drive part in the form of a simple diaphragm 14 at its end located in the cylinder chamber 12 of the drive head 11. The diaphragm 14 separates the cylinder chamber 12 of the drive head 11 into two chambers in the manner shown, namely into a pressure stroke side chamber 15 as well as a suction stroke side chamber 16.
In the suction stroke side chamber 16 of the drive head 11 a pressure spring 17 is arranged on the drive rod 13, which on the one side is supported at the wall of the cylinder chamber 12 and on the other side at a single diaphragm 14 and/or at its carrier part such that therefore the single diaphragm 14 is spring-loaded in the direction of the suction stroke of the drive head 11—in FIG. 1 towards the right.
At the same time, the suction stroke side chamber 16 is also constantly connected to the gas output 21, so that the suction stroke side chamber 16 is always acted upon by a lower gas pressure site P2 in pipeline 18 represented by “−”.
The pressure stroke of the drive head 11—in FIG. 1 towards the left—is caused by the pressurized gas in gas pipeline 18, for example, at or near a natural gas well at a higher pressure site P1 in pipeline 18 represented by “+”, and is fed via a feeding pipeline 19 to the pressure stroke side chamber 15 of the drive head 11.
Additionally, a control valve 20 is provided in the feeding pipeline 19, which guides the relaxed gas back into the primary gas pipeline 18 via an output 21, after it has executed the pressure stroke in the pressure stroke side chamber 15, namely at a downstream lower gas pressure site P2. Here, a pressure difference between P1 and P2 of less than 0.5 bar is sufficient, as already shown, in order to operate the drive head 11, i.e., to impinge the pressure stroke side chamber 15 with pressurized gas in the sense of a pressure stroke. The pressure difference may be created, for example, by a blind 23 in the pipeline 18.
The control valve 20 is designed such that it opens the pressurized gas influx via the feeding pipeline 19 to the pressure stroke side 15 of the drive head 11 for performing the pressure stroke of the drive head 11—in FIG. 1 towards the left—while in the suction stroke of the drive head 11—in FIG. 1 towards the right—it opens the outlet 21 to remove the gas then relaxed or expanded so that the relaxed or expanded gas is returned via this output 21 at the lower gas pressure in site P2 in the primary gas pipeline 18.
The control of the control valve 20 occurs mechanically in the manner shown via rod 22 moving about a pivot point as shown by a curved arrow, which is operated in turn via the respective axial position of the drive rod 13 of the drive head 11 and/or the piston rod 3 of the diaphragm dosing pump 1.
The modified embodiment according to claim FIG. 2 is different from the one according to FIG. 1 only in that instead of the single diaphragm 14 of the drive head 11, dual diaphragms 14′ are provided.
In an appropriate manner, in the embodiment according to FIG. 3, the drive head is not embodied as a diaphragm drive but as a piston drive, with its drive part being a piston 14″.
Reference is made explicitly to the claims as well as the drawing with regard to features of the invention not explained in greater detail above.

Claims

1. In combination, a diaphragm dosing pump and a gas-operated drive for dosing adjuvants into gas pipelines of a natural gas well, said combination comprising

a drive head of the gas operated drive, said drive head having a cylinder chamber,

a drive rod movable back and forth in the cylinder chamber of the drive head,

a drive part separating the cylinder chamber into a pressure stroke side chamber and a suction stroke side chamber, said drive part being connected to a piston rod of the diaphragm dosing pump by the drive rod,

a feeding pipeline connected at one end to the pressure stroke side chamber of the cylinder chamber of the drive head, and

a control valve connected at the other end of the feeding pipeline, the control valve being movable for controlling flow of gas from the feeding pipeline and the cylinder chamber of the drive head to a gas pipeline,

the drive head being alternatingly connected via the control valve to the feeding pipeline and the pressure stroke side chamber of the drive head and to the suction stroke side chamber of the drive head by a gas outlet from the suction stroke side chamber, and

a spring in the suction stroke side chamber of the drive head being biased in a direction of the pressure stroke side chamber.

2. The combination according to claim 1, wherein the control valve is open for performing a pressure stroke of the drive head by connection with the feeding pipeline.

3. The combination according to claim 1, wherein control of the control valve occurs mechanically via a rod operated via axial movement of at least one of the piston rod of the diaphragm dosing pump and the drive rod of the drive head.

4. The combination according to claim 1, wherein the diaphragm dosing pump operated by the gas-operated drive is a hydraulically operating diaphragm pump, with the piston rod in a connection with the drive rod of the drive head.

5. The combination according to claim 1, wherein the drive head is a diaphragm drive, and the drive part is a diaphragm member.

6. The combination according to claim 5, wherein the diaphragm member is a single diaphragm.

7. The combination according to claim 5, wherein the diaphragm member is a dual diaphragm.

8. The combination according to claim 5, wherein the diaphragm member is a rolling diaphragm.

9. The combination according to claim 1, wherein the drive head is a piston drive, and the drive part is a piston.

10. A method for controlling a gas operated drive of a diaphragm dosing pump, said method comprising the steps of

moving a drive part, on one hand, during a pressure stroke by impinging a pressure stroke side chamber of a drive head with pressurized gas and, on the other hand, during a suction stroke by impinging a suction stroke side chamber of the drive head with a spring force.

11. The method according to claim 10, wherein the pressure stroke of the drive part is introduced by opening a connection between the pressure stroke side chamber of the drive head and a first location of a pressurized gas feeding pipeline.

12. The method according to claim 11, wherein the suction stroke of the drive part is introduced by closing the connection between the pressurized gas feeding pipeline and the pressure stroke side chamber of the drive head by a spring force as well as by a connection between a suction stroke side chamber and a second location of the pressurized gas feeding pipeline with a lower pressure than said first location.