Circulating water system of drainage pumping station
By designing a circulating water system for the drainage pumping station, the reuse and temperature regulation of production water were achieved, solving the problems of non-recyclable production water and freezing under extreme weather conditions, thus improving the safety of the water supply system and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2026-03-31
AI Technical Summary
In existing technologies, the production water used in drainage pumping stations cannot be effectively recycled and reused, and it is prone to freezing in extreme weather conditions, affecting the safe operation of the pumping stations.
A circulating water system for a drainage pumping station was designed. The system connects to the municipal water network, pumping station reservoir, cooling tower, booster pump, and filter through pipelines to achieve the reuse of production water and temperature regulation, ensuring that the water source does not freeze under extreme weather conditions.
It enables the reuse of production water, reduces water consumption, improves the safety and stability of the water supply system, reduces the threat of extreme weather to water supply, and reduces the cost of drainage pumping stations.
Smart Images
Figure CN224063639U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of drainage pumping station technology, specifically to a circulating water system for a drainage pumping station. Background Technology
[0002] In urban drainage systems, pumping stations that use dry axial flow pumps and mixed flow pumps as the main pumps have a very high demand for production water. Production water is mainly used for cooling the main pump bearing lubrication tank, mechanical seals, impeller flushing, and flushing of the pumping station site and bar screen cleaning machine. If there are problems with the production water supply system, it will affect the operation of the pumps, and in severe cases, it will affect the normal delivery of the drainage pumping station. Therefore, ensuring a stable production water supply is extremely important for the safe operation of the drainage pumping station.
[0003] In existing technologies, the cooling water for the main pump seal, the impeller flushing water, and the screen cleaning water cannot be recycled and are mostly discharged directly. Furthermore, existing technologies do not make full use of the heat of the production water. In extreme cases or when the weather temperature is low, the production water may freeze and solidify, preventing it from flowing and circulating into the cooling system, which can seriously affect production operations. Utility Model Content
[0004] (a) Technical problems to be solved
[0005] In view of the shortcomings of the prior art, this utility model provides a circulating water system for a drainage pumping station to solve the problems mentioned in the background.
[0006] (II) Technical Solution
[0007] To achieve the above objectives, this utility model provides the following technical solution: a circulating water system for a drainage pumping station, comprising a municipal pipeline inlet and a pumping station reservoir. The municipal pipeline inlet and the pumping station reservoir are connected by a pipeline. A first booster pump and a first connecting pipe are installed at the end of the pumping station reservoir away from the municipal pipeline inlet. A second connecting pipe is installed at the end of the first connecting pipe away from the pumping station reservoir. A main pumping station is installed at the end of the second connecting pipe away from the first connecting pipe. A third connecting pipe, a first three-way valve, and a main sewage pipe are installed outside the main pumping station. A fourth connecting pipe and a main collection pipe are installed outside the first three-way valve. The fourth connecting pipe is located away from the first three-way valve. A cooling tower is installed at one end of the valve. A fifth connecting pipe, a second booster pump, and a first return water pipe are installed at the end of the cooling tower away from the fourth connecting pipe. A second three-way valve, a first auxiliary collecting pipe, and a second auxiliary collecting pipe are installed at the end of the main collecting pipe away from the first three-way valve. A return water collection tank is installed at the end of the second auxiliary collecting pipe away from the main collecting pipe. A third booster pump and a sixth connecting pipe are installed at the end of the return water collection tank away from the second auxiliary collecting pipe. A sedimentation tank, an auxiliary connecting pipe one, a main filter, an auxiliary connecting pipe two, a fourth booster pump, and a constant pressure filter are installed sequentially at the end of the main sewage pipe away from the main pump station. A second return water pipe is installed at the end of the constant pressure filter away from the main sewage pipe.
[0008] Preferably, the first connecting pipe is connected to the second connecting pipe, a check valve is provided on the outside of the first connecting pipe, the third connecting pipe, the fourth connecting pipe and the main collecting pipe are respectively connected to the three ends of the first three-way valve, the two ends of the first return water pipe are respectively connected to the pump station reservoir and the fifth connecting pipe, the second connecting pipe, the third connecting pipe, the fourth connecting pipe, the main collecting pipe, the first auxiliary collecting pipe, the second auxiliary collecting pipe and the sixth connecting pipe are made of PPR pipe or cast iron composite pipe with anti-corrosion lining, and the second connecting pipe, the third connecting pipe, the fourth connecting pipe, the main collecting pipe, the first auxiliary collecting pipe, the second auxiliary collecting pipe and the sixth connecting pipe are fully enclosed pressure-bearing pipes.
[0009] Through the above technical solution, during use, the municipal water supply outlet delivers municipal water to the pump station's reservoir. The first booster pump, through the first connecting pipe, delivers production water to the main pump station via the second connecting pipe, cooling the lubrication tank of the main pump bearing in the main pump station. The used water is then delivered to the cooling tower via the third connecting pipe, the first three-way valve, and the fourth connecting pipe. The cooling tower cools the production water, and the cooled production water is returned to the pump station's reservoir via the fifth connecting pipe, the second booster pump, and the first return water pipe, thus achieving the reuse of production water and reducing water consumption.
[0010] Preferably, the main collecting pipe, the first auxiliary collecting pipe, and the second auxiliary collecting pipe are respectively connected to the second three-way valve, the end of the first auxiliary collecting pipe away from the second three-way valve is connected to the second connecting pipe, and the sixth connecting pipe is connected to the second connecting pipe.
[0011] Preferably, a check valve is provided at the end of the sixth connecting pipe and the first auxiliary collecting pipe near the second connecting pipe, and both the second auxiliary collecting pipe and the sixth connecting pipe are connected to the return collection tank.
[0012] Preferably, the return water collection tank is located on the lower level of the main pump station. The storage capacity of the return water collection tank is such that it can receive the cooling water output of no less than two main pumps per unit time. The number of the third booster pumps is no less than two. The return water collection tank is also connected to the first return water pipe through a return pipe and a liquid pump.
[0013] Through the above technical solution, during winter use, the hot production water from the main pumping station is transported to the first or second auxiliary collection pipe through the third connecting pipe, the first three-way valve, and the second three-way valve. When higher-temperature production water is needed, it can be directly returned to the second connecting pipe through the first auxiliary collection pipe. When lower-temperature production water is needed, it can be returned to the second connecting pipe through the second auxiliary collection pipe, the return collection tank, the third booster pump, and the sixth connecting pipe. The production water returned to the collection tank can be returned to the pumping station's water storage tank through the return pipe and the pump. This ensures that the production water in the pumping station's water storage tank will not freeze, reduces the threat of extreme freezing weather to the water supply tank and pipelines, and improves the safety and stability of the water supply network.
[0014] Preferably, the sedimentation tank is connected to the main filter through a secondary connecting pipe one, the main filter and the constant pressure filter are connected to the fourth booster pump through a secondary connecting pipe two, the constant pressure filter is connected to the first return water pipe through a second return water pipe, and the main sewage pipe, secondary connecting pipe one and secondary connecting pipe two are made of PVC pipe or UPVC pipe.
[0015] Preferably, both the end of the fifth connecting pipe furthest from the cooling tower and the end of the second return water pipe furthest from the constant pressure filter are equipped with check valves.
[0016] With the above technical solution, during use, the water output from the main pump mechanical seal, the impeller flushing water of the drainage pump station, and the bar cleaning water can be collected in the sedimentation tank through the main sewage pipe for sedimentation. The settled water is then transported to the first return water pipe through the auxiliary connecting pipe 1, the main filter, the auxiliary connecting pipe 2, the fourth booster pump, the constant pressure filter, and the second return water pipe. This allows for the reuse of wastewater, reduces water consumption, and also lowers the cost of the drainage pump station.
[0017] Compared with the prior art, the present invention provides a circulating water system for a drainage pumping station, which has the following beneficial effects:
[0018] 1. The circulating water system of this drainage pumping station is equipped with a main pumping station, a cooling tower, a third connecting pipe, a fourth connecting pipe, a fifth connecting pipe, a second booster pump, a first return water pipe, and a pumping station water storage tank. The production water used by the main pumping station can flow into the cooling tower through the third and fourth connecting pipes for cooling. The cooled production water can then flow back into the pumping station water storage tank through the second booster pump, the fifth connecting pipe, and the first return water pipe, thus realizing the reuse of production water and reducing water consumption.
[0019] 2. The circulating water system of this drainage pumping station: After the main pumping station is used, the hot production water is transported to the first or second auxiliary collection pipe through the third connecting pipe, the first three-way valve and the second three-way valve. When higher temperature production water is required, it can be directly returned to the second connecting pipe through the first auxiliary collection pipe. When lower temperature production water is required, it can be returned to the second connecting pipe through the second auxiliary collection pipe, the return collection tank, the third booster pump and the sixth connecting pipe. The production water in the return collection tank can be returned to the pumping station's water storage tank through the return pipe and the pump. This ensures that the production water in the pumping station's water storage tank will not freeze, reduces the threat of extreme freezing weather to the water supply tank and pipelines, and improves the safety and stability of the water supply network.
[0020] 3. The circulating water system of this drainage pumping station allows the main pump mechanical seal output water, drainage pumping station impeller flushing water, and bar screen cleaning water to be collected in a sedimentation tank through the main sewage pipe for sedimentation. The settled water is then transported to the first return water pipe through secondary connecting pipe one, main filter, secondary connecting pipe two, fourth booster pump, constant pressure filter, and second return water pipe. This enables the reuse of wastewater, reduces water consumption, and also reduces the cost of the drainage pumping station. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the overall system structure of this utility model;
[0022] Figure 2 This is a schematic diagram of the circulating water utilization system of this utility model. Figure 1 ;
[0023] Figure 3 This is a schematic diagram of the circulating water utilization system of this utility model. Figure 2 .
[0024] The system includes: 1. Municipal water supply inlet; 2. Pump station reservoir; 3. First booster pump; 4. First connecting pipe; 5. Second connecting pipe; 6. Main pump station; 7. Third connecting pipe; 8. First three-way valve; 9. Fourth connecting pipe; 10. Cooling tower; 11. Fifth connecting pipe; 12. Second booster pump; 13. First return water pipe; 14. Main collection pipe; 15. Second three-way valve; 16. First auxiliary collection pipe; 17. Second auxiliary collection pipe; 18. Return collection water tank; 19. Third booster pump; 20. Sixth connecting pipe; 21. Main sewage pipe; 22. Sedimentation tank; 23. Auxiliary connecting pipe one; 24. Main filter; 25. Auxiliary connecting pipe two; 26. Fourth booster pump; 27. Constant pressure filter; 28. Second return water pipe; 29. Return pipe; 30. Liquid pump. Detailed Implementation
[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0026] Example 1:
[0027] like Figure 1-3 As shown, the present invention provides a circulating water system for a drainage pumping station, including a municipal pipeline inlet 1 and a pumping station reservoir 2. The municipal pipeline inlet 1 and the pumping station reservoir 2 are connected by a pipeline. A first booster pump 3 and a first connecting pipe 4 are installed at the end of the pumping station reservoir 2 away from the municipal pipeline inlet 1. A second connecting pipe 5 is installed at the end of the first connecting pipe 4 away from the pumping station reservoir 2. A main pumping station 6 is installed at the end of the second connecting pipe 5 away from the first connecting pipe 4. A third connecting pipe 7, a first three-way valve 8, and a main sewage pipe 21 are installed outside the main pumping station 6. A fourth connecting pipe 9 and a main collection pipe 14 are installed outside the first three-way valve 8. A cooling tower 10 is installed at the end of the fourth connecting pipe 9 away from the first three-way valve 8. One end of the four connecting pipes 9 is provided with a fifth connecting pipe 11, a second booster pump 12 and a first return water pipe 13. The end of the main collection pipe 14 away from the first three-way valve 8 is provided with a second three-way valve 15, a first auxiliary collection pipe 16 and a second auxiliary collection pipe 17. The end of the second auxiliary collection pipe 17 away from the main collection pipe 14 is provided with a return collection water tank 18. The end of the return collection water tank 18 away from the second auxiliary collection pipe 17 is provided with a third booster pump 19 and a sixth connecting pipe 20. The end of the main sewage pipe 21 away from the main pump station 6 is provided with a sedimentation tank 22, an auxiliary connecting pipe 1 23, a main filter 24, an auxiliary connecting pipe 2 25, a fourth booster pump 26 and a constant pressure filter 27. The end of the constant pressure filter 27 away from the main sewage pipe 21 is provided with a second return water pipe 28.
[0028] Specifically, the first connecting pipe 4 is connected to the second connecting pipe 5. A check valve is installed on the outside of the first connecting pipe 4. The third connecting pipe 7, the fourth connecting pipe 9, and the main collecting pipe 14 are respectively connected to the three ends of the first three-way valve 8. The two ends of the first return water pipe 13 are respectively connected to the pump station reservoir 2 and the fifth connecting pipe 11. The second connecting pipe 5, the third connecting pipe 7, the fourth connecting pipe 9, the main collecting pipe 14, the first auxiliary collecting pipe 16, the second auxiliary collecting pipe 17, and the sixth connecting pipe 20 are made of either PPR pipe or cast iron composite pipe with anti-corrosion lining. The connecting pipe 20 is a fully enclosed pressure-bearing pipe. Its advantage is that during use, the municipal water supply outlet 1 delivers municipal water to the pump station's water storage tank 2. The first booster pump 3 delivers production water to the main pump station 6 through the first connecting pipe 4 and the second connecting pipe 5, which cools the lubrication oil tank of the main pump bearing of the drainage pump station inside the main pump station 6. The used water is then delivered to the cooling tower 10 through the third connecting pipe 7, the first three-way valve 8, and the fourth connecting pipe 9. The cooling tower 10 cools the production water. The cooled production water then flows back to the pump station's water storage tank 2 through the fifth connecting pipe 11, the second booster pump 12, and the first return water pipe 13, thereby realizing the reuse of production water and reducing water consumption.
[0029] Example 2:
[0030] like Figure 1-3 As shown, this is an improvement on the previous embodiment.
[0031] Specifically, the main collection pipe 14, the first auxiliary collection pipe 16, and the second auxiliary collection pipe 17 are respectively connected to the second three-way valve 15. The end of the first auxiliary collection pipe 16 away from the second three-way valve 15 is connected to the second connecting pipe 5. The sixth connecting pipe 20 is connected to the second connecting pipe 5. Check valves are installed at the ends of the sixth connecting pipe 20 and the first auxiliary collection pipe 16 near the second connecting pipe 5. The second auxiliary collection pipe 17 and the sixth connecting pipe 20 are both connected to the return collection tank 18. The return collection tank 18 is located on the lower level of the main pump station 6. The storage capacity of the return collection tank 18 is such that it can receive the cooling water output of no less than two main pumps per unit time. The number of third booster pumps 19 is no less than two. The return collection tank 18 is also connected to the first return water pipe 13 through the return pipe 29 and the liquid pump 30. The advantage is that it can be used in winter. During the process, the hot production water from the main pumping station 6 is transported to the first auxiliary collection pipe 16 or the second auxiliary collection pipe 17 through the third connecting pipe 7, the first three-way valve 8, and the second three-way valve 15. When higher temperature production water is needed, it can be directly returned to the second connecting pipe 5 through the first auxiliary collection pipe 16. When lower temperature production water is needed, it can be returned to the second connecting pipe 5 through the second auxiliary collection pipe 17, the return collection tank 18, the third booster pump 19, and the sixth connecting pipe 20. Excess production water in the return collection tank 18 can be returned to the pumping station's water storage tank 2 through the return pipe 29 and the pump 30. This ensures that the production water in the pumping station's water storage tank 2 will not freeze, reducing the threat of extreme freezing weather to the water supply tank and pipelines, and improving the safety and stability of the water supply network.
[0032] Example 3:
[0033] like Figure 1-3 As shown, this is an improvement on the previous embodiment.
[0034] Specifically, the sedimentation tank 22 is connected to the main filter 24 via the auxiliary connecting pipe 1 23. The main filter 24 is connected to the constant pressure filter 27 via the auxiliary connecting pipe 25 and the fourth booster pump 26. The constant pressure filter 27 is connected to the first return water pipe 13 via the second return water pipe 28. The main sewage pipe 21, auxiliary connecting pipe 1 23, and auxiliary connecting pipe 25 are made of either PVC or UPVC pipes. Check valves are installed at the end of the fifth connecting pipe 11 away from the cooling tower 10 and at the end of the second return water pipe 28 away from the constant pressure filter 27. The advantage is that during use, the water output from the mechanical seal of the main pump, the impeller flushing water of the drainage pump station, and the bar cleaning water can be collected in the sedimentation tank 22 through the main sewage pipe 21 for sedimentation. The settled water is then transported to the first return water pipe 13 through the auxiliary connecting pipe 1 23, the main filter 24, the auxiliary connecting pipe 25, the fourth booster pump 26, the constant pressure filter 27, and the second return water pipe 28. This allows for the reuse of wastewater, reduces water consumption, and also reduces the cost of the drainage pump station.
[0035] Working principle: During operation, municipal water supply outlet 1 delivers municipal water to the pumping station's water storage tank 2. The first booster pump 3, through the first connecting pipe 4, delivers production water to the main pumping station 6 via the second connecting pipe 5, cooling the lubrication tank of the main pump bearing in the main pumping station 6. The used water is then delivered to the cooling tower 10 via the third connecting pipe 7, the first three-way valve 8, and the fourth connecting pipe 9. The cooling tower 10 cools the production water. The cooled production water then flows through the fifth connecting pipe 11 and the second booster pump 1... 2 and the first return water pipe 13 return the water to the pump station's water storage tank 2, thereby realizing the reuse of production water and reducing water consumption. During winter use, the hotter production water after use of the main pump station 6 is transported to the first auxiliary collection pipe 16 or the second auxiliary collection pipe 17 through the third connecting pipe 7, the first three-way valve 8, and the second three-way valve 15. When higher temperature production water is needed, it can be directly returned to the second connecting pipe 5 through the first auxiliary collection pipe 16. When lower temperature production water is needed, it can be returned to the second connecting pipe 5 through the second auxiliary collection pipe 16. The water flows back to the second connecting pipe 5 via the collection pipe 17, the return collection tank 18, the third booster pump 19, and the sixth connecting pipe 20. Excess production water in the return collection tank 18 can be returned to the pump station's water storage tank 2 via the return pipe 29 and the pumping pump 30. This ensures that the production water in the pump station's water storage tank 2 will not freeze, reducing the threat of extreme freezing weather to the water supply tank and pipelines, and improving the safety and stability of the water supply network. During use, the main pump's mechanical seal output water, the drainage pump station impeller flushing water, and the bar screen cleaning water... Wash water can be collected through the main sewage pipe 21 and sent to the sedimentation tank 22 for sedimentation. The settled water is then transported to the first return water pipe 13 through the secondary connecting pipe 23, the main filter 24, the secondary connecting pipe 25, the fourth booster pump 26, the constant pressure filter 27, and the second return water pipe 28. This allows for the reuse of wastewater, reduces water consumption, and lowers the cost of the drainage pumping station. The overall design is reasonable, avoiding the threat of extreme weather to the water supply tank and pipes, and minimizing water waste. It is suitable for widespread use.
[0036] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A circulating water system of a drainage pumping station, comprising a municipal pipe network water inlet (1) and a pumping station reservoir (2), characterized in that: The municipal pipe network water inlet (1) and the pump station reservoir (2) are communicated by pipeline, the first end of the pump station reservoir (2) away from the municipal pipe network water inlet (1) is provided with a first booster pump (3) and a first connecting pipe (4), the first end of the first connecting pipe (4) away from the pump station reservoir (2) is provided with a second connecting pipe (5), the first end of the second connecting pipe (5) away from the first connecting pipe (4) is provided with a total pump station (6), the outer side of the total pump station (6) is provided with a third connecting pipe (7), a first three-way valve (8) and a main sewage pipe (21), the outer side of the first three-way valve (8) is provided with a fourth connecting pipe (9) and a main collecting pipe (14), the first end of the fourth connecting pipe (9) away from the first three-way valve (8) is provided with a cooling tower (10), the first end of the cooling tower (10) away from the fourth connecting pipe (9) is provided with a fifth connecting pipe (11), a second booster pump (12) and a first backwater pipe (13), the first end of the main collecting pipe (14) away from the first three-way valve (8) is provided with a second three-way valve (15), a first auxiliary collecting pipe (16) and a second auxiliary collecting pipe (17), the first end of the second auxiliary collecting pipe (17) away from the main collecting pipe (14) is provided with a recycling collecting tank (18), the first end of the recycling collecting tank (18) away from the second auxiliary collecting pipe (17) is provided with a third booster pump (19), a sixth connecting pipe (20), a backflow pipe (29) and a liquid pumping pump (30), the first end of the main sewage pipe (21) away from the total pump station (6) is sequentially provided with a sedimentation tank (22), a first auxiliary connecting pipe (23), a main filter (24), a second auxiliary connecting pipe (25), a fourth booster pump (26) and a constant pressure filter (27), the first end of the constant pressure filter (27) away from the main sewage pipe (21) is provided with a second backwater pipe (28).
2. A recirculating water system for a drainage pumping station according to claim 1, characterised in that: The first connecting pipe (4) and the second connecting pipe (5) are communicated, the outer side of the first connecting pipe (4) is provided with a check valve, the third connecting pipe (7), the fourth connecting pipe (9) and the main collecting pipe (14) are connected at the three ends of the first three-way valve (8) respectively, the two ends of the first backwater pipe (13) are communicated with the pump station reservoir (2) and the fifth connecting pipe (11) respectively, the second connecting pipe (5), the third connecting pipe (7), the fourth connecting pipe (9), the main collecting pipe (14), the first auxiliary collecting pipe (16), the second auxiliary collecting pipe (17) and the sixth connecting pipe (20) adopt one of PPR pipe or cast iron composite pipe containing anticorrosive lining, and the second connecting pipe (5), the third connecting pipe (7), the fourth connecting pipe (9), the main collecting pipe (14), the first auxiliary collecting pipe (16), the second auxiliary collecting pipe (17) and the sixth connecting pipe (20) are full-closed pressure-bearing pipes.
3. A recirculating water system for a drainage pump station according to claim 1, characterized in that: The main collecting pipe (14), the first auxiliary collecting pipe (16) and the second auxiliary collecting pipe (17) are communicated with the second three-way valve (15) respectively, the first end of the first auxiliary collecting pipe (16) away from the second three-way valve (15) is communicated with the second connecting pipe (5), and the sixth connecting pipe (20) is communicated with the connecting pipe (5).
4. A recirculating water system for a drainage pump station according to claim 1, characterized in that: The sixth connecting pipe (20) and the first sub collecting pipe (16) are provided with check valves at one end close to the connecting pipe (5), the second sub collecting pipe (17) and the sixth connecting pipe (20) are communicated with the recovery collecting pool (18).
5. A recirculating water system for a drainage pump station according to claim 1, characterized in that: The recovery collecting pool (18) is located at the lower layer of the total pump station (6), the water storage capacity of the recovery collecting pool (18) is not less than the cooling water output of two main pumps per unit time, the number of the third booster pump (19) is not less than two, and the recovery collecting pool (18) is also communicated with the first backwater pipe (13) through the backflow pipe (29) and the liquid pumping pump (30).
6. A recirculating water system for a drainage pump station according to claim 1, characterized in that: The sedimentation tank (22) is communicated with the main filter (24) through the sub connecting pipe one (23), the main filter (24) is communicated with the constant pressure filter (27) through the sub connecting pipe two (25) and the fourth booster pump (26), the constant pressure filter (27) is communicated with the first backwater pipe (13) through the second backwater pipe (28), and the main sewage pipe (21), the sub connecting pipe one (23) and the sub connecting pipe two (25) adopt one of PVC pipes and UPVC pipes.
7. A recirculating water system for a drainage pump station according to claim 1, characterized in that: The fifth connecting pipe (11) is provided with a check valve at one end away from the cooling tower (10), and the second backwater pipe (28) is provided with a check valve at one end away from the constant pressure filter (27).