EP0570739A1 - Drainage system - Google Patents

Abstract

The drainage system operated at subatmospheric pressure is composed of a subatmospheric-pressure source (12), of a collection line (14, 16) connected thereon and of a plurality of connection lines (22) which are connected to said collection line and can be respectively shut off by a scavenging valve (24). In order to stabilise the subatmospheric pressure available at the connection lines and thus to ensure the function of scavenging valves controlled in dependence on pressure, the invention provides that the collection line (14, 16), passing between the connection lines (22) and the subatmospheric-pressure source (12), is laid in an inclined manner and is dimensioned such that part of its inner cross-section remains free, even if it is subjected to peak loading. <IMAGE>

Description

The invention relates to a drainage system operated with negative pressure, consisting of a negative pressure source, at least one collecting line connected to it, laid in or above the floor, and a plurality of intermediate lines connected to it, which can be shut off by independently operable suction valves.

While in drainage systems with free fall lines, the wastewater is transported by gravity, the transport in vacuum drainage systems is based on the principle of plug delivery, whereby, as with pneumatic tube, a liquid plug closes the pipe cross-section and due to a pressure difference between the front and rear in the vacuum line is driven forward. If the plug is overtaken by the pushing air during transport by penetrating it through the slower flowing water, then a collecting line, e.g. B. each after about 20 meters, a sink or pocket may be formed in which the water remaining in the adjacent line section collects and again forms a stopper which closes the line cross section and which is transported at least to the next sink or pocket when opened by opening a Valve, in turn, a pressure difference is generated between the side of the plug facing the outer end of the manifold and the side facing the vacuum source.

Vacuum drainage systems can sometimes also contain free fall lines in which the system negative pressure prevails (cf. DE 29 08 745 C2 and DE 26 37 962 B2). However, there are always pockets and sinks between the vacuum source, ie the vacuum pump, and the house connections or other connections to be suctioned, in which the water fills the pipe cross-section.

The above-described functional principle of vacuum drainage systems has a prerequisite for trouble-free operation that each time a suction valve is opened, only a relatively small amount of water of a few liters is sucked in together with a multiple volume of air. The large amount of air in relation to the amount of water conveyed makes the operation of a vacuum drainage system seem uneconomical, but is a necessity for local drainage systems operated according to the plug promotion principle, whose suction valves on the individual house connections are actuated independently of each other depending on the amount of wastewater. A simultaneity factor is even taken into account, i. H. the situation that occurs again and again with statistical probability that several house connection lines leading to a collecting line are opened simultaneously or in quick succession, so that suddenly a particularly large amount of air occurs, which creates a very large pressure difference towards the vacuum source and is therefore able to handle large water plugs or relatively long water columns, which have formed on the pockets and sinks of the vacuum line, to accelerate sufficiently that they are transported at least to the next pocket or sink in the direction of the vacuum source before the air is bubbled through. In quiet times, e.g. B. at night when the simultaneity effect does not occur, ventilation valves provided in addition to the suction valves on the house connection lines may have to be opened in order to prevent the drainage system from becoming blocked by sluggish water columns that are too long.

The vacuum drainage systems for local drainage that have been built so far also work with relatively large pressure fluctuations in the pipe network, depending on their load or filling. This is due to the fact that the suction valve of a house connection only opens automatically if there is a certain minimum negative pressure in the manifold at the connection point, on the other hand that there are enough large receptacles at the individual house connections that can hold a multiple of the volume of water to be extracted during a suction process and are able to store it in the long term. If there is only a slight negative pressure in the line system temporarily or only a slight negative pressure overall, the house connections affected do not open temporarily until the situation has normalized, possibly with the ventilation valves mentioned.

The suction valves on the house connections of the known vacuum drainage systems are controlled so that they automatically open at a certain filling level of the collecting container at the house connection and in the presence of a sufficient negative pressure in the vacuum line and either after a certain period of time or after the collecting container has been emptied and additionally a certain one Close the opening time for the intake of air. It is irrelevant for the safe operation of the system whether a collection container is actually completely emptied during a suction process, because if this is not the case, a new suction process will be initiated a short time later if there is sufficient vacuum.

However, there are situations where, on the one hand, drainage by drainage is not possible in the free fall, but on the other hand, a vacuum drainage system that works on the principle of plug promotion does not always work reliably. Such hitherto incompletely developed areas of application can be found, for. B. where over the connecting lines each with a single suction larger collection containers must be completely emptied or where you depend on a strong negative pressure in any case when opening a suction valve, such as. B. when the connecting lines are or contain high risers, whereby it must be ensured that the amount of liquid to be sucked out during the opening of a suction valve overcomes the height of the riser instead of falling back therein.

The application mentioned that relatively large collection containers must be suctioned off exists, for. B. at maintenance stations where the wastewater tanks of the wagons of a train are disposed of. A valve control for the suction valves of such a drainage system is described in EP 0 341 595 B1. It works in such a way that, after triggering a suction process, the entire connected waste water container is sucked empty and the suction valve closes automatically if air flows in after the waste water container has been emptied and the absolute pressure at the suction valve increases as a result. Safety precautions could also be taken, e.g. B. acoustic or visual warning devices that ensure in any case that all waste water tanks of a train are completely emptied before it goes on the next trip. However, this would involve considerable additional effort. On the other hand, there is currently a risk that it will go unnoticed by the maintenance personnel; if a suction valve closes before a collection container has been completely emptied.

The premature closing of a suction valve of the type described in EP 0 341 595 B1 and other pressure-dependent controlled valves can be triggered by pressure fluctuations which, for the reasons described above, have hitherto been unavoidable in vacuum drainage systems. The object of the invention is therefore to create a drainage system of the type described at the beginning, in which the vacuum available at the connecting lines is stabilized with simple means is, so that the function of pressure-controlled suction valves and possibly the suction of wastewater under difficult conditions, such as. B. via high risers is guaranteed.

The above object is achieved in that the manifold between the connecting lines and the negative pressure source is continuously laid with a slope and is dimensioned so large that its inner cross section remains partially free even at peak loads.

With the special division resulting from the proposal, the new drainage system represents a combination of elements of a conventional freefall drainage system and a vacuum drainage system. As explained above, the collecting lines with slope sections are also laid in vacuum drainage systems for local drainage where the wastewater flows by gravity towards the vacuum source. However, what is essential for the invention is not the force with which the water is conveyed in the collecting line. Rather, the decisive factor is that there is a continuously open connection between the vacuum source and the individual suction valves, which is not interrupted by water columns of different lengths, so that the suction valves arranged near the outer end of the collecting line also have an empty space and are not interrupted by sluggish water plugs and water columns the vacuum of the vacuum source.

In contrast to known vacuum drainage systems, it remains in a system according to the invention even if the relatively large volume of z. B. five hundred to a thousand liters of wastewater is sucked from a railroad car within about two to three minutes, without affecting the operability of the further away suction valves arranged from the vacuum source. In the relatively small manifold of a vacuum drainage system for local drainage, the large wastewater volume let into the manifold in one go would form a long, sluggish water column behind which the negative pressure could collapse to zero due to the inflowing air, which would result in the function of all of them the long water column arranged connections would be affected. In contrast, according to the proposal of the invention, the manifold is only partially filled, preferably up to about half the height of its inner cross section, and the uninterrupted gradient also prevents the formation of plugs in the further course of the manifold, so that over its entire length, regardless of the current one Load, essentially the same negative pressure prevails.

The fact that the invention does not depend on the type of discharge of the waste water, but rather on the supply of the suction valves with stabilized negative pressure, is also evident from the fact that in applications where only the pneumatic control devices of the suction valves function properly is, as an alternative to the first-mentioned solution, it can be provided that the control devices of the suction valves are connected to the vacuum source via a control line which is separate from the collecting line. It can be seen from a comparison with the first solution that the free cavity above the water level in the collecting line takes over the function of the control line of the second solution. In the case of the latter, it does not matter whether the manifold functions as a free fall line or as a vacuum drainage line based on the principle of plug production.

While with a conventional vacuum line the pressure losses increase with length because at regular intervals There are pockets or sinks for the formation of plugs, and an excessively large pipe cross-section for the conveyance in the form of plugs has an adverse effect on a drainage system according to the invention with a collecting pipe, the upper cross-sectional area of which is continuously free of waste water, the opposite. The larger the free space in the manifold, the larger the vacuum reservoir available at all times, together with the cavity of the vacuum source. A vacuum reservoir with a large volume offers the advantage that when a suction valve is opened, only relatively small pressure fluctuations are caused by the inflowing water and the inflowing air. The collecting line therefore preferably has a length of several hundred meters and an inner diameter of at least approximately 125 mm.

Fig. 1

eine schematische Darstellung einer Vakuum-Entwässerungsanlage eines Wartungsbahnhofs zur Entsorgung der Abwasserbehälter von Eisenbahnwagen;

Fig. 2

einen Teillängsschnitt durch eine Sammelleitung der Entwässerungsanlage nach Fig. 1.

An embodiment of the invention is explained below with reference to the drawing. Show it:

Fig. 1

is a schematic representation of a vacuum drainage system of a maintenance station for the disposal of the wastewater containers of railroad cars;

Fig. 2

a partial longitudinal section through a manifold of the drainage system of FIG. 1st

The vacuum drainage system shown consists of a central collecting space 10 which is constantly kept at a negative pressure of about 5 to 7 m water column by means of a vacuum pump 12 and serves as a negative pressure source. Two collecting pipes 14 and 16 are connected to the collecting space 10 above the water level, with a gradient of at least one in the floor 4 to 6 per mille are laid towards the collecting room 10 and extend on opposite sides along the platform of a maintenance station. The manifolds 14 and 16 consist of pressure-tightly connected plastic pipes with an inner diameter of z. B. about 150 mm. Depending on the application, this can also be somewhat smaller at the outer end of a manifold, e.g. B. about 125 mm or gef. also only be 90 mm, and larger diameter values of z. B. 250 mm and more, the design in each section of a manifold in the example chosen so that the peak level resulting from the flow rate per unit of time and the line cross section arises only approximately to the center of the pipe at peak load, as in Fig. 2 is shown where the central longitudinal axis of the manifold 14 is designated 18 and the water level 20.

In the upper, free area of the collecting line 14, 16 open, distributed over their length, several connecting lines 22 each, which have a substantially smaller cross section than the collecting lines, so that even a large volume of wastewater sucked off via a connecting line 22 despite the slower flow velocity in the manifold 14 or 16 whose cross-section does not fill. The connecting lines 22 each contain a suction valve 24, as is described in detail in EP 0 341 595 B1 together with its control device. The suction valve 24 is opened after coupling the connecting line of the wastewater tank of a railroad car and automatically closed again by said pneumatic control device after the wastewater tank of the railroad car has been sucked empty and only air flows in. Since all the connecting lines 22 are connected to the vacuum source 10, 12 via the upper cavity of the collecting lines 14 and 16 which is free of waste water, it is ensured that during the entire Duration of a suction process via any connection line 22, the system vacuum does not break down at its connection point, as a result of which the suction valve 24 is closed too early.

As an alternative to connecting the pneumatic control devices of the suction valves 24 via the upper, free cavity of the collecting line 14 to the vacuum source 10, 12, a control line 26, which is laid next to the latter and is indicated by dashed lines in FIG is and extends with branches along the individual connecting lines 22 to the suction valves 24. If such a control line 26 is used, the collecting line 14 can also have a smaller cross section and be laid with sinks or pockets to form plugs which fill the entire line cross section and are conveyed to the collecting space 10 by pressure differences in the line.

Claims (9)

Drainage system operated with negative pressure, consisting of a negative pressure source, at least one collecting pipe connected to it, laid in or on the floor, and several connecting pipes connected to it at a distance, which can be shut off by suction valves which can be actuated independently of one another, characterized in that the collecting pipe (14, 16) between the connecting lines (22) and the vacuum source (10, 12) are laid continuously with a slope and are dimensioned so large that their internal cross-section remains partially free even at peak loads. Drainage system according to claim 1, characterized in that the length of the collecting line (14, 16) is at least about 100 m. Drainage system according to claim 2, characterized in that the length of the collecting line (14, 16) is more than 200 m, preferably more than 400 m. Drainage system according to one of claims 1 to 3, characterized in that the collecting line also has an internal diameter of at least approximately 125 mm between the second and third connecting lines (22), as seen from the outer end in the direction of flow. Drainage system according to one of claims 1 to 4, characterized in that the collecting line (14, 16) is laid with a gradient of at least 4 to 6 per mille. Drainage system according to one of claims 1 to 5, characterized in that the inner cross section is dimensioned such that it is filled to a maximum of about 75%, preferably about 50%, at peak loads. Drainage system according to one of claims 1 to 6, characterized in that the closing movement of the suction valves (24) is controlled as a function of the pressure in the connecting line (22). Drainage system according to one of claims 1 to 7, characterized in that the connecting line (22) has a riser of more than 10 m in height. Drainage system operated with negative pressure, consisting of a negative pressure source, at least one collecting line connected to it, laid in or above the floor, and several connecting lines connected to it at intervals, which can be shut off by suction valves which can be actuated independently of one another, characterized in that the suction valves (24) are pneumatic Control devices can be actuated which are connected to the vacuum source (10, 12) via a control line (26) which is separate from the collecting line (14, 16).

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