The invention relates to a pig system for transporting liquid or pasty substances, in particular paints, comprising
Pig systems for transporting liquid or pasty substances are widespread in the art, in particular in coating technology, where they are primarily used in supply units for application devices. There they are used, inter alia, for the transport of paint between paint-carrying loop lines of the spray booth and the application device.
Pigs are subject to natural wear and tear, so that, after a certain operating time, they become uptight and leaks occur along them. They must then be replaced. This should be able to be done in as short a time as possible and, if need be, also automatically, in order that costly downtimes of the plant are as far as possible avoided. In the pig system which is described in DE 10 2004 037 247 B4 and corresponds to the type stated in the introduction, there is provided a pig changing station, which is disposed outside of a pig station and contains a multiplicity of positions in which pigs, new or defective, can be stored. This external pig changing station is connected to the pig station by a line or a hose. Normally, the pig channel in this pig station is closed off by a stopper, against which the single pig moving in the actual pig system abuts. For the exchange of this pig, this stopper is removed by an appropriate mechanism and the hose leading to the pig changing station is connected up to the pig channel, so that now the defective pig is moved out and can be conveyed into a position of the pig changing station. A new, functional pig is thereupon introduced in the reverse direction into the pig channel of the pig station and the pig channel is closed off again by the stopper. In this way, a great number of pigs can be introduced into the pig system, which ensures very high service lives. However, this mechanism is very complicated and the times which are required for the pig change are not wholly insignificant.
The object of the present invention is to provide a pig system of the type stated in the introduction, with which a worn or otherwise defective pig can be replaced in very short time, and with low equipment expenditure, by another pig.
This object is achieved according to the invention by virtue of the fact that
According to the invention, a stock of pigs is kept not outside, but within the actual pig system. By suitable controlling of the media connections, it is managed only to keep respectively only a part of the functional pigs, preferably only one pig, active, so that these or this can oscillate between the two pig stations in fulfilling their/its transport function, while the other pigs, whether these now are worn or still new, remain in parking positions of the one or other pig station. This “exchanging” of the respectively active pigs or of the active pig can happen in an extremely short time, since only the switching times of the appropriate valves here play a role. The design cost here remains within very narrow limits, so that the pig system according to the invention is also extremely cheap. However, the number of pigs which can in this way be used in a pig system prior to an opening of the pig system is naturally limited.
In an advantageous embodiment of the invention, the pigs have on an end face a projection, such that, between the end faces of adjacent pigs in a pig channel, there remains an interspace into which a hole assigned to a media connection opens out. In this way, it can be precisely defined which pig is moved at which moment and which pigs remain stationary in their parking positions.
An illustrative embodiment of the invention is explained in greater detail below on the basis of the drawing;
Reference is firstly made to
The shape of the pigs 5, 6, 7 is known per se: As the result of a waist narrowing, they acquire in both end regions a circumferential sealing lip; on an end face, in
The pig station 3 is provided with a plurality of media connections 10, 11, 12, 13, of which the media connections 10, 11, 12 situated furthest left in the drawing are respectively assigned to a parking position of the pigs 5, 6, 7. The media connections 10, 11, 12, 13 contain shut-off valves, which can release or shut off the inflow of pressurized media through an associated opening 14, 15, 16, 17 in the housing of the pig station 3 into the pig channel 8. The openings 14, 15, 16 here open out into an interspace between the parked pigs 5, 6, 7 kept at a distance apart by their projections 5a, 6a, 7a.
The media connections 10, 11, 12 are connected to a media supply source 18 and can be fed by this with pushing medium. Which of the media connections 10, 11, 12 respectively releases the pushing medium stream, and which not, is determined by a control system (not represented) which is known per se, according to a logic which is explained in greater detail below.
The fourth media connection 13, which likewise comprises a controllable valve, opens out with its associated hole 17 into the pig channel 8 at a place which lies between the pig 7 disposed furthest right in
A further look shall now be taken at the, in
The pig system 1 is operated in the following manner.
In the “new state” of the pig system 1, in which all pigs 5, 6, are undamaged and fully functional, the pig operation is performed solely of the pig 7, which in
As a result, the pig 7 is pushed out of the pig channel 8 and conveyed through the pig line 2 to the, in
The end of the movement of the pig 7 takes place once this has reached that parking position of the right-hand pig station 4 in which it has arrived with its right-hand end face against the stop 9′ within the pig channel 8′. By loading of the media connection 10′ situated furthest right in
This operation of the pig system 1 is continued until such time as wear phenomena or other defects are manifested on the “active” pig 7, in general by the fact that the sealing lips of the pig 7 no longer bear tightly against the inner wall of the pig line 2 and so leaks can arise along the pig 7. In this case, hitherto in the prior art, the pig system 1 is opened and the pig 7 exchanged. In the present case, on the other hand, the pig 7, as represented in
The transport of the medium through the pig line 2 is now taken over by the, in
If, after a further operating time, the, in
If the last pig 5, too, has reached the end of its life, it can still be moved for instance, as is shown in
In the above description, it was assumed that the respectively active pig 5, 6, 7 pushes ahead of it the substance to be transported. However, an operation in which the substance is used as a pushing medium, i.e. drives forward the pig 5, 6, 7 through the pressure of the media supply source 18, is also conceivable. The pig 5, 6, 7 here cleans the pig line 2 of another substance still present therein.
In many cases, it is also conceivable that not only an active pig 5, 6, 7 is used. For instance, applications in which the transport of the substance between two pigs 5, 6, 7 is realized in the manner of a “parcel” are known in the prior art. The functionalization and defunctionalization of pigs 5, 6, 7 or pairs of pigs is here realized in appropriate application of the principles set out above.
Number | Date | Country | Kind |
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10 2014 016 109.9 | Oct 2014 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2015/002017 | 10/13/2015 | WO | 00 |