EP0448944B1 - Method and device for intervalwise spraying of a suspension of lubricant - Google Patents

Abstract

A lubricant suspension is sprayed intermittently under high pressure by spray nozzle (4). Spray nozzle (4) operates like an excess pressure valve, by it opening automatically with the input pressure of the suspension exceeding a threshold value pressure and closing automatically in the case of the input pressure falling short of the threshold value pressure. The suspension is conveyed, without the interposition of a shutoff device, directly by pneumatically driven pump (2) to spray nozzle (4). The pump output pressure is maintained at a pause pressure in the pauses between the spraying intervals, is increased to the spraying pressure to spray the liquid, and is again lowered to the pause pressure at the end of the spraying interval. The pause pressure in this case is calculated so that it is just insufficient in value to open spray nozzle (4). The shutoff element subject to abrasion, previously necessary, between the pump and the spray nozzle becomes unnecessary by the pump pressure control according to the invention. The operating safety is significantly increased and the spraying starts immediately without delay when the pump pressure is increased.

Description

The invention relates to a method for intermittent spraying of a lubricant suspension to be sprayed under high pressure, according to the preamble of claim 1, and to a device for carrying out the method according to the preamble of claim 4.

Processes and devices of this type are used in particular for the lubrication of mandrel bars in pipe production. As described, for example, in EP-B 0 192 037, a lubricant suspension, in particular an essentially graphite, and polymers and auxiliaries, such as stabilizers, are suspended in high-temperature lubricant suspensions containing water (cf. CH-A 596 294 and 609 728 ) used, which the spray nozzle under very high pressure of e.g. 50 - 120 bar (in special cases even higher up to 250 bar) and with flow velocities of 20 to 120 m / sec. As the spray nozzle, as stated in EP-B 0 192 037, a spray nozzle which automatically opens in the manner of a pressure relief valve when the inlet pressure of the liquid exceeds a threshold value pressure and closes automatically when the pressure falls below the threshold value, such as, for. B. in EP-A 0 039 839 (Fig. 2).

For intermittent spraying of the liquid, a shut-off device arranged in front of the spray nozzle has been alternately opened and closed. At high pressures and flow velocities, the abrasion is critical, which also and especially occurs with the lubricants in question because of the high speed of the suspended particles (especially the graphite particles). As explained in detail in EP-B 0 192 037, the shut-off devices have therefore been improved in such a way that, on the one hand, they are functional over a long period despite the high abrasion and, on the other hand, leaks are detected in good time so that the entire system does not suffer a sudden failure of the shut-off device must be shut down.

The object of the invention is to increase the operational reliability of the methods and devices of the type mentioned at the outset.

The solution according to the invention of this task specified in patent claims 1 and 4 follows a path which differs fundamentally from the known. Instead of a further improvement of the shut-off device according to the invention, this is completely dispensed with and the suspension is conveyed directly from a pump to the spray nozzle, that is to say it is kept in constant, direct fluid communication with the pump, and its outlet pressure is kept at a pause pressure in the pauses between the spray intervals, for Spraying the suspension to the spray pressure is increased and at the end of the spray interval it is reduced again to the pause pressure, the pause pressure being dimensioned such that it is just not sufficient to open the spray nozzle.

The pause pressure is thus a safety tolerance below the threshold pressure ("closing pressure") of the automatically closing spray nozzle, so that it remains constantly operational and opens immediately when the pump pressure is increased.

From GB-A-2 109 271 a device for cleaning clogged drainage pipes with deposits is known. In this non-generic device, a jet head provided at the end of a hose is driven forward in the line by means of pulsating water jets directed backwards. By supplying the valve-free jet head intermittently with water, it moves jerkily and can clean pipes up to 600 m in length. In order to generate the pulsating water jet, a powerful pump is equipped with a hydraulic control circuit. This control circuit comprises a pressure accumulator and a valve which can be actuated by it. The valve opens and closes a bypass to the pump. The hydraulic control or oscillation circuit works like this: When the valve is closed, pressure slowly builds up in the pressure accumulator on the outlet side of the pump. If this is so large that it is able to overcome the spring force of the valve, the valve in the bypass is opened, the outlet pressure of the pump breaks down and the pump conveys a course. As a result, the nozzle drive jet breaks off. This depressurized state remains until the pressure in the pressure accumulator is reduced and the valve closes the bypass again due to the spring force. Immediately, a high pressure builds up in the hose line, which leads to a sudden water jet and thus a recoil, which causes the jet head to move forward suddenly.

To quickly lower the spray pressure to the pause pressure, a branch line leading away from the pump outlet line is preferably opened at the end of the spray interval, through which the liquid is either either returned to the pump inlet line or emptied into a drain line leading to a sewer or filter cake reservoir.

The pump is expediently driven pneumatically and supplied with two pneumatic lines, the first of which supplies the air pressure measured to generate the pause pressure and the second supplies the air pressure measured to generate the spray pressure, both pneumatic lines preferably being fed in parallel from the same compressed air source, and one in the first pneumatic line Pressure for generating the pause pressure limiting first pressure regulator is arranged, and the second pneumatic line has a shut-off device with which the compressed air supply is shut off from the compressed air source during the pauses. A second pressure regulator is expediently provided in the second pneumatic line so that the spray pressure can be varied. (Without a second pressure regulator, the compressed air source determines the spray pressure).

Further preferred embodiments of the method and the device result from the dependent claims and the following description of an embodiment of the invention.

The (only) figure shows a block diagram of a device for intermittent spraying of a lubricant suspension.

The lubricant suspension is drawn in by a pump 2 through a suction line 1. The pump 2 is in constant, direct fluid communication with a spray nozzle 4 through the pump pressure line 3 without the interposition of a shut-off device.

The spray nozzle 4 is designed in the manner of the nozzle shown in Figure 2 of EP-A 0 039 839 (Fig. 2) in such a way that it opens automatically like a pressure relief valve when the inlet pressure of the liquid exceeds a threshold value pressure and against the force of a spring the spring closes automatically when the pressure falls below the threshold value.

The pump 2 is a pneumatically driven (air-powered) 20: 1 piston pump (eg "King Pump" from Graco Inc.), the output pressure ("working pressure", pump pressure or delivery pressure of the liquid) is almost 20 times the pressure of the compressed air with which the pump 2 is acted upon.

The pump outlet pressure is increased for the intermittent spraying of the lubricant suspension by means of a pressure control device described in the following from a pause pressure that is just not sufficient to open the spray nozzle 4 to a spray pressure and then lowered again.

For this purpose, the pump 2 is connected to two pneumatic lines 5, 6, the first of which supplies the air pressure measured to generate the pause pressure and the second supplies the air pressure measured to generate the spray pressure. Both pneumatic lines 5, 6 are connected on the input side together (in parallel) via a water separator 7 to the compressed air network 8 of the plant, which supplies compressed air at a pressure of 5 bar, for example. On the output side, both pneumatic lines 5, 6 are connected to a feed line 9 of the pump 2, to which a safety valve 10 limiting the pressure to 5 bar is connected.

A first pressure regulator (pressure regulating or pressure reducing valve) 11 is arranged in the first pneumatic line 5 and reduces the primary pressure (5 bar) prevailing in the plant network to a secondary pressure of 1.5 bar. In the second pneumatic line 6 there is an electrical control device 12 serving as a shut-off device on the input side Controlled solenoid valve 13 and then a second pressure regulator (pressure control or pressure reducing valve) 14 is arranged, which reduces the primary pressure prevailing in the plant network 8 to a secondary pressure of 2.5 bar.

At a secondary pressure of 1.5 bar the pump outlet pressure (working pressure) is 30 bar (break pressure), at a secondary pressure of 2.5 bar the pump outlet pressure is 50 bar (spray pressure). The spray nozzle 4 opens at an inlet pressure which is greater than the pause pressure of 30 bar by a tolerance.

The pump outlet line 3 (pressure line of the pump 2) is guided to the spray nozzle 4 via a pressure shock absorber (pulsation damper, air tank) 15 and a filtering device 16. The filter device 16 serves to separate coarse particles from the suspension. It has a vestibule 18 lying in the flow direction in front of the filter body (filter basket, sieve) 17 and a scraper driven by a motor 19, which, in the manner of the scraper customary in pressure filters (cf., for example, DE-PS 28 23 092), each filter cake wipes off the filter body so that it does not become blocked. The section of the pump outlet line 3 coming from the pump 2 (via the pressure shock absorber 15) and opening into the antechamber 18 in front of the filter body 17 is designated 3a, the line section leading the filtrate from the filter body 17 to the spray nozzle 4 is designated 3b.

A branch line 20 leads away from the antechamber 18, which branches into a first branch 21 leading back to the pump inlet line 1 and a second branch 22, which opens out via an outflow funnel 23 into a sewer channel 24, into which the outflow of the water separator 7 also opens. Arranged in each of the two branches 21, 22 is a solenoid valve 25, 26 controlled by the electrical control device 12, one of which is opened at the end of the spray interval in order to quickly lower the spray pressure to the pause pressure. The inlet and the outlet of the antechamber 18 of the filtering device 16, to which the pump outlet line section 3a and the branch line 20 are connected, are on opposite sides of the antechamber 18 Arranged such that when the solenoid valve 25 or 26 is opened, the antechamber 18 is flooded and the filter cake located in front of the filter body 17 and the filter cake parts (coarse particles) stripped by the scraper are at least partially washed away into the branch line 20.

The control device 12 has switches (not shown) and control inputs with which the device can be controlled either manually or automatically by control commands from the pipe manufacturing system. The electrical control device is a device customary in the prior art and is therefore not described in detail. Their mode of operation also results from the following description of the method carried out with the device shown, it being assumed that the tube production system in each case delivers a start pulse and a stop pulse for the beginning and the end of the spray interval:

In the ready state of the device, the valves 13, 25, 26 are closed. The pump 2 is pressurized with the secondary pressure of the pressure regulator 11 (fed by the compressed air network 8), so that the pump outlet pressure is 30 bar (pause pressure) and the spray nozzle 4 charged with this pressure remains closed.

If the control device 12 receives a start pulse, it issues an opening command to the valve 13, so that the secondary pressure of the pressure regulator 14 is applied to the pump 2, its outlet pressure rises to the spray pressure (50 bar) and the spray nozzle 4 immediately when the pressure rises opens, whereupon the lubricant is sprayed.

If the control device 12 receives a stop pulse, it issues a closing command to the valve 13 and an opening command to the valve 25. The pump outlet pressure consequently drops immediately to the pause pressure, whereupon the spray nozzle 4 closes automatically. After the expiry of the time required for the spray pressure to drop from the pause pressure (the control device 12 has a corresponding time element, in each case acted upon by the stop pulse), the control device outputs 12 a closing command to the valve 25. The standby state now prevails again.

If the suspension has a low coarse particle content, the valve 25 is opened, as described above, so that no suspension is lost and the few coarse particles washed away are again conveyed into the antechamber 18 by the pump. In this case, the valve 26 is only opened rarely, namely only when a high coarse particle concentration (a coarse particle sump) has formed in the antechamber. (This rare opening of the valve 26 can take place automatically after a certain number of openings of the valve 25 or can be triggered by pressing a key).

When the coarse particle content of the suspension is high, the valve 26 is opened correspondingly more often so that the coarse particles are led away into the sewer, with the aim of not opening the valve 26 too often, of course, since not only the undesired coarse particles but also (valuable) lubricant are also removed becomes.

The described method and the setup have the following advantages:
Since the pump pressure line 3 is held by the pump 2 at the pause pressure, which is only a safety tolerance below the threshold pressure ("closing pressure") of the automatically closing spray nozzle 4, an immediate spraying is ensured when the pump pressure is increased: the pressure does not have to be first build on the threshold pressure.

The simple, small solenoid valve 13, which only has to shut off the compressed air and is therefore not subject to abrasion, is sufficient for switching the spraying process. In contrast, the prior art previously required an expensive multi-way valve for shutting off the liquid, due to the high liquid pressure and the high flow rate the liquid was subjected to high abrasion and therefore had to be replaced frequently and impaired operational safety.

The branch line 20 with the valves 25, 26 enables immediate pressure relief of the pump pressure line 3 and thus an immediate interruption of the spraying of the liquid, which not only avoids unnecessary lubricant discharge but also reduces the risk of accidents: an unwanted spraying of the lubricant after the end of the relevant one Operation is dangerous because the worker may U. in the (because of the high spray pressure) dangerous spray area. In addition, rinsing and thus cleaning of the filtering device 16 is achieved at the same time.

Some variants of the described device and the method are explained below:
The valve 26 can also be a manually operated shut-off device so that the filter cake or the coarse particle concentrate can be carefully drained by hand, the outflow funnel 23 also opening into a collecting container (a reservoir) instead of the waste water channel 24 so that the filter cake can be recycled can be.

The valve 25 (likewise the valve 26) can also be a valve operated by compressed air, the control input of which is connected to the compressed air network 8 via a multi-way valve controlled by the control device 12, with which very short switching times can be achieved.

In the pump pressure line 3, a flow meter connected to the control device 12 can be provided, which measures the flow of the suspension, the control device having a monitoring circuit that indicates during the spraying (during the opening time of the valve 13) a deviation of the measured flow from a desired flow and / or in the event of a tolerance exceeding Deviates a warning signal. For the same purpose, a proximity switch connected to the control device 12 can be provided on the pump 2, which reports the pump strokes to the device 12, the monitoring circuit of which checks whether the pump strokes reported per unit of time fall below a limit value and, if so, the incorrect functioning of the pump 2 gives warning signal.

Manometers for checking the line pressure can be provided in lines 3, 5, 6.

In particular, a pressure gauge is advantageously arranged in the line 3, which is connected to the control device 12 and this reports a pressure drop below the pause pressure (if the valve 25 or 26 remains open too long), the control device 12 immediately opening the valve when the pressure falls below the pause pressure 25 or 26 closes if the user does not prevent this automatic closing of the valve 25 or 26 by actuating a special valve opening button (not shown) for the valve 25 or 26. (The valve opening button is pressed for a thorough cleaning of the filter device).

A check valve (or a check valve) can be arranged downstream of the pressure regulator 11 so that the compressed air from the pressure regulator 14 (when the valve 13 is open) cannot act on the pressure regulator 11.

The two pressure regulators 11, 14 can also regulate to higher secondary pressures, the first, for example, to 2.0 bar, the second to 3 bar, so that the pause pressure is 40 bar and the spray pressure is 60 bar, the spray nozzle 4, of course, only after that higher inlet pressure (in order to open a tolerance less than 40 bar). For the dimensioning of the threshold pressure of the spray nozzle 4, a possible pressure drop in the line 3 must also be taken into account, which in the exemplary embodiment described above was found to be negligible, but would have to be taken into account in the case of a long line with a narrow cross section.

The motor 19 expediently remains in operation; it can also be switched off by the control device during longer breaks and can only be put into operation again with the next start command.

Depending on the liquid (or suspension) used, the filtering device 16 can also be designed without a scraper (and motor 19). In this case, it is particularly advantageous to arrange the inlet and the outlet of the antechamber 18 of the filter device 16, to which the pump outlet line section and the branch line 20 are connected, on opposite sides of the antechamber 18 immediately adjacent to the filter body 17, such that when opening of the valve 25 or 26 the liquid flowing through the antechamber 18 passes directly along the filter body 17 and washes away the filter cake located thereon. (This arrangement is of course also advantageous in the filter device 16 with scraper described above).

In the case of liquids which do not require any filtration, the filtering device 16 can of course be omitted. Of course, branch 22 is also omitted (in the case of valuable liquids) and only branch line 20 remains, which in this case leads from pump pressure line 3 directly via valve 25 into suction line 1. Should only be a "cheap liquid", e.g. B. water, are sprayed, the branch 21 can be omitted and the branch line 20 from the pump pressure line 3 directly through the valve 26 into the sewer 24.

Claims (10)

1. Process for interval spraying of a lubricant suspension to be sprayed under high pressure, by means of a spray nozzle (4) which, like a positive pressure valve, automatically opens when the input pressure of the suspension exceeds a threshold pressure, and automatically shuts when the threshold pressure is below a threshold value, characterised in that the suspension is delivered without a shut-off means thereinbetween directly from a pump (2) to the spray nozzle (4), and the pump output pressure is maintained in pauses between the spray intervals at a pause pressure, and is increased to a spray pressure for spraying the suspension, and is at the end of a spray interval again reduced to the pause pressure, and that the pause pressure is such that it is not quite able to open the spray nozzle (4).
2. Process according to claim 1, characterised in that the pump (2) is pneumatically driven and that the required air pressure for producing the pause pressure and for producing the spray pressure is selectively applied to the pump (2).
3. Process according to claim 1 or 2, characterised in that at the end of a spray interval a branch pipe (20), which is normally shut and which connects from the pump output pipe (3) to the pump input pipe (1) and/or to an outlet pipe (22), is opened in order to rapidly lower the spray pressure to the pause pressure.
4. Apparatus for carrying out the process according to claim 1, comprising a spray nozzle (4) which, like a positive pressure valve, automatically opens when the inlet pressure of the suspension is in excess of a threshold pressure, and automatically shuts when the threshold pressure is below a threshold value, characterised by a pump (2), which is in a permanent liquid connection without a shut-off means thereinbetween to a spray nozzle (4), and a pressure-control device (11-14), by means of which the pump output pressure can be increased from a pause pressure which is not quite sufficient for opening the spray nozzle (4) to a spray pressure, and reduced therefrom.
5. Apparatus according to claim 4 for carrying out the process according to claim 2, characterised in that the pump (2) is pneumatically driven and connected to two pneumatic pipes (5, 6), the first of which delivers a pneumatic pressure as required for producing the pause pressure, and the second of which delivers a pneumatic pressure as required for producing the spray pressure.
6. Apparatus according to claim 5, characterised in that both pneumatic pipes (5, 6) are fed in parallel by the same compressed-air source (8), and in the first pneumatic pipe (5) is fitted a first pressure controller (11) which restricts the pressure for producing the pause pressure, and the second pneumatic pipe (6) is provided with a shut-off element (13) for shutting off the compressed-air supply from the compressed-air source (8).
7. Apparatus according to claim 6, characterised in that the second pneumatic pipe (6) comprises a second pressure controller (14) which restricts the pressure to the level required for producing the spray pressure.
8. Apparatus according to one of claims 4 to 7 for carrying out the process according to claim 3, characterised by a branch pipe (20), which connects from the pump output pipe (3) to the pump input pipe (1) and/or to a release pipe (22) and in which is arranged a shut-off element (25, 26), which is controlled by the pressure-control device (11-14) and which is opened at the end of a spray interval to allow a rapid drop of the spray pressure to pause pressure.
9. Apparatus according to claim 8, characterised in that the pumZ output pipe (3) is connected via a filtering device (16) to the spray nozzle (4), the filtering device (16) comprises an ante-chamber (18) in front of the filtering element (17) as seen in the flow direction, and the branch pipe (20) extends from this ante-chamber (18) in such a manner that, on opening the shut-off valve (25, 26) of the branch pipe (20), the ante-chamber (18) is flowed through, and therein contained filter-press-cake elements or coarse particles are at least partially washed into the branch pipe (20).
10. Apparatus according to claim 9, characterised in that the branch pipe (20) comprises two branch sections (21, 22), which are each fitted with a shut-off element (25, 26) and the one of which connects to the pump input pipe (1) and the other one connects to an outlet pipe (22).

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