Oil pressure interlocking shutdown device for screw compressor

Abstract

The utility model provides an oil pressure interlocking shutdown device for a screw compressor. The oil pressure interlocking shutdown device comprises a PLC (Programmable Logic Controller) and a PLC starting relay connected with the PLC, the device further comprises an oil pressure relay, a time relay and an oil pressure interlocking control relay, the oil pressure relay is connected with the first voltage and the oil pressure interlocking control relay, and the oil pressure relay is powered on or powered off under the influence of oil pressure; a contact switch linked with the PLC starting relay is connected with a time relay and is connected with a second voltage; the contact switch linked with the oil pressure interlocking control relay and the contact switch linked with the time relay are connected in series and are connected with a stop signal; and the contact switch linked with the oil pressure interlocking control relay is also connected with a PLC (Programmable Logic Controller). According to the oil pressure interlocking shutdown device for the screw compressor, timely interlocking shutdown of the screw compressor can be achieved when the oil pressure is low, the possibility that the screw compressor is damaged due to too low oil pressure is reduced, and the service life of the screw compressor is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of screw compressors, in particular to an oil pressure interlock shutdown device for a screw compressor. Background Art

[0002] Screw compressors are often used in the field of air compression production. For example, screw compressors are often used in the ironmaking air compressor station. At present, the screw compressors used in our company's ironmaking air compressor station use protection interlocks including temperature interlock shutdown of the machine head and air pressure interlock shutdown at the outlet position. Temperature interlock shutdown means that the screw compressor shuts down when the temperature of the machine head is high to a certain extent. Air pressure interlock shutdown means that the screw compressor shuts down when the air pressure at the outlet position is high to a certain extent. The interlock shutdown mechanism of the used screw compressor only includes temperature interlock shutdown and air pressure interlock shutdown, and only an oil pressure alarm prompt is given for the oil pressure of the screw compressor, and no shutdown signal is given. Therefore, no interlock shutdown mechanism is set for the oil pressure.

[0003] When the oil pressure is low due to lack of lubricating oil, since only temperature interlock shutdown is set (temporarily not considering air pressure interlock shutdown), the screw compressor can only shut down when the temperature of the screw compressor head is high. During the heating process, the screw compressor head will be severely worn, and only shutdown and maintenance can be carried out.

[0004] The utility model attempts to provide an oil pressure interlock shutdown device for a screw compressor, which can realize the interlock shutdown of the screw compressor when the oil pressure is low. Summary of the Utility Model

[0005] The utility model provides an oil pressure interlock shutdown device for a screw compressor, which can realize the interlock shutdown of the screw compressor when the oil pressure is low.

[0006] The present utility model provides an oil pressure interlock shutdown device for a screw compressor, which includes a PLC controller and a PLC start relay connected to the PLC controller. The PLC start relay is energized when the PLC controller starts. The oil pressure interlock shutdown device for the screw compressor further includes an oil pressure relay, a time relay, and an oil pressure interlock control relay. The oil pressure relay is connected to a first voltage and is connected to the oil pressure interlock control relay. The oil pressure relay is connected to an oil pressure sensor, and the oil pressure relay is energized or de-energized under the influence of the oil pressure. A contact switch linked to the PLC start relay is connected to the time relay and is connected to a second voltage. When the PLC start relay is energized, the contact switch linked to the PLC start relay closes. A contact switch linked to the oil pressure interlock control relay and a contact switch linked to the time relay are connected in series and are connected to a stop signal. The contact switch linked to the oil pressure interlock control relay is also connected to the PLC controller. When the oil pressure interlock control relay is energized, the contact switch linked to the oil pressure interlock control relay closes. When the time relay is energized, after a certain delay, the contact switch linked to the time relay closes.

[0007] The oil pressure interlock shutdown device for the screw compressor provided by the present utility model can achieve timely interlock shutdown of the screw compressor when the oil pressure is low, reduce the possible damage to the screw compressor due to too low oil pressure, and extend the service life of the screw compressor. Description of the Drawings

[0008] Figure 1 The following shows a schematic structural diagram of the oil pressure interlock shutdown device for the screw compressor according to an embodiment of the present utility model.

[0009] Figure 1 Figure (a) shows a schematic circuit connection diagram of the oil pressure relay.

[0010] Figure 1 Figure (b) shows a schematic circuit connection diagram of the time relay.

[0011] Figure 1 Figure (c) shows a schematic circuit connection diagram of the PLC controller.

[0012] Reference Signs:

[0013] 1: PLC start relay; 1': Contact switch linked to the PLC start relay;

[0014] 2: Oil pressure interlock control relay; 2': Contact switch linked to the oil pressure interlock control relay;

[0015] 3: Time relay; 3': Contact switch linked to the time relay;

[0016] 4: Oil pressure relay; 5: PLC controller. Detailed implementation mode

[0017] To further understand the purpose, structure, characteristics and functions of the present utility model, the following is a detailed description in conjunction with embodiments.

[0018] Figure 1 The figure shows a structural schematic diagram of an oil pressure interlock shutdown device for a screw compressor according to an embodiment of the present utility model. As Figure 1 shown, the embodiment of the present utility model provides an oil pressure interlock shutdown device for a screw compressor, including a PLC controller 5 and a PLC start relay 1 connected to the PLC controller 5. The PLC start relay 1 will be energized when the PLC controller 5 starts. The PLC controller 5 and the PLC start relay 1 are originally provided in the system, and the inventor has made improvements on this basis; the oil pressure interlock shutdown device for the screw compressor further includes an oil pressure relay 4, a time relay 3 and an oil pressure interlock control relay 2. The oil pressure relay 4 is connected to a first voltage (such as 24V) and is connected to the oil pressure interlock control relay 2. The oil pressure relay 4 is connected to an oil pressure sensor. The oil pressure relay 4 is energized or de-energized under the influence of oil pressure. For example, when the lubricating oil pressure drops to a certain level (such as lower than 5 bar), the oil pressure relay 4 is energized. When the oil pressure relay 4 is energized and connected, the oil pressure interlock control relay 2 is also energized, as Figure 1 shown in part (a) therein; a contact switch 1' linked to the PLC start relay 1 is connected to the time relay 3 and is connected to a second voltage (such as the working voltage 220V). When the PLC start relay 1 is energized (such as when the PLC controller 5 starts when the screw compressor starts), the contact switch 1' linked to the PLC start relay 1 closes, as Figure 1 shown in part (b) therein; a contact switch 2' linked to the oil pressure interlock control relay 2 and a contact switch 3' linked to the time relay 3 are connected in series and are connected to a stop signal. The contact switch 2' linked to the oil pressure interlock control relay 2 is also connected to the PLC controller 5, as Figure 1 shown in part (c) therein; where when the oil pressure interlock control relay 2 is energized, the contact switch 2' linked to the oil pressure interlock control relay 2 closes; when the time relay 3 is energized, after a certain delay (such as 20 s), the contact switch 3' linked to the time relay 3 closes.

[0019] The oil pressure relay 4 is connected to the oil pressure sensor. For example, it can be set that when the oil pressure is lower than 5 bar, the oil pressure relay 4 is energized and connected, so as to connect the first voltage of 24V. When the oil pressure is equal to or greater than 5 bar, the oil pressure relay 4 is not connected and there is no voltage output. Before starting, the oil pressure is 0, lower than 5 bar, so the oil pressure relay 4 is energized and connected, thus connecting the first voltage of 24V, making the oil pressure interlock control relay 2 energized, and making the normally open contact switch 2' linked to the oil pressure interlock control relay 2 closed. At this time, the time relay 3 has not been energized and the normally open contact switch 3' is in the open state. Refer to Figure 1 In part (c), the contact switch 3' is in the open state, so the PLC controller 5 is not connected to the stop signal, and at this time the air compressor can be started normally.

[0020] After the air compressor starts, the PLC start relay 1 is also energized and starts, making the PLC controller 5 also start. After 5 - 10s, the air compressor runs normally. At this time, the oil pressure is 8 - 13 bar, greater than 5 bar, the oil pressure relay 4 is not energized, and the oil pressure interlock control relay 2 is not energized either. The contact switch 2' linked to the oil pressure interlock control relay 2 is disconnected. Refer to Figure 1 In part (b), at this time, since the PLC start relay 1 is energized, the contact switch 1' linked to the PLC start relay 1 is closed, so that the second voltage of 220V is output to the time relay 3, making the time relay 3 energized. After a certain time (for example, set the delay to 20s to avoid the start-up time and make the air compressor have enough time to start), the normally open contact switch 3' is closed.

[0021] When the air compressor is running, once the oil pressure is lower than a certain value (for example, 5 bar), the oil pressure relay 4 is connected, making the oil pressure interlock control relay 2 energized, thus making the normally open contact switch 2' closed, making the stop signal connected to the PLC controller 5, applying the stop signal to the PLC controller 5, and the air compressor stops running, achieving the purpose of oil pressure interlock shutdown. After the air compressor stops running, the PLC controller 5 also stops running, the PLC start relay 1 loses power, and at this time the contact switch 1' linked to the PLC start relay 1 is disconnected, making the time relay 3 lose power, thus making the normally open contact switch 3' disconnected, and not affecting the next start of the air compressor.

[0022] In the above embodiments, it is set that after the time relay 3 is energized for a certain time (for example, set the delay to 20s), the normally open contact switch 3' is closed because if the oil pressure has not reached 5 bar at this time, the normally open contact switch 2' will also be closed, resulting in the stop signal being connected to the PLC controller and the normal start of the air compressor cannot be achieved.

[0023] The oil pressure interlock shutdown device for a screw compressor provided by the present utility model can achieve timely interlock shutdown of the screw compressor when the oil pressure is low, reduce the possible damage to the screw compressor due to too low oil pressure, and extend the service life of the screw compressor.

[0024] In the description of the present utility model, it should be understood that the terms "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" orientation or positional relationship are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0025] The present utility model has been described by the above related embodiments. However, the above embodiments are only examples for implementing the present utility model. It must be pointed out that the disclosed embodiments do not limit the scope of the present utility model. On the contrary, modifications and refinements made without departing from the spirit and scope of the present utility model fall within the scope of the patent protection of the present utility model.

Claims

1. An oil pressure interlock shutdown device for a screw compressor, comprising a PLC controller and a PLC start relay connected to the PLC controller, and the PLC start relay is energized when the PLC controller starts; It is characterized in that The oil pressure interlock shutdown device for the screw compressor further comprises an oil pressure relay, a time relay and an oil pressure interlock control relay, The oil pressure relay is connected to a first voltage and connected to the oil pressure interlock control relay, and the oil pressure relay is connected to an oil pressure sensor, and the oil pressure relay is energized or de-energized under the influence of the oil pressure; The contact switch linked to the PLC start relay is connected to the time relay and connected to a second voltage at the same time, and when the PLC start relay is energized, the contact switch linked to the PLC start relay is closed; The contact switch linked to the oil pressure interlock control relay and the contact switch linked to the time relay are connected in series and connected to the stop signal, and the contact switch linked to the oil pressure interlock control relay is also connected to the PLC controller; wherein, when the oil pressure interlock control relay is energized, the contact switch linked to the oil pressure interlock control relay is closed; when the time relay is energized, after a certain time delay, the contact switch linked to the time relay is closed.

2. The oil pressure interlock shutdown device for a screw compressor according to claim 1, characterized in that The first voltage is 24V and the second voltage is 220V.

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