Steam trap device causing no steam leakage and control method of the same

Abstract

To solve problems such as steam leakage or a risk of steam leakage and unwanted excessive drainage accumulation or a risk of unwanted excessive drainage accumulation.SOLUTION: A drainage storage container stores drainage and includes: a drainage storage container (1) which includes an inlet, into which drainage and / or steam flows, at an upper part and an outlet, from which drainage is discharged, at a lower part; a level sensor (2) which measures a water level (W) of the drainage in the storage container; an orifice or a nozzle (3) provided at a tip of the outlet; a buffer part (4) provided at a tip of the orifice or the nozzle; an on-off valve (5) which is provided at a tip of the buffer part and can continuously change an opening degree; and a pressure sensor (6) which measures a pressure (P2) in the buffer part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a steam trap device that is free from steam leakage, and more particularly to a steam trap device equipped with an orifice or the like, and a control method thereof. [Background technology]

[0002] Steam trap devices are generally simply called "steam traps" and are classified into mechanical, thermostatic, and thermodynamic types. Mechanical types are said to have less steam leakage, and among them there is one called an orifice type or simply an orifice. The orifice is said to have been invented by Lawrence L. Guzik [Patent Document 1 ('870)] and is illustrated in FIG. 2A of the patent. It is a metal disk with holes of about 0.2 to 5 mm in diameter, and sometimes about 0.5 to 15 mm in diameter. Recently, there are devices with multiple orifices arranged in series (in the direction of steam flow). For example, see Patent Document 2 ('734) and Patent Document 3 ('461). Incidentally, the word "orifice" means "hole" in English, but those skilled in the art call the entire disk with holes (i.e., the trap) an orifice, and we will follow this here. There are also orifices (sometimes called pieces) that are not plate-shaped but have a shape such as that shown in reference numeral 30 (orifice member) in FIG. 3 of Patent Document 3 ('461), and calling them "orifice plates" is misleading.

[0003] Later, nozzles were developed that were not simply disks with holes, but had thickness in the direction of steam flow. For example, "Nozzle 5" in Figure 1 of Patent Document 4 ('644) is one such nozzle. In the explanation of this invention, orifices (theoretically zero hole thickness) and nozzles (hole thickness is significant) are sometimes collectively referred to as orifices, etc. Orifices and the like have a simple structure, and therefore are inexpensive and durable, and are actually commercially available and widely used. It is necessary to select an orifice with an appropriate hole diameter φ according to the amount of drain per hour. If φ is small, the drain cannot be discharged properly and excessive drain retention occurs, causing various problems. Conversely, if φ is large, steam leakage occurs or increases, resulting in energy loss. Recently, steam leakage has become a problem from the standpoint of global warming and energy conservation.

[0004] However, the amount of drainage per hour fluctuates. For example, in the case of a jacketed boiler heated with steam, the amount of drainage generated, i.e., the amount of drainage, differs when heating starts, when it is steady, and when the amount of heated material in the boiler changes. Also, in the middle of the piping that sends steam from the boiler to the boiler, the amount of drainage generated, i.e., the amount of drainage, differs in the piping due to changes in the outside air temperature, for example, morning, afternoon, evening, summer, winter, rainfall, snowfall, etc. In other words, the amount of drainage fluctuates. However, it is not practical to replace the orifice with an appropriate φ each time the drain amount changes, and it also increases costs. Therefore, since excessive drain retention is a more serious problem than steam leakage, an orifice with a larger φ is installed. As a result, there is an undeniable tendency for steam leakage to increase. Orifices, etc. should be used with drain discharge volumes of at least a quarter of the maximum drain discharge volume, and the range of drain discharge volumes in which they can be properly discharged is narrow. Conversely, if the drain discharge volume is less than a quarter of the maximum drain discharge volume, there will be a lot of steam leakage. So a steam trap was invented that has a needle valve after a large φ orifice, and closes the valve when the amount of drain is small, so that it functions the same as a small φ orifice. This is shown in Patent Document 5 ('533). This widens the range of drain discharge volumes at which drain can be properly discharged.

[0005] According to paragraph

[0037] of Patent Document 5 ('533), if there is a lot of drain on the drain inlet 5 side, the temperature T will drop, so the needle valve opening is increased to increase the drain flow rate (discharged to the outside). Also, according to paragraph

[0038] of the same document 5, if the difference between the pressure P1 before the orifice etc. (symbol 10) and the pressure P2 after it is small, it can be determined that the needle valve opening is small compared to the amount of drain, so the needle valve opening is increased to increase the drain flow rate (discharged to the outside). On the other hand, although it is not stated in the same document 5, as the drain flow rate (discharged to the outside) increases, pressure P2 decreases, so it is interpreted that the difference between pressure P1 and pressure P2 increases. Although it is not stated in the same document 5, if we interpret it the other way around and the difference between pressure P1 and pressure P2 increases, it can be determined that the opening is large compared to the amount of drain, so the opening of the needle valve is narrowed to reduce the drain flow rate (discharged to the outside). Also, when the amount of drain present on the drain inlet 5 side decreases and the temperature T rises, the opening of the needle valve is narrowed to reduce the drain flow rate (discharged to the outside). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 3,715,870 [Patent Document 2] Japanese Patent No. 6408734 [Patent Document 3] Patent Publication No. 2016-223461 [Patent Document 4] Japanese Patent No. 6340644 [Patent Document 5] Patent Publication No. 2022-33533 Summary of the Invention [Problem to be solved by the invention]

[0007] In the invention of Patent Document 5 ('533), paragraph

[0037] of that document states, "If there are many drains on the drain inlet 5 side, the temperature T will decrease, so...the opening is increased to increase the flow rate of drain passing through the second nozzle 20." However, temperature does not accurately measure whether a lot of drain is present, i.e., the amount of drain retention, and since there is a possibility of a time lag in the relationship between temperature and the amount of drain retention, there is a risk of excessive drain retention in front of the orifice, etc., or steam leakage due to inability to accurately control the opening of the needle valve. Excessive drain retention causes serious problems and must be avoided at all costs. The problem to be solved by the present invention is to solve the problem of steam leakage or the risk thereof, and the problem of excessive or the risk thereof due to unintended drain retention. [Means for solving the problem]

[0008] The present invention provides, as a first invention, "A steam trap device comprising: a drain storage container for storing drain, the drain storage container having an inlet at the top through which drain and / or steam flow in and an outlet at the bottom through which drain is discharged; a level sensor for measuring the water level (W) of the drain in the storage container; an orifice or nozzle (3) provided at the end of the outlet; a buffer section (4) provided at the end of the orifice or nozzle; an on-off valve (5) provided at the end of the buffer section that can be continuously changed in opening degree; and a pressure sensor (6) for measuring the pressure (P2) in the buffer section." to provide.

[0009] The present invention also provides, as a second invention, "In the steam trap device according to the first invention, a control method for a steam trap device, comprising: lowering a value of a second target value (SV2) below when the water level (W) measured by the level sensor (2) is higher than a first target value (SV1); maintaining the value of the second target value (SV2) below when the water level (W) is equal to the first target value (SV1); raising the value of the second target value (SV2) below when the water level (W) is lower than the first target value (SV1); operating the on-off valve (5) in a direction to open the on-off valve (5) when the pressure (P2) measured by the pressure sensor (6) is higher than the second target value (SV2); maintaining the on-off valve (5) without operating the on-off valve (5) when the pressure (P2) is equal to the second target value (SV2); and operating the on-off valve (5) in a direction to close the on-off valve (5) when the pressure (P2) is lower than the second target value (SV2)." to provide.

[0010] Furthermore, the present invention provides, as a third invention, "In the steam trap device according to the first invention, If the water level (W) measured by the level sensor (2) is higher than the first target value (SV1), the value of the second target value (SV2) below is lowered, if the water level (W) is equal to the first target value (SV1), the value of the second target value (SV2) below is maintained, if the water level (W) is lower than the first target value (SV1), the value of the second target value (SV2) below is raised, a pressure difference (ΔP=P1-P2) between the pressure (P2) measured by the pressure sensor (6) and the pressure in the internal space of the drain storage container (1) is P1, and when the pressure difference (ΔP) is equal to the second target value (SV2), the on-off valve (5) is operated in a direction to close, and when the pressure difference (ΔP) is equal to the second target value (SV2), the on-off valve (5) is maintained without being operated, and when the pressure difference (ΔP) is lower than the second target value (SV2), the on-off valve (5) is operated in a direction to open. to provide. Further, from another viewpoint, the present invention provides a fourth invention, "A drain storage container for storing drain, comprising: a drain storage container (1) having an inlet at the top through which drain and / or steam flow in and an outlet at the bottom through which drain is discharged; a level sensor (2) for measuring the water level (W) of the drain in the storage container; a branch pipe (12) that branches into n pieces (n is a natural number of 2 or more, preferably 3 or more) provided at the end of the outlet; an orifice or nozzle (3) provided at the end of the branch pipe; and an on-off valve (13) provided before or at the end of the orifice or nozzle (3), In accordance with the water level (W) measured by the level sensor (2), when the water level is high, all or a proper number of the n on-off valves (13) are opened, and when the water level is low, all or a proper number of the n on-off valves (13) are closed, thereby maintaining the water level (W) at a predetermined value. to provide. Effect of the Invention

[0011] In the present invention, a "drain storage container for storing drain" is provided upstream of the orifice, and a level sensor is provided there to accurately measure the amount of drain (drain accumulation). Then, the opening of the on-off valve is controlled according to the amount of drain (drain accumulation). As a result, drain discharge can be accurately controlled, and there is no excess or risk of drain accumulation upstream of the orifice. Also, since a predetermined amount of drain is always accumulated in the drain storage container, there is no risk of steam leakage. In addition, conventional orifices and the like are suitable for use at drain discharge rates of at least about one-fourth the maximum drain discharge rate, and have a problem in that the range of drain amounts at which they can be properly discharged is narrow. In contrast, the device of the present invention, which is equipped with an orifice and the like, can be used at drain discharge rates of up to about one-fourth the maximum drain discharge rate without steam leakage, and has a wide range. Furthermore, by controlling the opening degree of the on-off valve in two stages, LIC and PIC, the fluctuating drain water level (W) can be leveled out and the control can be made easier. This is also one of the effects of the present invention (first to third inventions).

[0012] In the present invention (first to third inventions), a continuously variable on-off valve (5) is provided downstream of the orifice, etc., so the amount of drain discharged to the outside (the drain flow rate) can be controlled or adjusted by this valve, and therefore an orifice etc. with a relatively large hole diameter φ can be used. As a result, the hole is less likely to be clogged with foreign matter, etc., and long-term operation is possible. This is also one of the effects of the present invention. In addition, in the present invention (first to third inventions), the pressure beyond the orifice is not suddenly lowered to atmospheric pressure (see below*), but by providing a buffer section (4), irregular fluctuations in pressure caused by the flashing phenomenon are eliminated, a stable pressure (P2) is obtained, and appropriate control is made possible by measuring the stable pressure (P2). This is also one of the effects of the present invention (first to third inventions). [※] The downstream side of an orifice is usually open to the atmosphere, and the pressure beyond the orifice is atmospheric pressure, but in some cases, a drain recovery device may be installed beyond the orifice, and in that case the pressure will be higher than atmospheric pressure. Therefore, it is expressed as atmospheric pressure, etc. The fourth invention has a common drain storage container (1), level sensor (2), and orifice etc. (3), but its concept is different from the first to third inventions. Conventionally, in a trap device equipped with a drain storage container, there was only one orifice etc. (3) (n=1), but in the fourth invention, n=2 or more. Therefore, the range of drain discharge volume at which the drain can be properly discharged without steam leakage is widened. This is the effect of the fourth invention. [Brief description of the drawings]

[0013] [Figure 1] 1 is a conceptual diagram showing a configuration of a steam trap device according to an example of an embodiment for carrying out the present invention (first invention). The drawing is not drawn to exact scale. [Diagram 2] FIG. 2 is a conceptual diagram for explaining the configuration of the control unit in FIG. 1 in the case of control method A. The diagram is not drawn to scale. [Diagram 3] FIG. 2 is a conceptual diagram for explaining the configuration of the control unit in FIG. 1 in the case of control method B. The diagram is not drawn to scale. [Figure 4]5 is a flowchart showing a control sequence of a "method of controlling a steam trap device" according to one example of an embodiment for carrying out the present invention (a second invention). [Diagram 5] FIG. 2 is a schematic diagram showing the configuration of the device of FIG. 1 to which a descaling device has been added. The drawing is not drawn to scale. [Figure 6] 1 is a conceptual diagram showing the configuration of a steam trap device according to an example of an embodiment for carrying out the present invention (fourth invention). The diagram is not drawn to exact scale. In this diagram, the branch pipe branches in the vertical direction of the paper, but it may branch horizontally or in any direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An example of this embodiment will be described with reference to Figures 1 to 4. This is merely one example. The steam trap device according to this example is a drain storage container for storing drain, and is composed of a drain storage container (1) having an inlet (1a) at the top through which drain and / or steam flow in and an outlet (1b) at the bottom through which drain is discharged, a level sensor (2) for measuring the water level (W) of the drain in the storage container, an orifice or the like (3) provided ahead (downstream) of the outlet, a buffer section (4) provided ahead (downstream) of the orifice or the like, an on-off valve (5) whose opening degree can be continuously changed provided ahead (downstream) of the buffer section, and a pressure sensor (6) for measuring the pressure in the buffer section. Although not shown, when measuring the pressure (P1) in the internal space of the drain storage container (1), another pressure sensor is provided in the upper part of the container (1). The drain storage container (1) is ultimately connected to an upstream boiler via piping through the inlet (1a). Therefore, the pressure (corresponding to P1) of the steam and drain flowing into the container (1) varies from, for example, about 100 to 2000 kPaG (gauge pressure), and the container (1) is a metal pressure-resistant container that is suitable for these pressures. The size is also appropriately determined according to the steam pressure and the amount of drain. For example, a cylindrical shape with a diameter φ of about 50 to 300 mm and a height h of about 100 to 800 mm is preferable.

[0015] In addition, if the temperature of the drain in the drain storage container (1) drops, the temperature of the steam in contact with the drain will also drop, resulting in the generation of excess drain. In other words, steam will be wasted and unnecessary steam will be consumed. Therefore, it is preferable to keep the container (1) warm by surrounding it with a passive or active heat-insulating means. On the other hand, the drain storage container (1) has an outlet (1b) at the bottom through which the drain is discharged, and the downstream end of the outlet (1b) is connected to an orifice (3). A level sensor (2) is attached to the drain storage container (1) to measure the water level (W) of the drain. The level sensor (2) is preferably one that can continuously measure the water level (W), but it may also be one that measures discontinuously or intermittently, or in the extreme case, one that measures three points, the maximum water level (H), the minimum water level (L) and the intermediate water level, or one that measures two points, the maximum water level (H) and the minimum water level (L). The value of the water level (W) measured by the level sensor (2) is sent to the control unit via wire or wirelessly. Specific examples of the level sensor (2) include an electrode rod type, a capacitance type, and a float type.

[0016] The drainage accumulated in the drainage container (1) enters the orifice or the like (3) from the outlet (1b). The orifice or the like (3) is an orifice or a nozzle. Either is a component with a small hole of diameter φ, through which the drainage is discharged. The size of the diameter φ is about 0.2 to 5 mm, as in the past, and about 0.5 to 15 mm in some cases. In the case of a nozzle, the length is about 10 to 40 mm, as in the past. Metals such as stainless steel, iron, and copper alloys are used as materials. The drain that enters the orifice (3) is discharged into the buffer section (4). The pressure (P2) inside the buffer section (4) is usually lower than the pressure (P1) inside the drain storage vessel (1). As a result, the drain that passes through the orifice (3) undergoes adiabatic expansion (reduced pressure) as the pressure is released, and it often evaporates and turns into steam due to a drop in boiling point. This phenomenon is called flashing, and it causes irregular fluctuations in the pressure downstream of the discharge, making it difficult to accurately measure the pressure downstream of the discharge, which is a "problem." In the past, the downstream side of the orifice (3) was often open to the atmosphere, and this "problem" was ignored. However, in the present invention, when an on-off valve (5) is provided downstream, this problem cannot be ignored.

[0017] Therefore, in the present invention, the pressure is not suddenly lowered to the final stage pressure such as atmospheric pressure, but a closed space (buffer section) is provided to eliminate the irregular fluctuations in pressure caused by the flashing phenomenon, thereby obtaining a stable pressure (P2) and enabling appropriate control by measuring the stable pressure (P2). On top of that, an on-off valve (5) that can be continuously adjusted is provided beyond the buffer section (4). In this sense, the place where a closed space (buffer space) is created is called the buffer section (4). The buffer section (4) is created in a specified pressure-resistant container. Usually, the relationship is "P1>P2>atmospheric pressure, etc." An example of the size and shape of the buffer section (4) is a cylinder with a diameter of about 20 to 100 mm and a length of about 50 to 150 mm. In terms of volume, it is about 0.02 to 1 liter. The buffer section (4) is made of a pressure-resistant container like the container (1). A pressure sensor (6) is attached to the buffer section (4) to measure the pressure (P2) in the internal space. The value of P2 is sent to the control section via wire or wirelessly. Specific examples of the pressure sensor (6) include a diaphragm type and a Bourdon tube type.

[0018] The on-off valve (5) can change the opening continuously from a minimum of 0% to a maximum of 100%, and for example, a needle valve, a globe valve, a butterfly valve, a diaphragm valve, etc. are used. The on-off valve (5) is also called a back pressure valve. The opening of the on-off valve (5) may be changed manually, but an on-off valve (5) that is electrically changed will be described using a needle valve as an example. The on-off valve (5), i.e., a needle valve, is equipped with a drive unit (for example, a forward / reverse motor), and the opening (0 to 100%) can be changed to an open or closed direction by turning the needle rod. The drive unit operates upon receiving a command (signal) from the control unit. The function of the control unit, i.e., the control method, will be described with reference to Figs.

[0019] [Control method 1 (second invention)] First, the level sensor (2) measures the drain water level (W) in the container (1) in response to an instruction from the control unit and transmits the value to the control unit. (It may also be constantly measured without receiving an instruction from the control unit.) ≪2≫ The control unit is roughly divided into the LIC and the PIC as shown in Figure 2, and the transmitted water level (W) value is compared with the first target value (SV1) in the LIC. ≪3a≫ When the water level (W) is higher than the first target value (SV1), the LIC lowers the second target value (SV2). That is, the LIC outputs a predetermined lowering amount (-MV1) to the PIC. This predetermined amount (change) is, for example, 0.1% to 5% when the pressure (P2) in the buffer section (4) corresponding to the opening of the on-off valve (5) being 0% is set to 100% and the pressure (P2) corresponding to the opening being 100% is set to 0% (same below). As shown in FIG. 3, the output (-MV1) of the LIC may be an absolute value (changed SV2 = unchanged SV2 + change) instead of the change (control method A). In this case, the output name is called MV1 (changed output) from the LIC side and the input name is called SV2 (changed input) from the PIC side, but the signal (numerical value) is the same.

[0020] ≪3b≫ When the water level (W) value is equal to the first target value (SV1), the LIC maintains the value of the second target value (SV2). In other words, it does not output MV1. Alternatively, it may output to the PIC an instruction to maintain the current SV2. ≪3c≫ When the water level (W) is lower than the first target value (SV1), the LIC raises the second target value (SV2). In other words, the LIC outputs a predetermined amount of increase (+MV1) to the PIC. This predetermined amount (change) is, for example, 0.1% to 5% as described above. As shown in FIG. 3, the LIC output (+MV1) may be an absolute value (changed SV2 = pre-change SV2 + change) instead of the change (control method A). In this case, the output name is called MV1 (changed output) from the LIC side, and the input name is called SV2 (changed input) from the PIC side, but the signal (numeric value) is the same. Next, the pressure sensor (6) measures the pressure (P2) in the buffer section (4) in response to an instruction from the control section, and transmits the measured value to the control section (PIC). (It may also be constantly measured without receiving an instruction from the control section.) <5> The transmitted pressure (P2) value is compared with the second target value (SV2) in the PIC. In this case, the PIC stores the pre-change SV2, and the second target value (SV2) is already the changed second target value (changed SV2) after receiving a signal of a predetermined amount (change amount, i.e. ±MV1) from the LIC, and is compared with this. In the case of control method B, the PIC directly compares the pressure (P2) with the second target value (changed SV2).

[0021] <6a> When the pressure (P2) is higher than the second target value (SV2), the PIC outputs a signal (+MV2) to the actuator to operate the on-off valve (5) in a direction to open the valve by a predetermined amount (change). The predetermined amount (change) is, for example, 0.1% to 5% in terms of opening (same below). Note that the output (+MV2) of the PIC may be control method B, which outputs an absolute value (opening after change = opening before change + change) instead of the change (control method A). In response to this, the on-off valve (5) will eventually open to 100%. <6b> When the pressure (P2) is equal to the second target value (SV2), the PIC maintains the opening of the on-off valve (5). In other words, it does not output MV2. Alternatively, it may output MV2 to the actuator to maintain the current opening. <6c> When the pressure (P2) is lower than the second target value (SV2), the PIC outputs a signal (-MV2) to the actuator to operate the on-off valve (5) in a direction to close the valve by a predetermined amount (change). The predetermined amount (change) is, for example, 0.1% to 5%, as described above. Note that the output (-MV2) of the PIC may be control method B, which outputs an absolute value (opening after change = opening before change + change) instead of the change (control method A). In response to this, the on-off valve (5) will eventually close to 0% opening or to the low limit (described below).

[0022] <7> The drive unit receives a signal [change or changed opening degree (absolute value)] from the control unit and operates the on-off valve (5) in the (a) opening direction, (b) maintaining the opening degree, or (c) closing direction. As a result, the amount of drainage passing through the on-off valve (5) (a) increases, (b) does not increase or decrease, or (c) decreases. As a result, the drain water level (W) (a) decreases and approaches the first target value (SV1), or (b) remains unchanged and is maintained equal to the first target value (SV1), or (c) increases and approaches the first target value (SV1) as new drainage enters from the inlet (1a). ≪8≫ Next, return to ≪1≫, measure the water level (W), and repeat the steps ≪1≫ to ≪7≫ several times. This control method is a dual feedback control (W and P2) combination method, which corresponds to what is generally called cascade control. The drain discharge speed of the trap is controlled by the amount of drainage (water level W) in the container (1) and the pressure in the buffer section (P2).

[0023] When the on-off valve (5) is closed, the pressure (P2) rises to approach the pressure (P1) in the internal space of the container (1), the pressure difference [P1-P2] decreases, and the drain discharge speed decreases. As a result, the drain water level (W) in the container (1) rises. This is a method for maintaining the water level (W) when the amount of drain generated is small, and conversely, when the amount of drain generated is large, the on-off valve (5) is opened to lower the pressure (P2) in the buffer section. This increases the pressure difference [P1-P2] and increases the drain discharge speed. As a result, the drain water level (W) decreases. As a result, the drain does not accumulate excessively beyond the maximum water level H in the container (1), nor does it fall below the minimum water level L, and the drain water level (W) can be maintained within a specified range, thereby preventing steam leakage when the amount of drain generated is small and excessive drain retention when the amount of drain generated is large. This is one of the effects of the present invention (first to third inventions).

[0024] LIC is an abbreviation for level (L) indication (I) regulation (C) control system, and PIC is an abbreviation for pressure (P) indication (I) regulation (C) control system. The reason for the two-stage control, LIC / PIC, is as follows. If one were to directly control the drain water level (W), which is the ultimate control goal, by controlling the drain water level (LIC), the amount of drain generated would constantly fluctuate, and the control would not be able to keep up with the fluctuations in the water level (W) unless the capacity of the drain storage container (1) was extremely large. By having two stages of control, the fluctuating water level (W) value can be averaged out, making control easier. This type of control is effective for a steam trap device (steam trap) that uses an orifice with a fixed opening area rather than a valve-opening type. In a conventional valve-opening type trap, this control method performs a discharge operation (drain discharge / stop) in response to changes in the drain water level (W), and the control theory is fundamentally different from that of the control method of the present invention (the second and third inventions).

[0025] [How to determine the first target value (SV1)] First, based on the actual shape of the drain storage container (1), the maximum water level (H) is determined to be slightly below the position of the inlet (1a), and then the minimum water level (L) is determined to be slightly above the position of the outlet (1b). If the distance between H and L is 100%, then L = 0% and H = 100%, and the water level (W) anywhere between 0% and 100% (including both ends) is set as the first target value (SV1). From a safety theory perspective, it is most preferable to set the first target value (SV1) at 50% or near it, but the first target value (SV1) may also be set to a water level (W) somewhere between 10 and 90% (inclusive), or to be even safer, the first target value (SV1) may be set to a water level (W) somewhere between 20 and 80% (inclusive), or to be even safer, the first target value (SV1) may be set to a water level (W) somewhere between 30 and 70% (inclusive), or to be even safer, the first target value (SV1) may be set to a water level (W) somewhere between 40 and 60% (inclusive).

[0026] [How to determine the initial value of the second target value (SV2)] The second target value (SV2) is determined (varies) according to the output (MV1) from the LIC, and the initial value will be described below. The initial value is set at the start of control and is anywhere between 0% (fully closed) and 100% (fully open) (including both ends) of the opening of the on-off valve (5). Usually, it is preferable to set the opening degree of 0% (fully closed) or 100% (fully open) as the initial value. Among them, the opening degree of 100% (fully open) is particularly preferable compared to the opening degree of 0% (fully closed). The reason is as follows. The opening degree of the on-off valve (5) has an opening degree range where abrupt changes occur, generally called a breakpoint, and while in other regions, the change in the "flow rate passing through the valve" with respect to the change in opening degree is smooth, in this region the change is abrupt. This abrupt change is generally less severe in the case of [open ⇒ closing operation] than in the case of [close ⇒ opening operation]. Also, when some trouble occurs in the early stage, if the initial value is the opening degree of 0% (fully closed), the drain is not discharged because it is fully closed, and there is a risk of excessive drain retention. On the other hand, if the initial value is the opening degree of 100% (fully open), the drain is discharged because it is fully open, and excessive drain retention is avoided. Therefore, it is particularly preferable in terms of safety to set the initial value to 100% (fully open). Even if the valve is opened 100% (fully open), the orifice (3) located upstream can minimize steam leakage (steam leakage that occurs when drain is not stored in the drain storage container (1) due to some trouble) due to the orifice effect. This is also one of the effects of the present invention.

[0027] The steam trap device of the present invention is installed in the middle and / or at the end of a heating system that uses steam to heat a jacketed kettle, etc. When the initial value of the second target value (SV2) is determined and operation of this heating system is started, the second target value (SV2) automatically converges to an appropriate value by the LIC to achieve the first target value. In other words, if the initial value of SV2 is not appropriate for achieving the first target value (SV1), the LIC will issue an instruction to change (increase or decrease) the second target value (SV2) (for example, if the liquid level W is higher than SV1, an instruction will be issued to lower SV2), and the on-off valve will open and close due to the control (PIC) to bring the pressure value (P2) closer to SV2. As a result, the first target value (SV1) will be achieved, and the second target value (SV2) will have converged at that point. In other words, the second target value (SV2) is controlled to increase or decrease by the LIC output to achieve the first target value (SV1), and the PIC output is controlled to increase or decrease accordingly to achieve the second target value (SV2). By repeating these steps, the initial value of the second target value (SV2) at the start of control is changed and converged to a value that is suited to the amount of drain generation at that time.

[0028] Usually, it is preferable to set the initial value (sometimes even during normal control) of the lower limit (minimum opening) of the opening of the on-off valve (5) to a value greater than 0%, for example, about 5% (low limit), rather than to 0%, i.e., to a control method that does not set the valve to fully closed (0% opening). This control method is referred to as the low limit method. The reason why we do not want to set the lower limit to 0% (fully closed) is as follows. When trying to increase the opening from the minimum opening, if we try to increase it from fully closed, a sudden change in the pressure (P2) in the buffer section may occur, which may cause a hunting phenomenon (repeated back and forth). Therefore, if we increase the opening from a slightly open state (for example, about 5% opening = low limit), we can avoid the occurrence of the same phenomenon and perform smooth flow control. The reason for setting it to about 5% is that the operation of an opening and closing valve has a mechanical "play", and if the minimum is set to about 2 to 3%, it may actually remain almost fully closed. On the other hand, if the lower limit is set significantly larger than about 5%, for example, about 10% or more, the control range (control ratio: called turndown) will be narrowed, and the value evaluation as an opening and closing valve will decrease. Therefore, taking these factors into consideration, the lower limit is set to about 5% (4% to 9%).

[0029] However, if for some reason the water level (W) in the drain storage container (1) drops too low (the normal control cannot keep up with the water level control), the low limit method is temporarily cancelled and the on-off valve (5) is fully closed. A control method that normally keeps the opening of the on-off valve (5) at about 50% is preferable. This is because when the amount of condensate flowing in increases and the water level (W) in the condensate storage container (1) begins to rise, the opening of the valve must be increased to increase the amount of condensate discharged, but it is safer to have a margin of error up to the maximum opening of 100%.

[0030] [Control method 2 (third invention)] Control method 2 is the same as control method 1 except for the PIC. In control method 1, the PIC uses the pressure (P2) measured by the pressure sensor (6) to compare P2 with a second target value (SV2). In contrast, in control method 2, the PIC uses the pressure difference (ΔP=P1-P2) between the pressures (P1) and (P2) in the internal space of the drain storage container (1) to compare the pressure difference ΔP with the second target value (SV2). When the pressure difference ΔP is higher than the second target value (SV2), the on-off valve (5) is operated in the closing direction (opposite to control method 1), when the pressure difference (ΔP) is equal to the second target value (SV2), the on-off valve (5) is kept not operated, and when the pressure difference (ΔP) is lower than the second target value (SV2), the on-off valve (5) is operated in the opening direction (opposite to control method 1).The only difference is the direction, and the specific operations are as explained in the explanation of control method 1.

[0031] [Widening the range of drain discharge volumes that can be properly discharged] With one orifice, the range of drainage volume at which drainage can be properly discharged is narrow. Therefore, in order to widen the range, even in this invention (first invention), multiple orifices (3) may be provided in parallel, and a buffer section (4), an on-off valve (5), a pressure sensor (6), a drive section, etc. may be provided downstream of each of the orifices, and the pressure P2 measured by each sensor (6) may be sent to the control section. In this case, the control section will perform more complicated control. [Foreign object removal device] As is the case with conventional steam trap devices, the steam trap device of the present invention is equipped with an orifice or the like, and therefore foreign matter contained in the steam, such as dirt and scale, may adhere to or accumulate around the hole, reducing the hole diameter φ or blocking the hole, resulting in poor drain flow or, in extreme cases, causing the hole to become clogged and preventing the drain from flowing. An example in which a foreign matter removal device is added to a steam trap device (FIG. 1) according to an embodiment of the present invention (first invention) will be described with reference to FIG. In Fig. 5, a new pipe (7) is attached to the bottom of the drain storage container (1), and an on-off valve (8) is attached midway through the pipe, with the end (downstream) open to the outside (atmosphere). The on-off valve (8) may be a valve that switches between on (100% opening) and off (0% opening), or may be an on-off valve whose opening can be varied continuously or stepwise from 0% to 100%. On the other hand, an on-off valve (9) similar to the on-off valve (8) is provided upstream of the drain storage container (1), and a pipe (10) branched off from the steam pipe extends further upstream and leads to the buffer section (4). An on-off valve (11) similar to the on-off valve (8) is provided midway through the pipe (10).

[0032] If no foreign matter is attached or accumulated in the orifice, etc. (3), the drain water level (W) should drop over time if the opening of the on-off valve (5) is increased, but if foreign matter attaches or accumulates, the hole of the orifice, etc. (3) narrows and the water level (W) does not drop. Therefore, the control unit calculates the relationship between the opening of the on-off valve (5) and the drain water level (W), monitors the calculation result every hour, and if the calculation result changes from a predetermined value, it is determined that foreign matter has attached or accumulated, and switches from the normal operation mode to the foreign matter removal mode. When the foreign object removal mode is entered, first, the on-off valve (9) is closed, and on the other hand, the on-off valve (11) and the on-off valve (8) are opened. Then, the drain in the drain storage container (1) flows by its own weight through the pipe (7) to the on-off valve (8). At the same time, the pressure P2 in the buffer section (4) increases to a pressure P1 equivalent to the steam pressure from the boiler. Therefore, the steam from the boiler flows into the buffer section (4), passes through the orifice etc. (3), enters the bottom of the drain storage container (1), and further passes through the pipe (7) and the on-off valve (8) to be discharged to the outside. Since the pressure P1 is very high, for example, 100 to 2000 kPaG, the steam passing through the orifice etc. (3) is very high speed, and if there is a foreign object there, it is peeled off and blown away, and the foreign object falls into the drain storage container (1) and is discharged to the outside through the pipe (7). In this way, the foreign object that has narrowed the hole diameter φ or blocked it is removed. After the foreign object removal mode has been performed for a predetermined period of time, the operation mode is returned to the normal operation mode. First, the on-off valve (9) is opened, while the on-off valves (11) and (8) are closed. This enters the normal operation mode.

[0033] [Fourth embodiment of the invention] An example of this embodiment will be described with reference to Fig. 6. This is merely an example. It is preferable that n is 3 or more, and n=4 in this example. The trap device of this embodiment is composed of a drain storage container (1) for storing drain, a level sensor (2) for measuring the drain water level (W) in the storage container, a branch pipe (12) that branches into four and is provided at the end of the outlet, a total of four orifices, etc. (3) provided at each end of the branch pipe, and a total of four on-off valves (13) provided before or at the end of the orifices, etc. (3). The on-off valve (13) here is an electromagnetic valve, and the drive unit (14) is a solenoid. The solenoid receives a signal from the control unit and turns the valve on (100% opening) or off (0% opening). In some cases, the on-off valve may be capable of varying the opening from 0% to 100% continuously or in steps. In this case, the control unit needs to issue more precise signals. Depending on the height of the water level (W) measured by the level sensor (2), if the water level (W) is high, all or an appropriate number of the four on-off valves (13) are opened, and if the water level (W) is low, all or an appropriate number of the four on-off valves (13) are closed, thereby maintaining the water level (W) at a predetermined value. The more the amount of drain flowing into the drain storage container (1) increases, the higher the water level (W), so the "appropriate number" is the number that corresponds to the state in which the water level (W) can be maintained at a predetermined value (about M in FIG. 6) by increasing the drain discharge capacity, i.e., by increasing the number of on-off valves (13) to be opened to suppress the rise. Conversely, the less the amount of drain flowing into the drain storage container (1) decreases, so the more the water level (W) decreases, so the "appropriate number" is the number that corresponds to the state in which the water level (W) can be maintained at a predetermined value (about M in FIG. 6) by decreasing the drain discharge capacity, i.e., by reducing the number of on-off valves (13) to be opened to suppress the fall.

[0034] In Fig. 6, the four on-off valves (13) are named No. 1, No. 2, No. 3, and No. 4 from the top. In this case, the hole diameter φ of the four orifices etc. (3) upstream of the on-off valves (13) is the same. When the amount of drain flowing into the drain storage container (1) remains constant, the water level (W) is maintained at M with the first and second on-off valves (13) open and the remaining two on-off valves (13), the third and fourth on-off valves (13), closed. In this state, as time passes, the amount of drainage flowing in increases, and if it is measured that the water level (W) has dropped from M to the higher H level, the control unit receives this measurement signal and outputs a signal to open the third on-off valve (13) to increase the number of open valves (13) by one to three. If it is still measured that the water level (W) has dropped from H to the higher HH level, the control unit receives this measurement signal and outputs a signal to open the fourth on-off valve (13) to increase the number of open valves (13) by one more to four. As a result, the water level (W) drops from HH to H to M. Conversely, if the amount of drain flowing into the drain storage container (1) decreases over time and it is measured that the water level (W) has dropped from M to the lower L level, the control unit receives this measurement signal and outputs a signal to close the second on-off valve (13) in order to reduce the number of open valves (13) by one to one. If it is still measured that the water level (W) has dropped from L to the lower LL level, the control unit receives this measurement signal and outputs a signal to close the first on-off valve (13) in order to further reduce the number of open valves (13) by one to zero. As a result, the water level (W) rises from L to M.

[0035] So far, the case has been described where the hole diameter φ of the four orifices etc. (3) is the same. However, the hole diameter φ may be increased continuously or stepwise from the first to the fourth. For example, when the maximum capacity per hour (drain discharge capacity) through which drain and / or steam passes or permeates the orifice etc. (3) is taken as 1 capacity, as shown in the following [Table 1], the first orifice etc. has a hole diameter φ that results in a capacity of 1, the second has a hole diameter φ that results in a capacity of 4, the third has a hole diameter φ that results in a capacity of 16, and the fourth has a hole diameter φ that results in a capacity of 64. The total capacity is 85. For example, if the capacity per hour is 50 kg / hr, the total capacity is 50 x 85 = 4250 kg / hr. [Table 1]

[0036] The above [Table 1] lists all the ways (modes) to select whether the first through fourth orifices are open (○) or closed (×). Since there are four orifices, there are theoretically 16 modes. For example, in mode 1, all orifices are closed (×), and the total capacity is 0. In mode 8, the first through third orifices are open (○), and the fourth orifice is closed (×), and the total capacity is 21. It is also possible to use only six modes, for example, modes No. 1, 2, 3, 5, 9, and 16, instead of using all 16 modes. This makes it easier to design and manufacture the control unit. Generally, it is said that orifices and the like should be used in the range of one-fourth (0.25) to four-fourths (1.00) of their maximum capacity because a small amount of drain causes a lot of steam leakage. If this range is applied to the above specific example, 50 x 0.25 = 12.5, so the above specific example is calculated to enable operation of the trap device without steam leakage and without excessive drain retention, even if the amount of "drain and / or steam" fluctuates in the range of 12.5 to 4250 kg / hr.

[0037] [Strainer] As explained in the section on "Foreign matter removal device" above, steam and / or drain may contain foreign matter such as garbage and scale (canned stone, limescale) derived from the boiler, which may directly clog holes in the orifices, etc. Therefore, it is preferable to provide a strainer (also called a filter or sieve) before (upstream of) the orifices, etc. Specifically, in FIG. 1, it is preferable to provide strainers at the inlet (1a) and outlet (1b). Also in FIG. 6, it is preferable to provide strainers before (upstream) the inlet, outlet, and branch pipe (12) of the drain flowing into the drain storage container (1), before (upstream) each orifice, etc. (3), etc. [Explanation of symbols] 1 Drain storage container 2. Level sensor 3. Orifice or nozzle (orifice, etc.) 4. Buffer section 5. Continuously variable opening valve 6. Pressure sensor 7. Piping 8. On-off valve 9. On-off valve 10 Piping 11...Shut-off valve 12...Branch pipe 13...Shut-off valve 14. Drive unit

Claims

1. A steam trap device comprising: a drain storage container (1) for storing drain, the drain storage container having an inlet at an upper part through which drain and / or steam flow in and an outlet at a lower part through which the drain is discharged; a level sensor (2) for measuring the water level (W) of the drain in the storage container; an orifice or nozzle (3) provided beyond the outlet; a buffer section (4) provided beyond the orifice or nozzle; an on-off valve (5) provided beyond the buffer section whose opening degree can be continuously changed; and a pressure sensor (6) for measuring the pressure (P2) in the buffer section.

2. The steam trap apparatus of claim 1, If the water level (W) measured by the level sensor (2) is higher than the first target value (SV1), the value of the second target value (SV2) below is lowered, if the water level (W) is equal to the first target value (SV1), the value of the second target value (SV2) below is maintained, and if the water level (W) is lower than the first target value (SV1), the value of the second target value (SV2) below is raised, a control method for a steam trap device, comprising the steps of: operating the on-off valve (5) in a direction to open the on-off valve (5) when the pressure (P2) measured by the pressure sensor (6) is higher than a second target value (SV2); maintaining the on-off valve (5) without operating the on-off valve (5) when the pressure (P2) is equal to the second target value (SV2); and operating the on-off valve (5) in a direction to close the on-off valve (5) when the pressure (P2) is lower than the second target value (SV2).

3. The steam trap apparatus of claim 1, If the water level (W) measured by the level sensor (2) is higher than the first target value (SV1), the value of the second target value (SV2) below is lowered, if the water level (W) is equal to the first target value (SV1), the value of the second target value (SV2) below is maintained, and if the water level (W) is lower than the first target value (SV1), the value of the second target value (SV2) below is raised, a pressure difference (ΔP=P1-P2) between the steam pressure in the internal space of the drain storage container (1) and the pressure (P2) measured by the pressure sensor (6) is higher than a second target value (SV2), the on-off valve (5) is operated in a direction to close, and when the pressure difference (ΔP) is equal to the second target value (SV2), the on-off valve (5) is maintained not to be operated, and when the pressure difference (ΔP) is lower than the second target value (SV2), the on-off valve (5) is operated in a direction to open.

4. The drain storage container for storing drain includes: a drain storage container (1) having an inlet at an upper portion through which drain and / or steam flow in and an outlet at a lower portion through which drain is discharged; a level sensor (2) for measuring the water level (W) of the drain in the storage container; a branch pipe (12) that branches into n pieces (n is a natural number of 2 or more) provided at the end of the outlet; orifices or nozzles (3) provided at the ends of the branch pipes; and an on-off valve (13) provided before or at the end of the orifices or nozzles (3), This steam trap device is characterized in that, depending on the water level (W) measured by the level sensor (2), if the water level is high, all or an appropriate number of the n on-off valves (13) are opened, and if the water level is low, all or an appropriate number of the n on-off valves (13) are closed, thereby maintaining the water level (W) at a predetermined value.

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