Electrically regulated mechanical seal hydraulic pressure follow-up system

Abstract

The application provides an electrically-regulated mechanical seal sealing liquid pressure follow-up system, which comprises a control system, a servo motor, a speed reducer, an electric push rod, a connecting sleeve, a pressure boosting cylinder, a manual liquid supplementing pump, a pressure transmitter, a temperature transmitter and pipeline valves. The servo motor is connected with the electric push rod through the speed reducer, the electric push rod is connected with the piston rod of the pressure boosting cylinder through a universal joint, and the shell of the electric push rod is connected with the cylinder body of the pressure boosting cylinder through the connecting sleeve. The application realizes that the mechanical seal sealing liquid pressure is always higher than the sealing cavity pressure of a shaft fluid equipment by a certain constant value. When the sealing cavity pressure changes or the sealing liquid leakage volume loss changes, the mechanical seal sealing liquid pressure changes accordingly, so that the pressure difference between the two is kept constant. The pressure transmitter measures the sealing cavity pressure and the sealing liquid pressure, and the temperature transmitter measures the sealing liquid temperature, which are all input into the control system. The control system takes the sealing liquid pressure as the control object, takes the measured sealing liquid pressure as the control feedback, adopts a PID regulation control algorithm and takes the sealing liquid temperature as the control correction parameter, so that the mechanical seal sealing liquid pressure is controlled to follow the sealing cavity pressure of the shaft fluid equipment through the above-mentioned control mode.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrically regulated mechanical seal sealant pressure follow-up system, belonging to the design of mechanical seal auxiliary system, and suitable for the shaft end sealing device of various shaft fluid equipment, such as pumps, kettles, compressors and other rotating, gas and liquid lubricated equipment. BACKGROUND

[0002] Mechanical seal is the most important shaft end sealing form in shaft fluid equipment. In actual work, mechanical seal almost needs to be matched with corresponding auxiliary system to improve the sealing working environment, improve the sealing stability and service life through temperature regulation, pressure regulation, flushing, cooling and lubrication of the auxiliary system. API 682 standard, also known as American Petroleum Institute 682 standard, is an international standard for mechanical seal auxiliary system, which provides the best guidelines for the design, selection, manufacturing, operation and running of mechanical seal auxiliary system. Under the API 682 standard, the existing mechanical seal auxiliary system is almost designed for constant pressure working condition. For variable pressure working condition, only PLAN53C and PLAN54 systems in API 682 standard can be used. The PLAN53C system realizes constant pressure ratio pressurization through the different areas of the two ends of the pressurizing cylinder piston, and has the problems of unadjustable pressure ratio, easy to cause blockage of the pressure pipe or pollution of the pressurizing cylinder under poor medium conditions, and further cause the pressurizing piston to be stuck, etc. These problems will cause the sealant pressure of the mechanical seal to be unable to follow the change of the seal cavity pressure under variable pressure working condition, and easily cause the mechanical seal to fail due to the reverse pressure. At the same time, the PLAN53C system uses hydraulic principle to pressurize, and it is difficult to obtain the mechanical seal running parameters such as liquid level and leakage in real time, and it is unable to make corresponding adjustment and control according to the running parameters, which does not meet the needs of the intelligent development of mechanical seal auxiliary system. Although the PLAN54 system does not have the above-mentioned shortcomings of the PLAN53C system, the PLAN54 system uses a pump as a pressurizing element and a high-precision regulating valve as a pressure regulating element, so the PLAN54 system has the shortcomings of large size, high cost and complex adjustment. The present application aims at the above-mentioned defects of the existing auxiliary system, and invents an electrically regulated mechanical seal sealant pressure follow-up system, which can effectively improve the operation stability and service life of the mechanical seal under variable working conditions. SUMMARY

[0003] In order to solve the problems of poor intelligence, low reliability, high cost and complex adjustment of the existing mechanical seal auxiliary system under variable working conditions, the present application provides an electrically regulated mechanical seal sealant pressure follow-up system, which realizes the constant pressure difference between the seal cavity pressure and the mechanical seal sealant pressure by electrically regulating when the seal cavity pressure changes or the sealant leakage volume loss, so as to ensure the safe and stable operation of the mechanical seal under variable working conditions.

[0004] The technical means adopted by the present application are as follows:

[0005] The electrically-regulated mechanical seal sealing liquid pressure follow-up system comprises a control system, a servo motor, a speed reducer, an electric push rod, a connecting sleeve, a pressure cylinder, a manual liquid supplement pump, a pressure transmitter, a temperature transmitter, a forced circulation device and pipeline valves.

[0006] Further, when the sealing cavity pressure changes or the sealing liquid leakage volume loss, the electrically-regulated mechanical seal sealing liquid pressure follow-up system changes the mechanical seal sealing liquid pressure follow-up by consuming electric power, keeps the pressure difference between the sealing cavity pressure and the mechanical seal sealing liquid pressure constant, and is equal to the preset pressure difference value in the control system.

[0007] Further, the electric push rod is connected with the pressure cylinder piston rod through a universal joint, and the shell of the electric push rod is connected with the pressure cylinder cylinder body through the connecting sleeve.

[0008] Further, when the mechanical seal sealing liquid is lost, the manual liquid supplement pump can be used to supplement the sealing liquid into the pressure cylinder.

[0009] Further, the control system controls the rotation of the servo motor, the rotation of the servo motor drives the pressure cylinder piston to make linear reciprocating motion through the speed reducer and the electric push rod, the linear reciprocating motion of the pressure cylinder piston changes the volumes of the pressure cylinder rodless cavity and the mechanical seal sealing liquid cavity, and finally changes the sealing liquid pressure, that is, the control system realizes the control mode of the sealing liquid pressure.

[0010] Further, the pressure transmitter measures the sealing cavity pressure and the sealing liquid pressure, and the temperature transmitter measures the sealing liquid temperature, which are input into the control system, the control system takes the sealing liquid pressure as the control object, takes the measured sealing liquid pressure as the control feedback, adopts the PID regulation control algorithm, takes the sealing liquid temperature as the control correction parameter, and realizes the closed-loop feedback follow-up control of the mechanical seal sealing liquid pressure following the sealing cavity pressure of the shaft fluid equipment through the control mode.

[0011] The control principle of the electrically-regulated mechanical seal sealing liquid pressure follow-up system is as follows:

[0012] When the pressure of the sealed cavity changes, the pressure transmitter measures the pressure of the sealed cavity and the pressure of the sealant and inputs them to the control system, and when the control system determines that the sum of the measured pressure of the sealed cavity and the constant pressure difference preset in the control system is not equal to the measured pressure of the sealant, a clockwise or counterclockwise rotation instruction at a given speed is sent to the servo motor, wherein the given speed is determined by a PID adjustment control algorithm according to the absolute value of the pressure difference and the correction of the sealant density to the sealant temperature measured by the temperature transmitter, and the clockwise or counterclockwise rotation is determined by the PID adjustment control algorithm according to the positive or negative of the pressure difference. After receiving the rotation instruction, the servo motor starts to rotate, and the rotation of the servo motor is converted into the linear reciprocating motion of the piston of the pressure increasing cylinder through the speed reducer, the electric push rod and the pressure increasing cylinder. The linear reciprocating motion of the piston of the pressure increasing cylinder changes the volume of the pressure increasing cylinder and the sealant cavity of the mechanical seal, and finally changes the pressure of the sealant. Thus, the measured pressure of the sealant is adjusted repeatedly as a control feedback, and the sealant pressure servo adjustment is completed when the control system determines that the sum of the measured pressure of the sealed cavity and the constant pressure difference preset in the control system is equal to the measured pressure of the sealant.

[0013] Compared with the prior art, the present application has the following beneficial technical effects:

[0014] 1) From the aspect of standards and norms, the present application provides a mechanical seal auxiliary system under variable pressure conditions, which is a beneficial supplement to the mechanical seal auxiliary system under variable pressure conditions according to the existing API682 standard.

[0015] 2) From the actual application effect, the present application can automatically adjust the pressure difference between the seal cavity pressure of the shaft fluid equipment and the sealant pressure of the mechanical seal to be equal to the preset pressure difference value in the control system when the seal cavity pressure changes or the sealant leakage volume loss, thereby preventing the mechanical seal from being invalidated due to the fluctuation of the seal cavity pressure, and completely solving the common problem of seal failure that always exists and cannot be avoided in the prior art.

[0016] 3) From the perspective of technical innovation, the control system of the present application adopts a PID adjustment control algorithm, which is more accurate, stable and sensitive. When the pressure of the sealed cavity fluctuates, the sealant pressure is accurately, subtly and sensitively adjusted to ensure the stability of the sealant pressure and avoid the impact on the mechanical seal, thereby completely changing the condition that the mechanical seal is easily impacted and causes failure in the prior art.

[0017] 4) From the perspective of technical development, the control system of the present application can obtain many seal running parameters in real time, including real-time position, torque, leakage amount and various state parameters, can monitor the seal running parameters to perform corresponding alarm and parking, and realizes intelligent monitoring and management of seal running and maintenance.

[0018] 5) The present application is more suitable for complex and difficult working conditions than the prior system scheme, because the medium side pressure pipeline of the booster cylinder is cancelled, under harsh medium conditions such as containing particles, powder, easy coking crystallization, etc., the booster cylinder piston is avoided to be stuck due to medium blockage of the pressure pipeline or medium blockage of the booster cylinder piston, and further, the mechanical seal counter pressure failure problem caused by these problems is avoided; BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0020] Figure 1 It is a schematic diagram of the principle of the electrically adjusted mechanical seal liquid pressure servo system of the present application.

[0021] In the figure: 1, control system, 2, servo motor, 3, speed reducer, 4, electric push rod, 5, intermediate sleeve, 6, universal joint, 7, booster cylinder, 8, safety valve, 9, ball valve, 10, temperature transmitter, 11, pressure transmitter, 12, ball valve, 13, mechanical seal, 14, reaction kettle, 15, ball valve, 16, forced circulation pump, 17, motor, 18, pressure transmitter, 19, check valve, 20, ball valve, 21, manual liquid supplementing pump, 22, exhaust stop valve, 23, booster cylinder built-in cooling water coil DETAILED DESCRIPTION

[0022] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] It is to be understood that the terms so far as the word "comprise" or "comprising" or "include" or "including" or "has" or "having" or "contain" or "containing" etc. shall mean "including but not limited to" and not "consist only of" or "consisting only of" or "consisting exclusively of" or "consists only of" or "consisting of" unless specifically so stated in such closing

[0025] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in these embodiments are not limiting to the scope of the present application unless specifically so stated. Also, it should be clearly understood that the drawings are merely shown to scale in some instances, but in other instances the dimensions of each part are not necessarily shown to scale. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail, but rather can be assumed to be known by those of ordinary skill in the art. In all examples shown and discussed herein, any specific values should be interpreted as merely illustrative and not as a limitation on the scope of the exemplary embodiments. Thus, other examples of the exemplary embodiments can have different values. It is noted that like numbers and letters on the figures identify like parts throughout the disclosure, thus, once one part is defined in one figure, it is not necessary to discuss it further in connection with other figures unless explicitly stated.

[0026] In the description of the present application, it is to be understood that the orientation or positional relationships indicated by terms such as "front", "back", "up", "down", "left", "right", "horizontal", "vertical", "top", "bottom", and the like are generally based on the orientation or positional relationships shown in the drawings, and are merely intended to facilitate the description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be understood as limiting the scope of protection of the present application. The orientation terms "inner", "outer" refer to the inner and outer relative to the outline of the parts themselves.

[0027] For purposes of the description hereinafter, spatial relative terms, such as "above", "below", "upper", "lower", and the like, can be used to describe the relative position of one element or feature to another as illustrated in the figures. It will be understood that the spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device is inverted, then the elements described as above other elements or features would now be oriented below the other elements or features. Thus, the examples terms "above" and "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial relative descriptors used herein interpreted accordingly.

[0028] In addition, it should be noted that the use of "first", "second", and the like words of distinction do not connote any actual physical or chronological order, but are merely used for convenience and clarity in identifying one element from another. Unless otherwise stated, the use of these words is not intended to limit the scope of the application claimed.

[0029] As shown in the accompanying drawings, Figure 1 An electrically regulated mechanical seal sealant pressure servo system, including a control system 1, a servo motor 2, a reducer 3, an electric push rod 4, a connecting sleeve 5, a booster cylinder 7, a manual sealant pump 21, pressure transmitters 11 and 18, temperature transmitters 10, forced circulation devices 16 and 17, and pipeline valves. The servo motor 2 and the electric push rod 4 are connected through the reducer 3, the electric push rod 4 is connected with the piston rod of the booster cylinder 7 through the universal joint 6, and the shell of the electric push rod 4 is connected with the cylinder body of the booster cylinder 7 through the connecting sleeve 5;

[0030] Further, when the seal cavity pressure of the reactor 14 changes or the sealant leakage volume loss of the mechanical seal 13, the electrically regulated mechanical seal sealant pressure servo system changes the sealant pressure of the mechanical seal 13 by consuming power, keeps the pressure difference between the seal cavity pressure of the reactor 14 and the sealant pressure of the mechanical seal 13 constant, and is equal to the pressure difference value preset in the control system 1;

[0031] Further, the electric push rod 4 is connected with the piston rod of the booster cylinder 7 through the universal joint 6, and the shell of the electric push rod 4 is connected with the cylinder body of the booster cylinder 7 through the connecting sleeve 5;

[0032] Further, when the sealant of the mechanical seal 13 is lost, the manual sealant pump 21 can be used to supplement the sealant in the booster cylinder in the case of online system;

[0033] Further, the control system 1 controls the rotation of the servo motor 2, the rotation of the servo motor 2 is converted into the linear reciprocating motion of the piston of the intensifier cylinder 7 through the speed reducer 3, the electric push rod 4 and the intensifier cylinder 7, the linear reciprocating motion of the piston of the intensifier cylinder 7 changes the volume of the sealed liquid cavity of the mechanical seal 13 and the pressure of the sealed liquid, that is, the control system realizes the control mode of the sealed liquid pressure;

[0034] Further, the pressure transmitters 11 and 18 measure the sealed cavity pressure and the sealed liquid pressure, and the temperature transmitter 10 measures the sealed liquid temperature, and input them to the control system 1, the control system 1 takes the sealed liquid pressure of the mechanical seal 13 as the control object, takes the sum of the measured sealed cavity pressure of the reactor 14 and the constant pressure difference preset in the control system 1 as the control target, takes the measured sealed liquid pressure as the control feedback, uses the PID regulation control algorithm and takes the sealed liquid temperature as the control correction parameter, through the control mode, realizes the closed-loop feedback servo control of the sealed liquid pressure of the mechanical seal 13 following the sealed cavity pressure of the reactor 14;

[0035] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrically regulated mechanical seal sealant pressure servo system, comprising a control system, a servo motor, a speed reducer, an electric push rod, a connecting sleeve, a booster cylinder, a manual sealant supplement pump, a pressure transmitter, a temperature transmitter and a pipeline valve; the servo motor is connected to the electric push rod through the speed reducer, the electric push rod is connected to the booster cylinder piston rod through a universal joint, and the outer shell of the electric push rod is connected to the booster cylinder body through the connecting sleeve; the pressure transmitter collects the seal cavity pressure and the sealant pressure, and the temperature transmitter collects the sealant temperature; the control system takes the sealant pressure of the mechanical seal as the control object, takes the measured sealant pressure as the control feedback, takes the sum of the measured seal cavity pressure of the reaction kettle and the constant pressure difference preset in the control system as the control target, adopts a PID regulation control algorithm and takes the sealant temperature as a control correction parameter, inputs the control system, controls the rotation of the servo motor, and realizes closed-loop feedback servo control of the sealant pressure of the mechanical seal following the seal cavity pressure of the reaction kettle.

2. The system of claim 1, wherein: The control system controls the rotation of the servo motor, the rotation of the servo motor drives the booster cylinder piston to make linear reciprocating motion through the speed reducer and the electric push rod, and the sealant pressure is adjusted by changing the sealant cavity volume.

3. The system of claim 1, wherein: When the mechanical seal sealant is lost, the manual sealant supplement pump can be used to supplement the sealant into the booster cylinder.

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