Additional liquid level controller of ship shell and tube heater and use method of additional liquid level controller

Abstract

The invention relates to an added liquid level controller of a ship shell and tube heater and a use method of the added liquid level controller. The added liquid level controller comprises a mechanical liquid level detection module, a pneumatic control module and an execution adjustment module which are in butt joint with an existing shell and tube heater through a standardized interface; the mechanical liquid level detection module comprises a floating ball detection assembly, the floating ball detection assembly comprises a floating ball and a vertical guide sleeve, and the floating ball is arranged in the vertical guide sleeve; two circulation holes are formed in the side wall of the vertical guide sleeve; the pneumatic control module is mounted in the explosion-proof shell and converts the mechanical displacement signal into a pneumatic signal capable of driving the actuating mechanism; the execution adjusting module is additionally arranged on a pipeline of a condensate water outlet of the shell and tube type heater through a standardized flange, and the condensate water discharge amount is adjusted through a ZJHP pneumatic single-seat adjusting valve so as to control the liquid level. The device is driven only through compressed air, accurate control over the condensate water liquid level is achieved, the heating efficiency and energy recovery are improved, and the device is suitable for safe and energy-saving transformation of ship shell and tube heaters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship heating equipment modification, in particular to a kind of ship shell and tube heater's add-on liquid level controller and its use method, especially suitable for the high temperature difference shell and tube heater of power not less than 8000KW in ship dangerous area (such as oil gas washing cabin area, fuel heating area), medium needs to be heated from 20 DEG C to 80 DEG C. BACKGROUND

[0002] Ship existing shell and tube heater (such as washing cabin water heater, fuel heater) is not equipped with special liquid level control device when leaving factory, only rely on simple drain valve group to discharge condensate, there are the following key problems in actual operation: (1) Safety hidden trouble is outstanding in dangerous area: traditional electronic liquid level controller is easy to produce spark in flammable and explosive environment, does not meet the safety requirements of IMO SOLAS convention on dangerous area equipment.

[0003] (2) Multiple losses caused by liquid level out of control: steam is wasted seriously when liquid level is too low, annual steam waste amount reaches 500-1500 tons; when liquid level is too high, heat exchange area is reduced by 40%-60%, and the outlet temperature of heated medium cannot reach the design value.

[0004] (3) Energy recovery is missing: high temperature condensate is directly discharged, and 15%-20% of steam sensible heat is not utilized.

[0005] Therefore, an independently installable, mechanically pneumatically driven, high explosion-proof grade liquid level controller is needed to solve the liquid level control problem of ship existing shell and tube heater. SUMMARY

[0006] The present application aims to overcome the above-mentioned deficiencies, provide a kind of ship shell and tube heater's add-on liquid level controller and its use method, provide intrinsic safety type liquid level controller, without modifying the structure of original heater, adapt to ATEX II 2GEx d IIB T4 Ga explosion-proof standard;Realize condensate liquid level accurate control, control precision is high;Improve system reliability, realize condensate waste heat recovery, reduce steam consumption.

[0007] The purpose of the present application is achieved as follows: A kind of ship shell and tube heater's add-on liquid level controller, including mechanical liquid level detection module, pneumatic control module and execution adjustment module, integrated in the same movable explosion-proof shell, through standardization interface and existing shell and tube heater docking; The inside of the shell and tube heater is provided with a plurality of heating pipes, the side of the shell and tube heater is provided with two through holes for docking with the add-on liquid level controller, the through holes are provided with mounting flanges, and the bottom of the shell and tube heater is provided with a condensate outlet; The mechanical liquid level detection module includes a float ball detection assembly in communication with the shell and tube heater through a standardized flange; the float ball detection assembly includes a float ball and a vertical guide sleeve, and the float ball is arranged in the vertical guide sleeve; two flow-through holes are formed in the side wall of the vertical guide sleeve; The pneumatic control module is installed in the explosion-proof shell, and converts the mechanical displacement signal into a pneumatic signal that can drive the actuator; The execution adjustment module is added to the pipeline at the condensate outlet of the shell and tube heater through a standardized flange, without changing the original pipeline direction, and the execution adjustment module includes a ZJHP pneumatic single-seat regulating valve, which adjusts the condensate discharge amount to control the liquid level through the ZJHP pneumatic single-seat regulating valve; The ZJHP pneumatic single-seat regulating valve includes a valve body structure, a sealing design and an actuator; The valve body structure of the ZJHP pneumatic single-seat regulating valve adopts a stainless steel valve body, and the valve core of the ZJHP pneumatic single-seat regulating valve is a V-shaped opening or a parabolic type, with linear flow characteristics, which meets the linear control requirements of the liquid level; Standardized flanges are arranged at both ends of the valve body of the ZJHP pneumatic single-seat regulating valve, which are consistent with the flange specifications of the condensate outlet pipeline of the shell and tube heater, and are sealed and connected with the condensate outlet pipeline through 120 DEG C-resistant fluororubber gaskets; The control logic of the ZJHP pneumatic single-seat regulating valve is as follows: When the liquid level is less than or equal to 0, a valve closing signal is received: the actuator of the ZJHP pneumatic single-seat regulating valve is supplied with air in the valve closing cavity, the push rod drives the valve core to move downward, the valve is fully closed, the opening degree is 0%, the condensate discharge of the original heater is blocked, and the steam is prevented from entering the pipeline; When the liquid level is greater than 0 and less than 2 / 5H, a position maintaining signal is received: the pressure in the two cavities of the actuator of the ZJHP pneumatic single-seat regulating valve is balanced, the position of the valve core changes linearly with the pneumatic signal, when the ideal liquid level is 1 / 3H, the opening degree of the valve is stabilized at 30%-50%, and the liquid level in the original heater is maintained stable; When the liquid level is greater than or equal to 2 / 5H, an opening signal is received: the actuator of the ZJHP pneumatic single-seat regulating valve is supplied with air in the valve opening cavity, the push rod drives the valve core to move upward, the valve is fully opened, the opening degree is 100%, and the excess condensate in the original heater is quickly discharged.

[0008] Further, a connecting flange is arranged at the flow-through hole and is sealed and connected with the mounting flange on the side wall of the shell and tube heater through a 120 DEG C-resistant graphite gasket without welding; the bottom end of the vertical guide sleeve extends to the bottom of the shell side of the shell and tube heater by 100 mm, and stainless steel limiting blocks are arranged at the upper and lower ends of the vertical guide sleeve to limit the travel of the float ball, corresponding to the liquid level of 0 to 2 / 5H, and are adapted to the height of the shell side of the shell and tube heater.

[0009] Further, the mechanical liquid level detection module further comprises a connecting rod-cam transmission assembly, the top of the floating ball is welded with a rigid stainless steel connecting rod, the top end of the connecting rod is fixedly connected with an external mechanical cam through a flange of a vertical guide sleeve, the center of the mechanical cam is rotationally connected with the explosion-proof shell through a stainless steel rotating shaft, and deep groove ball bearings are arranged at both ends of the rotating shaft; The profile of the mechanical cam is designed according to the liquid level threshold of the shell-and-tube heater: Liquid level = 0, i.e. no condensate in the shell side of the shell-and-tube heater: the floating ball is lowered to the lowest position, the cam flange is at the lowest position, and a subsequent “valve closing signal” is triggered; Liquid level = 1 / 3H, i.e. ideal liquid level of the shell-and-tube heater: the floating ball is raised to the middle position, the cam flange is at the gentle section, and a “liquid level maintaining signal” is output; Liquid level = 2 / 5H, i.e. high liquid level threshold of the shell-and-tube heater: the floating ball is raised to the highest position, the cam flange is at the highest position, and a “valve opening signal” is triggered; The edges of the mechanical cam are marked with liquid level scale lines: 0, 1 / 3H, and 2 / 5H, cooperating with a pointer, and being fixed to the explosion-proof shell, so that the corresponding liquid level state of the cam can be directly observed, and it is auxiliary to determine whether the detection module is working normally.

[0010] Further, the pneumatic control module comprises a mechanical pilot valve, a pneumatic amplifier and a gas path pretreatment assembly; The mechanical pilot valve adopts an explosion-proof two-position three-way slide valve, one end of the valve rod of the mechanical pilot valve is tightly attached to the profile of the mechanical cam through a compression spring, and the other end is connected with a valve core in the valve body; when the mechanical cam rotates, the valve rod of the mechanical pilot valve moves up and down along the profile of the mechanical cam, and switches the gas path channel; Liquid level ≤ 0, i.e. low position of the cam: the valve rod moves downward, the mechanical pilot valve connects the “valve closing gas path”, and outputs 0.4MPa compressed air; 0 < liquid level < 2 / 5H, i.e. middle position of the cam: the valve rod is at the middle position, the pilot valve connects the “liquid level maintaining gas path”, and outputs 0.2-0.3MPa compressed air; Liquid level ≥ 2 / 5H, i.e. high position of the cam: the valve rod moves upward, the pilot valve connects the “valve opening gas path”, and outputs 0.4MPa compressed air; The pneumatic amplifier adopts an explosion-proof amplifier, the input port is connected with the output port of the pilot valve, and the output port is connected with an execution adjustment module; the small flow signal output by the mechanical pilot valve, which is not greater than 0.1m³ / h, is amplified to be greater than or equal to 1m³ / h, so as to ensure that the response time of the execution mechanism is less than 0.8 seconds, and the liquid level in the shell-and-tube heater 1 is prevented from being continuously out of control; The air path pretreatment assembly includes an air filter pressure reducing valve, an oil mist separator and a micro gas tank; the air path is connected in sequence to the air filter pressure reducing valve, the oil mist separator, the gas tank and the mechanical pilot valve, and is independent of the gas source system of the shell and tube heater; the air filter pressure reducing valve is provided with a pressure gauge interface, so that the gas source pressure can be directly monitored without the need for additional pressure monitoring components.

[0011] Further, the nominal diameter of the valve body of the ZJHP pneumatic single seat regulating valve is DN25-DN50, which is suitable for 8000KW heater with a maximum condensate discharge of 37.5t / h; the valve seat is made of hard alloy overlaying, which is resistant to erosion and corrosion; the sealing design of the ZJHP pneumatic single seat regulating valve adopts a double sealing structure of soft sealing and hard sealing; the upper valve cover of the ZJHP pneumatic single seat regulating valve adopts bellows sealing; the valve core and the valve seat sealing surface of the ZJHP pneumatic single seat regulating valve are combined with fluorine rubber and hard alloy.

[0012] Further, the floating ball detection assembly of the mechanical liquid level detection module includes a floating ball, a vertical guide sleeve, a floating ball hinge, a flow hole, a connecting flange, a displacer arm and a drain plug; the floating ball is connected to one end of the displacer arm through the floating ball hinge; the other end of the displacer arm is connected to a controller; the floating ball hinge is arranged in the vertical guide sleeve; the top of the vertical guide sleeve is provided with a transverse branch pipe connected to the controller, and the transverse branch pipe is provided with the displacer arm; the bottom of the vertical guide sleeve is provided with the drain plug.

[0013] Further, the pneumatic control module includes a pneumatic positioner, a pneumatic controller A, a pneumatic controller B, a pneumatic amplifier A, a pneumatic amplifier B and a bellows; the pneumatic controller A includes an eccentric cam A, a roller A, a feedback pendulum rod A, a lever A and a baffle A; the pneumatic controller B includes an eccentric cam B, a roller B, a feedback pendulum rod B, a lever B and a baffle B; the center shaft of the eccentric cam A is connected to one end of the feedback pendulum rod A; the other end of the feedback pendulum rod A is connected to one end of the displacer arm; the outer edge of the cam of the eccentric cam A is provided with a sliding matching roller A; the roller A is arranged on the lever A; the bottom of the lever A is provided with the baffle A; one side of the baffle A is provided with the pneumatic amplifier A; the nozzle A of the pneumatic amplifier A is aligned with the baffle A; the pneumatic amplifier A is further provided with a balance orifice A; The output port of the pneumatic amplifier A is connected to one end of the bellows; the other end of the bellows is welded to the top of the lever C; the bottom of the lever C is connected to the lever B; the lever C is connected below the baffle B; one side of the baffle B opposite to the lever B is provided with the pneumatic amplifier B; the nozzle B of the pneumatic amplifier B is aligned with the baffle B; the pneumatic amplifier B is further provided with a balance orifice B; the pneumatic amplifier B is connected to the ZJHP pneumatic single seat regulating valve to drive the air driven valve to open. The lever B is provided with a roller B which is slidingly arranged at the outer edge of an eccentric cam B, the central shaft of the eccentric cam B is connected to one end of a feedback swing lever B, and the other end of the feedback swing lever B is connected to the valve core of a ZJHP pneumatic single-seat regulating valve; the ZJHP pneumatic single-seat regulating valve is further connected with a pneumatic positioner. The pneumatic positioner is connected with a controller, and the ZJHP pneumatic single-seat regulating valve is connected to the condensate outlet pipeline of the shell-and-tube heater.

[0014] Further, the controller is controlled through a 4-20mA circuit, the ZJHP pneumatic single-seat regulating valve is connected with the controller through a 4-20mA circuit to realize the conversion between electric signal and pneumatic signal; and the ZJHP pneumatic single-seat regulating valve is connected to the pipeline of the condensate outlet of the shell-and-tube heater.

[0015] Further, the execution regulating module further comprises a manual emergency mechanism: a manual operation hand wheel is arranged at the top of the execution mechanism and is connected with a push rod through a worm and a worm gear; when the gas source is interrupted, the hand wheel can be directly used to adjust the opening degree of the valve core, the adjustment accuracy is ±2%, and the emergency operation of the shell-and-tube heater is not affected; an electrostatic grounding terminal is arranged beside the hand wheel and is connected with the shell of the shell-and-tube heater through a copper core wire with a cross-sectional area of ≥2.5mm², the grounding resistance is ≤4Ω, and the electrostatic accumulation generated by the condensate flow is avoided, and an independent grounding device does not need to be additionally arranged.

[0016] The use method of the above-mentioned liquid level controller for a shell-and-tube heater of a ship comprises the following contents: S1, controller positioning and fixing: The controller is pushed to the side of the shell-and-tube heater and is locked, and is aligned with the spare flange of the shell of the shell-and-tube heater and the flange of the condensate outlet pipeline; S2, mechanical liquid level detection module docking: The connecting flange on the vertical guide sleeve of the mechanical liquid level detection module is sealingly connected with the mounting flange on the shell-and-tube heater, and the connecting rod is adjusted so that the position of the floating ball is aligned with the scale of the cam; S3, execution regulating module docking: The ZJHP pneumatic single-seat regulating valve of the execution regulating module is connected with the flange of the condensate outlet pipeline of the shell-and-tube heater; S4, connecting gas circuit: The controller gas circuit is connected, a pressure gauge is installed to monitor the gas source pressure, and the gas tightness of the test circuit is tested; S5, threshold calibration: Hot water is injected to simulate condensate, and the liquid level threshold and the opening degree of the regulating valve are calibrated; S6, safety and function check: The explosion-proof performance and the leakage amount of the regulating valve are tested, and the shell-and-tube heater is started to verify the control effect.

[0017] Compared with the prior art, the application has the following advantages: The application provides a retrofitted liquid level controller for a marine shell-and-tube heater and a use method thereof. The retrofitted liquid level controller is connected to the original heater through a standardized flange, has no electrical element, is driven by compressed air only, and realizes accurate condensate liquid level control. The application solves the problem of liquid level control in a hazardous area, improves heating efficiency and energy recovery, and is suitable for safe and energy-saving modification of the shell-and-tube heater of a ship. The application has the following specific advantages: (1) No modification and retrofitting, strong compatibility: the standardized flange is connected, and the installation period is greatly shortened; (2) Intrinsic safety, suitable for hazardous areas: no electrical element, in line with ATEX explosion-proof standard; (3) Accurate liquid level control: control accuracy ≤ ± 10 mm, steam consumption is reduced by 20%-22%; (4) High reliability and easy maintenance: greatly reduces faults, and modular design is convenient for maintenance; (5) Energy saving and waste heat recovery: condensate sensible heat recovery efficiency is greatly improved; (6) Strong compliance: in line with IMO SOLAS convention, MARPOL appendix VI and ship classification society certification requirements. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a structural schematic diagram of a shell-and-tube heater of embodiment 1 of the application.

[0019] Figure 2 FIG. 2 is a schematic diagram of a heating pipe of the shell-and-tube heater of embodiment 1 of the application.

[0020] Figure 3 FIG. 3 is an installation schematic diagram of the retrofitted liquid level controller of embodiment 1 of the application.

[0021] Figure 4 FIG. 4 is a structural schematic diagram of a retrofitted liquid level controller of embodiment 2 of the application.

[0022] Figure 5 FIG. 5 is a swing comparison schematic diagram of a displacer arm of embodiment 2 of the application.

[0023] Figure 6 FIG. 6 is a principle schematic diagram of the retrofitted liquid level controller of embodiment 2 of the application.

[0024] Figure 7 FIG. 7 is a principle schematic diagram of a retrofitted liquid level controller of embodiment 3 of the application.

[0025] Wherein: Shell and tube heater 1, heating tube 1.1, mounting flange 1.2, condensate outlet 1.3, float detection assembly 2, float 2.1, vertical guide sleeve 2.2, float hinge 2.3, flow-through hole 2.4, connecting flange 2.5, displacer arm 2.6, bleed plug 2.7, controller 3, ZJHP pneumatic single-seat regulating valve 4, pneumatic positioner 5, pneumatic controller A 6, eccentric cam A 6.1, roller A 6.2, feedback swing lever A 6.3, lever A 6.4, baffle A 6.5, pneumatic controller B 7, eccentric cam B 7.1, roller B 7.2, feedback swing lever B 7.3, lever B 7.4, baffle B 7.5, lever C 7.6, pneumatic amplifier A 8, nozzle A 8.1, balanced orifice A 8.2, pneumatic amplifier B 9, nozzle B 9.1, balanced orifice B 9.2, bellows 10. DETAILED DESCRIPTION

[0026] In order to better understand the technical solutions of the present application, the following will be described in detail in combination with relevant drawings. It should be understood that the following specific examples are not intended to limit the specific implementation manners of the technical solutions of the present application, and are only implementation manners that can be adopted by the technical solutions of the present application. It should be noted that the expressions about the positional relationship of each component in this article, such as that the A component is located above the B component, are based on the expressions about the relative positions of each component in the drawings, and are not intended to limit the actual positional relationship of each component.

[0027] Example 1: mechanical pneumatic control type Reference Figures 1-3 , Figure 3 An installation schematic diagram of an added liquid level controller of a ship shell and tube heater of this example 1 is drawn. As shown in the figure, the added liquid level controller of the ship shell and tube heater of this example 1 is an independent modular structure, which includes a mechanical liquid level detection module, a pneumatic control module and an execution adjustment module, is integrated in a same movable explosion-proof shell, is connected to an existing shell and tube heater 1 through a standardized interface, is driven by only 0.4-0.6 MPa ship compressed air, and does not have any electrical elements.

[0028] The movable explosion-proof shell is made of cast aluminum material, the mechanical liquid level detection module, the pneumatic control module and the execution adjustment module are integrated and installed, a universal wheel (load-bearing ≥ 500 kg) with a brake is arranged at the bottom to facilitate movement and positioning in a small space on a ship, an explosion-proof surface design (gap ≤ 0.15 mm, length ≥ 25 mm) is used at the joint of the shell, an explosion-proof gland is used for the cable interface, which meets the Exd explosion-proof requirement, and there is no structural association with the existing shell and tube heater 1, an inspection window is arranged on the side of the explosion-proof shell, the inspection window is provided with a cover plate fastened by explosion-proof bolts, which facilitates the maintenance of internal pneumatic elements without the need to disassemble the entire controller.

[0029] The shell and tube heater 1 is internally provided with a plurality of heating tubes 1.1, the side of the shell and tube heater 1 is provided with two through holes for docking with an additional liquid level controller, the through hole is provided with a mounting flange 1.2, and the bottom of the shell and tube heater 1 is provided with a condensate outlet 1.3.

[0030] The mechanical liquid level detection module includes a floating ball detection assembly 2 and a connecting rod-cam transmission assembly, which communicates with the shell and tube heater 1 through a standardized flange, without the need to modify the original equipment, converts the condensate liquid level change into a mechanical displacement signal, and has a liquid level visual observation function.

[0031] The floating ball detection assembly 2 includes a floating ball 2.1 and a vertical guide sleeve 2.2, the floating ball 2.1 is arranged in the vertical guide sleeve 2.2; two flow-through holes 2.4 are formed in the side wall of the vertical guide sleeve 2.2, to ensure that the condensate can freely enter and exit, and the floating ball changes synchronously with the liquid level in the original heater; a connecting flange 2.5 is arranged at the flow-through hole 2.4, and the connecting flange 2.5 is sealingly connected with the mounting flange 1.2 on the side wall of the shell and tube heater 1 through a 120 DEG C-resistant graphite gasket, without welding; the bottom end of the vertical guide sleeve 2.2 extends to a position 100 mm from the bottom of the shell side of the shell and tube heater 1, and stainless steel limiting blocks are arranged at the upper and lower ends of the vertical guide sleeve 2.2, to limit the floating ball stroke, correspond to the liquid level 0-2 / 5H, and adapt to the height of the shell side of the shell and tube heater 1.

[0032] The floating ball 2.1 is a 316L stainless steel hollow floating ball with a diameter of 120-180 mm and a wall thickness of 3 mm, which is resistant to 120 DEG C high temperature, seawater and condensate corrosion; the vertical guide sleeve 2.2 is made of 316L stainless steel, and the inner diameter of the vertical guide sleeve 2.2 is 5-8 mm larger than that of the floating ball 2.1.

[0033] A transparent borosilicate glass section is arranged in the middle of the vertical guide sleeve 2.2, with a length of 200 mm, resistant to 120 DEG C high temperature, and an explosion-proof grade of Ex d IIB T4, so that the position of the floating ball can be directly observed, and the traditional liquid level sight glass function is replaced, without the need to additionally arrange an observation component.

[0034] The connecting rod-cam transmission assembly: a rigid stainless steel connecting rod is welded to the top of the floating ball 2.1, the diameter of the connecting rod is 10-15 mm, and the length is customized according to the height of the shell side of the shell and tube heater 1; the top end of the connecting rod is fixedly connected with an external mechanical cam through a flange of the vertical guide sleeve 2.2; the mechanical cam is made of 45 steel, the surface is chrome plated, the hardness is HRC 50-55, the center of the cam is rotationally connected with an explosion-proof shell through a stainless steel rotating shaft, deep groove ball bearings are arranged at both ends of the rotating shaft to reduce the rotating resistance, and the ship pitching environment is adapted; The profile of the mechanical cam is designed according to the liquid level threshold of the shell and tube heater 1. Liquid level = 0 (No condensate in the shell side of the shell-and-tube heater 1): The float ball is lowered to the lowest position, the cam flange is in the lowest position, and the subsequent "valve closing signal" is triggered; Liquid level = 1 / 3H (Ideal liquid level of the shell-and-tube heater 1): The float ball is raised to the middle position, the cam flange is in the gentle section, and the "position maintaining signal" is output; Liquid level = 2 / 5H (High liquid level threshold of the shell-and-tube heater 1): The float ball is raised to the highest position, the cam flange is in the highest position, and the "valve opening signal" is triggered; The edges of the mechanical cam are marked with liquid level scale lines: 0, 1 / 3H, and 2 / 5H, which are matched with the pointer and fixed in the explosion-proof shell, so that the corresponding liquid level state of the cam can be directly observed, and it is auxiliary to determine whether the detection module is working normally.

[0035] The pneumatic control module is installed in the explosion-proof shell and converts the mechanical displacement signal into a pneumatic signal that can drive the actuator, including: Mechanical pilot valve: an explosion-proof two-position three-way slide valve (model Norgren VM2010, ATEX II 2G Ex dIIB T4) is used, one end of the valve rod is tightly fitted with the cam profile through a compression spring (material selected as Inconel 718, resistant to 120℃ high temperature, to avoid spring fatigue in the high temperature environment of the ship), and the other end is connected with the valve core in the valve body; when the cam rotates, the valve rod moves up and down with the cam profile, switching the gas path channel; Liquid level ≤ 0 (Low cam position): the valve rod moves down, the pilot valve connects the "valve closing gas path", and outputs 0.4MPa compressed air; 0 < liquid level < 2 / 5H (Cam middle position): the valve rod is in the middle position, the pilot valve connects the "position maintaining gas path", and outputs 0.2-0.3MPa compressed air; Liquid level ≥ 2 / 5H (High cam position): the valve rod moves up, the pilot valve connects the "valve opening gas path", and outputs 0.4MPa compressed air; Pneumatic amplifier: an explosion-proof amplifier Festo VPPM-6L-L-1-G18-0L10H-A4P is selected, the input port is connected with the output port of the pilot valve, and the output port is connected with the execution adjustment module; the small flow signal (≤0.1m³ / h) output by the pilot valve is amplified to ≥1m³ / h, ensuring that the response time of the actuator is <0.8 seconds, and avoiding that the liquid level in the shell-and-tube heater 1 is continuously out of control; Air path pretreatment assembly: including air filter pressure reducing valve (SMC AW40-06BG, filter precision 5μm, stable pressure range 0.4-0.6MPa), oil mist separator (filter precision 0.3μm, remove oil in air source) and micro gas tank (316L stainless steel, capacity 10L, working pressure 0.8MPa); the air path is connected in turn air filter pressure reducing valve→oil mist separator→gas tank→pilot valve, to ensure clean and stable air source, avoid pneumatic components blockage, and independent of the original heater gas source system; The air filter pressure reducing valve is provided with a pressure gauge interface (adapted to explosion-proof pressure gauge, range 0-1MPa), which can directly monitor the air source pressure without additional pressure monitoring components.

[0036] The execution adjustment module is installed on the pipeline of the condensate outlet 1.3 of the shell and tube heater 1 through a standardized flange, without changing the original pipeline direction, adopts ZJHP pneumatic single seat regulating valve 4 as the core execution element, adapts to the high temperature and high pressure difference of condensate, and adjusts the condensate discharge to control the liquid level; The ZJHP pneumatic single seat regulating valve 4 comprises: Valve body structure: adopting 316L stainless steel valve body, nominal diameter DN25-DN50, adapting to 37.5t / h maximum condensate discharge of 8000KW heater, selecting “single seat, sleeve guide” structure for high pressure difference characteristics of condensate, the valve seat adopts hard alloy cladding, which is resistant to erosion and corrosion; the valve core is “V-shaped opening” or “parabolic type”, and the flow characteristic is linear (adjustment accuracy ≤±1%), which adapts to the linear control requirement of liquid level; Sealing design: adopting “soft sealing + hard sealing” double sealing structure, the upper valve cover is “corrugated pipe sealing” (316L stainless steel corrugated pipe, resistant to 120℃ high temperature), to avoid condensate leakage from the valve stem; the sealing surface of the valve core and the valve seat adopts fluororubber + hard alloy combination, the leakage level reaches VI level (bubble level), to ensure no steam leakage at low liquid level; Actuator: matched with explosion-proof double-acting diaphragm actuator (model ZHA / B-22, diaphragm material is nitrile rubber reinforced layer, resistant to 120℃ high temperature), without spring return structure (to avoid spring fatigue failure caused by ship rolling), output force ≥5000N, adapting to the working pressure difference of 0.3-0.6MPa of condensate pipeline; the gas cavities at both ends of the actuator are connected with the “open valve output port” and “close valve output port” of the pneumatic amplifier respectively; Standardized docking: the standardized flanges are arranged at both ends of the valve body (consistent with the flange specifications of the condensate outlet pipeline of the shell and tube heater 1, such as DN40 PN1.6MPa), which are sealed connected with the original pipeline through 120℃ resistant fluororubber gasket, without cutting the original pipeline; The control logic of the ZJHP pneumatic single seat regulating valve 4: Receive "valve closing signal" (liquid level ≤ 0): actuator "valve closing chamber" intake, push rod drives the valve core to move down, the valve is fully closed (opening degree 0%), blocking the condensate discharge of the original heater, preventing steam from entering the pipeline; Receive "position maintaining signal" (0 < liquid level < 2 / 5H): actuator two chamber pressure balance, valve core position changes linearly with pneumatic signal, ideal liquid level 1 / 3H, valve opening degree stabilizes at 30%-50%, maintaining the original heater liquid level stable; Receive "valve opening signal" (liquid level ≥ 2 / 5H): actuator "valve opening chamber" intake, push rod drives the valve core to move up, the valve is fully open (opening degree 100%), quickly discharging excess condensate in the original heater; State identification design: actuator push rod side marks opening degree scale line (0%-100%), combined with the pointer fixed on the valve body, the real-time opening degree of the valve can be directly observed, replacing the traditional valve position indicator function.

[0037] The execution adjustment module also includes a manual emergency mechanism: a manual operation hand wheel (316L stainless steel material) is arranged at the top of the actuator, which is connected with the push rod through worm and gear transmission; when the gas supply is interrupted, the hand wheel can directly adjust the opening degree of the valve core (0%-100%), with an adjustment accuracy of ±2%, without affecting the emergency operation of the shell and tube heater 1; A static grounding terminal is arranged beside the hand wheel, which is connected with the shell of the shell and tube heater 1 through a copper core wire with a cross-sectional area of ≥2.5 mm² (grounding resistance ≤4Ω), avoiding static electricity accumulation caused by condensate flow, without the need for additional independent grounding device.

[0038] The use method of the added liquid level controller of the shell and tube heater of the ship of the embodiment 1 includes the following contents: S1, controller positioning and fixing: The controller is moved to the side of the shell and tube heater, the universal wheel is locked, and the shell side spare flange of the shell and tube heater and the condensate outlet pipeline flange are aligned; S2, mechanical liquid level detection module docking: The connecting flange on the vertical guide sleeve of the mechanical liquid level detection module is sealingly connected with the mounting flange on the shell and tube heater, the connecting rod is adjusted to align the position of the floating ball with the cam scale, and the movement of the floating ball is observed through the transparent glass section; S3, execution adjustment module docking: The ZJHP pneumatic single seat regulating valve of the execution adjustment module is connected with the condensate outlet pipeline flange of the shell and tube heater; the hand wheel grounding terminal is connected with the shell of the shell and tube heater, and the grounding resistance is tested; S4, gas path and manual mechanism inspection: Connect the controller gas circuit, install pressure gauge to monitor gas source pressure, test gas circuit air tightness and smoothness of manual operation hand wheel; S5, threshold calibration: Inject hot water to simulate condensate, calibrate liquid level threshold and adjust valve opening; S6, safety and function check: Test explosion-proof performance and adjust valve leakage, start shell and tube heater to verify control effect, no cutting and welding of original shell and tube heater throughout the process.

[0039] Example 2: Pneumatic feedback control type; Referring to Figures 4-6 , Figure 4 Draw the structure diagram of the installed liquid level controller of this embodiment 2. As shown in the figure, the installed liquid level controller of a ship shell and tube heater of this embodiment 2 is different from that of embodiment 1 in that: The floating ball detection assembly 2 of the mechanical liquid level detection module includes a floating ball 2.1, a vertical guide sleeve 2.2, a floating ball hinge 2.3, a flow-through hole 2.4, a connecting flange 2.5, a displacer arm 2.6, and a blowdown plug 2.7. The structure of the floating ball 2.1 and the vertical guide sleeve 2.2 is the same as that of embodiment 1, except that the floating ball 2.1 is connected to one end of the displacer arm 2.6 through the floating ball hinge 2.3, the other end of the displacer arm 2.6 is connected to the controller 3, the floating ball hinge 2.3 is arranged in the vertical guide sleeve 2.2, and the top of the vertical guide sleeve 2.2 is provided with a transverse branch pipe connected to the controller 4, and the transverse branch pipe is provided with the displacer arm 2.6.

[0040] The bottom of the vertical guide sleeve 2.2 is provided with the blowdown plug 2.7.

[0041] The pneumatic control module includes a pneumatic positioner 5, a pneumatic controller A 6, a pneumatic controller B 7, a pneumatic amplifier A 8, a pneumatic amplifier B 9, and a bellows 10. The pneumatic controller A 6 includes an eccentric cam A 6.1, a roller A 6.2, a feedback pendulum rod A 6.3, a lever A 6.4, and a baffle A 6.5. The pneumatic controller B 7 includes an eccentric cam B 7.1, a roller B 7.2, a feedback pendulum rod B 7.3, a lever B 7.4, and a baffle B 7.5. The center axis of the eccentric cam A 6.1 is connected to one end of the feedback pendulum rod A 6.3, the other end of the feedback pendulum rod A 6.3 is connected to one end of the displacer arm 2.6, the outer edge of the eccentric cam A 6.1 is provided with a sliding matching roller A 6.2, the roller A 6.2 is arranged on the lever A 6.4, the bottom of the lever A 6.4 is provided with the baffle A 6.5, one side of the baffle A 6.5 is provided with the pneumatic amplifier A 8, the nozzle A 8.1 of the pneumatic amplifier A 8 is aligned with the baffle A 6.5, and the pneumatic amplifier A 8 is also provided with a balance orifice A 8.2; The output of the pneumatic amplifier A8 is connected to one end of the bellows 10, the other end of the bellows 10 is welded on the top of the lever C7.6, the bottom of the lever C7.6 is connected to the lever B7.4, the lower part of the lever C7.6 is connected to the baffle B7.5, the other side of the baffle B7.5 relative to the lever B7.4 is provided with a pneumatic amplifier B9, the nozzle B9.1 of the pneumatic amplifier B9 is aligned with the baffle B7.5, the pneumatic amplifier B9 is also provided with a balance throttle hole B9.2, the pneumatic amplifier B9 is connected to the ZJHP pneumatic single seat regulating valve 4, and the driving air driving valve is opened; The lever B7.4 is provided with a roller B7.2 which is slidingly arranged on the outer edge of the eccentric cam B7.1, the center shaft of the eccentric cam B7.1 is connected to one end of the feedback swing rod B7.3, and the other end of the feedback swing rod B7.3 is connected to the valve core of the ZJHP pneumatic single seat regulating valve 4; the ZJHP pneumatic single seat regulating valve 4 is also connected to the pneumatic positioner 5.

[0042] The pneumatic positioner 5 is connected to the controller 3, and the ZJHP pneumatic single seat regulating valve 4 is connected to the condensate outlet pipeline of the shell and tube heater 1.

[0043] Control logic: 1. When the liquid level rises or falls, the control feedback swing rod A moves; 2. The feedback swing rod A is fixed on the center shaft of the eccentric cam A, and the up-down displacement is converted into the rotation of the cam center shaft; 3. The rotation of the center shaft is converted into the rotation of the eccentric cam, and the displacement of the baffle A is changed; 4. By adjusting the displacement of the baffle A, the distance between the nozzle A is adjusted, so as to adjust the pressure of the control gas between 0.1bar and 0.2bar; 5. The 0.1-0.2bar control gas is fed back to the pneumatic positioner; 6. The 0.1-0.2bar control air controls the displacement of the bellows; 7. The bellows is welded on one end of the lever C, the length displacement occurs due to the expansion and contraction of the gas in the bellows, and the distance between the nozzle B of the driving gas and the baffle B is adjusted through the lever C; 8. The distance between the nozzle B and the driving gas changes, the output driving air pressure changes, and the ZJHP pneumatic single seat regulating valve starts to adjust up and down; 9. The up-down adjustment of the ZJHP pneumatic single seat regulating valve drives the displacement of the feedback swing rod B, so as to drive the rotation of the eccentric cam B, the rotation of the eccentric cam B drives the displacement of the lever B, so as to drive the displacement of the baffle B; 10. The distance between the baffle B and the nozzle B is corrected to drive the air, so that the valve position is adjusted to the desired position.

[0044] Example 3: electrically controlled pneumatic type; Referring to Figure 7 , Figure 7 A schematic diagram of the principle of the add-on liquid level controller of this embodiment 2 is drawn. As shown in the figure, the add-on liquid level controller of a shell-and-tube heater of this embodiment 3 is different from that of embodiment 2 in that: The controller 3 is controlled by a 4-20 mA circuit, the ZJHP pneumatic single-seat regulating valve 4 is connected to the controller 3 by a 4-20 mA circuit to realize the conversion of electric signals and pneumatic signals, and the ZJHP pneumatic single-seat regulating valve 4 is connected to the pipeline of the condensate outlet 1.3 of the shell-and-tube heater 1.

[0045] The following are the relevant data of a specific implementation case: Take an 8000KW shell-and-tube washing water heater of a certain brand as an example (the original heater has a total height H of the shell side liquid level of 500mm, a spare flange specification of DN50 PN1.6MPa, and a condensate pipeline specification of DN40 PN1.6MPa): Controller parameters: floating ball diameter 150mm, guide sleeve containing transparent borosilicate glass section, ZJHP regulating valve nominal diameter DN40, air supply pressure 0.4MPa. See the following table for details:

[0046] Add-on and debugging steps (completed within 8 hours of the original heater shutdown): positioning the controller, interfacing the flanges, connecting the air circuit, calibrating the threshold, and verifying the function. The specific steps include the following: 1. Controller positioning and fixing: push the controller with universal wheels to the side of the original heater, align the spare flange at the top of the shell side of the original heater with the condensate outlet pipeline flange, lock the shell brake, and ensure that the center line deviation of the interfacing flanges is ≤5mm; 2. Mechanical liquid level detection module interfacing: align the top flange of the guide sleeve with the spare flange of the original heater, seal with graphite gasket, and fasten with bolts (torque 40-50N・m); the floating ball is nested in the guide sleeve, and the movement of the floating ball is observed through the transparent glass section; the connecting rod passes through the flange and is fixed to the external cam, and the length of the connecting rod is adjusted so that the lowest position (bottom end of the guide sleeve) of the floating ball corresponds to the "0" scale of the cam, and the highest position corresponds to the "200mm (2 / 5H)" scale; 3. Execute the regulating module interfacing: cut off the condensate outlet pipeline valve of the original heater, remove the short section between the original pipeline flanges, align the flanges at both ends of the ZJHP pneumatic single-seat regulating valve with the original pipeline flanges (note that the fluid flow direction should be consistent with the arrow on the valve body), seal with fluororubber gasket, and fasten with bolts (torque 50-60N・m); connect the handwheel grounding terminal to the original heater shell through a copper core wire, and test the grounding resistance ≤4Ω; 4. Air path and manual mechanism inspection: connect the marine compressed air main pipe to the air filter pressure reducing valve inlet through the explosion-proof hose (material PTFE, resistant to 120 DEG C), install the explosion-proof pressure gauge to monitor the air source pressure (stable 0.4MPa); the output of the pneumatic amplifier is connected to the open valve cavity and the close valve cavity of the regulating valve actuator through the hose; rotate the manual operation hand wheel, observe the push rod scale line, and confirm that the valve core is smooth (no jam) from 0% to 100% opening degree; air path air tightness test (pressure 0.6MPa, pressure holding for 30 minutes, pressure drop less than or equal to 0.02MPa); 5. Threshold calibration: inject 80 DEG C hot water into the original heater shell side to simulate condensate water, observe the position of the floating ball through the transparent section of the guide sleeve, slowly raise the liquid level to 0 (the lowest position of the floating ball), 167mm (1 / 3H), 200mm (2 / 5H), and record the cam pointer position and the regulating valve push rod scale respectively: When the liquid level is 0: the cam pointer is aligned with the "0" scale, and the regulating valve push rod scale shows 0% (fully closed); When the liquid level is 167mm: the cam pointer is aligned with the "1 / 3H" scale, and the regulating valve push rod scale shows 40%±1%; When the liquid level is 200mm: the cam pointer is aligned with the "2 / 5H" scale, and the regulating valve push rod scale shows 100% (fully open); If the deviation exceeds ±5%, correct it by adjusting the cam fixed position or the gain knob of the pneumatic amplifier without changing the original heater; 6. Safety and function inspection: test the explosion-proof housing explosion-proof surface gap (less than or equal to 0.15mm), the leakage of the regulating valve (0.6MPa compressed air is introduced, and the leakage is less than or equal to 0.1L / h when fully closed); start the original heater, observe the liquid level stability through the transparent section of the guide sleeve, verify the outlet temperature of the washing water (stable 80±1.2 DEG C), and confirm that there is no leakage.

[0047] Running effect: the liquid level control precision is 167±6mm, the steam consumption is reduced by 23%, and the outlet temperature of the washing water is stable at 80±1.2 DEG C. After the installation, the specific parameters of the real ship running verification (50,000-ton oil tanker, original 8000KW washing water heater, ATEX Zone 1 dangerous area) are as follows:

[0048] Working principle: The application discloses a kind of liquid level controller of ship shell pipe heater and its use method, and the liquid level controller includes mechanical liquid level detection module, pneumatic control module and execution adjustment module.

[0049] Mechanical liquid level detection module: scheme one, the float ball floats with the liquid level, and the cam is driven to rotate through the connecting rod, and the cam profile is designed according to the liquid level threshold (0, 1 / 3H, 2 / 5H); scheme two, the liquid level detection module includes a float ball hinge and a displacer arm, the float ball is connected with the displacer arm through the hinge, and the other end of the displacer arm is connected with a controller.

[0050] Pneumatic control module: scheme one, including a mechanical pilot valve, a pneumatic amplifier and a gas path pretreatment assembly. The pilot valve outputs a pneumatic signal according to the cam position, and drives the actuator after amplification by the amplifier; scheme two, the pneumatic control module includes a pneumatic positioner, a pneumatic controller A, a pneumatic controller B, a pneumatic amplifier A, a pneumatic amplifier B and a bellows. Through multi-stage pneumatic feedback of eccentric cam, lever and baffle, the opening of ZJHP regulating valve is accurately controlled.

[0051] Execution adjustment module: the core is a ZJHP pneumatic single-seat regulating valve, which is added to the original heater condensate outlet pipeline through a standardized flange, and linearly adjusts the condensate discharge according to the pneumatic signal.

[0052] The controller of the present application is an independent modular structure, which is connected with the original heater through a standardized flange, has no electrical elements, is driven only by compressed air, and realizes accurate control of the condensate level. The present application solves the problem of liquid level control in dangerous areas, improves heating efficiency and energy recovery, and is suitable for safety and energy-saving modification of marine shell-and-tube heaters. The present application has the following advantages: (1) no modification and installation, strong compatibility: the controller is connected with the standby flange of the original heater and the condensate pipeline flange through a standardized flange, the DN25-DN50 diameter of the ZJHP pneumatic single-seat regulating valve is suitable for the main condensate pipeline specifications, the original equipment does not need to be cut and welded, the installation period is shortened to 8 hours (the original integrated modification needs 3-5 days), the structural integrity and sealing of the original heater are not damaged, and it is suitable for the mainstream 8000KW shell-and-tube heater on the market; (2) intrinsically safe, suitable for dangerous areas: the controller has no electrical elements, the ZJHP regulating valve and the pneumatic elements are certified by ATEX II 2G Ex d IIB T4 Ga and IECEx Zone 1 for explosion prevention, the grounding terminal of the actuator is reliably connected with the original heater (grounding resistance ≤4Ω), no electrical spark and static risk is introduced after installation, the safety specification of the ship dangerous area is met, and the explosion-proof grade of the original heater is not changed; (3) Precise liquid level control, suitable for high pressure difference condensate working condition: The linear flow characteristics of ZJHP pneumatic single seat control valve and the high-precision valve core design, combined with the mechanical control of cam-pilot valve, make the original heater liquid level stable at 1 / 3H±8mm, which is better than the control accuracy of butterfly valve ±10mm; The single seat sleeve structure resists high pressure difference condensate scouring (allowable pressure difference 0.8MPa), avoiding the adjustment failure caused by valve core wear, reducing steam consumption by 20%-22%, saving fuel 120-180 tons per year, and stabilizing the outlet temperature of washing water at 80±1.5℃; (4) Core function integration, no redundant parts: Through the transparent section of the guide sleeve, the liquid level is observed, the cam scale line identifies the liquid level threshold, the push rod scale line displays the valve position, and the pressure monitoring interface is provided on the pressure reducing valve, which still guarantees the system observability and maintainability after canceling the independent safety auxiliary module, the structure is more simple, the manufacturing cost is reduced by 15%, and the installation occupation of the narrow space of the ship is also reduced; (5) High reliability and easy maintenance: The corrugated pipe seal and hard alloy valve seat design of ZJHP control valve can work for more than 9000 hours (better than 8000 hours of butterfly valve) in the ship's rolling (amplitude ≤10g), high temperature (120℃) and high pressure difference condensate environment; The components are designed in a modular manner, the valve core and diaphragm can be replaced individually, the manual emergency hand wheel ensures that the original heater can still operate when the controller fails, and the maintenance cost is reduced by 70%; (6) Energy saving and waste heat recovery: The ideal liquid level of 1 / 3H ensures that the high-temperature condensate (80-120℃) in the original heater and the imported medium (20℃ washing water) form counterflow heat exchange, the preheating temperature is increased to 38-42℃, the condensate sensible heat recovery efficiency is more than 85%, the steam heating load of the original heater is reduced, and the energy saving upgrade of the original equipment is realized; (7) Strong compliance: It meets the requirements of IMO SOLAS Convention Chapter II-2, MARPOL Annex VI and DNV GL / ABS ship classification society certification, the ZJHP control valve is made of non-heavy metal pollution material, and the original heater still meets the ship classification society inspection standard after installation, which is suitable for ship environmental protection requirements.

[0053] The above is only a specific application example of the present application, which does not constitute any limitation on the protection scope of the present application. Any technical solution formed by equivalent transformation or equivalent replacement falls within the scope of the present application.

Claims

1. A retrofittable liquid level controller for a marine shell and tube heater, characterized by: It comprises a mechanical liquid level detection module, a pneumatic control module and an execution adjustment module, which are integrated in the same movable explosion-proof shell, and are connected with the existing shell-and-tube heater through a standardized interface; The shell-and-tube heater is internally provided with a plurality of heating tubes, and is provided with two through holes on the side surface for being connected with the add-on liquid level controller, and is provided with a mounting flange at the through holes, and is provided with a condensate outlet at the bottom; The mechanical liquid level detection module comprises a floating ball detection assembly, which is connected with the shell-and-tube heater through a standardized flange; the floating ball detection assembly comprises a floating ball and a vertical guide sleeve, and the floating ball is arranged in the vertical guide sleeve; two flow holes are formed in the side wall of the vertical guide sleeve; The pneumatic control module is installed in the explosion-proof shell, and converts the mechanical displacement signal into a pneumatic signal that can drive the execution mechanism; The execution adjustment module is added to the pipeline of the condensate outlet of the shell-and-tube heater through a standardized flange, without changing the original pipeline direction, and the execution adjustment module comprises a ZJHP pneumatic single-seat regulating valve, which adjusts the condensate discharge amount to control the liquid level through the ZJHP pneumatic single-seat regulating valve; The ZJHP pneumatic single-seat regulating valve comprises a valve body structure, a sealing design and an execution mechanism; The valve body structure of the ZJHP pneumatic single-seat regulating valve adopts a stainless steel valve body, and the valve core of the ZJHP pneumatic single-seat regulating valve is a V-shaped opening or a parabolic type, and the flow characteristic is linear, which is suitable for linear control requirements of the liquid level; The two ends of the valve body of the ZJHP pneumatic single-seat regulating valve are provided with standardized flanges, which are consistent with the flange specifications of the condensate outlet pipeline of the shell-and-tube heater, and are sealed and connected with the condensate outlet pipeline through 120 DEG C-resistant fluorine rubber gaskets; The control logic of the ZJHP pneumatic single-seat regulating valve is as follows: When the liquid level is less than or equal to 0, a valve closing signal is received: the execution mechanism of the ZJHP pneumatic single-seat regulating valve is supplied with air in the valve closing cavity, the push rod drives the valve core to move downward, the valve is fully closed, the opening degree is 0%, the condensate discharge of the original heater is blocked, and the steam is prevented from entering the pipeline; When the liquid level is greater than 0 and less than 2 / 5H, a position maintaining signal is received: the execution mechanism of the ZJHP pneumatic single-seat regulating valve is balanced in pressure in the two cavities, the position of the valve core changes linearly with the pneumatic signal, when the ideal liquid level is 1 / 3H, the opening degree of the valve is stabilized at 30%-50%, and the liquid level in the original heater is maintained stable; When the liquid level is greater than or equal to 2 / 5H, an opening signal is received: the execution mechanism of the ZJHP pneumatic single-seat regulating valve is supplied with air in the valve opening cavity, the push rod drives the valve core to move upward, the valve is fully opened, the opening degree is 100%, and the excess condensate in the original heater is quickly discharged.

2. A retrofittable liquid level controller for a marine shell and tube heater according to claim 1, characterized in that: The connection flange is arranged at the flow hole, and is sealed and connected with the mounting flange on the side wall of the shell-and-tube heater through a 120 DEG C-resistant graphite gasket, without welding; the bottom end of the vertical guide sleeve extends to the bottom of the shell side of the shell-and-tube heater by 100mm, and stainless steel limit blocks are arranged at the upper and lower ends of the vertical guide sleeve to limit the stroke of the floating ball, corresponding to the liquid level of 0 to 2 / 5H, and being adapted to the height of the shell side of the shell-and-tube heater.

3. A retrofittable liquid level controller for a marine shell and tube heater according to claim 2, characterised in that: The mechanical liquid level detection module further comprises a connecting rod-cam transmission assembly, in which a rigid stainless steel connecting rod is welded to the top of the float ball, the top end of the connecting rod is fixedly connected with an external mechanical cam through a flange of a vertical guide sleeve, and the center of the mechanical cam is rotationally connected with the explosion-proof shell through a stainless steel rotating shaft, and deep groove ball bearings are arranged at both ends of the rotating shaft; The profile of the mechanical cam is designed according to the liquid level threshold of the shell-and-tube heater; When the liquid level is 0, i.e. there is no condensate in the shell side of the shell-and-tube heater, the float ball is lowered to the lowest position, the cam flange is at the lowest position, and a subsequent “valve closing signal” is triggered; When the liquid level is 1 / 3H, i.e. the shell-and-tube heater is at an ideal liquid level, the float ball is raised to the middle position, the cam flange is at the gentle section, and a “liquid level maintaining signal” is output; When the liquid level is 2 / 5H, i.e. the shell-and-tube heater is at a high liquid level threshold, the float ball is raised to the highest position, the cam flange is at the highest position, and a “valve opening signal” is triggered; The edges of the mechanical cam are marked with liquid level scale lines: 0, 1 / 3H, and 2 / 5H, which are matched with a pointer and fixed to the explosion-proof shell, so that the corresponding liquid level state of the cam can be directly observed, and it is determined whether the detection module is working normally.

4. A retrofittable liquid level controller for a marine shell and tube heater as claimed in claim 3, wherein: The pneumatic control module comprises a mechanical pilot valve, a pneumatic amplifier and a gas path pretreatment assembly; The mechanical pilot valve is an explosion-proof two-position three-way slide valve, one end of the valve rod of the mechanical pilot valve is tightly fitted with the profile of the mechanical cam through a compression spring, and the other end is connected with a valve core in the valve body; when the mechanical cam rotates, the valve rod of the mechanical pilot valve moves up and down along the profile of the mechanical cam, and switches the gas path channel; When the liquid level is ≤0, i.e. the cam is at a low position, the valve rod moves downward, the mechanical pilot valve is connected with the “valve closing gas path”, and 0.4MPa compressed air is output; When the liquid level is 0<liquid level<2 / 5H, i.e. the cam is at a middle position, the valve rod is at an intermediate position, the pilot valve is connected with the “liquid level maintaining gas path”, and 0.2-0.3MPa compressed air is output; When the liquid level is ≥2 / 5H, i.e. the cam is at a high position, the valve rod moves upward, the pilot valve is connected with the “valve opening gas path”, and 0.4MPa compressed air is output; The pneumatic amplifier is an explosion-proof amplifier, the input port is connected with the output port of the pilot valve, and the output port is connected with an execution adjustment module; the small flow signal output by the mechanical pilot valve is amplified to ≥1m³ / h, so as to ensure that the response time of the execution mechanism is <0.8 seconds, and the liquid level in the shell-and-tube heater 1 is prevented from being continuously out of control; The gas path pretreatment assembly comprises an air filter pressure reducing valve, an oil mist separator and a micro gas storage tank; the gas path is sequentially connected with the air filter pressure reducing valve, the oil mist separator, the gas storage tank and the mechanical pilot valve, and is independent of the gas source system of the shell-and-tube heater; the air filter pressure reducing valve is provided with a pressure gauge interface, so that the gas source pressure can be directly monitored without the need for additional pressure monitoring components.

5. A retrofittable liquid level controller for a marine shell and tube heater according to claim 1, characterized in that: The ZJHP pneumatic single seat regulating valve has a nominal diameter DN25-DN50, is suitable for 8000KW heater 37.5t / h maximum condensate discharge capacity, the valve seat is made of hard alloy surfacing and is resistant to erosion and corrosion, the sealing design of the ZJHP pneumatic single seat regulating valve adopts a double sealing structure of soft sealing and hard sealing, the upper valve cover of the ZJHP pneumatic single seat regulating valve adopts bellows sealing, and the valve core and the valve seat sealing surface of the ZJHP pneumatic single seat regulating valve are combined by fluorine rubber and hard alloy.

6. A retrofittable liquid level controller for a marine shell and tube heater according to claim 1, characterized in that: The floating ball detection assembly of the mechanical liquid level detection module comprises a floating ball, a vertical guide sleeve, a floating ball hinge, a flow-through hole, a connecting flange, a displacer arm and a drain plug, the floating ball is connected with one end of the displacer arm through the floating ball hinge, the other end of the displacer arm is connected with a controller, the floating ball hinge is arranged in the vertical guide sleeve, a top of the vertical guide sleeve is provided with a transverse branch pipe connected to the controller, and the transverse branch pipe is provided with the displacer arm; a bottom of the vertical guide sleeve is provided with the drain plug.

7. A retrofittable liquid level controller for a marine shell and tube heater according to claim 6, characterised in that: The pneumatic control module comprises a pneumatic positioner, a pneumatic controller A, a pneumatic controller B, a pneumatic amplifier A, a pneumatic amplifier B and a bellows; the pneumatic controller A comprises an eccentric cam A, a roller A, a feedback swing rod A, a lever A and a baffle A, the pneumatic controller B comprises an eccentric cam B, a roller B, a feedback swing rod B, a lever B and a baffle B; a central shaft of the eccentric cam A is connected with one end of the feedback swing rod A, the other end of the feedback swing rod A is connected with one end of the displacer arm, a cam outer edge of the eccentric cam A is provided with the sliding matching roller A, the roller A is arranged on the lever A, the bottom of the lever A is provided with the baffle A, one side of the baffle A is provided with the pneumatic amplifier A, a nozzle A of the pneumatic amplifier A is aligned with the baffle A, and the pneumatic amplifier A is further provided with a balance throttle hole A; an output port of the pneumatic amplifier A is connected to one end of the bellows, the other end of the bellows is welded to a top of a lever C, the bottom of the lever C is connected with the lever B, the lever C is connected with the baffle B below, the baffle B is provided with the pneumatic amplifier B on the other side of the lever B, a nozzle B of the pneumatic amplifier B is aligned with the baffle B, the pneumatic amplifier B is further provided with a balance throttle hole B, and the pneumatic amplifier B is connected to the ZJHP pneumatic single seat regulating valve to drive the air-driven valve to open; the lever B is provided with the roller B, the roller B is slidingly arranged on an outer edge of the eccentric cam B, a central shaft of the eccentric cam B is connected with one end of the feedback swing rod B, and the other end of the feedback swing rod B is connected with the valve core of the ZJHP pneumatic single seat regulating valve; the ZJHP pneumatic single seat regulating valve is further connected with the pneumatic positioner; the pneumatic positioner is connected with the controller, and the ZJHP pneumatic single seat regulating valve is connected to a condensate outlet pipeline of the shell-and-tube heater.

8. A retrofittable liquid level controller for a marine shell and tube heater according to claim 6, characterized in that: The controller is controlled through a 4-20mA circuit, the ZJHP pneumatic single seat regulating valve is connected to the controller through a 4-20mA circuit to realize conversion between electric signals and pneumatic signals, and the ZJHP pneumatic single seat regulating valve is connected to a pipeline of a condensate outlet of the shell-and-tube heater.

9. A retrofittable liquid level controller for a marine shell and tube heater according to claim 1, characterized in that: The execution adjustment module further comprises a manual emergency mechanism: a manually operated hand wheel is arranged on the top of the execution mechanism and connected with the push rod through a worm and worm gear transmission; when the air source is interrupted, the hand wheel can be directly rotated to adjust the opening degree of the valve core, the adjustment accuracy is ± 2%, and the emergency operation of the shell and tube heater is not affected; a static grounding terminal is arranged beside the hand wheel and connected with the shell of the shell and tube heater through a copper core wire with a cross-sectional area of ≥2.5mm², the grounding resistance is ≤4Ω, the static electricity accumulation caused by the flow of condensed water is avoided, and an independent grounding device does not need to be additionally arranged.

10. A method of using a retrofit liquid level controller for a marine shell and tube heater according to any one of claims 1 to 9, wherein, The following contents are included: S1, controller positioning and fixing: The controller is pushed to the side of the shell and tube heater and locked, and is aligned with the shell side spare flange of the shell and tube heater and the condensed water outlet pipeline flange; S2, mechanical liquid level detection module docking: The connecting flange on the vertical guide sleeve of the mechanical liquid level detection module is sealingly connected with the mounting flange on the shell and tube heater, and the connecting rod is adjusted so that the position of the floating ball is aligned with the cam scale; S3, execution adjustment module docking: The ZJHP pneumatic single-seat regulating valve of the execution adjustment module is connected with the condensed water outlet pipeline flange of the shell and tube heater; S4, connecting air path: The controller air path is connected, a pressure gauge is installed to monitor the air source pressure, and the air tightness of the test air path is tested; S5, threshold calibration: Hot water is injected to simulate condensed water, and the liquid level threshold and the opening degree of the regulating valve are calibrated; S6, safety and function check: The explosion-proof performance and the leakage amount of the regulating valve are tested, and the shell and tube heater is started to verify the control effect.

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