RU2073526C1 - Sterilizer - Google Patents

Abstract

FIELD: pharmaceutical practice. SUBSTANCE: sterilizer affords sterilization with steam in three sterilization modes by providing element pneumatic distributors which can be arranged so as to form unitized-modular sterilization circuits. Said three sterilization modes are intended for sterilization of, respectively, solutions of medicinal preparations, medical articles and vials for drugs. EFFECT: use is possible both under stationary and field conditions. 2 cl, 1 dwg

Description

 The invention relates to the field of medical equipment, in particular to the design of a horizontal steam sterilizer, and can be used to sterilize solutions of drugs, glass vials, closures and medical devices (surgical instruments, syringes, injection needles, surgical gloves, dressings and surgical material , medical linen, etc.) in stationary and field conditions.

Known sterilizer-autoclave AG-1 medical sterilization-distillation unit SDP-2 mounted on a single axle trailer TAPZ-755 [1]
The closest in technical essence to the claimed device is a serial horizontal steam sterilizer GK-75 selected as a prototype, which currently serves as one of the main units of sterilization-distillation units (CDS) of the field pharmaceutical laboratories of the medical service of the Armed Forces of the Russian Federation [2]
The GK-75 sterilizer is designed for a working vapor pressure in the chamber of 0.20 MPa (2 kgf / cm ² ), which has internal dimensions: diameter 400 ± 4 mm, depth 670 mm ± 5 mm. Three sterilization boxes of the size (390x190) mm are simultaneously loaded into the chamber of the sterilizer GK-75 (AG-1). The mass of the sterilizer is 90 kg (the capacity of the steam chamber of the AG-1 autoclave is 86 l, weight 87 kg). The CDS, which includes three GK-75 sterilizers, is mounted on a two-axle trailer SMZ-8326.

 The main disadvantages of the prototype are low productivity, due to the small volume of the sterilization chamber, low functionality due to the lack of versatility of sterilization (the impossibility of various sterilization modes), the complexity of maintenance and operation of the sterilizer, insufficient metrological support, uneven temperature distribution in different zones of the chamber volume, and also low resistance to disinfection of the sterilizer itself. Moreover, the GK-75 sterilizer (prototype) does not provide the sterilization effect in the whole mass of the sterilization material in the established sterilization periods in the field due to low vapor pressure, accumulation of condensate in the chamber, capture of part of the water with steam and humidification of the sterilization material.

 The aim of the invention is to increase the operational reliability of the sterilizer in the field and stationary conditions.

 The object of the invention is achieved in that the sterilizer is equipped with a group of pneumatic distributors located in the air control network, the output of the first of which is connected to the oil distributor, the output of the second pneumatic distributor is connected to the chamber door lock lock, the output of the third pneumatic distributor is connected to the pneumatic actuator of the first and shut-off valve of the vacuum line to which a third sensor relay and a vacuum two-stage liquid ring pump are connected, in a sealed chamber door under the gasket to connect the output of the fourth pneumatic distributor to it, the output of the fifth pneumatic distributor is connected to the pneumatic actuator of the sixth shut-off valve for supplying water to the water-cooling shirts, the output of the sixth pneumatic distributor is connected to the pneumatic actuator of the second shut-off valve for exhausting the vapor-air mixture from the chamber through the condensate tank, the output of the seventh pneumatic distributor is connected to the pneumatic the valve for exhausting air from the chamber, the output of the eighth air distributor is connected to the pneumatic actuator of the fourth the steam inlet shutoff valve and the pneumatic actuator of the fifth steam inlet shutoff valve, the output of the ninth pneumatic distributor is connected to the pneumatic actuator of the ninth pressure balancing shutoff valve in the chamber, the output of the tenth pneumatic distributor is connected to the pneumatic actuator of the seventh shutoff valve for filling the condensate of the tank for process media, the output of the eleventh pneumatic distributor is connected to the eight a valve connected through a check valve to the chamber on one side and connected through a second filter with the first sensor-relay and the compressed air system on the other hand, while the working inputs of all pneumatic valves are connected to the compressed air system, and their switching inputs are connected by electric wires to the push buttons of the control panel, the steam supply network is equipped with a gearbox for receiving steam under pressure, the water-cooling chambers of the chamber are formed by stiffening ribs and are equipped with blades built into the latter for film irrigation of the walls of the sterilization chamber, the latter is equipped with a slide and mobile th sterilization container having a guide for the slide, wherein the sealed door of the sterilization chamber is equipped with a locking device, the sealed door lock assembly is provided with a clamp latch and the sterilization chamber and its door reinforced and lined mullitokremnezemnistym roll thermally insulating material, and automatic control of the sterilizer duplicated manual control. The inventive sterilizer differs from the prototype in that it is a block-modular design and is equipped with portable packaging containers for transporting block modules in them, and the frame is made in the form of a welded carbon steel frame for fixing the main components and mechanisms in it.

 The drawing shows a functional block diagram of a sterilizer (medical steam).

 The sterilizer contains a sterilization chamber 1 with water-cooling jackets in the form of stiffeners, equipped with a door 2 with a cylindrical pneumatic actuator 3, a locking device 4 and a fixing unit 5 of the door 2, including guide rollers 6 and a latch-latch 7. The sterilizer also contains a container 8 for process media, condensate collecting tank 9, oil distributor 10, first 11 and second 12 filters, safety 13 and check valves 14, control unit 15, vacuum pump 16 with condenser 17, shut-off valves 18 with pneumatic actuators 19, pneumatic distributors 20, upper 21 and lower 22 level sensors, sensors-relays 23, control and measuring devices, including six pressure gauges 24, electric contact and pressure gauges 25 type MVPZ-U, network of process pipelines 26, power supply networks 27 and control 28. All components and mechanisms the sterilizer is installed and fixed on the frame 29, made in the form of a welded frame made of carbon steel.

 Decorative panels 30, with which the sterilizer is lined on the outside, and doors 2, which are also attached to the welded frame, are made of stainless steel. The chamber 1 and its door 2 are reinforced and lined with mullite-siliceous roll of heat-insulating material 31. The door 2 of the chamber 1 is equipped with a blocking device 4 for automatically stopping the lifting of the door 2 when an obstacle 32 appears in the opening of the chamber 1. The chamber 1 is equipped with a slide 33 for moving the sterilizing container-cartridge 34 , which is equipped with guides 35, consistent with the slides 33 of the sterilization chamber 1, and the sterilizer itself is equipped with a reducer 36 for receiving steam under a pressure of 0.4 MPa and is made in the form of block-modular constructions 37, transported in separate packages 38 and mounted on-site in a mobile field pharmacy or mobile pharmaceutical laboratory.

 The control unit 15 is connected to the control panel 39 and contains a pulse counter 40, control microcircuits 41, starters 42, travel 43 and push-button 44 switches, signal armature 45 and bell 46. The sterilization chamber 1 has a rectangular body and water-cooling shirts 47 in the form of ribs stiffness, in which the blades 48 for film irrigation of the walls of the chamber 1 are integrated, is equipped with fittings for supplying and discharging process media, as well as fittings for connecting pipelines of instrumentation. The chamber 1 is also made of stainless steel.

 Elements of the sterilizer 29 35, 37 38 because of less importance in the drawing are not indicated.

The sterilizer works as follows. For normal operation of the sterilizer installed in the K-4310 box body of a KAMAZ field pharmacy, you must have:
a network with a condensate supply with a constant pressure of 0.3 0.4 MPa;
water supply with a constant water pressure of 0.4 MPa (4.0 kgf / cm ² );
a network with a supply of saturated water vapor with a pressure of 0.3 MPa (3.0 kgf / cm ² );
electric network;
sewage system;
a network with air supply with a constant pressure of 0.6 MPa (6 kgf / cm ² );
during operation, the sterilizer can be in one of three states (depending on the position of the field pharmacy): storage, transportation, working condition. In all three states, the sterilizer is connected to all energy systems that ensure its operation (water supply, steam pipe, vacuum line, air pipe, sewer, mains).

The operational reliability of the sterilizer is increased by increasing its versatility by introducing three sterilization modes: solutions of medicines, medical devices and vials for solutions of medicines (PM). Reliability is increased by increasing the sterilizer's performance by increasing the volume (capacity) of the sterilization chamber 1 (160 dm ³ instead of 75 dm ³ ), reducing the time in all three modes, evenly distributing the temperatures in the chamber 1 volume, receiving steam at the inlet of the sterilizer under two times of pressure (not less than 0.4 MPa); by increasing the sterility of the sterilized products due to preliminary sterilization of the bottles, simplifying the methods of keeping the sterilizer clean and reducing the resistance of its surface to disinfection; by increasing efficiency and simplifying the maintenance of the sterilizer due to a significant reduction in the power consumption of its electrical units, automatic and metrological support of all sterilization modes, automatic control duplicated by manual control, with arrow (direct-showing), light and sound indication.

This goal is achieved by the fact that in the sterilizer using water vapor under pressure, sterilize drug solutions in a hermetically sealed glass container (first program sterilization mode), sterilize glass vials and capping material (second sterilization program) and sterilize medical devices (surgical instrument, syringes, injection needles, etc.) the third sterilization program. The parameters of the sterilization regimen for drugs: pressure 0,098 MPa $\genfrac{}{}{0ex}{}{\text{+0.013}}{\text{-0.006}}$ $\genfrac{}{}{0ex}{}{\text{MPa}}{\text{MPa}}$ , temperature 120 ^o ± 1.0 ^o C, sterilization time up to 15 min; the parameters of the sterilization mode for medical devices: pressure 0.105 MPa ± 0.01 MPa, temperature 121 ^o ± 1.0 ^o C, sterilization time up to 20 ⁺² min; parameters of the vial sterilization mode: pressure 0.21 MPa ± 0.01 MPa, temperature 134 ^o ± 1.0 ^o C, sterilization time 5 ± 1 minute. Sterilization heating time 30 minutes. A method of removing air from a sterilizer is pulsating vacuum pumping, a radar cooling method replacing water vapor with an air-water mixture.

 The work of the sterilizer is carried out in the following sequence: preparation for work, loading the sterilization chamber 1, closing the door 2, passing the sterilization process in automatic mode, depending on the selected sterilization program; opening door 2 and unloading the sterilization chamber 1.

 Preparing for work.

Clean the sterilizer of preservation grease and rinse chamber 1 with hot water. Ground the sterilizer through a bolt with a copper wire with a cross section of at least 16 mm ² , connecting the ground wire with the ground bolt installed in the control unit 15, then connect the actuators of the pneumatic valves and sensors 21, 22, 23 of the chamber 1 to the control unit 15 and connect the electrical consumers to AC power supply. Check the fastening of pneumatic valves 13, 14, 18, pneumatic valves 20, pipe connections and, if necessary, seal the pipelines, while eliminating the leakage of water, condensate, steam, suction and air leakage.

 After that, the sensors-relays 23 and manovacuometers 24 check the availability of power supply to the sterilizer (water, air, steam, etc.) and make a trial (at least one) sterilization without loading chamber 1 in the first program with automatic control, while being monitored sterilization parameters, operation of executive bodies, door gasket 2 and tightness of joints of other parts and assemblies according to the indications of devices. Before starting work, it is required to purge the safety valve 13.

 The operation of the sterilizer.

 Enable introductory machine. On the remote control 39 control, press the button 44 "Door open". The loading of the chamber 1 is carried out using a sterilization container 34 with installed cassettes with bottles of radar. To do this, bring the trolley to the opening of chamber 1 and lock it, roll the container 34 with bottles into the chamber 1 manually from the trolley, aligning the guides 35 with the slides 33 of the chamber 1, and move the container 34 into the open opening of the chamber 1 until it stops; then move the locking knob to the vertical position and roll the trolley. Press the “Close door” button 44 and the compressed air controlled by the pneumatic distributor 20 (PB1) enters the corresponding cavity of the cylindrical pneumatic actuator 3, which moves the door 2 along the guides 6 to its highest position, in which a signal is sent from the limit switch 43 to fix the door 2. The fixation is made by the latch-latch, which enters the socket of the latch located on the door 2 of the chamber 1. The latch 7 moves from the pneumatic actuator 3, controlled by the corresponding pneumatic distributor 20 (PB2). After fixing door 2, it is necessary to open the door of the remote control 39 and put the switch of the type of work into automatic operation when the first sterilization program is selected (button 44 "Automatic" is pressed, valve signal 45 is on).

 Automatic control of the sterilizer.

 After selecting the sterilization program N 1 using the switch on the remote control 39 by pressing the 44 "Start" button, the process of sterilization of drug solutions is started, which proceeds in the following sequence: a) sealing the doorway; b) heating the camera 1; c) mode; d) back pressure (cooling); e) alignment; e) depressurization of the doorway; g) finish.

 For the program N 2 (sterilization of medical devices) and N 3 (sterilization of vials), instead of point d) "Back pressure", the point "Drying" is carried out. The operator observes the sequence of each stage of the sterilization cycle through the light signals of the fittings 45 of the console 39.

 a) Sealing the doorway.

 After pressing the "Start" button, the pneumatic distributor PR 20 (РВ4) is activated and the compressed air enters the groove under the gasket for the door 2 of chamber 1. After the pressure reaches a value of 0.35 MPa, the doorway is sealed and the next stage is "Heating".

 b) Heating.

When heated, periodically removes air and vapor-air mixture from chamber 1, which consists of four pulsations. During the pulsation, the vacuum pump 16 is turned on, which can serve up to three sterilizers simultaneously. To do this, the shut-off valve 18 (Cl. 2) opens using compressed air supplied from the PR 20 (PB 6), and the air-vapor mixture is aspirated from the chamber 1 through the condensate collecting tank 9 and the condenser 17, which is part of the vacuum pump 16. When creating a vacuum of 0.05 MPa (0.5 kgf / cm ² ) in chamber 1, the shut-off valve 18 (Cl. 2) closes, the vacuum pump 16 is turned off and shut-off valves 18-4 (Cl .4) and 18-5 (Cl. 5) on the steam supply line using compressed air supplied from PR 20-8 (RV 8). Steam enters the chamber 1 through a reducer 36, tuned to a pressure of 0.4 MPa; after four pulsations, the pressure in the chamber 1 rises to 0.21 MPa and for 20 minutes the pressure in the chamber 1 is constant until the radar warms up to a temperature of 120 ^o ± 1 ^o C. After that, by the command of ECM 24 on the remote control 39, the light signal of the valve 45 "Mode".

 c) Mode.

The sterilization mode of drug solutions is maintained automatically by means of an 18-3 shut-off valve (Cl. 3). The duration of this phase of the cycle is 15 minutes. The duration of the sterilization regimen for medical devices is 20 ⁺² minutes, and the sterilization of vials is 5 ⁺¹ minutes.

 d) Back pressure (cooling).

The sterilization object is cooled by removing 1 steam from the chamber with its replacement with an air-water mixture. Compressed air from the pneumatic system through the second filter 12, the check valve 14, the shut-off valve 18-8 (Cl. 8) enters the chamber 1 through the nozzle. During its movement through the pipeline 26, it sucks a certain amount of condensate from the tank 8 for process media. Condensate absorption occurs due to the difference in kinetic energies of compressed air and condensate. The opening of valve 18-8 (Cl. 8) is due to the supply of compressed air from PR 20-11 (RV 11). Condensate in the tank 8 comes from the collector by opening the valve 18-7 (Cl. 7) using PR 20-10 (PB 10). When the condensate in the tank 8 reaches its upper level, the signal of the upper level sensor 21 closes the shut-off valve 18-7 (Cl. 7). When the condensate in the tank 8 is reduced to a lower level by the signal of the lower level sensor 22, the valve 18-7 opens and the process of supplying condensate to the tank 8 is repeated. Simultaneously with the air supply to the chamber 1, cooling water through the shut-off valve 18-6 (Cl. 6) is supplied to the jacket of the chamber 1 and discharged into the sewer. Opening and closing the valve 18-6 is performed using a pneumatic distributor PR 20-5 (PB 5). In order to reduce water consumption by reducing the duration of the cooling stage due to film irrigation with a guaranteed film thickness, used to cool the walls of the chamber 1, which allows to increase the heat transfer coefficient from the cooling water to the wall of the sterilization chamber 1. The duration of the cooling stage is determined by the achievement of the temperature in the chamber 1 of the value of 60 ^o ± 5 ^o C, 65 minutes after the stage "Mode". Maintaining the reference pressure in the chamber 1 at this stage is carried out at a constant pressure by opening the shut-off valve 18-3 (Cl. 3) with a pneumatic actuator 19-3 using PR 20-7 (RV 7) at the command of ECM 24. After the end of the “Back pressure” step "the sterilizer automatically proceeds to the next step.

 e) Pressure equalization.

 At this stage, with the shut-off valve 18-3 open, excess air-water mixture is discharged from chamber 1.

 f) Door depressurization 1.

 By turning on the pneumatic valves 20-1, 20-2, 20-3 and starting the vacuum pump 16 when opening the shut-off valve 18-2 (Cl. 2) using PR 20-6, a vacuum is created under the gasket and the gasket is drawn into the groove. The entire radar sterilization cycle is completed. The light signal on armature 45 “Finish” lights up and the audible signal of bell 46 is turned on. After that, press 44 4 “Stop mode” on the remote control 39, then press 44 “Open door”. Bring the trolley to the camera opening, lock the trolley in horizontal position to lock the trolley, roll container 34 with pharmaceutical dishes filled with radar onto the trolley, put the latch handles in a vertical position and roll the trolley back. To re-enable the sterilizer in the work, the above procedure should be repeated. For the sterilizer to work with manual control, repeat the procedure for preparing for work, then open the door of the control panel 39 and put the work switch in the "manual" position (the button is pressed, the signal is on).

 The operation of the sterilizer with manual control.

Press the button 44 "Program Selection" and the button switch 44 "Sealing the door" on the remote control 39 manual control. Press button 44 “Start the vacuum pump” 16 and “Reset steam from the chamber”. When the calculated vacuum pressure in the chamber reaches 0.05 MPa and is fixed by a vacuum gauge 24, turn off the "Reset from chamber" button. Press button 44 "Start steam in the camera." When the pressure in the chamber reaches 0.060 MPa, fixed by a vacuum gauge 24, turn off the button 44 "Start steam in the chamber". Thus, the first pulsation of the pumping of air from the chamber 1 was carried out. The pumping of the air must be repeated three more times, manipulating the buttons 44 described above. After the 4th pulsation, turn off the on buttons 44. Then turn on the “Steam into the chamber” button, and then bring the pressure in the chamber to the operating parameter of the selected program (for N 1 0.098 MPa $\genfrac{}{}{0ex}{}{\text{+0.013}}{\text{-0.006}}$ $\genfrac{}{}{0ex}{}{\text{MPa}}{\text{MPa}}$ ,, for N 2
0.105 ± 0.01 MPa, for N 3 it is necessary to have 0.21 MPa ± 0.01 MPa). According to the indication of the countdown (remaining) time, carry out a sterilization exposure, maintaining the temperature in chamber 1 by periodically turning the "Start steam in chamber" button on and off. At the end of the countdown, turn off the button 44. Then press the button of the selected program "Cooling" or "Drying").

 Stage of the cycle "Drying".

 With sterilization programs N 2 and N 3, after the completion of the "Mode" stage, the "Drying" stage is carried out. For this, the valves 18-4, 18-5 are closed, the steam supply to the chamber 1 is stopped. The vacuum system is turned on: the valve 18-2 opens, the vacuum pump 16 is turned on, and cooling water is supplied to the condenser 17. The capacitor 17 and the vacuum pump 16 are connected in series. The vapor from the chamber 1 under pressure enters the condenser 17 and, in contact with its cooling walls, condenses, while the vapor pressure is released. At the same time, the remaining steam and condensate are pumped out by a vacuum pump 16. A vacuum is created in chamber 1. The drying effect is obtained due to the discharge and hot material in the chamber 1. At the same time, the light signal on the valve 45 "Drying" lights up. The duration of the "Drying" stage is 15 minutes, in automatic mode. With manual control, the exposure time control stage "Cooling" or "Drying" is carried out by the indicator of the countdown on the remote control 39 to control the sterilization process by the hour. At the end of the "Drying" stage, it is necessary to turn off the vacuum pump 16 or the air supply to the chamber 1 by pressing the corresponding buttons 44. After the "Drying" stage, the "Alignment" stage is activated by turning on the "Align pressure" button 44.

 Alignment.

 When the pressure is equalized, the shut-off valve 18-9 (Cl. 9) opens and the air through the first filter 11 enters the chamber 1 through the check valve 14. When atmospheric pressure is reached (the pressure in the chamber is 0.0 MPa according to the pressure gauge 25), the signal " Finish". After that, the "Pressure equalization" button must be turned off. Opening the valve 18-9 is carried out using a pneumatic distributor 20-9 (PB 9). Next, you must turn off the button 44 "Sealing the door" and at the same time turn on the button 44 "Vacuum pump". After depressurization of the door 2 of the chamber 1, it is necessary to turn off the vacuum pump 16 and press the button 44 "Door open". Then unload the camera 1 is identical to that described above.

 Technical and economic efficiency of the invention.

 Experimental studies and tests of the current prototype and prototype of the inventive sterilizer intended for sterilization of drug solutions, glass vials, closures and medical devices indicators that, compared with the prototype, this sterilizer provides increased operational reliability, has versatility due to the introduction of three sterilization modes - solutions of medicines, medical devices and glass vials; It has increased productivity by increasing the capacity of the sterilization chamber, reducing the time of each sterilization program, evenly distributing the temperature in the chamber volume and receiving steam at its inlet under twice the pressure (compared with the prototype); Moreover, the inventive sterilizer has increased sterility due to the provision with it of preliminary sterilization of vials for drug solutions, facilitating its cleanliness and increased resistance of its surface to disinfection with a 3% hydrogen peroxide solution with the addition of a 0.5% detergent means of the type "Lotus" or 1% solution of chloramine. In addition, the inventive sterilizer is more economical in comparison with the prototype, because its electrical units and instrumentation have significantly lower power consumption; it is easier to maintain and operate due to improved automatic and metrological support of all sterilization modes, moreover, the automatic control mode is duplicated by manual control, and on all sterilization programs it has an arrow (direct-showing), light (at the stages of the sterilization cycle) and sound (at the finish) ) indication.

Claims (2)

 1. A sterilizer containing a frame, a rectangular sterilization chamber with water-cooling jackets, equipped with a sealed door with a cylindrical pneumatic drive and a door fixing unit with guide rollers, containers for process media and condensate collection, an oil distributor, first and second filters, safety and non-return valves, a unit control with a remote control, a vacuum line having a vacuum pump with a condenser, upper and lower level sensors, shut-off valves, relay sensors, a group of pressure gauges and a network of technol ogic pipelines, a power supply network and an air control network, characterized in that it is equipped with a group of pneumatic distributors located in the air control network, the output of the first of which is connected to the oil distributor, the output of the second valve is connected to the chamber door lock lock, the output of the third valve is connected to the pneumatic actuator of the first shut-off valve valve of the vacuum line to which the third sensor relay and the vacuum two-stage liquid ring pump are connected, in a sealed To verify the chamber under the gasket, a groove has been made for connecting the output of the fourth pneumatic distributor to it, the output of the fifth pneumatic distributor is connected to the pneumatic actuator of the sixth shut-off valve for supplying water to the water-cooling shirts, the output of the sixth pneumatic distributor is connected to the pneumatic actuator of the second shut-off valve for exhausting the vapor-air mixture from the chamber through the condensate tank, the seventh outlet the air distributor is connected to the pneumatic actuator of the third shut-off valve for air exhaust from the chamber, the output of the eighth air distributor I am connected to the pneumatic actuators of the fourth and fifth shutoff valves for steam inlet, the output of the ninth pneumatic distributor is connected to the pneumatic actuator of the ninth shutoff valve for balancing the pressure in the chamber, the output of the tenth pneumatic distributor is connected to the pneumatic actuator of the seventh shutoff valve for filling the condensate of the tank for process media, the output of the eleventh pneumatic distributor of the eightth pneumatic distributor connected through a check valve to the camera on one side and connected through a second filter with p on the other hand, while the working inputs of all pneumatic valves are connected to the compressed air system, and their switching inputs are connected by electric wires to the push-buttons of the control panel, the steam supply network is equipped with a gearbox for receiving steam under pressure, water-cooled camera shirts formed by stiffeners and equipped with blades built into the latter for film irrigation of the walls of the sterilization chamber, the latter is equipped with a slide and mobile sterilization insulating container having a guide for the slide, wherein the sealed sterilization chamber door is equipped with a locking device, the sealed door lock assembly is provided with a clamp latch and the sterilization chamber and its door lined and strengthened mullitokremnezemnistym roll thermally insulating material, and automatic control of the sterilizer duplicated manual control.  2. The sterilizer according to claim 1, characterized in that it is a block-modular design and is equipped with portable packaging containers for transporting block modules into them, and the frame is made in the form of a welded carbon steel frame for fixing the main nodes and mechanisms.