mixing tank

  Components

        Folded stirring shaft

        The power output of the motor in the mixing equipment is transmitted to the mixer through the mixing shaft, so the mixing shaft must be strong enough. At the same time, the mixing shaft should be connected with the mixer and pass through the shaft seal device, bearings, couplings and other parts, so the mixing shaft should also have a reasonable structure, high machining accuracy and fitting tolerance.

        According to the support situation, the mixing shaft can be divided into cantilever type and single span type. The cantilever type stirring shaft does not have intermediate bearing or bottom bearing inside the mixing equipment, so it is easy to maintain and repair, especially for biological, food or drug mixing equipment with high cleanliness requirements, which reduces the components inside the equipment, so it should be preferred.

        Folded internal components

        Including baffles, coils, guide barrels, gas distributors, etc.

        In order to eliminate the phenomenon of whirling of liquid in the mixing vessel, so that the stirred liquid is tossed up and down to achieve uniform mixing, it is usually necessary to add a baffle in the mixing vessel. Usually the width of the baffle is about 1/12 to 1/10 of the container diameter, where the equipment accessories such as thermometer, heat transfer snake tube or various support body can also play a certain role in the baffle, but often does not reach the "full baffle conditions". Usually increase the number of baffles and their width, power consumption will also increase, but after increasing to a certain value, the power consumption will not increase again, the working conditions at this time is called "full baffle conditions".

        In the mixing vessel, the fluid can flow in all directions to the stirrer, the fluid stroke length varies, in the need to control the speed and direction of reflux, used to determine a stream of conditions can be used to guide the barrel. Guide tube is the upper and lower open cylinder, installed in the container, in the stirring and mixing to play a guide, not only to improve the degree of mixing of fluid in the container, to strengthen the direct shearing effect of the agitator on the fluid, but also to cause a certain circulation flow, so that the fluid in the container can be strongly mixed area through the guide tube to improve mixing efficiency. After the installation of the guide barrel, the circulation path is limited, reducing the chance of fluid short circuit. The deflector barrel is mainly used for the deflection of propeller, screw and turbine type mixers.

        Folded Shaft Seals

        Shaft seal is an important part of the mixing equipment. The shaft seal is a dynamic seal, and its function is to ensure a certain positive pressure or vacuum in the mixing equipment, to prevent the escape of the material being mixed and the infiltration of impurities, so not all shaft seal types can be used in mixing equipment. In the mixing equipment, the most commonly used shaft seals are liquid seal, packing seal and mechanical seal, etc.

        Folded liquid seal

        When the working pressure inside the mixing equipment is atmospheric pressure and the role of shaft seal is only to prevent dust and impurities from entering the internal working medium, or to isolate the working medium from the environmental medium around the mixing equipment, liquid seal can be used. The structure of liquid seal is simple, and there is no direct contact with the drive shaft to cause friction parts. However, in order to ensure that the clearance between the cylindrical shell or stationary element and the rotating element meets the design requirements, the processing and installation of the parts of the seal are more demanding.

        At the same time, due to the influence of structural characteristics, the use of liquid seal is narrow. It is generally applicable to the working medium which is non-flammable and explosive or mildly hazardous in toxicity, and the working pressure in the equipment is equal to atmospheric pressure and the temperature range is 20-80℃.

        It is worth noting that the liquid working medium should not be full of mixing equipment; and the sealing liquid should be used as far as possible to mix the working medium in the equipment, or neutral liquid that does not have physical and chemical effects with the working medium, and at the same time must be very little volatile and do not pollute the atmosphere.

        Packing seal

        It has the advantages of simple structure, low manufacturing requirements and easy maintenance. However, the packing is easy to wear, and the reliability of the seal is poor. It is generally only applicable to mixing equipment with low pressure or low speed, non-corrosive and weakly corrosive media, and allows regular maintenance.

        Mechanical Seal

        Mechanical seal is a device that changes the sealing surface of the rotating shaft from axial to radial, and achieves sealing through the mutual fitting of the two end surfaces of the dynamic ring and static ring and relative movement, also called end seal. Mechanical seal has low leakage rate, reliable sealing performance, low power consumption, long service life, no frequent maintenance, and can meet the automation of production processes and high temperature, low temperature, high pressure, high vacuum, high speed and a variety of flammable, explosive, corrosive, abrasive media and solid particles containing media sealing requirements.

        Compared with packing seal, mechanical seal has the following advantages:

1, reliable sealing, stable sealing state in long-term operation, leakage is very small, the leakage is only about 1% of the packing seal;

2, long service life, in oil, water media can generally reach 1-2 years or longer, in chemical media can generally work more than half a year;

3, low friction power consumption, its friction power is only 10-50% of the packing seal;

4、The shaft or sleeve basically does not wear;

5、Long maintenance cycle, the end face can be automatically compensated after wear, generally do not need regular maintenance;

6、Good vibration resistance, insensitive to vibration, deflection of the rotating shaft and deflection of the shaft to the sealing chamber;

7, a wide range of applications, can be used for high temperature, low temperature, high pressure, vacuum, different rotating frequency, and a variety of corrosive media and media containing abrasive seals.

        It is due to the above advantages of mechanical seal, it has been widely used in the mixing equipment.

        There are two kinds of mechanical seals: single-end mechanical seal and double-end mechanical seal. The price of single-end mechanical seal is lower, and when single-end mechanical seal cannot meet the requirements, double-end mechanical seal is needed.

        When the mixing medium is highly toxic, flammable, explosive, or more expensive high-purity materials, or need to operate in a high vacuum state, the sealing requirements are very high, and the packing seal and mechanical seal can not meet, can choose a fully enclosed magnetic transmission device.

        Transmission device

        The transmission device of mixing equipment includes motor, transmission, coupling, bearing and frame. The stirring drive mechanism usually adopts the combination of motor and transmission or the motor with frequency converter to make the stirring reach the required speed.

        The role of the transmission device is to make the mixing shaft rotate at the required speed and ensure that the mixing shaft gets the required torque. In most mixing plants there is only one mixing shaft and the agitator rotates in one direction at a constant speed. However, there are some special mixing equipment where two mixing shafts can be used in one mixing equipment to obtain better mixing results and to allow the agitator to perform complex movements, such as reciprocating, reciprocating, planetary, etc.

        Motor

        The mixing shaft of a mixing plant is usually driven by an electric motor. Since the speed of the mixing equipment is generally low, the motor is in most cases used in combination with a transmission, and sometimes a frequency converter is used to regulate the speed directly. For this reason, when choosing an electric motor, special consideration should be given to matching it with the transmission.

        Agitator

        The stirrer, also known as impeller or paddle, is the core component of the mixing equipment. According to the flow pattern generated in the agitator's mixing kettle, the agitator can basically be divided into two kinds of axial flow and radial flow. For example, propeller impellers and new wing impellers belong to axial flow agitators, while various straight and curved turbine impellers belong to radial flow agitators.        

        The stirrer is usually inserted vertically into the kettle from the top center of the kettle, but sometimes it is also inserted laterally, at the bottom or laterally. Different installation methods should be chosen according to different mixing requirements.

        Types of stirrers

        The rotating paddle stirrer is composed of 2~3 propeller blades (Figure 2), with a high working speed and a general circumferential speed of 5~15m/s. The rotating paddle stirrer mainly causes axial liquid flow and generates a large circulation volume, which is suitable for stirring low viscosity (<2Pa-s) liquids, emulsions and suspensions with less than 10% solid particles. The shaft of the stirrer can also be inserted horizontally or obliquely into the tank, where the circulation circuit of liquid flow is asymmetrical, which can increase turbulence and prevent liquid surface depression.

        ②Turbine type stirrer consists of 2~4 flat or curved blades mounted on a horizontal disc (Figure 3). The ratio of outer diameter, width and height of the blades is generally 20:5:4, and the circumferential speed is generally 3~8m/s. The turbine causes highly turbulent radial flow when rotating, and is suitable for the dispersion of gas and insoluble liquid and liquid-liquid phase reaction process. The viscosity of the agitated liquid generally does not exceed 25 Pa-s.

        Paddle stirrer There are two types of paddle stirrers: flat paddle stirrer and inclined paddle stirrer. The flat paddle stirrer is composed of two flat and straight blades. The ratio of blade diameter to height is 4~10, and the circumferential speed is 1.5~3m/s. The resulting radial liquid flow speed is small. Inclined paddle stirrer (Figure 4), the two blades are folded 45° or 60° in opposite directions, thus producing axial liquid flow. Paddle stirrers are simple in structure and are often used for mixing low-viscosity liquids as well as dissolving and suspending solid particles.

        The shape of the outer edge of the paddle is consistent with the inner wall of the mixing tank (Figure 5), and there is only a small gap between them, which can remove the viscous reaction products attached to the tank wall or the solids accumulated at the bottom of the tank and maintain a good heat transfer effect. The circumferential speed of the outer edge of the paddle is 0.5~1.5m/s, which can be used to stir Newtonian and plastic fluids with viscosity up to 200Pa-s (see Viscous Fluid Flow. Only when stirring high viscosity liquid, there is a large stagnation zone in the liquid layer.

        ⑤ Spiral stirrer The outer diameter of the spiral belt is equal to the pitch (Figure 6), specifically for stirring high-viscosity liquids (200~500Pa-s) and proposed plastic fluids, usually operating in the laminar flow state.

        Corning digital heaters have a closed circuit knob to monitor and adjust the stirring speed. The microprocessor automatically adjusts motor power to suit water quality, viscous solutions and semi-solid solutions.        

        The Corning digital heaters have an optional external temperature controller (Cat. No. 6795PR), and they can monitor and control the temperature in the vessel.

Heating device or cooling device

        Generally the use unit depends on whether the material is heated or dried or cooled. In the custom range, the temperature should be below 200℃ and the use pressure is lower than 0.1Mpa. the heating method can be determined according to the production conditions of the use unit. There are two kinds of heating methods, such as hot oil and other media circulation and direct electric heating. Hot oil and other media circulation is heat-conducting oil in another configuration of the heating tank heated to a certain temperature, through the hot oil pump for transmission and circulation; direct heating is the jacket directly installed on the electric heating tube, so that the heat-conducting oil heated to the required temperature (the temperature can be adjusted according to the actual situation). Cooling cycle is to use water to circulate inside and outside the jacket, so that the material does not produce caking or stickiness at a certain temperature. It can also be heated or cooled according to the user's requirements by adding coils and other forms. (Note: the general use of heating or cooling medium is to take the principle of low pipe mouth into, high pipe mouth out)

        Standard operation procedure of mixing tank

        Purpose

        To eliminate the occurrence of human operation accidents and ensure the normal operation of the equipment.

        Scope of application

        400L, 300L, 600L mixing tank.

        Responsibilities

        1. Extraction operators use and sanitary cleaning according to this regulation.

        2. Maintenance personnel repair and maintain according to this regulation.

        3. The manager of production management department is responsible for supervising the implementation of this regulation.

        Contents

        1. Use

① Check if the equipment is "normal", make sure the equipment is clean and meet the requirements.

② Check whether the connection between slurry and motor is firm and reliable.

③ Select the mixing tank according to the volume of the material and liquid to be processed, generally the volume of the material and liquid sample is not less than 1/3 of the volume of the mixing tank.

④ Slowly adjust the speed knob (variable frequency speed controller) to slowly increase the stirring speed until it reaches the desired speed. The speed range is 80--1400 r/min.

⑤ Turn the speed knob to the position of zero speed.

⑥ Add the material liquid and turn on the power switch.

⑦ Turn off the power when the equipment is finished.

⑧ Clean and disinfect according to the Standard Operating Procedures for Cleaning and Disinfection of Mixing Tank.

⑨ Fill in the relevant records. 

2. Caution

① Pay attention to the distance between the stirring rotor and the container, if it is a glass container, the stirring speed should not be too fast.

② If the sample needs to be processed, the power switch must be turned off and the speed knob must be adjusted to the minimum before repeating the above operation.

③ If a serious spark occurs, the machine must be stopped immediately for inspection and repair to avoid further damage.

④ If the motor does not turn during use, check the power supply, speed governor, fuse and motor brush first. If the speed control part or motor damage, should notify the maintenance personnel to repair.

3. Installation and commissioning

1, please check whether there is serious damage and serious deformation of the equipment in transport, as well as check whether the fasteners of the equipment are loose and other phenomena!

2、Please ask the user to adopt the way of pre-buried ground bolts to install the equipment horizontally on a firm foundation.

3、Under the guidance of professionals, please install the equipment, electrical control devices and accessories correctly, and check whether the pipeline is smooth, whether the instrumentation installed is correct, and whether there is damage. Before starting the equipment, please check whether there are people or objects in and around the equipment that affect the normal operation of the equipment to avoid danger.

4、After installation, please run a test run for a few seconds to make sure there is no electrical short circuit or abnormal sound before a short test run.

5、If the mixing tank is equipped with mechanical seal, an appropriate amount of 10# or sewing oil must be injected into the lubricating tank of the machine seal before the main machine starts, and cooling water must be passed into the cooling chamber of the machine seal so that the machine seal device can be well lubricated and cooled. The machine seal is not adjusted at the factory. After installation, adjust the machine seal to the best position according to the installation and use instructions before normal operation (according to the user's needs).

6. After normal operation, please check the bearing temperature, running smoothness, sealing, etc. and whether the instrument is normal, and make sure it is normal before feeding and running.

4. Use and maintenance

1、The equipment is atmospheric pressure equipment, heat exchanger if the pipeline is smooth also considered atmospheric pressure, if the pressure is super high, please check whether the import and export blockage phenomenon.

2, the reducer should be installed in 40 # - 50 # oil or 70 # - 90 # extreme pressure industrial gear oil, the first 20 days of operation (8 hours of work per day), replace the oil and clean the oil tank, after every 3-5 months to replace and clean the oil tank. (No reducer except)

3、If the condenser is equipped, the effect of heat exchange can be judged according to whether it should be cleaned for heat exchange pipeline.

4、Stirring tank should be loaded strictly in accordance with the effective volume of the tank, overload is strictly prohibited, so as not to burn the motor or damage the reducer and other components.

5、If the equipment is not used for a long time, it should be cleaned, lubricant should be injected into all parts and power should be cut off.

The above content is my understanding, if you have different opinions or needs, welcome to contact us.