The Daily Maintenance of Magnetic Stirrer

The Daily Maintenance of Magnetic Stirrer

Magnetic stirrer is an instrument works under the principle of mixing the material. Suitable for the viscosity is not very large solid-liquid mixture or liquid in the physical magnetic. In the daily usage if the magnetic stirrer broken, we need to calmly deal with, do not be anxious. Some treatment and methods can be used to determine the cause of the failure, so the daily use of magnetic stirrer in the process must also pay attention to do maintenance of magnetic stirrer, extend the equipment Of life as much as possible.

First, the routine maintenance

1.       First static then dynamic: determine the electrical equipment buttons, transformers, thermal relays and the fuse is good or bad, to determine the fault position when the device is not powered. Power test, listen to the sound, test parameters, determine the fault, then maintenance. If the motor phase is missing, if the measured three-phase voltage value can not be identified, it should listen to the sound, individually measured each relative to the voltage, to determine which phase defects.

2.       First the general then special: due to assembly quality or other equipment failure caused by failure, generally account for about 50% of common faults. Electrical equipment, special failures are mostly soft faults, rely on experience and instrumentation to measure and repair.

3.       First cleaning then repairing: for the heavy pollution of electrical equipment, clean its buttons, wiring points, contact points, check the external control keys are malfunctioning. Many failures are caused by dirt and conductive dust.

4.       First Machine then electrical: only in the determination of mechanical parts without failure, and then electrical inspection. Check the circuit failure, you should use the detection equipment to find the fault location, to confirm no contact failure, and then targeted to see the relationship between the operation of the line and machinery to avoid misjudgment.

5.       Thinking first before moving hands: for electric stirrer failure, should not rush to the first hands-on, ask the reason of fault. For unfamiliar equipment, should also be familiar with the circuit principle and structural characteristics, to comply with the corresponding rules, before you disassemble. Familiarize yourself with the function, location, connection, and relationship with other devices in each electrical component. In the absence of an assembly diagram, you should dismantle and sketch the mark.

6.       First debugging then fault: debugging and fault coexistence of electrical equipment, should first remove the fault, and then debugging, commissioning must be carried out under the premise of the electrical line speed.

7.       First external then internal: should first check whether the equipment obvious cracks, defects, to understand its maintenance history, life, etc., and then check the machine internal. Before the demolition should be excluded from the surrounding fault factors, identified as the machine after the failure to disassemble, otherwise, blind disassembly, the equipment may repair the worse.

8.       First power then equipment: the power part of the failure rate in the entire fault equipment accounted for a high proportion, so the first maintenance power can often be more with less.

Second, the maintenance when working

1.   It is best not to let the instrument works in the absence of heating liquid.

2.  The machine should be checked before the operation of the ground, to ensure that after the completion of work.

3.  In order to ensure no damage to the instrument, usually the instrument will be placed inside the insulation material, so the first time we use the magnetic stirrer will find a little smoke or pungent taste, it is normal. Not the Product quality problems, but Keep it ventilated.

4. The magnetic stirrer inside the device heating the upper limit, so in the heating time must be taken into account, the best way is to ensure that the machine is not only heating, and remember the state of the motor into a rotating state, so that The greatest degree of protection of magnetic stirrer.

5.   After the completion of heating, turn off the heat first, and after the temperature has been dispersed and then close the mixing.

6.   To ensure that the environment of the dry. Because in a humid environment, the instrument easily leads to leakage and other phenomena, which is why we must ensure that the instrument grounded, if the instrument is very wet when you must use hot air dry.

7.   The operation must be careful, do not be burned, because the general temperature is relatively high.

8.  For the sake of safety equipment on the back of a fuse, the device is still working after the power can check whether the need to replace.

Kent Yuan (Mr.) Hangzhou Zhongwang Technology Co., LTD.

P  /Wahtsapp: +86 15068109723  E lei@zonwon.com

Coyp right by @Hangzhou Zhongwang Technology CO.,LTD

Determination of Molecular Weight of Polyacrylamide by Dilute Solution Viscosity Method

Determination of Molecular Weight of Polyacrylamide by Dilute Solution Viscosity Method

Abstract: To learn and master the Ubbelohde viscometer viscosity measurement method; to understand the statistical significance of the molecular average molecular weight and polymer dilute solution of the intrinsic viscosity of the characterization method; master the determination of polymer dilute solution viscosity experiment Technology and viscosity method to characterize the molecular weight of polymer; the viscosity of polyacrylamide aqueous solution to reflect the molecular weight of polyacrylamide;

Experimental principle

        Liquid flow is due to external force molecules irreversible displacement process. Liquid molecules exist between the interaction force, so when the polymer liquid flow, the polymer molecules to produce internal friction between the performance of the liquid viscosity characteristics.

        According to Newton's law of viscous flow, the viscous resistance of the liquid to the flow is caused by the flow gradient between the two layers of flowing liquid (with A) due to intermolecular friction.

In the Ubbelohde viscometer capillary, it is assumed that the force that causes the polymer dilute solution to flow is all used to overcome the internal friction f:

For most flexible polymer - good dilute solution solvent system, protraction

with c and  with c. Extrapolated intercepts coincide with the value of the point

 , that is, the shape of the polymer is the polymer solution between the chain and the polymer solvent interaction between the molecules of the reaction, the current Mark-Houwink empirical formula:

Can be found in the relevant manual. Therefore, the polymer can be dilute the viscosity of the polymer to calculate the molecular weight.

Instrument: Ubbelohde viscometer constant temperature water bath, electronic scales, stopwatch, pipettes, flasks, ear cleaning ball, glass sand funnel;

Reagents: polyacrylamide samples, sodium chloride, purified water;

Experimental steps:

1. Solution preparation

2. Viscosity meter cleaning and drying

3. Viscometer installation: check the viscometer, with a clamp carefully fixed viscometer, into the constant temperature sink. The viscometer should be kept vertical, and the constant temperature surface should be immersed in the two balls above the capillary and the temperature remains constant.

4. Determine the elution time of the solution: Remove the 10 ml solution from the self-volumetric flask and inject it from the A tube into the viscometer. The clip holds the C tube and draws the solution from the B tube to the top of the a The ball volume of half of the time until the release of the ear ball, release the C tube clip, the air into the C tube, immediately horizontally watching the decline in the liquid level with a stopwatch recorded liquid flow through the a and b line time is Out of time.

5 ml, 5 ml, 10 ml and 10 ml of solvent were added to the same solution for 2/3, 1/2, 1/3, 1/4 of the original solution, and the respective elution times (t2, t3 , T4, t5).

Determination of pure solvent elution time: The solution in the viscometer was poured out and washed several times with solvent to determine the elution time t0 of the pure solvent.

Kent Yuan (Mr.) Hangzhou Zhongwang Technology Co., LTD.

P  /Wahtsapp: +86 15068109723  E lei@zonwon.com

Coyp right by @Hangzhou Zhongwang Technology CO.,LTD

Difference Between Ubbelohde Viscometer and Brookfield Viscometer

Difference Between Ubbelohde Viscometer and Brookfield Viscometer

Abstract：Introducing of Ubbelohde viscometer and Brookfield Viscometer. Concept, difference and advantages of ubbelohde viscometer and Brookfield viscometer.

Brief introduction of Ubbelohde viscometer：

When the fluid is flowing by external force, there is a tangential internal friction between the flowing liquid layers, and if the liquid is to pass through the tube, a portion of the work must be consumed to overcome the resistance of the flow. When the flow rate is low, the liquid in the pipe is advanced in a straight line parallel to the pipe wall. The liquid closest to the pipe wall is actually stationary, and the farther the distance from the tube wall is, the greater the flow rate is. The tangential force f between the flow layers is proportional to the contact area A between the two layers and the velocity difference Δv, and is inversely proportional to the distance Δx between the two layers: where η is the proportional coefficient, called the viscosity coefficient of the liquid, Referred to as viscosity.

The molar mass of the polymer not only reflects the size of the polymer molecule, but also directly related to its physical properties, is an important basic parameter. Unlike conventional inorganic or low molecular organic matter, the polymer is mostly macromolecular mixture of different molar mass, so the measured molar mass of polymer is usually a statistical average. 

Brief introduction of Brookfield Viscometer:

       Brookfield Engineering is an engineering and manufacturing company with headquarters in Middleboro, Massachusetts. Its product line includes laboratory viscometers, rheometers, texture analyzers, and powder flow testers as well as in-line process instrumentation. These instruments are used by research, design, and process control departments. It was suspected of causing one of Massachusetts' most unusual and serious residential toxic waste contamination problems, and settled the claim by paying relocation and cleanup costs without admitting responsibility.       

Classical Brookfield viscometers employ the principle of rotational viscometry - the torque required to turn an object, such as a spindle, in a fluid indicates the viscosity of the fluid. Torque is applied through a calibrated spring to a disk or bob spindle immersed in test fluid and the spring deflection measures the viscous drag of the fluid against the spindle. The amount of viscous drag is proportional to the amount of torque required to rotate the spindle, and thus to the viscosity of a Newtonian fluid.In the case of non-Newtonian fluids, Brookfield viscosities measured under the same conditions (model, spindle, speed, temperature, time of test, container, and any other sample preparation procedures that may affect the behavior of the fluid) can be compared. When developing a new test method, trial and error is often necessary in order to determine the proper spindle and speeds. Successful test methods will deliver a % torque reading between 10 and 100. The rheologicalbehavior of the test fluid can be observed using the same spindle at different speeds, but because the geometry of the fluid around a rotating bob or disk spindle in a large container does not allow a single shear rate to be assigned, proper rheometry is not feasible using this setup.

Apart from its rotating bob viscometers, Brookfield now also produces defined-geometry rheometers which allow complete rheological analysis of fluids.

Difference Between Ubbelohde Viscometer and Brookfield Viscometer

1. Ubbelohde Viscometer：Cheap, suitable for relative measurement, Uptel viscometer itself can not control temperature, with precision thermostat can be accurate measurement of viscosity, in addition to the Ubbelohde viscometer installed in the automatic viscosity test equipment, you can achieve Ubbel's viscosity Automatic measurement, directly to the intrinsic viscosity, than the viscosity, relative viscosity, viscosity, viscosity average molecular weight and other needs of the measurement results.
2. Brookfield Viscometer：Have adopted the well-known viscosity measurement principle, which absorbs the viscosity value by the continuous rotation of the rotor immersed in the liquid to be measured. The torque is proportional to the resistance of the rotor immersed in the sample by sticky dragging, proportion.

Kent Yuan (Mr.) Hangzhou Zhongwang Technology Co., LTD.

P  /Wahtsapp: +86 15068109723  E lei@zonwon.com

Coyp right by @Hangzhou Zhongwang Technology CO.,LTD

IVS800 Automatic Polymer Viscosity Measuring System

Determination Liquid viscosity determination at different temperatures

Determination Liquid viscosity determination at different temperatures

Abstract: to understand the principle of the thermostatic bath, structure and function of each component, learn to adjust the thermostat. Understand the significance of liquid viscosity and the principle and method of measuring viscosity. Determination of viscosity of ethanol at different temperatures by Ubbelohde viscometer, calculate the activation energy of ethanol flow.

1.      Constant temperature technology:

A thermostatic bath commonly used in laboratory is a common temperature control device. The basic principle is that when the bath temperature is lower than the set temperature, it heating automatically; when the bath bath temperature is higher than the set temperature, stop heating automatically, and automatically depending on the situation. As a result, the temperature fluctuates in a small range, and the system is confined to the required temperature at very small intervals under the constant temperature water.

2. Determination of liquid viscosity:

All the liquid have viscosity, it can be represented by a viscous coefficient η. η has the relationship with the molecular size, shape, and composition of liquid molecular force. In this experiment, the viscosity of liquid is measured by capillary outflow method. Under certain temperature by Poiseuille formula PI ETA = r4pt/ (8LV). The international system of η units is ETA Pa * s, 1P=0.1Pa * s. Usually use two kinds of liquid viscosity formula for doing business. That is η2=η1×p2t2/p1t1

The temperature changes of the intermolecular force , viscosity also changed.The relationship are η=Aexp(Evis/RT) or Inη=InA+Evis/RT.
 Among them, Evis is called liquid flow activation energy, to In on the 1/T map in a straight line, the slope of S=Evis/R,so Evis=SR.

Operation procedure of viscosity test:

1. Switch on the constant temperature sink power supply, turn on the switch, set the temperature for the experiment temperature, wait for the water temperature to the set temperature and keep stable.

2. Determination of 25 degree ethanol through Ubbelohde viscometer capillary time. Clamp the tube on the C tube with a clamp to absorb the gas. Draw the ethanol from the D ball, capillary, and E ball to the G ball. Step B tube of latex tube, remove the C tube clip, at this time, D ball part of ethanol flow back to the F ball, D ball through the C tube and atmospheric communication, capillary end that the atmosphere. The B pipe clamp is removed and the ethanol falls in the B tube. When the liquid level flows through the scale a, the stopwatch is started and the time is stopped when the liquid level drops to B. This time is the time between the AB and the volume of V ethanol flowing through the capillary tube ta. Repeat operation 2~3 times, each difference is not more than 0.5s, take the average.

3. Increase the temperature 3 degrees, ibid., the 2 step, determine the temperature of ethanol flow through the capillary tube, so measured 4~5 data.

4. After measuring, turn off the thermostat, the switch and the agitation tank switch, disconnect the power supply, and return the instrument, ear ball and stopwatch.

Experimental raw data

Number	1		2		3		4
T/℃	28		31		34		37
ρ/g×cm-3	0.78267		0.78		0.77756		0.775
t/s	a	b	a	b	a	b	a	b
	306.44	306.68	294.47	296.9	275.18	277.87	266.25	265.5

When T = 28 ° C, the viscosity of ethanol is η1 = 1.015 mPa × s

The activation energy of anhydrous ethanol was found to be 13.40 kj / mol

Experimental Data Processing and Results Discussion:

From the formula η1 / η2 = p1t1 / p2t2, and the viscosity of ethanol η1 = 1.015mPa × s can be obtained at different temperatures viscosity, as shown in the table below:

1/(T/K-1)	3.32×10-3	3.28×10-3	3.26×10-3	3.22×10-3
In(η/mPa×s)	0.0149	-0.0243	-0.0943	-0.138

Make Inη—1/T chart

Takes on the straight line A (0.00331, -0.001), B (0.00324, -0.109) two points, find the slope S = (0.001-0.109) / (0.00324-0.00331) = 1.54 × 103K

             Evis = RS = 8.31 x 1.54 x 103 KJ / mol = 12.80 KJ / mol

   The relative error E = | Evis-Evis true | / Evis true × 100% = | (12.8-13.4) /13.4|×100%=4.47%

Experimental error analysis:

1. viscometer can not be guaranteed when placed completely straight, resulting in a certain error;

2. with a stopwatch time, because the stopwatch itself is not accurate enough, will cause some error, and in the stopwatch may appear even when the phenomenon, so that measurement is not allowed;

3. because in the observation of the liquid surface, in the a and b line to determine the standard can not be exactly the same, resulting in a certain error.

Note:

1. viscometer must be placed as far as possible;

2. with the suction ball to absorb the liquid, the liquid may not be mixed with bubbles, or should be exhausted in order to be able to experiment;

3. if the operation to contact B tube or C tube should be particularly careful, because the B tube or C tube has a longer arm, the force is small but the formation of a larger torque, easy to break at the interface between the tube;

4. viscometer can not water, should ensure that the purity of the tube ethanol.

Kent Yuan (Mr.) Hangzhou Zhongwang Technology Co., LTD.

P  /Wahtsapp: +86 15068109723  E lei@zonwon.com

Coyp right by @Hangzhou Zhongwang Technology CO.,LTD