Pressure regulator for chemical laboratory

The voltage regulator used in the chemical laboratory to adjust the power of the heating coil is an autotransformer or a manual single-phase contact voltage regulator (Figure 22-4)

(1) Basic principles

A voltage regulator is an autotransformer with a continuously adjustable turns ratio

(Two) use

When in use, first adjust the voltage of the voltage regulator to zero with the help of the handwheel, then insert the voltage regulator plug and the heating coil plug, and finally rotate the handle slowly and evenly as needed to adjust the voltage

(3) Maintenance

(1) The housing of the regulator should be kept clean and tidy, and no water droplets, oil stains, etc.

(2) It must be placed in a dry, clean and ventilated place during use and storage.

(3) Frequent self-inspection is necessary.

(4) The surface of the coil and the brush should always be kept clean, otherwise it is easy to cause ignition and burn the surface of the coil

(5) After each use, adjust the voltage back to zero through the handle

(4) Safety instructions

(1) It cannot exceed 70% of the rated power at most, and it cannot be used with overload

(2) One voltage regulator can only drive one heating ring

(3) When moving or carrying the regulator, you should hold the regulator base in your hand, and do not drag the power cord or the handle of the regulator

(4) At least 20cm away from the oil bath and the reaction device to prevent the pressure regulator from burning or being corroded by the flushing material

(5) If there are suspicious problems such as internal ignition, burning smell, etc.

Overload, loose joints (Figure 22-5), and punching (Figure 22-6) are the three main reasons that cause the regulator to be burned

Figure 22-5 Overload and loose joints cause the regulator to be burned

Figure 22-6 The pressure regulator is burned due to the flushing material

(5) Use little common sense

(1) The relationship between the voltage of the regulator and the power of the heating coil: the power is proportional to the square of the voltage
.

(2) The voltage regulator is the easiest to ignite, causing the load to heat up, and the parts that are often burned are: the contact between the carbon brush and the coil, the coil input connector, the internal and external connections of the wiring board, and the paint peeling between the coils caused by the punching, etc.
Location
.

(3) Reasons for the increase in the temperature of the oil bath at night: ①The voltage of the dry branch circuit at night is higher than that in the day; ②The exhaust fan is turned off and the air circulation is lost → the heat dissipation effect of the oil bath is reduced → the temperature of the oil bath is increased; Corrosion→fire between coils→shortcut of current→equivalent to reduction in the number of coils→increased voltage and increased power→sudden increase in oil bath temperature
.

(6) Replacement technology and products

In order to eliminate the various defects and safety hazards of the voltage regulator [such as internal ignition, easy to be corroded and fire, complicated and easy to make mistakes, occupying area (Figure 22-7), etc.
], a new type of intelligent temperature control system (intelligent temperature control) Instrument) has entered the laboratory
.
The system adopts PID intelligent operation control, thermocouple temperature sensing, relay control output, single-key quick rise and fall temperature setting mode, setting and control of double-row digital display, and has a burnout protection function.
When the required temperature is set , The microcomputer will automatically adjust the heating rate according to the temperature difference.
Through continuous pulse power supply and proportional adjustment, the best heating effect can be quickly achieved.
The accuracy is ±1℃, which can safely and accurately heat and control the temperature
.
It is small in size and does not occupy valuable fume hood space.
It can be easily installed on the pillar of the agitator or used in other safe places with sufficient safety distance, as shown in Figure 22-8
.

Figure 22-7 Traditional fishing regulator will occupy limited space in the cabinet

Figure 22-8 Smart temperature controller does not occupy effective space

Precautions for the use of the intelligent temperature control instrument: The temperature control probe needs to be fixed firmly and cannot be shaken: it should be placed in a suitable position of the heat transfer oil, not close to the heating ring; the depth should be 2cm below the liquid surface, and it should not fall to the bottom
.
In addition, make sure that the heating coil is completely immersed in oil
.

Figure 22-9 shows the fire event caused by the improper position of the temperature control probe, and the heat transfer oil has been dried
.

Figure 22-9 Fire event caused by improper position of temperature control probe

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