Analysis of Causes of Air Compressor Trip Caused by Unreasonable Design of Electrical Principle

Process interlocking is a kind of protection circuit often used in the protection of large-scale units. Common process interlock protection has oil pressure, water pressure, temperature, etc. When the protection conditions are not available, the main motor can refuse to operate to achieve the purpose of protection.

A time relay is a relay that generates a jump change (or contact action) after the input circuit has been added (or removed) with an action signal that has passed the specified accurate time.

When the coil is energized (voltage specifications are ac38V, ac22V or dc22V, dc24v, etc.), the armature and the pallet are attracted by the core and instantaneously moved down, so that the instantaneous action contact is turned on or off. However, the piston rod and the lever cannot fall together with the armature because the upper end of the piston rod is connected to the rubber film in the air chamber. When the piston rod starts to move downward under the action of the release spring, the rubber film is then concave downward. The air in the air chamber becomes thin and the piston rod is dampened and slowly descends. After a certain period of time, the piston rod is lowered to a certain position, and the delay contact is actuated by the lever, so that the breaking contact is opened and the moving contact is closed. From the energization of the coil to the completion of the delay contact, this time is the delay time of the relay. The length of the delay time can be changed by adjusting the size of the air inlet of the air chamber with a screw. After the attracting coil is de-energized, the relay is restored by the action of the return spring. Air is quickly expelled through the vent.

2 The principle of oil pressure interlock protection The contactor of the KM2 coil is electrically closed and the main contact is closed. The motor is stepped down by an autotransformer. The time relay KT1 coil is electrically connected, the KT1 auxiliary contact is delayed, the KA1 intermediate relay coil is electrically connected, the auxiliary contact KA1 is closed and self-protected, the KA1 normally closed auxiliary contact is opened, and the contactor KM1, KM2 coil is lost. Electric, KM1, KM2 main contacts open. The KM1 normally closed auxiliary contact is closed, the contactor KM3 coil is electrically connected, the KM3 main contact is closed, and the motor is operated at full pressure.

When the oil pressure is 0.IMPa, the instrument oil pressure interlocking contact is closed, the KT2 coil is energized, the KT2 normally closed contact is delayed, and the control loop power loss motor stops running. In order to achieve the purpose of protecting the unit ().

During the trial use, it was found that the time relay KT2 contacts were often stuck and the relay was often damaged. After inspection, the original control loop design has certain defects.

When the unit is stopped, the oil pressure is at O.IMPa, the oil pressure interlocking point is closed, the time relay KT2 coil is electrically connected, the KT2 auxiliary contact is delayed after 8 seconds, the KT2 coil is de-energized, and then the KT2 auxiliary touch When the point is closed, the time relay coil is electrically connected again, and the time relay KT2 coil has electric suction, so the frequency is repeated frequently, and the time relay is damaged for a long time. The KT2 contact often sticks or is damaged, causing the control circuit to fail to start the unit.

In order to ensure the normal operation of the unit, for the design defects found in the daily maintenance operation, the time relay KT2 coil is always energized after the unit is stopped, the control line is improved, and the hydraulic interlock point is changed to the KM3 auxiliary contact. The rear side solves the problem that the time relay KT2 coil contact is easy to damage the defect accident ().

The head is closed and the KM1 auxiliary contact is self-protected. At the same time, the KM1 auxiliary contact is closed, the contactor KM2 coil is electrically connected and the main contact is closed, and the motor is stepped down by the autotransformer. The time relay KT1 coil is electrically connected, the KT1 auxiliary contact is time-closed, the KA1 intermediate relay coil is electrically connected, the auxiliary contact KA1 is closed, and the theoretical research V-fuel supply combustion chamber volume m3. furnace volume heat load (qV) It is one of the most important thermal characteristic parameters in boiler furnace design and operation, especially for the hand-fired furnace structure of atmospheric boiler. The grate area heat load qR qR refers to the heat power of the combustion exotherm on the unit grate area, also known as the visible furnace discharge heat.

qR is the most important thermal characteristic parameter of the fixed grate combustion area (R), and is also the only characteristic parameter. The design calculates the thermal characteristics according to the empirical statistical value qR. 4) The thermal characteristics of the fixed grate hand furnace (available The design parameters are selected) the excess air ratio of the furnace outlet a 5) the arrangement of the heated surface (the convection tube bundle of the furnace body) The natural water circulation in the furnace is completely dependent on the water, the pressure head formed by the difference in vapor density is established, and the circulating pressure head is again It is generated by heat, and the resistance to flow is also related to heat. The water pipe type boiler should be arranged reasonably in the cross pipe bundle of the furnace body. As many as possible, several layers of water pipes should be arranged below the sky tube, and the arrangement should be staggered to improve the high temperature smoke flow laterally flushing the heated surface area and reduce the exhaust gas temperature. The pipe and the horizontal plane of the furnace body are at an angle of 10.12. so that the flow resistance in the pipe is reduced, the contact between the pipe wall and the water is ensured, and the flow deviation of the parallel pipes is reduced, so that the heat absorption and heat conduction are balanced.

7 Calculation of boiler thermal efficiency and various heat losses 1) Definition of boiler thermal efficiency: The heat that is effectively utilized in the boiler ((1) The percentage of total heat input to the boiler (QR) is called the boiler thermal efficiency, expressed as “.

The heat balance of the boiler refers to the heat Qr (also known as the heat of charge, mainly the heat of combustion of the fuel) sent to the boiler and the heat Q1 (ie the heat absorption of the working medium) and the heat loss Q2, Q3 of the boiler. The relationship between the sum of Q4, Q5, and Q6. The heat balance equation is as follows; (solid, liquid fuel), (gas fuel is KJ/m3); Q3-burner gas incomplete combustion heat loss, KJ/Kg or KJ/m3 Q4- boiler solid incomplete combustion heat loss, KJ /Kg or KJ/m3 Q6-physical heat loss of boiler ash and physical heat loss of cooling water, KJ/Kg or KJ/m3. In the calculation of heat, solid, liquid is based on lKg mass fuel, based on gas The fuel is based on lm3 volume fuel under standard conditions (0.1013 MPa. 0 °C).

The constant pressure vertical hot water boiler is matched in the application of heating engineering. The problem of thermal efficiency should be taken seriously with scientific attitude, especially the selection of larger heating area should be more cautious. Key thermal parameters should be calculated and verified in design and manufacture. It is recommended that the capacity of the vertical atmospheric hot water boiler should not exceed 1 MW in design and manufacture, and the horizontal structure should be preferred for the 1.4 MW furnace.

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