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Application Of Resistance Heating In Installation Of Hydroelectric Unit
Hangzhou Ualloy Material Co.,Ltd | Updated: Nov 28, 2017

Application of resistance heating in installation of hydroelectric unit

In the installation of hydropower unit shaft bolt tension is usually hydraulic tensile, tensile and tensile resistance heating flame heating three ways for the installation of small and medium hydropower, bolts tensile applied by resistance heating method, but also a part of the hydraulic tensile bolt connection way of. The resistance heating method can be used not only for the connection between the main shaft of the turbine and the main shaft of the generator, but also for the connection between the main shaft of the hydraulic turbine and the rotary wheel.

First, an overview

Resistance heating method applied to tensile bolt, including heating resistance selection, heating resistance corresponding power supply and switch configuration, equipment installation and adjustment, horizontal or vertical position measuring device stretching lineation, the initial heating tensile test and tensile bolt fastening. The selection of resistance heaters should be based on the design parameters of different manufacturers, such as coupling bolts, main shaft and runner flange. The following is mainly about the brief construction process of resistance heating method and the correction of the heating elongation of coupling bolts.

Two. Construction process

1. Preparation before construction

1.1 put the wheel on the installation platform according to the position of the planning work. When placing the runner, it is considered that the staff can enter the work from the bottom. The runner can be filled with four high 800mm steel piers to facilitate the assembly of the drain cone or nut cover.

1.2 a pair of wedges are arranged on the four steel piers to adjust the level of the wheel to the requirements of the 0.02mm/m of the spindle or the main shaft of the turbine.

1.3, sweep the runner and the flange of the main shaft and the main shaft of the turbine or the main shaft of the generator, and assemble the runner and main shaft related components and accessories according to the design requirements.

1.4, check the main shaft (main shaft or generator shaft) of the main shaft, the positive and negative two planes of the flange plane and the connection surface on the runner. Check the connection surface between the large shaft and the runner with the small area grinding platform, and finally meet the horizontal adjustment requirements of the flange surface.

2. Selection of resistance heaters

According to the design requirements, the bolt is heated and tightened in turn so that the elongation of the bolt is reached to the design value, or the nut is rotated to the corresponding angle. In combination with the environment conditions of the construction site, it is not suitable to increase the temperature too quickly during the heating process, so as to avoid the large deviation of the bolt length measured. Can choose the resistance heater high power three-phase and two-phase low power two (such as 380V 7.5Kw and common 220V three-phase two-phase 1.5Kw model), 380V high power heat resistance temperature rise, resistance heating time is usually not more than 25 minutes, otherwise easy to damage and high temperature heater heater can not be pulled out, causing leakage electric shock accidents. However, the heating temperature of the 220V resistance heater is relatively slow, but it has the characteristics of uniform temperature rise speed and easy control. The selection of the resistance heater should also refer to the length of the heater and the comparison value of the length of the coupling bolt, as well as the surrounding market.

3.

3.1 smooth lifting shaft and runner (generator spindle) over to a certain height when the alignment flange matching rabbet and a coupling bolt hole through at least four bolts for symmetrical positioning. When the bolt is penetrated, the lubricant is smeared on the contact end of the bolt screw thread and the nut and flange, and the joint bolt is initially tightened.

3.2 use a certain thickness of insulating material to wrap the finishing surface on the spindle to prevent accidental damage by collision and electric welding.

3.3, according to the design elongation and nut rotation angle, the starting line of the corner is clearly arranged on the coupling bolts and nuts one by one, so as to observe conveniently during heating. According to the heating resistor layout and a dial indicator are respectively arranged in the bolt up and down.

3.4 preparation of a special distributor and power supply, according to the number of coupling axisymmetric bolts into four heaters. For more uniform and effective heating of the shaft bolts, a certain amount of thermal couplings should be purchased and applied evenly to the surface of the effective heating section of the resistance heater (mainly on the effective heating section of the heater, and the thickness of the coating should not be too thick).

Initial heating test of 3.5 resistance heater

3.5.1 checks the angle line on the shaft bolts and nuts and the insertion depth of the resistance heater, and starts the initial heating test after it meets the requirements.

3.5.2 will be symmetric in four bolt upper end and lower end of the dial gauge to zero "layout".

3.5.3 also opened the four resistance heater power supply, monitoring bolt, end dial indicator readings, and record the time and elongation of dial indicator bolt design reached thermal elongation values for other bolt heating for reference.

The amount of thermal design elongation difference 3.5.4 bolt for reading the upper and lower end surfaces to bolt the dial indicator (a power plant is 1.23 + 0.04mm) after the power supply is cut off, and with a special spanner rotating shaft coupling nut to the designated angle reticle position.

Remove the 3.5.5 resistance heater, record bolt, dial indicator readings to end bolt after cooling, and calculate the difference between the two, compared with the design value of elongation, meet the design requirements will be recorded. If it does not meet the requirements of the design, a certain correction should be carried out, and the heating test is repeated, and the elongation value of the coupling bolt finally meets the design requirements.

Correction of the elongation of 3.5.6 shaft bolt

C) the actual residual elongation of all coupling bolts should be recorded in detail, L1.

3.6 according to the initial heating test data, the remaining shaft bolts are stretched and the final remaining elongation value and angle are recorded.

4, flange coupling with 0.02mm feeler examination combined with surface gap, should be no gap. The local clearance should be less than 0.03mm, and the measurement situation is recorded in detail.

5, the connection between the main shaft and the runner of the turbine is made. The coaxality of the measuring bracket can be measured by itself. The roundness and the coaxality of the upper and the lower leakage rings of the runner are checked based on the large axis of the turbine, and the deviation should be less than the design gap of the 10% stop ring.


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