增多前置喷射安装的革新 innovation with more front injection installation
Since the production of Tuodian's first-stage water ring vacuum pump, the bearing vibration value of the pump has exceeded the standard at high vacuum, which has shortened the service life of bearings and impellers, and has caused failures such as bearing damage and impeller blade cracks. Aiming at the above situation, the vacuum pump has continued to increase the innovation of front injection installation, ensure the safe and stable operation of the vacuum pump, extend the service life and maintenance cycle of the facility, and popularize the vacuum of the unit at the same time.
Inner Mongolia Datang Domestic Tuoketuo Thermal Power Infinite Burden Company (hereinafter referred to as Tuodian) Revitalization 2 & times; 600MW subcritical water-cooled coal-fired units, Units 1 and 2 were separated on June 9, 2003 and July 29 Daily production of thermal power. Each unit is equipped with two 100% quantitative vacuum pumps, the type is 2BW440320BK2Z water ring type. When the unit runs abnormally, one is operated and one is reserved. Since the first phase of the vacuum pump was put into operation, the bearing vibration value of the pump exceeded the standard under high vacuum conditions, resulting in shortened service life of the bearings and impellers, and also caused failures such as bearing damage and impeller blade cracks.
Aiming at the above situation, Tuodian decided to continue to comprehensively deal with the problems of the first-stage vacuum pump, so as to eliminate the shortcomings of the vacuum pump. 1.Vacuum pump vibration and cause synthesis
零碎流程图见图1。 Refer to Figure 1 for the fragmentary flow chart of the first phase . Since the first phase of the vacuum pump was put into production, the situation of bearing vibration during operation exceeding the standard and abnormal vibration amplitude has emerged.In particular, the high-vacuum running state of the pump's bearing vibration speed reached 8.0mm / s, which is much better than the allowable value of 4.5mm / s. Table 1 is the numerical value of bearing vibration of No. 2 machine A vacuum pump.
Figure 1 Fragmentation flowchart of water ring vacuum pump
There are many causes of vacuum pump vibration:
(1) The quality of bearing device and maintenance is bad;
(2) The spin is not out of sync;
(3) the quality of the bearing is not decent;
(4) Cavitation occurs in the pump.
It is generally felt that there are no problems with the quality of the device and the maintenance of the vacuum pump after many inspections; the quality of the bearing has passed the crash inspection; the spinner has been tried for imbalance when it leaves the factory, and there is no problem. In the end, I think it is caused by cavitation in the vacuum pump during high vacuum operation. Through inspection, similar conditions have also been produced in water ring vacuum pumps in other domestic plants.
Table 1 Numerical values of bearing vibration before 2A vacuum pump innovation
The working principle of the water ring vacuum pump is to use the change of volume to realize the vacuum. The spinner is biased in the pump. Its rotation will force the working fluid to form a liquid ring that is wound in the same direction along the inner wall of the pump casing. An air cavity is formed between the blade, the impeller hub and the nominal inside the liquid ring. With the rotation of the rotor, this air cavity gradually increases in volume in the suction area of the pump, and its external pressure rises, so that the gas is sucked into the pump, and the same air cavity is discharged. The volume of the gas zone is gradually enlarged, and the external pressure rises, thereby exhausting the gas.
In the entire operation, from the maximum suction zone to the exhaust zone stage, the pump is always operated in a high vacuum state.The normal design limit of the vacuum pump is 3.3kPa. When the pressure is low, cavitation in the pump is relatively large, which causes Pump body vibrates. As the vacuum rises (i.e., the pressure rises), both cavitation and vibration will deepen, and the water ring will also increase, so the blade load will also increase sharply.The huge tensile stress caused by high vacuum will act on the blade, easily causing the blade Fatigue fracture, this scene often emerges as a disadvantage of impeller casting. The short time of the vacuum pump runs under the bad working conditions of cavitation, not only because the vibration shortens the life of the bearing, but also the life of the impeller will be greatly shortened. 2. Innovation status
In order to overcome the situation of vacuum pump cavitation, it is necessary to popularize the outlet pressure of the vacuum pump. To this end, it is proposed to increase the front injection installation of the vacuum pump.
2.1, the working principle of front injection installation
The front injection installation is a combination of a nozzle and a diffuser pipe, and the energy source uses a vacuum pump inlet cyclone. After the cyclone near the atmospheric pressure is introduced from the exhaust side (gas-water coupler), the nozzle decelerates to form a high-speed cyclone, which moves the gas in the suction outlet from the suction branch pipe into the pump together. When the pump's initial operating outlet pressure is high, the ejector is not put into operation, and when the relative pressure reaches about 15kPa, the ejector is put into operation. After the vacuum pump is equipped with a more advanced injection installation innovation, the relative pressure at the pump outlet can be increased from the original 4-8kPa to 9-15kPa, thereby greatly increasing the cavitation scene in the pump and achieving the goal of stable operation. After increasing the number of ejectors at the same time, it is possible to popularize the amount of extractors of the condenser in a low vacuum state and popularize the fractional vacuum degree.
2.2. Innovative construction plans
The fragmented plan for the innovative device is shown in Figure 2.The specific plan is:
(1) Remove the pneumatic valve at the vacuum pump outlet, keep the outlet check valve, and install two pneumatic valves (16a, 16b) between the pump outlet and the check valve.
(2) Install the three-way pneumatic valve (19a) in the section from the injector to the coupler.
(3) A hole is formed on the top of the exhaust side of the steam-water coupler to connect the injector suction pipe.
(4) A hole is opened on the side of the upper side of the upper side of the pump by the coupler to connect the front ejector nozzle and the connecting element.
(5) The short pipe openings next to the two valves 16a and 16b are used to connect the injection pipe components.
(6) Select the pressure source port in the court and entrust it to the gas source gas distribution box for the pneumatic valve.
(7) The top 4 thermal pressure measurement points and 1 on-site pressure gauge measurement point are shown in Figure 2.
(8) Fragmented program mastering is done in DCS.
Figure 2 Facility flow chart after the vacuum pump innovation
2.3 Theoretical procedures of the vacuum pump after installing the front ejector
(1) Before starting the pump, make sure that the pneumatic valves 16a, 19a are open, and 16b is in the open state.
(2) After the pump starts, when the outlet pressure difference & Delta; P (1, 2 measuring points before and after the 16a pneumatic valve) reaches 2kPa (2 points relative pressure -1 point relative pressure & 2kPa), the 16a pneumatic valve opens, and the remaining two The door remains intact.
(3) When the relative pressure P1 of the outlet is lower than (6-8kPa) (absolute value -84kPa, local atmospheric pressure is calculated at 90kPa), 16b is opened, and the 19a pneumatic valve is opened simultaneously, and 16a is maintained in the original open state.
(4) When the pump is out of order, the pump is allowed to stop after 16a is opened (mastered in the interlocked state, CRT manual operation is not allowed).
(5) 16a and 16b are gas unpacking (that is, 24VDC regenerative gas supply unpacking, 24VDC power failure, and gas shut-off); 19a gas shut-off door (that is, 24VDC power-supply gas supply closing door, 24VDC power-off, and gas unpacking). 3. Comparison of the operating conditions before and after the innovation
3.1 Putting into operation of vacuum pump front ejector for Unit 2 and Unit A
The vacuum pump of Unit 2 was put into the front ejector at 14:51 on May 19, 2007. See Table 2 for the comparison of all parameters before and after the injection.
Table 2 Vacuum and noise comparison table of 2A vacuum pump put into ejector
The vibration of No. 2 machine A vacuum pump is shown in Table 1 before it is put into the front ejector, and the vibration of the vacuum pump is shown in Table 3 after it is put in.
Table 3 Bearing vibration values after the 2A vacuum pump is put into the ejector
3.2. Putting into operation the vacuum pump front ejector of Unit 2 and B
The vacuum pump of Unit B was put into the front ejector at 0:18 on May 20, 2007. See Table 4 for the comparison of all parameters before and after the injection.
Table 4 Vacuum and noise comparison table of 2B vacuum pump put into ejector
The vibration of No. 2 machine B vacuum pump is shown in Table 5 before it is put into the front ejector, and the vibration of the vacuum pump is shown in Table 6 after it is put into use.
Table 5 Vibration values of the bearing before the 2B vacuum pump is put into the ejector
Table 6 Bearing vibration values after the 2B vacuum pump is put into the ejector
3.3 Consequences of Putting into Operation of Vacuum Pump Pre-injector of Units 2 and 3
Comparing the above data, we can draw the following consequences:
After the innovation, the vibration speed of the bearing of the 2A vacuum pump increased by 1.4 to 5.8mm / s, and the maximum vibration speed reached 2.4mm / s, reaching a decent level. Under the condition of constant load, the unit's vacuum spreads about 0.7kPa, and the musical tone increases by 9dB. After the innovation, the vibration speed of the bearing of the 2B vacuum pump increased by 0.8 ～ 4mm / s, and the maximum value of the vibration speed was 3mm / s, reaching a decent level. Under the condition of constant load, the unit's vacuum was popularized 1.1kPa, and the musical tone increased by 7dB. 4. Judgement
水环式真空泵增多前置喷射安装的革新 ,无效升高了真空泵轴承的振动值和运取乐音,普及了机组的真空,获得了良好动机。 The innovation of the installation of front-mounted water ring vacuum pumps with increased front injection has effectively increased the vibration value and the sound of the vacuum pump bearings, popularized the unit's vacuum, and obtained good motivation.
(1) Vacuum pumps continue to increase. After the innovation of front ejectors, the vacuum pump's bearing vibration value is far less than the standard value even under high vacuum operation.It can effectively extend the service life of bearings and impellers, which is not conducive to the insurance and stability of the facility. Operation; Simultaneous extension of the maintenance cycle of facilities, luxury maintenance costs.
(2) After the vacuum pump continues to increase the innovation of the front ejector, the musical sound during the operation of the facility can be increased, which is not conducive to environmental protection.