With the development of my country's industry, the scale of many enterprises has continued to expand, and the boilers that provide power sources have also increased. In the non-boiler industry, there are few people who are proficient in boilers, and even fewer people are proficient in boiler auxiliary equipment. This brings certain difficulties to the company in the selection of boiler auxiliary equipment. In order to avoid large deviations in the actual application of the selected equipment, the following only proposes a few simple types for the selection of boiler water pump models. Applicable methods and precautions.
(1) For the seal of the rotating shaft, use mechanical seals as much as possible, especially for boiler feed water pumps. If packing seals are used, although maintenance is simple, the failure rate and maintenance frequency are high and the workload is large, so mechanical seals should be selected, and the service life should be greater than 8000h .
(2) The water pump motor on the boiler is the power source for the operation of the water pump. If the motor fails, the water pump cannot operate. Therefore, the structure and insulation level of the motor should meet the requirements of the installation and use environment temperature to ensure the safe operation of the motor.
(3) If the frequency conversion water supply is selected, the selected pump head should be slightly higher than the design value H. Because the pump is running for 3~5a, the head will drop by 20~30m due to the wear of the impeller and the expansion of the gap, so it should be about 30% higher than H to ensure that the pump can still supply water normally after many years and put the inverter into the good energy-saving effect. The service life of the pump.
(4) The material of impeller, sealing ring and balance plate should be HT200 or higher (such as HT250 and HT300, etc.).
(5) If the feed water temperature is normal temperature, it can be used when selecting
Special instructions; but if the water supply temperature is >100℃, the water supply temperature should be emphasized when selecting the water pump, because the high temperature pump and the low temperature pump have different materials, structure and anti-cavitation function.
Determination of parameters for model selection of boiler feed water pump
(1) Calculation of feed water pump flow:
Q=k(Q1+Q2)
In the formula, Q is the flow rate of the boiler feed water pump, m3/h;
Q1 The total water supply at the maximum steam load of a boiler, m3/h;
Q2 Other water consumption, such as continuous blowdown, regular blowdown and desuperheater, m3/h; k standby coefficient 1.1~1.2ε
(2) Boiler feed pump lift calculation
H=H1+H2+H3+H4
Where H is the head of the boiler feed pump m
H1—The opening pressure of the safety valve of the boiler under the designed pressure, MPa;
H2—The resistance of the economizer and water supply piping system MPa
H3—The difference between the highest and lowest water level of the water supply system MPa
H4 One other.
(3) The upper water pump should be set to standby. When the largest feed water pump stops running, the remaining total flow should be able to meet 110% of the required feed water volume of all operating boilers at the rated evaporation; when the boiler room is equipped with a desuperheating device Or the total flow of the feed water pump in the case of a heat accumulator should be included in its water consumption.
(4) One or more boilers with the same steam pressure can choose two or more feedwater pumps to operate in parallel. If the main pipe is used for water supply, you can choose two pumps, one for use and one for backup, and then variable frequency water supply, which not only reduces The consumption of electric energy also makes the water supply pressure stable. Although the one-time investment is relatively large, through frequency conversion energy-saving measures, the investment cost can be recovered in 3 to 4 years.
(5) The use of steam-driven feedwater pumps as emergency backup pumps should have a flow that can be 20%-40% of the required feedwater for all operating boilers at the rated evaporation capacity. The steam-driven feedwater pump can only be installed when the boiler room and feedwater pump with the first-level electric load stop running and will not cause water shortage in the boiler. The non-power station boiler rooms of general industrial enterprises do not have such conditions and must be installed.
