Balance test of casting impeller

1. Selection and determination of detection method

As a key part of the pump body, the impeller of desulfurization pump rotates around the main shaft at high speed when the pump is running. In order to make the pump run smoothly, it is necessary to make the balance quality of the impeller meet the design requirements. If the balance quality of the impeller is too large, it will cause large vibration, high noise, bearing damage, efficiency reduction, current instability and abnormal sound of the pump when the pump is running.

At present, there are two methods to measure the balance: dynamic balance and static balance. The so-called static balance refers to the state in which a mass is placed or removed on the correction plane to achieve static balance. The value of mass is the static balance. Dynamic balance refers to the balance correction on both sides of the rotor to achieve the required balance state. The corrected residual unbalance is within the specified range of allowable unbalance, which is dynamic balance.

According to gb9239: if the support space of disc rotor is large enough and the axial runout of disc part is small when rotating, so the dynamic balance can be ignored, then a correction front can be used to correct the imbalance, i.e. static balance. It is necessary to verify whether these conditions are met for the specific rotor. After balancing a certain type of rotor on a plane, the maximum residual unbalance can be obtained and divided by the support distance. As long as this value is not more than half of the allowable residual unbalance, static balance is sufficient.

For this impeller, the static balance method is mainly used to measure its balance.

2. Static balance test and results of desulfurization pump impeller

For the impeller of desulfurizing pump, the mandrel is used for positioning, and it is installed on the test stand to make the rotating impeller. If the mass center of the impeller is not in the vertical plane including the rotating axis, the mass center is at the bottom when the rotation stops, so that the deviation direction of the mass center can be determined, the unbalanced position can be found, and the deviation direction of the mass center can be marked. Then try to add an appropriate balance mass in the opposite direction. At this time, the added balance mass is the same as the unbalanced mass of the impeller. The impeller shall be balanced by the weight removal method, but the cut thickness shall not be greater than 1 / 3 of the wall thickness, so as to achieve the static balance of the impeller.

According to the requirements of the standard, the unbalance mass of the impeller of the desulfurization pump is less than 80g. In order to meet the balance requirements, the worst removal weight of the impeller made by the combined sand core process in Shijiazhuang industrial pump factory is 5500g, which brings great difficulties to the subsequent machining. However, the impeller produced by the integrated sand core made by the EPC sand mold composite process has a removal quality of 1200g through static, horizontal and horizontal tests. It can be seen that the balance performance of the impeller produced by the new technology has been greatly improved.

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