The 32-meter pump truck boom, especially the plates of the first few arms connected to the turntable, generally use high-strength steel plates. When high-strength steel plates ensure yield strength, some indicators such as plasticity, ductility, and weldability are reduced, especially during welding. The thermal stress affected zone formed during the welding process causes the strength of the weld and surrounding areas to decrease.

When the concrete pump truck is in construction, the distribution arm is unfolded, each section of the distribution arm and the hydraulic cylinder of the outrigger are locked, and the entire distribution arm system forms a cantilever beam structure. The boom of the concrete pump truck adopts an R-shaped structure. After the two-section arm, there are three or four-section arms. The three-section arm also adopts a bending structure, and the two-section arm has to bear a certain torsional load. At the same time, when the concrete pump truck is working, the two pumping hydraulic cylinders alternately circulate to continuously press the concrete to the pouring position. Due to the alternating action of the two pumping cylinders, the concrete pump truck is subjected to a forced impact with a certain frequency. Under the impact of the pumping cylinder, the vibration of the cloth arm is amplified, so the cloth arm is subjected to alternating loads, causing fatigue damage.

The wear of the pins and copper sleeves caused the impact force at the tail of the cloth arm. During the inspection, it was found that three pins and six copper sleeves were worn, and the two pins and copper sleeves in the same group had inconsistent wear degrees.

There is stress concentration at the bushings at the roots of the two-section arms. According to the qualitative analysis of the root of the arm of the previous 37m similar pump truck, there is obvious stress concentration on the lower side of the bushing. The high-strength plate used as the boom plate has good toughness and plasticity, and the initial crack tip yields locally in a small area under the action of high stress concentration area and residual force. In this case, the action of alternating loads gradually propagates microcracks.

Pump trucks basically operate in an open-air environment. Due to long-term erosion by corrosive media such as rainwater and hydrogen sulfide in the air, oxidative corrosion is caused and local strength is reduced.

Due to the highly comprehensive equipment of the pump truck, local cracks and fatigue cracks cannot be completely avoided. Sometimes even basic maintenance, such as oiling between the pin shaft and the copper sleeve, is not performed, let alone overall maintenance. Sometimes a little crack is not terrible, as long as it is repaired or strengthened. If it is not discovered, or if measures are not taken in time, the crack will expand, which may eventually lead to structural damage or even an accident. The damage to this pump truck illustrates this problem.

The above is an extended analysis of a maintenance problem of the concrete pump truck boom and the reasons for fracture that Saintyol DAWIN has summarized for you. Long-term use will inevitably cause a series of problems, which requires us to Only by paying more attention can the service life of the pump truck be better extended.