MH-type gantry crane girder deflection detection of the three methods

MH-type gantry crane girder deflection detection of the three methods

In  bridge gantry crane  safety and technical inspection, the main beam camber detection is a very important element. JB1036-82 (Universal bridge crane technical conditions) clearly states: the main beam span camber F = L (0.9-1.4) / 1000. And the maximum camber should be controlled in the middle of the span L/10 range. The most commonly used method for detecting gantry crane with traditional pull wire hook hanging foot laws and existing laws, as well as a magnet hanging ruler France.

1, drawn steel wire method

Pull wire method requires three inspectors must climb the crane main beam, so that φ0.5mm of a thin steel wire fixed on one end of the main beam (wire through the cover plate contour block), and the other head and another girder 15kg spring balance connected at one end. Then select the measuring point, measuring wire to the vertical distance between the surface of the main beam, and then calculate the camber values. This method has great limitations and testing personnel climbing operation risk, applies only to part of the box-shaped double girder  overhead gantry crane  girder camber testing, not suitable for single-girder bridge (the door) and a crane with a skirt The box-shaped double girder bridge crane girder camber testing.

2, hook hanging ruler France

Hook hanging scale method is to 300mm steel ruler upside down on a hook, start the car (electric hoist) along the beam orbit, through the erection on the ground water level, measured in turn take the main beam elevation value of each point. Then calculate the camber values. This measurement error is large, it may sometimes come to the opposite result. Factors affecting the measurement accuracy is: Trolley wheel tread radius error and orbital shape error as well as other car three legs will be directly reflected in the elevation value, causing the elevation value measurements taken untrue, the final calculated value will not camber accurate .

3, the magnet hanging ruler France

Magnet hanging foot method of 0.5m with a thin wire, one end fixed to the magnet, and the other end fixed to a weight of 0.5kg. The fine wires can be adjusted on the location of installation of a steel ruler 300mm, with a special insulated rod magnets in the main beam to the cover or the lower surface of the beam track. Then select the main beam and the beam ends the three measurement points, through the erection on the ground water level reading on the ruler hanging by a magnet values ​​to calculate the arch girder span value. That is the main girder span camber value = Cross winning high value -1 / 2 (the higher end of the value + cross side elevation cross-over bottom side elevation values).

Steel ruler fixed on the thin wire on the positive, the measured result is positive for the upper arch, and vice versa for the next scratch. With this method can detect various types of hoist gantry crane  girder camber, method is simple, accurate, saving time and effort.