Joined: Oct 21, 2015
| Posted: 2019-04-28 21:42|
In the course of concrete pump truck commutation, concrete flow often appears obvious phenomenon of flow-break-flow, which is commonly referred to as the phenomenon of flow-break.
There are three reasons for the phenomenon of flow:
When the main cylinder runs close to the end of the stroke, it sends out the reversing signal to the reversing cylinder, and then the main system oil circuit changes direction. The main cylinder moves in the opposite direction, which takes at least 0.2 seconds.
(2) When concrete is sucked into a concrete cylinder, the suction efficiency is usually only 85%-95%. Inevitably, a small section of air will be sucked in, which will be a short empty journey.
(3) When reversing, the pressure of the concrete inhaled from the concrete cylinder rises when it is exported, which has certain compressibility, and this is also a short empty journey. Because of the commutation and two empty travel time, the concrete pump truck appears, so the concrete pump truck has the problem of break-off in the process of concrete pumping. Continuous pumping of concrete is realized before the concrete pressure in the pipeline and distribution valve is fully released, so as to minimize the backlash of concrete pressure released in the pipeline and distribution valve during the process of concrete separation due to break-off and reversal. By choosing and setting the control mode of the main oil pump, the problem of interruption flow in concrete transportation can be effectively solved, the reversing impact can be reduced, and the pumping performance of concrete can be greatly improved.
At present, concrete pump trucks generally suffer from concrete cut-off phenomenon at the moment of pump commutation. This phenomenon has two major hazards. One is easy to cause concrete segregation, some concrete dewatered into dry hard concrete, which causes blockage and cut-off phenomenon. This is especially true when pumping concrete with low slump.
The second is the release of concrete pressure in the pipeline and distribution valve at the moment of reversal, which will impact the hydraulic system of concrete pump, cause damage to some parts and increase energy loss. Cut-off is very harmful to vertical upward pumping, especially to the height above 50m.
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