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Selection of concrete pumps At present, for the general construction side of the material used by the bone size and construction speed selection of concrete pump selection, is the so-called by the amount of food put, and for high-rise building pumping construction generally use high-pressure pump or pump to the top to fulfill.
Relay pumping is the delivery of concrete through a concrete pump to another concrete pump hopper that has been placed at a certain height in advance, and then the concrete is delivered to the destination via a second transfer pump; this solution is economical and reliable; Say, the requirements of the pump is not too high, at the same time, after the completion of the project, these pumps can be economically used in other general construction; the disadvantage is that the construction is more complicated, the construction of the first pump and the second pump should be coordinated; The second pump to be fixed to do special treatment, taking into account the carrying capacity of the floor can meet the requirements. The pumping method is used in the early days of early concrete pumping machinery. As the concrete pumping machinery and related technologies become more mature, the solution is gradually replaced by a pump-to-ceiling solution.
A pump to the top is the use of ultra-high pressure concrete pump directly to the destination of concrete delivery; The program has the advantages of simple construction, low construction costs, but the program pumping pressure is too high, prone to leakage leading to concrete segregation, plugging and many other The problem, therefore, places great demands on the pumping equipment, the concrete delivery pipelines and the pumping construction process; at the same time, the pump is less economical for other general projects once the project is completed.
According to the comprehensive consideration, the case chooses a pump topping scheme, that is, only one pump is used to pump the concrete to the destination. The scheme is very demanding and representative for the pumping equipment.
EHV concrete pump selection is generally based on job requirements to estimate the pipeline resistance, according to the calculated pressure value of primary concrete pump model, and finally according to the manufacturer to provide the demand for the amount of construction, to confirm the pumping pressure (which determines the pumping height) , The theoretical amount (determines the pumping time) to meet the construction needs. If you meet the demand, model to determine, if you do not meet the needs of the re-selection of models. So repeatedly until the selected model to meet the requirements so far, the flow chart shown in Figure 1.
(1) Pumping pressure estimation.
At present there is no mature method for estimating the pressure of high-strength and high-performance concrete pumping. We first estimate the pumping pressure based on the three methods of traditional pumping pressure estimation (that is, S. Morinaga formula method, calculation graph method, Japan Civil Engineering Society formula method) and the S. Morinaga formula method. The reason is that the formula to calculate the pressure loss value is too large, in line with high-strength high-performance concrete with large resistance characteristics.
According to the calculation method recommended by JGJ / T10-95 Technical Specification for Concrete Pumping Construction, the formula of S. Morinaga with higher pressure loss is selected [1]:
Where: r-pipe radius r = 0.0625 (m)
K1 = Cohesion coefficient (Pa) K1 = (3.0-0.10S1) .102
K2 = speed coefficient (Pa / m / s) K2 = (4.0-0.10S1) .102
t2 / t1 - distribution of switching time and the ratio of piston push concrete time, take 0.2
V-average velocity of concrete in the duct (m / s)
α-concrete radial pressure and axial pressure ratio, α = 0.9
According to the calculation: â–³ PH = 0.035MPa / m (level)
Preliminary calculation:
It is known that the vertical height is 432.5 (m) × 2 × 0.035 = 30.28 MPa
Expected: Horizontal pipe 100m × 0.035 = 3.5MPa
Empty machine pressure: 1MPa
Therefore, the outlet pressure of concrete pump at least greater than P> 30.28 +3.5 +1 = 33.78MPa
(2) equipment model primaries.
According to the above calculation, taking into account the slump loss, piping, concrete fluctuations and other factors, set aside 5% of the coefficient. Pump outlet pressure of at least 35.47 MPa; that is, to choose more than 35.5 MPa concrete pump. For the outlet pressure exceeds 35.5 MPa, consult the concrete pump type spectrum at home and abroad,
(3) equipment model to determine.
For most projects, there is a requirement for the construction speed, so when choosing a pumping equipment, the concrete output capacity of concrete should be considered.
Concrete pump selection