Monitoring of pumping system for any type of work, not only in concrete work, is very important as performance of this system depends on monitoring and relevant maintenance of pumping system. It is very common to find worn out pumping system in ready-mix job, requires repair frequently; if valve is worn out excessively; squeezing out of mortar from mix is being pumped may cause plugs.
Some types of valves have to be adjusted to control mortar loss from the valve. When piston heads of concrete cylinder is worn badly, water from water box may get mixed with concrete being pumped through the system which may alter water-cement ratio producing higher slumps and subsequent separation followed by plugging.
Obviously high water-cement ratio produces concrete of low strength. When it is found hydraulic oil is too hot during pumping, the pumping should be stopped and following steps should be taken:
a. Immediately stop pumping
b. Check performance of soil cooler
c. Rapidly locate source of heat generation
d. Make sure water box is filled with water
e. Cold water can be sprayed on oil tank and over all hydraulic system
f. Start pumping after above remedial measure and check temperature with slow pumping
In some type of pump cooler fan may be turned on manually. In locating heat source, the position of outrigger valve/any other valve have to checked, as wrong positioning may produce heat.
If overheating continues, there may have problem with pump like
• Wrong setting of pressure relief valve
• Worn out piston rings
• The hydraulic oil may be of wrong grade
The machine oil should not allow to heat more than 820C. Sometimes gauges for oil temperature may not work properly or out of order, in this situation, a pump operator may get idea about temperature by touching oil tank.
If he can hold his hand on oil tank for 5 seconds, it is considered the oil is not too hot. If he has to remove hand immediate after touching, the oil is considered too hot.
The usual pressure of boom pumps on piston face remains within (700-1000) psi. In case of high-pressure pumps (trailer pumps) this pressure exceeds 2000 psi. It should keep in mind that pressure found in hydraulic system is not the pressure of concrete. The area of head of hydraulic piston should be considered to determine total force and then divided by area of concrete piston head to find concrete pressure.