Preparatory work and foundation construction before installing the water pump unit

Preparatory work and foundation construction before installing the water pump unit

1. Preparatory work before installing the water pump unit

Before installing the centrifugal pump unit, detailed verification work should be carried out, mainly including whether the plane position of the water pump unit installation and the vertical elevation of each part meet the design requirements; verify whether the plane position and elevation of the reserved holes at the wall penetration positions of each inlet and outlet pipe meet the design requirements; verify whether the elevation of the top surface of the water pump unit foundation meets the design requirements.

To ensure the installation quality of the unit, the quality of the water pump, matching motor and various accessories should be carefully checked before installation. Disassemble and inspect the water pump, motor and various accessories, clean them, and reassemble them for installation.

The installation work must be carried out according to the design drawings. The installation position and installation height must meet the design requirements. However, if there are problems with the design during installation, they must be solved on site in a timely manner.

2. Foundation construction

The function of the water pump foundation is to support and fix the unit so that it runs smoothly without violent vibration, and foundation subsidence is not allowed. Therefore, the requirements for the foundation are: (1) solid and firm, in addition to being able to withstand the static load of the unit, it can also withstand mechanical vibration loads; (2) it should be cast on a relatively solid foundation, and should not be cast on a soft foundation or new fill to avoid foundation sinking or uneven settlement. Generally, medium and small vertical axial flow pumps are installed on reinforced concrete racks or special pump beams; while horizontal centrifugal pumps are mostly installed on concrete block foundations.

1. Concrete foundation

The concrete foundation should have sufficient plane dimensions to ensure the installation and fixation of the pump. Its size is generally determined according to the data provided by the selected pump installation size. For specific determination methods, see the relevant content of Section 2 of Chapter 4.

During foundation construction, it is required to dig a machine pit at the specified location first, lay a 5cm thick layer of gravel or broken bricks underneath, compact it with a tamping machine, and then pour concrete. The mix ratio of concrete can be calculated by mass. Generally, it is 1 part cement, 2 parts yellow sand, and 5 parts gravel. Or 1 part cement, 2 parts yellow sand, 4 parts gravel, or 1 part cement, 3 parts yellow sand, 6 parts gravel. Which mix ratio to use can be selected according to the importance of the building and the quality of cement. The quality of water is 40% to 60% of the quality of cement. The less water added, the higher the strength. When pouring, the formwork should be placed near the ground and above the ground, and the formwork should be nailed according to the size of the foundation.

2. Fixing of the base screws

The fixing of the anchor bolts of the unit base is divided into one-time casting method and two-time casting method.

The one-time casting method is to fix the anchor bolts on the model frame before pouring concrete. When pouring concrete, there is no need to reserve bolt holes. It is poured in one time and the anchor bolts are cast in the concrete foundation. This method is usually used for the installation of small water pumps with bases. The advantages of this method are shortening the construction period; enhancing the stability of the base screws in the foundation; and ensuring the installation quality. The disadvantage is that if the anchor bolts are not fixed correctly or the casting anchor bolts are displaced, it will bring difficulties to the installation of the water pump unit.

The foundation of small water pumps generally adopts the one-time grouting method. Usually, the formwork is set up with wooden boards or bricks according to the specified size requirements, and the vertical and horizontal strips with screw holes are nailed at the position of each foot screw to fix the position of the foot screw, and then the concrete is poured.

The secondary pouring method is to reserve the anchor bolt holes in advance when casting the concrete foundation, and pour concrete into the reserved pouring holes after the water pump unit is in place and the bolts are tightened. The disadvantage of this method is that it increases the workload of the foundation formwork project and pouring, and it is poured twice. The concrete that solidifies before and after is sometimes not well combined, affecting the stability of the foot screw.

In the installation of medium and small water pump units, in order to avoid the shortcomings of the above method, high-strength refractory bricks can be used to pad the four corners of the base, and then the anchor bolts are placed, the formwork is supported, and the concrete foundation is poured at one time.

When using the secondary grouting method, the formwork must be set up in advance, and the reserved hole template must be set up at the position of the foot screw. The size of the reserved hole is generally about 5cm larger than the diameter of the foot screw. If you don't use a reserved hole template, you can also put an iron pipe or bamboo tube with a diameter 1.5 to 2 times thicker than the bolt diameter on the outside of the base screw, and fix the base screw on the template frame. Allow the base screw to move slightly to facilitate alignment with the base screw hole on the base.

Large water pump units usually do not have a base. In order to facilitate the installation and leveling of the unit, channel steel is often used to make an integral base. When pouring the concrete foundation, one or two pouring methods are used to stabilize the steel unit base in the designed position. The advantage of this construction method is that the steel base is more firmly combined with the concrete and has better integrity.