Centrifugal pump base grouting: A crucial step to ensure the long-term stable operation of the pump.

In the centrifugal pump industry, customers generally pursue two goals: first, ensuring the pump operates reliably over the long term, and second, achieving economical installation costs. The core function of the baseplate is to provide a stable support surface for accurately aligning the pump and the drive unit. It not only ensures precise alignment between the two but also provides the necessary path for the transmission of vibrations, nozzle loads, and pipe forces. If the baseplate is improperly designed or installed, all alignment efforts may be rendered useless during the initial stages of pump operation. Conversely, correct baseplate installation will maintain this critical alignment and yield long-term economic benefits by reducing maintenance costs.

 

 

• Installation Requirements and Cost-Effectiveness

Generally, the lower the pump's power, the less need there is for expensive installations (such as foundations, bases, and grouting). However, some companies may choose the cheapest base and place it directly on the floor or ground, simply connecting the pump's inlet and outlet pipes and electrical connections. This approach might be suitable for low-power pumps operating in low ambient temperatures and for short periods. But in the long run, any pump system intended for proper installation with overall and long-term value should seriously consider alternatives such as pre-grouted pump bases.

 

 

Due to a lack of specific standards, pump and baseplate manufacturers typically do not specifically prepare the baseplate underside for the grouting process. However, the following key questions should be considered: When was the baseplate last turned over and the grouting surface prepared? Have the pump and drive unit been removed?

Ideally, the baseplate underside should be sandblasted and installed within a short period (ideally within 8 hours in a controlled environment) to ensure a strong bond with the grout. Another option is to apply a suitable epoxy coating to the baseplate underside to serve as the bonding surface for the grout. Grout manufacturers will provide specific recommendations regarding surface preparation and paint.

 

During the grouting process, the pump and drive unit should be removed from the base. Before removal, carefully verify that the equipment can be properly aligned and ensure the base is flat and coplanar. The concrete foundation must be fully cured before installation and grouting. The curing time for a new foundation will vary depending on environmental conditions and the concrete mix used.

Additionally, when installing the base on a new or existing concrete foundation, the laitance must be removed to a depth of at least half an inch. Avoid using a hand hammer when removing the laitance to prevent concrete cracking. A small, lightweight pneumatic hammer with a sharp tip is recommended.

 

It is important to note that the curing of epoxy resin grout is affected by temperature. If the ambient temperature is too high or too low, appropriate measures should be taken to adjust or control it, such as setting up temporary insulation or shading facilities. Furthermore, it is crucial to ensure that the equipment is protected from rain during the curing process.

 

Anchor bolts are crucial connecting elements between the foundation and the base plate. They pass through the through-holes in the base plate and not only provide fixation but, more importantly, tightly connect the foundation, grout, and base plate together. During the grouting process, the anchor bolts exert tension on the base plate, effectively preventing it from floating. To ensure smooth operation and prevent grout from entering unwanted areas, a certain gap should be maintained between the anchor bolts and the grout. This can be achieved by using protective sleeves/tubes.

 

Before grouting, many people are accustomed to using wooden or metal shims to level the base and leaving the shims in place. However, this may not be the best option. Shims are prone to corrosion, while leveling screws provide more precise adjustments and can be removed after grouting. For easier removal, it is recommended to apply a light grease to the shims.

 

Before starting the grouting process, the primary task is to decide which grouting method to use – whether to do it in two stages or in a single step. I personally prefer single-stage grouting, especially when using epoxy resin grout. Single-stage epoxy resin grouting is recommended, with appropriate vent holes to ensure air release.

 

During the grouting process, the stability and impermeability of the formwork are crucial. Attention must be paid to the stability of the formwork, the accurate measurement of materials, and their smooth flow. To prevent grout adhesion, a substance that does not react with the grout, such as paste wax, is usually applied to the formwork, typically in two to three layers.

During grouting, it is essential to ensure proper air venting. Because base components and supports may hinder proper installation and venting, vent holes with a diameter of at least 13 mm should be provided at the highest point of each section (panel) of the base, as specified by API 610 standards.

 

Grouting is crucial for the stable operation of the pump. Proper grouting ensures a secure base, thereby extending the pump's service life. Therefore, mastering the correct grouting techniques and understanding the relevant operating procedures is extremely important.