Find out what the most common problems are in the casing and impeller of motor pumps and the most common causes to try to avoid them.
(Eduardo Terres Secco – Engineering and Technical Sales)
As mentioned in pprevious ost, a significant part of the malfunctions of a motor pump come from inadequate model selection and also from incorrect installation and maintenance of the equipment. Inadequate specification of the motor pump and the materials that make up the entire pumping system can often cause irreversible damage to the equipment.
Let's bring here some of the problems most common in carcass and rotor and the motor pumps that impact the operation or cause the equipment to stop. We will also present the most common causes that may have generated such situations. It is worth informing that the problems we will present were those most commonly encountered, according to a survey carried out by the ATechnical assistance from FAMAC.
Follow along with us!
In the carcass
Carcass breakage can be caused by several situations. The most relevant problems as well as their most common causes are presented and illustrated below.
- Wear on the casing: can occur as a result of cavitation, abrasion, chemical attack, presence of foreign bodies or pumped liquid with excess solids.
- Cracks in suction or pressure: resulting from the use of inadequate connections, excess thread sealing tape or the use of excessive force when tightening.
- Breakage of the coupling or crack in the casing wall: due to piping that is poorly fixed, misaligned or supported on the motor pump, due to the high impact after the motor pump falls, freezing of the pumped liquid, work above the permitted pressure or water hammer.
Below you can see images that show carcasses with wear, cracks and breaks.
On the rotor
A rotor can stop working properly and even burn out and this can be caused by different factors. The most relevant highlighted and illustrated below.
- Worn or unbalanced rotor: may have been caused by cavitation, abrasion, chemical attack or corrosion. Also, due to the presence of foreign bodies or excess solids in the pumped liquid.
- Loose rotor: caused either by working with a reversed direction of rotation or by water hammer.
- Dragging or locked impeller: may be due to oxidation, shaft warping, or the presence of foreign bodies inside the pump. It can also occur due to a lack of lubrication in the bearing or it being damaged by wear or moisture.
In the images below you can see worn or unbalanced, loose or locked rotors.
Motor pumps driven by electric motors
In these cases, the main care to be taken is regarding their rotation, ensuring that they are rotating in the right direction, according to the design. Operation with an incorrect direction of rotation may cause damage to the pump and other equipment, as well as failure to provide the pressure and flow required by the system.
There is a wide range of problems that can, as a result, cause damage to the engine and cause it to burn out. The main problems and their causes are presented for both single-phase and three-phase electric motors, through materials developed and published by WEG, one of the main suppliers and partner of FAMAC, a global reference in the manufacture of electric motors.
Another place where problems can occur and impact the functioning of a motor pump is in the mechanical seal, but so as not to go on too long, we will leave this topic for the next post.
It's worth remembering that you can access some really cool (and very didactic) content about bombs and motor bombs in the booklet that you can download herei.