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Picture comparison of d-type pump and self-balancing multi-stage pump

11 Apr 2021Email

Picture comparison of d-type pump and self-balancing multi-stage pump

The d-type pump is a horizontal single-suction multi-stage segmented centrifugal pump, using a balance disc device, referred to as the old-fashioned multi-stage pump (traditional ordinary multi-stage pump), the self-balancing multi-stage pump is our company summed up many years of independent multi-stage pump production experience The new generation of multi-stage centrifugal pump developed and produced, as an alternative to the traditional d-type multi-stage centrifugal pump, compared with the d-type centrifugal pump, the self-balancing pump has a great improvement in various performance parameters.

photo of d type multistage pump

 

 

The impellers of the traditional d-type horizontal multistage centrifugal pump are arranged in the same direction, and the axial force of each impeller is in the same direction. In order to balance the axial force, a special balance mechanism is set up, which includes a balance plate and a balance ring. (Balance ring sleeve), balance tube. Old-fashioned multi-stage pump: the shell is made of ordinary cast iron, the shaft is made of 45#, the impeller, guide vanes, etc. are all used HT250, the mouth ring, guide vane sleeve, balance disc, balance ring uses QTMn

 

Disadvantages of d-type multistage centrifugal pump:

The balance system is prone to failure: due to the axial movement and the structure of the system, the balance disc and the balance ring, etc., mutual friction and wear are caused, which promotes the impeller to move to the water inlet end (commonly known as leaning to one side), aggravating the impeller and the orifice ring, the impeller and the The friction of the guide vane and the middle section; as the running time increases, the balance effect gradually decreases, forming a vicious circle.

The pump efficiency is low and the parameters do not meet the standard: the actual working condition parameters of the pump do not meet the design requirements. Under normal circumstances, the actual parameters of the water pump can only reach 80-85%. For example: D155-67X9 multi-stage pump, at rated head, the flow is only 133m3/H (22m3/H less than the design flow).

Short trouble-free running time and high maintenance cost: The running time is short and the balance plate, gimbal and rotor components need to be replaced frequently; the cost of parts alone can reach 40-50% of the equipment purchase cost without calculating the loss of production shutdown.

Mechanical seal life is short: because the axial force cannot be completely eliminated, the water pump has 3-7mm axial movement during operation, and the rotor moves left and right during operation. The mechanical seal compression is generally within 5mm, when the axial moves to one side , The other end of the moving ring and the static ring are in poor contact and the seal fails, causing serious leakage and damage to the mechanical seal, requiring frequent replacement of the mechanical seal.

Small range of use: the balance system is unstable, the mechanical seal cannot be positioned, the failure rate is high, and the working condition is slightly poor, and it cannot operate normally; for example, conveying mine drainage with particles...

Self-balancing multi-stage pump structure diagram

Self-balancing multi-stage pump structure diagram

 

Advantages of self-balancing multistage centrifugal pump:

<1> High efficiency and energy saving: Adopt advanced hydraulic model and independently research and develop high efficiency and energy saving products; because the pump rotor does not have the wear and axial movement of the balance disc, the impeller and the guide vane are always in the best state. The structure of the ordinary multi-stage pump has a significant drop in efficiency with the wear of the balance plate and the advancement of the rotor components; and there is no leakage of the balance water, which reduces the volume loss, improves the pump's operating efficiency as a whole, reduces the shaft power, and has Very good energy saving effect;

<2> New structure: with symmetrically arranged impeller rotor components, the axial forces generated by the symmetrical impellers at various levels cancel each other, and the huge axial thrust in the pump cavity can be automatically balanced without the need for a balance disc structure, which breaks through the multi-stage The traditional structure of the pump;

<3> New technology: Due to the higher lift of the bidding product and the longer main shaft, the main shaft is more flexible during operation, and the impeller inlet and the sealing ring are prone to friction, resulting in reduced efficiency and unstable operation. The self-balancing pump has a throttling and pressure reducing device in the middle of the main shaft (this item has obtained a national patent certificate), which can not only play a throttling and pressure relief function, but also play an auxiliary support role, thereby preventing the impeller and the seal ring from wearing too quickly. In addition, the axial force in the opposite direction keeps the rotor parts under tension, which improves the rigidity of the main shaft and makes the operation more stable. Therefore, the self-balancing pump can be made longer, with higher stages, and is more suitable for high-lift pumps;

<4> High reliability: The symmetrical arrangement of the impeller makes the axial thrust generated during operation basically automatically balanced, so that there is no need for a small gap, high pressure drop, easy scouring, easy wear, and failure of the balance disc device, so that due to The wear caused by the axial force load and the adverse effect on the system interference are minimized. The residual axial force is borne by the thrust bearing, so that the pump shaft is always in tension, the shaft stress state is uniform, and the peak stress is greatly reduced compared with the prototype structure, thereby improving the rigidity and critical speed of the pump rotor, and making the pump rotor run The stability and reliability of the system are significantly improved;

<5> Good cavitation performance and long service life: The first stage impeller of MDS (P) pump adopts double suction structure. Compared with the same specification pump with the first stage impeller of single suction structure, it must have lower cavitation margin and absorb water. Better performance; At the same time, optimized hydraulic and structural design, precise casting, and reliable wear-resistant materials make the pump have good cavitation resistance, stable operation, low noise and long service life;

<6> Strong mechanical seal reliability: There is no axial movement of the rotor components when the pump is started and stopped, and there is no axial pulsation when working, which overcomes the problem of poor mechanical seal reliability that has been plagued by multi-stage pumps;

<7> Wide range of applications: the small gap balance plate is eliminated, which is more suitable for occasions with harsher media properties than the prototype structure;

<8> Low maintenance cost: The use of precision casting reduces vulnerable parts, reduces the number of assembly and disassembly of replacement parts, extends the life of the product, and minimizes a series of problems caused by excessive assembly and disassembly. Vibration and noise are greatly reduced, and maintenance costs are greatly reduced;

<9> Product parts have strong versatility and interchangeability.

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