An Introduction to Direct Pump

Posted on Apr 27, 2021

Direct Pump

A direct pump is a hydraulic pump that is powered by electric motors and arranged in a direct drive configuration. Mechanists and pump designers set up the powered hydraulic pumps mostly with direct or indirect drive in general, connecting the hydraulic system and the power source.

What Is a Direct Pump?

A direct pump is a hydraulic pump that is powered by electric motors and arranged in a direct drive configuration. Mechanists and pump designers set up the powered hydraulic pumps mostly with direct or indirect drive in general, connecting the hydraulic system and the power source. The direct pump, which is also widely called direct drive pump, has the hollow shaft design sliding onto the drive shaft of the engine. The connection to the pipes, tubes, hoses, the flange of the pump, is installed to the end of the motor shaft or the face of the engine.

The powered hydraulic pump converts the power source into hydraulic energy-like pressures. With the engine or electric motor, the direct pump can generate flows,  which can sufficiently resist pressure induced by the loads at the outlet of the pump. Every time the powered hydraulic pumps are activated, it generates the vacuum suction at the inlet, forcing liquids into the line toward the direct pump, subsequently transporting the liquid flows to the outlet and forcing them toward the hydraulic unit.

In the system that employs a direct pump and gasoline engine, the pump that is directly attached to the shaft has the same RPM as the engine’s one, which is about 3450 rpm. As for the system incorporating a direct pump and electric motor, the direct drive pump under the control of the motors typically rotates at the rpm of 3450 or 1723. 

The arrangement of direct drive and direct pump eliminates the side loads on the pump bearings. However, direct pumps are only applicable for relatively fewer applications, since the pump and the electric motor should be firmly and precisely installed. This helps ensure the alignment between the motor shaft and the direct drive pump. Also, the direct pump requires a pilot surface and bore on the pad in some cases, and the mechanists should still be concerned about the alignment during the mounting of the direct-drive system.


Pros and Cons of Direct Pump

One of the advantages of the direct pumps is the simple drive system that involves fewer moving components, making the direct pump and direct drive system less costly to acquire. Also, the compact and simple configuration of the direct pump and hollow shaft makes the direct pumps better suited for pressure washers that have a more compact design. 

When it comes to the disadvantages of the direct pump, the direct-drive design typically has a reduced lifespan, since the direct pump that rotates as much as the electric motor may obtain more wear, including the pump bearing part. Also, the vibration of the engine or electric motor can also significantly affect the direct pump. The features are the reason that the direct pumps cannot be used for drawing liquids from storage tanks or standing liquid sources, as the pressure washer rotates extremely fast. However, the direct pump is available when the liquids are forced into the pump structure, for instance, the water is hooked up to a hose.

:: Read more: Direct Water Pumps Make Benefits for Water Transmission


Different Options of Direct Pump Installation

The direct pump mounting types for electric motors include the hollow shaft style and bell housing style, which are both simple installations that directly mounted the pump to the engine or motor.


● Hollow Shaft Direct Pump: 

The direct pumps with hollow shaft can match the 56C or 184TC face motors, which can be directly bolted to connect the units. The design of hollow shafts changes the general features of pump motors in construction, which is a solid shaft. The direct-drive pump’s head-shaft extends through the shaft of the electric motor, connecting at the crest of the motor. 

There is an adjusting nut in this arrangement that is positioned on the peak of the head-shaft, simplifying the control of the strength of the pump impellers. The pump bushing which is mounted firmly is used to center and maintain the stability of the pump shaft. During the actual operations, the pump shaft, motor shaft as well as pump bushing spins simultaneously, causing ideal stability that is comparable to that of a solid shaft arrangement.


● Bell Housing Direct Coupled Pump:

In some cases, the mechanists utilize a set of matched pumping parts installed on the motor shaft, which is overlength in order to ensure the alignment of the motor shaft and the pump shaft. The bell housing is the connecting part for electric motors and the powered hydraulic pump, which is typically made in aluminum alloys. In the arrangement, the bell housing that uses a flexible coupler, or coupling to mount the pump to the motor, the direct pump is known as a direct-coupled drive pump. 

In general, the bell housing direct coupled drive pump is utilized up to 15 HP. The direct-coupled drive pump obtains most of the advantages of the direct pump but removes the requirements for accurate shaft alignment. In most of this style of direct pump installation, side loads on the pump bearings are lower. The users should be aware of the angularity of intersecting shafts and offset or non-intersecting shafts, which the flexible coupler should accommodate.


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