Pump Drives Information
Pump drives take power from an input rotational source and send it to a hydraulic pump. Gears or other equipment generate the power. Pumps are positioned on the drive housing.
A pump system's rotary power source is referred to as a drive. The term drive signifies motor control units such as an inverter or starter. It also refers to other segments of the power supply such as a motor or gearbox. Gearboxes moderate motor speed. When attached to a motor as a unit, they are considered gearmotors.
The following are the two predominant types of pumps:
- Centrifugal pumps operate at speeds above 1750 rpm. They direct liquids toward their center, where centrifugal force discharges the liquids. Fluids of low to medium viscosity are appropriate for such devices as they generate shearing that mixes the fluids. As a result, homogenous mixtures work well with these instruments.
- Positive displacement (PD) pumps operate at a slower rate than the centrifugal models. They rely on rotating sections of space for moving the product. These devices induce minimal shear and are suitable for non-homogenous mixtures to retain product texture.
Inline helical geared motor drives featuring feet or flanges for mounting serve as PD pump drives. Gear reducers are engaged to ensure the speed is in a proper range. Select models feature input flanges and hollow shafts conjoined with a flanged gearmotor. Pumps with a solid input shaft employ the footed version.
Bolting a coupled C-face motor to a gearmotor drive is expensive. However, it allows using any type of C-face unit in conformance with NEMA dimensions. This permits access to a broad selection of motors designed for particular applications.
Pump drives support a myriad of features, including:
- Engine mount
- Independent mount
- Increasing ratio
- Decreasing ratio
- Field configurable pads
- Field configurable splines
- Thru shafts
- PTO shafts
- Individual pump disconnects
- Hot shift clutches
- Cast iron housings
- Ball bearings
- Heavy duty (non shimming) ball bearings
- Case hardened shafts
- Identical gear ratios on outputs
- Output rotation direction opposite input rotation
- Multiple disc drive plates (for smoother operation)
- Non-bearing cup pump pads (for easy removal)
- Voltage spike protection
The drives serve a diverse spectrum of fields where pumps are utilized, including:
- Oil and gas drilling
- Mixed flow
When it comes to selecting these devices, the following factors merit consideration:
- Pad number (determines how many pumps are mountable to a drive)
- Sizing the drive
- Horsepower rating
- Maximum torque
- Gear ratio
Pump manufacturers rely on computer-aided programs or graphs displaying pump performance to determine horsepower, size, and speed of a drive. If a device possesses a slower than needed rpm, reduction in flow rate occurs. Devices with excessive rpm may cause a disparity between the calculated horsepower and selected horsepower, reducing operational efficiency as a result.
Once the instrument's horsepower and rpm have been identified, the speed reducer service is selected. The speed reducer is required to have a service factor equal to or greater than the level recommended by the AGMA. Speed reducers with service factors unsuited to specific tasks are subject to premature failure.
With improvements in technology, drives using variable frequency inverters are gaining popularity. They replace belt cases and traction drives in activities where multiple speed operation is essential. They offer specific benefits such as programming and reliability. Use of standardized speed reducers and motors makes the devices more compact than belt cases or traction drives.
Torque analysis is helpful in minimizing the chances of over- or undersizing a drive's horsepower. Functions engaging dissimilar products with different rates of flow require variable torque. On the other hand, activities involving the same pump necessitate individually calculated torque. In these cases, the drive is sized to accommodate the largest torque and the greatest speed.
To size two separate applications using the same pump, the following steps are required:
- Calculate the pump's load torque at all possible speeds
- Determine the size of the drive motor using the highest load torque at the maximum load speed
The use of friction drives for applications where shock loading occurs is discouraged. Doing so creates the potential to cause damage to internal traction drive components. A belt case is a suitable alternative as it allows the rubber belt to absorb shocks and reduce wear and tear.