As a supplier in the oilfield pump industry, I’ve witnessed firsthand the critical role these pumps play in the efficient extraction and transportation of oil. The appropriate starting method for an oilfield pump is not just a technical detail; it can significantly impact the pump’s performance, longevity, and overall operational safety. In this blog, I’ll explore some of the most common starting methods for oilfield pumps and delve into their respective advantages and considerations. Oilfield Pump
Direct – On – Line (DOL) Starting
Direct – On – Line starting is perhaps the most straightforward and simplest method of starting an oilfield pump. In a DOL start, the pump motor is directly connected to the full supply voltage at the instant of starting. This method is characterized by a high – initial current, which can be up to six to eight times the motor’s full – load current.
The major advantage of DOL starting is its simplicity and low cost. There are no additional starting devices required, which reduces both the initial investment and the maintenance complexity. For small – to medium – sized oilfield pumps with relatively low power ratings, DOL starting is often a practical choice. It allows the motor to quickly reach its rated speed, providing an immediate start and enabling efficient operation.
However, DOL starting also has its drawbacks. The high – inrush current can cause significant voltage drops in the electrical supply system. In an oilfield environment where multiple pumps and other equipment may be operating simultaneously, these voltage drops can disrupt the operation of other sensitive devices. Moreover, the high mechanical stress caused by the sudden application of full torque can lead to premature wear and tear of the pump’s mechanical components, such as shafts, couplings, and bearings.
Star – Delta Starting
Star – delta starting is another commonly used method for starting oilfield pumps, especially for larger motors. In this method, the motor windings are initially connected in a star (Y) configuration during the starting period. This reduces the voltage applied to each phase of the motor to approximately 58% of the line voltage. As a result, the starting current is reduced to about one – third of what it would be with a DOL start.
After the motor has reached a certain speed (usually 70% – 80% of the rated speed), the winding connection is switched from star to delta (Δ), and the motor then operates at full voltage. The star – delta starter consists of a main contactor, a star contactor, and a delta contactor, along with a timer to control the switching sequence.
The main advantage of star – delta starting is the significant reduction in starting current, which minimizes the voltage drop in the electrical supply system. This is particularly important in oilfields where stable power supply is crucial for the operation of various equipment. Additionally, the reduced inrush current also means less mechanical stress on the pump components, which can extend the equipment’s service life.
On the downside, star – delta starting requires additional electrical components, such as contactors and timers, which increase the initial cost and the complexity of the system. The switching operation from star to delta also introduces a brief interruption in torque, which may cause a small jerk in the pump’s operation.
Auto – Transformer Starting
Auto – transformer starting is a more sophisticated method that uses an auto – transformer to reduce the voltage applied to the motor during the starting process. The auto – transformer steps down the supply voltage to a lower value, typically 50%, 65%, or 80% of the full voltage, depending on the motor’s requirements.
By reducing the starting voltage, the starting current is proportionally reduced. Similar to star – delta starting, the auto – transformer starting method allows for a smooth start with less stress on the pump’s mechanical and electrical components. The starting torque can be adjusted by selecting the appropriate tapping on the auto – transformer, which provides more flexibility compared to star – delta starting.
However, auto – transformer starters are relatively expensive due to the cost of the auto – transformer itself. They also require more space for installation, which can be a constraint in some oilfield facilities. Additionally, the auto – transformer needs to be sized correctly to match the motor’s specifications, and improper sizing can lead to inefficient operation or even damage to the equipment.
Soft – Starter Starting
Soft – starter starting is a modern and increasingly popular method for starting oilfield pumps. A soft – starter uses solid – state devices, such as thyristors, to control the voltage applied to the motor during the starting process. The voltage is gradually increased from a low value to the full – line voltage over a pre – set time period, typically ranging from a few seconds to a minute.
This gradual increase in voltage results in a smooth start with a controlled starting current. The soft – starter can also limit the starting torque, reducing the mechanical stress on the pump’s components. Additionally, soft – starters can provide various protection features, such as over – current protection, over – temperature protection, and phase – imbalance protection, which enhance the safety and reliability of the pump operation.
One of the key advantages of soft – starters is their flexibility. The starting parameters, such as the ramp – up time and the starting voltage, can be easily adjusted to match the specific requirements of the pump and the operating conditions. Soft – starters also allow for easy integration with other control systems, enabling remote monitoring and control.
However, soft – starters are more expensive than traditional starting methods. They also generate some heat during operation, which requires proper ventilation and cooling to ensure reliable performance.
Variable Frequency Drive (VFD) Starting
Variable Frequency Drive starting is the most advanced starting method for oilfield pumps. A VFD not only controls the voltage applied to the motor but also varies the frequency of the electrical supply. By adjusting the frequency, the VFD can precisely control the motor’s speed, allowing the pump to operate at different speeds according to the demand.
During the starting process, the VFD ramps up the frequency and voltage gradually, providing a very smooth start with minimal inrush current. This method offers the highest level of control over the pump’s operation. It can optimize the pump’s performance, reduce energy consumption, and extend the life of the pump and its components.
In an oilfield environment, where the flow rate and pressure requirements can vary widely, a VFD – controlled pump can adjust its speed to match the changing conditions, which is more energy – efficient compared to fixed – speed pumps. Additionally, VFDs can provide advanced diagnostic and monitoring features, which allow operators to detect and troubleshoot potential problems before they cause significant damage.
However, VFDs are relatively expensive and require a high level of technical expertise for installation, operation, and maintenance. They also generate electromagnetic interference (EMI), which may require additional shielding and filtering to prevent interference with other electrical equipment.
In conclusion, choosing the right starting method for an oilfield pump is a critical decision that depends on various factors, including the pump’s power rating, the electrical supply system, the operating conditions, and the budget. As a supplier, I understand the importance of providing tailored solutions to our customers. We have a team of experienced engineers who can analyze your specific requirements and recommend the most suitable starting method and pump system for your oilfield operations.
If you’re in the market for an oilfield pump and are concerned about the starting method and overall pump performance, don’t hesitate to reach out to us. We’re committed to providing high – quality products and professional services to help you achieve efficient and reliable oilfield operations. Contact us today to explore how we can meet your needs.
Mud Pump References:
- Electric Motor Handbook, by Arnold E. Fitzgerald, Charles Kingsley Jr., and Stephen D. Umans
- Pump Handbook, by Igor J. Karassik, Joseph P. Messina, Paul Cooper, and Charles C. Heald
- Practical Electric Motor Handbook, by Irving Gottlieb
Shandong Rongli Intelligent Manufacturing Co., Ltd.
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