Depamu Twin Screw Pump for Fuel Oil and Other Oils
1. Introduction
The reliable transfer of fuel oil and other petroleum-based liquids is a critical operation across industries ranging from marine shipping and power generation to petrochemical processing and heavy manufacturing. Among the various pump technologies available, the twin screw pump has emerged as a preferred solution for handling these challenging media due to its positive displacement principle, superior suction capability, and exceptional tolerance for varying viscosity and gas content. Depamu (Hangzhou) Pumps Technology Co., Ltd., a China-based manufacturer established in 2003, has developed a range of twin screw pumps that leverage advanced German engineering and proprietary technologies to meet the demanding requirements of fuel oil and oil transfer applications.
2. Company Background and Technology Foundation
Depamu is a high-tech enterprise located in the Hangzhou Qiantang Economic and Technological Development Zone, occupying a covered area of 35,000 square meters with a registered capital of 54 million yuan. The company integrates research and development, production, and sales, employing over 200 personnel and holding more than 100 patents. Its twin screw pump products are built on advanced German technologies and professional technical certifications, representing international advanced standards. The company's product portfolio encompasses Metering Pumps, high-pressure Reciprocating Pumps, Diaphragm Pumps, screw pumps (single, twin, and triple configurations), Rotor Pumps, and complete chemical dosing systems, serving industries including petrochemical, environmental protection, mining, metallurgy, energy, and marine engineering.
3. Working Principle of the Twin Screw Pump
The twin screw pump is a positive displacement pump in which two intermeshing screws rotate within a closely fitted pump casing. The helical grooves on the screws and the inner wall of the pump chamber form a series of interconnected sealed cavities. As the screws rotate continuously, these cavities move steadily along the axial direction without agitation, smoothly drawing fluid from the suction port and delivering it to the discharge port. This volumetric pumping principle ensures stable flow, low pulsation, and reliable performance. Unlike centrifugal pumps, which rely on kinetic energy to move fluids, the twin screw pump displaces a fixed volume of liquid with each rotation, making its performance largely independent of viscosity variations within the design envelope.
4. Key Design Features and Performance Advantages
Depamu twin screw pumps incorporate several design features that make them particularly well-suited for fuel oil and other oil-based media. The synchronized gear drive ensures that the rotating components do not come into direct contact, making short-term dry running safe without risk of damage. Externally mounted bearings with independent lubrication allow the pump to handle various non-lubricating media, expanding the range of fluids that can be reliably transferred. The pump's special design ensures excellent suction performance, with a net positive suction head (NPSH) requirement of only 1.5 meters, enabling effective operation even under challenging suction conditions.
A heating jacket can be added to the bottom of the pump casing to facilitate the transport of high-viscosity media, a feature of particular relevance for heavy fuel oils that may require preheating to achieve pumpable flow characteristics. The pump structure ensures that the pumped liquid always remains inside the working components as a sealing medium, providing excellent self-priming capability and enabling oil-gas multiphase transportation with a gas content of up to 98%. This gas-handling capability is a significant advantage over centrifugal pumps, which are susceptible to gas locking when entrained gas is present in the fuel stream.
5. Application to Fuel Oil Transfer
Fuel oil—encompassing marine gas oil (MGO), light gas oil (LGO), heavy fuel oil (HFO), and various intermediate grades—presents a range of pumping challenges. Heavy fuel oils are characterized by high viscosity, which increases resistance to flow and demands a pump capable of maintaining consistent capacity across a wide viscosity range. Light fuel oils, while easier to pump, may contain entrained gases or operate under conditions where cavitation is a concern. The twin screw pump addresses both scenarios effectively because, unlike centrifugal pumps, the deliverable flow rate of a positive displacement screw pump actually increases as the fluid's viscosity increases.
Twin screw pumps find extensive application in tank farms and terminals for loading and unloading vessels, rail and road tankers, and tank stripping operations, even at high viscosities and varying discharge pressures. In the marine sector, they serve as fuel oil transfer pumps, cargo oil pumps, booster pumps, stripping pumps, and engine lubricating pumps for various fuel oils, lubricating oils, waste oils, and bilge sludge. Their low noise and nearly pulsation-free operation, with minimal fluid agitation or emulsified shear, make them ideal for the unique demands of ship unloading and product transfer to distant tank farms.
6. Application to Other Oils and Lubricating Fluids
Beyond fuel oil transfer, Depamu twin screw pumps are equally well-suited for handling lubricating oils, hydraulic oils, thermal oils, and other petroleum-based fluids. The pump's ability to convey media without shearing or mixing effects preserves molecular chain structures and the specific fluid properties formed during processing, which is critical for lubricating oils where shear degradation can compromise performance characteristics. Triple screw pump configurations, which achieve smooth and quiet operation through the interaction of one driving screw and two driven screws, are particularly suitable for lubricating fluids.
In the petroleum industry, Depamu twin screw pumps are used for transporting crude oil, heavy oil, various catalysts, polymers, oil sludge, and oil-contaminated water. The pumps can handle media with viscosities of up to 100,000 cP and solid contents of up to 60%, demonstrating remarkable versatility in demanding oilfield and refinery applications.
7. Comparison with Alternative Pump Technologies
When evaluating pumping solutions for fuel oil and other oils, the twin screw pump offers distinct advantages over centrifugal pumps and other positive displacement alternatives. Centrifugal pumps, while simple and widely used, exhibit a fundamental limitation: their deliverable flow rate decreases as fluid viscosity increases, and they are prone to gas locking when entrained gas is present. Twin screw pumps, by contrast, provide a virtually constant capacity over a wide viscosity and pressure range and are unaffected in performance by gas content up to 40% (and up to 98% in the case of Depamu's optimized designs).
The lower NPSH requirement of twin screw pumps compared to centrifugal pumps means they operate without cavitation, resulting in significantly longer operating life. Compared to other positive displacement pumps such as gear pumps or progressive cavity pumps, twin screw pumps offer higher flow rates, superior gas handling, and the ability to run dry for short periods without damage, thanks to the non-contacting screw design and synchronized timing gears.
8. Technical Specifications and Customization
Depamu twin screw pumps are available in a range of configurations to suit different application requirements. Various structural designs are offered, including horizontal and vertical orientations, with customizable material combinations selected according to fluid characteristics and operating conditions. The pumps can be manufactured to comply with API 676 standards for positive displacement pumps, ensuring compatibility with international petroleum industry requirements. The modular design facilitates maintenance and allows for adaptation to specific viscosity, temperature, and pressure parameters.
9. Conclusion
Depamu twin screw pumps represent a mature, technically advanced solution for the transfer of fuel oil and other oil-based media. Their positive displacement operating principle, combined with design features such as synchronized timing gears, externally lubricated bearings, high self-priming capability, and optional heating jackets, makes them exceptionally well-suited for the demanding conditions encountered in marine fuel transfer, tank farm operations, and industrial oil handling. With a foundation in German engineering technology, a substantial patent portfolio, and a broad product range, Depamu has established itself as a capable manufacturer of twin screw pumps for the global oil and fluid handling industry. For applications requiring reliable, efficient, and versatile pumping of fuel oils and other viscous or gas-laden liquids, the twin screw pump remains a compelling choice.