One of the fundamental elements characterizing global energy supply is the oil and gas industry, which runs effectively and efficiently due to reliable and robust equipment. The most critical component that ensures the smoothness of these operations in the industry is the centrifugal pump. These are the pumps that are necessary for transporting liquids at the various stages of exploration, production, refining, and distribution. This blog will discuss centrifugal pumps in the oil and gas industry, their types, advantages, and applications.
A centrifugal pump is a mechanical device devised to dispense a fluid by the conversion of rotating energy that is being transmitted from one or more driven rotors, that are called impellers. The accelerating fluid enters the impeller, which spins rapidly along its axis, and is ejected to the centrifugal force from the periphery of the impeller through the tips of the vanes. On its way to the pump outlet, the impeller exerts a force that increases the flow rate and the pressure of the fluid. Its primary goal is to create the circulation of the fluid while it is pressing down from the pump inlet to the impeller and then help in slowing and controlling the fluid at the exit.
Centrifugal pumps are the chief success factors in the oil and gas industry. In the upstream, midstream and downstream sectors of the company they play the major roles. This is a matter of their importance:
In the centrifugal pump, the main element is called the impeller. It is made of a number of blades that are bent. There are no changes in the case of an enclosed impeller that consists of the fluid spaces enclosed between two discs. On the other hand, an open or semi-open impeller that is only attached to a single-disc would be selected for solids in entrained fluids as it is also an alternative straightforward solution.
The fluid enters the impeller at its axis, which is called “the eye“, and then it is moved to the outlet by the vanes. The impeller is the part that is located on the opposite sides of the eye and it is the one that together with the drive shaft is attached to a motor that moves it by spinning it at high speed (usually from 500 to 5000 rpm). The impeller, being the rotational side opposite of the eye after the eye is the fluid entry, is joined to a motor and is hence driven at a very high speed (500-5000 rpm). The actual liquid starts swirling in the pump casing as a result of the rotational force produced by the impeller. The fluid is ejected out through the impeller vanes into the pump casing by the centrifugal forces created by the rotational movement of the impeller.
There are two designs of pump casing: volute and diffuser. Both of them have a common part that is to transmit the hydraulic flow to a controlled discharge at a certain pressure. The way that a volute casing is formed makes it an impeller-offset device assuming that the volute casing is the right part and the increasing part going out of the pump is the left.
As the impeller turns around, the liquid spreads out of the impeller vanes through the passage and after that, it poses pressure on the fluid hence making it flow out of it. The increased fluid pressure at the outlet is caused by the fluid acceleration before it gets closer to the outer side of the impeller. The diffuser suits the same concept and the fluid propelling force manifests itself in the same form as a radial flow airstream, for instance. In this case, the fluid pressure increases, as fluid leaves between the fixed stator vanes that encircle the impeller.
Diffuser designs can be adapted to fit a specific application and might be more effective in that niche. Volute casings are the best in terms of applications with high solids and/or high viscosity fluids when the concept of shedding the diffuser vanes is more of a benefit than the added resistance to flow. The non-uniformity of the volute design might cause more wear on the impeller and the drive shaft.
To run the centrifugal pump in the best way, a condition of constant high-speed rotation of its impeller must be observed. When dealing with feeds of high viscosity, the centrifugal pumps start to be inefficient due to increased resistance and higher pressure to keep a constant flow rate. In general, centrifugal pumps are therefore most useful in low pressure, high capacity, slipping applications of liquids with viscosities between 0.1 and 200 cP.
For example, slurry such as mud and high viscosity fuel can result in excessive wear and overheat thus leading to the damage and premature failures. Positive displacement pumps, in contrast, are usually in operation at considerably lower speeds and are thus less sensitive to these issues.
Any pumped medium that is sensitive to shearing (the separation of the emulsions, slurries or biological liquids) can also get damaged during the high speed operation of a different pump’s impeller. Hence, a positive displacement pump with a lower speed is the most suitable device for that.
Another negative aspect is that, unlike a positive displacement pump, a centrifugal pump cannot provide suction when dry: it should first be primed with the pumped fluid. Centrifugal pumps therefore have a limitation of not being suitable for applications where the fed is unstable. Moreover, in the case when deposit pressure changes, a centrifugal pump results in a variable flow; a positive displacement pump is pressure-dependent and will not change the output. In this way, in the situations where precise dosing is needed, a positive displacement pump is preferable.
The use of centrifugal pumps is highly essential during the exploration and production phases, especially:
In the transportation and storage of fluids, centrifugal pumps guarantee the steadfast reliability of the operation:
In refineries and petrochemical plants, centrifugal pumps backup a myriad of the most critical process:
Pumps in the oil and gas sector are the ones that cater to various operational demands because of their efficiencies such as:
Picking up the proper centrifugal pump is the main key to the correct performance of your application. Here are some of the most important benchmarks to consider being after:
The centrifugal pump functions through the conversion of rotational energy from one or more driven rotors, known as impellers. The impeller’s action raises the velocity and pressure of the fluid, and then it is channeled to the pump’s outlet. The centrifugal pump, with inadequate design but the most proper way to function it, thus can be easily maintained. Centrifugal pumps are the right kind of solution for many low-pressure hydraulic applications, which are low viscosity fluids like water, solvents, chemicals, and light oils. As a result, the main applications include water supply and circulation, irrigation, and the transfer of chemicals in petrochemical plants. Positive displacement pumps favor applications that use high viscous fluids like thick oils and slurries under high pressures, especially those handling emulsions, foodstuffs, and biological fluids, and when accurate dosing is necessary.
Also Read: Cutting-Edge Innovations in the Oil and Gas Industry
