Tag Archives: Vertiflo Pump Company

Cavitation on a centrifugal pump impeller

What is Cavitation?

Cavitation on a centrifugal pump impeller
Excerpt from the August 2021 Pumps & Systems Article by Peter Wolff

Understand how cavitation can damage your system.

Cavitation is a condition that can affect any fluid flow system. Despite it being an ever-present threat, it is not well understood. In the simplest possible terms, cavitation involves the formation of water vapor bubbles that damage metal components when they collapse back to the liquid phase. Here are some common questions and answers that relate to cavitation.

Does a pump sound differently when it cavitates?

Yes. Cavitation has been described as sounding like gravel or coffee beans in the system.

How does cavitation damage system components?

One aspect of cavitation that is not widely understood is why these apparently harmless bubbles are so destructive when they implode. The answer is in the release of latent heat energy of condensation when the water vapor returns to its liquid phase. The collapse of the bubble and the energy released creates a small pressure jet that can strike a nearby solid surface, potentially damaging it. Because of the large number of bubbles formed in a cavitating system, these bubbles of water vapor can cause extensive damage to system components over time. Because cavitation takes place on the entry to a pump, the first system component that the bubbles encounter is the pump impeller.

Where else can cavitation happen?

Virtually anywhere that water is moving fast. The most well-known locations, aside from pumps, are ships’ propellers, control valve seats and small-bore orifice plates in water pipework.

What causes cavitation in pumps?

Cavitation in pumps is caused by excessively low pressure at the pump inlet. A blockage or restriction such as a clogged filter or part-closed valve mounted on the inlet to the pump can cause it. It can also happen when the pump is having to source its water supply from a sump installed below the pump—called a “suction lift.” Finally, hot water, close to boiling point, is a likely contributor.

Why does hot water allow pumps to cavitate more easily?

When water temperatures are low, the vapor pressure of water is also low. For example, at 32 F, the vapor pressure is a fraction of 1 pound per square inch (psi). As water temperatures rise, the vapor pressure climbs. At 212 F, the vapor pressure is the same as standard atmospheric pressure. At this temperature, when the vapor pressure is the same as the atmospheric pressure, the water will begin to vaporize—turn to gas, in layman’s terms. The commonly known term for this is boiling.

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A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Pump Impeller Tip Speed

Wear in Centrifugal Pumps

Excerpt from the Dec. 2019 Pumps & Systems Article by Gary Dyson

Tips to recognize and reduce erosion and abrasive wear

Centrifugal pumps are sometimes used in environments where the pumped product contains suspended solids. While some pumps are specifically designed for solid handling or slurry applications, normal centrifugal pumps do not contain features to prevent performance degradation from the impact of solids.

There are a few key signs that a conventional centrifugal pump is suffering from erosive and abrasive wear. Here are assessment and mitigation strategies to be considered and applied when this occurs.

Particles are a problem in a centrifugal pump due to the way the machine adds velocity to the liquid as it passes up the impeller channels. In general, the higher the speed at the tip of the impeller, the more energy that is imparted to any particle that is suspended within the liquid. This energy can then cause damage to anything it impacts.

Pump Impeller Tip Speed

It is important to draw the distinction between tip speed and rotational speed. A small diameter impeller running at high speed could have a lower tip speed than a large diameter impeller running slowly. Tip speed is the velocity of the impeller at its outside diameter.

In general terms, the material loss by erosion is determined by the velocity of the particle cubed (Equation 1).

Equation 1:
Erosion = XC3

C is the velocity of the particle
X is a coefficient based on the liquid
being pumped

The velocity of the particle is directly associated to the tip speed of the impeller (Image 1). Lowering the tip speed of a machine has a significant impact on particle velocity and, thus, the erosive energy.

Volute Tip Wear

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Pump Curve

Determine Power When Looking at Typical OEM’s Pump Curve

Excerpt from the Feb. 2021 Pumps & Systems Article by the Hydraulic Institute

There are two ways to estimate the power for a specific operating point.

How do I determine the power required when looking at a typical manufacturer’s curve?

A typical pump curve (Image 1) includes the pump head for various impeller trims as a function flow rate. It also includes lines of constant efficiency, power and NPSH3. There are two ways to estimate the power for a specific operating point.

Pump Curve

For the flow and head, you can see where it lines up between the lines of constant power to get an estimate. In Image 1, the design flow or 1,000 gpm and 100 feet of head will require approximately 30 horsepower (hp). From this curve, we can also see that if a higher flow rate would be needed for the appropriate pump trim, it would exceed the 30-hp line, and the next size motor would be required for full curve coverage.

For any flow and head, you can find the closest efficiency and manually calculate the power required.

For the same design point in Image 1, we can see that the efficiency will be between 82% and 85% but closer to 85%, so let’s pick 84%. For water at ambient temperature (specific gravity = 1.0), the power can be calculated using Equation 1.

Equation 1

Pump input power (hp) = Flow (gpm) x Head (ft) x Specific gravity / 3960 x Pump efficiency= (1000 x 100 x 1.0)/(3960 x 0.84) = 30 hp

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

NPSHA vs rate of flow

Considerations for Wastewater Pumps

Excerpt from the Jan. 2021 Pumps & Systems Article by the Hydraulic Institute

Hydraulic Institute on examining altitude, temperature and more when selecting a wastewater pump.

Aside from handling solid waste and sludge, what else must be considered for wastewater pumps?

Typical pumping considerations for a wastewater pump include the ability to pump solids, grit, corrosive materials, sludge, scum and smaller particles that have agglomerated into larger particles. Aside from these requirements, additional considerations should be made when selecting a pump for wastewater applications. These include the altitude, temperature, flow rate and rotative-speed limitations.

When considering altitude, it is important to know that the site evaluation for the pump installation can affect pump operation. In general, the higher the elevation of the installation, the less suction lift there is available for the pump. For pumping systems with atmospheric suction pressure, the net positive suction head available (NPSHa) calculation should be checked to include the actual atmospheric pressure at the job site.

NPSHA vs rate of flow for wastewater pumps

Altitude will also affect the selection of the pump driver and, when applicable, the variable frequency drive (VFD) because higher altitudes will result in the air providing less cooling. The reduced cooling may require the driver and VFD to be derated.

The temperature of the liquid pumped affects the ability of the pump to operate. Specifically, high-temperature liquids will have higher vapor pressure, reducing the NPSHa. If not properly accounted for, the pump may cavitate, which can cause reduced performance, physical damage to the pump components and can increase vibration.

Current wastewater pump design technology allows reliable operation of pumps with values of suction specific speed (Nss) through approximately 250 for metric units (13,000 for U.S. customary units, Nss), depending on eye peripheral velocity, materials of construction, range of operation, pumped liquid properties, and other factors.

Higher Nss values result in pumps designed with lower NPSH requirements at the same or higher operating speeds. The maximum speed for a pump (n) due to NPSHa can be calculated from the Nss formula by expressing the rotative speed as a function of NPSHa, pump rate of flow (Q), and Nss (Equation 1).

Equation 1

n = (Nss × NPSHa0.75)/Q0.50

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Visualization of Gas-Liquid Flow Pattern in a Centrifugal Pump

Excerpt from the Feb. 2021 Vol. 13 of Measurement: Sensors research paper by LinZhao, Zhuang Chang, Zhenduo Zhang, Rui Huang, and Denghui He

1. Introduction

The centrifugal pump is extensively used in the fields of petroleum, chemical industry, nuclear power, agriculture, etc. The bubble flow is an important flow pattern that exists in the working process of a centrifugal pump. When bubbles are evenly distributed in the impeller channel, the pump performance is less affected by them. As the inlet gas volume fraction (IGVF) increases, bubbles may accumulate in the impeller, and thus, affect the pump performance. When bubbles coalesce further, it may form an air mass around the impeller inlet. With the increased gas concentration, the pump is prone to surge, resulting in a sudden drop in head, which is also accompanied by strong vibration and noise. In serious cases, the impeller channel will be blocked, resulting in “gas lock” effect, which makes the pump idle. This not only greatly reduces its service life, but also affects the normal production. Therefore, it is significantly important to study the flow pattern in the pump under bubble inflow condition for the safe and stable operation of pump.

Centrifugal Pumps

Murakami and Minemura classified four typical flow patterns in the pump impeller, i.e., the Bubble Flow (BF), the Agglomerated Bubble Flow (ABF), the Gas Pocket Flow (GPF) and the Segregated Flow (SF). For the pump operating under the bubbles inflow, the bubble behavior will affect the gas-liquid flow pattern in the pump, and thus, affect the pump performance. However, limited literature on the bubble behaviors in the pump are publicly available. Minemura and Murakami investigated the effect of the pressure gradient force, the drag force, the buoyancy force and the inertia force on bubbles motion in a centrifugal impeller. They reported that the governing factors for the bubble motion are the pressure gradient force and the drag force, and the effect of the inertia force increases as the diameter of bubble increases. Sterrett developed an analytical model for the motion of a single bubble through a pump impeller. The results showed that the Coriolis and buoyancy forces are important in describing the kinematics of gas phase.

The bubble motion is also influenced by the pump suction pressure. Barrios and Prado measured the bubble size inside the impeller channel of an Electric Submersible Pump (ESP) by using a high-speed instrumentation. They found that the majority of the bubbles inside the pump are not spherical. With the increase of the IGVF, the tendency of bubble coalescence as well as the bubble size increases. Similar results on the variation of bubble size were also reported by Cubas et al. Finally, the stagnant bubble at the impeller inlet causes the pump surging. Shao et al observed that for the BF and ABF patterns, the bubbles in the impeller rotate with the impeller, and the bubbles in the volute move along the volute channel. Once the IGVF reaches a critical value, some bubbles will flow back to the impeller near the volute tongue. When the flow pattern transits from the GPF pattern to the SF pattern, some bubbles in the discharge pipe return to the impeller near the volute tongue. When the height of the gas in the inlet pipe reaches the critical value, sometimes the bubble will flow into the volute, sometimes it will flow back to the impeller at a small velocity.

Stel et al experimentally and numerically investigated the bubbles motion in a centrifugal pump impeller. The effects of the bubble diameter and the liquid flow rate on the bubble trajectories were evaluated. The results indicated that the bubble movement is hindered by the bubble diameter and impeller rotational speed but facilitated by the liquid flow rate increasing. They also demonstrated that the behavior of the bubble inside the impeller is mostly dominated by a balance between the pressure gradient and the drag forces. This balance determines whether the bubble leaves or stays in the impeller. The bubble behaviors and their effects of the gas-liquid distribution in the impeller are still need further exploration.

2. Experimental setup and method

2.1. Experimental setup

Fig. 1 shows the gas-liquid two-phase flow loop employed in this study. The tap water and compressed air were used as the fluids. The experiment method and the parameters of the measurement devices employed in the present experiment are available in Ref. [18]. The measurement locations of the inlet pressure (Pin) and the pressure increment (ΔP) of the pump was shown in Fig. 1.

Centrifugal Pump Gas Flow

2.2. Centrifugal pump

The primary parameters of the centrifugal pump are shown in Table 1. As shown in Fig. 2, the pump inlet and the motor were designed in the same side to record the gas-liquid distributions in the whole impeller. The water flows into the pump through an annular inlet. The flow in the pump can be filmed from the hub of the impeller. The inlet part of the pump, the impeller and volute were made of polymethyl methacrylate (PMMA) (Fig. 3). The volute was designed with rectangular external shape and circular internal section to reduce the reflection and refraction of the light during the experiment, and thus, improving the shooting quality of high-speed photography. The pictures of the impeller and part of the volute are displayed in Fig. 3.

Centrifugal Pump Table 1

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Paradigm Shift Towards Solar Powered Centrifugal Pumps

Excerpt from the Sept. 2019 article from Modern Pumping Today by Dave Namrata

Rapidly changing agricultural technology combined with constant improvement in farm machinery is leading to wide adoption of energy-efficient centrifugal pumps, creating pressure and flow in the irrigation system. Solar-powered water pumping system in agriculture is gaining popularity as an alternative to grid electricity. The modern agricultural system has led to the growing demand for irrigation solutions that reduces energy cost, improves productivity and safeguards water resource. Moreover, a reduction in the price of solar panels and components in solar power systems is driving the adoption of solar-powered centrifugal pumps and emerging as an economically viable option for irrigation.

The growing concern towards wastewater treatment in the past few years has resulted in wide application of centrifugal pumps. Rising competitiveness in the market is resulting in the development of centrifugal pump technology leading to better performance and reduction in the overall cost. From a design perspective, manufacturers of centrifugal pumps are focusing on improving the quality of shaft steel in the pumps to withstand vibration, fatigue, and stress. According to some industry experts, water shortage is likely to impact more than half of the world population by 2025. This is accelerating the wastewater treatment process across the countries.

Increasing energy costs and growing environmental awareness are motivating pump manufacturers to focus on developing energy-efficient centrifugal pumps for the end-use industries. Moreover, centrifugal pumps operating at a high speed pumping a large amount of liquid consume more power. This is leading to the integration of economically feasible and reliable solar power in the centrifugal pumping system.

Long product life and low maintenance cost of solar-powered centrifugal pumps are emerging as the perfect alternative to other pumping systems. Industries consider various factors while selecting a pumping system, such as pump lifecycle cost, including initial cost, maintenance cost and energy cost. On average, centrifugal pumps can consume around 60 percent of motor energy in the facility resulting in higher energy and maintenance costs.

Centrifugal Pumps
Centrifugal pumps generated by solar power

 

Increasing Focus on Energy Efficiency

In recent years, with an increasing cost of energy worldwide, energy efficiency is gaining attention from governments and pump manufacturers across countries. Despite various challenges, pump manufacturers are adding sustainable design features, enhancing productivity, quality, and services.

Solar-powered centrifugal pumps have gained popularity and are available on a large scale in the developed countries. However, the high initial cost of solar-powered centrifugal pumps as compared to the cost of fuel-powered pumps is the main obstacle for solar pumps in developing countries. This is driving the pump manufacturers in the developing regions to design next generation, cost-effective solar powered centrifugal pumps, eliminating the need for grid connection or fossil fuel.

Use of solar photovoltaic technology for centrifugal pumping system has gained immense popularity. Continuous reduction in solar cells cost is likely to drive the application for centrifugal pumps powered by the solar photovoltaic system in agriculture and other industries.

solar panels for centrifugal pumps
Solar panels for centrifugal pumps

With an aim to save the energy cost, replacement and refurbishing of the pumping system in water and wastewater treatment industry is on the rise. There has been a rise in the adoption of centrifugal pumps powered by solar energy in this industry.

Driven by rapid industrialization and urbanization, municipal water and wastewater industry in emerging countries is creating growth opportunities for centrifugal pumps manufacturers. However, manufacturers are facing a flood of new competition due to the increasing demand for energy-efficient pumps and stringent regulations. According to the American Hydraulics Institute, around 30 percent of the total electrical energy consumed by pumping systems can be saved by developing a highly efficient system and using appropriate pumps.

First-generation PV pumping systems using centrifugal pumps have shown significant advancements in recent years. The current solar-powered pumping technology uses an electronic system by further increasing the output power, performance and efficiency. PV modules account for nearly 60 to 80 percent of the total cost of PV system. A significant decline in the cost of PV modules across various regions has also reduced the overall cost of the pumping system. Moreover, an increase in the cost of crude oil, diesel, and gasoline has made solar powered pumps financially attractive.

There exists immense growth opportunity for centrifugal pumps in wastewater, pharmaceuticals, food and beverage, and chemical industries, as the sectors are set to grow at a stable pace in the near future. However, centrifugal pump demand will continue to be hit by the nuclear power generation, mining, and oil and gas sectors, which are likely to experience slow growth.

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Minimum Continuous Stable Flow

Centrifugal Pump Flow Operating Regions and Impact on Reliability

Ideally, a centrifugal pump should be operated at or near its best efficiency point (BEP) flow rate in order to minimize the life cycle costs. However, all centrifugal pumps have sweet spots beyond the BEP that will yield acceptable efficiency and reliability.

Excerpt from the Sept. 2016 article from WaterWorld

There are limitations, though, on the minimum and maximum flow rates, beyond which the pumps should not be operated continuously (or for an extended period of time), in order to avoid premature failures.

A first step in avoiding these negative, low-efficiency and low-reliability conditions is to determine the pump BEP, preferred operating region (POR), and allowable operating region (AOR) flow rates. It is especially important to determine these flow regions because not all pump applications are static in nature or closely match the expected system demand. Because of this, pumps are often required to operate over a broad range of flow rates, which can adversely affect the pump efficiency and reliability.

Centrifuge Flow Reliability Factor

A pump will always operate at the flow rate where the pump head-capacity curve intersects the system head-capacity curve. This means that it is also critical to accurately determine the true system H-Q curve, in order to establish the true operating flow rates.

Once these flow regions and the true system conditions are known, actions can be taken to maximize pump operation in the POR and avoid or minimize operation outside the AOR, thus optimizing pump life cycle costs.

BEP Flow Region

Pump performance and service life are optimized around a rate of flow designated as the BEP. At the BEP, the hydraulic efficiency is maximum, and the liquid enters the impeller vanes, casing tongue (discharge nozzle), and diffuser vanes in a shockless manner. At the BEP, flow through the impeller and diffuser vanes (if so equipped) is uniform, free of separation, and well-controlled.

Minimum Continuous Stable Flow

Lower and higher flow rates cause mismatch between the flow and the impeller and casing vanes. This mismatch causes turbulence within the impeller and casing flow passages, which both block the flow passages and increases the local velocities. This increase in velocity increases vaporization (cavitation) within the liquid. The greater this resulting turbulence and cavitation, the lower the pump efficiency and reliability, and the more severe are the levels of vibration, noise and erosion.

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

What is a Centrifugal Pump?

centrifugal pump is a machine that uses rotation to impart velocity to a liquid and then converts that velocity into flow.

Excerpt from introtopumps.com

Let’s break that definition down into its components so that we can consider each one in turn:

  1. A centrifugal pump is a machine.
  2. A centrifugal pump uses rotation to impart velocity to a liquid.
  3. A centrifugal pump converts velocity into flow.

Every centrifugal pump includes an assembly of mechanical components that make operation of the pump possible. This mechanical assembly includes the pump shaft mounted on bearings, the sealing mechanism that keeps the pump from leaking excessively, structural components designed to handle the stresses and loads imposed on the pump during operation, and wear surfaces that allow the pump to be repaired and returned to its original specifications.

Every centrifugal pump includes an impeller. The impeller is the hydraulic component that rotates to impart velocity to the pumped liquid.

Every centrifugal pump includes a casing. The casing is the hydraulic component that captures the velocity imparted by the impeller and directs the pumped liquid to the pump discharge point.

At the most fundamental level, a centrifugal pump consists of just these three components:

  1. An impeller that rotates and imparts velocity to a liquid.
  2. A casing that captures the velocity generated by the impeller and transforms that velocity into a stable flow.
  3. An assembly of mechanical components that makes it possible for the impeller to be rotated within the pump casing.

>>Read more.


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Net Positive Suction Head Cavitation in Centrifugal Pumps

How to Understand Net Positive Suction Head

There are two ways of expressing NPSH relative to a centrifugal pumping system.

Excerpt from the August 2020 Pumps & Systems article by Gary Dyson

To make the term net positive suction head (NPSH) more accessible to pump engineers who may not understand how to design an impeller for NPSH or the exact details of the physics, I have tried to simplify it:

  • NPSH is a measure of the absolute pressure energy present in a liquid. Pump engineers use this energy to help “feed” the fluid into the eye of the first-stage impeller. Pumps generally do not suck.
  • NPSH is the sum of the total static plus kinetic pressure minus the liquid vapor pressure at the pump suction nozzle or impeller entry, which is expressed in terms of head.
Net Positive Suction Head Cavitation in Centrifugal Pumps
Net Positive Suction Head Cavitation in Centrifugal Pumps

There are two ways of expressing NPSH relative to a centrifugal pumping system:

  1. NPSHa—The net positive suction head available is the measurement of the amount of fluid pressure energy available from the system at the pump impeller inlet.
  2. NPSHr—The net positive suction head required is the measurement of the amount of fluid pressure energy required by the pump.

The NPSH available to the pump should be more than what the pump requires. If there is not enough NPSHa, the pump will cavitate. As a result, the performance and reliability can be compromised.

Impeller Blade Cavitation from Bubbles
Impeller Blade Cavitation Damage from Collapsing Bubbles

NPSHr Curves

NPSHr curves, as provided by the pump manufacturer, are generated using the data collected during a pump performance test. Determining NPSHr requires testing the pump over a series of carefully controlled, constant flow points and varying suction conditions in a test facility. The test lab operator sets the flow and then begins to introduce a vacuum on the suction side of the pump. This reduces the suction pressure in controlled increments. While reducing the suction pressure, the discharge pressure is closely monitored.

>>Read more.

 


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.

Horizontal Centrifugal Pump Selection for Chemical Applications

Selecting the Right Pump for Chemical Applications

Review pump types and pick proper construction materials.

Excerpt from the February 2020 Pumps & Systems article by Pete Scantlebury

There are many considerations when selecting the right pump for chemical applications. When working with materials such as corrosive or flammable chemicals, extra care should be taken to ensure that the product selected is suitable.

Define the Fluid Characteristics

The safety data sheet (SDS) and chemical manufacturer or chemical distributor can provide required information such as fluid name, concentration, fluid temperature, specific gravity and viscosity at pumping temperature. If solids are present, determine at what concentration, particle size and hardness, and if the material is corrosive, flammable or combustible.

Describe the Application

The more detailed the description, the better. Make sure to verify:

  • What type of container is the chemical stored in? Is it a drum or tote, bulk storage tank, rail car or tanker truck?
  • Where will the fluid be moved? From a drum to a bucket, from a rail car to bulk storage, or simply recirculating in the same container, for example.
  • Is the liquid below the pump? In this case, a pump that is either self-priming or one that can be submerged in the liquid is needed.
  • What is the flow rate required? Flow rate is required to calculate friction loss in the piping system.
  • What is the total head or pressure required? Total head is based on the piping system and is used (along with flow rate) to help choose a pump.
  • What is the net positive suction head available (NPSHa)? It is the suction head made available to the pump and provided by the piping system. To avoid cavitation (causes erosion damage to pump components) the NPSHa must exceed the NPSH required (NPSHr).
  • How long will the pump be operating per day or week? This is important in evaluating energy costs. For example, if a pump is going to be operating many hours per day, a pump driven with an electric motor could have considerably lower operating costs compared to an air-driven pump.
  • Is it indoors or outdoors? What are the maximum and minimum ambient temperatures? This is important for the correct selection of the construction materials for the pump and motor.
  • What is the altitude? Higher altitudes reduce available lift if it is a self-priming application, reduces NPSHa and reduces cooling by an electric motors fan.

Pump Selection

There are many variables to the selection of the best pump type with the correct materials of construction.

  • Gather information on the fluid to be pumped.
  • Gather information on the hydraulic and application requirements.
  • Consult the experts. Consult with the chemical manufacturer, chemical distributor, pump manufacturers, local pump distributors, and even industrial supply catalogs that are experienced in the selection of chemical pumps.
Horizontal Centrifugal Pump Selection for Chemical Applications
Horizontal Centrifugal Pump Selection for Chemical Applications

Review Possible Pump Types

Here are some of the most common pump types for transferring chemicals.

Drum/barrel pumps: Ideal for transferring a wide variety of chemicals from pails, drums, totes [(such as intermediate bulk containers (IBCs)] and other containers used by chemical manufacturers to transport products to the user. These can be powered by electric, lithium ion battery or air motors.

Centrifugal pumpsProvide smooth flow and have a wide range of flows and head capabilities. These pumps are available in a wide range of materials and either mechanically sealed or sealless magnetically coupled. They are typically operated with electric motors.

Air-operated double diaphragm pumps: Versatile, simple to operate, and can pump solids and viscous fluids. They typically operate with compressed air.

Positive displacement pumps: Includes gear, rotary vane or piston pumps. These pumps are good with high viscosity fluids and can generate high pressures.

>>Read more.

 


A Complete Line of Pumps for Industry

Vertiflo Pump Company’s Vertical Sump Centrifugal Pumps, Horizontal End Suction Centrifugal Pumps and self-priming pumps are delivered fast, usually in half the typical lead time. Vertiflo’s vertical sump pump line offers up to 3000 GPM, 250′ Heads and 26′ depth. The horizontal end suction pump line offers up to 3000 GPM and 300’ Heads.

Vertiflo pumps are designed for nonresidential applications and currently over 20,000 are operating successfully worldwide. Vertiflo is recognized as a quality manufacturer of dependable pumps, and continues to grow and encompass new applications in the pump industry.