Category Archives: Pump Technology

Horizontal Centrifugal Pump

Characteristics of Centrifugal Pumps

What are the Characteristics of a Centrifugal Pump? Head, performance curve and affinity laws all contribute to the efficiency of centrifugal pumps.

Excerpt from Pumps & Systems, Sept. 2012, by Sharon James, Rockwell Automation

Pumps are generally grouped into two broad categories—positive displacement pumps and dynamic (centrifugal) pumps. Positive displacement pumps use a mechanical means to vary the size of (or move) the fluid chamber to cause the fluid to flow. On the other hand, centrifugal pumps impart momentum to the fluid by rotating impellers that are immersed in the fluid. The momentum produces an increase in pressure or flow at the pump outlet.

Horizontal Centrifugal Pump
Horizontal Centrifugal Pump

Positive displacement pumps have a constant torque characteristic, whereas centrifugal pumps demonstrate variable torque characteristics. This article will discuss only centrifugal pumps.

A centrifugal pump converts driver energy to kinetic energy in a liquid by accelerating the fluid to the outer rim of an impeller. The amount of energy given to the liquid corresponds to the velocity at the edge or vane tip of the impeller. The faster the impeller revolves or the bigger the impeller, then the higher the velocity of the liquid at the vane tip and the greater the energy imparted to the liquid.

Characteristics

Creating a resistance to the flow controls the kinetic energy of a liquid coming out of an impeller. The first resistance is created by the pump volute (casing), which catches the liquid and slows it down. When the liquid slows down in the pump casing, some of the kinetic energy is converted to pressure energy. It is the resistance to the pump’s flow that is read on a pressure gauge attached to the discharge line. A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.

Static Discharge Head Suction Lift and Total Static Head

Figure 2. Representation of static discharge head, static suction lift and total static head

Head—Resistance to Flow

In Newtonian (true) fluids (non-viscous liquids, such as water or gasoline), the term head is the measurement of the kinetic energy that a centrifugal pump creates. Imagine a pipe shooting a jet of water straight into the air. The height that the water reaches is the head. Head measures the height of a liquid column, which the pump could create resulting from the kinetic energy the centrifugal pump gives to the liquid. The main reason for using head instead of pressure to measure a centrifugal pump’s energy is that the pressure from a pump will change if the specific gravity (weight) of the liquid changes, but the head will not change. End users can always describe a pump’s performance on any Newtonian fluid, whether it is heavy (sulfuric acid) or light (gasoline), by using head. Head is related to the velocity that the liquid gains when going through the pump.

All the forms of energy involved in a liquid flow system can be expressed in terms of feet of liquid. The total of these heads determines the total system head or the work that a pump must perform in the system. The different types of head—friction, velocity and pressure—are defined in this section.

Friction Head (hf)

Friction head is the head required to overcome the resistance to flow in the pipe and fittings. It depends on the size, condition and type of pipe; the number and type of pipe fittings; flow rate; and nature of the liquid.

Velocity Head (hv)

Velocity head is the energy of a liquid as a result of its motion at some velocity (V). It is the equivalent head in feet through which the water would have to fall to acquire the same velocity or, in other words, the head necessary to accelerate the water. Velocity head can be calculated using the following formula:

hv = V2/2g

Where:
g = 32.2 ft./sec.2
V = liquid velocity in ft./sec.

The velocity head is usually insignificant and can be ignored in most high-head systems. However, it can be a large factor and must be considered in low-head systems.

Pressure Head
Pressure head must be considered when a pumping system either begins from or empties into a tank that is under some pressure other than atmospheric. The pressure in such a tank must first be converted to feet of liquid. A vacuum in the suction tank or a positive pressure in the discharge tank must be added to the system head, whereas a positive pressure in the suction tank or vacuum in the discharge tank would be subtracted. The following is a formula for converting inches of mercury vacuum into feet of liquid:

Vacuum, feet of liquid = (Vacuum, in. of hg x 1.13)/Specific Gravity

The different types of head are combined to make up the total system head at any particular flow rate. The descriptions in this section are of these combined or dynamic heads, as they apply to the centrifugal pump.

Read more at Pumps & Systems.


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.

Suction Throttling NPSH Test Setup

What You Need to Know About NPSH

Most pump problems are related to net positive suction head (NPSH).
By Terry Henshaw, Pumps & Systems February 2018

Definition of NPSH
The margin of pressure over vapor pressure, at the pump suction nozzle, is net positive suction head (NPSH). NPSH is the difference between suction pressure (stagnation) and vapor pressure. In equation form:

NPSH = Ps – Pvap

Where:
NPSH = NPSH available from the system, at the pump inlet, with the pump running
Ps = stagnation suction pressure, at the pump inlet, with the pump running
Pvap = vapor pressure of the pumpage at inlet temperature

Since vapor pressure is always expressed on the absolute scale, suction pressure must also be in absolute terms. In U.S. customary units, both pressures must be in pounds per square inch absolute (psia). Gauge pressure is converted to absolute pressure by adding atmospheric pressure. The above equation provides an answer in units of pressure (psi). This can be converted to units of head (feet) by the following equation:

h = 2.31p/SG

Where:
h = head in feet
p = pressure in psi
SG = specific gravity of the liquid

Importance of NPSH
NPSH is a subject of extreme importance in all pumping systems. It has been estimated that 80 percent of all pump problems are due to inadequate suction conditions, and most suction problems are related to NPSH. (Either the system does not provide as much as anticipated, or the pump requires more than anticipated.) It is therefore probable that most pump problems are NPSH problems.

Units of NPSH
For centrifugal pumps, NPSH values are expressed in units of specific energy (equivalent column height) such as feet or meters. For displacement pumps (rotary and reciprocating), NPSH values are normally expressed in pressure units such as pounds per square inch (psi), kilopascals pr bars.

NPSH values are neither gauge pressures nor absolute pressures. The “g” in psig means that the pressure is measured above atmospheric pressure. The “a” in psia means that the pressure is measured above absolute zero, a perfect vacuum. NPSH is a measurement of pressure above vapor pressure, so the units of NPSH (in the U.S.) are just psi or feet.

NPSH Available: A System Characteristic
NPSHa stands for NPSH available from the system. It can be calculated by measuring suction pressure at the pump suction nozzle, correcting to datum, adding atmospheric pressure, adding velocity head and subtracting vapor pressure. In equation form:

NPSH = Psg + Pz + Patm + Pvel – Pvap

Where:
NPSHa = NPSH available to the pump, psi
Psg = gauge pressure measured at suction nozzle, psig
Pz = elevation of gauge above pump centerline, converted to pressure unites, psi
Patm = atmospheric pressure, psia
Pvel = velocity head, converted to pressure united, psi
Pvap = vapor pressure of the pumpage, at the pump suction nozzle, psia

If desired, all units can be converted to head (feet) prior to plugging into the equation. If the system has not been built, it is necessary to calculate the NPSHa by starting with the pressure in the suction tank. Add atmospheric pressure, add (or subtract) the liquid level above (below) datum, subtract all losses from the tank to the pump and subtract vapor pressure.

NPSH Required: A Pump Characteristic
The letters NPSHr stand for the NPSH required by the pump. This characteristic must be determined by test.
For proper operation of the pump, it is necessary that NPSHa > NPSHr. The system must provide more NPSH than the pump requires.

What Happens When NPSHr Exceeds NPSHa?
One potential complication when NPSHr exceeds NPSHa is cavitation. If at any time the static pressure on a liquid drops below vapor pressure, a portion of the liquid will boil-it will flash to a gas. This formation of gas bubbles is called cavitation. (Cavities form in the liquid.) Such gas formation in a suction pipe or inside a pump may cause a reduction in pump capacity and/or head. It may also cause damage to the pump. As liquid flows into any pump, there is a reduction in pressure. In a centrifugal pump, the liquid accelerates into the eye of the impeller, causing a reduction in pressure. The impeller vanes then slice into the liquid, creating zones of lower pressure.

If a sufficient pressure margin, over vapor pressure, is not provided at the pump inlet, some of the liquid will flash at the leading edge of each vane.

With displacement pumps, the situation is similar. Because the pressure drops as the pumpage moves into the pumping chamber, suction pressure must exceed vapor pressure by some margin to prevent cavitation.

Even though the liquid is cavitating, we usually say that the pump is cavitation. Possible effects of pump cavitation include noise, head and/or capacity loss, and equipment damage. It is not the formation of the bubbles that causes damage. Damage is caused to pump parts when the bubbles collapse or “implode.” When the bubbles collapse on a hard surface, they create a high pressure.

To Quieten a Cavitating CentrifugaI Pump
If a centrifugal pump sounds as if it is pumping gravel, if the system can tolerate it and if no other solution is readily available, inject about ½ percent (by volume) air (or other gas) just upstream (into the inlet) of the pump. Experiment to see how little air is necessary to obtain quiet operation. (Do not try this with a reciprocating pump!)

NPSHr & Suction Specific Speed
Suction specific speed, like specific speed, is not a speed at all. It is an index number, or “yardstick.” It is based on the NPSHr of a centrifugal pump, normally the 3 percent head drop NPSHr and normally at its best efficiency point (BEP). The equation for suction specific speed is the same as specific speed, except that NPSHr is substituted or head, as follows:

S = N√Q/NPSHr0.75

Where (in U.S. units):
S = suction specific speed
N = RPM of pump
Q = pump capacity*†, GPM
NPSHr = NPSH required by pump†, feet

*If the impeller is double suction, Q in the above equation is one-half the BEP capacity of the pump. This is a major difference from calculating specific speed, in which w use total pump capacity, whether the impeller is single suction or double suction.
†Normally calculated at the BEP

The symbol Nss is often used in place of S for suction specific speed. The value of S for most pumps is typically between 7,000 and 15,000. The higher values are more common in higher speed, higher capacity units.

Suction Specific Speed
For a number of years, the push from users and competitors required pump manufacturers to continually strive for lower values of NPSHr. The philosophy was that “The lower the NPSHr, the better the pump.” NPSHr in centrifugal pumps is normally reduced by increasing the diameter of the impeller eye. That philosophy has now changed.

Due to problems that have been attributed to oversized impeller eyes, pump users have established maximum values for S, which establishes minimum values for NPSHr. (See Pumps & Systems, December 2011, pumpsandsystems.com/ analyzing-impeller-eye).

Every centrifugal pump would like to run at its BEP. Pump components would experience maximum life at that capacity. Seldom does a pump run at its BEP, but component life will be significantly extended if it operates within its “stable” window of capacities. Suction specific speed can indicate the size of that window. Pumps with lower values of S have larger windows.


WAYS TO INCREASE & REDUCE NPSHa
If it is necessary to increase a system’s NPSHa, one or more of the following steps may be employed:

  1. Raise the level of the liquid in the suction vessel.
  2. Cool the liquid (after it leaves the vessel).
  3. Reduce the losses in the suction line by reducing its length, increasing its diameter, reducing number of fittings, etc.
  4. Install a booster pump.
  5. With a reciprocating pump or pulsating rotary pump, install a bottle or suction stabilizer in the suction line adjacent to the pump.

Ways to Reduce NPSHr
If the pump is in the selection stage, one or more of the following options may be employed to reduce the NPSHr:

  1. Use a double-suction impeller.
  2. Use a larger pump.
  3. Use a lower speed pump.
  4. Use an inducer (a small axial-flow impeller built into the eye of the main impeller).
  5. Install the pump at a lower elevation.
  6. With a vertical turbine pump, lower the first-stage impeller (make the pump longer).

All of the above will normally increase the initial cost of the pump and/or installation. Options two and three will also likely result in higher operating cost due to lower efficiency. Option two may result in a pump operating in the hydraulically unstable range. If the pump is already installed, one or more of the following options may be employed to reduce the NPSHr:

  1. If operating near or beyond the SEP, reduce pump capacity.
  2. If operating near shut-off, increase pump capacity (with a bypass if necessary).
  3. Reduce wear ring clearances.
  4. Reduce seal flush flow.
  5. Vent the seal chamber (stuffing box) back to the suction vessel.
  6. On a horizontal multistage pump with a balancing drum, pipe balancing line back to the suction vessel. The valves in this line must be locked open.
  7. On a vertical multistage pump, pipe the bleed-off line from the throat bushing back to the suction vessel. The valves in this line should be locked open.

This article was originally printed in Pumps & Systems magazine February 2018.


Industry News from the Pumps & Systems

 

The Cost of a Misbehaving Pump

Pump Training & Education


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.

Centrifugal pump selection guide 2

Centrifugal Pump Selection Guide, “How Pump Curves Assist in Selection,” by the Hydraulic Institute

HI Pumps FAQ, as published in June 2018 PUMPS & SYSTEMS Magazine

Q: How do I use the information on a pump curve to select a pump for my system?

A: A centrifugal pump selection guide curve (sometimes called a performance curve) is a graph that shows the total head, power, efficiency and net positive suction head (NPSH) where a 3 percent head loss occurs (NPSH3) plotted against rate of flow. These curves contain extremely important data that pump users need to analyze and interpret for proper pump selection and efficient operation. There are three main types of pump curves supplied by the pump manufacturer:

  • the selection chart shown in Image 1
  • the published curve shown in Image 2
  • the certified curve

Centrifugal pump selection guide 1

The certified curve is different from the selection chart and published curve because it is for the specific pump and impeller trim purchased and not the general product line. Often it will include the acceptance test standard and acceptance grade that the pump was tested against.

The selection chart shows the various pump sizes available for a given manufacturer’s pump line and speed. The desired head and flow rates are entered on the curve, and the pumps that overlap the area are valid choices to consider for selection. The selection chart is useful in developing a short list of pumps for consideration. For example, if the application called for a pump running at a nominal 1,800 revolutions per minute (rpm), that could provide 1,000 gallons per minute (gpm) at 100 feet of total head, the chart shows that 5 x 6 x 11 and 6 x 8 x 11 size pumps overlap on the selection chart and will likely be the two best sizes to evaluate further.

Centrifugal pump selection guide 2

Although the published curve may seem confusing, a lot of critical information can be extracted from this pump curve. If you understand the charts, you will benefit from the data they offer. Remember:

  • The Y axis (vertical) on this curve is the head in feet and meters, and the X axis (horizontal) is the capacity (flow rate) in m3/h and gpm.
  • Each downward sloping blue line is called a head capacity curve.
  • Each number above the head capacity curves to the right of the
    Y axis represent different impeller diameters. Total head is reduced when the impeller diameter is reduced.
  • The numbers in the circles above the topmost head capacity curve are the pump efficiency, and the lines stemming from these circles are lines of constant efficiency. The triangles that contain a number and word “NPSH” are constant lines of NPSH (in feet) that the system must supply for the pump to operate with a 3 percent head loss. NPSH margin above this value is required for the pump to operate at the published head.
  • The diagonal lines that run through the head capacity curves signify lines of constant pump input power.

Using the selection chart to narrow down the appropriate pump’s size for the duty point of 1,000 gpm and 100 feet of head, the manufacturer’s published curves can be referenced to help determine the best pump for an application. Image 1 shows the published curve for a 5 x 6 x 11 pump running at 1,770 rpm. Information can be derived from the manufacturer’s pump curve for this application, including the following:

  • The impeller diameter that meets the duty point falls between 10 and 10.5 inches.
  • The pump is 85 percent efficient at the rated point and 86 percent efficient at the best efficiency point (BEP).
  • At the rated point, the shaft power will be between 25 horsepower (hp) and 30 hp. To ensure a non­overloading condition at the end of the curve, a 40-hp motor may be required. NPSH3 is between 9 and 10 feet at the duty point.

Note that data displayed on a manufacturer’s pump curve is based on 68 F or 20 C water. If a liquid other than water will be pumped, information on the manufacturer’s published curve must be adjusted for the liquid density and viscosity, which affects the head, flow, efficiency and pump input power.

Centrifugal pump selection guide 3

HI Pump FAQs® is produced by the Hydraulic Institute as a service to pump users, contractors, distributors, reps and OEMs. For more information, visit pumps.org.

Horizontal Sump Pump

Keeping the Solids Out

Clogged pumps not only halt the flow of wastewater, they can also grind workflow to a halt while maintenance is performed. Using pumps that offer unrestricted flow can help keep things running smoothly. The designers of the Series 1600 industrial horizontal vortex sump pump from Vertiflo Pump Co. made the unit with the intent of keeping it in operation.

The pump’s fully recessed vortex impeller design provides an unrestricted flow since the impeller is not typically in contact with the solids being pumped. Applications for the pump include slurries, fragile food processing solids, pulpy solids, oils, pollution control and wastewater treatment. It can handle solids up to 4 inches in diameter.

“Pumping sewage, stringy product, light slurries and other soft solids is easily accomplished with the concentric volute design, offering unobstructed flow and smooth passage of the product being pumped,” says Bob Goldtrap, vice president of sales and marketing for Vertiflo Pump Co. “Pumping secondary biosolids in wastewater treatment facilities is an ideal application. It is easy and less costly to repair than competitive products.”

The Series 1600 offers heads to 170 feet, and it can operate in temperatures up to 250 degrees F with flows up to 1,600 gpm. Construction options include cast iron, 316 stainless steel fitted, all 316 stainless steel, Alloy 20 and CD4MC. The Model 1620 has a 0.875-inch shaft diameter with a 1.25-inch sleeve, while the Model 1626 has a 1.25-inch shaft diameter with a 1.625-inch sleeve. The unit is positively driven and gasketed, protecting the motor shaft from the liquid being pumped. Using any NEMA standard JP shaft motor, its standard JP shaft extension allows for easy interchangeability to packing standard mechanical seal or optional single or double mechanical seals of various designs and materials of construction. All pumps are designed with back pullout feature, which allows for the easy removal of all rotating components.

“That allows for easy inspection or service/maintenance without disturbing the piping to the pump, which is a cost-saving feature,” says Goldtrap.

All the unit’s suction and discharge openings are flanged for installation ease and integrity, while the impellers have wiping vanes that reduce axial loading and prevent dirt from entering the sealing area. Its vortex-type concentric design casing has an extra-heavy wall thickness for corrosion protection.

“Its durability and being able to pump 4-inch solids makes it a great fit in a wastewater plant,” says Goldtrap. “It’s been well-received in the industry.”

Horizontal End Suction Pump

Industrial Horizontal End Suction Pump is Easy to Install and Maintain

The Vertiflo 1400 Horizontal End Suction Pump is designed for process, pollution control, spray systems, deionized water, waste water, corrosive liquids and chemicals. Rugged heavy duty cast iron frame design incorporates integrally cast support and ribbed mounting feet which assure a solid, dependable pump installation and operation. One frame fits all pump sizes. The frame has a back pull-out design feature, which allows for easy inspection or service / maintenance without disturbing the piping to the pump. The pump has external impeller adjustment and the semi-open impeller design accommodates passage of solids or fines. All impellers have balance holes near the hub which reduce thrust load and pressure in the packing or seal area. Wiping vanes reduce axial loading and prevent dirt from entering the sealing area. Packing or various mechanical seal arrangements are available as standard options. The pump is offered in a variety of materials: Cast iron, 316 stainless steel fitted, all 316 stainless steel, or CD4MCu. Requirements for pumping clear and corrosive liquids can be satisfied with capacities ranging up to 3600 gallons per minute, heads of 275 Feet and temperatures of 250 degrees F.

Vertiflo Pump Company, 513/530-0888, Learn More.

Horizontal Centrifugal Pump

Horizontal Vortex Pump, Provides Unrestricted Flow, Impeller Not In Contact with Solids Being Pumped

Vertiflo Pump Company offers a rugged, dependable Series 1600 Industrial Horizontal Centrifugal Pump Vortex Sump for service in industrial and municipal applications. Fully recessed vortex impeller design provides an unrestricted flow since the impeller is not normally in contact with the solids being pumped. Industrial process applications include slurries, fragile food processing solids, pulpy solids, oils, pollution control and wastewater treatment. Solids handling up to 4” diameter spheres. 

The Series 1600 is designed for long life in severe services with heads to 170 feet, temperatures to 250° F with flows to 1600 GPM. Construction options include cast iron, 316 stainless steel fitted, all 316 stainless steel, Alloy 20 and CD4MC. Model 1620 has a 0.875” shaft diameter with 1.25” sleeve, Model 1626 has a 1.25” shaft diameter with a 1.625 diameter sleeve. Positively driven and gasketed, protecting motor shaft from liquid being pumped.

Use any NEMA Standard JP Shaft Motor, standard JP shaft extension allows for easy interchangability to packing, standard mechanical seal or optional single or double mechanical seals of various designs and materials of construction. All pumps are designed with back pull-out feature which allows for removal of all pump rotating components without disturbing the piping connections.

All suction and discharge openings are flanged for installation ease and integrity. All impellers have wiping vanes which reduce axial loading and prevent dirt from entering the sealing area. Impeller is keyed to shaft, and an impeller locking screw assures positive attachment. Vortex-type concentric design casing has extra heavy wall thick-ness for corrosion allowance. Three brackets fit all pump sizes.

All Vertiflo pumps are delivered fast, usually shipped in one-half the typical lead time. 

Vertiflo Pump Company, 513-530-0888, www.vertiflopump.com

Sewage Ejector Pump

Industrial Vertical Non-Clog Sewage and Waste Ejector Pumps with Heads to 100 feet

The Vertiflo Pump Company offers a rugged, dependable Model 700 industrial vertical non-clog sewage ejector pump for service in industrial wastes, sanitary wastes, process wastes and rendering wastes. The Model 700 is designed for long life in tough services with heads to 100 feet TDH and flows to 1500 GPM. 1.5 inch (Model 724) and 1.25 inch (Model 720) diameter shaft sizes are standard. The impeller is a fully enclosed two vane non-clog design with wiping vanes which reduce axial loading and prolong bearing life. Wiping vanes aid in keeping particles from behind impeller and pump bearing assembly. The impeller is secured to the shaft by taper fit with woodruff key/nut. There is a flanged discharge on all sizes. Designed specifically for solids handling, the 700 Series incorporates a long radius elbow, reducing friction loss and allowing smooth flow thru the discharge pipe.

The 700 Series has high-thrust angular contact ball bearing, external impeller adjustment and grease lubricated pump and line shaft bearings. Pump setting increments of 1′-0″ for sump depths up to 26′-0” are offered. The standard pump lower bearing assembly consists of a choker ring and two guide bearing bushings compatible with the liquid. The standard intermediate bearing assembly consists of two guide bearings compatible with the liquid and is standard when pump length exceeds 6 feet. Standard bronze bearings come with grease lubrication. Rubber or carbon graphite are optional.

Vertiflo Pump Company’s vertical, horizontal and self-priming pumps are delivered fast, usually in half the typical lead time!

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.

Vertiflo Pump Company, Inc. was established in 1979 to design, sell and build packaged lift stations. Since 1981, Vertiflo has concentrated on manufacturing vertical process pumps, sump pumps, end suction pumps and self-priming pumps in cast iron, stainless steel and special alloys.

Close Coupled Horizontal End Suction Pumps Ideal for Transfer of Water and Fertilizer Solutions

Close Coupled Horizontal End Suction Pumps Ideal for Transfer of Water and Fertilizer Solutions

The Vertiflo Pump Company offers a rugged, dependable Model 1312 Industrial, close-coupled, horizontal, end suction pump for service in general pumping, chemicals, wash systems, deionized water, process and OEM applications. This pump is especially useful for pumping liquid fertilizer from tank to tank and into transport delivery trucks. The Model 1312 is designed for long life in tough services with heads to 160 feet TDH and flows to 240 GPM. 1750 and 3500 RPM sizes are available. 

Back pull-out design construction allows rotating element to be easily removed, casing remains in piping. Casing may be rotated in 90° increments to accommodate various piping and discharge orientation options or requirements. The close-coupled design saves installation space. Suction and discharge connections are threaded NPT. 

Construction options include cast iron, 316 stainless steel fitted or all 316 stainless steel. Pump volute, impeller and mounting bracket are heavy cast metal. 

Model 1312 horizontal motor-mounted end suction pumps are designed for use with NEMA standard C-face electric motors. Standard size mechanical seal is a self-aligning design. Semi-open impeller with balance hub is secured to shaft by taper and threads. 

All Vertiflo pumps are delivered fast, usually shipped in one-half the typical lead time.

Vertiflo Pump Company, 513-530-0888, www.vertiflopump.com

Close Coupled Horizontal End Suction Pumps Ideal for Transfer of Water and Fertilizer Solutions
Close Coupled Horizontal End Suction Pumps Ideal for Transfer of Water and Fertilizer Solutions
Pump System Testing graph

Understanding the New DOE Pump System Testing Procedures

This is the first time the DOE has developed rules to determine the efficiency of pump systems.

by Thomas Lowery & Jack Creamer, from PUMPS & SYSTEMS

After many years of study, analysis and discussion, the U.S. Department of Energy (DOE) has released new rulemaking that defines a pump system efficiency test procedure, 10 CFR Parts 429 and 431 – Energy Conservation Program: Test Procedure for Pumps.

Energy conservation has been a focus for both the private and public sectors for years, but this is the first time the DOE has developed rules to determine the efficiency of pump systems.

Pumps represent more than 50 percent of all potential energy savings of motor-driven loads. Furthermore, energy costs associated with pumping applications represent approximately 40 percent of the total cost of ownership for the life of that pump.

Because pumps are a major consumer of electric energy, the DOE pump system guidelines have been the topic of discussion for several years. This is the first time that the government has taken steps to address energy usage in the previously unregulated pump industry.

This rule does not include information on any action that the DOE will take against inefficient systems; however, it lays the groundwork for future rules detailing efficiency level requirements and subsequent penalties for noncompliance. Many pump users remember the process that the DOE and the Environmental Protection Agency (EPA) underwent to develop minimum efficiency standards for electric motors nearly a decade ago and the resultant laws governing minimum allowable motor energy use as detailed in 10 CFR Part 31 of the 2010 Energy Conservation Standard for small electric motors.

The process started with the Energy Policy Act of 1992, which required that certain types of motors sold in the U.S. after October 1997 meet or exceed minimum efficiency standards.

Efficiency guidelines continued to expand with the Energy Independence and Security Act, setting the minimum efficiency for motors above 1 horsepower (hp) (signed in December 2007), followed by the DOE Small Motor Rule that set minimum efficiency requirements for certain electric motors between 0.25 and 3 hp in 2015.

Measuring Pump System Efficiency
Pump system efficiency typically has been measured only when a system is operating at 100 percent capacity (speed, flow and head pressure).

This full load and speed point of operation, while important, did not represent where most installed pump systems ran for long periods of time. Even if throttle valves or other mechanical bypass means were used to vary system flow and pressure, the overall system rarely ran at 100 percent capacity.

This new efficiency test procedure requires that measurements be taken at different key load points, gauging the system’s efficiency at varying loads to provide a more holistic understanding of the pump system’s overall energy use.

Addressing Pump System Efficiency
This rulemaking will be applied to new pump systems and will not mandate any updates to installed pumps. The regulations underscore the importance of energy efficiency for all pumping systems across all industries—both to reduce environmental impact and to improve the bottom line.

Schneider-Electric-table-for-0616 - Pump System Testing
Table 1. Load profiles based on pump configurationTable 1. Load profiles based on pump configuration

Fortunately, most pumping systems can be adapted to increase system efficiencies without incurring high installation costs associated with replacing mechanical equipment.

Technologies designed to increase process efficiency and provide detailed information on energy use have been evolving. One such technology is modern variable frequency drives (VFDs), devices designed to electronically vary a motor’s speed to match demand within a given process. VFDs have become an important contributor to overall pump system efficiency gains without sacrificing system performance.

Schneider-Electric-graph-for-0616 - Pump System Testing
Figure 1. For energy savings opportunities on motor-driven loads, pumping applications account for slightly more than 50 percent of all savings.Figure 1. For energy savings opportunities on motor-driven loads, pumping applications account for slightly more than 50 percent of all savings. (Courtesy of Schneider Electric)

In addition to the motor control functions, VFDs can offer greater insight into the level of efficiency for their respective processes. With that knowledge, the process owner can make changes to run the system more efficiently.

Contributing to the Guidelines

As with the majority of federal guidelines, this rule was developed through years of study and with the input of independent industry groups. The Air-Conditioning, Heating and Refrigeration Institute (AHRI) is one group prominently referenced in the legislation. This rule comes on the heels of that organization’s recently published VFD standard, AHRI Standard 1210 (IP) and 1211 (SI) Performance Rating of Variable Frequency Drives, which addresses system efficiency by focusing on the drives.

By adding a VFD, it is possible to reduce a pumping system’s electrical consumption by at least 30 percent. However, it was difficult to understand which drives provide greater process efficiency.

The AHRI standard represented the first independent, nationally recognized performance standard in the industry for VFDs, allowing users and consulting engineers to better specify VFDs based on published performance data verified by credible third-party testing. To achieve the Standard 1210/1211 Certification, manufacturers must complete a detailed process, including independent testing of three VFD measurements:

  1. Combination drive/motor efficiency at defined speed and load points
  2. Total harmonic current distortion at drive input terminals
  3. The rate of voltage change over time (Dv/Dt) of drive output waveform measured at motor input terminals with 6-, 15- and 30-meter cable lengths

The first of these three criteria seeks to reach the same goals as the new DOE testing method—measuring efficiency at different defined load points. This is a critical point because the DOE guideline states that “AHRI 1210–2011 specifies appropriate power supply tolerances so that both pump manufacturers and DOE enforcement testing can be confident with the establishment and verification of ratings of VFDs sold with pumps.” This means that, when the DOE begins to require system efficiency verification, those with AHRI-certified VFDs in their systems will be able to reference the independently verified AHRI data from the certification process to show that their systems meet the DOE requirements.

The option available for those not using AHRI-certified systems is to test and verify compliance using the new method of test, which can be costly, time-consuming and cumbersome for multiple sizes and types of each component: the VFD, motor and pump.

References
ASHRAE Journal, Feb. 2016; p.58-59