Pump Selection and Specifications

Pump Selection Criteria 

For sanitary processing, quick and efficient cleanability is critical when choosing a pump. To ensure a hygienically and microbiologically perfect condition of the final product, high standards are applied to centrifugal and PD pumps with regard
to hygiene and cleaning requirements. The surface finish influences the cleanability of pump parts. Cleaning times will decrease with improved surface finishes. Pumps for food, beverage or pharmaceutical industries are constructed of 316L stainless steel or alloys which provide a homogenous, pore-free surface. The product chamber should have no gaps or dead ends. Seal rings must be clamped in a way that they can be cleaned by the CIP solution. Non-metallic seals are typically made of NBR, EPDM, PTFE or FPM.1

The main purposes for creating sanitary design in pumps are to:
· make sanitation programs faster;
· make sanitation programs more efficient;
· make sanitation programs more economical;
· help prevent product adulteration;
· help satisfy regulatory requirements;
· help satisfy consumer/customer audits, demands and requirements.


Additionally, accrediting organizations, such as 3A, EHEDG, and the FDA, publish guidelines meant to specify the
technical requirements of pumps and other processing equipment. Full guidelines can be found on these organizations
websites.

Pump Specifications and Selection 

Pumps are commonly rated by horsepower, capacity or flow rate (US gallons per minute), outlet pressure (defined as meters or feet of head), and inlet suction (defined as suction meters or feet of head). The head can be simplified as the number of feet or meters the pump can raise or lower a column of water at atmospheric pressure.

Total Suction Head

where:
hs = static suction head
> 0 for flooded section
< 0 for flooded section
hfs = pressure drop in suction line
ps > 0 for pressure
ps < 0 for vacuum
ps = 0 for open tank

NBR – nitrile rubber; copolymer of butadiene and acrylonitrile; EPDM – Ethylene propylene diene rubber; a terpolymer of ethylene,
propylene and a diene-component; FPM – fluorinated propylene monomer; commonly sold under the trade name Viton®; PTFE –
polytetrafluoroethylene elastomer; commonly sold under the trade name Teflon®

Total Discharge Head

where:
ht = static discharge head
hft = pressure drop in discharge line
pt > 0 for pressure
pt < 0 for vacuum
pt = 0 for open tank

Total Head

where:
Ht = total discharge head
Hs = total suction head

From an initial design point of view, engineers often use a quantity termed the specific speed to identify the most suitable pump type for a particular combination of flow rate and head. Therefore, to ensure you choose the right pump for the application, the following is a list of questions you will need to answer.


Material Properties
What is the material being pumped?
What is the material viscosity?
What is the material density or specific gravity?
What is the particle size?
What is the temperature of the material?
Is the material abrasive?


Process Conditions
What is the desired flow rate?
Where is the feed tank relative to the pump?
What is the suction lift distance?
What is the head pressure?
What is the discharge distance?
What is the inlet and outlet hose diameter?


Other Considerations
What certifications are required (FDA, 3-A, EHEDG)?
Will it be used for COP or CIP?
What is the desired price range?
What is the pressure of the shop air?
Who will clean and service the pump?
What special applications need to be considered?


With these questions and answers in hand, you can discuss the best pump choice with one of our engineers.

If you want more information, contact us by phone or email. 

Day in the Life of a Control Systems Engineer

A Control Systems Engineer is keeping things under CONTROL at M.G. Newell. 
Take a look behind the scenes of a day in the life of Raymond Bennett working as a Control Systems Engineer. 

What is a typical day for a control systems engineer at M.G. Newell?

My typical day revolves around project management from the controls perspective. I balance and manage multiple projects, all with unique challenges and constraints. This project management manifests in customer correspondence trying to determine the best solution for their needs, cooperating with internal team members to ensure that our approaches align constructively with one another to facilitate what our end user not only needs but also wants, and of course, what I love most, designing and creating unique solutions to unique challenges. When I am not waist-deep in project work, I spend any spare free time taking advantage of any trainings or research I can. Our industry is constantly evolving, and we as controls engineers must constantly evolve with it.

 If someone is interested in becoming a control systems engineer, what is one piece of advice you’d give them?

Be Curious Always.

No degree is a good substitute for wanting to learn and know—every great engineer I have had the pleasure of working with has wanted to know. Having answers is never as good as being able to find the answers.

What is your favorite thing about your job?

I get paid to solve complex puzzles that change day by day and sometimes hour by hour. Every time I think I have seen it all, I am greeted with another new brain teaser. In addition to this, I have the opportunity to collaborate with fellow engineers, technicians, and fabricators every day, which enriches my life with fresh perspectives and valuable lessons that I would not otherwise encounter. Or in less flowery language, I get to do the work I love with people I like!

How long have you been a control systems engineer at M.G. Newell, and what education or background did you have to have to get this job?

I have been with Newell since November of 2024—I come from a diverse background of manufacturing, robotics, machine vision, and controls that I believe aligned and still align with our goal to venture into more non-process projects. I believe some of the other selling points that led to my hiring were less rooted in my technical capabilities and more so from my appetite for growth and continuous improvement. I originally went to school for film production but veered into electronics engineering technology shortly after starting my academic career because of how interesting I found the multidisciplinary curriculum. Academic pursuits with a bachelor’s degree in electrical engineering from FSU—I have consistently found that my associates have served me better from a practical standpoint, but my bachelor’s has gifted me with boundless resourcefulness in the face of confusion.

For more information, visit our website:  www.mgnewell.com and www.newellautomation.com.

Pump Repair Training – Case Study

Pump Repair Training – Case Study 

A customer was having a difficult time with positive displacement pumps needing frequent and costly repairs. After discussions with the plant engineer and sanitation, we felt we had a good grasp on the cause of the problem.

That is where Pump Repair Training comes in. 

The plant had experienced a change in personnel over the last 3 – 6 months on both the sanitation and maintenance staff. Some of the basic steps in disassembly and reassembly had not been properly performed along with missing preventive maintenance steps. The pumps were able to perform, but damage was occurring causing inefficiencies and expense in the upkeep.

Preventative Maintenance

We review our findings with the plant engineer. We don’t suggest a new pump. Instead, we determine that a “refresher” training course is needed to make sure everyone knew the proper sequence of assembly and proper preventive maintenance requirements of positive displacement pumps.

The hands-on pump repair training, proves to be the key in getting the process to turn around and reduce the occurrence of breakdown. This has led to lower maintenance cost and more production operating time. We sometimes lose sight of the “basic” practices that keep our operations functioning smoothly. It is very important that routine training programs and PM plans are in place to review equipment procedures that keep your process running smooth, safe, and cost effective.

M.G. Newell and our equipment manufacturers offer plant audits that help assist you in maintaining your equipment and provide training and preventative maintenance programs. We realize in this “challenged” economy that everyone is looking for ways to tighten their process parameters and keep costs down. This is just another way that M.G. Newell makes it work better.

If you want more information, contact us by phone or email. 

Pump Rebuild vs Pump Remanufacture

Pump Rebuild vs Pump Remanufacture

Pump Rebuild and Pump Remanufacture is offered at SPX Flow, in conjunction with M.G. Newell, on standard WCB positive
displacement pumps. These options allow you to get a longer life from your pump and reduce the cost of product
ownership.

Pump Rebuild

Pump rebuilds are performed by M.G. Newell in any of our 3 locations – Greensboro, Louisville or Nashville. As a SPX Certified Repair Center, M.G. Newell has qualified factory service technicians on staff with over 30 years of experience. We invest in equipment, inventory and training to become one of a select group of distributors that are approved. In a rebuild, we pull the shafts, replace the bearings and all wear items. Depending on the amount of wear, we also replace the rotors. Our shop will perform an evaluation of the pump and provide you with an estimate to rebuild your pump. The cost of a rebuild is approximately 50% of the cost of a new pump. The only drawback to a pump rebuild is a slight loss in its original efficiency.

Pump Remanufacture

Pump remanufacture is performed by SPX Flow at their factory. In this program, they only reuse four parts: the SS cover, body, gear case and gear cover. The remaining components are completely replaced with new, original equipment parts manufactured to factory specifications. They bore the existing body and make new oversized rotors. This machining is the main difference between a rebuild and remanufacture. When complete, the pump is back to its original performance specifications and has a new 1-year warranty from SPX Flow. Due to the new oversized body, standard rotors should not be used due to potential damage or failure of the pump. A pump can be remanufactured two times in its lifetime. The cost of a remanufactured pump is approximately 75% of the cost of a new pump.

If you want more information, contact us by phone or email. 

Pump Problem Solving

Pump Problem Solving – Cavitation 

For all pump application problems, cavitation is the most common issue we encounter. It occurs with all types of pumps – centrifugal, rotary or reciprocating. Cavitation is the formation of vapor cavities in a liquid – i.e. small liquid-free zones (“bubbles” or “voids”) – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of bubbles where the pressure is relatively low. These bubbles are carried along by the fluid and implode instantly when they get into areas of higher pressure.

According to the Bernoulli Equation, this may happen when the fluid accelerates in a control valve or around a pump impeller. Cavitation can result in a loss of pump efficiency/flow, noise and possible damage to the pump and/or system. The vaporization itself does not cause the damage – the damage happens when the vapor almost immediately collapses when the velocity is decreased and pressure increased. When a pump cavitates, the vapor bubbles move toward the impeller where they collapse. 

This causes a physical shock which creates small pits on the edge of the impeller. Each individual pit is microscopic in size, but the cumulative effect of millions of pits over a period of time can destroy a pump impeller. Cavitation can also cause excessive pump vibration which damages bearings, wearing rings and seals. Noise is typically the indication that a pump is cavitating. Other indications that can be seen include fluctuating discharge pressure, flow rate and pump motor current. Excessive pump speed and/or adverse suction conditions will probably be the cause.

Suggestions for avoiding or minimizing cavitation:
 Use the 1.5 multiplier for suction tubing (a 2” pump should have a 3” suction tubing and reduce to 2” at the pump)
  – Note – this could cause excessive pump sizing for CIP flow rate. This is only recommended when cavitation is a concern.
 Use the 7 to 10 diameter rule for straight tubing. No elbows directly into the pump.
 Fluid viscosity kills – stay under 5 feet per second.
 Maintain a static head as high as possible.
 Reduce fluid temperature, although caution is needed as this may have an effect of increasing fluid viscosity, thereby increasing pressure drop. If cavitation is a concern, it is strongly recommended that you contact an engineer to review your process.

Pressure ‘Shocks’ (Water Hammer) 

The term “shock‟ is not strictly correct as shock waves only exist in gases.

The pressure shock is really a pressure wave with a velocity of propagation much higher than the velocity of the flow, often up to 1400 m/s for steel tubes. Pressure waves are the result of rapid changes in the velocity of the fluid in especially long runs of piping.

The following causes changes in fluid velocity:
• Valves are closed or opened
• Pumps are started or stopped
• Resistance in process equipment such as valves, filters, meters, etc
• Changes in tube dimensions
• Changes in flow direction

Most pressure wave problems are due to rapidly closed or opened valves. For example, when a valve is closed, the pressure wave travels from the valve to the end of the tube. The wave is then reflected back to the valve. These waves gradually weaken due to friction in the tube. Pumps, which are rapidly/frequently started or stopped, can also cause some problems. A pressure wave resulting from a pump stopping is more damaging than for a pump starting due to the fact that a large change in pressure continues much longer after a pump is stopped compared to a pump starting. A pressure wave induced as a result of a pump stopping can result in negative pressure values in long tubes, i.e. values close to the absolute zero point which can result in cavitation if the absolute pressure drops to the vapor pressure of the fluid. When designing pipework systems it is important to keep the natural frequency of the system as high as possible by using rigid pipework and as many pipe supports as possible.

Effects of pressure waves:
• Noise in the tube

• Damaged tube

• Damaged pump, valves and other equipment

• Cavitation.

Slip

Slip occurs in PD pumps when fluids passes from the discharge side back to the inlet side of the pump through the pump clearances. It is the difference between the theoretical displacement and the actual displacement. Slip is caused by three factors:

 Viscosity – Slip will decrease as fluid viscosity increases; the
reduction eventually reaches a point called “zero slip”.
 Pressure – Slip will increase with pressure increases
 Clearance – Increased clearances will result in greater slip.
The size and shape of the rotors will be a factor.

If you want more information, contact us by phone or email. 

Pump Pressure Issues – Case Study

Pump Pressure Issues – Case Study

Inconsistent product output? Breaking pipe hangers and ferrules?

These system hammer issues can often be traced back to pump and pressure issues.

A producer of ingredients for human food and animal nutrition was having major issues in their process. They were inducting powdered maltodextrin into their process to form a starch slurry. During the maltodextrin induction process, air was getting into their PD pump. It was then pulled into a centrifugal booster pump that was pushing the slurry vertical 40 feet into a tank. They were experiencing low flow rates (30-60 gpm) and high pressures (>120 psi).

The product was building up in the pump housing seals. Product output was inconsistent. They were breaking ferrules and hangars. They had long periods of downtime. Operators were trying to overspeed the motors on the pumps to increase production rates.

The M.G. Newell salesman recommended that the customer consider a twin-screw pump. Twin-screw pumps can handle highly viscous products such as starch slurries. The design minimizes shearing in the product while still handling high pressures and higher speeds. Most importantly, the pump can handle any air that may be pushed into the line from the powder induction system. The customer removed the PD pump and the centrifugal booster pump and replaced them with 2 twin-screw pumps. They also switched 2” tubing and ball valves to 3” tubing and added an overpressure valve after the first pump.

After one month, the customer loves the new process improvements. They are maintaining a more consistent flow rate of 80-110 gpm and lower pressures of 60 psi. Production increased by 26% with more consistent product and a quieter production area. Maintenance and downtime decreased by 30%.

If you are frustrated with extended maintenance and downtimes, give us a call. We are happy to share our experience with you. Contact one of our associates to see how We Make It Work Better.

If you want more information, contact us by phone or email. 

The Pump Overview Part 2

The Pump Overview Part 2

As we continue the Pump Overview series, let’s review a few basic principles of pumps.
Pressure, friction and flow are three important characteristics of a pump system. Pressure is the driving force responsible
for the movement of the fluid, expressed as pounds per square inch (psi). Friction is the force that slows down fluid
particles. Flow rate is the amount of volume that is displaced per unit time, usually expressed as gallons per minute.
Pumps are typically classified by the way they move fluids. For the sanitary industry, we will only focus on positive
displacement pumps and centrifugal (or rotodynamic) pumps. Positive displacement pumps include single and double
rotary lobe pumps and diaphragm pumps. The table below outlines a few of the basic differences between these pumps.

Centrifugal pump

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system.

A typical centrifugal pump has five basic parts:
1. Casing – also known as the volute, is the outside visible part of the pump. For sanitary processing, the casing is typically a heavy-walled 316L stainless configured in a spiral design to even out flow and minimize turbulence. The end cover is clamped on and can be easily removed for access to the impeller.

2. Impeller – The impeller is the main rotating part that provides the centrifugal acceleration of the product. The impeller can have an open or closed vane. Generally closed vane impellers develop higher pressures but have a lower capacity. Open vane impellers develop lower pressure but have a higher capacity. It is attached to the shaft and rotates inside the casing at the speed of the shaft. The design is balanced to prevent vibration.

3. Shaft – The shaft rotates insides the casing at the speed of the motor and transfers the torque from the motor to the impeller. The shaft is typically made of 316L stainless.

4. Bearings – The bearings support the shaft and keep it in alignment so that it does not wobble inside the casing and prevents it from touching the casing.

5. Seals and/or Packing – The seals are the essential area in terms of hygiene as they prevent the product from leaking back inside the pump or outside of the pump when it is under pressure. Pumps can have either single-seal or double-seal arrangements.

 

How does a centrifugal pump produce pressure?

The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser or volute chamber, from where it exits into the downstream piping system.

The velocity of the fluid is also partly converted into pressure by the pump casing before it leaves the pump through the outlet. Pressure is produced by the rotational speed of the impeller vanes. The speed is constant. The pump will produce a certain discharge pressure corresponding to the particular conditions of the system (for example, fluid viscosity, pipe size, elevation difference, etc.).

If changing something in the system causes the flow to decrease (for example closing a discharge valve), there will be an increase in pressure at the pump discharge because there is no corresponding reduction in the impeller speed. The pump produces excess velocity energy because it operates at constant speed. The excess velocity energy is transformed into pressure energy and the pressure goes up.

Centrifugal pumps are typically used for large discharge through smaller heads. Centrifugal pumps are most often associated with the radial-flow type. However, the term “centrifugal pump” can be used to describe all impeller type rotodynamic pumps.

Therefore, the main factors that affect the flow rate of a centrifugal pump are:
 Friction, which depends on the length of pipe and the diameter
 Static head, which depends on the difference of the pipe end discharge height vs. the suction tank fluid surface height
 Fluid viscosity, if the fluid is different than water.

Typically, centrifugal pumps are selected for:

If you want more information, contact us by phone or email. 

The Pump Overview Part 1

The Pump Overview Part 1 

A pump is simply defined as a device that raises, transfers, delivers, or compresses fluids or that attenuates gases especially by suction or pressure or both. Pressure, friction and flow are three important characteristics of a pump system. Pressure is the driving force responsible for the movement of the fluid. Friction is the force that slows down fluid particles. Flow rate is the amount of volume that is displaced per unit time.

Pumps are typically classified by the way they move fluids. For the sanitary industry, we will only focus on positive displacement pumps and centrifugal (or rotodynamic) pumps. Positive displacement pumps include single and double rotary lobe pumps and diaphragm pumps. The table below outlines a few of the basic differences between these pumps.

Positive Displacement Pump

A positive displacement (PD) pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe.

Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant through each cycle of operation.

Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, theoretically can produce the same flow at a given speed (RPM) no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. However, a slight increase in internal leakage as the pressure increases prevents a truly constant flow rate.

For each revolution of the pump, a fixed volume of liquid is moved regardless of the resistance against which the pump is pushing. Therefore, a positive displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A PD pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is severely damaged, or both.

A relief or safety valve on the discharge side of the positive displacement pump is therefore necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve is usually only used as a safety precaution. An external relief valve in the discharge line, with a return line back to the suction line or supply tank provides increased safety. PD pumps are designed with very small clearances between the rotating lobes and the stationary parts to minimize leakage (slippage) from the discharge side back to the suction side. They are designed to operate at relatively slow speeds to maintain these clearances; operation at higher speeds causes erosion and excessive wear, which result in increased clearances with a subsequent decrease in pumping capacity.

When would you choose a PD pump? Typically, PD pumps are selected for the following scenarios:

Diaphragm Pumps

A diaphragm pump (also known as a Membrane pump, Air Operated Double Diaphragm Pump (AODD) or Pneumatic Diaphragm Pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic or Teflon® diaphragm and suitable valves either side of the diaphragm (check valve, butterfly valves, flap valves, or any other form of shut-off valves) to pump a fluid. This implies that the pump will deliver a specific amount of flow per stroke, revolution or cycle.

Air operated double diaphragm pumps have the following components:
 Air chambers: The pump has two chambers, one on the left side and the other on the right side of it. These chambers let the compressed air flow in and out of it.
 Air valve: The compressed air is directed to air chambers with the help of air valves. These have a valve cup and a valve plate. Air valves make sure that the compressed air enters the air chambers and leave from it through the exhaust port

 Check valve: There are four fluid check valves in a double
diaphragm pumps. Two of them are inlet check valves while the other two are outlet check valves. The flow of liquid in the fluid housing and manifolds is controlled by these check valves.
 Fluid housing: Each pump has fluid housing, one at each side of the pump. As the name implies, fluid housing is that part which holds the fluid and makes it flow through the pumping mechanism.
 Inlet manifold: Fluid enters the pumping container via the inlet manifold and flows evenly to the left and right fluid housing. This mechanism makes the distribution of fluid equal so that both fluid housings remain in operation.
 Outlet or Discharge manifold: When the fluid is coming out of the container, it passes through a couple of components. First, the fluid passes through one of the exit check valves and then this check valve directs the fluid to the outlet manifold to finally exit the container altogether.
 Diaphragms: The air operated double diaphragm pump obviously has two diaphragms in it. The diaphragm is actually a kind of a separation sheet in between the air chambers and fluid housings. The diaphragms are good enough to adjust
themselves according to the rise or fall of the air pressure, as the condition may be. Besides, the two diaphragms are allied with a shaft.
 Muffler: The objective of muffler is to control noise of the exhaust air. There are multiple mufflers available that offer several levels of noise reduction to ensure effective and efficient pumping operation.
 Exhaust port: The exhaust port is the final exit point in the pump.

How Does An Air Operated (Double) Diaphragm Pump Work?

Using compressed air as the resource to operate, double diaphragm pumps are meant for low pressure activities mainly. A vacuum is formed inside the pump casing each time the diaphragm is raised. This allows the inlet valve to open and seals the discharge valve thus allowing water and air to enter the pump. Whenever the diaphragm is lowered the resulting pressure seals the inlet and opens the outlet valve purging the pump housing of water and air.

In summary, the process is given below:
1. Chambers are filled with fluid and then emptied through an ongoing process. This is done through inlet and outlet manifolds.

2. The shaft joining the left and right diaphragms in each chamber enables them to move to and fro continuously.

3. Compressed air is directed to one of the diaphragms.

4. Eventually as the suction stoke occurs, the lower ball valve opens and the top one closes. Simultaneously, fluid enters the chamber through the inlet manifold.

5. When air enters the other diaphragm, the top ball valve opens and the lower one is closed. This allows the fluid to exit through the outlet manifold.

6. The same process repeats with the other chamber and it goes in cycles between the two chambers

When would you choose a diaphragm pump? 

The compressed air design gives diaphragm pumps the ability to run without electric power. Otherwise, diaphragm pumps offer many of the same benefits of a traditional lobe-style PD pump. They have a low initial cost, are easy to maintain and simple to install. They can handle shear-sensitive products and have the ability to process delicate materials without damage to the product. Diaphragm pumps are self-priming with excellent flow rates. Common applications include ingredient unloading (tote or drum unloaders), filler feeding and batch metering processes.

Diaphragm pumps:
• have good suction lift characteristics
• are able to handle a wide range of pressures and can deliver flow rates up to 300 gpm, dependent on the effective working diameter of the diaphragm and its stroke length.
• have good dry running characteristics.
• can be up to 97% efficient.
• have good self-priming capabilities.
• can handle highly viscous liquids (up to 1,000,000+ cps). A viscosity correction chart can be used as a tool to
help prevent under-sizing AODD pumps.

If you want more information, contact us by phone or email. 

Optimize Centrifugal Pump System Efficiency

Optimize Centrifugal Pump System Efficiency 

Take steps to reduce energy consumption, lower maintenance costs and improve process control 

Most chemical plants are working to become more energy efficient. Companies are implementing energy management software, installing occupancy sensors throughout plants to help lower electricity bills, and even changing times of operation to use less power at peak load to avoid the associated higher rates. One of the best ways to save energy is to focus on motor-driven pumps. Pumps consume more energy in chemical plants than any other category or type of rotating equipment. The average annual spending on pump maintenance and operations is approximately 50% greater than that of any other rotating machine, according to a recent study by the FiveTwelve Group. Companies that operate large numbers of pumps usually recognize the high energy costs as well as the impact pumps have on reliability and process control. However, too many organizations focus on these factors separately when, in fact, they are closely linked. A recent report on the use of motor efficiency technologies by the U.S. Department of Energy’s Industrial Technologies Program (ITP) contained an in-depth analysis of energy use and savings potential by market segment and industry. The report identified centrifugal pumps as the largest consumers of motor energy (Figure 1). Also, among all rotating assets in the plant, process pumps had the highest overall potential for electrical energy savings.

A separate Finnish Research Center study of centrifugal pump performance found that the average pumping efficiency was less than 40% for the 1,690 pumps reviewed in 20 different plants across all market segments. That study also revealed that 10% of the pumps were operating at less than 10% hydraulic efficiency. Considering this sizable efficiency loss, you can expect that from 10% to 20% of the pumps in any continuous process plant are candidates for optimization. More than likely, the real number is much higher. In the largest continuously operating process plants, opportunities for cost reduction—when all aspects of the system are considered —can easily represent millions of dollars and, thus, significantly impact the bottom line. Efforts to improve reliability and achieve optimization of pumping systems invariably involve addressing what is called the
―energy and reliability nexus.‖ In general, mechanical energy in excess of that required for moving process fluid through the pipes is manifested as vibration, heat and noise. This excess energy becomes a destructive force that undermines
pump and process reliability. As a result, pump systems routinely have the highest overall maintenance cost compared to other motor systems, including control valves, instrumentation and other types of process control equipment. In addition, pumps and valves are the primary process leak paths for fugitive emissions. 

LIFECYCLE ANALYSIS

Today, companies increasingly are relying on lifecycle costing (LCC)
for selecting an optimal solution to create economic and
environmental value over the life of a system. Using a lifecycle-cost
perspective during initial system design will minimize operating
costs and maximize reliability. For pump systems, using LCC makes
particular sense because the initial purchase price typically
represents only about 10% of long-term costs.

A LCC analysis assesses the cost of purchasing, installing, operating, maintaining and disposing all the system’s components. Determining the LCC of a system involves using a methodology to identify and quantify all the components of the LCC equation. For instance, the equation provided in the Hydraulic Institute’s ―Pump Life Cycle Costs: A Guide to LCC Analysis for Pumping Systems‖ includes terms for initial cost or purchase price (e.g., the pump, pipe, auxiliaryequipment); installation and commissioning costs (including training); energy costs (predicted for entire system, including controls); operating costs (labor man-hours for normal system supervision); maintenance costs (e.g., parts, tools, labor man-hours); downtime costs (loss of production); environmental costs (leakage losses and permit violations); and decommissioning costs (disassembly and disposal).

Energy consumption is a major element in pump lifecycle costs. Because excess energy consumption leads to higher maintenance costs, these two elements combined typically dominate total lifecycle cost. Thus, it’s important to determine
the current cost of energy and the expected annual escalation in energy prices over the system’s projected life, along with labor and material costs for maintenance.

Today, pump and automation suppliers, either individually or in partnership, provide customized services to help customers identify, qualify and quantify a pump system’s cost of ownership. Moreover, forward-thinking vendors are viewing their offerings as a holistic package of goods and services, providing the appropriate mix of products, information, training, customer service and personal attention to fully address the customer’s needs.

PROPER SIZING

Improper sizing often is the major culprit when it comes to pump inefficiency. Over-sizing of process pumps frequently occurs because parameters aren’t fully defined as the pumps are being specified.

Ideally, every pump should operate at its best efficiency point (BEP) at all times but often this isn’t a likely scenario. To maximize the return on an efficiency program, it’s important to know which pumps are most in need of attention and whether they possess far more or less flow capacity than optimum.

Consider, for instance, a pump for delivering 5,000 gpm of water at 100 ft. The right-sized pump may offer an efficiency of 70% and require 180 hp (133 kW). If, instead, the pump system is over-sized (excess capacity) and throttled (lower efficiency), efficiency may drop to 40% and brake horsepower may rise to 315 hp (232 kW). That difference of 135 hp or 99 kW (75% excess energy) will contribute to unreliability and poor control performance that continuously degrades over time.

Excess energy moving through the system often gives rise to tell-tale symptoms — including a highly throttled control valve in combination with pronounced pipe movement, or even a vibrating catwalk attached to plant infrastructure that’s
used to brace the throttled pump. Cavitation inside the pump, control valve or piping itself is a clear indication that hydraulic turbulence or instability exist.

If the system’s flow is too high coming out of the pump, some users choose simply to throttle the flow using a valve on the discharge side. This is a very inefficient and costly way to configure a system. It increases energy costs for operating the pump, reducing the operating life of the equipment and boosting downtime. Pumps are designed for specific hydraulic flow ranges. When a pump is operating optimally at its BEP, liquid flow is constant and radial forces acting on the impeller are balanced and minimized. As the pump is operated further away from its BEP, the radial and axial loads on the impeller rise. These increased loads can cause shaft deflection, which raises stress on the pump’s bearings and mechanical seal and accelerates the likelihood of pump failures.

MONITORING AND MAINTENANCE

Pump equipment condition is the most important factor for overall system efficiency. Today, various methods exist to monitor temperature, vibration and general health of rotating equipment —and diagnostics are becoming easier.

Maintaining reliable pump operations requires deploying a robust program that combines monitoring basic machine-health data in addition to pump operating conditions. The program should address four areas:

1. Pump performance monitoring. To better understand how a pump is performing, monitor five parameters — suction pressure, discharge pressure, flow, pump speed and power. Regularly checking suction and discharge pressure is essential for determining the total dynamic head (TDH) and the available net positive suction head (NPSHa), keeping the pump efficient throughout use. Permanent flow meters often are the best option for effective flow monitoring. If you’d like a temporary solution, go with clamp-on flow meters. For power measurements, consider using more than just transducers for monitoring. Assess factors such as input voltage, power factor and motor efficiency to accurately determine the actual shaft horsepower being transmitted to the pump. Pump speed also plays a role —the change in power should be proportional to pump speed.

2. Vibration monitoring. The vibration level of a pump directly relates to where it’s operating on its associated performance curve. In essence, high vibration levels indicate poor performance. To avoid future issues, take a vibration reading when a
pump is installed. This initial reading provides the baseline for future monitoring.

3. Bearing temperature monitoring. The best way to monitor pump bearing temperature is via a measuring device that contacts the bearing’s outer race. However, there are other, less invasive options, too. One alternative is to use an
infrared gun to obtain a temperature reading from the outside of the bearing house.

4. Visual inspections. To detect visual symptoms of pump distress such as cracking, leaking or corrosion, conduct frequent visual inspections; they are an inexpensive way to help save your system from future failures.

PROCESS CONTROL
According to a study of 300 plant energy audits by Emerson Entech, the majority of basic control loops involving pumps (or a set of devices designed to manage the behavior of other devices in a system) actually increase process variability.
The primary reason is improper sizing of the pump, control valve and piping — namely, not selecting them in concert to ensure optimum performance — which typically makes tuning the control loop difficult. Automatic control constantly
degrades over time as a result of pump and valve mis-sizing issues; as a result, control loops often are switched into manual mode to stabilize the process.

Other studies show a high percentage of control loops actually operate in manual mode. A benchmarking report by Honeywell LoopScout of 115 separate facilities across all market segments revealed that, at the worst performers, up to 60% of control loops were ―bad actors,‖ with many of those operating in manual mode.

Once you’ve picked a pump to optimize, you can consider a range of mechanical and digital options to help regulate your pumping assets.

Mechanical and control modification systems. As Table 1 indicates, using a speed control to help vary speed linearly with an accompanying increase or decrease in horsepower consumption can provide sizable energy savings. 

Even a small speed reduction could lead to a 30% drop in power consumption. Alternatively, impeller trims (altering the impeller diameter) can change horsepower consumption at a squared rate —offering significant power decreases but not ones as large as from speed changes.

Another mechanical option is installing a parallel system to cope with fluctuation in flow or demand rates. By installing two similar pump systems with parallel piping to handle variable flow rates, plant operators can deal with rates that one pump can’t support alone. Although this may seem like an obvious solution, if the load increases more than the pump was designed to handle, the original pump may be running inefficiently from the beginning.

Electronic control systems. Digital technologies, such as electronic inverters, electronic-only variable frequency drives
(VFDs) and variable speed drives (VSDs) that include mechanical devices in addition to electronics, can alter the speed of the pump motor to help improve efficiency.

A VFD is an electrical system that controls motor speed by varying the frequency supplied to the motor. The drive also regulates the output voltage in proportion to the output frequency to provide a relatively constant ratio of voltage
to frequency (V/Hz), as required by the characteristics of the AC motor to produce torque. In closed-loop control, a change in power and frequency supplied to the motor alters its speed, thus compensating for a change in process demand. This
means greater process control and system efficiency, with even more intelligence integration.

Modern VFDs are the most efficient method to change pump speed, with up to 98% electronic efficiency. The simplest of these is the soft starter, a solid-state motor starter that’s used to start or stop a motor by reducing the voltage to each of
its phases, gradually increasing the voltage at a fixed frequency until the motor gets up to full voltage/speed. Motors, especially low-voltage ones, have a high initial current (amp draw) when first turned on; this can cause voltage
fluctuations and affect the performance of other circuits. Voltage spikes also can damage motor windings. To counteract this issue, you can add components in series to control current in-rush upon startup. In addition, it’s crucial for electronic
systems to reside in a climate-controlled environment, which is becoming more common as plants integrate digital systems.

More-advanced VFDs or VSDs utilizing frequency inverters can vary the speed of the pump to match the process flow demand. VFDs offer tremendous benefits, including pump size reductions, lower energy costs and improved efficiency. The U.S. Department of Energy estimates that up to 25% of installed motor systems can benefit from retrofitting VSD technology.

Despite the known benefits of the technology, initially VFD adoption was relatively slow, primarily due to perceived complexity, reliability and electrical issues. However, today’s more mature VFD technology and cable installation practices largely have mitigated these concerns. As a result, VFD implementation on pump systems is on the rise.

CASE IN POINT

When evaluating inefficiencies in a pumping system, it’s important to look for tell-tale symptoms of excess energy moving through various subsystems. Often, inefficiency results from a combination of issues that negatively affect equipment
integrity and surrounding infrastructure.

A vat dilution pump in a chemical process had a 1,180-rpm, 250-hp (187-kW) medium-voltage motor driving a double suction pump. The pump had a 14-in. (35.5-cm) discharge line that branches into three separate lines, each feeding200°F (93°C) filtrate to separate end-user systems. Each of the 10-in. (25.4-cm) branches had its own 8-in. (20.3-cm) control valves that usually were operating in the range of 20% to 40% open. The gaskets between the pump discharge flange and pipe frequently failed. Looking downstream and up to the top of the chemical towers, the pipes on each branch were rattling, leading to an inordinate number of cracks. Such pipe cracks can cause chemical losses in the sewers, environmental incidents and unplanned downtime. All told, the over-sized pump system averaged one day of downtime per month to repair some component or multiple components. These 12 additional days of unplanned downtime cut into production goals, increased costs and reduced profits. In this case, the financial impact exceeded $1 million annually. Added to that, the company suffered negative publicity both locally and nationally.

The primary solution here was implementing VFDs for constant discharge pressure control. The pump system normally consumed around 200hp (149kW), with the end-user valves highly throttled (20%–40% open) and the vibration levels about 0.6 in.(1.5 cm) per second. After VFD implementation, the pump consumes 75 horsepower (56 kW) during normal operation. In effect, the excess 125 horsepower (93 kW), not required to move the fluid, was directly damaging the pump and reducing its reliability.

IMPROVE SYSTEM EFFICIENCY

Using LCC to assess pump systems can lead to substantial performance gains. The amount of excess energy, once identified, will serve as the first step in quantifying the value needed for project justification. Then, predict reliability improvements and use past work orders and computerized-maintenance-management-system repair records to estimate annual maintenance costs avoided. Also, evaluate whether better process control can reduce the costs incurred by material variability. Estimate lifecycle savings based on current costs versus optimized ones. The plant of the future will make calculated decisions based on measurable, long-term operating costs and through identifying potential energy drains.

If you want more information, contact us by phone or email. 

The Chocolate Situation – Case Study

“Life is like a box of chocolates. You never know what you’re gonna get”

Tom Hanks in Forrest Gump 

For one chocolate processor, they sometimes never knew what the chocolate situation was going to be in their plant. They only knew each sweet product brought its own unique challenges. One of our customers manufactures candy bars and protein bars. Common ingredients include melted white and dark chocolate, caramel, liquid sugar, peanut butter, syrup, and some custom flavorings. Each product presents unique demands in processing. For example, one process may require a very thick and abrasive dark chocolate, but then very thin and smooth white chocolate for another.

Due to these variations in product properties, choosing a transfer pump was a headache for the plant. The customer had 4 different brands of pumps in their lines. For each brand, they had 3-4 different sizes and models with different pumping capacities. Each one had a different design and different spare parts, resulting in a large number of spare parts on stock. And maintenance? Maintenance was performed line-specific since most of the pumps were not interchangeable. It was simply a daily headache for the production and maintenance teams.

M.G. Newell carefully studied the customer’s process requirements and specifications including temperature, flow rate, product abrasiveness and elastomer compatibility. We were able to standardize the customer’s transfer pumps down to one brand, one model and 3 sizes to handle their entire pump needs. By standardizing on the Waukesha Cherry-Burrell Universal 3 Series of positive displacement pumps, the number of spare items was greatly reduced since two of the 3 sizes share common spare parts.

Also, since the pumps share a common design, maintenance has improved and streamlined. Each technician can work on any process line and pumps can easily be replaced by a same size pump. They’ve also reduced their spend on spare parts by reducing the number of spares in inventory. Simply put, it’s one more way We Make It Work Better.

If you want more information, contact us by phone or email.