Tips for optimizing pump efficiencies by setting proper impeller clearances.

In the ubiquitous world of horizontal ANSI pumps…all share some common dimensions and a back pull-out feature but note there are also two distinctly different styles.

Both styles utilize an external feature to adjust the impeller clearance. This adjustment device helps the owner to set and later re-establish pump performance and efficiency by axially compensating for wear…all without disassembly of the pump.


Two Choices

On one style; the open/semi-open vane impeller, operating clearance is set to the casing/volute and on the other style, the reverse vane impeller it is the opposite…that is, the clearance is set to the seal chamber/stuffing box. For either style the purpose of the adjustment mechanism is twofold. First to set the initial clearance for the pump size and product temperature and then later when wear inevitably occurs… you can re-adjust the clearance to regain performance and efficiency.



 

Both impeller designs have their pros and cons. For example, the reverse vane impeller can be accurately set without the casing in the safe and controlled environment of a shop. The open impeller design normally offers a larger wear area that may translate to longer periods of reliable and less costly operation. The reverse vane impeller presents a consistent lower seal chamber pressure (note: check for vapor pressure issues). The open impeller handles stringy and fibrous solids better.

Please note that Summit Pump offers both styles. For more details on the advantages and disadvantages of either style please contact your Regional Sales Manager.

Regardless of which type of pump you choose; the initial impeller clearance must be set prior to commissioning the pump in the field. The actual clearance specification varies as a function of the pump size and the product temperature. See your Instruction and Operating Manual (IOM) or contact our engineering department for details.

Even if the purchase order specified the factory to set the impeller clearance at a certain dimension you should always recheck the clearance in the field to verify the setting is correct. Unless there was an unbroken chain of custody with the pump, you cannot be positive and besides, it is easy to check.


Why Do You Care if the Impeller is Set Incorrectly?

As clearance increases pump efficiency decreases. You are effectively reducing the impeller’s size when the clearance increases. Just 0.015 to 0.020 inches off the correct clearance can reduce the performance of a 10-inch impeller to perform like 9.5 inches.

 



 

The general “rule of thumb” is that the pump will lose about 1% of its capacity for each 0.001 inches of impeller clearance for the first 0.005 to 0.008 inches of added clearance over the initial setting. The issue gets markedly worse with increasing clearance.


Pump Tips

  • On average you can adjust the impeller for component wear three times before the pump should come apart for closer inspection and before the clearance has doubled.
  • When you adjust the impeller, you are also changing the setting on the mechanical seal. On the open impeller style, you will be reducing seal face pressure and on the reverse vane you will be increasing seal face pressure. Resetting the seal may also be required.
  • On the open impeller style, the axial thrust will increase each time the impeller is adjusted due to the impeller’s back pump out vanes moving farther from the seal chamber. The effect will increase the axial thrust and reduce bearing life.
  • Net Positive Suction Head Required (NPSHR) increases as clearances open.
  • Regardless of the wear location, the seal chamber/stuffing box or the casing/ volute, there is also some wear on the impeller. Post repair or new, we highly recommend that before the pump is commissioned to measure and record total axial travel of the rotating element. With this benchmark information you can measure total travel at later intervals and compare. You will not know exactly which component is wearing or by how much, but you will have an important metric data point to help in the maintenance decision process.


References for More Information





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This month, we review the reasoning for multiple pump alignments and why there may actually be more required than you think!


At the factory… the motor is positioned on the base plate and checked for proper alignment to the pump. As soon as the unit (base/motor/pump) is loaded on the truck the alignment integrity is lost. Later the unit is moved from the truck or warehouse/staging area to the foundation, consequently any semblance of an acceptable alignment tolerance is placed in jeopardy.

Industry best practices (experienced engineers, millwrights, and rotating equipment experts) will tell you that a pump requires a minimum of at least four (4) alignment checks prior to startup/commissioning. There may be an additional 4 or 5 checks to be conducted in the full commissioning process for a possible total of nine (9).

Align the Pump 9 Times

When I tell people that they need to conduct 9 alignment checks in the process of pump commissioning, I receive a wide range of interesting comments…please first let me explain my statement.

One… the first alignment
As mentioned above; prior to shipment the pump is positioned on the base and centered within its bolt tolerance. The motor is then placed on the base and a “rough alignment” is conducted to ensure that a precision alignment is possible and can be successfully conducted later in the field.

There can be exceptions to this example, and it depends on the type and size of driver. The initial factory alignment may only cover the side-to-side adjustments and not the aspects of the vertical or angular offsets, as those will be addressed in the field. No matter how precise the alignment conducted at the factory and how carefully the equipment is transported … the alignment will change in the process.

Second alignment check 
When the pump, motor and base are received at the site and initially set on the foundation the second alignment should be conducted to correct for changes in transit. It is critical that the second alignment be conducted prior to grouting or connecting the piping to the pump. Omitting this step is a common and expensive mistake.

Three… the third alignment
You may have thought you had the alignment completed before, but now that the base is grouted you will find that that the alignment has again moved out of specification.

The process of grouting the base will oftentimes warp or otherwise move the base and offset the alignment. During the grout curing process there is a large amount of heat and some expansion force involved that will potentially change the alignment.

Four… the fourth alignment
Now that the base is properly grouted and the driver is aligned to the pump, it is time to connect the piping to the pump. It is always better to “pipe away” from the pump and not from the system to the pump to avoid unwanted moments and forces. Done correctly, connecting the piping to the pump should not alter the alignment in any way. However, from my experience this is a common reason for the alignment to change out of specification and introduce unwanted stresses into the pump.

Alignment steps 5 thru 9 
Involve further preventative measures, double-checking and troubleshooting. If you are experiencing issues with alignment procedures and achieving acceptable results in the field, it could be from omitting key steps in the process.Still interested in correctly conducting alignments and commissioning procedures? Please review my articles on this subject for more information regarding the remaining steps by clicking the links below.

 

 

 

 

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Recently, we investigated numerous issues with mechanical seals failing in self-priming pumps on suction lift applications. In each instance the pump/system was not installed or operated properly. Root cause analysis suggested a misunderstanding of basic physics. We thought it would be beneficial to review a few fundamentals for pumps on suction lift installations.  


suction lift simply means the maximum level of the liquid to be pumped is physically below the centerline of the pump impeller. Most centrifugal pumps can operate with a suction lift if they are primed first. Primed means the suction line, pump casing and impeller are full of liquid and all of the air or non-condensable gases are removed.

 

A centrifugal pump cannot “suck” or ‘lift” the liquid into itself. Atmospheric pressure is the force pushing the liquid into the pump for open systems. From this information we can conclude; the maximum suction lift at sea level with a perfect pump, a perfect liquid and a frictionless leak free system can approach 34 feet (Atmospheric pressure at sea level is 14.7 psia X 2.31 ? 34).

 

NPSH Available

 

You should always calculate the NPSHA for any application, but this rule is especially true for suction lift applications. From the NPSHA calculation you can see the following effects that subtract from the max suction lift:
  • If you are at an elevation above sea level then the max suction lift is reduced accordingly because atmospheric pressure will decrease with elevation.
  • As the temperature of the liquid increases so will the vapor pressure. As vapor pressure increases the max suction lift decreases.
  • The higher the static lift the lower the NPSHA and corresponding max suction lift.
  • Friction loss in the system will reduce NPSHA and the max suction lift.

 

Compressor vs. Pump

During the priming process the displaced air has to go somewhere. Even a great centrifugal pump is a really poor compressor due to the difference in density between air and water (? 800). If there is a check valve on the pump discharge, a parallel pump in operation and or a residual vertical liquid column, the pump will not prime. The air has to be vented somewhere, usually back to the suction source.

Submergence

The critical submergence must also be calculated so the pump does not create vortices and pull air into the pump. Even a self-primer has limits for air entrainment.

 

Final Note

You can have sufficient NPSHA and not enough submergence …and you can also have adequate submergence and not enough NPSHA.

If you are ever in doubt regarding a pump application, please contact your Regional Sales Manager and/or our engineering group for assistance.

For more information see my related articles on the topic:
• Calculate NPSHa for a Suction Lift Condition 
• 10 Common Self Priming Pump Issues 
• Guidelines for Submergence & Air Entrainment

 

 

If time and money were no object, the pump OEM would be very happy to design a pump specifically for the customer’s unique operating point;
it happens, but not very often.


In essence, all single stage centrifugal pumps are designed for one operating point on the curve. This point is commonly referred to as the Best Efficiency Point (BEP). All other operating points are a degree of compromise with efficiency, cavitation, radial thrust, and recirculation issues. Ignoring these stressors will shorten the life of the bearings and mechanical seals, thereby making the pump less reliable and more costly to operate.

Of course, most end users don’t have just one operating point and normally they want to operate in a wide area that is commonly referred to as a safe or allowable operating region (AOR). Therefore, most pump applications will require operation away from the area of BEP.

 

Reliability Management Methods

Assuming the pump selection was the best compromise (choice) for the application there are methods to mitigate the potential for the consequential negative effects. All the methods come standard with the added cost of reduced efficiency, but that cost can often be an acceptable tradeoff for reliability and reduced maintenance costs.

Some common mitigation methods are as follows:

      • Variable Speed Drive or Variable Frequency Drive (VSD/ VFD)
      • Bypass loop (manual or auto-process controlled) if operating too far left on the curve
      • Throttling control (manual or auto) if running to the right of BEP
      • Operating a different number of pumps in either series or parallel
      • Using different size pumps in the same system to accommodate system outliers

There are also common methods to manage the symptoms versus the problem:

      • Balance the impeller to a stricter standard
      • Ensure a proper alignment is conducted
      • Ensure the shaft runout and the radial/axial allowable movements are within OEM tolerance
      • Establish and maintain operating clearances to specification
      • Reduce or eliminate pipe stress at the pump flanges
      • If possible, choose a pump with dual volute or a diffusor style casing
      • Upgrade the pump shaft to a more robust design to reduce deflection (Reduces the L over D ratio)

 

Another Possibility – Low Flow 

In cases where the pump is operating on the left side of the curve it may be feasible to replace the pump with a low flow version. Standard single stage centrifugal pumps are typically of an expanding volute design. Expanding volute designs have the benefit of being more efficient, but the downside is increased radial thrust if you operate the pump away from the design point.

Low flow pumps utilize a circular casing where the casing is concentric to the impeller. By utilizing this design the radial thrust component can be appreciably reduced by amounts, normally in the range of 65 to 85%. In many cases using a low flow pump will reduce the need and cost for the more robust shaft (lower L over D ratio) and bearing system.

These are just some of the more common methods to reduce stress on the pump. If you are faced with an application that seems to have a “no right fit pump solution” Summit Pump can offer assistance.

We are your Best Value by
“providing quality pumping
products in a timely manner,
at a fair market price.”

Last month we reviewed basic vacuum principles.
The reason was to better understand how to correctly measure the differential pressure across an operating pump.


Understanding your suction pressure and knowing how to read a vacuum is critical in identifying performance issues. In the field, instruments measure in units of PSI …whether gauge, absolute or vacuum. When diagnosing issues, PSI must be converted to head in order to calculate Total Dynamic Head (TDH).

 

Total Dynamic Head

Consider Total Dynamic Head as the amount of energy the pump converts from suction to discharge. This information is critical in identifying where the pump operates on the performance curve.

Suction Pressure

To illustrate reading vacuum or pressure on the suction side of the pump, we will examine both a flooded suction and a suction lift application. Each example will assume the same pump, the same liquid and the same operation speed. The differential pressure of the pump will be the same for each example.

Note: For simplicity, we will not convert pressure readings to head in these examples, but understand the conversion mentioned above must be done in order to calculate TDH. For a more in-depth explanation, see my full article on the topic.


Flooded Suction
In flooded suction, the liquid level is above the pump datum and has energy to provide to the pump. Meaning the pump does not need to convert this energy and will use this “given” energy elsewhere. In this case, a higher discharge pressure.

 


Suction Lift

In Suction Lift, the pump must generate a low enough pressure at the eye of the impeller to have the fluid pushed into the pump by atmospheric pressure. Energy is used to make this happen and results in less energy available for pressure at the discharge.

Notice the overall pressure readings are lower but the differential pressure (75 PSI) remains about the same in both flooded and suction lift applications (using the assumptions we made earlier).

 

Take-a-ways

Pressure gauges neglect velocity energy and read only one type of energy, which is pressure.Understanding your suction pressure and knowing how to read a vacuum is critical in calculating the pump’s TDH (Total Dynamic Head). Knowing the TDH can lead you to resolving several issues including operation cost, safety, pump life, inaccuracy or just nuisance issues.

 

 

We are your Best Value by
“providing quality pumping
products in a timely manner,
at a fair market price.”

 

The concept of vacuum mystifies some people when encountered on pump applications. Today, we hope to simplify the problem.

 

Pressure vs. Vacuum

Even in a vacuum there remains some pressure… it is simply a pressure at a magnitude below the surrounding atmospheric pressure. Vacuum does not necessarily mean the absence of all pressure; vacuum can be any pressure between 0 PSIA and 14.7 PSIA.

As a refresher…we offer the following points:

  • Vacuum or vacuum pressure measurements are characterized as either absolute or relative (gauge).
  • Absolute pressure is measured from zero, which means a 100% or a perfect vacuum.
  • Relative pressure measurements are in reference to the atmospheric pressure. So if you see the word gauge or vacuum in the description it is being measured relative to atmosphere.
  • Absolute pressure = gauge pressure + atmospheric pressure.
  • Absolute pressure can be zero, but it can never be negative.
  • Absolute pressure at sea level is usually given as 14.7 PSIA.
  • Atmospheric pressure changes with elevation referenced to sea level and changes with barometric pressure (weather). If you are using gauge pressure to measure pressure or vacuum, you need to state the atmospheric pressure at the time of the measurement.

 

Units, Scales and Terms 

In the pump world we often encounter two descriptive terms, “absolute” and/or “vacuum” assigned to the measurement scale. Further, the measurements may either be in units of inches of Mercury (in-Hg) or pounds per square inch (PSI) in absolute pressure (PSIA) or gauge pressure (PSIG).

 

 

perfect vacuum, if measured in absolute terms is zero (0 inches Hg) but is 29.92 in-Hg V (-29.92 in-Hg G) if the measured units are deemed relative (vacuum or gauge).

Due to the differences in these two measurement methods you need to ask the equipment owner if the parameter measurement scale is absolute or relative? The methods are 100% opposite of each other and if not properly understood can lead to some big mistakes.

 

Application

If we had a container at a theoretical perfect vacuum (that is, we have removed every molecule and its components from within the vessel) then we could state that vacuum condition as 0 (zero) pressure absolute or 0 PSIA.

However, if we were to measure our perfect vacuum in inches of Mercury Vacuum or inches Hg V the reading would be 29.92 inches Hg V not zero PSIA as in the first part of the example.

 

 

Need More?

Stay tuned for part two in next month’s 60 seconds with Summit Pump for more information. If at any point you are confused by a vacuum application in the field and not sure how to proceed, just give us a call.

 

 

 

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products in a timely manner,
at a fair market price.”

 

We get calls from the field concerning issues with pumps that are experiencing performance issues. Typically we perform a triage scenario; we first figure out if the pump is on a suction lift arrangement and make sure the pump is notattempting to defy the laws of physics. Once that question is satisfied we then walk through the Net Positive Suction Head Available (NPSHa) calculationswhere about 60% of the time we find that there is sufficient NPSHa. After the NPSHa exercise we ask about critical submergence (SC). A frequent reply to the submergence question is that no one knows what submergence really is or they never thought that it could be an issue if the NPSHa was sufficient.

Net Positive Suction Head (NPSHa) and Critical Submergence are two different things, and while they are connected by the liquid’s static height at suction, they are two independent factors requiring consideration for a successful suction system design.

Note: That you can have sufficient submergence and not have sufficient NPSHa.
Note: That you can have sufficient NPSHa and not have enough submergence.

 

What is Critical (Required) Submergence? 

Submergence is defined as the distance (D) measured vertically from the surface of the liquid to the centerline of the inlet suction pipe. A more important term is the required submergence, also known as minimum or critical submergence (SC). Required submergence is the vertical distance—from the fluid surface to the pump inlet—required to prevent fluid vortexing and fluid rotation (swirling and or pre-swirl).

What happens if I don’t have enough submergence? 

Without proper submergence the pump will create a vortex that will introduce air to the impeller suction. Just 2% air entrainment will have a negative effect on the pump hydraulic performance because the air bubbles become trapped at the impeller eye blocking the fluid flow. At 4% to 6% the performance will drop significantly and at 12% the pump may bind. See my related Guidelines for Submergence & Air Entrainment article for more details.

 

 

How much submergence do I need?

There are many sources of information regarding this subject with accompanying submergence charts that you can refer to in pump reference books, ANSI/HI 9.8 and on web sources. Normally the guides will suggest that for every one (1) foot of liquid velocity on the suction entrance you will require one-half (0.5) of a foot of submergence. Recently revised empirical data from the Hydraulic Institute and my professional suggestion is that if you want to avoid pulling air into the pump altogether, then you should elect the more conservative approach of one (1) foot of submergence per one (1) foot of liquid velocity.

In the harsh realities of the real world you may not always have the luxury of the conservative one foot of submergence allowance per one foot of liquid velocity approach. If that is the case please contact us for the means and methods to work around the issue.

 

 

 

 

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MYTH: Factory Supplied Pumps are “Plug and Play”.

Busted

Pumps shipped from the factory are NOT ready
to be started when and as received in the field.


As an annual ritual I am compelled to remind pump industry people that 99.35% (approx.) of industrial centrifugal pumps do not arrive ready to run and play – unfortunately this “Plug and Play” pump industry myth continues to persist.

Overview

  1. There is NO OIL in the pump.
  2. The impeller may or may NOT be set to the proper clearance.
  3. The driver is NOT aligned to the pump.
  4. The direction of rotation on the motor has NOT been determined.
  5. The mechanical seal is NOT set.

If you already know these 5 things and fully understand the significance, then you can stop here. If you don’t know or would like a refresher please read on.

Oil
A pump shipped from the factory will NOT have oil in the bearing housing. Someone at the site must add oil prior to startup.

Oil is considered a hazardous substance in the commercial shipping world, consequently it is a violation of several federal laws to ship oil in the pump… Yes, there are means and methods to overcome this issue, but it requires special shipping, more money and paperwork. Additionally, OEM pump manufacturers are not in the business of stocking the multitude of different oils that a customer may request.


Impeller Clearance

A pump shipped from the factory may or may not have the proper axial clearance when it arrives on site. The factory adjusts the clearance at a nominal setting for the pump type and size based on ambient temperature water specifications.

The factory does not know the liquid’s temperature or other properties for the operating system. Note: it is also very possible the settings could have been adjusted after it left the factory. Confirming the clearance in the field is both easy and a professional best practice. Why take the chance? Also, prior to running the pump is the perfect time to take the initial total axial movement readings for the maintenance records.

Alignment
The driver will NOT be aligned precisely to a pump shipped from the factory. The factory utilizes laser manufactured templates for layout and performs a series of nominal checks to ascertain that the motor can be precisely aligned to the pump. Even if the factory did align the driver to the pump in accordance with the highest standards… as soon as the skid is picked up/transported the precision alignment will morph to unacceptable levels.

To learn more about about pump alignment, please check with your regional sales manager or refer to my articles on this subject:

Does Your Pump Have an Alignment Problem?
19 Tips and Common Alignment Mistakes


Driver Direction of Rotation

A pump shipped from the factory will NOT have the coupling spacer installed because you must first complete the driver rotational check with the coupling (spacer) removed. Additionally, with the coupling removed the process to set the impeller and mechanical seal is simplified.

The factory has a 50/50 chance of guessing the correct electrical phase rotation at your local site. If the rotation is wrong, the pump quickly converts to an expensive pile of useless scrap metal shortly after startup.

Mechanical Seal Setting
Factory installed mechanical seals will NOT be set. The pump comes with the seal clips in place (sleep position) to ostensibly preclude damage to the seal during shipping and handling. Plus prior to setting the seal the impeller clearance will need to be checked/set and the alignment completed.

Summary

• Read the instructions
• Add the oil
• Set the impeller clearance
• Complete the alignment and rotational checks … then set the seal
• Install the coupling spacer and the OHSA guard
Need some assurance when commissioning your pump? Give your RSM a call and/or perhaps review this article on the subject:

The Basics of Pump Startup

Finally
A warning tag is attached to each pump to communicate these 5 key steps to the end user/installer. Of course these steps have always been stated in the Instruction and Operations Manual (IOM). The IOM is included with every pump and if misplaced can also be downloaded from our website.

 

 

 

 

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We are your Best Value by
“providing quality pumping
products in a timely manner,
at a fair market price.”

Thanksgiving…At this time of year in America we purposefully pause and offer thanks for all we have. Suppose for a minute that in a fictional and make-believe universe you were a pump; what would you give thanks for? We share some ideas. 

This Pump is Grateful For… 

 

  • A balanced impeller, precise shaft alignment, robust foundation and solidly grouted baseplate so that vibrations and stresses can be properly transmitted to the earth. I operate smoothly with my oil level “level”.
  • Properly set clearances, so I can be efficient and stay on the published performance curve. The Efficiency Police and the Electric Bill will also send a separate Thank You card.
  • The proper diameter suction piping and the unobstructed 5 to 10 diameter length rule, so that I am not getting pelted with high velocity fluid. Suction flow is balanced, laminar and equally loaded to my impeller.
  • Controlled rate of temperature change to reduce thermal shock and related issues with different rates of expansion and contraction with my parts. We’re not getting any younger you know!
  • Proper materials/metallurgy so the acids and corrosives don’t eat away at my casing and impeller.
  • The correct operating speed so that the suspended solids don’t erode my parts 8 times faster  than normal.
  • Operating in the allowable operating range near the best efficiency point so that my arch enemy Radial Thrust and his evil twin step brother Shaft Deflection do not upset my performance and reliability. The mechanical seal and the bearings texted and stated they are also grateful.
  • The absence of pipe strain so that my bearing centerlines are congruent and the bearing geometry remains in the original round shape in lieu of eccentric. My brother, the coupling, also gives thanks.
  • Adequate NPSHA so there is no cavitation damage to the impeller and mechanical shock to the bearings and seals. Thanks for reducing air entrainment in the pumped liquid so my impeller eye doesn’t get blocked and blinded by air bubbles.
  • Our neighbor the electric induction motor also sends thanks for remembering to compensate for the liquid’s Specific Gravity in the horsepower calculation. She states that it makes her life much less stressful. Do make a mental note that her two tenants, Volts and Amps are still resisting to pay the power invoice, in case you run into them over at Ohm’s Law office.

Now for some ‘PUMP KIN’ pie!

Happy Thanksgiving,

 

 

 

 

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We are your Best Value by
“providing quality pumping
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Established in 1982, Summit Pump began as a pump parts supplier in Green Bay, WI. Under Bob’s visionary leadership Summit Pump evolved into a complete multi-line OEM pump manufacturer and trusted parts supplier for the industry worldwide. Bob reminds us the company mission statement is more than just a plaque on the wall; it is how we strategically go to market. We will “provide quality pumping products in a timely manner, at a fair market price”.

Today Bob continues to be involved in Summit Pump’s daily operations. When not at the factory, Bob enjoys going to the cottage and working in the woods, as he did in his youth. Having grown up in that area, Bob continues to share camaraderie with many high school friends.

Summit Pump appreciates the foundation Bob Keller laid for our company and the lessons he has taught us all. Please join in celebrating Bob’s 80th  birthday on Thursday November 12th by sending your greetings here.

 

 

How fast was I going officer?


Speed is a critical limit for any pump, but even more so for Positive Displacement (PD) pumps.  The maximum allowable speed of a PD pump is determined by several factors including the viscosity and temperature of the pumpage. Other important factors are the level of abrasives in the product, acceleration head, and the Net Positive Suction Head Required (NPSHR).

Commercially available and cost effective electric induction motors nominally operate at speeds well above the optimum PD pump speeds, consequently some method must be used to reduce the drive output speed. Direct drive is just not all that common in most Internal Gear Pump (IGP) and Progressive Cavity (PC) applications for this reason.

The boundary for PD pump speed will typically be managed with either a gear reducer or a Variable Frequency Drive (VFD) and/or a combination of the two. For even more precise flow modifications a servo motor can be used in conjunction with both a gear reducer and a VFD.
Speed Kills

As the product temperature and/or abrasive concentrations increase, the pump should be operated at even slower speeds to reduce the inevitable wear and increase reliability. This may also mean a bigger and slower pump is required. Pump wear is exponentially proportional to speed. Even for relatively small increases in speed the wear rate can increase by a factor of eight.

 

 

Prior to purchase, the allowable speed range for the pump should be reviewed so that the correct choice of materials and speed control are made to achieve the lowest Total Cost of Ownership (TCO) and Mean Time between Failures and Repairs (MTBF/R).

 

Controlling Speed

Gear reducers (aka “gear sets” or “gear boxes”) are both essential and common components in the drive train of many PD pumps. Unfortunately the fixed output of a gear box will lock the end user into one operating speed. Therefore, the pump’s hydraulic duty point (at some speed) and the maximum allowable speed must both be considered when making the selection.

One additional benefit of a gear reducer is the increase in the amount of torque delivered to the pump shaft.  Gear sets are frequently referred to as “torque multipliers” for this reason. Adding a gear set may potentially reduce the required motor size when compared to direct drive.

VFDs are often used in applications where speed dependent flow requirements will/can vary over a range. A VFD in conjunction with a gear reducer will allow the pump to operate across an acceptable range of speeds, while simultaneously providing the required proportional flow rate.

Note: Pump speed limits must be applied when initially programming the VFD.  The VFD operational parameters must be set within the pump’s speed limits to avoid the critical and common over speed mistake. 


Don’t get Pulled Over by the Pump Police for Speeding: 
Operating correctly saves time and money.

Teaching owners and end users about pump boundaries allows them to choose smart solutions for their application and ensure the equipment is effective, efficient and reliable… reducing the TCO and MTBF/R.If you have any questions please contact your Regional Manager or Engineering in Green Bay.

 

 

 

 

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“providing quality pumping
products in a timely manner,
at a fair market price.”

 


I recently received a phone call and subsequent email stating “my self-priming pump is not priming”. Both the phone call and the email were detailed with pictures and appropriate information to start the troubleshooting process.

The pump was a model 2796 MTO 6 X 6 – 13 with a 10.625” diameter impeller turning at 1750 RPM. The design point was 1000 GPM at 85 feet of head and the liquid was pond water at ambient temperature. The 6-inch suction piping was approximately 60 feet long and extended down to the pond with a check valve located only 30 feet from the pump. We did not know the depth or submergence of the suction piping into the pond. The suction “lift” was 23 feet. The issues with this application are at the end of the article.

 

 

In pump school we review self-priming “do’s and don’ts” and have developed
a check list of items to review if you are having a problem:

    • Even a self-priming pump must be primed initially.
      Fill the priming chamber with liquid.
    • Is the required lift is too high?
      No more than 25 feet: lower depending on temperature and altitude.
    • Pump distance from the liquid source.
      25 to 30 feet maximum.
    • Is there a leak in the suction line?
      It will pull air in; you will not see the leak.
    • Air vent.
      The air in the suction side of the system being displaced by the liquid must have somewhere to go, otherwise the pump will air bind.
    • Pipe size and geometry.
      The suction piping should be the same size as the pump suction because of the air volume that needs to be evacuated. The suction pipe should rise continuously to the pump and not create any high points that will trap air.
    • Submergence.
      The sump or source you are drawing from will likely have operating levels that are constantly changing. If you reach minimum submergence, it will be possible for air to be drawn into the pump and affect performance.
    • NPSHA.
      Calculating the NPSHA for self-primers, is a great method to identify potential problem areas. Remember, everything except atmospheric pressure is working against you (Static Lift, Vapor Pressure and Friction).

 

And Now for the Rest of the Story –
The Issues with the Application

A wise man once told me you can not violate the rules of physics
and 95% of pump problems are on the suction side of the pump.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Issue #1 – NPSHA is ? 6.5 feet. NPSHR at BEP is 14.6 feet. NPSHA must always be more than NPSHR with as much margin as possible.

Issue #2 – Suction pipe is ? 60 feet. Too much air to evacuate.

Issue #3 – Submergence Unknown. Minimum submergence required is ? 8 feet (without a bell mouth setup).

Issue #4 – Check / Foot Valve located 30 feet from the pond. If you are going to use a foot valve it should be located at the bottom end of the suction pipe.

As a general guideline, if your pump takes more than four minutes to prime than you should shut the pump down and look for and correct the cause of the problem.

 

 

 

For More Information
Reference These Pump & Systems Articles
by Jim Elsey:

10 Common Self Priming Pump Issues
Guidelines for Submergence & Air Entrainment
Calculate NPSHa for a Suction Lift Condition

 

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Jim Elsey's Pumps and Systems Articles

 

 

We are your Best Value by
“providing quality pumping
products in a timely manner,
at a fair market price.”

Green Bay, WI USA | Summit Pump, Inc. –

 

Summit Pump has cancelled all pump schools for 2020. With so much uncertainty over the upcoming months we felt this to be the prudent decision.

The Summit Pump school experience is classroom based, plus a factory tour with 14 educational stops and a social aspect like no other school.

Course content consists of:

    • Centrifugal Pump “101 Plus” Fundamentals: Basic hydraulics and fluid dynamics.
    • Summit Pump products and marketing, features and benefits, and tips about competitors.
    • Meet key personnel from Summit Pump, Inc, and participate in the factory tour which includes ANSI pumps, self-primers, PC pumps, IGP, manufacturing and quality checks.
    • Evening “symposiums” to meet, mix with and learn from other Summit Pump distributors from around the world.

We want to make sure all portions of the pump school are available to the students.

This break in pump school sessions provide us time to evaluate and reinvent the Summit Pump School experience to be better than ever next year.
We look forward to seeing you then.

 


Yes! Yes, we do.

First, please pardon my paraphrasing of classic movie quotes. However, I think it is a great analogy when talking about gauges in pump systems. Depending on who you talk to … Some people think gauges are extremely important to the overall efficiency of the system, but others do not. As an OEM pump manufacturer we know that gauges can be almost as important as the pump itself for creating an efficient and reliable system.

As a daily life example; Most of us would not drive a car without the basic gauges for speed, fuel, temperature and oil pressure. So why would we risk a multi-million dollar production system with no way of knowing how and where the pump operates or have the ability to troubleshoot it.

The Hydraulic Institute publication, Optimizing Pumping Systems states, “A pump system with no means of measuring flow, pressure or power is an inefficient pumping system”. Unfortunately, in many cases gauges are not often specified for a pump project or supplied at the time of installation due to cost constraints. In many cases, an up-front investment of a few hundred or even a few thousand dollars can save tens or perhaps hundreds of thousands of dollars down the road.

 

One of the best ways to monitor pump reliability is to install two pressure gauges. One on the suction side and the other on the discharge side. With the pump curve in hand and knowledge of the speed and impeller size, the gauges will tell you exactly where and how well the pump is performing. If the pump is not on the curve refer to this article for more information.

All of us in the pump industry should be familiar with reading pump curves and we know that pumps have specific areas of operation. These areas have descriptions like; Shut Off, RIGHT or LEFT side of the curve, Run Out and Best Efficiency Point (BEP). If the pump is “running left” on the curve, this simply means that the pump is delivering relatively higher pressure and lower flow. “Running to the right” means a higher flow rate, but a decrease in discharge pressure. BEP is the point of optimum flow and efficiency. The bottom line is that without gauges you will not know where the pump is operating. Oftentimes a gauge reading is a more accurate performance indicator than a flowmeter.

Here are a few scenarios on why using gauges is important in maintaining and troubleshooting a pump.

  1. Readings from both the discharge and suction gauges are a useful tool because the difference in pressures is proportional to the total head.
  2. The pump will operate where the system curve intersects it. Your estimate of where that point truly is may be off.
  3. A shutoff head test will provide useful information in relation to the pump’s health.
  4. Static readings are useful in detecting a leak in the suction or discharge.

One last note: I frequently see gauges installed directly on the pump flanges; while a common practice this is not always the best location. For gauges to provide an accurate reading the gauge taps should be installed close to the pump, but preferably at a minimum of 3 to 6 pipe diameters away from the flanges.

If you don’t measure it, you can’t manage it.

 

 

 

 

 

 

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We are your Best Value by
“providing quality pumping
products in a timely manner,
at a fair market price.”

Today we will discuss ANSI pumps with a focus on Summit’s model 2196 product line.  


Pump Impeller Clearance 

When a pump leaves our OEM factory there are a minimum of five critical steps required (to be completed in the field) as part of commissioning and starting up the pump. One of these five key steps is setting and or verifying the impeller clearance.When asked what dimension to set the clearance many individuals will throw out a nominal number like 0.015” and sometimes that is right, but many times it is wrong. And so, it is important to realize that the clearances are different for each size, type and model of pump along with the essential factor of product temperature.

Below is a chart from the 2196 manual as a reference:

Pump Efficiency or… What happens if the clearances are opened up further then the factory recommendations?

In general: Once impeller clearances reach 0.005”- 0.010” in excess of the factory design clearances the efficiency loss will be approximately one to one. That is, there is a one percent efficiency loss for each additional 0.001” of clearance.Once you exceed 0.010” beyond the factory advised clearances the rate changes and it then becomes a two  to one loss. That is, there is an additional two percent loss for each additional 0.001” of clearance.

Efficiency continues to decrease dramatically as clearances increase. Once clearances exceed 0.015 to 0.020 over the initial clearance, the rate of efficiency decrease can become exponential, first as a square function and then by the cube and so on. Somewhere in excess of 0.030” to 0.040” the pump loses most of its ability to pump effectively.

What should I do? 

Even if you set the clearances correctly at startup… over time, wear on both the casing and impeller will inevitably take place and so the pump will experience a loss of efficiency and performance. At which point, you’ll need to readjust the impeller clearance to compensate for the wear. As a general “thumb rule” once the clearance is doubled from the original settings, the pump clearances need to be reestablished to the original dimensions. Please talk with your RSM for more information on this topic.

Why should I maintain proper pump clearances? 

Setting proper impeller clearances on pump installations is a critical and crucial step.

Note that as clearance increases…

 

 

 

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We are your Best Value by
“providing quality pumping
products in a timely manner,
at a fair market price.”