I recently received an e-mail asking to explain what the terms “open” or “closed” referred to when discussing impellers in a slurry pump. So here it is.

Although there are numerous styles/designs offered by pump manufacturers, most slurry pump offerings boil down to a variation of one of two basic designs, with a third design, slightly less common, that is becoming more widely used every year.

Closed Impellers

The first, and arguably the most, rugged design is the closed impeller. In this design, the liquid follows a path down a tunnel formed on the sides by the vanes and is “closed” in on the top and bottom (or front and back depending on shaft orientation) by two shrouds. The two images below illustrate this design.

Semi Open Impeller

The semi open impeller is very similar in its design to the closed impeller. The one major difference is the absence of the front shroud. The vanes of a semi open impeller are supported by a back shroud only and the impeller is completely void of a front shroud. In the absence of a front impeller shroud, the front wear plate completes the tunnel used to accelerate the slurry within the pump.

Recessed Impellers

The third and slightly less common slurry impeller is the recessed impeller. Often called “torque flow” impellers, they create a centrifugal force in a unique manner.  Instead of accelerating liquid down the vanes, these impellers use the vanes to create a hydraulic coupling. The coupling then spins the slurry within the casing, thereby creating the centrifugal force required to create discharge pressure. 

With the vanes basically out of the normal flow path, erosion is minimized and the vanes do not need to be as thick as they have to with other impeller styles.  In fact, finer blades increase efficiency and are therefore often deemed more desirable.

The picture below is a good representation of the impeller, and the section view beside it illustrates the impeller location within the pump.

I hope these short descriptions help clarify the terms “closed”, “open” and “recessed”.  Next month we will look into the advantages and common application of each of these designs.


Whether it be a submersible pump you already own or a used pump you are looking to buy, it is important to know the condition of the electric motor. A few quick checks can save you a bunch of time and or money.

The most common problem in a submersible pump motor is water ingress. Whether it be entry though damage to the electrical cable, motor housing or seal system the results are the same. Water and electricity don’t mix well and most often end in what is referred to as a phase to ground fault. When this happens electricity normally contained within the motor windings “leaks” through damaged electrical insulation within the pumps motor and reaches the motor case/ ground circuit.

Fortunately for pump users the slow ingress of water does not immediately result in a catastrophic failure but does cause the winding insulation to weaken, which in time eventually does result in a major motor failure.

If a phase to ground leak has resulted in a catastrophic failure there will be little to no electrical resistance between the power conductor and the pump ground circuit. This is a clear indicator that the insulation at one or more points has completely failed. This type of failure can often be detected with an inexpensive multimeter or ohmmeter. A reading of zero ohms (or close to it) on the lowest setting clearly indicates a major problem. (see below)

If the insulation is only weakened but basically still intact, the applied voltage from a multimeter is not sufficient to detect a problem. To detect this condition a much higher voltage must be applied. Insulation resistance testers generate much higher voltages, up to 1000VDC or more. These instruments are often referred to by the brand name ‘Megger’, but are available from many different test equipment manufacturers.

Higher test voltages can generate leakage currents large enough to yield much more accurate results than a multimeter. Found early, motors with low readings can often be disassembled, dried out, and re-dipped to add extra insulation. This is far more cost effective than a full rewind. Below is a picture of a modern Insulation resistance tester and beside it an older crank-powered one.

Insulation resistance testers often feature multiple ranges, such as 300V, 500V ,750V, or 1000 volts. To apply a test the general rule is to determine the motors normal operating voltage and choose the next higher scale. (eg, for a Megger offering the four voltages listed above, use the 750 volt scale for a 575 volt motor.) Ideally, you want a reading of a few gigaohms or more, but I’ve personally installed 575 volt motors with 750 megaohms resistance to ground and had no problems. This value will decrease as the motor ages.


When looking to test a submersible pump motor, first test the unit with the electrical cable still connected at the pump end but completely disconnected from the power supply. If a fault or weakness is found, separate the supply cable from the pump by opening the pump and disconnecting the motor winding leads from the cable conductors. Check the motor and the cable conductors separately, you may be lucky and have a good motor and only have to re and re the cable.

Just to be clear, the phase to ground test described in this blog will identify 90% of the faulty or weak motors, but only a well equipped rewind shop can perform complete testing of a submersible motor.

Should you need hands on support with a motor problem, or for that matter any pump problem please give us a ring. We are here to help!!


I often receive questions as to whether a check valve in a pumping system is a good or a bad thing.  Auto closing check valves are often an integral part of a successful pumping system; however, they can also be the root of many system failures. The question then becomes “when is it appropriate to incorporate check valves in a piping system?” Answering this question is often different for systems handling clear liquid or non-settling slurries than it is for systems handling settling slurries, so let’s look at both.

Clear liquid or Non–Settling Slurries

Seven factors to consider when deciding if a check valve should be installed:

  1. If the piping system has a significant elevation change, then back-flow through the pump on system shut down can spin the pump backwards damaging the pump or the pump driver.

  2. If a pump is operating in parallel with other pumps and there is no check valve present, a reverse flow could be induced  when a single pump is shut down or fails. The reverse flow may spin this pump backwards and damage it or the pump driver.  In addition, flow diverted backward through the idle pump would further reduce the production within the overall system.

  3. If the system incorporates a long pipeline, the significant friction component within the system head will be absent on an empty pipe start up. This will cause the pump to operate at run-out conditions as the pipeline is filled. A check valve can limit this problem to the initial charging of the line and thereby reduce possible damage due to cavitation.  It can also similarly reduce issues with the pump driver, if the driver was not sized to handle the high-power draw that run-out conditions create.

  4. Centrifugal pumps have to establish flow through the pump to develop discharge pressure.  Pumps operating against a high static closing pressure on the check valve may not be able to move enough liquid through the impeller to open the check valve and establish flow. This circumstance would necessitate the use of a relief valve between the pump and the check valve and for the relief valve to be temporarily opened every time the pump is started. This of course adds another layer of complexity and cost to the overall system.

  5. Obtaining a check valve with a pressure rating suitable for ultra high lift series systems may be difficult.  For example: a deep open pit mine may have over 1000 ft of back-pressure on the primary pump’s check valve if the check valve at a later lift station fails.

  6. In locations that are subject to freezing weather conditions, dump valves must be installed to drain the line after a shut down when check valves are present. These need to be automated or stringent procedures in order for 24-hour monitoring to be in place.

  7. Auto check valves that allow some degree of back-flow before totally closing can be the source of catastrophic water hammer.

Settling Slurries

The factors to consider for settling slurries are the same as the ones listed above, but the issue of solids settling in the line and the possibility of a plug forming can add further complications.  If check valves are employed, procedures for line flushing must be in place. In addition, dump valves are strongly recommended so lines can be drained of solids should an unscheduled shut down suddenly occur.

My Advice

With so many factors to consider there is no hard and fast rule as to whether a check valve will help or hinder operations. My advice is to:

  1. Look at your system without check valves and decide if any of the factors listed above are a major concern.

  2. If there are concerns, look at installing check valves and make up a list of automation and or procedures that would be practical and needed to address those factors.

  3.  The final step then becomes a cost / risk analysis as to whether the automation and or procedures will appropriately address the concerning factors.

 I trust that this blog will help some of you decide if and how automatic check valves should be installed.  For those readers who were looking for me to simply say “yes or no to check valves”, I apologize!!


Are your slurry pumps in good condition?

I travel to customer sites on a weekly basis and I see a full range of good and bad when it comes to pump maintenance.

I decided to write a blog on the most common preventive maintenance tips concerning the Hevvy/Toyo line of pumps so it’s available even when I’m not.

This list is based off the most common errors that I see on a consistent basis.

How to ENSURE proper maintenance of your slurry pumps? (In only 6 steps)

Step #1: Check the belts

When should you check the belt tension of the slurry pumps?

If your slurry pumps are belt driven please check the tension once quarterly at a minimum. Belts that are too tight will cause damage to the light series motor bearing and once that bearing fails then the thrust bearing will start to fail in the pump. Belts ran too loose will cause poor performance and slippage causing damage to the sheaves.

How to tell if the belts are loose on slurry pumps?

I like to use a Gates tension tester. It is a simple tool and comes with instructions. An experienced ear can tell if the belts are too loose. They will be making a flapping sound. Belts that are too tight could cause the motor to be pulling high amps or bearing temperatures to increase before you start to notice bearing failure. We also recommend that you refer to TB Woods website and manuals for proper troubleshooting and maintenance on belt drives.

Step #2: Check the oil

When should you change the oil of your pump?

If your pump is on oil lubrication please check periodically to make sure no water or product is present in the oil. If your sealing device is ok, changing the oil on a regular interval will increase the lifetime of any pump.

Water is bad for your slurry pump: How to know if there is water in the oil?

Water is bad as it will cause bearing and/or motor failure. Seals do leak by nature and a small amount of water is ok. A significant amount of water in the oil will cause the oil to be milky.

Some key features may be already incorporated into your pump’s design to help identify water in your oil. One such feature is the moisture sensor which will trip when there is excessive amounts of water in the oil. Water in the oil is an early indicator that sealing has been compromised.

The first place to check is the sealing device used on your particular pump. If you feel you are getting false alarms on the moisture sensor try adjusting the sensitivity setting.

Another thing to check is the setting distance from the end of the probe from the housing. If you’re unsure about this please contact our engineering team or myself for proper setting on the Hevvy/Toyo line.

Step #3: Check your impeller clearance

Best performance is achieved by checking your impeller clearance on occasion. Consult your manual for proper clearance. When checking clearance look for excessive wear in the impeller and other wetted parts.

Wear in the wetted parts can cause the clearance to increase causing a loss in performance.

Wear can be caused by the abrasiveness of the product being pumped or by running the pump off the designed curve for the pump.

Step #4: How to review slurry pump requirements

Is the slurry pump still being asked to do what it was built to do?

Sometimes systems and processes change but we continue to ask the same of our equipment without taking into consideration the changes to the process that may have been made throughout the years.

For trouble shooting it is a good idea to install a pressure gauge and flow meter on the discharge line of the pump. You can take the pressure reading and multiply it by 2.31 to give you a rough TDH. You can then take the TDH and a flow reading and see if your pump is running near BEP on the pump curve. If not, please contact the OEM.

Step #5: Monitor your pumps temperature

Temperature sensors are provided with our submersible pumps for protection of the motor. Each manual provided with the pump will outline how to hook up and monitor the temperature sensors for maximum lifetime.

Why should you care?

If the motor gets too hot the sensors will trip and the pump will shut down until the motor cools. If the sensors are not connected you are running the risk of burning up your motor.

If you ask for a warranty claim and these devices are not connected then your warranty is void.

When should you check your slurry pump temperature?

Our horizontal and cantilever pumps need to have the temperature of the bearings checked weekly while the pump is in operation. Using a temperature gun check the bearing housing temp in the closest proximity to the bearing.

What temperature should the slurry pump be?

While most pump bearings run in the 140 to 170 F range I suggest never allowing temperatures to exceed 200 degrees F maximum. Bearing temperatures can be a sign of too much lubrication or beginning stages of bearing failure.

Step #6: Monitor the pump bearings

Using some form of vibration equipment. This will give you an indication if bearings start to fail.

Vibration analysis should be performed by a qualified and trained engineer/ technician experienced with this type of work.

Proper vibration monitoring will give the user a lot of useful information which can increase the MTBF and improve performance of the pump. Refer to HI vibration guidelines on vertical, horizontal, and submersible pumps for proper limits. Consult Hevvy/Toyo engineering for more information.

Learn about other pumps:

Click the links to go back to learning about slurry pumps USA services or slurry pumps Canada services.  Talk to Hevvy Pumps for more information.



According to our electrical team, heat is the number one cause of motor failure. It simply kills them. Temperatures near or above the insulation rating of your motor will cause your motor’s insulation to deteriorate faster, ultimately resulting in premature motor failure.

Defining the starting limit for your pump’s electric motors

 Our team is often asked one important question: How often can I start my pump?

The answer will change depending on the size and starting method of the pump (which we will touch on below), but to avoid damage to your pump’s electric motor, it is always best to verify the starting limit with your vendor.

Motor starting limits are usually specified in two ways: number of starts per hour (typically used for lower HP motors) or minimum time frame for one cold and two hot starts (typically used for larger HP motors). These ratings are based on starting a motor across the line, which is when a typical induction motor may see inrush currents of 6-8 times its FLA, generating large amounts of heat in the motor windings. The allowable start number reflects how long it takes for your induction motor to cool off. Larger motors will take longer to cool, meaning that they can safely start less frequently than smaller motors.

H class insulation and heat

Some may think that having a pump with H-class insulation means that the insulation can’t be damaged. In reality, it only means that your motor has a little more headroom on the amount of heat it can safely tolerate. While this will help increase the number of allowable starts, the higher temperature allowance of H Class (180°C) insulation over standard F Class (155°C) insulation is far outweighed by how slowly most motors (especially submersible motors) can dissipate excess heat. Any benefit from higher insulation temperatures comes from the specified allowable number of starts.

Submersible pumps with a cooling jacket

There is also a belief that submersible pumps with a cooling jacket can be started more often. Unfortunately, the answer to this is usually still no. Once again, it comes back to how fast your motor can dissipate its excess heat. For heat to leave the motor windings, where most heat is generated, it has a long way to travel. It must pass through the winding insulation, the steel laminations in the stator, and the motor housing before being removed by a cooling jacket. While this may not sound like a lot, means that some larger motors can take hours to cool. Providing a cooling liquid to the motor housing does very little to increase the speed at which the excess heat disappears.

Solutions to mitigate motor damage from excessive motor starts

Change the starting method

As stated above, one way to increase the number of allowable starts involves starting a motor across the line (direct on line or DOL). Other options include soft starters and VFDs, which can drastically reduce the inrush current to an induction motor—sometimes to only 1.5 or 2 times FLA (as low as one quarter of across the line) if configured correctly. These are the best options for reducing the inrush current; they have the added benefit of reducing the required current from your power system to start your pump. Using a wye-delta starter or a reduced-voltage autotransformer starter can also reduce the inrush current to your motor by up to half that of an across the line start.

Change the number of starts

This can involve anything from increasing the volume of your sump, to simply adjusting the level of your pump up or pump down switches to eliminate backflow oscillations or maximize the range of your sump. Any change in the sump and piping system can reduce the number of starts that a pump experiences will help increase the life of your motor.

Learn about the industrial pumps that Hevvy Pumps has to offer your project:

Read the Slurry pump maintenance guide to learn how to maintain your slurry pump for optimal performance. View slurry pumps in USA options.

Talk to Hevvy Pumps for more information.

We hope this helped answer some of your questions! As noted at the beginning of this blog, best practice is to verify the starting limit of your pump with your vendor.


    Hevvy Support

Vibration issues with your slurry pump might be obvious: your slurry pump shakes like a wet dog, or subtle: you keep losing bearings or seals prematurely and don’t understand why. In either case, vibration can cause a number of problems with your pump that can lead to costly repairs, downtime, and shorter mean times between failure.

How to Confirm a Slurry Pump Vibration Problem

Removing vibration in your slurry pump.

The Hydraulic Institute publishes acceptable vibration limits for all vertical, horizontal and submersible slurry pumps. But how do you verify whether or not you are within these limits? A trained vibration engineer/technician can take readings using a vibration analyzer to determine exactly where the problem lies.

If everything seems to check out, then you can start looking at how the slurry pump is running. Sometimes the pump performs differently on-site than when it was purchased from the factory. For example, a slurry pump may have been sized to deliver a much higher design head. This can cause problems with vibration as well as premature failure of the wet end. To check the actual function of the piece of equipment in question, you can install a pressure gauge, or if one is already installed, take a pressure reading.

How can I calculate the TDH in slurry pumps? 

Using the following formula, the TDH can be easily calculated:

TDH = Hs + (Psig x 2.31/Slurry SG) + 0.00259*GPM²/D4  

A flow reading is also needed. If no flow meter is installed, a portable one can be used to obtain a fairly accurate reading. Once the TDH is calculated and a flow reading is available, check the curve shown in the manual to determine the performance of your slurry pump. The best efficiency point will already be marked on your curve.

Here is an example of a slurry pump performance and system head curve:

Pump performance and system head curves chart for a slurry pump.

6 Steps to Take When You Have a Slurry Pump Vibration Issue

slurry pumps vibration solution tips


  • Check the framework for loose bolts and/or cracked welds. A loose bolt or cracked weld can cause looseness and allow the pump to vibrate. Depending on the severity, this can lead to bearing failure.
  • Use some sort of listening device to detect irregular noise in the bearings. Most of the time if you are losing a bearing, you will hear a popping noise. If you are unsure of the noise you are hearing, go listen to a good bearing on another piece of rotating equipment so you can judge whether the noise you are hearing in the suspect bearing is abnormal.
  • Check for coupling or sheave misalignment. Always check that keys are 180 degrees apart as this can be a source of imbalance.
  • Open the wet end and check for blockage in the impeller vanes. Check for looseness of the impeller.
  • Check and make sure the sheaves are correct for the speed at which you are supposed to be operating. If direct drive and running on a VFD, check your setting to ensure you are not running in the critical speed range.
  • Check for airlocks. An airlock in the pump can cause a shut-off scenario, high vibration and ultimately pump failure.


Vibration as a Problem Indicator

Poor performing slurry pump due to vibrations and other issues.

Vibration checks should be a regular part of your preventative maintenance program. If checked for properly, vibration can be a leading indicator of a number of common pump ailments, including:

  • Bad bearings
  • Cavitation
  • Coupling or sheave misalignment
  • Impeller balance
  • Running the pump off the curve
  • Critical speeds
  • Improper frame support or improperly designed baseplate
  • Airlock
  • Bent shaft

Read the Slurry pumps maintenance guide to learn how to maintain your slurry pump for optimal performance. 

If you feel uncomfortable or have any issues with vibrations in your slurry pumps, don’t hesitate to contact us. As always, we will be happy to help in any way possible. We design and repair slurry pumps to keep your project working efficiently. Talk to Hevvy Pumps today for more information. 

Let’s get into priming your industrial pump

Did the POTUS really coin this phrase and what does it mean?

Today the President of the United States of America, Donald Trump, put the pump industry into the mainstream by claiming to have coined the phrase “priming the pump”.  In doing so he highlighted one of the basic principles of pumping and I thought this was great opportunity for us to talk about pump priming, its origins, its principles and why it’s so necessary.

Now of course when President Trump used the phrase “Priming the Pump” he is not actually referring to a piece of pumping equipment but moreso using it as an analogy for government spending or cutting taxes to stimulate the economy. The idea of using the term “Priming the pump” as an analogy for government stimulus is not a new idea. John Maynard Keynes the author of the New Deal has long been credited for first using the phrase. He is after all the father of idea that it is necessary for governments to spend money to stimulate the economy during recessionary times. That being said, there is no evidence of Keynes actually using the term “Priming the Pump”. The first occasion of “Priming the Pump” being used as an analogy for stimulating the economy was actually in a Wall Street Journal article in 1933 and then again used by President Franklin D. Roosevelt in a 1937 speech, according to Merriam-Webster.

So now that we understand it’s origins in popular culture, let’s now look at the technical necessities of priming a pump. Just as today the phrase has come to mean intervention in terms of stimulus to prepare a weak economy to build strength and momentum and ultimately move on its own, the origins of the analogy are quite appropriate.  Let’s find out why.

First a history lesson! In the late 17th century Denis Papin built a straight vaned centrifugal pump and is credited as the father/inventor of the centrifugal pump.

Denis Papin born 22 August 1647

As the name implies, a centrifugal pump relies on centrifugal force to create a pumping action. Denis’s creation, and for that matter all centrifugal pumps, use a rotating impeller to accelerate a liquid down the length of the vane and create a pressure. The pump action relies upon the departing liquid to exit, creating a low pressure zone behind it.   As the pressure at the impeller eye drops, external pressure fills the low pressure zone with new liquid and the fluid cycle continues.

When a pump’s impeller is void of liquid, that is to say full of air, there is problem!! With out a fluid of some mass within the vanes, the pump cannot create a useful low pressure zone. With out a low pressure zone the fluid may not enter the pump and provide the mass to create the low pressure.  A classic example of the chicken and egg story!!

To start the cycle and create a pumping action we must  first supply the impeller with a liquid. This is commonly referred to as priming the pump.

How a pump is primed is a function of the pump style and the installed application.  There are many ways of establishing a prime but most pumps require that the impeller and casing  be filled with liquid from an outside source, usually before the pump is started.

Many pumps are installed in applications that provide a flooded suction, the simplest solution to the priming issue. The pump is installed at an elevation lower than the liquid source so that gravity will cause the pump to naturally fill.  

For submersibles,  priming is typically accomplished by lowering the pump into the liquid and allowing the air to be displaced by the liquid.

Caution; submersing just the impeller and casing may allow the pump to prime but in the case of electric submersibles, operating the pump without submersing a large portion of the motor may result in motor cooling issues.

Learn about the industrial pumps that Hevvy Pumps has to offer your project:

Read the Slurry pump maintenance guide to learn how to maintain your slurry pump for optimal performance. View slurry pumps in USA options.

Talk to Hevvy Pumps for more information.

There are numerous other methods of establishing a prime, some of which we will cover in future blogs. Until then stay primed!

Until Next Time,

RJ (The Fact Checker!)

Gain In-Depth Knowledge About Our Pumps & Industry

The pumping of water packed with coke fines produced by the jet cutting process in a Delayed Coker Unit (DCU) is an aggressive application. Pumps commonly fail or have reduced operating lives for a variety of reasons including: heavy fines loading, challenging suction conditions, high temperatures, and deep set sumps all combine to create a harsh environment that constantly takes pumps out of operation and puts them into the repair shop.

What the application requires is a pump that can withstand all of the following challenges

  • Inadequate lineshaft bearing lubrication due to high temperatures and solids ingress.
  • The collapse of accumulated solids which can bury the pump’s wet end and choke the suction with solids.
  • Seal and lower bearing failures resulting from the cavitation that is created by the higher temperatures and ensuing low NPSHa, as well as from the restricted sunction that results from solids accumulation.
  • Seal and lower bearing failures resulting from clogging with fines, as well as the reverse flow and potential reverse rotation that can occur upon shutdown due to faulty check valves.
  • Overheating of submersible motors.

Hevvy-Toyo’s new HNS submersible pumps model addresses and solves each of these concerns.

Inherently, our HNS submersible eliminates the Lineshaft bearings which are a prime source of failure in vertical pumps. The removal of these bearings means that there is no need to worry about improper lubrication, solids ingress on the lower bearing, or shaft binding caused by the temperature differences between the bearing column and discharge pipe. Lineshaft bearings are negated altogether!

Our patented Plenum 54™ system combined with our proprietary XD seal are designed specifically to function in environments with high solids and fines concentrations, abusive suction conditions where cavitation is common, and where the pump and rotating assembly can see heavy loading due to high solids and/or extreme operating fluctuations.

To further provide solutions to these application issues, the Hevvy HNS is supplied with our patented agitator and jet ring. These key items work to keep the zone underneath and around the pump’s suction clear of solids, while also fluidizing the solids in the event that a submerged “wall” of solids collapses onto the pump.  During the reinstallation of the pump, the powerful jet ring can also clear a path to the sump floor through the solids accumulated in its absence. The jet ring combined with the submersible configuration provides a powerful alternative to this challenge faced by vertical pumps. 

So how do you install a vertical pump into a sump that is effectively shallower than when the pump was removed?  With the HNS submersible and jet-ring, this challenge is eliminated.

At the heart of this system is the HNS motor and rotating assembly.  Designed with a robust L/D ratio < 1 (our patented “run-dry” technology) and built on a modular format, the HNS provides security in the toughest applications as well as flexibility for the future.   The modular concept allows for multiple benefits:

  • Spec your own service factor; 1.35, 1.5, 2.0, 3.0….?   Our wet-ends are interchangeable across a broad range of motor sizes, thus allowing you to customize the service factor.  Whether you want to “supercharge” your rotating assembly, or drive down internal loads and operating temps, the HNS’ modular design allows you to do so.
  • The HNS is interchangeable across all our wet end designs.  If operating conditions change, or you want to repurpose the pump into another application, the HNS design allows you to swap out the wet-end, or the motor to meet your new requirements.

The HNS can even be attached to a column and mounting plate in a pseudo VS4 configuration to retrofit existing problem pumps, while maintaining the current piping configuration.

Whether you require a submersible pump or vertical pump for your coke pit, Hevvy-Toyo has the knowledge and advanced solutions available to ensure long, trouble free operation.

Learn about the industrial pumps that Hevvy Pumps has to offer your project:

Read the Slurry pump maintenance guide to learn how to maintain your slurry pump for optimal performance. View HNS pumps options and distributor locations. 

Talk to Hevvy Pumps for more information.

Speak with one of our Coking experts to find out how we can help improve the reliability of your decoking sump pumps.