Hard metal pumps are at the heart of the slurry industry. Without them, transporting abrasive, slurry materials from one point to another within the system would be difficult if not impossible.
A hard metal pump is sometimes called a slurry pump since it handles slurries that could clog or wear out other kinds of pumps. It is made with a sturdy material that is specific for the kind of mixture that it will carry.
Solid particles in the slurry can be abrasive. Hence, the linings are often made with a metal or rubber that could withstand the knocks and scratches that the particles can create.
Specific designs withstand slurries with extreme temperature and pH levels, too. And since these solid-liquid mixtures could be thick and difficult to pump, this kind of equipment generally requires more power to operate. And therefore, it requires a higher operational cost than a standard water pump.
Determining what kind of hard metal pump you will use in your process will depend highly on the material that you will be moving.
But with all the options that you have, it could be confusing and choosing the wrong one could be a costly mistake. Let this article help you in understanding the basics of slurry pumps and in choosing the most suitable one for your process.
How does a hard metal pump work?
Many hard metal pumps are some form of Centrifugal pump. The inlet of the pump is at the center of a rotating impeller. As the mixture flows in between the blades of the impellers and reaches the edges using centrifugal force, pressure energy builds up in between the impeller and the casing. This, in turn, generates kinetic energy that will pump the mixture.
The mechanism is quite simple making this kind of equipment extremely productive and easy to maintain.
Also, understanding this mechanism can help you decide on which parts and features you need to look at closely when dealing with this kind of equipment.
The impeller must be sturdy, the casing must be easy to maintain, and the motor and rotating shaft must operate smoothly.
What are things to consider in selecting hard metal pumps?
Characterize the material
In designing your pumping system, not just in selecting which pump to use, you will need to consider several parameters such as:
Consider the flow
If the particles are small enough and tend to create a homogeneous mixture, then, the slurry may be considered non-Newtonian.
Knowing this will determine the behavior of the slurry when subjected to stress. Is the shear rate proportional to the shear stress you applied? Newtonian. Does it require a higher amount of force before it starts flowing? Non-Newtonian.
Determining the homogeneity of the mixture also helps you visualize how the mixture behaves inside the piping system. The settling solid particles will be in contact with the walls of the pipes and pump while the non-settling ones will flow steadily.
Even the velocity at which the particles travel along the pipeline will matter. If the velocity is too fast, it will lead to faster wear and tear of the pipe. Also, there will be more friction losses.
Meanwhile, if the velocity is too slow, the particles may settle which can lead to sedimentation and will still have friction losses.
With all these things to consider, choose a hard metal pump that has a wide working range of parameters and that is designed specifically for your system.
Determine the discharge requirements
The total discharge head is the sum of the static discharge head and the friction losses. If you have a target pressure, take note of that as well. Basically, you must know the height at which you want to discharge the mixture and the power requirement depends on this, too.
What are the industries that use hard metal pumps?
Here are some of the industries that employ this kind of pump:
This kind of equipment is versatile, and many industries use it in their processes. In these industries, you will find three types of this kind of pump.
Nagle Pumps, Inc., an industry leader for more than 50 years, provides all three kinds with features boasting a long service life and high capacity.
The design includes impellers with large passages to minimize wearing while maximizing the throughput. The bearings are also isolated and specially designed to be heavy-duty and leak-free.
Moreover, Nagle Pumps are easy to maintain which further extends its life. Some parts like the bearing cartridge and the stuffing boxes are easily removable for easy access and maintenance.
Another industry front-runner is the Finish Thompson DAP Series, ANSI Process Pump B73.1. It is one of the most versatile ones in the market.
The wide range of parameters and dimensions of this pump are designed such that it can replace other ANSI pumps in the DAP family without changing the pipeline system. Options for high-temperature systems are also available.
It can withstand the highly corrosive and abrasive slurries of most industries with various materials you can choose from:
Investing in the equipment that will make your process smooth, defect-free, and productive will surely lead you to better business profitability. Although there are a lot of aspects that govern your business costs, surely, a big percentage of that is your equipment.
With the vast selection of hard metal pumps in the market today and the increasing demand for it, it is easy to be overwhelmed. But if armed with the basic knowledge about it, you will surely find something fit for your process.
Take the time to understand your system requirements and contact Pye-Barker Engineered Solutions, your trusted equipment provider, for more assistance.
Last month I shared with you six mistakes that could be shortening the life of your pumps. In this follow up article I’ll share with you another six mistakes that could be shortening the life of your pumps.
Not Minimizing Radial Force
Industry statistics indicate that the biggest reason centrifugal pumps are pulled from service is the failure of bearings and/or mechanical seals. Bearings and seals wear and tear give you a good idea of what is happening inside the pumping system.
To minimize radial force run your pump at its Best Efficiency Point (BEP). At its BEP, by design pumps will experience the lowest amount of radial force. High radial force and shaft deflection are a killer of mechanical seals and a contributing factor to bearing life reduction.
Not Changing Your Oil On Schedule.
For ball bearings, more than 85 percent of bearing failures result from contamination, either dirt and foreign material or water. Just 250 parts per million (ppm) of water will reduce bearing life by a factor of four.
Operating a pump can be similar to operating a car continuously at 60 miles per hour… Driving 24 hours per day, seven days a week, puts plenty of ‘miles on the clock’ —1,440 miles per day, 10,080 miles per week, or if you will 524,160 miles per year. You’d be checking your car’s oil regularly if you were doing those sorts of miles wouldn’t you? Why not check your pump’s oil regularly too?
Not Reducing The Risk of Cavitation.
Cavitation will create damage to the pump impeller, and resultant vibrations will affect the seals and bearings. Cavitation is minimized by having a large margin between net positive suction head available (NPSHA) and the net positive suction head required (NPSHRR).
Running Your Pump At High Speeds
A 3600-rpm pump will wear out faster than a 1800-rpm pump by a factor of 4-to-8. So if you’ve got to run a pump at high RPMs, when it does finally wear out be sure to look for a pump that can move the same volume of material while running at a lower speed.
I recommend that impellers be balanced to International Organization for Standardization (ISO) 1940 grade 6.3 standards at a minimum. If the impeller is trimmed for any reason, it must be re-balanced.
An unbalanced impeller on an overhung pump or on some vertical designs can cause a condition known as shaft whip, which deflects the shaft just as a radial force does when the pump operates away from the BEP. Radial deflection and whip can occur at the same time.
Too Many Casing Penetrations
Many end users want the casing drilled and tapped for drains, vents, gauge ports or instrumentation. The problem is pump casing penetrations shorten pump life. Every penetration is primed for corrosion and stress risers. It’s a trade-off.
If you find yourself frustrated with pumps being continuously offline for unscheduled maintenance or need to increase the life of your pumps give the team at Pye-Barker a call at 404-363-6000 or drop us a line at email@example.com we will advise you on your best options to increase your pump life.
Today I’m going to go through the remaining 5 categories of problems we see all too often with centrifugal pump installations.
Centrifugal pumps are the exception to the rule about pipe size – experienced pump users know they need a suction line to be one size larger than the pump suction… Not for self-priming pumps.
The bigger pipe means there will be more air in the line – which means you have longer waits for the pump to prime.
You need to make sure that the suction pipe never goes above the pump’s suction inlet. Any piping above the inlet is a place for air/other non condensable gases to collect… which can bind the suction line.
Any time the temperature drops below freezing for more than an hour or more there is a risk any water in the pump will solidify. When water (unlike most liquids) freezes it expands, which can cause the casing to crack – an unnecessary expense and a big one too.
When there is a risk of freezing nights, either drain the fluid out of the pump or supply a heat source when the ambient temperature is predicted to fall below freezing.
When centrifugal pumps run in reverse (by accident or by design), the impeller may eventually come loose and damage the pump. Backward-running impellers generally only create about 50 percent of the rated flow and only generate about 50 percent of the rated head.
If your pump is under-performing check to see it is running in the right direction. It’s far less embarrassing when you figure it out yourself rather than place a service call, and our techs come out to they tell you it’s being installed backwards.
Using Non-collapsible flex piping is a convenient form of piping when you need a portable pump unit. However, the internal diameter (ID) of flex pipe is smaller than the same sized standard pipe.
This means you need to recalculate the pipe friction for the NPSHA and make sure your flex piping is strong enough to withstand the suction.
By calculating NPSHA you know the minimum operating level your sump needs to be and can spot air binding risks more easily.
For example, if the fluid is 160 degrees F, the vapor pressure of the fluid alone will likely preclude you from this application. For example, water at 160 F has a vapor pressure that equates to a negative 11 feet.
If the sump you are drawing from will likely have constantly changing levels, at some level of submergence it will be possible for the system to create a vortex and air bind the pump. Even if the pump is not completely air bound, performance can still be affected.
Knowing NPSHA means you’ll be able to keep enough liquid in the sump to avoid air binding your pump.
If you are having trouble with your centrifugal pumps give Pye-Barker a call at 404-363-6000 or drop us a line firstname.lastname@example.org we can help you troubleshoot your centrifugal pumps or help you select the right replacement if that is the best course of action.
We do our share of field service for centrifugal pumps – when we get there we often see them being used beyond their specifications and obviously that is when trouble strikes.
If you boil all the problems down, they fall into 10 categories. I’ll deal with the first five now and we’ll dive into the next 5 in a later post.
Centrifugal Pump Mistake #1: Too Much Suction Lift
Play it safe and don’t force your pump to do more work than it has to. Otherwise you are facing unnecessary downtime and additional repairs that could have been avoided.
In many cases when a pump goes down the whole system goes down – so the cost of lost running time is much higher if you calculate the value of the whole system. When you design the system keep the lift well within the limits.
Centrifugal Pump Mistake #2: The pump is too far from the liquid source.
Intelligent system designers know that the suction pipe length be held to a minimum to promote long pump life. Every section of suction piping equates to a volume of air that must be removed when the pump starts. Best practices say to reduce priming time to a minimum.
The literature recommends no more than 30 feet but closer is definitely better. See what I said about suction lift and downtime.
Centrifugal Pump Mistake #3: Leaks in the suction line.
The suction line on a self-priming pump is at less than atmospheric pressure. That means liquid doesn’t leak out of the suction line. Air leaks into the line.
A roll of kitchen cling wrap can be used to test for air leaks – just wrap the line in plastic and see if it is sucked anywhere.
The golden rule is, if your pump takes more than four minutes to prime then you should call in your maintenance team.
Centrifugal Pump Mistake #4: Air/Gas Binding
When you start a centrifugal pump, the air in the suction line needs to be vented otherwise it will form pockets around the impeller – which spins in the air and it heats up… as obvious as this remedial lesson is – we still see air bound pumps…
Make sure some sort of vent is installed so that air can escape while the pump is priming. We are more than happy to make sure your design meets proper pump specs.
Centrifugal Pump Mistake #5: Failure to Complete The Initial Priming
Okay – so the name is slightly misleading. There are warnings in all the product literature yet this still happens from time to time.
There is a priming chamber of some description in all centrifugal pumps. This needs to be filled prior to operation. There are lots of ways to do this – check your documentation and consult with the system designer for the best practice in your situation.
Finally remember: If there is evaporation of the fluid in the priming chamber, leakage, pump movement or maintenance your ‘self-priming’ pumps need to re-primed.
Looking to install a new system with centrifugal pumps? Call 404-363-6000 or drop us a line at email@example.com and the team at Pye-Barker can review your system and/or recommend the right pumps and make sure you won’t have any trouble with pump performance. Or we can help you troubleshoot a problem system with you.
Historically our clients have been very diligent about installing monitoring solutions for their mission critical pumps. Due to the cost of installing the system and the cost of ongoing maintenance of the system, condition monitoring solutions for all pumps on site has been typically unrealistic.
Manual monitoring of the remaining pumps or a policy of ‘run until breakdown’ is normal which in light of today’s technology can prove to be MORE expensive and unnecessary.
Older monitoring systems meant wiring the sensors into the control center; it was expensive, time consuming and created a lot of infrastructure to maintain.
It meant a limited roll out of electronic condition monitoring to pumps with either a high risk of maintenance issues or a high impact when a maintenance issue does occur. For example – pumps that have repeat failures, pumps without spares or pumps where failure could cause an environmental incident.
With the advances of wireless technology the same monitoring systems can be installed without the time or expense of maintaining a complicated infrastructure. It has now become affordable to install a higher quality monitoring system across more of your pumping process system.
These three monitoring applications can help a plant implement predictive maintenance systems which can reduce maintenance costs, unexpected failures, repair and overhaul time – and at the same time increase uptime by up to 30% and increase MTBF.
Affordable Monitoring Application #1: Cavitation
While many cases of cavitation occur when a pump is operated outside of their design specifications, there are still times when a pump operating within its specifications can still experience cavitation.
A simple discharge pressure monitoring system (consisting of vibration monitoring and discharge pressure) can give your central monitoring system an alert when a pump is likely ‘pre-cavitation.’ Depending on the frequency of manual rounds this might mean the prevention of damage and downtime compared to discovering cavitation in progress.
For high-head multi-stage pumps – the risk of damage with even brief periods of cavitation means that pressure differential across the pump should be continuously monitored.
Affordable Monitoring Application #2: Vibration
Vibration monitoring systems can give you indicators on running condition as well as faults and failures. Vibration transmitters can give you a series of vibration frequencies which can in turn be used to diagnose the cause of the vibrations in a given pump.
Affordable Monitoring Application #3: Pump Seal Monitoring
For pumps that have auxiliary seal flush system, API 682 recommends moving from switches to continuous level management.
With recent advances in technology, rather than having to wire the monitoring system into the network it can be installed wirelessly and then connected to the central monitoring system.
I’ll admit it may take some retrofitting of technology to get the seal flush reservoirs installed so they can be remotely monitored. But continuous monitoring will give far more lead time to address maintenance issues compared to intermittent manual maintenance inspections of pump seals.
If it is time to increase the reliability of your pumping systems then the team here at Pye-Barker can help you select and install pump monitoring systems for your plant. Drop us a line at firstname.lastname@example.org or call 404-363-6000 for help with all your pumping system needs.
A couple of months back I shared with you three all too common mistakes I see our clients’ maintenance teams make that damage their pumps and shorten their lives, leading to costly repairs, more downtime and unnecessary replacement.
So if you have budget to burn and really want to give us the money to prematurely replace your pumps then by all means do the OPPOSITE of what I’m advising you to do here.
Otherwise – if you want to minimize your downtime and maintenance costs while maximizing the life of your pump then I suggest you avoid these pump ruining ‘tricks:’
Letting Your Pump Run Dry
Don’t do it. When your pump runs dry it can quickly cause pump cavitation and mechanical seal damage – Mechanical seals can get so hot when a pump is running dry that it can shatter in about 30 seconds.
So if a pump is running dry for any reason - shut it off as soon as possible - but RIGHT NOW would be better.
Blocked Balance Holes and Vanes
When solids that are too big get pulled into the pump they can block up your balance holes and vanes. When this happens your pump is at risk of having unequal pressure which creates and an impeller imbalance.
You’ll see priming issues and high vibration. If this goes untreated you’ll eventually sustain bearing and seal damage to your pump.
Regular maintenance and proper filtration of your fluids will keep the risk of this happening to a minimum.
Using the Wrong Sized Impeller
I don’t know why this happens but I’ve seen pumps that have had the wrong sized impeller put back in them during a routine service. We provide the impeller when we install or supply our pumps, for a reason:
If you’ve replaced the specified impeller with one that is too big, the pump will begin to work harder to pump your fluids – causing premature burnout.
If the new impeller is too small then it will probably not generate the flow or head you need for your system. That sounds frustrating doesn’t it?
If you’ve got a pump that is consistently down for maintenance or not lasting like you expected it to then there may be an opportunity for improvement. You can get some help just by giving one of the team here at Pye-Barker a call at 404-363-6000 or drop us a line email@example.com.
Two common descriptions of pump pressure are PSI (pounds per square inch) and TDH (total dynamic head). PSI is usually associated with positive displacement pumps and TDH with centrifugal pumps, but the terms are interchangeable.
PSI is usually stated in gauge pressure as PSIG, the pressure you read on a pressure gauge. Negative pressure is usually stated in inches of mercury vacuum, HgV. These are common values used in America, but pressure can be translated into metric and other terms.
Differential pressure (ΔP or delta P or DP) is the difference in pressure across the pump. Differential pressure is used for pump and motor selection as it is the actual pressure the pump sees. DP is the pressure on the suction side of the pump plus the pressure on the discharge side of the pump in relation to the desired discharge pressure. If 50PSI is the desired discharge pressure and you have +10PSI on the suction side, the pump needs to develop 40PSI for the total discharge pressure to equal 50PSI (+10+40). Likewise, if the suction pressure was negative -5PSI (~10”HgV) such as a suction lift application where the liquid level is below the pump, the pump would have to develop 55PSI (-5+55) to achieve the total discharge pressure of 50PSI.
PSIA is pressure per square inch absolute. This takes into account atmospheric pressure. 0PSIG is equal to 14.7PSIA at sea level or 33.9’ of water column (atmospheric pressure decreases with altitude, for example: 14.2PSIA at 1000 ft. elevation).
TDH or total dynamic head is another common term for describing pressure across a pump. Every 2.31’ of vertical level = 1 PSI for water and liquids with a specific gravity of 1 (or 8.34 pounds per gallon). For liquids heavier than water, the pressure exerted is greater for the same vertical level. For example; a tank with 23.1’ of water level would read 10PSI on a pressure gauge at the bottom of the tank [(23.1ft./2.31ft/psi)X1SG=10psi].
With a liquid with a specific gravity of 1.2 (10 pounds per gallon) at the same 23.1 foot level, the pressure gauge would read 12PSI [(23.1ft./2.31ft/psi)X1.2SG=12psi].
And a pressure gauge would read less for liquids lighter than water.
Many of my customers ask “WHY DO I NEED A SUCTION STRAINER FOR OUR NEW PUMP?”
Below are the primary reasons:
VIKING internal gear PD pumps have tight strict internal clearances and if the inlet fluid could contain a high particulate concentration from pipe debris or fluid hardening that may cause restriction in pump clearances specified causing excessive heat and potential cavitation that could cause short pump life and the downtime to inspect and repair pump may be cost prohibitive to your production requirement. A suction strainer is a relatively inexpensive item compared to cost of new or repaired pump and should be considered as an insurance investment. Centrifugal pumps that have enclosed trimmed impellers can also see blockage with potential same outcome from cavitation or short pump life from heat bearing failure. An inlet suction basket strainer or Y-strainer can be supplied with several filter mesh liners for specific size particulate seen. If your fluid has high particulate due to fluid composition then a no mesh basket can be supplied with approximate 3/16” perforated basket. Look at your cost of lost production time or pump repair time and you will see the minimal cost of a suction strainer is justified.
Many fluids may be harmed from pipe scale seen on inlet of pump or from the pump bushings or other internal pump parts that contain carbon or iron. Again, an inlet pump strainer will protect your fluid from these damaging materials.
VIKING PUMP has partnered with EATON STRAINERS for inlet simplex and duplex strainers with many different materials of construction and port configurations. See link for more information.
VIKING LIDEASE strainers is a proven simplex suction strainer supplied for many years has an easy opening cover is another option. See link for more information.
If your production process cannot allow downtime to clean or replace internal strainer baskets then the EATON duplex strainer is best recommended option.
If you consider your fluid a clean fluid and inlet piping not an issue then a suction strainer may not be needed.