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A little bit more about Cavitation
Just what then is this thing called cavitation?
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A little bit more about troubleshooting centrifugal pumps and mechanical seals
One of the U. S. based Japanese automobile manufacturers has a unique method of troubleshooting any type of mechanical failure. The system is called the "Five Whys".
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A new way of classifying chemicals to assure effective sealing
The most common question asked by seal salesmen is "what are you sealing?"
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A technique for making pump troubleshooting decisions
The rules are very simple. Decisions have to be made when doing nothing will cause the condition to degenerate.
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A.P.I. (American Petroleum Institute) and C.P.I. (Chemical Process Industry) merger
Any prediction about the future of the pump and seal business would have to include the high probability that the CPI will adopt the API seal standard
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Affinity laws for positive displacement pumps
The affinity laws accurately predict the affect of changing the speed of a positive displacement pump
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Affinity laws- what happens when you change the pump speed or impeller diameter?
There are occasions when you might want to permanently change the amount of fluid you are pumping, or change the discharge head of a centrifugal pump. There are four ways you could do this
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Alignment between the pump and driver
In the pump business alignment means that the centerline of the pump is aligned with the centerline of the driver. Although this alignment was always a consideration with packed pumps, it is critical with sealed pumps especially if you are using rotating seal designs where the springs or bellows rotates with the shaft
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All about impellers
Simply - all about impellers!
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All about NPSH 15
Simply - all about Net Positive Suction Head (NPSH)!
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ANSI pump Standard
ANSI is an acronym used to describe the American National Institute Pump Standard. The standard evolved from the American Voluntary Standard (AVS) that was first proposed by the Manufacturing Chemists Association in the nineteen fifties. It is a set of inch dimensional standards that describe the envelope dimensions of a back pull out, centrifugal pump
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API Gland
The seal gland is that part that holds the stationary half of the mechanical seal and attaches to the stuffing box. The most universally used gland is labeled the American Petroleum Institute (API) gland
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API plans that I use
The American Petroleum Institute (API) issues guide lines to help petroleum people select and then pipe various types of controls for mechanical sealing applications. These piping arrangements are described in a series of plans issued by the API.
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Ball bearing lubrication in centrifugal pumps
It turns out that bearings fail for two main reasons: Contamination of the bearing oil by water or moisture or High heat often caused by too much lubrication
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Barrier or buffer fluid. The liquid we circulate between dual seals.
Let's clear up the confusion about flushing seals
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Bearing fit tolerances
Bearing Fit tolerance charts
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Calculating net positive suction head (NPSH) in non-metric units
To calculate the net positive suction head (NPSH) of your pump and determine if you are going to have a cavitation problem, you will need access to several pieces of information
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Calculating the centrifugal pump first critical speed
The first critical speed is linked to the pump's static deflection.
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Carbon graphite seal faces - how they are manufactured and where carbon/graphite cannot be used
Seal companies purchase carbon/ graphite molded faces from one of several carbon manufacturers. The seal companies pay for the necessary molds and then retain the exclusive use of them
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Carbon seal faces; which is best? Solid or pressed in a metal holder?
Carbon Graphite is probably the best seal face you can use in most of your water and chemical applications
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Causes of overheating in cartridge seal designs
Too much heat can cause multiple problems with mechanical seals
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Cavitation
Cavitation means that cavities are forming in the liquid that we are pumping. The cavities form for five basic reasons.
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Centrifugal pump ball bearing seals
Bearings are normally lubricated with either oil or grease. Oil mist is another alternative, but recent fugitive emission regulations are making this form of bearing lubrication less desirable
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Centrifugal pump formulas, rules and definitions
Some of the basics you need to understand centrifugal pumps
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Centrifugal pump shaft displacement
We know that seals fail for only two reasons: One of the seal components becomes damaged, or the lapped faces open
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Centrifugal pumps - what is wrong with their design
Ask for a pump recommendation from your favorite supplier and chances are he will recommend one of the standard pump designs that conform to either the A.N.S.I., I.S.O. or D.I.N. specifications. On the surface that might seem like a good recommendation, but the fact is that all of these designs will cause you maintenance problems
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Centrifugal Pumps: Basic Concepts of Operation - Part 1
- requires free Adobe Acrobat Reader for viewing.
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Centrifugal Pumps: Basic Concepts of Operation - Part 2
- requires free Adobe Acrobat Reader for viewing.
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Centrifugal Pumps: Basic Concepts of Operation, Maintenance, and Troubleshooting
This article, from Mukesh Sahdev, Associate Content Writer at The Chemical Engineers’ Resource Page, covers all aspects of operation, maintenance, and troubleshooting of centrifugal pumps. The article has been written specifically with students and beginners in mind, but is a worthwhile refresher for more experienced engineers.
- requires free Adobe Acrobat Reader for viewing.
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Changing the diameter of the piping to save operating costs
Business has not been that good and production has decided that maybe they can save costs if they increase the piping size so that a smaller and more economical motor can be used and the possibility of cavitation can be reduced. What exactly is going to happen to the horsepower requirement for this new installation? Will the additional cost of converting to larger piping be justified by the lower operating costs?
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Classifying seals by the operating conditions
It is extremely important for any modern process company to have a good set of seal specifications
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Concentric dual seals
Dual seals are recommended for a variety of purposes
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Condensate - why you must seal it
We want to keep dissolved oxygen out of condensate. Why?
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Controlling temperature in the pump stuffing box
Many fluids are adversely affected by a change in their temperature, and when this reaction takes place seal failure is almost sure to follow
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Converting head to pressure
the definition of some pumping terms
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Corrosion problems associated with stainless steel
The rotating equipment business uses a great deal of 300 series stainless steel, and as a result we often experience corrosion that is described in a variety of technical terms
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Dangerous fluids, how to seal them
The definition of fluids includes both liquids and gases and any of these fluids could be labeled dangerous for a variety of reasons
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Density and specific gravity
We often describe a fluid by its "lightness or heaviness".
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Design, operation, and maintenance problems associated with mechanical seals
The purpose of this paper is to give you an overview of the subject, and assist you in your troubleshooting function
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Double volute pump
the advantages of using a double volute centrifugal pump to eliminate radial shaft deflection caused by operating off the best efficiency point (BEP) of a single stage centrifugal pump
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Dynamically balancing the pump rotating components
Everyone agrees that balancing the rotating components of a centrifugal pump is a good idea, but it is seldom done.
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Elastomers - selecting the correct O-ring for the application
The guide is an attempt to select the fewest number of elastomers that will give you satisfactory sealing of most of the chemicals we find in the process industry
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Elastomers - where the special compounds do not work
In recent years the elastomer industry has produced a variety of newer compounds that appear to be getting closer to the universal rubber that we are all seeking. Unfortunately we are not there yet, so this paper is an attempt to put these "super compounds" into a proper perspective
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Environmental controls - controlling pressure in the stuffing box
We have very little control over the products that we must seal, but we have a great deal of control over how we elect to seal them
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Environmental controls and special seals
For any given seal application problem there are two generally accepted solutions
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Estimating the shutoff head of a centrifugal pump
In the fifteenth century the Swiss scientist Daniel Bernoulli learned that the combination of head and velocity was a constant throughout a piping system. He then wrote the formula showing the relationship between this liquid velocity, and resultant head
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EXAKT reduces failures at Canadian Kraft Mill
In 2005, the Toronto based CBM Lab collaborated with a Canadian kraft pulp mill operator to investigate the high incidence of unpredicted failures among a small group of its fleet of Gould pumps. EXAKT, developed by the University of Toronto’s CBM Lab (Condition-Based Maintenance Laboratory), is an advanced failure prediction software package. By analyzing the pump failures, EXAKT provided a statistical decision tool to accurately predict whether the mill could continue to run the pump until the next shutdown.
- requires free Adobe Acrobat Reader for viewing.
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Flow through a Venturi
Here is the formula for an approximate flow through a venturi tube
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Flow through an orifice
The equation for flow through an orifice is a simple one to understand. Only the units are somewhat awkward
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Flow. How the resistance is affected by any change of flow in a pipe
What happens when we change the flow going through a piping system?
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Fugitive emissions - the chemicals on the list
In this paper I have noted the chemicals that are presently on both the Carcinogen and Fugitive Emissions lists. The compounds on these lists should be sealed with two (dual) mechanical seals to prevent their escaping to the atmosphere and violating the applicable restrictions or possible harming personnel in the area
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Grout for the pump base
The forces and vibrations present in our rotating equipment must be absorbed by the foundation or they will be transmitted to the mechanical seal and pump bearings, causing higher stresses and premature failure of one or both of these components
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Head - calculating the total head in inch units
To calculate head accurately we must calculate the total head on both the suction and discharge sides of the pump. In addition to the static head we will learn that there is a head caused by resistance in the piping, fittings and valves called friction head, and a head caused by any pressure that might be acting on the liquid in the tanks including atmospheric pressure, called " surface pressure head".
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Head - calculating the total system head in metric units
To calculate head accurately we must calculate the total head on both the suction and discharge sides of the pump. In addition to the static head we will learn that there is a second head caused by resistance in the piping, fittings and valves called friction head and a third head caused by any pressure that might be acting on the liquid in the suction or discharge tanks including atmospheric pressure. This third head is called " surface pressure head".
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Head - changes in the discharge head
We have to know the discharge head of a centrifugal pump for several reasons. We can have many problems determining accurate head information because of variations in the discharge system
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Head, Pressure and Mr. Bernoulli
The term "pressure" can be a little confusing because the units we use to measure pressure change in various parts of the world
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Heat, how it affects the pump and mechanical seal
Every day salesmen call on customers and make claims that their pump or mechanical seal can take more heat than the other guys. Before we rush out to purchase these wonder products we should take a closer look at the heat problem
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How pipe friction, liquid capacity and pump head are affected by the amount of liquid flowing through a pipe
You can use the following formulas to supplement the Affinity Laws
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How the shape of the pump impeller affect the pump curve
In this paper we are going to see how the shape of the pump impeller affects both the slope of the pump curve and the amount of horsepower that will be consumed by the pump at various capacities
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Hydrodynamic gas seals
The idea is very simple. Let the seal faces ride on a film of gas either pumped to or flowing between the seal faces. Unlike hydrostatic seals that create a balanced opening and closing force to maintain just the right amount of seal face separation, the hydrodynamic seal depends upon the generation of a lifting force to separate the seal faces
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Hydrostatic sealing
This paper is all about hydrostatic sealing and the principle behind this type of seal is not too difficult to understand
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Increasing the centrifugal pump performance by modifying the impeller
What happens when you reduce the impeller vane diameter?
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Installing pump piping
A few things you should know about your pump's piping system
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Installing pumps
A reminder of a few things you should know about installing pumps
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Maintenance practices that cause seal & bearing problems
Here are some of the maintenance practices that increase pump failure rate
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Mechanical Seal hydraulic balance
Seal hydraulic balance is one of the most effective tools we have to counter the detrimental affects of heat being generated in the stuffing box area. The original patent for hydraulic balance was granted in 1938, but the concept has never been adopted by the "original equipment manufacturer" (O.E.M.), and so to this day it remains only as an "after market" product.
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Metal bellows seals
An overview of metal bellows sealing
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Monitoring the centrifugal pump
A sensible predictive maintenance program for centrifugal pumps is still an elusive dream for most plants
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More about packing conversion
Sales people constantly preach the virtues of converting that nasty, greasy packing to a brand new, shiny, expensive mechanical seal. Their presentation makes a lot of sense and besides that the government is passing new legislation that is making conventional packing more obsolete by the minute.
If you are about to make one of these conversion in your plant there are some things that you should know to make the transition easier
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Non metallic seals
A portion of the chemical industry use non metallic pumps. You will find them manufactured from Teflon®, graphite, Carbamate, and a variety of other materials.
Common sense dictates that if the application engineer selected a non metallic pump, he must of had a good reason for doing so, and it would not be logical for you to equip it with a mechanical seal containing metal components exposed to the product unless you had specific knowledge that doing so would make some kind of sense.
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NPSH - A Discussion
The one hydraulic characteristic that is least understood by the people who maintain, or operate pumps is the Net Positive Suction Head (NPSH). Most of the literature available on this subject is complex in nature and tends to confuse those who have little experience in pumping technology. The purpose of this paper is to explain as simply as possible the many factors affecting NPSH.
- requires free Adobe Acrobat Reader for viewing.
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NPSH required, allowable reductions
The curve that came with your pump shows the NPSH required for any given impeller size and capacity. This number was determined by pumping cold water through the pump while reducing the suction head until the pump showed a reduction in discharge head of three percent (3%), due to the low suction head and any formation of bubbles within the pump. This point is called "the point of incipient cavitation.
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Open vs.Closed impeller design pumps
There are advantages and disadvantages to each design
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Operating practices that cause maintenance problems
There are three types of problems we encounter with centrifugal pumps and poor operation is one of them.
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Oversized pumps
Do a survey of any process plant and you will find that a high percentage of the centrifugal pumps are oversized. There must be a reason why this is such a common problem
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Packing conversion - why you should do it and the possible savings
Packing conversion is a subject that has become more important in recent years. The savings that are real and easily measurable
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Parallel piping for pumps
There are some considerations you must address when using parallel pumps
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Positive displacement pump troubleshooting
A troubleshooting guide for positive displacement pumps
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Positive displacement pumps
Rotary pumps make up about 10% of the pumps we use in industry. Unlike the more common centrifugal design they are PD (positive displacement) pumps
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Predictive maintenance for centrifugal pumps
Is there a reliable method of introducing a centrifugal pump predictive maintenance program?
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Preventative maintenance - pumps
A sensible preventative maintenance program for centrifugal pumps cheat sheet
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Preventative maintenance - pumps and seals
Pump and seal preventative maintenance - what is it all about?
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Preventative maintenance - seals
A sensible preventative maintenance program for mechanical seals, cheat sheet
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Priming the centrifugal pump
Why you must prime a centrifugal pump
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Pump and seal problems with no apparent cause
These problems are the ones that drive you crazy. No matter how hard you look the solution keeps evading you. Over the years I have collected quite a few examples. I offer some of them for your enjoyment and maybe, in the process, they will help you solve the "un-solvable"
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Pump bearings, why do they fail?
Most of us change the bearings every time we disassemble the equipment to replace the mechanical seal or the packing sleeve. Is this really a sensible thing to do?
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Pump charts and graphs you will need
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Pump curve - how to read one
How to read a pump curve
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Pump efficiency - figuring the heads
How efficient is your pump?
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Pump efficiency - making the calculations
What do we mean by pump efficiency?
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Pump it up! Online Pump resources
Some great Web sites related to pumps
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Pump modifications to increase seal life
Pump modifications you can make to increase the life of mechanical seals and centrifugal pump bearings
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Pump Partnering
With all the current talk about seal partnering, can pump partnering be far behind? As with mechanical seals the concept is simple; call in several pump companies, talk to them about a lot of lofty ideals and then learn which of them will give you the best price on a standard ANSI (American National Standards Institute) pump if you promise to give them all of your business.
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Pump Performance Checklist
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Pump rebuilding tips
Some pump rebuilding tips to prevent future vibration problems
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Pump reliability
Have you joined the bandwagon? Are you purchasing to a company or engineering standard of some type and made the capital investment in the reading and recording data?
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Pump selection practices that cause maintenance problems
Purchasing well designed hardware does not bring automatic trouble free performance with it. The very best equipment will cause problems if it was not designed for your particular application
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Pump-related conversion tables
Velocity, Mass Flow rate, Force, Pressure and Liquid Head, and more
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Pumps - additional information you need
Some more things you should know about centrifugal pumps
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Pumps installed in pits.
How to correct some existing suction problems
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Pump-Zone.com
Many articles about anything related to pumps
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Radial thrust calculations for centrifugal pumps
Pump shaft radial thrust alternative calculations (in Imperial dimensions)
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Reading seal face flatness
There is often confusion between the terms "Seal face flatness" and "Seal face surface finish".
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Recipe for a Reliable Brew
How one brewery saved nearly $200,000 each year through intense asset management and optimization
- requires free Adobe Acrobat Reader for viewing.
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Repair of mechanical seals
The days of sending mechanical seals back to the manufacturer, or having a local repair facility repair your seals will shortly come to an end
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Resonance Analysis - a Vertical Pump Case Study
This article written by Ali Al-Shurafa of Jubail Industrial College in Saudi Arabia describes a vibration analysis case study, examining resonance in a vertical pump used to deliver sea water to a power station's cooling towers.
- requires free Adobe Acrobat Reader for viewing.
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Rubber bellows seal
Available from a number of seal companies (the Crane #1 is typical), and manufactured in a variety of materials
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Rules of thumb - pumps
If you want to know a pumps capabilities the rules are simple, look at the manufacturer's published pump curve. The problem is that you do not always have the curve available. Pump companies test their pump to determine its performance, they have no need for general guide lines or "rules of thumb."
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Rules of thumb - seals
The following is offered as a guide when dealing with mechanical seals in general
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Rules of thumb -seals and pumps
The biggest advantage of experience is you have hopefully learned what can get you into trouble. The following information has been explained in detail in previous technical papers, but I still see the same problems re-occurring on a daily basis
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Seal Application. Do you have one?
You have three opportunities to do a mechanical seal application
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Seal design - the questions you should ask
How do you test a mechanical seal? No two pumps are exactly alike; what is a fair test? Too often we test only how the seal performs when all the operating conditions are known and the seal is installed correctly.
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Seal face hardness testing
The common methods seal people use to measure the hardness of a seal face
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Seal face lubrication
What is really happening between the mechanical seal faces?
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Seal failure - some things you can do to prevent it
Preventing premature seal failure
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Seal features - the ten most important
The ten most important features you can specify in a mechanical seal design
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Seal hydraulic balance - two way balance for dual seals
There are several reasons why you might want to invest in the higher cost of installing two seals in your pump, or some other pieced of rotating equipment
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Seal improvements in recent years
Where have we been, and where should we be going?
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Seal installation
Common seal installation mistakes that cause premature mechanical seal failure
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Seal life - how to get good seal life
How to get good mechanical seal life
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Seal metal parts - selecting the right ones
Selecting the correct metal for the mechanical seal components
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Seal misconceptions
Some common misconceptions about mechanical seals
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Seal partnering
The latest fad to hit the process industry is "partnering" allowing industrial academics to have a wonderful time thinking up these new projects so that they will appear to be doing something productive and useful. Although "partnering" implies many lofty benefits it always ends up being nothing more than purchasing negotiating a large discount from the seal manufacturer. The really important stuff that is costing you the most money, always takes second place.
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Seal value - how to get good value
Getting what you pay for
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Sealing Energy Savings
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Sealing products sensitive to a change in temperature or pressure
In this paper we will be considering how small changes in either temperature or pressure will cause failures to occur, and learn how to prevent these changes especially when the pump is stopped and often subject to both temperature and pressure fluctuations
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Sealing products sensitive to agitation
This category of sealing is the one that is the least understood by most of the people that are involved in the process industry.
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Seals - as supplied by the original equipment manufacturer- the problems
The next time you purchase a pump, mixer or some other type of rotating equipment and request that it be supplied with mechanical seals you are going to be very disappointed in the performance of those seals unless you specify exactly which brand, model and materials you want.
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Seals - preventing premature failure
What is the best way to prevent a premature seal failure? Find out what is causing the failure and then take the necessary steps to prevent it.
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Seals - the most asked questions
he most asked questions about mechanical seals
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Seals classification
The classification of mechanical seals
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Seals. Which one should you buy?
You're going to have to figure that one out yourself, but I can tell you which designs not to buy
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Selecting the correct hard face seal material
A good mechanical seal should run leak free until the carbon/graphite seal face wears away
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Selecting the correct horsepower motor
Electric motors operate at their best power factor and efficiency when fully loaded so you do not want to purchase a motor that is too big, and common sense dictates that one that is too small is even worse. In the following paragraphs we are going to learn how to select the correct motor for your centrifugal pump application
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Selection And Procurement Of Pumps For Replacement
Reviews the various situations in which it may be better to replace, rather than repair, a pump
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Self priming pumps
The concept is simple. Change the pump design so that the pump will retain enough fluid when it stops, to start again without having to worry about re-priming
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Shaft deflection
Solving a major cause of shaft deflection in volute type pumps
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Shaft deflection
Shaft deflection is certainly undesirable
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Shaft deflection - some calculations in inch and metric
Shaft deflection and the pump best efficiency point
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Shaft deflection - three rules
The three magic formulas you need to know if you want to understand how centrifugal pumps function
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Shaft deflection direction when operating off the BEP
Some additional information about shaft deflection
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Shaft displacement and original equipment seals (O.E.M.)
Shaft displacement and the original equipment seal (O.E.M.)
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Shaft fretting. What causes the problem?
The next time you remove a grease or lip seal (the rubber seal located next to the bearing) you will note that the shaft is grooved and damaged under the rubber lip. You will see this same damage in a few other locations also
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Siphon, How it works
Now just what is a siphon?
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Specific gravity
It is important that you do not confuse specific gravity with viscosity
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Specific speed - how to calculate it
Specific speed is a term used to describe the geometry (shape) of a pump impeller. People responsible for the selection of the proper pump, for their application, can use this Specific Speed information
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Specific speed vs. suction specific speed
The difference between specific speed and suction specific speed
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Split mechanical seals
The split seal is the one seal that every consumer wanted. The main reason that people continue to use packing is that no one wanted to take the pump apart just to fix a leak
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Stable temperature probes for hydraulic efficiency measurements
For the instrument designer, the main challenge of the thermodynamic method is the stable and accurate measurement of dT, the differential temperature, which will vary with total head and pump efficiency.
- requires free Adobe Acrobat Reader for viewing.
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Stable temperature probes for hydraulic efficiency measurements
Robertson Technology Pty Ltd has developed technology for measuring the differential temperature (dT) across a pump to an accuracy of better than 1mK, with long-term stability over periods of years. This technology has been applied to both portable and permanently installed (fixed) thermodynamic pump performance monitors, and has also been utilised for measurements with turbines.
- requires free Adobe Acrobat Reader for viewing.
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Standby pumps. Should they be run?
If there were a simple answer to this question, it would never come up. The more I look into the subject, the more I'm convinced that there is no easy answer
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Stationary vs. Rotary seals
One of the most difficult concepts to teach in writing is the difference in operation between stationary and rotating mechanical seals. It is like trying to write a set of instructions as to how to tie your shoe laces, easy to demonstrate, but difficult to explain
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Stuffing box
Next to stabilizing the pump shaft, without question the single most effective action you can take to increase the life of your mechanical seal, is to replace the present narrow stuffing box with one of the newer more open designs
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Suction throttling
Throttling the discharge of a centrifugal pump is a common method of stopping a cavitation problem
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System curve for positive displacement pumps
Every pump manufacturer would like to recommend the perfect pump for your application. To do this he would like you to provide him with an accurate system curve that would describe the capacity and head needed for your various operating conditions
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Technical term correlations
If you are going to be messing around with pumps, bearings and mechanical seals, these words are going to have to become a regular part of your vocabulary
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Temperature - causes of a rise in stuffing box heat
Many factors contribute to a change in the pump stuffing box temperature
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Testing for Net Positive Suction Head Available (NPSHA)
Centrifugal pumps are designed to pump liquids, not air. We are interested in the amount of NPSH available at the pump's suction flange because we want to insure there is enough head (pressure) available to prevent the fluid from vaporizing and causing gas bubbles.
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Testing for Net Positive Suction Head Required (NPSHR)
How can you tell the NPSH required for your pump? It's easy, just ask the manufacturer!
As logical as that sounds, we still find people assuming that if the know the NPSHR for pump brand "A" and pump brand "B" is the same size, both pumps should have the same requirement. So why isn't it true?
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The centrifugal pump is drawing too much amperage
This is the third paper in a four part series about pump troubleshooting
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The centrifugal pump is not producing enough capacity
This is the second paper in a four part series about pump troubleshooting
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The centrifugal pump is not producing enough head
This is the first paper in a four part series about pump troubleshooting
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The centrifugal pump looses suction, the pump is cavitating
This is the fourth paper in a four part series about pump troubleshooting
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The Critical Mistake Of Assuming That Clean Water Circulation Means A Clean Piping System
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The non seal pump
Non-leak pumps have been the dream of pump designers ever since the first pump was invented back in the dark ages
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The problem with pump standards
A Quick check of existing pump standards will reveal that there are a variety of them
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The reasons for premature bearing failure
Bearings have no wearable surfaces, they are instead designed to fatigue after many hours of service
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The relationship between the pump L3/D4 and premature seal failure
Some pump and mechanical seal sales people talk about L3/D4 . How important is the number when it comes to selecting a pump?
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The sealing of high pressure and hard vacuum
High pressure does three things that will damage any mechanical seal
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The sealing of hot oil
The largest user of hot oil pumps is the heat transfer oil customer. Many consumers use these products with oil temperatures exceeding 500° Fahrenheit (260° C.) and 600° to 700° F. ( 315° to 370° C.) becoming common
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The sealing of hot water
Water is normally considered a good lubricant and can do an adequate job of providing lubrication between the lapped faces of a mechanical seal, but there are a few problems
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The sealing of liquid slurries
Whenever you deal with slurries there are several problems you must consider
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The sealing of mixers and agitators
Tips for better sealing of mixers and agitators
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The sealing of non lubricants
When we are discussing mechanical seals, a lubricant is defined as a fluid that has a film thickness of at least one micron (0.000039 inches) at its operating temperature and load. If the product we are sealing is not a lubricant we are forced to use the self lubricating characteristics of the carbon/ graphite mixture used in the manufacture of the seal face.
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The ten most important features you can specify in a single stage centrifugal pump design
Here they are in no particular order
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Training for pumps and seals
I often get e-mail inquiries asking about how to set up a pump and seal training program within a company. The inquiry almost always refers to a "hands on program" implying that this should be the program of choice. Is there a way to set up such a program?
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Troubleshooting common centrifugal pump problems
You have four opportunities to trouble shoot centrifugal pumps and each opportunity can offer you a clue as to what is wrong with the pump
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Troubleshooting mechanical seal failure, a quick reference guide
Of all the seal related activities, analyzing mechanical seal failure continues to be the single greatest problem for both the consumer and the seal company representative
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Troubleshooting mechanical seals at equipment disassembly
After the failure has occurred you will frequently get a chance to analyze the failed components. You are going to be looking for several things.
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Troubleshooting mechanical seals at the pump site
Leakage can occur at any time throughout the life of the mechanical seal. To troubleshoot seals effectively it is helpful to know just when the leakage starts. This is the advantage of being able to troubleshoot a running pump or one that is still hooked up to its piping
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Troubleshooting mechanical seals, an overview of the subject
Seal problems are almost always associated with face leakage, but as we will soon learn there are other leak paths in addition to the obvious one between the lapped seal faces
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Troubleshooting rub marks in a centrifugal pump
When a centrifugal pump is disassembled there are a couple of things visible to the trained trouble shooter. He can see either corrosion or evidence of rubbing, damage or wear.
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Using a variable speed motor to control flow in a centrifugal pump
If you operate too far off the pump's BEP(best efficiency point) the shaft will deflect radially and that could lead to both seal and bearing problems. So what should you do if you have to vary the capacity of a centrifugal pump?
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Using Pump terms
In any discussion of centrifugal pumps you will find that there are several terms that are interrelated
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Vacuum pumps
The idea is simple enough. The pump will be designed to pump liquid as well as gas or vapors. If you need to create a vacuum you can connect your piping to the suction side of the pump, but if you need a positive pressure you can connect the piping to the discharge side of the same pump.
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Venting horizontal pumps
Heat is always a problem with mechanical seals and any heat generated in the stuffing box is never desirable. When we fill the pump with liquid, air frequently becomes trapped in the stuffing box with no logical way for it to vent
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Venting vertical pumps
Vertical pump applications are very different than horizontal pump applications because the stuffing box is often the high liquid point in the system. Air becomes trapped in the stuffing box and cannot get out.
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Vibration in a centrifugal pump - causes and cures
It is necessary to be interested in vibration because it has a major affect on the performance of your pump
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Viscosity
A primer on viscosity
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Viscosity corrections for Centrifugal Pumps
Viscosity corrections to the pump curve
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Water horsepower - how to make the calculation
How to the calculate the water horsepower coming out of the pump
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What is the best pump and seal technology?
The "Best Technology" phrase comes up in recent government regulations and every day plant conversations. So what is the best Mechanical Seal and Pump Technology available today?
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Why do not good seals wear out?
We know that a mechanical seal is supposed to run until the carbon wears down, but our experience shows us this never happens with the original equipment seal that came installed in the pump. We buy an expensive new mechanical seal and that one doesn't wear out either. What is wrong? Was the new seal a waste of money?
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Why Seals Fail
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