the 5 mistakes on pump.pdf

8/14/2019 the 5 mistakes on pump.pdf

http://slidepdf.com/reader/full/the-5-mistakes-on-pumppdf 1/45

The Five Costly Mistakes

That AlmostEvery Company

Makes With Their Pumps

…..and how to avoid them.

by Ross Mackay

Ross Mackay Associates Ltd.

www.rossmackay.com

http://www.rossmackay.com/




The 5 Costly Pump Mistakes Page 1

© Ross Mackay Associates Ltd. www.rossmackay.com

Introduction

A story is told about the golf touring professional, Ben Crenshaw whowas having difficulty with his sand wedge out of the traps around the

greens. He approached his coach, the famous Harvey Pennick, and asked

for help. Harvey immediately started talking to Ben about his mid and

long iron clubs. Ben patiently explained that it was not his other irons

that were the problem, only the sand wedge out of the bunkers. At this

point Harvey Pennick is reputed to have stated,

“We’ll discuss how to get out of the sand traps,

once we’ve stopped you hitting into them in the first place.”

In other words, before we start talking about getting out of the pump

trouble we’re in, let’s follow Harvey’s advice and first consider how not

to get into trouble in the first place.

By correcting – or better yet,avoiding

– the problems that are created bythese 5 Costly Mistakes, you will be able to achieve some very enviable

results. You will....

• extend the life of your pumps,

• eliminate repetitive failure,

• reduce the cost of operation,

• minimize routine maintenance,

• stop unscheduled downtime, and

• improve the reliability of your operating system.







Why Me?

Through our Mackay Pump School, we have trained over 25,000operations and maintenance engineers and technicians in Science of

Pumping Reliability. These clients come from a wide range of industries

that are dependent on the efficient movement of liquids, such as Pulp &

Paper, Power, Petro-Chemical, Water/Waste Treatment, and many others.

The Mackay Pump School is a comprehensive series of training sessions

which combine into a Reliability Training Program focused on improving

trouble-shooting skills to increase pump reliability and thus eliminateongoing and repetitive pump failure. Implementation of the ideas

presented in this school has saved end users millions of dollars in

increased efficiency and reliability.

I have also written “The Practical Pumping Handbook ” and “12 Steps to

Mechanical Seal Reliability” as well as the video learning program, “A

Practical Approach to Pumping”, that explores the three vital areas of

pump mechanics, system hydraulics and seal operation, integrating themto simplify root cause analysis and effective trouble-shooting. All three

have been highly recommended for those seeking a further appreciation

of process pump design and operation.

My background includes graduating from Stow College of Engineering

in Glasgow, Scotland, and I am a member of PAPTAC, TAPPI and the

AWWA. I have also been associated with such companies as Weir,

BW/IP, Bingham and Chesterton.

In other words, I’ve been around the block a few times, and I know what

works and what doesn’t work. Now I am taking this opportunity to share

this information with you. I hope you can put it to good use.



http://www.rossmackay.com/clients.php

http://www.rossmackay.com/training.php

http://www.practicalpumping.com/













http://www.rossmackay.com/clients.php






Mistake #1 - Buying the Cheapest Pump

Your Get What You Pay For.....!

While most of us are likely to have heard that before, many of us have

actually discovered the truth of it the hard way... by harsh experience.

Those who have been around the pump business for more than a couple

of years, have probably even witnessed it taking effect right before our

eyes.

The policy of always buying the cheapest product or service is one that

few of us practice in our private lives, yet it continues to be the single

biggest mistake made by end users of pumping equipment? Why?

I believe the problem is ignorance. Many people think that if all the

pumps meet the specification (assuming there is one!), then the cheapest

one is the best buy. But is that true?

The Specification

First of all, does the pump really meet the specification?

Real world experience will tell us that, when the specification isacknowledged at all by the supplier, it is usually in the form of a list of

qualifications and comments about various paragraphs within the body of

the specification. It is very rare for a supplier to commit to their offering

being in full compliance with all the requirements.





Is the specification complete and accurate?

An additional challenge is that the specification is either inappropriate or

incomplete. This is a more serious situation and happens more frequentlythan we would care to acknowledge. It does not always refer to any

vindictive misrepresentation or withholding of data (See Mistake #2), but

rather to the limitations of knowledge of the field conditions and the

understanding of how these conditions might impact the pump

performance and reliability.

All pump problems arise from either internal or external stresses. The

internal stresses mostly occur as a result of upset hydraulic conditions,which are rarely discussed in any specification, regardless of how

integral they are to the system in which the pump must operate. The

external stresses come from inappropriate installation or operation, and

they too are rarely acknowledged in the specification.

The problem is that the pump selected must be able to withstand these

(sometimes) unknown stresses. The cheaper pump generally will not.

Is the pump going to do what it’s been purchased for?

I am still astounded at the number of plant engineering and operating

personnel who labor under the delusion that a centrifugal pump should

produce 500 gallons per minute in the field, if its nameplate says that's

the condition for which it was purchased. Many readers will still wonder

what's wrong with that statement. This reveals a lack of realization that

the centrifugal pump is the slave to the system, and is clearly a symptom

of the inadequacy of on-the-job training. (See Mistake #5.)





We need to understand that pump suppliers do not guarantee field

performance. It is essential that we understand that the standard pump

manufacturer's guarantee covers defective material and workmanship of

parts of its own manufacture. They will also agree to meet (within certain

tolerances and under factory test conditions) all specified conditions of

Head, Capacity, NPSH and, sometimes, Vibration, with the stated levels

of Efficiency and Power Draw offered.

In the event that the field performance is not acceptable, the first reaction

is to take the pump back to the factory and test it under controlled

conditions. This is quite understandable and justified, as the supplier has

no control over the installation and operating conditions in the field.

Consequently, field performance is rarely, if ever, guaranteed.

The Price Negotiation

Traditional pricing negotiation frequently shows up in the guise of “Your

price is too high!” which instantly takes the emphasis away from the need

to buy the best value, and not the lowest price. Many salespeople have

not yet realized that this statement is simply a set piece in the informalscript of the negotiation process, which has become part of the pump

purchasing scenario over the years. Any purchasing agent worth their salt

will use that phrase at some time during negotiations, regardless of the

specific numbers in front of them.

Unfortunately, this problem is aggravated by the fact that many of those

who purchase pumps don’t know how to evaluate one pump bid against

another on anything other than a subjective basis. Consequently, the low price policy continues to rule.

The sad part is that, over the years, this strategy has resulted in the

elimination of the availability of some good quality products in certain





markets. This, in turn, leaves those industries with inappropriate and

usually inefficient equipment with which to transfer and process the

liquids needed in their operation.

The long-term consequence of this scenario usually finds these same end

users negotiating low bids on the prices of the over abundance of spare

parts they need to keep their pumps operational. Many of which are now

supplied by third party organizations that, in turn, can take no

responsibility for any changes in hydraulic operation of the pumps for

which they provide the parts.

The Consequences

The trouble is that, when we buy the cheapest pump, it almost always is

less efficient, breaks down more easily and frequently, and often doesn’t

even do the job that was anticipated.

This results in more power draw, which increases the cost of running the

pump. More frequent breakdowns increase the cost of spares and

expended manpower as well as a reduction in availability and production.

The Correction

Value Based Purchasing helps us buy the pumps that are the best

available in the market, and the ones most suited to the operation forwhich they are being purchased.

This involves a detailed evaluation and comparison of pump quotes, and

will always require some degree of subjective evaluation about the





accuracy of the data presented. In this area, some previous experience

with pumps and potential suppliers will be invaluable. However, the

overall consideration must continue to be the best long-term value for the

money.

To do that, we must consider specific aspects of the equipment being

purchased, including:

1. Hydraulic suitability to the service.

2. Efficiency of operation.

3. Mechanical suitability to the service.

The better companies already include some type of evaluation for the

first two factors in their considerations. The only comment that can be

made would be in relation to the hydraulic suitability of the pump for theservice. This can only be established if all the extremes of operation are

considered, and not just the 'normal' conditions.

With respect to efficiency of operation, an evaluation of power cost is

fairly standard, and is based on the particular cost of usable power in that

plant. To ensure a real appreciation of the value of an efficient pump, it is

strongly recommended that the actual power consumption cost for each

pump under consideration be calculated. Do not be tempted into onlycalculating the difference in efficiency quoted, as it tends to give a false

impression.





It is also recommended that cost considerations for various system setups

be considered, as well as the various mechanical options within the pump

itself. These form part of our System Design and Pump Selection training

program identified on our web site www.practicalpumping.com

Consequently, as we don’t buy the "cheapest" of anything else, let’s start

working with a value based approach to pump purchasing, and stop

committing the First Costly Mistake by simply buying the cheapest

pumps.

We can offer you some assistance with this mistake in our one day school

on System Design and Pump Selection which uses, as a text, our book“The Practical Pumping Handbook”.













Mistake #2 – Providing Incomplete

Information to Suppliers

Frequently, when a pump is being selected, it is known that it will have to

operate at more than one single condition. Sadly, this information is not

always transmitted to the supplier, and the Engineer will decide for which

application the pump will be sized. It is not uncommon for that decision

to be made based on what is considered to be the Worst Condition. The

thought process being that, “if it can handle the worst condition, it should

be able to handle all the others”. Sadly, such is not always the case. In

face, it is more frequently true that, when the pump is selected for the

Worst Condition, then that worst condition becomes the Best Condition,simply by virtue of the fact that it is the duty for which the pump has

been selected.

Transfer System

The classic example of such a situation is in a batch transfer system,

where the Total Head is constantly adjusting as a result of the change in

tank levels throughout the batch. In spite of this, the supplier is given

misleading information by being supplied with only one Head-Capacity

condition. This effectively creates a reduction in the liquid level in that

tank and the equivalent increase in the static head that the pump must

overcome.





Figure 2 - 1 Typical System Diagram

When this happens, the System Curve will move straight up on the graph,

with the following three specific conditions occurring during a single batch.

At the Startup point, the level of liquid in the supply tank will be at it's

highest, while the level in the discharge tank could be zero. This will

translate into a low value of Static Head (Curve a).

At the Intermediate point, the level of liquid in the supply tank will have

dropped, and the level in the discharge tank will be greater. This will

result in a higher value of Static Head (Curve b).





At the Shutdown point, the liquid in the supply tank will have been

transferred entirely into the discharge tank, resulting in the maximum

value of Static Head (Curve c). At this point, the pump should be shut

down.

Figure 2 - 2 Varying System Curves

The system curve will assume the three positions shown in Figure 2-2 as

it moves steadily from Startup (a) to Shutdown (c) with the

corresponding change in pump capacity. However, as the system

approaches the Shutdown point, the pump performance will become

unstable, thus resulting in low reliability and high maintenance costs.

However, had the complete system information been provided to the

Supplier, an alternative selection could have been made which would





place the BEP midway between the Startup and Shutdown condition, thus

providing stable operation from start to finish.

Pressurized System

In a pressurized type of system, such as a boiler feed system, the feed

pump takes it’s suction from a deaerator under vacuum and supplies a

boiler under pressure. In this system, the Differential Pressure is not a

function of the flow rate and will have similar consequences as the Static

Head change in the previous example. Any change in pressure in either

the deaerator or the boiler, will also cause the system curve to move up or

down as indicated in Figure 2-2.

Closed Loop System

A closed loop system is one in which the entire system is pressurized by

the pump. To achieve this, the pumpage is fully contained within a series

of pipes and pressurized process equipment all the way from the pump

discharge, through the system, and back to the pump inlet. In such a

layout, the Static Head in the system is effectively zero, and the pumping

conditions are usually controlled for the flow rate.

System Controls

A change in Friction Loss can be caused by a variety of conditions suchas manual operation or automated controls opening and closing a

different valving system. This will result in the System Curve adopting a

different slope that will pivot about it's point of origin at zero capacity.





Figure 2 - 3 Friction Changes in a System

Restrictions in Piping

The same effect can also be realized when the bore of the pipe in the

discharge side of the pump reduces in size owing to some kind of buildup

such as scaling, etc. Such a buildup may also occur inside process

equipment such as filters or heat exchangers. These build-ups

automatically reduce the bore of the pipe and therefore increase the

Friction Losses in that pipe.

Consider the difference in effect between throttling a valve and having

scale build up in the pipe. The former will have an immediate effect,

while the scale build-up can frequently take years to show some effect.





Consequently, when we are selecting a pump for a particular service, it is

important to be aware of all the ramifications of that service before

deciding on which pump to use. Frequently, the basic operating data is

insufficient for an optimum selection. Knowledge of any extreme or

upset conditions must be made available to the supplier in order that they

can be considered.

Operational Extremes

Some considerable time ago, I was involved with an operation where a

slow closing valve was designed into the system, but was frequently

overridden by a check valve that was slammed shut manually. This madea huge difference to the system and it’s operation.

Under the design operation, the pump was brought gently to a shutoff

operation condition prior to being switched off. This permitted the

selection of an ANSI pump that was capable of handling the entire range

of Head-Capacity conditions in a smooth manner well within it’s pressure

design limitations.

However, when the check valve was slammed shut, it created an

extremely high shock loading on the pump that exceeded the pressure

capability of the ANSI pump and caused a fracture of the pump casing

with the potential for explosion of the product being pumped.

As a result of the full understanding of what can frequently happen in this

application, the pumps now used are designed in accordance with API

610 specification and are capable of handling twice the operating

pressure of the ANSI design.





In this case, knowledge of the worst condition was essential in view of

the fact that it represented a single shock loading problem that could not

be avoided. Without that information an incorrect pump would be

selected with a dangerous result.

Correction

Ensure that the pump supplier is provided with as much information as is

available to the system designer, with input from the operations group.

Discussions on a variety of this type of situation are available in the

various articles listed on our www.practicalpumping.com web site. This

is also typical of the information shared in our E-mail Newsletter, “The Pumpline”, which supplies Tips and Techniques on Pump Reliability at

monthly intervals. Free registration is available for The Pumpline on the

web site.

http://www.rossmackay.com/pumpline.php










Mistake 3 – Leaving the Choice of

Seal to the Pump

Supplier

One of the most important things to remember about mechanical seals is

that they are purchased by two different groups. While they both share a

desire to ensure that the seal "works", the two groups have different

priorities when selecting a seal.

The end user generally considers a variety of benefits such as reliability,

ease of installation, availability, flexibility, and other factors important to

the reliable and long term operation of the whole plant.

On the other hand, the majority of pumps are purchased on the basis of

"low bid" (see Mistake #1) and the pump supplier is constrained by that

short term budget. Consequently, most mechanical seals are also

purchased on the basis of price. Therefore, the considerations of

reliability, ease of installation, availability, flexibility and all the other

factors vital to the long term operation of the plant, are ignored.

It must be recognized that, just because they look the same and fit the

same, not all seals perform the same. Seals that are manufactured with

poor quality materials may cost less initially, but are likely to result in

additional cost, lost time, and a low level of reliability for the pump and

system.

To avoid this, the end user (by necessity) must become a mechanical seal

expert and know which seal is needed for the particular application. It

also requires knowledge of the important aspects of mechanical seals and

their operation as part of the pump. With this information, the end user

can specify the seal needed in the pump being purchased.





It should be noted that this is not a new concept as most plants operating

with a high level of reliability are already doing this with considerable

success.

A number of difference areas of the seal need to be considered.

The Seal Faces

For many years, the most popular combination of seal face material wasthe carbon rotating face running on a ceramic stationary. These are still in

popular use, and have been augmented by stainless steel, tungsten carbide

and silicon carbide. It is vital that the correct material is selected to guard

against the problems of the particular liquid being pumped

As the seal faces are machined to a high degree of flatness accuracy, very

careful handling of these faces is essential during installation. The seal

manufacturers’ installation instructions must also be carefully followed toensure that the seal faces are suitably protected and precisely located.

Seal Flexibility Options

Any axial or radial movement of the shaft, will require some flexibility

from the spring(s) in order to keep the faces closed. This flexibilityhowever can only be carried to a certain degree, and the mechanical

condition of the pump plays an important role in the reliability of the

seal.





This seal flexibility is usually supplied by a single large spring, a series

of small springs, or a bellows arrangement. The decision of which to use

is important and depends on the particular application being considered

and the type of product being pumped.

Figure 3- 1 Seal Flexibility Options

In traditional seal designs the springs were applied to the rotating face,

but more recent designs apply the springs or bellows to the stationary

face of the seal. In fact, it is now quite common to find both stationary

and rotating faces of a mechanical seal having some kind of flexible

mounting arrangement.

Although the main closing force is normally provided by the pressure in

the stuffing box, the springs and bellows compensate for any shaft

movement and keep the seal faces closed during startup and shutdown of

the pump. The strength of this closing force is also a factor in the overall

reliability of the equipment.

Fretting or Non-Fretting Seal.

A pump shaft will undergo both radial and axial movement for a variety

of reasons, including bearing tolerances, end play, vibration and shaft

deflection. To keep the seal faces together, the springs are constantly

adjusting the seal to compensate for that moving shaft.





When an elastomer is used between the rotating face and the shaft under

these conditions, the elastomer moves back and forth on the shaft. This

eventually creates a groove at that point on the shaft. The groove causes

leakage and necessitates repetitive repair or replacement of the shaft.

While the shaft can continue to be protected by means of a shaft sleeve,

the only real lasting solution to that kind of fretting is by eliminating that

dynamic seal. Most major seal manufacturers now produce "non-fretting"

seals which protect the pump parts from fretting corrosion.

Balanced or Unbalanced Seals

An Unbalanced Seal exposes the full cross-sectional area of the rear of

the rotating face to the stuffing box pressure and creates a relatively high

closing force between the seal faces. Balancing a mechanical seal reduces

the closing force which tends to lower wear rate and the temperature

buildup, thus extending the life of the seal.

While the balanced seal may appear to be the answer to all sealing

problems, certain services may be better served with the unbalanced seal,

depending on the need. For example, some light slurry applications may

need the additional security of the higher closing force at the seal faces.

This again highlights the importance of knowing which seal is needed in

any particular service.

Regardless of any other consideration, a balanced seal is usually

recommended when the stuffing box pressure exceeds 50 p.s.i.





Inside or Outside Seals

The more popular arrangement positions the seal inside the stuffing box.

Although this requires disassembly of the pump wet end to carry out anymaintenance on the seal, the main advantage is that it is possible to

control the seal environment inside the stuffing box.

An Outside Seal reverses the orientation of the stationary face and locates

the rotating unit on the shaft between the stuffing box gland and the

bearing. This simplifies installation and saves maintenance man-hours.

However, if control of the seal environment is essential to the reliability

of the equipment, then an outside seal is not usually a practical option.

Figure 3 - 2 Split Seal





An important addition to the Outside Seal in recent years is the Split Seal

that eliminates the need to dismantle the pump every time the seal needs

to be changed. This option is also subject to question if there is limited

knowledge of seals in the plant. As it is so easy to replace, there can be a

tendency to change the seal without conducting any in-depth

troubleshooting of the seal failure. Consequently, the same root cause

that created the seal failure in the first place, could easily be reinstalled.

Component or Cartridge Seals

A component seal is one where each part of the seal must be assembled

on the pump individually. This requires considerable skill and significanttime investment on behalf of the maintenance personnel.

The cartridge seal is a completely self-contained assembly that includes

all the components of the seal, the gland and the sleeve in one unit. As it

does not require any critical installation measurements, it simplifies the

seal installation procedures while simultaneously protecting the faces

from accidental damage. It also effectively reduces the time spent on

maintenance by simplifying seal installation and change-out procedures.

However, a similar situation can be created as discussed above with the

split seal. As it too is relatively easy to replace, there can be a tendency to

change the seal without conducting any in-depth troubleshooting of the

seal failure.





Figure 3 - 3 Cartridge Seal

Single or Double Seals

A Double Seal is used instead of a Single Seal when a high degree of

leakage protection is desired. It comprises two sets of seal faces

combining to increase the security of the environment from the pumpage.

They are most frequently used for volatile, toxic, carcinogenic, hazardous

and poor lubricating liquids.





Every double seal requires a barrier fluid between the two sets of seal

faces and ensure that the outer set of faces receive some lubrication. The

recent introduction of Gas Seals uses an inert gas between the seal faces

which eliminates any possibility of product contamination.

Correction

When a mechanical seal is correctly installed and supported it can

provide extensive and reliable service. However, it does require accurate

selection, and most pump suppliers do not have the necessary incentive

or expertise to make such a selection. Although a reliable seal sales

person can often assist, it will usually be necessary for the end user to become their own in-house expert in mechanical seals.

We can offer you some assistance with this mistake in our one day Pump

Troubleshooting school which comprises the second day of our Mackay

Pump School. Much of that information can also be found in our book

“The Practical Pumping Handbook ”.









Mistake #4 – Poor Installation Practices

Correct and complete installation practices can mean the difference between a unit that gives many years of trouble-free service and one that

requires constant and repetitive maintenance. It should therefore be

everyone’s concern that the pump should be mounted on a strong

baseplate supported by a strong concrete foundation. It must also be

properly connected to the system by means of accurate alignment to the

piping system as well as to the driving motor.

Three particular areas must be satisfied to ensure that the pump will provide long and reliable operation within the system.

The Foundation and Base

The concrete foundation must be properly designed with the best of

material and sufficiently substantial to absorb any vibration, thereby

forming a permanent rigid support for the baseplate. A rule of thumb that

is frequently used is that the foundation should be about 5 times the

weight of the pump/motor assembly, and approximately 6 inches longer

and wider than the baseplate.

The baseplate should be supported on leveling screws, shims or on metal

wedges with a small taper located close to the foundation bolts. All

leveling screws and other areas requiring protection from grout spatter,

should then be covered with a wax to prevent the grout from adhering to

them.





The machined mounting surfaces on the baseplate should be checked to

within 0.002 inches per foot by adjusting the leveling devices and using a

precision level. Ensure the machined mounting surfaces of the baseplate

are horizontal, flat and parallel. To prevent stress and distortion of theequipment, all surfaces in the same plane must be within 0.002 inches

overall.

When the baseplate is level, check that all support wedges or shims are in

full contact with the foundation and baseplate. Tighten the foundation

anchor bolts evenly and double-check the level.

The temperature of the baseplate, grout and foundation should be kept

between 40 and 90 degs. F. during grouting and for a period of at least 24

hours afterwards. Follow the grout supplier’s instructions in detail and

ensure that the placement of the grout is done quickly and continuously

to prevent cold joints and voids under the baseplate. The grout should

then be allowed to harden in accordance with the manufacturer’s

instructions.

Piping Arrangements

Without any doubt, this is the single most abused area of pump

installation, in fact it can it can be stated unequivocally that most pumps

are piped up incorrectly. When we look at the way many pumps have

been installed, it resembles a “plumbers nightmare”. They look as if

they’ve been squeezed into a corner out of the way, and the pipesthreaded in and out, without any consideration for fluid flow patterns.

The blame for this must be laid squarely at the feet of the pump supplier!

After all, if you were installing a new pump in a new system, where





would you go for information on how the pump piping should be

arranged?

Most of us would refer to the pump’s Installation, Operation and Maintenance (IOM) Manual supplied by the pump manufacturer.

Unfortunately, that won’t provide a lot of information, as most of the

pump companies once subscribed to an attitude of limiting their

responsibility within the confines of the suction and discharge nozzles of

the pump. Although this attitude is fast disappearing, the change has not

yet reached most of the IOM Manuals. As a consequence, accurate and

complete information is still severely limited, and a high proportion of

the pumps in most industries are installed with inappropriate piping

arrangements that result in premature failure.

The major problem with this condition is that it positions the root cause

of the pump failure outside the physical confines of the pump itself, thus

making it difficult to source for the unwary and inexperienced.

Piping design is one area where the basic principles involved are

frequently ignored, resulting in problems such as hydraulic instabilities inthe impeller, which translate into additional shaft loading, higher

vibration levels and premature failure of the seal or bearings. As there are

many other reasons why pumps could vibrate, and why seals and

bearings fail, the trouble is rarely traced to incorrect piping.

It has been argued that because many pumps are piped incorrectly, yet are

operating quite satisfactorily, piping procedure is not important. That

doesn’t make a questionable piping practice correct, it merely makes itlucky.

Even when the design is correct, the practice of using “come-alongs” and

other external forces to bring misaligned piping into position on the





pump flanges will cause internal stress within the pump casing that will

result in premature failure.

Any piping mistakes that are made on the discharge side of a pump,frequently can be accommodated by increasing the performance of that

pump. Problems on the suction side however, can be the source of

repetitive failures, which may never be traced back to that area and could

continue undetected for many years to come.

Our 5 Rules of Pump Piping are as follows:

1. Provide the suction side with a straight run of pipe, in a length

equivalent to 5 to 10 times the diameter of that pipe, between the

suction reducer and the first obstruction in the line

2. The pipe diameter on both the inlet and the outlet sides of the

pump should be at least one size larger than the nozzle itself.

3. Eliminate elbows mounted on the inlet nozzle of the pump.

4. Eliminate the potential for vortices or air entrainment in the suction

source.

5. Arrange the piping in such a way that there is no strain imposed on

the pump casing.

Further details on these Rules can be found in the Articles section of our

web site.

http://www.rossmackay.com/articles.php

http://www.rossmackay.com/articles.php





Alignment

Industry has progressed well beyond any discussion of the statement that

good alignment is essential to safe and trouble-free operation of rotating

equipment. The only questions that still remain in some areas are; “what

is alignment?”, and, “what is good alignment?”.

When we discuss “Alignment” in the pump industry, we are usually

discussing either “Piping Alignment” or “Shaft Alignment”. It must be

noted that the term “Coupling Alignment” is a misnomer. We are not

concerned about bringing the coupling halves into alignment. We are

only interested in ensuring the shafts of the pump and it’s driver will

rotate on a common axis. If the shafts are not coaxial, the resulting

moments will increase the forces on the pump shaft and bearings, causingaccelerated wear and premature failure.

Alignment occurs when two lines that are superimposed on each other,

form a single line. Misalignment is a measure of how far apart the two

lines are from forming that single line. The two lines we are concerned

with here are the centerlines of the pump shaft and the driver shaft. In

one condition, the two lines can be parallel with each other, but at a

constant distance apart. This is referred to as Offset or ParallelMisalignment. In the other, one line will be at an angle to the other, and

is referred to as Angular Misalignment.

Parallel misalignment can be considered as the distance between the

driver shaft centerline and the pump shaft centerline at any given point

along the length, and this misalignment can happen in any plane.

Consequently, it is worthwhile to take the necessary measurements on the

top and on the bottom for vertical offset and also on each side for thehorizontal offset.

Angular misalignment refers to the difference in slope of the two shafts.

If the pump, base and foundation have been properly installed, the shaft





centerline of the pump can be considered as level and therefore, as the

reference or datum line.

Figure 4 - 1 Shaft Offset and Angular Misalignment

The slope of the driver shaft can be calculated by determining the offset

measurement at two different points, subtracting one from the other, and

then dividing the result by the axial distance between the two points. This

misalignment should be measured and calculated in both the vertical and

horizontal plane.





Correction

Ensure that a strong rigid baseplate is properly grouted into place

(following all grout manufacturer’s instructions) onto a properly designed

foundation that is sufficiently substantial to absorb any vibration, thereby

forming a permanent rigid support for the baseplate.

Any piping mistakes that are made on the discharge side of a pump, can

frequently be accommodated by increasing the performance of that

pump. Problems on the suction side however, can be the source of

repetitive failures, which may never be traced back to that area and could

continue undetected for many years to come.

When it comes to acceptable shaft alignment tolerances, these depend to

a large extent on the level of pump reliability that is expected by the

pump user. Consequently, every end user should develop their own

acceptance levels that provide their desired outcomes.

The tolerances shown in The Practical Pumping Handbook are offered as

guidelines only, but they can be used as a starting point for developingtolerances that will be specific to each individual company or equipment.







Mistake #5 – Lack of the Appropriate

Training

One of the major problems facing industry today is the limited number of

people who have sufficient skill and experience to diagnose and rectify

the basic problems plaguing centrifugal pumps. The other major

difficulty is that the same lack of skill and experience is creating many of

these problems in the first place.

A detailed evaluation of a pump problem requires a depth of knowledge

which usually surpasses that to which most people are ever exposed. Forexample, most pump engineers, operators and maintenance people

develop their knowledge base from the same “school of hard knocks”.

While this on-the-job type of training has much to commend it, it does

expose the pupil to the opportunity of learning other people’s mistakes

and misconceptions. At best, it only teaches what is necessary to execute

a particular job function in exactly the same manner as it was previously

performed - good or bad!

A purchasing manager may be faced with the responsibility of buying

equipment within a capital cost budget which has no mechanism for the

evaluation of long term operation and maintenance costs. Consequently

the “most economical” pump purchased may result in frequent and

repetitive failures which could quickly exceed the initial cost difference

and even the total price of the pump itself. (See Mistake #1.)

A system engineer may have learned how to size a pump based on theoperating parameters of the system. However, if that pump is unable to

withstand the effects of certain installation or operating anomalies which





may occur in that plant, the reliable life of the pump could be

detrimentally affected. (See Mistake #2.)

Operations personnel are often required to “tune” the system to providethe desired output of product. As a consequence, they may be faced with

the necessity of throttling back the pump discharge valve, and that can

result in a variety of hydraulic and mechanical problems in the pump.

(This mistake didn’t even make it into the top 5!)

The ramifications of all such situations are generally imposed on the

maintenance department. Unfortunately, the training in that group has

traditionally been limited to the physical change-out of the parts when a breakdown occurs. As the underlying cause of pump failure often extends

well beyond the failed item, these maintenance methods will effectively

reinstall the same old problem.

This is particularly concerning when we realize that over 80% of all

pump failures tend to manifest themselves at the mechanical seal or the

bearings, which then act in a manner similar to a fuse in an electrical

system

Just because the fuse fails, doesn’t mean there is anything wrong with the

fuse! In fact we understand that the problem is almost always somewhere

else in the system.

In spite of this, when a seal or bearing fails, we rarely look for the real

problem but simply replace the offending part. While that will

occasionally solve the problem, the simple change-out of a seal or

bearing rarely provides long-lasting relief from the problem. So let’s

consider a few relevant factors.





Failure Analysis

As there are only a few symptoms with which to recognize a troubled

pump, the key to failure analysis lies in understanding how thecombinations of symptoms identify the underlying cause of the problem.

An effective troubleshooting tool will always begin with the question,

“How fast did it show up?”. If the problem has suddenly appeared, it is

likely to have a different cause than a similar problem that has been

developing slowly. It is also fairly obvious that a sudden appearance of

the problem is probably caused by a sudden change in the condition to

create the problem. Therefore it is highly unlikely that such a problemcan be attributed to normal wear and tear. It is much more probable that

an inappropriate action has taken place recently.

The exception to that concept is where wear gradually takes place until

the point at which failure suddenly occurs. In such an event however, the

wear is usually indicated by a gradual reduction in performance until the

breaking point is reached; thus providing some prior notification of

imminent failure.

Operational Problems

This is the type of problem where the pump simply doesn’t produce the

hydraulic results for which it was intended. A typical example of this

occurs when the centrifugal pump isn’t pumping enough liquid through

the system. While this is often blamed on an inadequate pump, it is more

often the fault of a system head that is higher than was expected.





Another example is when the pump is operated so far away from its

design point that it begins to vibrate as a result of a variety of hydraulic

conditions that may occur.

Reliability Problems

These problems bring into question the length of time the pump can be

expected to continue running. A typical example is when a pump is

vibrating as a result of a variety of mechanical conditions that can occur

from a wide variety of problems.

Although there have been almost 100 different problems associated with

centrifugal pumps, many of which have more than one, two, three, or

even more solutions, it’s interesting to note that the total number of

solutions is less than 40. In fact, when these are carefully considered, it is

evident that there are only really 6 basic solutions to every pump

problem.

• Better Sealing Devices

• Component Modification

• Upgraded Materials

• System Change

• New Pump

• Personnel Training





Of these 6, the most significant will continue to be that of Personnel

Training, where everyone who has anything to do with the sizing,

selection, installation, operation and maintenance of the pump, is fully

skilled and experienced in their own particular function, as well as how

their actions impact the reliability of the pumping system.

Aging Problems

No.... not the pumps, the people! A few years ago at the TAPPI

Conference (Technical Association of Pulp and Paper Industries), it was

identified that, by the year 2006, over 65% of the maintenance labor

force in the Pulp and Paper Industry will have reached retirement age.This created considerable concern in an industry where, like many others,

little attention has been paid to apprenticeship training programs. As a

consequence, there is a real danger of entire mills losing the vast majority

of their maintenance expertise in a very short period of time.

Since that TAPPI Conference, I have discussed this personnel situation

with a number of clients in other industries and have seen the realization

set in that they too are facing a very similar problem in their facility.Consequently, effective and appropriate training will become an ever

greater need in the coming years.

Inappropriate Training

Most companies spend a vast amount of their training budget teaching

their maintenance crews how to dismantle and reassemble their pumps,

when the money would be much better spent on teaching them how to

stop the pumps failing in the first place.





The truth is that most of these maintenance people are really good at

dismantling and reassembling pumping equipment because they’ve been

getting lots of practice at it. What is really needed in these instances is to

teach the people who are around the pumps most of the time how to stop

them failing, and what kind of things they should be watching for and

how to tell if a pump is in trouble.

In other words, start using one of the most neglected tools for pump

reliability in every plant..... the operators.

Operators are the first line of defence for any company against repetitive

equipment failure. They are on the spot all the time and, when properlytrained, they can operate the pump properly and can identify and report

any potential for danger. A skilled operator can perform inspections and

conduct minor maintenance tasks that will lower maintenance costs and

increase pumping reliability.

Every time I train people in a company that has a high level of pump

reliability and where productivity and profitability is very high, I find

myself working with a multi-disciplined group of engineers, operatorsand maintenance people, instead of just the maintenance guys.

Correction

To bring your plant to the highest levels of pump reliability, productivity

and profitability, start creating reliability teams within your plant and

train every single member, regardless of whether or not they think they

need it.





These teams should include everybody involved in running the pumping

processes in addition to those who designed the system and purchased the

equipment as well as those who maintain it on an ongoing basis.

For those who can acknowledge they could do with a little help, check

out our unique “Pump Reliability Audit ” at our website and review the

various training programs. These are available to be conducted at your

plant and focused on your specific equipment and problem areas.

http://www.rossmackay.com/audit.php









Conclusion

These are the 5 costly mistakes again:

Mistake #1 Buying the cheapest pump.

M istake #2 Providing incomplete information to suppli ers.

M istake #3 Leaving the choice of seal to the pump suppl ier .

M istake #4 Poor pump installation.

M istake #5 Lack of appropriate training.

Now it’s up to you!

I hope you’ve learned something from the e-book. But more importantly,

I’d like it to spur you into action - because what matters is not knowledge

itself, but whether or not knowledge is applied.

If you read this e-book and do nothing, that’s just as bad as not having

read it at all. In fact, it’s worse, because you’ve wasted your time. Also,

the next time you make the same mistake, you will know it’s a mistake,

but do it anyway.

So please take action, and start now.

I would also suggest that you sign up for my FREE e-mail Newsletter,

“The Pumpline” that will bring you monthly Tips and Techniques on

Pump Reliability.







Free Electronic Redistribution Rights

Another action you can take is to send this e-book to anyone else youthink may be interested.

I believe this e-book contains extremely important information that most

people don’t have, but need. So I’m giving you free electronic

redistribution rights to send it to anyone else you choose.

This means that you can give it away to other people. You can send it toyour associates in other branches or departments of your company. You

can even send it to your suppliers or customers.

The only restriction is that you must not change it in any way. That

means you must send it in its original PDF format and in it’s entirety.





How we have helped others.

Here are some of the things that people say aboutThe Mackay Pump School.

“Outstanding! The information was well presented. Very useful data.

Enriching.”

Marvin Williams, Training Specialist, PCS Nitrogen

“An information-packed class that should be required train ing for

maintenance personnel and engineers in all industries.”

Darren C. Bittick, Reliability Engineer, International Paper

“A wealth of practical in formation.”

John Ruttle, Plant Engineer, Husky Energy

“Great! I t’ s good to hear fr om an expert who doesn’ t talk over your

head! – Knowledge you can use! ”

Donnie Shreve, Maintenance, Paducah-McCracken JSA

“A weeks worth of information in onl y two well spent days.”

Bryan Monich, Process Design Engineer, Labatt Breweries









Also a few comments about

“The Practical Pumping Handbook ”.

“Th is is an excellent and concise reference. Anyone responsible for

pumping equipment should have a copy handy.”

Kevin Delaney, President, Kevin Delaney-MS, LLC

" The real value of th is book i s how easy it i s to read and understand. I

have bought several copies for our Technicians in the mill ."

David Djuric, Business Unit Leader, Alberta Pacific










How may we help you?

The most effective way of my assisting you is by my conducting aMackay Pump School exclusively for your own people in your plant

and focused on your pumps. We customize this school by means of our

exclusive Pump Reli abil ity Audi t . Depending on your company’s level

of commitment to pumping reliability and your specific need, the school

can involve any number of these one-day programs.

Pump and System Reliability

Pump Troubleshooting

Pump Operators School

System Design and Pump Selection

Accountability Session (a follow-up course)

These programs also include a copy of The Practical Pumping Handbook

and/or an interactive program workbook. They also include the use of the

Video Series, “A Practical Approach to Pumping ” which can also be purchased individually or as part of a self-training module. In addition to

the Videos, two books are also available from our website

www.practicalpumping.com where you can also sign up for our free

eNewsletter, “The Pumpline” . This provides you monthly tips and

techniques on pump reliability.

“12 Steps to Mechanical Seal Reliabil ity in Centri fugal Pumps”

“The Practical Pumping H andbook”

We would welcome the opportunity to work with you and help you

increase pump reliability and stop pump failure in your plant.










http://www.rossmackay.com/books.php






















Contact Us

By Mail: Ross Mackay Associates Ltd.

4 Simmons CrescentAurora, Ontario

Canada L4G 6B4

Ross Mackay Associates Ltd.

P.O. Box 670-PMB-29

Lewiston, NY

U.S.A. 14092

Email Ross Mackay

Fax 1-905-726-2420

Tel: 1-905-726-9587

within the U.S. and Canada 1-800-465-6260

mailto:[email protected]

mailto:[email protected]

Documents

the 5 mistakes on pump.pdf