Piping, Systems, and Project Design: Codes, Standards, and Specifications!

One third of global electricity consumption is by industrial electric motors. I just heard this statistic on a recent Pumps & Systems podcast and went in search of verification for it. Holy moly. It turns out that’s true! It’s one of these points that an up until recently outsider like myself may well have never known. How are they and other process instrumentation regulated and why does it matter? It’s important to keep asking the relevant questions and looking for answers, so let’s do it.

Piping, pumps, motors and other equipment have a critical role in global safety, security, and standards of living. This equipment is designed in adherence to rules established by standards organizations, government agencies, and trade association standards. Engineers can also employ their own project-specific specifications. This matters because when a project calls for instrumentation, it’s mandatory to know what the applicable standards are that apply to an informed project design. And there are caveats to be mindful of in this process.

In the interest of saving time, engineers will sometimes recycle codes, standards and specifications from past projects onto a new project. Brian Silowash, author of Piping Systems Manual, has seen this firsthand. It can be problematic if any regulations specified are out of date. Apart from recycled codes, projects tend to have multiple revisions. The danger in printing projects on paper is that various parties may not have the same revisions in hand. A Building Information Modeling (BIM) program can solve that problem by storing project revisions to the internet cloud, allowing all parties associated with projects access to the same revisions.

Though some effort has been made through the years to unify codes and standards, there are still many to sort through by relevant issuing associations. The first photo below shows standards issuing trade associations. My reference text shows eighteen of these associations, though there may be more nationally and internationally. 


This next photo shows one page of individual standards, their issuing organizations, ID numbers and titles pertaining to valves and fittings. We should be mindful that every project is subject to a number of codes, specifications, and standards. 

Codes, standards, and specifications are typically identified like this:


ACRO is the organization that developed the code, standard or specification

SPEC is an alphanumeric identifier

YR is the year of the latest revision 


I recently came out of a piping and instrumentation diagram seminar session where a wastewater department standard drawing references legends, symbols and abbreviations. The photo below depicts engineer specified project specific instrument letter identification, symbol configuration, and instrument or function symbols.


While instrumentation and projects are subject to codes, standards, and specifications from many sources and there are pitfalls to avoid, the good news is that these are categorized for searches. Take care to ensure that any recycled codes are current. And save time for all parties affiliated with the project by use of a BIM cloud storage application.

Best regards and thank you for reading.

Jennifer Zadka


Sources: Piping Systems Manual by Brian Silowash

On the Job Site: Construction course by Jim Rogers

Affinity Laws in Practice

Merriam Webster defines affinity as: “a likeness based on relationship or causal connection.”  The Affinity Laws are a heuristic governing pump sizing for one pump based on known constants for another of that same pump. Knowing of these laws helps, but really understanding to apply them in problem solving goes a long way. I’ve been holding off on writing this because the topic is one I had been struggling with. It’s important to know, so it’s worth the struggle.

I once had someone tell me, “I’m not paying you to learn all of this theory!” That’s fair enough, but know that the trade-off is between a culture of striving for a good enough versus one that’s striving for excellence. Which standard would you rather hold? If we’re honest, we can’t have it both ways. For this, I challenge you. Be honest. Hold your torches high!

  • Pump performance involves relationships between performance [ie, head, shaft speed, volumetric flow rate] and power. If speed or impeller diameter are known with one pump, performance based on speed or impeller diameter change for a another of that same pump can be determined. Also, if these are known for just one pump with a VFD (variable frequency drive), which is a commonplace scenario, new H-Q (head-capacity relationship) and BHP (brake horsepower) curves with a different speed than published on a pump performance curve can be plotted.
  • There are two sets of Affinity Laws, and both are based on the premise of a pump’s specific speed not being changed once its been calculated. One law holds impeller diameter constant. The other holds speed constant.
  • What’s nice is that this can all be seen on a pump performance curve. These relationships are what we’re typically seeing most manufacturers including in their pump H-Q curves. The curve is designed to provide this information/knowledge as given information. What I’m writing about here is less about that knowledge, itself, and more about understanding relationships based on knowledge.
  • Though you could just see it all on the curve and not bother with knowing the why and how of it, don’t cheat. Learn how it all ties together foundationally. This is like the difference between seeing a movie in just two dimensions versus in all three (seeing versus “seeing”). Wouldn’t it be more far more entertaining to have it all come to life in vivid detail – not once, but every single time?
  • Here are the two sets of Affinity Laws presented in basic and practical terms:

Affinity Laws Set 1.

Holding the impeller diameter, D, constant, let’s solve for speed:

Q1/Q2 = N1/N2

  • Q is capacity (flow in GPM) and N is speed (motor speed). 1 is the first baseline pump; 2 is a second of that same pump with a capacity change having affinity in predicting second pump speed based on capacity change.

What that’s saying is this:

Q1(capacity of baseline pump 1)/Q2(capacity change for pump 2) = [N1(speed of baseline pump 1)/N2(speed change for pump 2)].

Visualizing this, I see two of the same exact pumps sitting side-by-side. Each has the same unchanged impeller size inside the respective volutes. But each pump calls for a different capacity (flow in GPM). How will the flow difference in that second pump change the required motor speed, since capacity and speed are related? We’re about to find out!

Let’s solve an iterative trial and error problem with these known terms, referencing this pump curve:


Using an example pump curve, what speed is required with a full diameter impeller to make this rating: 3000 gpm @ 225′? Here, I’m referencing an ITT Goulds Model 3196 centrifugal pump performance curve, 6 x 8 – 15 at 1780 RPM. (This model has a 6″ discharge, an 8″ suction, and a 15″ full impeller diameter). Let’s try out 2200 RPM to see if it gets to the desired rating:

Holding the impeller diameter, D, constant, let’s solve for speed:

Q1/Q2 = N1/N2

  • Q1 = 3000 GPM; H1 = 225 ft; N1 = 1780 RPM
  • Q2 = Q1 * (N2/N1); Q2 = 3000 * (1780/2200) = 2427 gpm
  • H2 = H1 * (N2/N1) squared; H2 = 225 (1780/2200) squared = 147′

This first test doesn’t work out. We’re trying for a motor speed to accommodate 3000 gpm given an untrimmed full 15″ impeller diameter. 2427 gpm isn’t a high enough flow for the full impeller to make sense on the example 1780 RPM pump curve. It’s below the 15″ full diameter curve line. Ditto for the 225 feet of head requirement. 147′ isn’t a high enough head for the full 15″ impeller size.

We tried a 2200 RPM motor speed for 3000 gpm @ 225′ and it didn’t work out. I’ll try again, this time @ 2000 RPM:

Holding the impeller diameter, D, constant, let’s try again to solve for motor speed:

Q1/Q2 = N1/N2

  • Q1 = 3000 GPM; H1 = 225 ft; N2 = 1780 RPM
  • Q2 = Q1 * (N2/N1); Q2 = 3000 * (1780/2000) = 2670 gpm
  • H2 = H1 * (N2/N1) squared; H2 = 225 * (1780/2000) squared = 178′

Referencing the performance curve published for this pump, 2670 gpm @ 178′ does fall on the curve line for the 15″ full size impeller. (It wasn’t slow enough of a speed to be above the line.) 2000 RPM speed is the test winner! Awesome.

Q1/Q2 = N1/N2

  • For this first set of Affinity Laws (that being the set with the impeller diameter held constant), it’s also true that:

H1/H2 = (N1/N2) squared

  • H1(ft/hd requirement for baseline pump 1)/H2(ft/hd change for pump 2) = [N1(speed of baseline pump 1)/N2(speed change for pump 2) squared].

BHP1/BHP2 = (D1/D2) cubed

  • BHP1(brake horsepower for baseline pump 1)/BHP2(brake horsepower change for pump 2) = [N1(speed of baseline pump 1)/N2(speed change for pump 2) cubed].

In summary, this first set of laws holds impeller diameter as constant. The second set of affinity laws is different. It holds speed constant in order to solve for impeller diameter trim.

Affinity Laws Set 2:

The speed is held constant. Let’s solve for impeller trim.

  • Flow in GPM is the same as shaft speed (1780 RPM, for example).
  • Head is shaft speed squared. (1780 * 1780 RPM).
  • Power (BHP) is the cube of shaft speed (1780 * 1780 * 1780 RPM).

Q1/Q2 = D1/D2

  • Q is capacity (flow in GPM) and D is impeller diameter (imp dia). 1 is the first baseline pump; 2 is a second of that same pump with an imp dia change having affinity in predicting second pump imp dia based on capacity change.

What that’s saying is this:

Q1(capacity of baseline pump 1)/Q2(capacity change for pump 2) = [D1 (imp dia of baseline pump 1)/D2(imp dia change for pump 2)].

Visualizing this scenario, I see two of the same exact pumps sitting side-by-side. Each runs on the same motor speed (1780 RPM, for example). But each pump calls for a different capacity (flow in GPM). How will the flow difference in that second pump change the impeller trim, since capacity and impeller diameter are related? Let’s do this!

In the second set of Affinity Laws (the set holding speed as the constant), it’s also true that:

  • H1/H2 = (D1/D2) squared
  • BHP1/BHP2 = (D1/D2) cubed

To summarize, the first set of Affinity Laws holds the impeller diameter as an unchanged constant in order to solve for motor speed required to accommodate a pump rating. In set one of the Affinity Laws, the problems can be solved by either changing capacity, feet of head, or brake horsepower to solve for speed. The second Affinity Laws set holds the speed constant in order to solve for impeller diameter trim. In set two, the problems can be solved by either changing capacity, feet of head, or brake horsepower to solve for impeller diameter trim.

To conclude, the Affinity Laws are a good rule of thumb, but can have up to a 15%-20% margin of error when solving for impeller trim. Slower motors tend to allow for greater impeller trim while following the Laws than higher specific speed motors. I personally find it interesting that capacity is equal to, while ft/head is squared and brake horsepower is cubed to solve for these variables. It’s so neat and tidy to have these variables line up for solving that way. I hope this information brings value to you. Please feel free to hold onto this for your next learning “curve” adventure!

With warm regards,

Jennifer Zadka

PS: Here’s my reference source: Pump Characteristics and Applications, 3rd Edition by Mike Volk.

The Power and Elegance of Circles

I’m a lifelong figure skating fan. If someone were to ask me why, the first thought that comes to mind is the power and elegance in it. There is a convergence of power, speed and grace, where these coincide to create the breathtakingly captivating experience we see on the ice. If you’ve ever watched a performance, you’ll quickly see that circular motions are what make the shows. What now? You’re not into figure skating, so you say? Try it, try it, and you may! In that case, let’s get on a race track and rev up your engines. If neither figure skating nor cars are gonna do it for you, so much more is governed by circular shapes that there aren’t enough hours in the day to cover it.

  • For those of us involved with water stewardship, circles are everywhere. They are in all places water transport and water treatment. I work in a pump shop. We call it rotary equipment. It’s only in these last few months that circles being in every facet of water stewardship has become a stark observation. It really came together for me in this last week, while I was taking a close look at pump stuffing box drawing. The diameter for gland, shaft, lock nuts, and bearings among other things, are all specified with diameter symbols throughout the page.
  • Some people have visions of sugar plums dancing in their heads. I was looking at the page, seeing nothing but diameter symbols everywhere because each of these components is circular. We wanted to know what it would take to possibly fit a cartridge type mechanical seal into the tight clearance, possibly boring through the box to accommodate a packing-to-seal conversion.
  • In tandem, I was overhearing an inquiry for a sump basin diameter. I walked out into our shop and looked at the wall of gaskets, baskets of o-rings, and shelves of couplings, pipes, fittings, impellers, and yes, at FRP basins being prepped for pump station installations. It was this unreal recognition. There are just circles, circles, and nothing but more circles all over the place. You have to leave the shop to get away from them, even for one moment! When calculating new installations and retrofits, this has implications for how it’s done.

If we know a diameter, calculating a circumference is straightforward. Here are some basic definitions:

  • Radius: A straight line extending from the center of a circle to one end of the circle (diameter / 2).
  • Diameter: A straight line across the center of a circle, from end-to-end (2 * radius, since a radius is half of a diameter).
  • Circumference: The linear distance around the circle. (2 * pi * radius), or (pi * diameter).
  • pi: A little over 3x the diameter of a circle. 3.14….

Why are there so many circles in the structures of water stewardship? It turns out that circles are the most efficient shape for handling pressure because pressure force is evenly distributed around a circumference. With other shapes, pressure forces concentrate at the corners, requiring expensive non-standard inefficient reinforcement. So, let’s say we have flow through a square. Is the velocity the same or is it slowed down? Well, if pressure is not evenly distributed, it can’t accelerate the same.

  • From the above example, we know that circumference is (2 * pi * radius). For circular motion, here’s how it’s determined:
  • Average speed = distance/time = (2 * pi * radius)/time. In other words, circumference is the distance we’re talking about here divided by time, which gives us the average speed.

I’ve been talking about circles in terms of their mechanics. Bacteria and other buildup such as scaling also love to hide in corners and crevices that come from shapes other than circular. This, too, means circles are a winning shape.

All of this had me curious about the larger picture above and beyond water. Circles are elegant and the most powerful of any shape to be found in the universe and beyond. They might be the shape of choice in water stewardship, but they didn’t start there. That shape is found everywhere in nature, and its use in water stewardship is simply a mirror to it. Everything from atoms to cells to the earth, planets, sun, moon, and even black holes are all circular shapes. It’s only fitting that the shape of the basic building block of life is also the best conductor to what flows through it.

That’s fascinating. And beautiful.

Ohm’s Law: Resistance, Conductance, and Application

“A professor who preached such heresies was unworthy to teach science.” This was the phrase used to describe Georg Ohm back in the day. Ohm was a German professor written off for his “web of naked fancies” by the German Minister of Education in 1825. Technology has come along a bit since then, but humans? Well, not quite as much. If you’re gonna hit someone up with an insult, try a little harder. Or at least have credibility beyond status quo bias as a basis for defense.

Now that the components of power and how they fit together have been covered, ohms as units of measurement for electrical resistance can be explained with a practical application example. Let’s say we have a handheld ohmmeter for motor insulation resistance (IR) testing, or what we in the pump and motor world call megger testing. We perform a field test to determine electrical current resistance in stator windings, which have an electromagnetic insulation varnish applied in manufacturing, in order to resist damage from the motor potentially overheating. The ohmmeter returns a value of 75 megohms of electrical resistance, or high current resistance. Is that good news or bad? Let’s have at this topic right now.

  • Ohm’s Law tells us there is voltage across two points, and that current in amperage is directly proportional to it. It’s expressed this way: I = V/R, where:
  • I is amps as current through the conductor (that conductor, or you can think of it as a passageway, is the motor stator windings in my example) = V, which is voltage across our conductor / R, meaning resistance of current in amps (how much resistance to current flow in amps are encountered across the stator diameter).
  • The freer the current flowing across the stator windings, the faster those windings can overheat and wear down their magnetic function in relation to the stator.
  • All kinds of other variables can also factor into insulation breakdown: excess moisture or humidity, corrosive vapors, hot, cold, vibration or mechanical damage.

We need that magnetic function to work in order to create rotating magnetic flux across poles. It’s not going to work if it’s worn down. That’s because flux creates a magnetic field in the air gap between the stator and the rotor. That, in turn, induces a voltage which produces current through the rotor bars. The rotating flux plus the current create the force for the torque needed to start the motor. When I read about and saw the insulation for myself, it was really confusing. Insulation for what? The insulation is to create a barrier to the free flow of electric charges. If windings sufficiently overheat, the insulation wears down, allowing for resistance to drop and the magnetic flux to lessen. That electric energy is transformed to the mechanical, or kinetic energy powering the motor shaft drive. That’s how this all fits together. There is more to this topic, but this is enough for now.

Now, back to the original question.

  • If we’re testing motor windings with a handheld ohmmeter that returns 75 megohms of resistance, is that a good thing?
  • It is, because the higher the resistance, the better shape that motor is in, where it will perform to its name plate rating while powering something that might have a critical requirement for power such as a pump.
  • If that ohmmeter returns a resistance of 10 megohms or lower, that means the DC current running the megger test is returning higher than acceptable conductivity.
  • Conductivity is the inverse of resistivity, measured in siemens.
  • It’s not a good thing and likely an indication that it’s time for a motor repair or more commonly, a motor replacement.
  • And yep, that test is typically performed in direct current. AC megohm testing could be done, but typically isn’t because the higher voltage has more potential to wear stator winding insulation down, causing current leakage.
  • As we know from thermodynamics, stray current manifests as excess heat. It kind of seems like once the insulation starts breaking down, the excess heat hastens the integrity degradation process.

If you’re taking the whole “this guy was European, not American” bit to mean that the ohm could be a metric system (SI) derived unit, you’re right about it. Knowing that, it follows that kilohm and megohm units are just multiples from the base ohm units.  In case you’re ever corrected for pronouncing kilohm as kiloohm and megohm as megaohm, from what I’m seeing now, those longer prefixes are right. But they’ve been shortened by convention. Who needs three syllable words instead of two for just one extra letter?

Now, I know what you must be thinking. Says who? Buck the trend and take the plunge! Use these three syllable variants to rivet and captivate your audience. Insist that these legitimate finer points receive their proper due instead of resigning – and then settling on a lifetime of obedience to a staid status quo. Just do it. And watch out for another type of resistivity: any flying tomatoes or pies coming at you. Don’t say I didn’t warn you.

*The image shown atop this post is of Ohm’s notebook, where he wrote out this practical and useful electrical relationship named after him that we take for granted today.

*Reference sources:



Close the Loop on Power!

Volts, amps, watts, kilowatts, and power. I don’t know about you, but until today, nothing has earned my ire and frustration quite as much as trying to clearly understand the difference between these electrical terms once and for all: volts, amps, watts, kilowatts, and power. They’re all to do with electricity, but what exactly do they each mean, and how do they all fit together? Today is the day for closing this loop!

A practical example involving all of these terms makes it easy to grasp them. Let’s say we have a motor with a dual rating of 230V/460V. Will running a motor at its higher voltage rating save money by using less amperage?

It won’t because we pay for power in watts or kilowatts. Volts are units measuring electrical potential, while amps are a unit of measurement for electrical current. Power is the combined value of amps (electrical current) and volts (electrical potential), and it turns out be the same for each “rated value” (meaning the 230V or 460V voltage values rated to the motor on its nameplate). Power, which is (amps * volts) is measured in watts or kilowatts.

So, for example, if we’ve got:

*14 amps run at 230V, (14 * 230) that’s 3,220 watts, or 3.2 kw of power

*7 amps run at 460V (7*460) is also 3,220 watts, or 3.2 kw of power

What’s interesting to note is that the higher voltage rated value of 460V is double that of the lower value of 230V. It takes half the amps (i.e., running electrical current) to get the same power (measured in watts or kilowatts) with 460V (of electrical potential) to attain 3.2 kw of power.

Running current at the higher rating can only save money on installation costs because smaller diameter wires can be run at the higher rating than are required for the lower rating.

This explanation, which I was lucky enough to stumble on in web research, finally had each term making clear sense, while showing how it all fits together in practical terms.

This is the source article via El Paso Electric: http://c03.apogee.net/contentplayer/?coursetype=md&utilityid=elpaso&id=12592


Thermodynamics in Cavitation

I’m not sure I ever really understood the underlying dynamics involved with hydraulic or liquid cavitation until now. I only knew that it involves pressure and equipment damage potential. Thanks to the common sense writing in Mike Volk’s publication, Pump Characteristics and Applications, it finally makes sense. Let me start by saying that there is no way to grasp this topic without learning something totally new to a lot of us.

Cavitation involves vapor pressure creating bubbles that collapse in implosion. I kept seeing images of bubbles headed toward pump impeller eyes in various books with the caption: “cavitation”. That was a start in the right direction in grasping this. It turns out that actually getting it means learning a little about thermodynamics. Those bubbles are boiling water! Now, wait a minute. How can that be? We are talking about ambient temperature water that is boiling, not high temperature water over a stovetop.

If you’re like me, you might have only known about raising temperature as a means to get liquid boiling. This is where it gets interesting. There is another way to get water or another liquid boiling starting with a lower or even ambient or cold temperature, and that is to lower pressure below vapor pressure. I was reading this in awe because I’ve gone through life without this fascinating and useful information. It turns out that pressure and heat are correlated. Raising or lowering either of these, pressure or temperature, has a direct impact on when cavitation happens.

I’ll use a few examples from Mike Volk’s book in my own words on this. So, if we’re talking about 14.7 psia, which is baseline sea level atmospheric pressure, water boils at 212 degrees F. That sounds familiar so far. Now, let’s go climb a mountain where the psia is lower than sea level atmospheric pressure and boil water via raising temperature at that higher level elevation. Water will actually boil at several degrees lower than 212 F, so that means the temperature level is relative to pressure level.

Now, let’s take the psia in the other direction. Let’s say we have 100 psia with a 300 degree temperature. That liquid will not be boiling at 300 degrees with that higher psia. Incredibly, it will just remain in a liquid state. You need to raise the temperature higher to get boiling in that case, and this is how pressure cookers work. Drop the pressure to 67 psia on it and it will boil. At 60 degrees F, vapor pressure is 0.2563 psia, so if pressure is dropped below that, cavitation results. That boiling water with vapor bubbles collapsing and imploding throughout equipment in a significant pressure drop situation even at ambient temperature causes cavitation!

There are predictable causes for water pressure dropping below vapor pressure in equipment such as a pump. Those causes for pressure loss are a topic for another time. And, I’ve been talking about water here. This topic applies to any liquid. If it’s liquid other than water, specific gravity needs to be factored in and taken into account. Thanks for reading!

Why flow coefficient in valve selection matters

Happy New Year and welcome to my first official learning blog post! Couple my current interest in water strewardship with my inherent love for writing, and it should come as no surprise that I’m ringing in the New Year with a blog of my own. I’ve benefitted so much from the blogs of others. Here is my small part and piece to add to it all from the perspective of a relatively new learner.

In the world of pumps, pipes, and valves that I’m in these days, there is a question of how to size a valve for a process system allowing for optimal performance. Undersizing valves can mean restriction upstream and back pressure buildup which can lead to flashing or cavitation. Oversizing via a too large flow/valve coefficient can lead to the opposite problem: a drastic pressure drop and velocity speed up. Here again, there is the real chance of encountering flashing or cavitation. Trim parts inside a valve can start eroding, causing a “bathtub stopper effect” wherein the closure element of a valve gets sucked into its seat. 

What are flashing and cavitation? These are pressure problems at opposite ends of each other, both with real potential for damaging effects to anything in their paths. When we’re thinking about the concept of pressure, it has to due with a strong or weak flow of water.

  • With high pressure, i.e. low/weak water flow, we want to boost water flow up to meet demand.
  • It is the opposite with strong/high water flow. We need to do the opposite and decrease it.
  • Too fast of a velocity or speed boost of the water flow results in a large pressure drop. A large pressure drop can lead to flashing, whereby water “flashes” into a partially vaporized state with the potential for equipment damage.
  • Slow the speed, i.e. velocity, down too far and we get a large pressure increase. This is where cavitation comes in. Now we have too much pressure, so we’ve got water static pressure dropping below vapor pressure instead. The vapor evaporation collapses on itself and that’s cavitation. Think of caved in or deformed pipes, valves, or equipment and you’ve got the idea here.

This, in part, all has to do with the valve “restriction”. What is restriction? Drumroll, please…

You say you’ve gotta valve in the path of a pipe, do you? Drumroll square roots, because they are all over this and so many other of these doggone mechanical engineering problems. There is an equation called the “Square-Root Law”, whereby flow = restriction * square root of pressure drop. I need to figure out how to get these symbols in my posts properly. Until then, there are calculators and charts that punch these out in no time.

Back to where we started here: valve coefficients. There is a sizing formula for this, known as Cv. Cv = flow * square root of (specific gravity/pressure drop).  Don’t get hung up or caught up in this. And please don’t let anyone try to say that you *just can’t* possibly understand or grasp this due to it being formulaic. Everyone uses calculators. Get your hands on one and you’re as good to go as anyone else making this proclamation. They’re not doing anything else we wouldn’t.

We need to get this right to size valves properly to optimize performance and avoid expensive wear and tear. Flow characteristics come into this, where there are inherent flow and installed flow characteristics. WTH, you might ask. I know I did. Inherent flow does not take into account the effects of piping, while installed flow does. There is more to this, but I am putting a close to this post for now. Thanks for reading. Please feel free to add or comment. Where is the rest of the topic here? I’m not done yet! If there is interest, please stay tuned for more.

All my best wishes for health, happiness, and exciting new learning and development in the New Year!

In gratitude,

Jennifer Zadka

Good company in a journey makes the way seem shorter. — Izaak Walton