A Case Study on Why Pipe Strain Needs to be Measured
September 23, 20191
Let us review this case study on a common issue when working on a pump and motor alignment done by Brian Franks, Owner and Field Service Technician of JetTech Mechanical (www.jettechmechanical.com).
He begins in the normal manner entering the distances of the machine. As you can see this is not a small machine (see Figure 1 below) – there are 57 inches between the motor’s feet and if you add all the measurements together you have 87 inches from the Stationary laser detector unit and the back foot of the movable machine (motor). Notice also that it is a spacer coupling.
He continues doing the alignment work by taking a softfoot measurement on each of the machines and as you can see, there is very little, so we know it’s a stable base that the machine units are sitting on.
An important note is that they would need the coupling open/loose and the pipe disconnected in order to do this correctly.
The new ANSI standard (ANSI/ASA S2.75-2017/Part 1) allowable softfoot tolerance is two thousandths (0.002 thou or 2.0 mils) of shaft deflection and he is below this, so he is good to go. He documents it for his report.
He now performs the machines’ shaft to shaft alignment.
Notice that he’s removed most of the bolts from the coupling in order to allow the coupling to flex. This is a stiff coupling so you don’t want it locking up during the alignment and you also want to make as few moves as possible. So, this is a good practice. This also tells me they know what they are doing which is good.
The tool they are using is an Easy-Laser XT770 which is a dot laser system that can read in the horizontal and vertical plane.
Because this is a spacer coupling, it has two planes of flexure. This means that the measurement results will be two angles. It will say so many thou (or mils) per inch.
Take a look at these results. They are excellent. The top graphic is the horizontal plane because we are looking down upon the machines and we can see all four (4) feet of the movable machine, in this case the motor. The angle is only 0.1 of a thou or mil per inch at the first flex plane. And the angular is the same 0.1 of a thou/mil per inch at the second flex plane. Which is very, very little misalignment.
The lower graphic is vertical plane. We are now looking at the machines from the side. The results at the coupling are very good, we can see the motor has to go down 52.1 thou at the back end, however this is not that important because of the large distances between the machines feet. It also is a spacer coupling which means the angle at each flex plane are in tolerance.
What is important is the angle measured at both planes of flexure at the coupling. And in this case they are excellent!
The next stage is to attach the piping. Brian is looking for shaft deflection as the pipes are attached and torqued. He wants to add a pipe strain measurement to his report.
The crew will use a flange mounting and tightening procedure. This will take some time but the XT770 will operate 24 hours on batteries.
To do this he positions the laser/detector heads at 12 o’clock so that they are reading in the live mode in the vertical and horizontal planes.
He will then use the dynamic measurement program to record the results. In this program he can watch or monitor any change to his alignment results. He will flip the machines making the pump the moveable machine and make the coupling a single flex plane to give a more precise result.
I find this quite interesting because as you can see the pipe has pulled the pump down by 7.1 thou/mils. The black line shows the moveable machine in the vertical plane and in this case we are moving and reading the stationary machine which is the pump.
The top part of the screen is showing the offset, while the lower displays the angle. As you can see, there is no angle or very, very little. The yellow line is showing the movement in the horizontal plane, and you can see that it’s been pulled over a whopping 19.5 mils! This puts it well out of tolerance.
In section6.1.8 Pipe strain, conduit strain, duct strain, and other external forces of the ANSI/ASA S2.75-2017/Part 1 standard it says,
“External forces from piping strain, flange strain, conduit strain, attached ductwork, etc., applied to machine cases shall not be sufficient to cause changes in the shaft alignment of magnitude greater than 50 micrometers (2 mils) vertical or horizontal measured at the coupling.”
Obviously, some work needs to be done to correct these alignment results, but the bottom line is that this pipe strain has been measured and recorded. It’s a quantifiable value that will allow the crew to make a decision. That’s the kind of report I would like if I’m a customer or maintenance supervisor.
Well done JetTech and Brian Franks for doing the job right. Visit JetTech’s website here: https://jettechmechanical.com/.
I has been my experience when doing pipe strain on horizontally opposed suction and discharged on pedestal mounted equipment that you alternate between the suction and discharge.
You pull the center line horizontally as best you can to 3:00 9:00 alternating between the two lines until the piping is tightened.
This should be done before grout to assure you can line the equipment after it is set in stone or epoxy 🙂
API Spec on those flanges for parallelism back in the back would have probably been .010 thousandths.
The crush of the flexatallics would be worked in your favor.
I spent years and years in the field correcting that type of strain, I normally ended up doing most of the pipe stress relief on the equipment.
What is the relationship between pipe strain and pipe size?
The relationship between pipe strain and pipe size is that larger pipe diameters tend to experience greater strain and deflection under the same load conditions compared to smaller pipe sizes.
What is the difference between strain and stress in pipes?
The difference between strain and stress in pipes is that strain refers to the deformation or change in the shape and size of the pipe, while stress is the force or pressure acting on the pipe that causes the strain.
How does pipe size affect pipe strain in piping systems?
The size of the pipe affects the pipe strain in piping systems, as larger pipes tend to experience lower strain compared to smaller pipes under the same loading conditions.
What is pipe strain in plumbing systems?
Pipe strain in plumbing systems refers to the deformation or bending of pipes caused by external forces, such as temperature changes, ground movement, or improper installation. This strain can lead to leaks, cracks, and other structural issues in the plumbing system.
What are the common causes of pipe strain in plumbing systems?
Common causes of pipe strain in plumbing systems include thermal expansion, water pressure, ground movement, and improper pipe installation or support. These factors can lead to excessive stress and deformation of the piping, potentially causing leaks or even pipe failure.
How does temperature affect pipe strain in metallic pipes?
Temperature can significantly impact pipe strain in metallic pipes. As the temperature increases, the metal expands, leading to higher pipe strain and potential issues with alignment and equipment performance.
What is the effect of corrosion on pipe strain?
Corrosion can significantly increase pipe strain by weakening the pipe material, leading to changes in the pipe's physical properties and dimensions, and ultimately, higher susceptibility to deformation and failure under stress.
What are the consequences of ignoring pipe strain in buildings?
Ignoring pipe strain in buildings can lead to severe consequences, such as pipe misalignment, equipment failure, and potential damage to the building's infrastructure, ultimately compromising safety and operational efficiency.
How do you calculate strain on a curved pipe?
Calculating strain on a curved pipe involves measuring the change in length or curvature of the pipe relative to its original dimensions. This is typically done using strain gauges or other measurement techniques to quantify the amount of deformation or stress on the pipe structure.
How does pipe strain occur in pipes?
Pipe strain occurs in pipes due to various factors, such as thermal expansion, pressure fluctuations, and external forces acting on the piping system. These stresses can lead to misalignment, vibration, and potential failure if not properly measured and addressed.
What is the difference between pipe strain and pipe stress?
The difference between pipe strain and pipe stress is that pipe strain refers to the deformation or change in the shape of the pipe, while pipe stress refers to the internal forces acting on the pipe that can cause this deformation.
What is the maximum pressure strain on a steel pipe?
The maximum pressure strain on a steel pipe is typically determined by the pipe's design specifications, material properties, and the operating conditions. Industry standards, such as ASME B31.3, provide guidelines on the maximum allowable stress and strain limits for steel pipes under various pressure and temperature scenarios.
How does pipe strain affect water pressure in homes?
Pipe strain can affect water pressure in homes by causing the pipes to become distorted or misaligned, which can restrict the flow of water and reduce the overall water pressure experienced in the home.
How does pipe strain impact system efficiency?
Pipe strain can negatively impact system efficiency by causing machinery misalignment, increased vibration, and reduced equipment performance, ultimately reducing overall system efficiency and reliability.
What methods measure pipe strain accurately?
Accurate pipe strain measurement methods include strain gauges, laser displacement sensors, and dial indicators, which can quantify changes in pipe dimensions and alignment during industrial processes to prevent machinery issues.
What tools are used for pipe strain analysis?
Common tools used for pipe strain analysis include strain gauges, laser alignment tools, and digital dial indicators. These instruments measure pipe movement, alignment, and deformation to assess the strain on piping systems.
How do environmental factors influence pipe strain?
Environmental factors such as temperature, pressure, and vibration can significantly influence the amount of strain experienced by pipes, which can lead to potential misalignment and operational issues.
What is the role of pipe bends in strain?
Pipe bends play a critical role in strain measurement as they can introduce additional stress and strain on the piping system, which is important to quantify during alignment procedures to ensure proper equipment performance and safety.
How to mitigate pipe strain during installation?
Mitigating pipe strain during installation involves careful planning, proper pipe support, and alignment procedures to minimize stresses on the piping system and prevent operational issues.
What are the industry standards for pipe strain?
The industry standards for pipe strain focus on limiting the amount of stress and deformation in piping systems to prevent machinery misalignment and operational issues. Industry guidelines typically specify maximum allowable strain limits based on pipe material, diameter, and application.
How does vibration affect pipe strain measurements?
Vibration can significantly impact pipe strain measurements, as it introduces dynamic loading and movement that can distort the readings. Accurate pipe strain assessment requires minimizing vibration effects to obtain reliable data for alignment and equipment performance.
What are the signs of excessive pipe strain?
Signs of excessive pipe strain include misalignment between connected equipment, vibration, and visible deformation or bending of the pipe. Excessive pipe strain can lead to equipment failure and operational issues.
How is pipe strain measured during operation?
Pipe strain is measured during operation by utilizing specialized measurement tools that detect and quantify the amount of stress or distortion in the pipe structure. These tools typically include displacement, strain, and vibration sensors that provide accurate data on the pipe's physical condition and performance.
What factors contribute to pipe strain in joints?
Factors that contribute to pipe strain in joints include thermal expansion, vibration, and misalignment between connected equipment. These can cause significant stress on the piping system and lead to potential failures if not properly addressed.
How often should pipe strain assessments be performed?
Pipe strain assessments should be performed regularly, typically on an annual basis, to monitor changes in pipe alignment and identify potential issues before they escalate and affect equipment performance or safety.
What best practices minimize pipe strain risk?
Best practices to minimize pipe strain risk include proper pipe alignment, use of flexible couplings, installation of pipe supports, and regular monitoring and maintenance of the piping system.
What types of sensors detect pipe strain?
Pipe strain can be detected using strain gauges, which measure the deformation of the pipe material. Displacement sensors, such as linear variable differential transformers (LVDTs), can also measure pipe strain by tracking changes in the pipe's position.
How does pipe strain relate to system pressure?
Pipe strain is directly influenced by the system pressure. Higher pressure can create greater stress on the pipe, leading to increased strain and potential misalignment of connected equipment.
What is the role of pipe supports in strain?
Pipe supports play a crucial role in managing pipe strain by providing structural support, preventing excessive movement, and minimizing the stress exerted on the pipe system.
How can thermal expansion cause pipe strain?
Thermal expansion can cause pipe strain when temperature changes cause the pipe to expand or contract, leading to stresses and deformation that can affect equipment alignment and performance.
What is the relationship between pipe strain and pipe size?
The relationship between pipe strain and pipe size is that larger pipe diameters tend to experience greater strain and deflection under the same load conditions compared to smaller pipe sizes.
What is the difference between strain and stress in pipes?
The difference between strain and stress in pipes is that strain refers to the deformation or change in the shape and size of the pipe, while stress is the force or pressure acting on the pipe that causes the strain.
How does pipe size affect pipe strain in piping systems?
The size of the pipe affects the pipe strain in piping systems, as larger pipes tend to experience lower strain compared to smaller pipes under the same loading conditions.
What is pipe strain in plumbing systems?
Pipe strain in plumbing systems refers to the deformation or bending of pipes caused by external forces, such as temperature changes, ground movement, or improper installation. This strain can lead to leaks, cracks, and other structural issues in the plumbing system.
What are the common causes of pipe strain in plumbing systems?
Common causes of pipe strain in plumbing systems include thermal expansion, water pressure, ground movement, and improper pipe installation or support. These factors can lead to excessive stress and deformation of the piping, potentially causing leaks or even pipe failure.
How does temperature affect pipe strain in metallic pipes?
Temperature can significantly impact pipe strain in metallic pipes. As the temperature increases, the metal expands, leading to higher pipe strain and potential issues with alignment and equipment performance.
What is the effect of corrosion on pipe strain?
Corrosion can significantly increase pipe strain by weakening the pipe material, leading to changes in the pipe's physical properties and dimensions, and ultimately, higher susceptibility to deformation and failure under stress.
What are the consequences of ignoring pipe strain in buildings?
Ignoring pipe strain in buildings can lead to severe consequences, such as pipe misalignment, equipment failure, and potential damage to the building's infrastructure, ultimately compromising safety and operational efficiency.
How do you calculate strain on a curved pipe?
Calculating strain on a curved pipe involves measuring the change in length or curvature of the pipe relative to its original dimensions. This is typically done using strain gauges or other measurement techniques to quantify the amount of deformation or stress on the pipe structure.
How does pipe strain occur in pipes?
Pipe strain occurs in pipes due to various factors, such as thermal expansion, pressure fluctuations, and external forces acting on the piping system. These stresses can lead to misalignment, vibration, and potential failure if not properly measured and addressed.
What is the difference between pipe strain and pipe stress?
The difference between pipe strain and pipe stress is that pipe strain refers to the deformation or change in the shape of the pipe, while pipe stress refers to the internal forces acting on the pipe that can cause this deformation.
What is the maximum pressure strain on a steel pipe?
The maximum pressure strain on a steel pipe is typically determined by the pipe's design specifications, material properties, and the operating conditions. Industry standards, such as ASME B31.3, provide guidelines on the maximum allowable stress and strain limits for steel pipes under various pressure and temperature scenarios.
How does pipe strain affect water pressure in homes?
Pipe strain can affect water pressure in homes by causing the pipes to become distorted or misaligned, which can restrict the flow of water and reduce the overall water pressure experienced in the home.
How does pipe strain impact system efficiency?
Pipe strain can negatively impact system efficiency by causing machinery misalignment, increased vibration, and reduced equipment performance, ultimately reducing overall system efficiency and reliability.
What methods measure pipe strain accurately?
Accurate pipe strain measurement methods include strain gauges, laser displacement sensors, and dial indicators, which can quantify changes in pipe dimensions and alignment during industrial processes to prevent machinery issues.
What tools are used for pipe strain analysis?
Common tools used for pipe strain analysis include strain gauges, laser alignment tools, and digital dial indicators. These instruments measure pipe movement, alignment, and deformation to assess the strain on piping systems.
How do environmental factors influence pipe strain?
Environmental factors such as temperature, pressure, and vibration can significantly influence the amount of strain experienced by pipes, which can lead to potential misalignment and operational issues.
What is the role of pipe bends in strain?
Pipe bends play a critical role in strain measurement as they can introduce additional stress and strain on the piping system, which is important to quantify during alignment procedures to ensure proper equipment performance and safety.
How to mitigate pipe strain during installation?
Mitigating pipe strain during installation involves careful planning, proper pipe support, and alignment procedures to minimize stresses on the piping system and prevent operational issues.
What are the industry standards for pipe strain?
The industry standards for pipe strain focus on limiting the amount of stress and deformation in piping systems to prevent machinery misalignment and operational issues. Industry guidelines typically specify maximum allowable strain limits based on pipe material, diameter, and application.
How does vibration affect pipe strain measurements?
Vibration can significantly impact pipe strain measurements, as it introduces dynamic loading and movement that can distort the readings. Accurate pipe strain assessment requires minimizing vibration effects to obtain reliable data for alignment and equipment performance.
What are the signs of excessive pipe strain?
Signs of excessive pipe strain include misalignment between connected equipment, vibration, and visible deformation or bending of the pipe. Excessive pipe strain can lead to equipment failure and operational issues.
How is pipe strain measured during operation?
Pipe strain is measured during operation by utilizing specialized measurement tools that detect and quantify the amount of stress or distortion in the pipe structure. These tools typically include displacement, strain, and vibration sensors that provide accurate data on the pipe's physical condition and performance.
What factors contribute to pipe strain in joints?
Factors that contribute to pipe strain in joints include thermal expansion, vibration, and misalignment between connected equipment. These can cause significant stress on the piping system and lead to potential failures if not properly addressed.
How often should pipe strain assessments be performed?
Pipe strain assessments should be performed regularly, typically on an annual basis, to monitor changes in pipe alignment and identify potential issues before they escalate and affect equipment performance or safety.
What best practices minimize pipe strain risk?
Best practices to minimize pipe strain risk include proper pipe alignment, use of flexible couplings, installation of pipe supports, and regular monitoring and maintenance of the piping system.
What types of sensors detect pipe strain?
Pipe strain can be detected using strain gauges, which measure the deformation of the pipe material. Displacement sensors, such as linear variable differential transformers (LVDTs), can also measure pipe strain by tracking changes in the pipe's position.
How does pipe strain relate to system pressure?
Pipe strain is directly influenced by the system pressure. Higher pressure can create greater stress on the pipe, leading to increased strain and potential misalignment of connected equipment.
What is the role of pipe supports in strain?
Pipe supports play a crucial role in managing pipe strain by providing structural support, preventing excessive movement, and minimizing the stress exerted on the pipe system.
How can thermal expansion cause pipe strain?
Thermal expansion can cause pipe strain when temperature changes cause the pipe to expand or contract, leading to stresses and deformation that can affect equipment alignment and performance.
Let us review this case study on a common issue when working on a pump and motor alignment done by Brian Franks, Owner and Field Service Technician of JetTech Mechanical (www.jettechmechanical.com).
Take a look at these results. They are excellent. The top graphic is the horizontal plane because we are looking down upon the machines and we can see all four (4) feet of the movable machine, in this case the motor. The angle is only 0.1 of a thou or mil per inch at the first flex plane. And the angular is the same 0.1 of a thou/mil per inch at the second flex plane. Which is very, very little misalignment.
I find this quite interesting because as you can see the pipe has pulled the pump down by 7.1 thou/mils. The black line shows the moveable machine in the vertical plane and in this case we are moving and reading the stationary machine which is the pump.
I has been my experience when doing pipe strain on horizontally opposed suction and discharged on pedestal mounted equipment that you alternate between the suction and discharge.
You pull the center line horizontally as best you can to 3:00 9:00 alternating between the two lines until the piping is tightened.
This should be done before grout to assure you can line the equipment after it is set in stone or epoxy 🙂
API Spec on those flanges for parallelism back in the back would have probably been .010 thousandths.
The crush of the flexatallics would be worked in your favor.
I spent years and years in the field correcting that type of strain, I normally ended up doing most of the pipe stress relief on the equipment.