Metraflex manufactures expertly engineered products designed to handle a wide range of movement in any application. (more…)

Finite Element Analysis

Need help designing an engineered piping system? Contact Metraflex. We offer delegated design services for firms needing this special expertise.

Materials and Stamped Calculations
Increasingly project specifications are calling for a “delegated design submittal” and making the contractor responsible for the design of piping expansion. Metraflex uses CAEPipe® finite element analysis software to analyze your complex piping layouts for movement, stresses and anchor loads. You receive all the materials and calculations required for you to meet submittal requirements.

Metraflex services include:

• Stress analysis
• Design Calculations
• Anchor Details
• Guide details
• Material Certificates
• Welding Certificates

Learn more by contacting your local Metraflex account representative or contact Metraflex with your specific needs.

Shortly after Metraflex introduced the first flexible pipe loop (the Metraloop), it became the standard used by engineers and designers to protect piping systems in seismic events, exactly what you would expect from something invented by a person named Jim Richter.  Metraflex has been leading the way with seismic solutions ever since.

 

All the Metraloop, V loop, and Dog leg products are all ideally suited to be used for seismic applications.  The low spring rates, movement in all directions, and that they do not impart any thrust loads on the piping reduce loads on the seismic bracing make them ideal for seismic applications.  Additionally, these products are capable of movement in all six planes.  

All these products are available in standard configurations and customized versions, tailored to meet your projects requirements.  Additionally, the Seismic Gator was developed to be used when there was not enough space to use a Metraloop. 

Application and Installation

We have found that the construction requirements to install a functional seismic protection system for piping systems is ahead of the building codes themselves.  Outside of any local codes, the only national code that we are aware of that gives us guidance of how to install a seismic device is NFPA 13.  Although this is only mandatory for fire sprinkler water, it is a good basis of design for other systems if local codes do not exist.

NFPA 13 specifies that that the seismic device / flexible pipe loop be no more than 2 feet from the seismic separation.  It also specifies that the bracing can be no farther than 6 feet from the seismic separation.

One of the most common seismic questions is; how do you fit in a Metraloop where the seismic separation is located between two walls that are close together?

You would need to create a seismic clearance in one wall as shown below.  The seismic clearance needs to be the seismic movement plus 2 inches per NFPA 13.  If you do not have this clearance a seismic event would shear off the pipe.

You would then place the Metraloop on the same side with the seismic clearance and put the brace on the other side of the Metraloop.  If the customer is concerned with an open hole, this can be sealed with a sheet metal escutcheon plate that would yield during a seismic event and need to be replaced afterward.  There are also companies that offer a rubber boot for these applications. Be sure to inspect all loops after a seismic event.

Another common question is if thermal and seismic movements can be combined into one devise.  This is an important consideration since we have seen cases where the seismic movement had been addressed without any consideration of the thermal growth of the piping.  One device can be used for both seismic and thermal movements can be done if:

1. The seismic device (Metraloop, V-Loop, or Dog Leg) is sized for the combined movement of the Thermal and Seismic loads.
2. The seismic braces next to the seismic device are replaced with guides.  Typical Spider Guides with a corresponding pipe hanger is shown in the detail below.

Note:  Make sure the guide is also sized for the combined movement.

In Line Seismic Joints

For installations where there is no room to install a Metraloop or V Loop, Metraflex has developed the Seismic Gator that is designed to handle movement in all directions.

The in-line profile is achieved by utilizing a combination of an externally pressurized joint, the Metragator, and a pair of gimbal joints on each end. The Seismic Gator is a rugged and reliable joint, but it will develop high thrust loads like an in-line bellows, unlike the Metraloop which develops very low loads.

Seismic Breakaway Hanger

See below details on how the Seismic Breakaway Hanger is installed:

To ensure your seismic devices (Metraloop, V Loop or Dog Leg) will perform properly in a seismic event, it is very important to use a Seismic Breakaway Hanger in the following situations.

1. Whenever the seismic device to installed to close to the deck of the structure.  The seismic device needs to be installed at a distance of a minimum of two times the seismic movement minimum 12” or during a seismic event the seismic device will swing into the structure causing damage to both the structure and the seismic device.  The picture below shows an example of a +-30 Dog Leg with a seismic Breakaway Hanger installed.

2. For applications with large movements that require longer hose lengths.  The hose section will likely sag, so an intermediate support is required to prevent this sag.  This is very important for plumbing system applications that require a proper pitch.  The solution is a Seismic breakaway Hanger installed with a saddle on the hose as shown in the detail below.

3. To ensure that both sections of hose in a seismic device move freely and evenly.  What a lot of designers and users do not understand is that in a seismic event very often one leg of a seismic loop takes all of the movement, while the other leg sees very little movement as shown in the details below.   The simple solution is to install a seismic breakaway hanger in the support rod, so that in a seismic event it will release allowing both sections to move freely and evenly.

After any seismic event, the Seismic Breakaway Hanger can be simply reset.

How Not to Install a Seismic Device.

In the below picture you will see a set of seismic Metraloops installed over a seismic separation.

If you look closely, you will notice that the top of the loops are supported with a rigid hanger.  If the structure on either side of the seismic separation moves in the Z axis (vertically) the sections of hose will either be pulled apart or over compressed.  It is always important for a successful installation, for both seismic and thermal applications that the top of the loop be free to move freely.

In this case the solution is simply installing a Seismic Breakaway Hanger at the top of the loop.  In a seismic event it will release, allowing the loops to move freely without damage.

Base Isolation Systems

Base Isolation seismic systems is an alternative to the traditional design with seismic separations.  In a base isolation system, the entire structure is supported by base isolators that will allow large amounts of horizontal movement.  Horizontal movements of 36” are common, vertical movements are usually 1 or 2 inches.  This is an ideal way to retrofit seismic protection into an existing building.

Metraflex considers seismic joints for base isolation systems to be engineered products. Contact Metraflex or your local representative for more information.

The engineering staff at Metraflex has decades of combined experience. 
Please feel free to call us to review your application.

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By James C. Neville Project Engineer, Engineering Services
Blue Ridge Numerics, Inc.
October 31, 2006

Executive Summary:
Conclusion: The CRV Flex provides a better flow profile entering the pump, therefore better pump performance, than a suction diffuser. The CRV Flex also has a significantly lower pressure drop.

Introduction:
Two CFD simulations are contained herein. Both analyze leading products used to condition and improve flow entering a pump. The first CFD analysis is of two popular styles of suction diffusers: the traditional cylindrical screen diffuser and the more recent model with a conical diffuser screen.
The second simulation is of the CRV Flex. A fixed vane device placed in front of the pump’s suction side elbow which imparts a half revolution to the media flowing through the elbow (see back cover). This minimal deflection of flow negates the turbulence caused by the geometry of the 90 degree elbow and produces measurably better flow conditions and
lower pressure drops than a suction diffuser.

Methodology:
Modeled were 4” x 3” reducing suction diffusers and a 4” x 3” reducing CRV Flex. Both designs were simulated at fluid velocities of 4 ft/sec and 10 ft/sec to determine overall pressure drops as well as the condition of the flow exiting the devices. Flow conditions between these ranges, slightly below and above can be interpolated from the data.
Simulations were conducted using CF Design version 9.0 from Blue Ridge Numerics, Inc.

Project Summary:
A computational fluid dynamics analysis was performed on the Metraflex 4” x 3” suction diffuser to determine the overall pressure drop through the diffuser as well as the condition of the flow exiting the device. Furthermore, an analysis was performed
on a cylindrical screen design (constant screen cross-section) for a performance comparison. Both designs were simulated at fluid velocities of 4 and 10 ft/s. The simulations were conducted using CFdesign version 9.0 from Blue Ridge Numerics, Inc.

Project Methodology:
The CFdesign analysis setup is shown below in Figure 1. Additional pipe lengths were modeled upstream and downstream of the diffuser to ensure fully developed flow at the device and at the constant pressure outlet.

Simulation Assumptions:
Various assumptions were made for the simulation of the suction diffuser and are listed below:

• Steady-state conditions
• Incompressible flow
• Water modeled at standard temperature and pressure
• Screen diffuser modeled as a distributed radial resistance (34% open area)
• Thermal effects negligible

Results:
Cut-surfaces showing pressure results are displayed in Figures 2-5 below. These cutsurfaces are oriented in such a way that they bisect the flow passing through the device. Figures 2 and 3 show results from the 4 ft/s inlet flow case while Figure 4 and 5 show those from the 10 ft/s case. The pressure drop across each design is summarized in Table 1.

Table 1. Pressure delta summary across the device for each screen type and inlet flow velocity.

Contours of fluid velocity magnitude through the device are shown in Figures 6-9 below. It is clear that several areas around the diffuser screen do not experience significant fluid flow and can be considered areas of stagnation.
The effect of the cross-like screen support can be seen in the fluid velocity results. Higher velocities were found in the top two chambers, especially in the conical diffuser analyses. It is shown that the cylindrical diffuser provides a more uniform fluid velocity among the four inner chambers.

Both designs showed that approximately 53% of the total fluid volume travels through the top two inner diffuser chambers, yet the difference in peak velocities between the upper and lower chambers was consistently higher in the conical design.
This shows that the fluid velocity distribution exiting the screen diffuser region is more uniform with a cylindrical screen diffuser.

A comparison of the flow profiles approximately 3 inches downstream of the device is shown below in Figure 10. In both the 4 and 10 ft/s scenarios, the cylindrical diffuser screen provided a significantly more uniform outlet flow.

Fluid particle traces released into the inlet stream are shown below in Figures 11-16. These traces help to visualize the fluid path as it travels through the device. In particular, Figures 13 and 16 highlight the areas of flow stagnation around the screen and the higher speed flow exiting the upper two inner diffuser chambers.

Conclusions:
After reviewing the results obtained through CFD analysis, it is clear that the main difference in performance between the two diffuser screen designs is to be found in the downstream flow profiles. While the overall pressure drop through each suction diffuser is almost identical,
the downstream flow profile is more uniform with a cylindrical diffuser. Both designs showed similar areas of minimal fluid flow through several portions of the diffuser screen.

Project Summary:
The Metraflex six-bladed CRV flow conditioner was analyzed to determine its effect in a 4” to 3” reducing elbow at water velocities of 4 and 10 feet per second. The simulations were conducted using CFdesign version 9.0 from Blue Ridge Numerics, Inc.

Project Methodology:
The CFdesign analysis setup is shown below in Figure 1. Additional pipe lengths were modeled upstream and downstream of the elbow to ensure fully developed flow at the CRV and at the constant pressure outlet.

Simulation Assumptions:
Various assumptions were made for the simulation of the elbow and are listed below:

• Steady-state conditions
• Incompressible flow
• Water modeled at standard temperature and pressure
• Constant water properties
• Thermal effects negligible

Results:
Cut-surfaces showing the velocity profile and velocity vectors for both analyses are shown below in Figures 2 and 3, respectively. Note that there is very little discernible flow separation around the reducing elbow with the CRV in place. The CRV aides in providing a more uniform velocity profile beyond the reducing elbow.

A cut-surface of velocity approximately three inches downstream of the elbow is shown in Figure 4. Both analyses show similar velocity profiles, with slightly lower velocity regions near the bottom of the pipe due to the swirling action of the CRV.

The pressure gradient for both analyses is shown below in Figure 5. The total pressure drop through the CRV and elbow was found to be 0.37 psig for the 4 ft/s case and 2.19 psig for the 10 ft/s case.

Figures 6 and 7 below show particle traces released from various points on the pipe inlet. These traces show where individual fluid particles will travel as they pass through the system. Note the similar flow patterns shown for both flow rates. The swirling effect of the CRV is clearly visible.

Conclusions:
The Metraflex CRV flow conditioner is shown to provide a near uniform velocity distribution downstream of the elbow. The CRV is effective in eliminating the large recirculation regions that would develop downstream of the elbow without a flow conditioner.

Standard CRV® Flex Configurations

The Challenge of Installing New Mechanical Systems in an Occupied Building.

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It had been nearly 4 decades since the John C Kluczynski Federal Building in Chicago had been constructed, and no significant upgrades to the mechanical system had been undertaken since its ribbon cutting in 1974. So with the enactment American Recovery and Reinvestment Act (ARRA), the rush was on to quickly take advantage of the new ARRA funds and upgrade the building’s mechanical system to meet new federal guidelines for energy consumption.

The 45-story steel-frame Kluczynski Building contains 1,200,000 square feet of space and is one of a the three-building Federal Center complex, which also includes the US Post Office (Loop Station) and the Everett McKinley Dirksen United States Courthouse. Approximately $11 million was budgeted to replace the 36-year-old mechanical equipment and riser pipes. The project was started on July 1, 2010 with an anticipated completion date in February 2012.

Minimizing flame and odor in an occupied building
“One of the major challenges to upgrading the mechanical system and risers is doing it while the building is occupied,” explains Michael Johnson, Executive Vice President, Edwards Engineering, Elk Grove Village, IL. “The system needs to be installed with the least amount of flame and using installation methods that produce as little odor as possible, minimizing disruption to work spaces.

“There are 44 risers in three tiers for a total of 132 risers in the building,” he continues. “and all the copper risers needed compensators to accommodate a specification of over 3-inches of expansion. This meant thousands of guides would be welded to the building frame, which was in direct conflict with minimizing odor and flame.” The drawings called for 264 bellows compensators, two compensators per riser, and per manufacturers recommendations over 1900 guides would be required to complete the installation.

Again, with the building occupied and the work of federal employees to continue with minimal interruption, finding locations to install all these guides was next to impossible. Risers were not always close enough to structural steel to install guides in proper locations. As a result, Edwards revisited the drawings to find alternatives to the compensators and guides originally specified. “We needed to determine a much better solution since welding thousands of guides was really not feasible,” explains Mr. Johnson.

“We found the Metraloop expansion loop would easily handle the 3-inch movement, plus require significantly fewer guides,” comments Mr, Johnson. “The Metraloop installation requires only one (1) Metraloop per riser and two (2) guides per Metraloop for a total of only 264 guides, a fraction of the number of guides previously required.

“The ability of the Metraloop joint to absorb non-linear expansion also assisted in the installation of the piping risers,” he continues. “In addition, the dramatic reduction in the number of guides that needed to be installed meant less interruption where people were working, and significantly less labor required to weld all those guides onto the building steel.” Edwards Engineering estimated a savings of 9-12 hours of labor per riser, times 132 risers, or approximately 1,200+ man-hours.

The extremely flexible Metraloop expansion joint has virtually no anchor loads and requires minimal guiding. Capable of 360° movement, the Metraloop expansion joint has been installed in thousands of buildings internationally. It helps compensate for building settlement, thermal expansion and contraction, and helps building piping systems meet code for seismic applications. The Metraloop expansion joint, with is ability to move easily in the X, Y and Z planes, helps protect the integrity of a piping system during a seismic event.

Once Edwards determined Metraloops were the best option to reduce impact in the buildings retrofit, they worked with Metraflex to confirm their calculations and expedite the first shipment of Metraloops to the worksite. “We are installing 2-inch to 4-inch Metraloop joints and needed to start the installations as soon as possible once we determined the existing drawing specification would not work,” explained Mr. Johnson. “Metraflex was able to ship the first 24 Metraloops within 4 days.”

As the multi-phase mechanical retrofit continues, and more risers have been replaced, the Metraloops expansion joints continue to simplify installation and reduce labor costs. “This was really the perfect solution to our problem,” states Mr. Johnson. “If we had to install all those guides it would have required a lot of disruption, and a lot of time. The Metraloop joints have removed the complexity and streamlined the riser installations.”

For more information on this installation and to see how the Metraloop expansion loop exerts a fraction of the anchor load, requires far fewer pipe guides, and reduces overall project costs, go to www.metraflex.com/metraloop, or contact Metraflex at info@metraflex.com; 1-800-631-4347

FIRELOOPS® CROSS BUILDING’S EXPANSION JOINTS TO PROTECT FIRE SPRINKLER SYSTEM

“The installation was easy,” commented Keith Cunningham, Foreman, National Fire Protection, Inc. “It was the first time we had installed a joint to handle building movement, as well as the first time to install loops, and these went in real easy.”

Expansion joints not part of original design
Mark O. Hatfield Clinical Research Center is an 850,000 square foot addition to the National Institutes of Health (NIH) Clinical Center. It will be highly efficient and flexible state-of-the-art facility with 600,000 square feet of hospital and 250,000 square feet of research laboratories.

The need for joints that crossed over the building’s expansion joint came in as a change order.

The joints needed to fit into the existing design, and allow for the building movements specified in the revised plans.

The Metraflex Fireloop was specified, in 2-inch, 2- 1/2 inch and 3-inch sizes with grooved ends. The loops were installed in 30 locations in mains and branch lines throughout the fire protection system and pressurized to 175 psi.

“We installed the Fireloops parallel to the ceiling and all we needed were hangers for the end, and at the two connections,” Keith explained.

Having never installed loops before, Keith was pleased with the simplicity of the installation. “I would use the Fireloops again in other projects in the future,” he commented.

 

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A Comparison of traditional Y Strainers and Basket Strainers to the new LPD Strainer

Considering the y-strainer as a critical, energy-saving piping system component

Pumps, chillers, boilers and heat exchangers are the high-profile piping system components targeted to improve energy efficiency. More obvious in their energy consumption, these units are constantly being re-engineered, tested, measured and introduced to the market with improvements that measurably improve energy savings.

Other low-cost components in the system are routinely plugged into a design, accepted for their role in creating pressure drops and turbulence since there are no alternatives. One of these components is the strainer.

Today’s traditional strainer design was actually introduced over 100 years ago. The strainer was created to protect expensive equipment, such as pumps, chillers, boilers and heat exchangers by removing debris from fluid before it reached these components. But, a century ago energy consumption was not a consideration and energy efficiency was an unknown concept.

It is now better understood how strainers add pressure top due to their antiquated design and a screen that accumulates debris and increasing pressure loss. This pressure loss translates into pumps increasing energy consumption. It’s time to consider the strainer’s energy consumption.

A new strainer has recently been introduced. The new LPD y-strainer is redesigned from the ground up to provide superior pressure drop. Its internal geometry has been completely re-engineered, which also allows for a much larger screen with significantly increased debris capacity.

Following are comparisons between the centuryold y-strainer and basket strainer designs and the new LPD y-strainer to assist in making a more informed decision on which component is right for your piping system.

Y-strainers

Y Strainers are widely used in hydronic systems and have been the most common type of strainer because

1) Unlike basket strainers they can be installed in horizontal and vertical pipe runs.

2) They can be blown down.

3) They are less expensive than basket strainers.

Basket Strainers

Basket strainers are the go to selection for strainers in “open” systems such as cooling towers. There were several perceived reasons for this.

1) Basket strainers have a higher capacity over the traditional “Y” strainer.

2) Basket strainers have a lower pressure drop.

3) Basket strainers are available with clamp on covers making cleaning the screen easier, then it would with a traditional “Y” strainer.

Taking a closer look at these points we will address some long-standing misconceptions about strainers, and discuss alternatives that will improve piping design.

Figure 1

Figure 2

The redesign of the strainer started with the basic Y strainer to take advantage of the versatility of vertical and horizontal installation, the ability to be blown down and the lower cost.

A CFD analysis and quickly confirmed the obvious, that the bridgewall universally used in Y strainer design caused restriction and an abrupt change in direction of flow, a big contributer to pressure drop.

In the new design, the bridge wall has been eliminated. See CFD analysis results below.

The bridge wall restricted flow and created turbulence in the strainer resulting in increased pressure loss (Figures 1 and 2).

The next design improvement – the pitch of the screen. Screen pitch was lowered from 45º to 22.5º.

Figure 3A: The old, traditional strainer, left, has a steeper screen pitch. Right, the new LPD Y-strainer has a shallower pitch allowing the screen to be much longer.

The lower pitch resulted in a much larger area of the screen to be in the flow path. This resulted in lower internal velocity and lower pressure drop (Figures 3A and 3B).

The change in pitch now allowed the screen to be much longer. Then as part of the redesign the casting was made larger to increase screen diameter (Figures 4A and B).

The result was not only a screen with much larger area for debris capacity, but a much larger screen area in the fluid flow.

Figure 4: Comparisons between traditional strainer screens and the new LPD Y-strainer

Figure 4B: Four-inch strainer screens. Basket strainer screen, left, y-strainer screen, center, and LPD Y-strainer screen, right.

The results of all these design improvements result in a major improvement in the CV values of the LPD strainer, in some sizes almost double that for the old fashioned Y strainer and substantially better than a basket strainer as shown in (Figure 6).

Note, the CV values shown (Figure 6) are results from independent testing. We have found several basket strainer manufacturers literature that had much higher values that we believe to be overstated.

Probably the best feature of the LPD is its ability to capture debris. The same amount of debris in an LPD will have far less of an impact than it would in a traditional Y strainer or basket strainer. Using a dollar bill to represent the same debris blockage in each screen (Figure 7), it is obvious how much more unobstructed screen area is available in a 4-inch LPD vs a traditional, old-style 4-inch strainer.

Figure 5: C_v comparisons between traditional strainer screens and the new LPD Y-strainer

Figure 6: Independent testing results comparing a clean LPD Y-strainer, and various amount of debris blockage, to a completely clean competitor strainer.

To demonstrate how the difference in pressure drop is even more dramatic between the two LPD and the traditional y-strainer, a test compared an LPD strainer with 92.7 in2 of blockage (29% blocked) still has a better CV than a 100% clean competitive strainer.

The larger capacity of the LPD strainer screen also means that you do not have to blow it down as often as a standard Y strain reducing maintenance costs.

Y-strainer vs Basket strainers

Basket strainers are considered easier to clean than y strainers. If shut off valves are properly located, the basket strainer does not lose water or require the system be drained to clean.

However, the LPD can be blown down where the basket strainer cannot. If blown down, the LPD may not even need to be cleaned.

The basket strainer is available with a clamp-on cover requiring only one bolt to be loosened to remove the cover. Depending on the manufacturer, clamp-on covers result in a lower pressure rating than a standard flange cover. This is normally a big advantage over a traditional Y strainer using a standard pipe flange for a cover. However, the new LPD design features a cover with 4 or 6 bolts depending on the size. Additionally, the cover of LPD strainers 10” and larger are hinged for easier handling.

Whenever a cover is removed from any of the traditional basket strainers or y strainers there is often a custom gasket that needs to be replaced. The LPD strainer uses a reusable O-ring seal.

In conclusion, it is taken for granted that science and technology has improved virtually everything around us. However, it has been over 100 years since technology has tackled the inherent flaws in y-strainer design. With the introduction of the new LPD y-strainer, significant energy savings have been captured with its new design. The LPD y-strainer is a significant improvement over other strainers, making it the best performing strainer on the market today.

Just days after installation of Metraloop expansion loops at Safeco Field, Seattle experienced a 6.8 magnitude earthquake Safeco field. After all the movement and swaying, inspection of the piping system showed Metraloops had helped keep the system intact.

While installing a trench box steam distribution system at Le Moyne College, engineers chose to stacking Metraloops in manholes instead of using hard pipe loops, translating into significant savings.