Posted on November 2,
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There are a handful of pipe joining methods that have been adopted by the construction industry, today. These methods are accompanied by an overwhelming amount of resources to guide you through a practical and sustainable piping design. When it comes to Victaulic questions, we want to make it as easy as possible for you to find the answers you need. That is why Victaulic employs a global team of engineers from various backgrounds that support our customers and provide experienced guidance. On any given day, you will see them out in the field helping to demonstrate installations, taking calls from around the world, and writing letters to address potential application concerns. And they aren&#;t just answering Victaulic questions. Victaulic engineers are known around the world for their breadth of application engineering knowledge. But for today&#;s blog post we asked our engineers to give us the top 10 Victaulic questions they hear.
For vacuum applications, any Victaulic pipe coupling that features our Installation-Ready&#; or FlushSeal&#; gasket profiles should be used.
Yes, Victaulic offers gaskets designed specifically for drinking water applications that hold a variety of agency approvals around the world. For a complete list of ANSI/NSF 61 and 372 approved gaskets for drinking water applications refer to submittal publication 02.06.
Yes, Victaulic products are designed to be buried, however, there are considerations that need to be made for each application such as soil conditions and available coatings. The selection is based on the requirement of the project.
It is common to coat products to increase the corrosion resistance of the base metal. The maximum coating thickness that can be applied to Victaulic products is .010 &#;/.25 mm. This information can be found in the I-100 Victaulic Field Installation Handbook on page 20.
Yes, Victaulic EPDM gaskets are compatible with glycol. This information can be found in the Seal Selection Guide (05.01).
To confirm Victaulic&#;s gasket compatibility with a fluid, please reference the Seal Selection Guide (05.01), or contact the Victaulic Applications Engineering Department.
The answer to this question is a bit complicated, but simply put, the difference between a Victaulic rigid pipe coupling and a flexible pipe coupling is the movement capabilities of the joint. Flexible pipe couplings provide axial and deflection movement capabilities. Rigid couplings do not allow movement in the joint. Typical applications for flexible pipe couplings include thermal accommodation as well as seismic, vibration and noise attenuation. For more information on the differences between rigid and flexible pipe couplings and the history of how they were invented, check out this recent blog post.
You can find the pressure ratings of each Victaulic product in the individual product technical submittals. These submittals can be found here.
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Victaulic offers numerous pipe groove profiles. To confirm your pipe grooves meet Victaulic specifications, reference one of the groove specification documents below. Victaulic Grooved Specifications can be found on victstage.wpengine.com.
Victaulic products are designed for use on several types of pipe including carbon steel, stainless steel, ductile iron, PVC, CPVC, HDPE, aluminum, and copper. To determine if a product may be used on any of those materials mentioned above, view the Victaulic Product Guide.
Did we answer your question in this post? If not, contact the Victaulic Applications Engineering team who is standing by to field your questions. And be on the lookout for future blog posts where we try to capture more answers to some of your commonly asked Victaulic questions.
Flow testing has confirmed that the joints exhibit good flow characteristics. Testing involved grooved and plain-end 4-in. Type K copper tubing, and 2 in. to 8 in. Schedules 10 and 40 carbon steel pipe at flow velocities of 4, 8, 12 and 16 ft./sec. at ambient water temperature.
Pressure taps located 10 ft. apart on a straight section of pipe (or tube) established the baseline measurement at the tested flow rates. Then, the pipe/tube was cut into four segments to insert three roll-grooved pipe joints between the pressure taps. After the new pressure losses were recorded, the baseline loss was subtracted out to determine the insertion loss. The average loss of each grooved coupling joint was about 1/2 equivalent feet of pipe.
Additional independent testing by Factory Mutual Research Corp. supports these findings. Factory Mutual&#;s Loss Prevention Data Technical Advisory Bulletin 2-8N stipulates that one equivalent foot of pipe be added for each roll-grooved joint on any pipe size. This is conservatively higher than actual test values, yet still relatively low compared to the values established for components such as valves and fittings. These values further attest to the low loss characteristics of roll grooved joints.
Roll grooving pressure drop is consistent and can be accounted for during system design. Although, in theory, welded systems produce little to no loss at the joints, variables of craftsmanship can lead to welding material entering the pipeline, interfering with flow and, in some cases, dislodging and causing a system blockage.
Another concern is the ability of a grooved joint to perform adequately under load. Regardless of pipe joint type, a pipe under load exhibits two forms of stress: longitudinal and hoop. Longitudinal stress is a tensile stress, tending to stretch the pipe axially. A failure from longitudinal stress produces a circumferential fracture. Hoop stress is &#;ballooning,&#; a radial expansion, and the potential failure mode is a lengthwise split. The calculations for determining stress also show that the hoop stress will be twice longitudinal stress:
Hoop stress = (P x OD) / (2 x Tw)
Longitudinal stress = (P x OD) / (4 x Tw),
P is the line pressure, OD is the outside diameter and Tw is the wall thickness. This means that overstress failures are most likely to occur along the length of the pipe &#; in a weld seam, for example &#; not on the pipe circumference.
Everything else being equal, a decrease in wall thickness results in an increase in hoop stress. In a grooved joint, the coupling housing, which engages the groove, prevents diametric expansion and reinforces the pipe. This suggests the grooved technique doesn&#;t produce greater hoop stress and, therefore, doesn&#;t weaken the pipe. Any potential increase in pipe hardness, reduction in tensile strength or reduction in elongation the roll grooving process produces has no effect on the pressure capability of the joint, and pipe material changes are comparable to any other cold-forming manufacturing operations.
Cut grooving reduces the wall thickness by removing a narrow circumferential strip of material from the outside surface. The hoop stress remains approximately the same because the groove is narrow and reinforced by the full wall thickness of pipe on either side of the groove. The groove also is reinforced by the coupling key engaged in the groove, preventing it from expanding diametrically. However, the longitudinal stress increases proportionally with the decrease in the wall thickness. Therefore, if one half of the original wall thickness remains, longitudinal stress is doubled or approximately equal to the hoop stress.
Because the cut groove depth in standard wall thickness pipe removes only about one-third the original pipe wall thickness, the hoop stress remains larger than the longitudinal stress. Any over-stress failure continues to occur along the length of the pipe, not at the groove, demonstrating that the groove area isn&#;t weaker than the longitudinal barrel of the pipe. Again, this means that the groove doesn&#;t compromise joint strength.
The pressure rating on a grooved mechanical pipe joint is determined in consideration of all the components involved. Grooved pipe has no rating without the corresponding coupling, and coupling ratings are a function of the piping material and wall thickness. Every manufacturer&#;s published pipe joint rating is calculated or tested on pipe that contains a groove, meaning that any potential effect of the groove on the strength of the pipe is incorporated in to the coupling&#;s performance rating.
Another misconception about grooved mechanical pipe joining is that couplings can&#;t produce rigid joints and require extra supports to prevent system sagging. The housing on a rigid coupling positively clamps the pipe to produce a rigid joint, providing system behavior characteristics similar to those of other rigid systems. The piping remains aligned and isn&#;t subject to axial movement or angular deflection.
Systems using rigid couplings need support techniques identical to those of welded systems when designed and installed according to the hanger spacing requirements as noted in the ASME B31.1 Power Piping Code, ASME B31.9 Building Services Piping Code and NFPA 13 Sprinkler Systems Code.
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