Explore the various applications of snubbers, sway braces and sway struts in piping systems and equipment. Learn how these products help prevent pipe system failure due to seismic loads, flow transients, wind loads, safety valve thrust loads or pipe rupture. Discover the various tests performed within PT&P’s facility to ensure product quality, including cycle testing, travel testing and load testing.
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Shock Control Devices Presentation
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2. Shock Control, Restraint and Support Devices Piping Technology & Products, Inc. Webinar Presentation hosted by… For Audio: 1.) Select Speakers/Headphones & Turn Speakers Up or 2.) 10:00 am Session : Dial (1) 323-417-4600 Access Code: 380-579-405 2:00 pm Session : Dial (1) 516-453-0014 Access Code: 307-154-138 (for countries outside the U.S. please refer to the list of numbers in your confirmation email)
3. PT&P and Subsidiaries Fronek Anchor Darling Ent., Inc. ASME Nuclear Qualified Pipe Shields, Inc. Sweco Fab, Inc. ASME U-Stamp PIPING TECHNOLOGY & PRODUCTS, INC. Member of MSS, SPED, APFA U.S. Bellows, Inc. Member of EJMA
10. Hydraulic Snubbers Reservoir Adjustable Rod End Lock Nut Extension Piece Cylinder Flow Control Assembly Stroke Position Datum Point Piston Rod End Hydraulic Snubber
43. Thank You For Attending… Shock Control Devices Webinar Please send any additional questions or inquiries to info@pipingtech.com We invite you to visit our Discussion Forum at www.pipingtech.com
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Hello everyone, I would like to welcome you to our Webinar on Shock Control, Restraint and Support Devices. The Webinar today is hosted by Piping Technology & Products. I am Jerry Godina and I will be your presenter. If you would like to join in on the audio portion of the presentation, please make sure you select speakers/headphones in the audio choice box and double check that your volume is turned up. You can also listen to us by telephone, 10:00 am for the United States, just dial: (1) 323-417-4600, for countries other than the US, please refer to the list of numbers in your confirmation e-mail. The access code for this presentation is 380-579-405 2:00 pm for the United States, just dial: (1) 516-453-0014, for countries other than the US, please refer to the list of numbers in your confirmation e-mail. The access code for this presentation is 307-154-138 Also, if you have a question during the presentation, please feel free to type a question into the text box you see to the right of the presentation, or if you prefer, you can ask questions after the presentation during our “Questions and Answers Session.”
Piping Technology & Products, Inc. (Member of MSS, SPED, APFA) * Engineered Pipe Supports: - Spring Hangers: Variables, Constants and Big-Ton Spring Supports - Vibration Control Devices: Snubbers and Sway Struts - Support Assembly Components: Clamps and Hardware - Pre-Insulated Pipe Supports: Cryogenic and Heat Applications (Cold & Hot Shoes) - Fabricated Pipe Shoes, Guides and Anchors * Slide Bearing Plates * Anchor Bolts and Embed Plates U.S. Bellows, Inc. (Member of EJMA) * Expansion Joints Metallic, Thin-Wall, Thick-Wall, Fabric, Rectangular, and Slip-Type Sweco Fab, Inc. (ASME U-Stamp and R-Stamp Certified) * Pressure Vessels, Pig Launchers/Receivers, Spectacle/Line Blinds, Instrument Supports and ASME/Misc. Fabricated Items. Pipe Shields, Inc. * Insulated Pipe Supports for: - Commercial and Light Industrial - Heavy Industrial: Based on Mounted Anchors - Pipe Riser Clamps Fronek Anchor/Darling Enterprises Inc. (ASME Nuclear Qualified) * Hydraulic Snubbers: Short Strut and Adjustable Strut * Mechanical Snubbers * dynA/Damp Compensating Strut
“Once again, thank you for attending our Webinar today…” Snubbers Most common example of working principle: automotive safety belt Not activated under normal thermal contraction and expansion 2 types of mechanical Transmits force to fixed base Primarily acts as a rigid restraint Sway Braces Restraint load is proportional to travel Sway Struts 1 degree of freedom
Snubbers are used as restraining devices to safeguard the piping system against Impulsive Loading while introducing negligible resistance during normal thermal movements… Undesirable abrupt movements of the components can be caused by: 1.) Internal excitation, such as, pressure shocks from valve operation, water hammer, boiler events, turbine trips, pipe breakage and safety/relief valve discharge Or Impulsive Loading can be cause by: 2.) External excitation, such as, wind load, seismic or cyclic events, impact by moving vehicles and explosions Under normal conditions, slow thermal movement of the piping system does not activate the snubber. Typically, an impulse type event will occur for a short time, but with a large magnitude. As the piping system responds, the impulse is transmitted to the snubber through SUPPORT MEMBER- 1. When the impulsive force exceeds the Predetermined Threshold value, the snubber activates, becoming a rigid support and arrests axial movement transmitting the shock through SUPPORT MEMBER -2 to the FIXED BASE . (NOTE: piping system will not move) Summary : In a sudden shock event, an instantaneous, secure and almost rigid connection is produced. The resulting dynamic loads are at once conducted into the structural connection. Normal operational movements of the piping and other components remain unhindered after impulse loading. In the case of seismic events, typical Frequency Response is 1 to 33 Hz.
The two main types of snubbers are Hydraulic and Mechanical Design criteria vary; however, there are a few common design requirements: 1.) Type of Motion: Snubbers must be able to move back and forth, so that it can lock the motion and resist inertial forces of oscillatory nature in both directions along the longitudinal axis of the snubber. 2.) Normal Operation: During normal conditions, snubbers shall allow essentially free movement of component imposing minimum resistance when the component is subjected to non-dynamic loads such as those imposed by thermal expansion and contraction. 3.) Breakaway/Drag Force: The force required for axial movement shall not exceed 1 to 2 % of the rated load. 4.) Sensitivity: A snubber should get locked or produce large inertia force when the linear velocity of piping system supported by snubbers exceeds designed criteria. Or acceleration exceeds the design value. 5.) Dynamic Response: The peak to peak displacement across the unit, including end attachments, shall not exceed 1-30 -40 Hz, when input frequency is in 1 –33 Hz range at nominal load. 6.) Temperature: The snubber shall be designed for normal operation at 120 ° F. 7.) Humidity: The snubber shall be designed for normal operation at relative humidity of 25%. 8.) Corrosion Characteristics: The materials shall not promote corrosion under the operating conditions.
A second ago, you saw the schematic of a snubber in general. Here you see the schematic of a hydraulic snubber under normal conditions … Suppose the piping system moves right (shown by the white arrow). As the piston P1 moves forward, it pushes the fluid through the channels 1 and 2 . As long as the piston velocity, V<V critical , the valve V1 remains open. The fluid pushed by piston P1 flows uninterrupted through the channel, indicated by arrows. The fluid enters into the back of the main cylinder through port 5 and also to the compensating cylinder through port 3 . The same uninterrupted flow occurs through the valves and channel if the P1 rod moves in the opposite direction (in this case, the flow through the channel is reserved). Such movement occurs due to thermal expansion and contraction of the piping system. During this free movement, the breakaway drag is typically 1-2% of the rated load.
Here you see the schematic of a hydraulic snubber in “locked” condition … When subjected to movements that exceed the design velocity limits (which is typically 8 &quot; /min.), the valve is activated and is momentarily closed (this is shown by “X” as the piston moves forward). This is known as the “lock up” of the snubber. This forms a rigid connection between the piping system and the support structure. When the load has dissipated, the snubber “unlocks” and again allows gradual movement of the pipe and component. During the “lock up” state, a small amount of fluid is allowed to bleed either through a narrow channel (shown here as number 2) or through a separate channel in the valve itself.
By continuity Fluid equilibrium Never goes on back side
Here you see an exploded view of an hydraulic snubber In the middle, you see a high pressure main cylinder, which is offered in seven cylinder bore sizes: 1 1/2 to 8 inches. Selection of size depends on the anticipated force and thermal movement of the protected piping/equipment. Our hydraulic snubbers include a flow control section that contains dual stage velocity sensitive poppet valves All are made to include reservoirs in 6, 10, 15, or 20 inch strokes, except the 1 1/2 inch bore size. * The 1 1/2 inch bore size is offered only in 6 and 10 inch strokes. A spherical bearing allows for angular rotation of (plus or minus six degrees) ±6° to accommodate misalignment
Optional Design Features Include: Integral Relief Valve (Inside) – A non-adjustable valve which is factory preset at 133 percent or 200 percent of rated load. Protective Boot – The boot is installed over a piston rod for protection against corrosive or outdoor environments. The system’s movement is controlled by a flow control device, which can be designed adjustable if needed.
Pictured here are adjustable type Hydraulic Snubbers with two rear brackets, These snubbers were manufactured for an Power Plant in Turkey. Most snubbers have a fixed C – C dimension, but these are custom designed with a lock nut that locks in place after adjusting the length by removing the rod end screws in and out of the cylinder. The maximum load is 140,700 pounds and the stroke is 6 inches. The design temperature is 375 degrees Fahrenheit and the design pressure is 1,750 PSIG
Carbon Steel Hydraulic Snubber This Hydraulic Snubber has a maximum load of 225,000 pounds Three-Coat Paint System 14 ½ inch Diameter Weighs 4,000 pounds
Applications for Hydraulic Snubbers: Snubbers are used in piping systems or equipment when unrestrained thermal movement must be allowed under normal operations, but must be restrained during impulsive or cyclic disturbance. - They essentially restrain shock loading both in tension and compression. Special settings are available to absorb the continuous thrust resulting from safety valve blow-off or pipe rupture. For the most effective operation of the unit, please specify the mounting position, vertical or horizontal. Preferred usage with standard settings to prevent destructive results due to earthquakes, flow transients, or wind load. The unit is not effective against low amplitude, high frequency movement.
PT&P’s MSA series mechanical snubber operates on the principle of limiting the acceleration of any pipe movement to a threshold level of 0.02g. When a disturbance occurs that exceeds the threshold, the ball screw and drum produces angular momentum to the inertia mass. The inertial resistance of the mass engages the resilient capstan spring to tighten around a hardened mandrel, which is part of the structural tube. This in turn causes restraining force against rotation of the ball screw. During thermal compensation, the associated acceleration is far below the threshold limit of “g” (in other words, any slow movement will not activate the capstan spring). Prevalent Example: seat belt Complete arresting of motion
In addition to MSA mechanical snubbers, PT&P also designs and manufacturers dya/Damp mechanical snubbers. Pictured here is a very simple mechanical snubber using a singer verge with a rack-pinion arrangement. Depending on the load and configuration, the snubber becomes more complex with more numbers of oscillating verges and gears. Instead of locking, the dynA/Damp mechanical snubber produces increasing resisting inertia force with increasing input velocity produced by external force. It utilizes inertia force of oscillating verge(s) with connecting gearing, which limits the velocity of geared rack and thereby controls the rate of linear displacement of piping or other equipment systems. During normal thermal movements the rack is free to displace with relatively small resistance. Upon introduction of an external applied force— such as a seismic event— oscillation of the verge limits movement of the geared rack to a velocity proportional to the applied load. Since the snubber is always engaged, instant snubbing action assures positive displacement control of the connected piping or equipment system.
Mechanical Snubbers designed for a Refinery in Louisiana: The sizes range between 18 inches and 80 inches in length in the retracted position. The maximum load capacity is 700 to 10,000 pounds. These snubbers were tested at both high and low rates of loading on a computer controlled test machine. NOTE: general snubber specs
Mechanical Snubbers are: Maintenance free and can be placed in any orientation; including, vertical, horizontal or skewed. There are standard strokes readily available and can be used in series to increase the available travel range. The compact design of the mechanical snubber allows for small overall length. Sizes range from ¼ to 100, load rating is from 350 to 120,000 lb. and the standard maximum stroke ranges from 4 to 6 inches. Effective stroke of 12 inches
61 Mechanical Snubber Assemblies for a Power Plant in Southern California These assemblies are used to control a maximum shock load of 1,500 lb. within a piping system. Each Snubber was supplied with a custom designed yoke clamp made from Chrome-Moly (A387 Gr.91). Each snubber was also supplied with a stainless steel u-bolt and a protection saddle. The travel capacity range is 1&quot; to 5&quot;. An expedited delivery of two weeks was provided per customer's request.
Features of the Mechanical Snubber includes: Adjustable length for field fit-up Used in conjunction with a yoke clamp Allows movement in axial and translational directions Restrains all movement when a disturbance even occurs
Mechanical Snubbers designed for a Refinery in Louisiana: The sizes range between 18 inches and 80 inches in length in the retracted position. The maximum load capacity is 700 to 10,000 pounds. These snubbers were tested at both high and low rates of loading on a computer controlled test machine.
Under normal operating conditions: Snubbers are generally maintenance free Under severe service: Seals may become damaged, causing a loss of fluid, in this case, the snubber must be completely disassembled, new seals installed, and replenished with new fluid ** Severe Service usually involves excessive vibration or high temperatures ** If the snubber is damaged, contact us immediately for a replacement. If the snubber needs to be refurbished, remove the snubber from operation and send it back to us for maintenance and testing.
PT&P has two test machines specifically designed for testing snubbers for piping applications , one for routine testing of hydraulic snubbers, and a more sophisticated machine that can perform a wide range of tests on both hydraulic and mechanical snubbers. PT&P STADAS Snubber Test Machine The STADAS is a trailer mounted snubber test machine manufactured by Paul-Munroe Inc., California. This computer controlled, hydraulic test machine is used to test the performance of mechanical and hydraulic snubbers ranging in size from 150 pounds to 135,000 pounds. The STADAS may also be used to verify snubber conditions at the point of manufacture, or during an outage (refueling) at the plant site. The STADAS machine is capable of controlling a test, following any load sequence needed. It can then plot the test results immediately, and save the results to disk for future reference. The main frame of the STADAS machine is comprised of two drive cylinders, which supports the snubber being tested. The smaller drive cylinder is used for snubbers rated to 6,000 pounds, and the larger drive cylinder is used for snubbers rated up to 150,000 pounds. Each drive cylinder is equipped with an electro-hydraulic servo-valve, load cell and connections to the hydraulic system.
Hydraulic Snubber Test Machine The Hydraulic Snubber test Machine is mainly used to perform testing for hydraulic snubbers, it has a similar test bed like the STADAS machine, however, it is not computer controlled. It is adequate to perform all the tests normally required for hydraulic snubbers, such as quality control and periodic tests that are sometimes required as part of plant maintenance programs. Mechanical snubbers can also be tested on this machine, but due to the complication of the process, mechanical snubbers testing is usually performed on the STADAS machine.
Sway Braces are recommended for absorbing shock loadings; guiding or restraining the movement of pipe resulting from thermal expansion; bracing a pipe line against sway. Working principle is similar to variable springs (as movement increases; the restraint force increases) Can be utilized in tension or compression or a combination Standard sway brace sizes: - 3 &quot; of total travel in tension or compression - Load ratings from 50 to 7200 pounds
10 Sway Braces were designed and manufactured for a Petroleum Company in Louisiana… The total travel distance is 14 &quot;; t he standard PT&P braces have springs that allow 3&quot; of total travel distance. These sway braces were custom designed to provide a total travel distance of 5&quot; and 14&quot;. The center-to-center dimensions range from 92 ¼&quot; to 115&quot; with internal supports to prevent buckling. The desired spring rates for the sway braces is 450 lb./in. and 1,350 lb./in. The custom sway brace assemblies are comprised of pipes (for spring housing), springs (sizes dependent on spring rate and total travel) and in some cases, ball joints.
(load and travel) This is a 9 inch travel spring loaded sway brace.
Piping Technology & Products, Inc., Designed and Fabricated 126&quot; Long Sway Braces for a Power Plant These PT&P sway braces are fabricated from carbon steel and measure 126&quot; from pin to pin. They use an integral piston assembly with guide to eliminate any buckling and/or misalignment during extension and compression. The sway braces are designed for 10 1/2&quot; of travel and a load of 1,500 lb. A combination of standard spring coils is used to achieve the required spring rate of 150 lb./in. Prior to shipment, a test was performed using a hydraulic ram. This test simulated actual field conditions and allowed the sway brace to move through the entire travel range in both compression and extension modes.
(end connections and travel) ** Previously you saw Sway Struts with ball joints – Now we are showing sway braces with ball joints These Sway Braces were designed for a local refinery and are used to stabilize tall stacks. The deflection capability is (plus or minus nine inches) ±9” in all directions The Sway Braces in this project ranged from 71 inches to 144 inches in length and have a load capability of 8,000 pounds There are machined pivoting ball joints at each end that allow for freedom of movement in any unpredictable direction
- Travel test being performed on a sway brace for a client. - This is a specially designed sway brace designed for 14 inches of travel. - This sway brace uses an integral piston assembly with a guide to eliminate any buckling and/or misalignment during extension and compression. - Test was performed using hydraulic ram which simulated actual field conditions and allowed the sway brace to move through the entire travel range in both the compression and extension modes.
Sway Strut Assemblies: Rotate around pivot point (c - c dimension) Used to restrain movement of piping in one direction while providing for movement due to thermal expansion or contraction in another direction. They are effective for either tensile or compressive force. The self-aligning bushings permit (plus or minus five degrees) ±5° misalignment or angular motion. (clamp) Standard drawing of a sway strut assembly Clamp & end bracket 10 different sizes available with up to 68,200 pounds in maximum load ratings C – C dimensions can vary from a minimum of 16 ¾ inches to a maximum of 120 inches Fig. 2 Side view of end bracket Fig. 3 Options for end bracket Note: If unsure of the length, we can always provide one rod end loose for final fit-up in the field
Left: Measuring the c – c dimension Right: Prepared for shipping
Sway Strut Assemblies with Custom Designed 3-Bolt Pipe Clamps These sway strut assemblies are designed in conjunction with custom three-bolt clamps to prevent movement on a pipeline. The sway struts range in length from 25&quot; to 70&quot; from pin to pin. The operating load ranges between 8,000 lb. to 15,000 lb. The clamps are designed for pipe sizes ranging from 8&quot; to 24&quot;. The sway strut assemblies are fabricated entirely from carbon steel with a hot-dipped galvanize finish. The completed assemblies also include a custom 2-coat paint system that was applied over the galvanize finish before being shipped to an LNG plant overseas.
Size 5 & 6 sway struts Max loading of 35,500 Chrome moly and brackets Utilized for attachment at elevated temperatures
2 Chrome-Moly Sway Strut Hangers for a Power Generating Station in Iowa. (PT&P Ref #82417-C1, DS) 12/21/2005 These sway struts are made of ASTM A387 GR22 weighing at 1,485 lb. each. They are 6&quot; in diameter and 8'2&quot; long and are used for main steam valve supports with specifically designed spacers, pins, and retainers capable of restraining movement up to 90,000 lb. at high temperatures exceeding 750°F. The turnaround time for this was 6 weeks.
Ball-Joint Sway Strut Assemblies These Sway Strut Assemblies are 96 inches long and have a 20,000 pound load. There is a ball joint on each end connected by an extension rod to control piping system through complete range of thermal piping movements.
This Sway Strut is fabricated from carbon steel and is 6 inches in diameter with a 15,000 pound load. The Sway Strut includes a hot-dipped galvanize finish, a painted finish and will support a 30 inch process line in a refinery. This particular product was necessary because the current line only had a few I-beams for support and was not able to handle the large forces acting on the line. A heavy schedule pipe and heavier duty strut ends were necessary due to the heavy loads acting upon the pipe.
PT&P has a system of stock pipe supports and spring supports, as well as an “on-call” engineering and manufacturing team to meet any of your quick-turn and emergency needs.
That concludes our Webinar presentation on Shock Control Devices…. I hope everyone enjoyed the presentation and as a reminder, we have a staff of experts on snubbers, sway braces and sway struts standing by to answer any questions you may have. You can just chat them now while in session until 10:00 am CDT, or you can visit our discussion forum, just click on the blue graphic labeled “DISCUSSION FORUM” on the left hand side of our home page at www.pipingtech.com
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