Fronek Anchor/Darling, a division of PT&P, designed and manufactured hydraulic snubbers for Geothermal power plants. Historically, these plants are located near tectonic plate boundaries in the Earth’s crust where thermal activity is easily tapped into. This heat energy is transferred into electrical energy through the use of turbines, generators, and heat exchangers. These snubbers are fabricated from stainless steel and include a special paint system suitable for a Hydrogen Sulfide (H2S) environment. All the snubbers for this application were a 2-1/2 bore size, capable of operating at loads up to 10,000 lb., and were provided with either 6″ or 12″ of available stroke. The Pin-to-Pin dimensions ranged from approximately 36″ to 54″ Each snubber was tested at its rated capacity to assure acceptable dynamic performance once it is installed in the field.
|Design:||3,000-15,400 lb load/5″-12″ stroke|
|Size:||31″ up to 148″ pin-to-pin and cylinder diameters from 2.5″ to 5″|
Piping Technology & Products designed these hydraulic snubbers for an ammonia plant in Louisiana. The snubbers ranged in length from 31″ up to 148″ pin-to-pin and cylinder diameters from 2.5″ to 5″. They are designed for an operating load raging from 3,000 lb. to 15,400 lb. and have a 5″ to 12″ stroke. Hydraulic snubbers are designed to protect the piping system when a sudden, heavy load is applied (such as an earthquake of high intensity), which can cause serious vibrations leading to damage and possible failure of the piping system.
Most hydraulic snubbers have a piston which is relatively unconstrained in motion at low displacement rates. At high displacement rates the piston “locks up” and acts as a rigid restraint.
When the velocity of the piston reaches a certain value (about 8in/min),the hydraulic valve will shut off and the entire system is locked. i.e. that isthe piston movement is arrested.
A snubber is a shockabsorber, it stops all movement caused by a sudden transient (emergency) loadin a pipe system.A sway brace is ashock arrestor, it dampens the load and reduces the overall movement.A sway strut stopsall movement and transfers it into the pipe structure.
Large Sway Brace
A mechanical snubber is a device that permits pipe deflection under normal operating conditions, but when subjected to an impulse load, such as an earthquake, waterhammer, etc., the snubber becomes activated and acts as a rigid restraint to restrict pipe movement as a result of the unwanted impulse loading.
A mechanical snubber uses gears and springs to produce the restraint force when activated.
Hydraulic snubbers are designed with a pre-defined amount of stroke. Those stroke ratings are available in 6 inch increments from 6″ to 24″. The amount of movement, which could be accommodated by any stroke designation, would depend upon the initial setting. For example, setting a 6″ stroke snubber at the midpoint would mean that during operation, the snubber could extend 3″ maximum or retract 3″ maximum.
Hydraulic Snubbers with Protective Boots
Field testing of snubbers is not recommended. In order to accurately confirm the function of a snubber, a certified test machine must be utilized to accurately simulate impulse loading.
Hydraulic Snubber Being Tested on the STADAS Test Machine
The main criteria to remember when utilizing snubbers is that they are intended to be passive elements during normal operation and will become activated only when that unwanted impulse event is present. When that impulse event dissipates, the snubber will become deactivated and thus produce negligible restraint to pipe deflections under standard operating conditions.
Mechanical Snubber Installed in the Field
Because snubbers are not meant to be active support components, they could be installedat any time during the construction phase. It should also be noted that pipingsnubbers can be retrofit to existing systems at any time.
Close Up View of Hydraulic Snubber Installed in the Field
A shocksuppressor is another name for a snubber, which is a device that permits pipedeflection under normal operating conditions, but when subjected to an impulseload, such as an earthquake, water hammer, etc., the snubber becomes activatedand acts as a rigid restraint to restrict pipe movement as a result of theunwanted impulse loading.
Mechanical Snubber Assemblies
Pipe supports can be classifiedaccording to both their level of engagement (active or passive) and function(load-bearing, guiding, or anchoring).
We designate support configurationswhose primary capabilities are always engaged as active, whereas passivesupport configurations simply follow the movement of the pipe during normaloperation. However, disturbances such as severe weather, impact, abnormalvibration or seismic events, will activate these otherwise passive supports,which then function as active anchoring devices.
Pipe support functions include loadbearing, guiding, or anchoring. A load bearing support will uphold the weightof the pipe while allowing possible movement in all three dimensions. A guidewill uphold the weight of the pipe while restricting movement in up to twodimensions. An anchor will completely restrict pipe movement in all threedimensions while bearing the weight, side, and thrust loads.
Hydraulic Snubber Assemblies – Passive Supports
These hydraulic snubber assemblies were designed with maximum load capacities ranging from 1700 lb. to 59,400 lb. All of the snubbers were provided with an overall stroke of 6” and were preset to the midpoint of the total stroke, meaning that during operation, these snubbers could accommodate piping deflections of +/- 3” from the installed position.
The piston diameters range from 1-1/2″ to 6″ and the total assembly length ranges from 31-1/2″ to 220″. The largest assembly required a custom extension section to eliminate the risk of buckling under compression loads. Two-thirds of the assemblies included dual end brackets and the remaining assemblies included an end bracket/clamp combination. The housing, extension piece and end brackets are fabricated from carbon steel, while the cylinders, pins and two of the end brackets are fabricated from polished stainless steel. Standard “lock and bleed-down” tests were performed prior to shipping to a LNG processing facility in Peru.
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Anchor/Darling Enterprises, Inc., a wholly owned subsidiary of Piping Technology & Products, Inc. designed and fabricated these hydraulic snubbers for a power plant in Turkey. They are adjustable type snubbers with two rear brackets. The hydraulic snubbers can absorb loads up to 140,700 lb.
Pressure: 1,750 PSIG
Sizes of mechanical snubbers for this project range between 18″ and 80″ in the retracted position. The maximum load capacity ranges between 700 and 10,000 lb. Mechanical snubbers function to restrain thermal movement in abnormal circumstances such as earthquakes, hydraulic hammer, and upstream pipe rupture. The snubbers were tested at both high and low rates of loading on a computer controlled hydraulic test machine to ensure quality assurance.
Snubbers are restraining devices. They allow free thermal movement during normal operations but restrain in abnormal circumstances such as with an earthquake. These snubbers were fabricated from carbon steel. They measure 2 1/2” x 24” and the yoke clamps have pipe sizes of 23” and 25”. Each snubber weighs 890 lb. and has a travel capacity of 24”. Designed for the support of a cryogenic line, these snubbers can handle loads of up to 2,900 lb.
Piping Technology & Products, Inc., recently designed and manufactured fourteen PTP Fig. 2100 Hydraulic Shock Suppressor and pipe hanger assemblies for a Steel Company in North Dakota. The assembly consists of a 12 diameter alloy clamp and a PTP Fig. 2100 Hydraulic Snubber with cylinder size of 3 1/4 diameter and 5 stroke load. They are designed to accommodate loads of 25,000 lb. and high temperatures up to 1,100 F. To ensure the products quality, dimension and movement tests were conducted prior to shipment.
PT&P also designed and manufactured Variables Spring Hangers and various Pipe Supports Assembly Components in a range of different specifications and materials for this project.
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Piping Technology & Products, Inc. recently designed and manufactured a hydraulic snubber weighing 4000 pounds for an oil refinery in Mexico. The snubber is fabricated from carbon steel with dimensions of 17 x 101. It supports a maximum load of 225,000 lbs. The purpose of the hydraulic snubber is to reduce shock loading created by events such as water hammer or an earthquake. To meet customer specifications, the hydraulic snubber was coated with a three-coat paint system.
Piping Technology & Products recently designed and manufactured four fig. 2100 hydraulic shock snubbers for a refinery in California. Carbon steel was used to manufacture these snubbers. They support a maximum load of 14,000 lbs., have a 3” cylinder, and 5” stroke load. This was a custom job where the customer provided the figure number, cylinder size, and stroke load; we built the snubbers according to these specifications.