Thrust restraint design for ductile iron pipe seventh edition dipra. The dynamic equivalent axial load for thrust ball bearings and thrust roller bearings with. If the basic rating life requirement is not met, the relubrication interval n should be shortened, or a larger bearing or rod end should be selected. Here are the features you will see with ebaa irons restraint length calculator rlc v7. Thrust block forces on pipe bends anchor due to liquid velocity and internal pressure online resulting force calculator sponsored links in a piping structure without adequately support fluid flow velocities and internal pressures may create intolerable forces and tensions. Thrust restraint design of dead ends, valves, reducers and. I will start by giving an overly condescending explanation of where thrust comes from. In efect, the thrust block transfers the load from the pipe to a wider load bearing surface. The dynamic equivalent axial load for this type of bearings is given by. When the bearing width is insufficient, one option is to upgrade the lumber used in the truss or truss bearing. A conventional thrust block at a block designed to transfer the thrust from the pipe into the undisturbed native soil. Thrust blocking is needed at all changes in size or direction. The drawing displayed is only for general representation and may not be identical to the selected bearing variant. In order to properly size thrust blocks or other devices to hold a pipe in place, the.
Skf uses cookies on our web site to align the information shown as closely as possible to the visitors preferences and to tailor our web site user experience in general. Worked example what bearing area of thrust block is required for a 160 mm pn12. A thrust bearing is either integrated with a specific main bearing assembly or independent of the main journal bearing. Romac thrust block restraintcalculatorhelp free download as pdf file. Allowable soil bearing pressure to the depth to the center of the thrust block is. Jul 31, 2012 the bearing strength of the soil is expressed in pounds per square foot. In this manner, the pipeline itself acts as a thrust block. With similar inputs as before, were now able to calculate the thrust block volume required, as well as determine the height and width. This program is based on the equations and procedures found in the dipra brochure thrust restraint design for ductile iron pipe.
Therefore, the area behind the thrust block must engage enough soil area to resist the resultant thrust force at a change in direction. These advantages are considered in the calculation of the basic. Any pipeline with restrained joints welded, flanged, victaulic, tytonlok, etc. Marine propulsion system, automation, transmission, hull, thrust block, stern tube. Jan 22, 20 this is the subject of thrust restraint and how a relatively simple subject seems to be confusing to so many, especially structural engineers.
If size of thrust block has not been specified by engineer, the following example shows steps required to determine the bearing area. Expanded calculator heres the new expanded thrust block calculator. Joint restraints offer alternative to thrust blocks. If any of the conditions on the standard detail cannot be met, then special design blocking is required as indicated below. Rating tool for concentrated livestock areas to determine if the area is a resource concern by calculating a rating at the edge of a concentrated livestock area and the end of a buffer. Math geometry physics force fluid mechanics finance loan calculator. Skf manufactures heavyduty spherical plain bearings with the multigroove feature in the outer ring bearings and rod ends requiring maintenance. Thrust block area design equations formulas calculator. To reduce the design time on each project, your manager has asked you to develop a trial calculation tool to identify the thrust block bearing area required for 60o pipe bends in the horizontal plane for a range of pipe sizes and discharges. Machine excavation of the thrust bearing surface should be discouraged. Improved understanding of the theory of lubrication films initially by reynolds allowed the development of much more efficient bearing surfaces.
Pressure pipe thrust block design f tee t 2pasin e2 bend ab t x sfsb ab bearing area of thrust block sq. Forces in a pipe bend in the horizontal plane are caused by the fluids momentum and pressure. See the engineers handbook for used calculation formulas and other instructions for designing plain bearings. Using the tables on the following page you can calculate the size of the thrust block for various pipe sizes. Calculate the thrust block area for a water pipe bend. The required bearing block area is then, for a horizontal bend, where s f is a safety factor usually 1. Thrust blocking prevents main line from moving when the pressure load is applied. Divide the total thrust by the bearing capacity of the soil in excavation from table 2 to determine the area in square feet of thrust block required to be in contact with the undisturbed soil.
The thrust block should be designed knowing the intensity of the thrusts developed in the pipe and the load bearing strength of the soil. Typical values for conservative horizontal bearing strengths of various soil types are listed in table 1. Bearing calculation formulas inventor 2016 autodesk. Conservative assumptions, along with an explicit safety factor, have been employed to assure a conservative design with an adequate overall safety factor. Area of thrust block, thrust force, soil bearing pressure formula. The unit system can be set only on the select bearing page. Thrust block is usually defined as a mass concrete block design to provide resistance by transferring the thrust force to the soil through a larger surface area of the block such that the.
Aw3d30 dem shows good accuracy particularly in relatively low lying area as compared to srtm 30. Romac thrust block restraintcalculatorhelp pipe fluid. Machine excavation of the thrust bearing surface should be discouraged because this method usually damages the bearing surface. Your hose at home has plenty of bends but it doesnt need thrust blocks. Thrust blocking installations the harrington corporation. Thrust block design calculator solving for allowable soil bearing pressure required given area of thrust block and thrust force.
Types of thrust blocks bearing gravity bearing thrust block bearing area ft 2 safety factor thrust force lbs bearing capacity of undisturbed soil lbsft2 undisturbed soil bearing area 45 45 soil bearing strength sb soil sb lbft2 muck 0 soft clay 1,000 silt 1,500 sandy silt 3,000 sand 4,000 sandy clay 6,000 hard clay 9,000. As an example, for a 90 degree bend in a 12inch ductile iron pipeline at 150 psi in a soil with a bearing strength of 2000 psf and a safety factor of 1. Plain bearing calculator inventor 2016 autodesk knowledge. The restrained length of pipe lr, along the run of the tee and on each side of the tee, encounters passive bearing resistance from the soil that acts perpendicularly to the tee. Divide 2 by the safe bearing capacity of the soil type against which the thrust block must bear. In some instances, the bearing area of the wall or beam may need to be increased.
The main aim of the design is to provide a bearing area of the block a b that will distribute the force against the soil such that the lateral. I have to put thrust blocks on a welded pe or steel pipe. As an example, for a 90degree bend in a12inch ductile iron pipeline at 150 psi in a soil with a bearing strength of 2000 psf and a safety factor of 1. If integrated, the thrust bearing area is present in the form of flanges that extend from the front and rear of the main bearing shells. Use the block calculators below to calculate the amount of materials needed.
Tee fittings require the restraint of all joints within a calculated length along the branch pipe. The bearing strength of the soil is expressed in pounds per square foot. Thrust blocks and anchors must be large enough to withstand the forces tending to move the pipe, including those of momentum and pressure as well as forces due to expansion and contraction. Thrust restraint design for buried piping common design guidelines 2008 c27. Calculate the total thrust by selecting thrust 100 by size and type of fitting from table 1 and multiplying thrust 100 by system pressure divided by 100. This is the area in which a thrust block would normally be poured. Thrust block design calculator solving for area of thrust block required given thrust force and allowable soil bearing pressure.
Thrust blocks allow a narrow point force to be spread and distributed across larger areas of soil down to a pressure that the soil can bear. Select bearing top click on select bearing to search for or add a bearing. Radius of pipe joint r in or mm bend deflection angle angle deg safe bearing value for soil a psf or nsm factor of safety fs output. Check the above table and you will find that the thrust developed on an 8, 90 bend is 9300 lbs. Bearing blocks are another way to deal with insufficient bearing area. The required bearing block area is then, for a horizontal bend, where sf is a safety factor usually 1. The extra large grease reservoir in those bearings extends relubrication intervals and bearing service life, especially in applications where there are constant direction loads.
Pressure thrust load is calculated by finding the area of the mean diameter of the bellows and multiplying it by the design pressure. To compute bearing areas for different test pressures and soil bearing stresses, use the following equation. The design was achieved by calculating the bearing area from the design. The next table lists the approximate soil bearing strengths. Jul, 2018 last week i introduced a new thrust block calculator and explored some of the concepts around the design and function of thrust blocks. Thrust blocks in water mains are created in the following ways. The soil types used in this program are divided into broad categories with varying properties. A similar approach may be used to design bearing blocks to resist the thrust forces at tees, dead ends, etc. Calculates plain bearings and designs and checks statically loaded radial plain bearings working under hydrodynamic lubrication conditions. The thrust block design is commonly determined by the equation a b s f ts b. Divide the total thrust by the bearing capacity of the soil in excavation from table 2 to determine the area in square feet of thrust block required to be in contact with the. Role of thrust blocks in order to prevent the internal pressure from forcing the pipe and fittings to separate, blocking or thrust blocks provide stability and allow the surrounding soil to accept the thrust force from the pipe assembly. Pressure pipe thrust block design utoledo engineering.
Where a b is the required bearing area of the thrust block, s f is the safety factor, t is the. The unit system section becomes read only on the other pages. Can be selected by entering the boundary dimensions inner dia. Required area t thrust p water pressure a cross sectional area of pipes interior required area is the amount of bearing surface that will be against undisturbed soil. Design of software for optimal calculation of anchor blocks in pipelines. A properly designed thrust block involves much more than dumping a load of concrete behind a bend.
The quantity of btus is calculated from the data entered for different energy sources. The fitting should be placed over a large enough area to keep stresses on the fitting at a minimum. In 1905, australian engineer george michell obtained a patent for the thrust block. Where ab is the required bearing area of the thrust block, sf is the safety factor, t is the resultant thrust force, and sb is the bearing strength of the soil. Question 4 50 marks the firm that you work for des. Thrust blocks are required where fittings are used to change the direction i. The idea is to automate the process of calculation and generation of 2d drawing of marine propeller shaft and its related components by programming and integrating the software such as spyder and rhinoceros using python language keywords. The force comes from the change in direction as the water goes around the bend.
Thrust block equations and formulas design calculator. Calculate the thrust developed at the fitting being considered 3. Based on 150 psi test pressure and a soil bearing pressure of 1500psf. The figure below the tables indicates methods required to calculate the thrust block area. This is accomplished by transferring the unbalanced force generated by changes in direction and changes in diameter to soil bearing and frictional resistance. This allowed the replacement of multiple collars in a thrust box by a single thrust block. The values of these two factors in the upper limit of the coloured area may be used for bearings with the multigroove system. The design of a restrained piping system is both simple and proven. Areas covered include construction practice, building design and materials. Question 4 50 marks the firm that you work for designs and constructs potable water distribution systems for local governments.
Area of thrust block, thrust force, soil bearing pressure. Thrustblock excel spreadsheet calculators engineers edge. Establish the maximum pressure to be applied to the line 2. Allowable soil bearing pressure to the depth to the center of the thrust block is area of thrust block required a min. Thrust restraint can be accomplished by using properly sized thrust blocks 1. How can i design thrust block for steel water pipelines. Jul 05, 2018 the calculator the tool below is an early part of a larger effort to determine the thrust block detailing. In order to properly size thrust blocks or other devices to hold a pipe in place, the momentum equation is used to compute the necessary resistive force to hold the pipe stationary. Area of thrust blocks for dead ends and tees shall be 0. The restraint design also requires the selection of a length of. Thrust restraint in pvc piping systems when using any gasketed pressure piping system, proper thrust restraint at valves and fittings is extremely important to the long term performance of the installation. Volume has been calculated assuming a triangular block shape with angles of 45 deg. T resultant hydrostatic pressure lbs sf safety factor 1. Typical thrust block arrangements download scientific diagram.
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