Thrust Block Velocity (Kinetic) Thrust - …

1 Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe SystemsdesignThrust BlockSupportsPE pipes and fittings joined by buttwelding, electrofusion, or other end loadbearing joint system do not normallyrequire anchorage to withstand loadsarising from internal pressure and joint types which do not resist endloads, plus fabricated fittings whichincorporate welded PE pipe segments,anchorage support must be provided inorder to prevent joint or fitting failure. Inaddition, appurtenances such as valves,should be independently supported inorder to prevent excessive shear loadsbeing transferred to the PE Pressure ThrustwhereR = resultant Thrust (kN)P = pressure (MPa)A = area of pipe cross section (mm2) = angle of fitting (degrees)For blank ends, tees and valvesR = PA 10-3 For reducersR = P(A1 - A2) 10-3R=2PA.

2 Sin .10-32R= .10-92 Soil TypeSafe Bearing Capacity(N/m2)Rock and sandstone (hard thick layers)100 x 105 Rock- solid shale and hard medium layers90 x 104 Rock- poor shale, limestone24 x 104 Gravel and coarse sand20 x 104 Sand- compacted, firm, dry15 x 104 Clay- hard, dry15 x 104 Clay- readily indented12 x 104 Clay/Sandy loam9 x 104 Peat, wet alluvial soils, siltNilVelocity (Kinetic) ThrustThe Velocity or kinetic Thrust applies onlyat changes of = fluid density (kg/m3)a = inside pipe cross section area(mm2)V = flow Velocity (m/s)The Velocity Thrust is generally small incomparison to the pressure pressure used in the calculationsshould be the maximum working, or testpressure, applied to the Loads of SoilsThe Thrust developed must be resistedby the surrounding soil. The indicativebearing capacities of various soil typesare tabulated below:The figures in the table below are forhorizontal thrusts, and may be doubledfor downward acting vertical thrusts.

3 Forupward acting vertical thrusts, theweight of the Thrust Block mustcounteract the developed shallow (<600mm) cover installationsor in unstable conditions of fill, the soilsupport may be considerably reducedfrom the values tabulated, and acomplete soil analysis may be Warehouse Group Pty 1300 661 417PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe BlockSize Calculations1. Establish the maximum pressure tobe applied to the line2. Calculate the Thrust developed at thefitting being considered3. Divide (2) by the safe bearingcapacity of the soil type againstwhich the Thrust Block must ExampleWhat bearing area of Thrust Block isrequired for a 160 mm 90 bendin hard, dry clay?1. Maximum working pressure pipe is pressure is x WP= Bearing capacity of hard, dry clay is15x104 N/m2 Thrust blocks may be concrete or cast insitu concrete is used, anadequate curing period must be providedto allow strength development in theconcrete before pressure is introduced tothe pipeline.

4 Where timber blocks areused, test pressures may be introducedimmediately, but care needs to be takento ensure that the blocks will not rot andwill not be attacked by termites or area of Thrust x 104215 x 10= Thrust BlocksClosed end and hydrant anchorageValve anchorageBend in vertical plane anchorageBend in horizontal plane anchorageTee anchorageR= .102= x10-4-3 NIrrigation Warehouse Group Pty 1300 661 417