Thrust Restraints: 

When the pipeline is pressurized, unbalanced thrust force occur at bends, reducers, tees, wyes, bulkheads and other changes in line direction. These forces must be restrained in some manner to prevent joint separation. When the surrounding soil cannot provide this restraint, thrust or stress/thrust block must be used. Determination of need and design of these restraints is the responsibility of the owner’s engineer subject to the following limitations.

Al-Matin Fiberglass Pipe’s. Engineering Dept. can assist in designing the restraint.

Thrust Blocks:

Thrust block must limit the displacement of the fittings to 0.5% of the diameter or 6 mm whichever is less. The block must completely surround the fitting fo r its entire length and circumference and should be placed either against un-disturbed earth or back-filled with pipe zone materials as appropriate for the native soil characteristics.

These blocks are applicable to:

•   All bends, reducers, bulkheads and blind flanges.
•   Tees, when the branch pipe is concentric to the header pipe centerline.

Note: It is not necessary to encase nozzle connection in concrete.

Nozzles are tee branches meeting all the following criteria:

•    Nozzle diameter  ≤ 300 mm.
•    Header diameter ≥  3 times nozzle diameter.
•    If the nozzle is not concentric and/or not perpendicular to the header pipeaxis, the nozzle diameter shall be considered to be the longest chord distance on the header pipe wall at the nozzle/pipe inter-section.

Thrust Stress / Blocks:

Thrust/stress block must limit the dis-placement of the fitting to to that the coupling angles notations do not exceed the allowable . They must also restrict the radial deformation of the fitting to 0.5% of the radius of the respective pipe sections.

The block must completely surround the fitting for its entire length and circumference and should be placed either against un-disturbed earth or backfilled with pipe zone material as appropriate for the native soil characteristics.

These blocks are required for the following fittings when the line is ≥100 kPa (1 bar):

•   Tees, when the branch pipe is eccentric to the header pipe centerline
•   Lateral wyes
•   Bifurcations
•   Custom fittings as noted by special instructions

Pressure Class:

Pressure series are : PN ( 1 ,6 ,10  ,12 ,16  ,20, 25  and 32)   Bar

Stiffness Class :

The stiffness classes are : SN  (1250, 2500, 5000 and 10000) N/m² .

Diameter Range:

The nominal diameters covered by this specification are :

For large diameters fitting ( ND 2500)  please consult Al-Matin