1. Variable & Constant Spring Supports. Ajinkya Sande Roll No. – 01 Piping – Part Time - 58

2. Contents  Spring supports  Types of spring supports  Variable spring supports  Spring sizing of variable spring supports  Constant spring supports  Mechanism of constant spring support  Spring sizing of constant spring supports

3. Why to use spring supports?  Line operating at high temperatures is subjected to thermal expansion.  Spring supports provide continuous support during expansion or contraction of pipe.  Employs a spring element, which can get compressed or stretch-out depending upon the thermal movement of pipe and the corresponding loads.

4. Types of spring supports  Variable spring supports  Constant spring supports  Big ton springs  Sway braces  Snubbers

5. Variable Spring Supports  Generally recommended for non critical lines.  Supporting force varies with the spring deflection and spring scale.  Variation in supporting force is equal to the product of the amount of vertical expansion and spring scale.  Variation in supporting force results in additional stresses in piping system  Accepted amount of variation as per the codes is ± 25%.

6. Availability in Market Size 23 standard sizes 50 to 50000 lb load Types Type A,B and C Type D and E Type G Configuration Short Standard Double Triple Quadruple

7. Types of Variable Spring Supports Type A Used where it is desired to locate the spring hanger at a specific elevation

8. Types of Variable Spring Supports Type BType C Both these types are used where headroom is limited

9. Type DType E Provides for adjustments of the load from below the supporting channels by turning the turnbuckle. Provides for adjustment of the load by turning the nut at the top of rod shown above. Types of Variable Spring Supports

10. Used where the spring hanger must be placed under the piping to provide support from the floor or a structural member Type F

11. Types of Variable Spring Supports Type G Used where head room is insufficient to accommodate the spring hanger and the necessary associated hardware

12. Configurations of Variable Spring Supports

13. VARIABLE SPRING SUPPORTS: LOAD AND TRAVEL TABLE

14. Basic Steps in Spring Hanger Design 1)Determine location of spring hangers from isometric drawing. 2)Calculate hanger loads due to pipe weight at each hanger location. 3)Calculate thermal movement of piping system at each hanger location

15. Spring Sizing  Available Data :- Hot load : 1650 kg, Cold load : 2000 kg Thermal expansion : 12 mm  Locate the loads on the load & travel table and select -- Spring rate : 14.29 kg/mm -- Hanger size : 140  Check Spring Variability: Variability = (spring rate x Thermal Expansion ) / Hot load = (14.29 x 12 ) / 1650 =0.1039 = 10.39% ≤ 25%  Thus the selected Variable Spring Hanger is of Standard configuration with spring rate of 14.29 kg/mm.

16. Constant Spring Hangers  Only recommended if the line is critical.  Geometry and kinematics of constant spring hangers is such that theoretically constant supporting force can be achieved throughout its full range of expansion contraction.  Cost is more than that of variable spring hanger.  Space required is more due to its geometry.

17. Mechanism of Constant Spring Hanger  Consist of helical coil spring and bell crank lever.  Spring force x distance = pipe load x distance from pivot from pivot  Counter balancing of load and spring movement is obtained which results in contant supporting force.

18. Availability in Market Size 1 – 100+ Types Type A,B and C Type D,E,F,G & U Configuration VERTICAL HORIZONTAL

19. Spring Sizing  Available Data :- Hot load, Cold load & Thermal expansion  Total displacement = thermal expansion + (1’’ or 20%)  Determining the size from load & travel table.  Consideration of available room for suspending the pipe and hanger will indicate whether a vertical or horizontal hanger is desirable.

20. Thank You