**Related Resources: hardware**

### Bolt Elongation Formula and Calculator per. ASME PCC-1

Pressure Vessel Design Formula and Calculators Resources

Fastener and Screw / Bolt Design, Formula & Calculations

Bolt Elongation Formula and Calculator per. ASME PCC-1

When bolt elongation (bolt stretch) measurement is selected as the load-control technique to be used, the required bolt elongation is computed according to the following equation (assumes the bolt is threaded full length):

Equation 1

ΔL = [ ( S_{b} · L_{eff} ) / E ] · ( A_{r} / A_{ts} )

Equation 2 (Metric Threads)

A_{ts} = ( π / 4 ) ( D - 1.3 · P ) / 2

Equation 3 (ANSI Inch Threads)

A_{ts} = ( π / 4 ) ( D - 1.3 / n ) / 2

Where:

A_{r} = root area (minor diameter), mm^{2} (in.^{2})

A_{ts} = tensile stress area, mm^{2} (in.^{2}).

n = threads per
inch

P = thread pitch

E = modulus of elasticity, MPa (ksi)

L_{eff} = effective stretching length, mm (in.). The conventional
assumption is that the effective
stretching length in a through-bolted joint system
is the distance between mid-thickness of
the nuts, where the nominal thickness of a
heavy hex series nut is one nominal bolt diameter.
By the same standard, the effective length
of the portion of a bolt that is studded into
a tapped hole is one-half of a nominal bolt
diameter.

S_{b} = Target Bolt Stress (root area), MPa (ksi). It is
noted that bolt stresses computed in accordance
with Mandatory Appendix 2 of
Section VIII, Division 1 of the ASME Boiler
and Pressure Vessel Code are based on root
area. If Target Bolt Stress (tensile stress area)
is used, drop the A_{r} / A_{ts} term from the ΔL
computation.

ΔL = bolt elongation (bolt stretch), mm (in.). Select
a tolerance on this computed value and include
it in the joint assembly procedure.

Related:

- Bolt Elongation Equation and Calculator while under Axial Stress
- Fastener, Bolt and Screw Design Torque and Force Calculation
- Bolt Preload Tension Calculator and Force Equation
- Moment Effect on the Bolts Circular Distribution in the End-plate Connection
- Screw Thread Size Chart
- ANSI Hardware Design Guide
- Metric Hardware Specification Charts and Tables
- Fastener Threaded Shear Area Equation and Calculator ISO 898

Reference:

Guidelines for
Pressure Boundary
Bolted Flange Joint
Assembly

ASME PCC-1-2010