revalidating requirements: rigging hardware case study

Anthony Underhill321-730-6269anthony.underhill@mantech.comcapt_underhill@yahoo.com

WHY DOES THE SAFETY REQUIREMENT EXIST?

“We’ve always done it that way?”

How was the requirement validated?

What were the circumstances at the time?

Is the requirement still relevant (effective) in today’s environment?

SHACKLE FOR CRITICAL LIFT APPLICATION

  AFSPCMAN 91-710 ASME B30.26

Initial Proof 2 x Rated Load 2 X Rated Load*

Post Proof Inspection Volumetric & NDE Visual

Periodic (annual) Proof 2 x Rated Load Not Required

Periodic (annual) Inspection

NDE(Dye Penetrant)

(Magnetic Particle) Visual

FAST FORWARD TO TODAY

Facility Cost ⇒ $110K annualUser Mission Cost ⇒ $ 34K per mission

TOTAL COST ON Eastern Range = ~$1M per year

BUT IS IT MORE SAFE?

US NAVY – high number of accidents◦ Causes: Uncertainty in the load

High corrosion environmentNo Consensus standard for

design◦ Solution: Annual 2 x rated load test

OSHA in its infancy

US Air Force Range◦ Adopt 2 x RL in ESMC (1984)

1970 2000

Weak OSHA Strong OSHA

Inconsistent Design FOS Consensus FOS

Various materials Specific Materials

2 x rated test solution 2 x rated test solution

WHAT DOES ASME SAY ABOUT 2 x RL TESTING?

Do not recommend exceeding 42% yield strength or fatigue may occur (ASME B30.20 interpretation)

Does annual 2 x RL proof increase safety?

Are Magnetic Particle or Dye Penetrate inspections required to find critical flaws?

10 Fatigue Rated shackles failed in fatigue when subject to 2 x RL

BUST

E

D

Failed @ 2.87 x RL Failed @ 1.28 x RL

Failed @ 1.87 x RL Failed @ 2.28 x RLBUST

E

D

Chance of improperly tested Change of damage during installation Change of damage during installation

REVISIT YOUR SAFETY REQUIREMENTS

REVALIDATE THEY ARE FULLFILLING THEIR INTENDED PURPOSE

◦ YES – ENFORCE THEM◦ NO – CHANGE THEM