Fittings shall be extra heavy pattern where pressure is ______ psi or more.

Fittings shall be extra heavy pattern where pressure is ______ psi or more.

• A. 125
• B. 150
• C. 175
• D. 200

Answer: (C)

High-pressure service demands sturdier fittings. Extra heavy pattern fittings have thicker walls and a tougher shape to resist the higher hoop stresses on the pipe and the greater loads at the joints. The standard sets the switch to extra heavy when pressure reaches 175 psi or more because, beyond that point, a regular pattern can start to fail or leak under operating and surge conditions. So at 175 psi and above, extra heavy is required. (Note: anything below that can use a lighter pattern; and 200 psi would also fall under the same requirement since it’s above the threshold.)

High-pressure service demands sturdier fittings. Extra heavy pattern fittings have thicker walls and a tougher shape to resist the higher hoop stresses on the pipe and the greater loads at the joints. The standard sets the switch to extra heavy when pressure reaches 175 psi or more because, beyond that point, a regular pattern can start to fail or leak under operating and surge conditions. So at 175 psi and above, extra heavy is required. (Note: anything below that can use a lighter pattern; and 200 psi would also fall under the same requirement since it’s above the threshold.)