Hangers And Snubbers

Question 1

Describe the types of strains and movement experienced by plant systems?

Answer 1

-Weight of piping
-Fluid in piping
-components weight (valves)
-Pressure and temp. expansion and contraction
-Movement caused by flow changes or pressure surges (water hammer)

Question 2

State the purpose of Hangers

Answer 2

-Hangers support piping systems
-Prevent damage by compensating for strains and movements

Question 3

Describe the different types of hangers

Answer 3

-Flexible allowing for vertical movement due to thermal expansion
• constant support
•Variable support

-Rigid
•no vertical movement
•attachment point to structure for support of piping system

-Snubbers
•special type of hanger
•used on more complex systems to slow movement of piping

Question 4

Explain basic operation of Mechanical snubbers

Answer 4

Operate by:
•Ball screw shaft and spring mechanism
Or
•Verge and rack assembly

-Provide a breaking action limiting the axial movement to the max safety acceleration

Question 5

Explain the basic operation of hydraulic snubbers

Answer 5

Two types:
•2 RCP snubbers on each RCP
•2 S/G snubbers on each S/G

•Two ports allowing flow for regular movement

•Those ports close when movement accelerates too quickly

Question 6

Describe failure modes and symptoms of hangers and snubbers

Answer 6

HYDRAULIC
•After severe service(earthquake, water hammer)
•damaged seals
•loss of hydraulic fluid

MECHANICAL
•improper assembly
•over heating from welding
•dirty/corroded
•improper lube

Question 7

Purpose of Snubbers

Answer 7

-Restrain movement during seismic event, unit trips.
-Ensure safety systems can still perform safety functions
-Ensures good movement during normal operations

Question 8

Different type of snubbers

Answer 8

-Mechanical
•Limit acceleration

-Hydraulic
•Limit velocity