Process Equipment and Plant Design
A stuffing box is used for

Absorbing the contraction/expansion of pipeline due to temperature changes
Reducing the resistance of fluid flow
Prevention of fluid leakage around moving parts
Facilitating smooth opening and closing of a valve

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Process Equipment and Plant Design
Triangular pitch tube layout as compared to square pitch in a shell and tube heat exchanger

Both B and C
Permits the use of more tubes in a given shell diameter
Facilitates comparatively easier external cleaning because of large clearance
Permits the use of less tubes in a given shell diameter

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