line sizing slides

8/11/2019 Line Sizing Slides

1/22

31% of large property damage

losses are caused by failures inpiping systems.

Some lines reach 60 inches indiameter - larger than manyequipment items.


2/22

MB & EB balances must include: Normal mass balance - base case.

Start-up, shut down or upsetdevn.

Recycle of off-spec products.

Equipment bypass conditions.

MB for flare, fire water, sewers,

steam, condensate and CTWheaders.


3/22

Limiting line velocities notknown or ignored.

Velocity greater than 15 fps in CSpipe can cause erosion.

Low velocities (< 3 fps) can cause

entrained solids to settle and pluglines.


4/22

Poor record keeping during Phase 3prevents detailed follow-up inPhase 4 design stage.

PSV lines need to be checked inPhase 4.

Pump lines need to be checked inPhase 4.


5/22

Corrosiveness of fluid unknown.

At high temps, degradation mayproduce acidic components. (La.

HumbleTherm example). Pipe not suitable for unexpected

cold temperatures.

Pipe not suitable for unexpected

extreme high temperatures.


6/22

Compressible fluid flow not well

understood by process engineers. Flows at Mach 1 (Sonic Flow) can

be destructive.


7/22


8/22


9/22

Two Phase Flow not well

understood by process engineers. Horizontal Flow - Baker Chart.

Vertical Down Flow.

Vertical Up Flow.


10/22


11/22

Siphons may form readily May have damaging pulsating

flow


12/22


13/22

May have damaging pulsating

flow 4 ft. dia. Cooling tower inlet pipe

experiences severe vibration, fails& floods plant


14/22


15/22

Two phase flow pressure drops

may be higher than expected andthereby limit performance.


16/22

Flashing liquids often not

considered during processdesign.

Two phase flow can be acomplex, transient problem.


17/22

PSVs are usually sized for single

phase flow. Two phase flow can occur when

vessels operated above maximumfill limit.

Two phase flow can occur whenflows are higher than expected.


18/22

Draining water from KO Pot toopen sewer during rain storm.

Flammable vapor entrained dueto formation of liquid vortex.

Lightning strikes near plant ISBL. Sewer explodes, wrecks cold box

in Ammonia Plant.

One operator killed.


19/22

Flow in reactor manifolds.

Flows in branched piping. Flows in shell-side of exchangers.


20/22

System or vessel design pressuresexceeded when EBV suddenlystops flow.

EO transfer example.

See computer spreadsheet design

program.


21/22


22/22

Which flow regime should youavoid for horizontal, two phaseflow?

If a liquid vortex forms on drainingfrom a vessel, what safety problemscan this create?

When can a PSV which is sized for

single phase flow experience twophase flow?

line sizing slides

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