Choosing a Line Size and Wall Thickness

8/12/2019 Choosing a Line Size and Wall Thickness

1/20

CHOOSING A LINE SIZE AND WALL THICKNESS


2/20

LESSON OUTCOMES

At the end of todays lecture, students shouldbe able to:

Describe effect of velocity to size liquid, gas andtwo-phase pipelineDetermine ID using velocity equationsDescribe standards and requirements used to

calculate wall thickness of pipeDetermine wall thickness of pipe using standards.


3/20

LECTURE OUTLINE

Selection criteriaLine size criteria focus on VELOCITY

Wall thickness criteriaExample


4/20

SELECTION CRITERIA

TWO-PHASE LINE

LIQUID LINES

GAS LINES

VELOCITY PRESSURE DROP

LINE SIZE

ANSI B 31.1 ANSI B 31.3 ANSI B 31.4

LOCATION CLASS1,2,3 AND 4

TEMP DERATING

FACTOR,T

DESIGN FACTOR,F

ANSI B 31.8

STANDARDS ANDREQUIREMENTS

WALL THICKNESS

SELECTION CRITERIA


5/20

LINE SIZE CRITERIA

PRESSURE DROPImportant for long flowlineImportant for flowline between equipment operatingat the same or nearly the same pressure

Equivalent length and elevation changes to beconsidered

VELOCITY

Below maximum to prevent erosion, noise or waterhammer Above minimum to minimize surging and transportingsand or solid particles


6/20

LINE SIZE CRITERIA (contd..)

Erosional Flow

Liquid droplets impact the wall with enough forceto erode the metal and exposing it to the fluidand allowing more corrosion to occur

Fluid erosion occurs when V > 21)( m

e

C V


7/20

LINE SIZE CRITERIA (contd..)

LIQUID LINEGAS LINE

Max velocity 15 ft/s and min velocity is3 ft/s

Sized to maintain avelocity sufficient tokeep solid particlesfrom depositing

Fluid velocity in oilfieldunit:

Max velocity 60-80 ft/s and min velocity is

10-15 ft/s Sized to minimize liquid

settling out and effect ofnoise and corrosion

Pressure less than 1000psi, erosional velocity isnot significant

Gas velocity in oilfieldunit:

VELOCITY

2

1012.0d Q

V P d

TZ QV g 260


8/20


9/20

Standards and Requirement

ANSI B 31.3 - Power Piping.This standard deals with steam and is required by the U.S Coast Guard onall rigs

ANSI B 31.3 Chemical Plant and Petroleum Refinery Piping.This standard is required by the US Minerals Management Service foroffshore platform in federal, state waters and offshore facilities in otherparts of the world

ANSI B 31.4 Liquid Petroleum Transportation Piping System.This standard is normally used in onshore oil production facilities

ANSI B 31.8 Gas Transmission and Distribution Piping System.This standard is normally used for gas lines in onshore productionfacilities and when transporting or distributing gas.

WALL THICKNESS CRITERIA


10/20

General Hoop Stress Formula for ThinWall Cylinders

WALL THICKNESS CRITERIA


11/20

WALL THICKNESS CRITERIA (contd..)

ANSI B 31.3

Tol PY SE

Pd t t t o

thc

100

100

)(2


12/20


13/20


14/20


15/20

WALL THICKNESS CRITERIA (contd..)

ANSI B 31.8

)(2 FETS Pd

t o


16/20


17/20


18/20


19/20

STEPS TO CHOOSE A LINE SIZE AND WALLTHICKNESS

i. Determine the max and min velocityallowable for specific fluid types

ii. Find pressure drop of the systemiii. Determine the I.D of pipe relative to the

velocityiv. Determine pressure drop in the pipeline

v. Find the wall thickness based on thestandard vi. Choose the appropriate pipeline size from

the standard


20/20

EXAMPLE CALCULATION

A gas with specific gravity of 0.85, viscosity of 3 cp and compressibilityfactor of 0.67 flows at a rate of 23 MMscfd in a pipeline.

The pipeline is laid at Gobi Desert.

The inlet pressure of the gas is 900 psi at a temperature of 80 oF.

The length of the pipeline is 7000 ft.The gas flows to a dehydrator that operates at 800 psi. The rated pressure ofthe pipeline is 1480 psi. The pipe is seamless and the minimum yieldstrength is 35000 psi.

Determine the appropriate line size and wall thickness based on ANSI B 31.8

Choosing a Line Size and Wall Thickness

Documents

Transcript of Choosing a Line Size and Wall Thickness