LESSON

1LECTURE

PIPES

SUB-OBJECTIVE

At the end of this lesson, the trainee will be able to understanding of Pipes and Pipe Dimensions.

1.0 INTRODUCTION

Commercial pipe and tube products are grouped into various classification generally based on the application or use and not on the manufacturing method.

2.0 CLASSIFICATION

Most tubular products fall into one of three very broad classification.

a. Pipeb. Pipe pressure tubesc. Mechanical tubes

Each classification falls into various sub-grouping which may be defined and standardized differently by the different trade or user groups. On the basis of user classification, the more commonly used types of pipe are tabulated in Table 1-1. This listing ignores method of manufacture, size range wall thickness, and finish.

SPECIFIC MECHANICAL COURSE FOR ENGINEERSLESSON 1 PAGE 1 PIPE COMPONENT AND ANCILIARY EQUIPMENT

Table 1-1. Major Pipe classifications and examples of application.

Type of pipe Uses

Standard Mechanical (structural) service pipe, low-pressure service pipe, refrigeration (ice machine) pipe, ice-rink pipe, dry-kiln pipe.

Pressure Liquid, gas or vapor service pipe, service for elevated temperature or pressure, or both

Line Threaded or plain ends, gas, oil, and steam pipe.

Water well Reamed and drifted, water-well casing, drive pipe, driven well pipe, pump pipe, turbine pump pipe

Oil country tubular goods Casing, well tubing, drill pipe.Other pipe Conduit, piles, nipple pipe, sprinkler

pipe, bed stead tubing.

2.1 STANDARD PIPE

Mechanical service pipe is produced in three classes of wall thickness.

a. Standard weightb. Extra strongc. Double extra strong

2.2 PRESSURE PIPE

Pressure pipe is used for conveying fluids or gases at normal, subzero, or elevated temperatures or pressures. It generally is not subjected to external heat application. The range of sizes is 1/8 in. nominal size to 36 in. actual outside diameter in various wall thicknesses. Pressure piping is furnished in random lengths, with threaded or plain ends, as required. Jointers are not customarily produced. Pressure pipe generally receives a hydrostatic test by the mill.

2.3 LINE PIPE

Line pipe is welded or seamless pipe produced in sizes from 1/8 in. nominal OD to 36 in. actual OD, inclusive. It is used principally for conveying gas, oil, or water. Line pipe is produced with ends plain, threaded, beveled, grooved, flanged, or expanded, as required for various types of mechanical couplers or for welded joints. When threaded ends and couplings are required, recessed couplings are normally supplied.

SPECIFIC MECHANICAL COURSE FOR ENGINEERSPIPE COMPONENT AND ANCILIARY EQUPMENT LESSON 1 PAGE 2

2.4 WATER-WELL

Water-well pipe is welded or seamless steel pipe used for conveying water for municipal and industrial applications. Pipelines for such purposes involve flow mains, transmission mains, force mains, water mains, or distribution mains. The mains are generally laid underground. Sizes range from 1/8 to 96 in. in a variety of wall thicknesses. Pipe is produced with ends suitably prepared for mechanical couplers, with plain ends beveled for welding, with ends fitted with but straps for field welding, or with bell-and-spigot joints with rubber gaskets for field joining. Pipe is produced in double random lengths of about 40 ft. single random lengths of about 20 ft. or in definite cut lengths, as specified. Wall thicknesses vary from 0.068 in. for 1/8 in. nominal outer diameter to 1.00 in. for 96 in. actual outer diameter.

When required, water-well pipe is produced with a specified coating or lining or both. For example, cement-mortar coatings are extensively used.

2.5 OIL COURTRY GOODS

Casing is used as a structural retainer for the walls of oil or gas wells and is also used to exclude undesirable fluids, and to confine and conduct oil or gas from productive subsurface strata to the ground level. Casing is produced in sizes 4 ½ to 20 in, outside diameter inclusive. Size designations refer to actual outside diameter and weight per foot. Ends are commonly threaded and furnished with couplings. When required, the ends are prepared to accommodate other types of joints.

3.0 PIPE SELECTION

Many pipes of different diameter and thickness are used in power and desalination plant. They are selected mainly by the following parameter.

a. Fluid characterb. Flow rate and flow velocityc. Pressure

For above selecting parameter we must know about the standard pipe size or diameter wall thickness and pipe schedule number.

3.1 DIAMETER

Up to 12 inches pipe size coming with it nominal pipe size. The nominal outside diameter is standard, the increase in wall thickness results in a decrease of the inside diameter.

The standardization of pipe size over 12 inches, is based on the actual outside diameter.

SPECIFIC MECHANICAL COURSE FOR ENGINEERSLESSON 1 PAGE 3 PIPE COMPONENT AND ANCILIARY EQUIPMENT

3.2 WALL THICKNESS

The standard pipe normally in three or more coming different classes according to the wall thickness of pipe standard, extra strong and double extra strong or extremely strong. For inspection purposes and for ordering, the minimum thickness must be taken into account the code formula for pipe wall thickness is :

tm = PD

2S + 2Y P + C

Where

tm = minimum pipe wall thickness in inch.P = Maximum internal service pressure psiD = Outside diameter in inchS = Allowable stress in material due to internal pressure as shown in table 1-2.C = Allowance for threading, mechanical strength and/or corrosion.Y = a coefficient having values as given in Table 1-3.

Table 1-2. ASME Power Boiler code.

Material ASTM Specificati

on

Grade or Symbol

Min Tensile

Strength

S Values PSI for Metal Temperature not to exceed

-20 to 650 F

700 F 750 F 800 F

Electrical Resistance Welded Steel

A 53 OR A 135

AB

48.0060.00

10.20012.750

Lap-Welded steel A 53 -- 45.00 9.00 -- -- --Butt Welded Steel A 53 -- 45.00 6.750 -- -- --Stainless steel A 53

A 106AB

48.0060.00

12.00 11.650 10.700 9.000

15.00 14.350 12.950 10.808

Table 1-3. Values of Coefficiently

Temperature, deg F

900 and below

950 1000 1050 1100 1150 and above

Ferrite Steels

0.4 0.5 0.7 0.7 0.7 0.7

Austenitic Steel

0.4 0.4 0.4 0.4 0.5 0.7

SPECIFIC MECHANICAL COURSE FOR ENGINEERSPIPE COMPONENT AND ANCILIARY EQUPMENT LESSON 1 PAGE 4

Table 1-4. Values of C

Type of pipe Value of C, in.

Thread pipe:1/8 in. and smaller

0.05

½ in. and larger Depth of threadPlain end pipe or tubes for 1 in. size and smaller 0.05Plain end pipe or tubes for sizes above 1 in. 0.065

3.3 BRIEF FORMULA FOR WALL TICKNESS (METRIC)

Pipe thickness can be calculated by the following brief formula.

Where P = pressure 1N/mm²

D = pipe diameter mm

= allowable stress of N/mm²carbon steel pipe

t = allowance for corrosionand other factor mm

t = pipe thickness mm

If above values are as follows:

P = 0.686 (N/mm²)

D = 700 (mm)

= 400 x 1/6 = 67 (N/mm²)(6 means safety factor)

t = 2 mm

the pipe thickness will be:

SPECIFIC MECHANICAL COURSE FOR ENGINEERSLESSON 1 PAGE 5 PIPE COMPONENT AND ANCILIARY EQUIPMENT

t = PD

2 + _ t

t = 0.686 x 700

2 x 67 + 2 = 3.6 + 2 = 5.6 (mm)

The calculation result is 5.6 mm, but usually the next thicker section is selected.

Thickness, calculated according to a number of variables is found in the pipe dimension tables given as an example, on table 1-2, 1-3 and 1-4.

The value of the safety factor to be chosen depends on the dynamic or static pressure, and on environmental forces, such as rotating machines.

For static pressure, usually a safety factor of approximately 4 is chosen, while for dynamic pressure this factor is between 6 and 10.

If a pipe is located near a vibration source such as a rotating machine, the chosen safety factor is 6 or larger.

4.0 SCHEDULE NUMBER (SCH)

The SCH number is used to denote the standard thickness of pipe. The formula to decide the SCH number is as follows:

where : P = fluid pressure (N/cm²)

S = allowable stress of pipe material (N/mm²)

Japanese SCH numbers have two categories, as shown in the following:

The SCH numbers for carbon steel pipes

SCH: 10,20, 30, 40, 60, 80, 100, 120, 160

The SCH numbers for stainless steel pipes (thinner than above)

SCH: 55, 10S, 20S, 30S, 40S, 80S

The same SCH number series of pipes have the same pressure durability. Therefore, if an SCH number for one size of pipe is decided, then all series of same SCH number pipes will have same durability against inner fluid pressure. This system has been developed to simplify the determination of pipe thickness and to standardize it for pipe manufacturer and stocking.

Allowable stress S in the above formula is different from country to country for each material and temperature.

For carbon steel pipes for high temperature service (STPT38), at 200C, S is 93.1 N/mm² in Japan. For stainless steel pipes (SUS304LTP) used under the same temperature, S is 106.8 N/cm².

Assuming that a carbon steel pipe is subject to a pressure of 343 N/cm² and a stainless steel pipe to 93.1 N/cm², we have:

SPECIFIC MECHANICAL COURSE FOR ENGINEERSPIPE COMPONENT AND ANCILIARY EQUPMENT LESSON 1 PAGE 6

SCH = 10 x P

S

For carbon steel pipe:

For stainless steel pipe:

Dimension of above formula, cm² and mm², need not coincide for the calculation. That is, P must be expressed by N/cm², and S must be expressed by N/mm².

Next higher SCH than 36.8 equals to 40, and next higher SCH than 8.7 equals to 10S. Hence for above application, SCH of carbon steel pipe and stainless steel pipe should be respectively 40 and 10S.

In order to decide a proper pipe thickness, you must calculate it by using the formula shown.

SCH is 40. Assume that a calculated thickness is 3.7. You have to look for 3.7 thickness shown in SCH40 column, and ascertain whether 3.7 is allotted to its column.

Unless you can not find your desired thickness, you should calculate thickness again, changing the external diameter until the result fits to a data hereon.

SCH of one system of a pipe line is preferably fit equal.

SPECIFIC MECHANICAL COURSE FOR ENGINEERSLESSON 1 PAGE 7 PIPE COMPONENT AND ANCILIARY EQUIPMENT

SCH = 10 x 343

93.1 = 36.8 < 40

SCH = 10 x 93.1

106.8 = 8.7 < 10S

Table 1-5.

Table 1-6.

SPECIFIC MECHANICAL COURSE FOR ENGINEERSPIPE COMPONENT AND ANCILIARY EQUPMENT LESSON 1 PAGE 8

Table 1-7. Carbon Steer Pipes for High Temperature Service.

SPECIFIC MECHANICAL COURSE FOR ENGINEERSLESSON 1 PAGE 9 PIPE COMPONENT AND ANCILIARY EQUIPMENT