TEK.FS.MED.004-M 1.docx

FORM NO: QF-507 MED 004 Page 1-1
TekPath Finishing School
MED 004 - Piping Design
MODULE -1
INTRODUCTION
INTRODUCTION
Pipes are used to transfer fluids such as water, steam, chemicals, oil and gas from one place to another.
Assemblies of piping components are used to convey, distribute, mix, separate, discharge, meter or control
fluid flow. Piping also includes pipe supporting elements but does not include support structure. Process
piping is used to transport fluids between storage tanks and processing units. Service piping is used to convey
steam, air, water etc. for processing. Utility piping is used for supplying water, fuel oil, fuel gas etc.
Transportation piping is normally large diameter piping used to convey liquids, slurries and gases some times
over hundreds of kilometers. Civil piping is used to distribute public utilities and to collect rain water, sewage
and industrial waste water. Most piping of this type is placed under ground. Pipes are also used for
construction works. Steel, cast iron, copper, aluminum, plastic etc. are different materials used for
manufacturing pipes. Pipes are joined by different methods like screwing, welding etc. Different type of pipes
fittings are used for laying of piping.
Depending upon the material used for manufacturing, pipes are classified as
1) Cast iron pipes
2) Steel pipes
3) Galvanized iron pipes
4) Copper pipes
5) Lead pipes
6) Plastic pipes
7) Lined pipes
8) Non metallic pipes
9) Glass pipes etc.
1.2 PIPE & TUBE
Tubular products are termed “pipe or tube”.
Tube is customarily specified by its outside diameter and wall thickness. Pipe is customarily specified by
“nominal pipe size” and wall thickness defined by “schedule number”. The outside diameter of a pipe is
constant for a particular nominal bore irrespective of their wall thickness (ie. schedule number)
1.3 DESIGN CONDITIONS
The piping design basis starts from the line list which specifies design conditions with respect to pressure and
temperature. In the absence of this data, the design engineer should consider the following
1) design pressure as 10% higher than the anticipated maximum operating pressure
2) Design temperature as 250
C above the anticipated maximum operating temperature
3) When operating temperature is 150
C and below, the design temperature as the anticipated minimum
operating temperature
The design should meet the relevant code requirement
The material used shall be in accordance with latest revision of standards. The selection of material
shall follow the norms below for ASTM materials

a) Carbon steel shall be used up to 425 0
C (800 0
F)
b) Low temperature steel shall be used below -29 0
C (-200
F)
c) Alloy steel shall be used above 425 0
C ( 800 0
F)
d) For corrosive fluids recommendation from the process licensor to be followed. The required
thickness for the pipe to withstand internal/ external pressure to be found out using code
formula. Corrosion allowance, if applicable to be added to the calculated minimum thickness. The
thickness arrived thus is to be modified for the mill tolerance of 12.5 %
The design engineer selects/designs the piping components based on the following mechanical
properties
a) Yield strength
b) Ultimate strength
c) Percentage elongation
d) Impact strength
e) Fatigue endurance strength
1.4 DESIGN CODES
Piping designs are generally carried out as per the ASME (American Society of Mechanical Engineers) codes for
pressure piping available under the number B 31. Different codes in this section are as under.
1. B 31.1 – POWER PIPING
2. B 31.2 – FUEL GAS PIPING
3. B 31.3 – CHEMICAL PLANT & PETROLEUM REFINERY PIPING
4. B 31.4 – LIQUID TRANSPORTATION SYSTEMS FOR HYDROCARBONS, LIQUID
5. PETROLEUM GAS, ANHYDROUS AMMONIA AND ALCOHOL
6. B 31.5 – REFRIGERATION PIPING
7. B 31.8 – GAS TRANSMISSION AND DISTRIBUTION PIPING SYSTEMS
8. B 31.9 – BUILDING SERVICES PIPING
9. B 31.11- SLURRY TRANSPORTATION PIPING SYSTEMS
In the field of design and detailed engineering, majority of the projects are related to Oil, Gas, Petrochemical,
Fertiliser and Power sectors. Piping components out of steel materials are normally used in these areas. This
paper is focused on steel materials and related standards generally used in these type of industries.
1.5 MATERIALS
The steel materials largely used fall into carbon steel (CS), alloy steel (AS), stainless steel (SS) and low
temperature carbon steel (LTCS).

1. CARBON STEEL
A steel, which owes its distinctive properties chiefly to the carbon (as distinguished from other elements), that
it contains, is called carbon steel.
2. ALLOY STEEL
A steel, which owes its distinctive properties to elements other than carbon, is known as alloy steel. Alloy
steels are used where high tensile strength at elevated temperatures is desired or where resistance to
corrosion is a factor.
3. STAINLESS STEEL
Alloy steel having unusual corrosion resisting properties, usually imparted by Nickel and Chromium is stainless
steel.
4. LOW TEMPERATURE CARBON STEEL
Unexpected and sudden failures in piping, pressure vessels, bridges and other structures and in welded steel
ships have made engineers and metallurgists aware that steel which behave ordinarily in a ductile manner
may, under certain conditions, exhibit highly brittle character. Although relatively few failures of this type
have occurred in piping, the consequences of such a sudden failure is extremely disturbing and can be tragic.
Steel is generally considered to be a ductile material. When overloaded it usually gives warning by flowing
plastically; i.e. by bulging, stretching, bending or necking before rupturing. Contrary to expectations, however,
steels sometimes rupture without prior evidence of distress. Such brittle failures are accompanied by but little
plastic deformation, and the energy required to propagate the fracture appears to be quite low. Under certain
conditions, steel may shatter like glass. But in piping this extreme behaviour generally occurs only at low
temperatures.
The three conditions which control this tendency for steel to behave in a brittle fashion are (1) high stress
concentrations; i.e. notches, nicks, scratches, internal flaws or sharp changes in geometry (2) a high rate of
straining and (3) a low environmental temperature. These three factors are so interrelated that a
determination of the effect of any one of them gives indication of how the steel will react to intensification of
either or both of the others. The effect of lowering the testing temperature is the condition most convenient
to measure quantitatively. Consequently, the transition from ductile to brittle behaviour of steel is generally
expressed in terms of temperature.
The transition temperature for any steel is the temperature above, which the steel behaves in a
predominantly ductile manner and below which it behaves in a predominantly brittle manner. A steel with a
low transition temperature is more likely to behave in a ductile manner during fabrication or in service, and
therefore, steels with low transition temperatures are generally preferred for service involving severe stress
concentrations, impact loading, low temperatures or combination of the three.
1.6 PIPE SIZING
The following standard pipe sizes shall be used
DN 15, DN 20, DN 25, DN 40, DN 50, DN 80, DN 100, DN 150, DN 200, DN 250, DN 300, DN 350, DN 400, DN
450, DN 500 and DN 600 in accordance with the following limitation
a) Due to their vulnerability to damage and their limited mechanical strength, sizes DN 15 and DN 20
should not be used for long run pipes.
b) Nominal pipe sizes in pipe tracks shall not less than DN 50
c) Nominal pipe sizes in pipe racks shall not be less than DN 40
Unless economically justified, the range of pipe sizes above DN600 shall be restricted to the following, in order
to avoid the purchasing of many different sizes of pipes and fittings
DN 750, DN 900, DN 1050, DN 1200, DN 1350, DN 1500, DN 1650, DN 1800, DN 2100, and DN 2400

After the basic pipe routes, number of valves, control valves, fittings etc. have been determined the
anticipated pressure drops for the preliminary pipe sizes shall be checked.
Pipe sizes shall be listed in the data sheet.
1.6.1 Consideration in pipe sizing
The following should be considered in determining a suitable pipe size
1) The available pressure drop
2) The fact that pressure surges may occur in the piping system
3) The fact that erosion may occur in the piping system
4) The fact that piping system may be subjected to vibration
5) The fact that settlement of solids may occur when the fluid is slurry
6) The allowable temperature drop if the fluid is highly viscous
7) An economic pipe size considering capital and operating expenditure
The above consideration shall be taken into account both for design capacity and for conditions
such as starting up, shutting down and regeneration.
1.6.2 Reynolds number (Re)
The Reynolds number indicates whether the flow is laminar or turbulent. The change from one type of flow to
the other may occur at a definite value of Reynolds number. Laminar flow can be expected in pipes if the
Reynolds number is < 2300. Turbulent flow can be expected when Re > 4000. With Re between 2300 and 4000
the flow can be easily switched from one type to other, i.e. transitional flow.
This could change the pressure drop by a factor of 3 or more
The Reynolds number is calculated as follows
Re = ρvdi /
Where Re = Reynolds number
Ρ = density (kg/m3
)
V = Average linear flow velocity (m/s)
di = inside diameter of pipe (m)
 = Dynamic viscosity (Pa.s)
In terms of kinematic viscosity the above equation become
Re= vdi /
Where = / ρ= kinematic viscosity
1.6.3 Pressure drop calculation
The formulae for pressure drop calculations given below are applicable to fluids whose density and viscosity
are constant along the length of the whole pipe. Pressure drop due to piping component other than straight
pipe shall be exposed for calculation purpose as equivalent length (Le ) and added to the length of the straight
pipe in the system, thus giving the total length ( L) to be used in the pressure drop calculation.
For valves and fittings Le is given in the table below.

The pressure drop across control valves shall be determined in consultation with parties responsible for
instrumentation. To obtain a reasonable degree of control, the pressure drop across the control valve (at 80%
open position) shall be at least 1 bar. However, if the pressure drop across the control valve is too high the
installing of a piece of small bore pipe in front of the control valve in order to reduce the pressure drop across
the valve shall be considered.
1.6.3.1 General equation for pressure drop calculation
The pressure drop for a piping system is given by the equation:
In which: ∆p = pressure drop (N/m2)
 = friction factor which depends on the Reynolds number and the roughness factor
L = total design length (m)
di = inside diameter of pipe (m)
v = average linear flow velocity (m/s)
ρ= density (kg/m3)
To convert pressure drop from N/m2 into meters of liquid, the above equation can be written as:
Table1.1

In which: g = acceleration due to gravity (m/s2)
See figures: 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6
1.6.4 SCHEDULE NUMBER
Common pipe thicknesses are specified as schedule numbers. They are approximate values of the formula,
SCHEDULE NUMBER = 1000 X P/S
Where, P = maximum internal pressure and S = allowable stress of material at maximum system temperature.
1.7 PIPE WALL THICKNESS CALCULATION
1.7.1 Thickness of straight pipe for internal pressure
ANSI/ASME B31.3 code gives minimum thickness as follows
Tm = T+C
Where T= PDo/2(SE+PY)
P = design pressure in psi
Do = outside diameter in inches
S = Allowable stress for the material in psi
E = joint quality factor (table 1.2)
Y = coefficient (table 1.3)
C = C1 + C2
C1 = corrosion allowance for carbon steel, in inches
C1 = 0 for stainless steel
C2 = depth of thread (used only upto 1½ “ NB)
The calculated thickness to be corrected to consider the mill tolerance of – 12.5 % as
Tm= 8 x PDo + C1 + C2
7 2(SE+PY)
Example:1
Q) A 8” (200NB) pipe has an internal maximum operating pressure of 500 psig (35kg/cm2
) and temperature of
6750
F. The material of construction of the pipe is seamless carbon steel to ASTM A 106 Gr B. The
recommended corrosion allowance is 1/8 “(3mm). Calculate the thickness of pipe as per ASME B 31.3 and
select the proper schedule.
Ans:
Tm= P D + C
2(SE+PY)
P=10% higher than the Maximum working pressure

= 1.1 x 500= 550 psi
D=8.625”
Design temperature= 675+25=7000
F
S, allowable stress=16500 lbs at 7000
F for A 106 Gr B ( refer ASME B 31.3 Appendix -A Table A-1)
E=1 (Joint Quality efficiency Refer ASME B 31.3 Appendix -A Table A-1B) (Refer Table 1.2)
Y=o.4 (Refer Table 304.1.1) (Refer Table 1.3)
C=0.125” (Specified)
Hence Tm= 550 x 8.625” + 0.125
2(16500x 1+ 550 x 0.4)
= 0.1419 + 0.125
= 0.2669
Consider the mill tolerance of 12 ½ % , the normal wall thickness of 0.2669” will be
T=0.2669/.875=0.305”
In practice we will specify schedule 40 pipe which has a nominal wall thickness of 0.322” and minimum of
0.2669”
1.7.2 Thickness of straight pipe for external pressure
The pipe with a large ratio of diameter to wall thickness will collapse under an external pressure which is only a
small fraction of internal pressure, which it is capable of withstanding. To determine the wall thickness under
external pressure, the procedure outlined in the ASME code section VIII division 1 UG-28 through UG-30 shall
be followed
Example:2
Q) A 6” (150 NB) pipe has an external Design Pressure of 400 psi: at 750F. The material of construction of pipe
is seamless austenitic stainless steel to ASTM A 312 TP 304 L. Calculate thickness and select proper schedule.
Ans:
Refer ASME Section VIII div 1, UG 28 Assume value of T and determine ratios L/D0 and D0/t D0 for 6” NB pipe
= 6.625”
Assume Sch 40S pipe Nominal thickness = 0.28”
Consider L/D0 = 50 since L is unspecified Minimum thickness considering negative mill tolerance of 12.5%
t = 0.875 x 0.28=0.245”
Do/t= 6.625/0.0245=27.04
From Graph (Fig. G) in ASME Section II Part D Factor A = 0.0015 (see fig: 1.7)
From Graph (Fig. HA-3) in ASME section II Part D Factor B (see fig: 1.8) for the above factor A and 750 F = 4500
allowable Pressure Pa = 4/3 x B = 4 x 4500
Do/t 3 x 27.04
=221.89 psig
Less than Design Pressure
Assume higher thickness.
Consider Sch 80 S pipe
Nominal thickness = 0.432''
Minimum thickness = 0.432'' x .875=0.378”

Do/t =6.625/0.378=17.5
Factor A for the new value of Do/t=0.0038
Corresponding factor B=5500
Allowable pressure 4x5500 =419 psig
3x 17.5
More than design pressure
Hence select Sch. 80 s pipe
1.8 PIPING BELOW GROUND LEVEL
1.8.1 Buried piping
Buried piping shall be considered for:
- drainage or sewage;
- fire water and other water pipes, for protection against heat or frost;
- large-diameter pipes (e.g. main cooling water ducts) so as not to impede traffic.
Buried piping shall have a minimum cover of soil as shown below:
- fire water pipes (mains) 0.6 m
- in areas inaccessible to heavy traffic 0.3 m
- in areas accessible to heavy traffic and at road crossings,
pipes of DN 600 and smaller 0.6 m
pipes over DN 600 0.9 m
- pipes crossing beneath railways 1.0 m
- in areas where only night frost can be expected 0.6 m
- in areas where daytime freezing can be expected 0.7 m
The above soil cover depths depend on the outside temperature and the permeability of the soil. In areas
where prolonged sub-zero temperatures may occur, the suitability of the above soil cover depths shall be
confirmed. The load on pipes crossing railways and roads should be equalised, e.g. by means of pipe sleeves or
a culvert. The pipes shall be kept centrally in the sleeves by distance pieces welded to the pipe or fixed to the
sheeting if the pipe is insulated for low-temperature service. Insulated pipes should not be buried. If this is
unavoidable, or if it is desired for life-cycle economic reasons, the insulation material shall be able to
withstand the stresses caused by the thermal expansion of the pipe. Special attention shall be paid to avoid
corrosion under the insulation and the system shall be designed so that inspection is possible or not needed.
Soil settlement and thermal expansion of the piping shall be taken into account in the design of underground
piping. For buried pipes operating at a temperature of 60 °C or below, there shall be a clear distance of at least
300 mm between the pipe and any electrical or instrument cables. For buried pipes operating above 60 °C, the
pipe shall be insulated to limit the outer surface (cladding) temperature to a maximum of 60 °C and there shall
be a clear distance of at least 600 mm between the cladding and any electrical or instrument cables. For
buried pipes which have impressed current cathodic protection, there shall be a clear distance of at least 1 m
between the pipe and any parallel-running cables, to prevent stray current corrosion of the steel wire
armouring of those cables. Piping shall be designed so that the complete system can be flushed and cleaned.
(e.g. “dead ends” should be avoided).
1.8.2 Pipe tracks and pipe trenches
Piping outside process units (e.g. piping between process units and storage facilities) should be supported on
sleepers, at ground level in pipe tracks or below ground level in pipe trenches. The choice between pipe tracks

or pipe trenches is dictated by technical and economic considerations, e.g. the number of road or rail
crossings, the ground water level and the length of the required trench. Pipe racks may be used if space at
ground level is limited or if the use of culverts or buried piping is uneconomical.
The distance between sleepers in pipe tracks and in pipe trenches shall be based on the maximum allowed
free span of the majority of pipes. Smaller pipes requiring a shorter supporting distance shall be grouped
together and be supported on additional supports.
The elevation of the sleepers shall be such that there is access for maintenance and for operation of valves,
drains and instrumentation and that pipes and insulation will remain above the highest expected storm water
levels.
Flanged connections shall not be installed in trenches, in order to prevent the accumulation of gas and liquid
vapours in the trenches. Concrete trenches in process units shall be adequately drained into a liquid-sealed
drainage system and shall be covered with grating.
1.9 PIPING ABOVE GROUND LEVEL
Except for the services mentioned under 1.6 above, piping shall be routed above ground level. Where
practical, piping entering and leaving a plot area or a processing unit shall be grouped together. Where
practical, inside-plot piping shall be routed on overhead pipe racks. These pipe racks usually have a stanchion
interval giving a span of around 7 m. If the pipe diameters require closer supports then intermediate beams
shall be installed. The smallest allowable pipe size on pipe racks is DN 40. If the span between the supports is
too long for a pipe, the size of that pipe may be increased, instead of additional supports being provided; if
this is justified technically and economically (the technical evaluation shall include the possibility of internal
corrosion due to the slower flow causing separation of corrosive liquid from the mixture). If a pipe rack forms
a part of a structure, or is located next to a structure, the stanchions of the pipe rack should be in line with the
columns of the structure, to make optimal use of space for incoming and outgoing pipes. Equipment which is a
potential source of fire shall not be located under pipe racks.
Piping with instrument connections shall be routed so that safe access to these connections is ensured; if
necessary, platforms or walkways shall be provided. Care shall be taken to avoid any possibility of
contaminating austenitic stainless steel, duplex stainless steel, nickel alloy or 9% nickel steel components with
zinc. If hot work is performed on galvanised items situated in the vicinity of these components, they shall be
shielded (e.g. with fire blankets) to avoid contamination. For components which are insulated, the cladding is
considered to be sufficient protection. A forked pipe shall be designed and supported so that no excessive
loads on equipment may occur when one branch of the pipe is disconnected (e.g. during maintenance
operations). Where multiple nozzles are applied (e.g. on air cooler banks) the connecting piping shall be
designed so that small dimensional errors in construction can be accommodated. Safety relief valve discharge
piping shall be designed to withstand the dead loads and the blow-off loads. Blow-off design loads shall take
into account the most severe case, such as possible flashing conditions and liquid entrainment in vapour flows.
In a pipe rack the heaviest and/or the hottest pipes should be located at the sides of the pipe rack to provide
space for expansion loops and to reduce the moments in the beams caused by the weight and thermal
expansion of the pipes.
The minimum elevation of the bottom of overhead piping shall be:
6.0 m over railways;
6.0 m over main roads;
4.0 m for crane access;
4.0 m for truck access;
2.7 m for fork-lift truck access;
2.1 m over walkways and platforms

NOTE: In some situations the lower side of the pipe supports or the supporting steel dictates the minimum
elevation of overhead piping.
There shall be a minimum horizontal clearance of 0.75 m for access ways and walkways, and 0.9 m for
thoroughfares.
Pipe routings and crossings shall be on different, predetermined elevations. Complicated crossings should be
avoided by not installing pipe rack spurs opposite each other
1.10 EXPANSION, CONTRACTION AND SUPPORTING
Piping systems shall be routed, supported, anchored or guided so that thermal expansion/contraction,
vibration or movements due to earthquakes and storms will not result in stresses in the piping or in the
connected equipment in excess of those permitted by ASME B31.3 and the equipment design code, in order to
prevent:
- failure of piping components due to overstress;
- leakage at joints;
- excessive loads and moments on connected equipment, anchor points, flanged connections, etc.
The upper and lower design temperatures and differences in temperature between piping and equipment
shall be taken into account for all design cases. Loops and/or offsets shall be provided in piping systems where
improved flexibility is required. Expansion joints may be installed only where loops or offsets cannot be used
(e.g. due to limited space) or will not give sufficient flexibility. Expansion joints shall be used only if the fluid
fouling properties cannot make them ineffective. Expansion joints shall be provided with guides and anchors
to withstand forces generated by the internal pressure. Where an uneven flow is possible, additional supports
and/or anchors should be installed to protect the expansion joints. The tresses, forces and movements on
expansion joints shall be within the limits stated by the Manufacturer. Information about expansion joints and
about the location of supports in pipes with expansion joints is given in the EJMA standard. Expansion joints
shall not be used in very toxic services or in systems where they would be subjected to tensional loads. Pipes
should be supported in groups at a common support elevation. Since civil design is often done earlier than
piping support design, special structural provisions for connecting pipe supports, such as inserts poured in
concrete beams or supporting structures, should be made during the civil and mechanical engineering phase
and should be located at standard locations.
Identification of standard pipe supports and special pipe supports shall be shown in the 3DCAD model, on
piping plan drawings and on piping isometric drawings. Supports and supporting structures shall be able to
sustain the hydrostatic test load. If this is not economical, temporary supports may be applied. Spring supports
shall be blocked, or removed and replaced by temporary supports which are able to sustain the hydrostatic test
load. The use of spring supports, snubbers and sway braces should be avoided. If they are unavoidable they
shall be permanently accessible. If this may lead to unacceptable costs the Principal shall be consulted. The
most commonly applied type of spring assembly is the "variable load" unit. If very low variable loads are
essential, such as pipes connected to strain sensitive equipment or for critical systems with large movements,
"constant load" type units shall be used. Excitation forces of two-phase flow pipes and flare pipes shall be
determined and a dynamic analysis of the piping system shall be considered. At points where flow conditions
change, e.g. where diameter or flow direction change, the possible occurrence of movements shall be analysed
and, if necessary, adequate measures shall be taken to hold the pipes in place, without the pipes and the
supporting structure being over-stressed by expansion or settlement. Guides near expansion loops in these
lines should be of the goal post type. Supports shall be located as close as possible to changes in direction but
shall allow adequate flexibility for thermal expansion and settlement of the pipe. If pipe stress calculations
require the approval of national or local authorities they shall be performed by methods approved by those

authorities. Formal computer flexibility analysis shall be made of all critical systems, which include the
following:
• pipes DN 500 and larger;
• Process pipes DN 80 and larger if connected to rotating equipment;
• Pipes connected to air-cooled heat exchangers;
• Pipes connected to pulsating equipment;
• Pipes to and from boilers and heaters;
• In cases where differential settlement of equipment and/or supports is expected;
• Process regeneration pipes;
• Pipes where engineered items are required like spring supports, expansion joints, snubbers etc.;
• Pipes subject to slug flow or water hammer;
• If required by local regulations;
• Pipes for two-phase flow;
• flare pipes DN 100 and larger;
• Pipes subjected to relief loads;
• pipes DN 80 and larger in very toxic service operating at temperatures above 200 °C
1.10.1 EXPANSION BELLOWS
Engineering materials experience changes in dimensions as a result of application of stress, change in
temperature, passage of time, change in internal configuration, changes in dissolved moisture content and
possibly a few other causes. Of these, the first two are by far the most important as far as piping is concerned.
Piping should be designed so that time dependant inelastic effects such as creep and relaxation are of
negligible importance. Materials selected for piping service should be stabilized and should be used for
temperatures for which there is no significant change in internal structure. Moisture content is obviously not
of significance in metallic piping. Thus, essentially dimensional changes in piping material depend upon
changes in temperature and stress.
The linear expansion of piping system is accomodated either by the flexible action of the piping itself or by
employing special devices, usually called expansion joints, in which, so to speak flexibility is concentrated.
Expansion joints may be divided into two basic categories : (1) sliding joints, in which there is a relative motion
of adjacent parts, and (2) flexible joints, in which there is no such relative motion but rather a distributed
distortion of the device.
1.11 DISTANCE BETWEEN PIPES
The minimum distance between pipes or the insulation of pipes in pipe tracks and trenches and on pipe racks
shall be 75 mm. The minimum distance between a flange and a pipe or the insulation of a pipe in pipe tracks
and trenches and on pipe racks shall be 30 mm. Where required, the distance between pipes shall be
increased to allow for movements caused by thermal expansion. The distance between the insulation of a low-
temperature pipe and any other object shall be at least 100 mm. The distance between pipes shall allow for
the turning of a spectacle blind, if present

Table 1.2

Table 1.3

Table 1.4
Dimension and properties of pipe-DN 6 to DN 750

Table 1.4 (Continued)

Fig: 1.1
Friction factors and roughness factors for flow in pipes
Friction factor for Reynolds number up to 2 x 105

Fig: 1.2
Friction factors and roughness factors for flow in pipes
Friction factor for Reynolds number up to 2 x 105 to 108

Fig: 1.3
Roughness factors for flow in pipes

Fig: 1.4
Pressure drop in carbon steel water pipes at 200C
Flow rate 1 m3/h to 10m3/h

Fig: 1.5
Flow rate 10m3/h to 300m3/h

Fig: 1.6
Flow rate 300m3/ h to 10000m3/h

Fig:1.7

1.12 PIPING COMPONENTS
The piping system is the interconnected piping subject to the same set of design conditions. The piping system
includes not only pipes but also the fittings, valves and other specialties. These items are known as piping
components. Codes specify the piping components as mechanical elements suitable for joining or assembly
into pressure-tight fluid-containing piping systems.
The various piping components include:
PIPES
FITTINGS
FLANGES
GASKETS
BOLTING
VALVES
SPECIALITIES
1.13 PIPING ELEMENTS
The piping element is defined as any material or works required to plan and install the piping system.
Elements of piping include design specifications, materials, components, supports, fabrication, inspection and
testing. Piping elements should so far as possible conform to the specifications and standards listed in the
code referred for design.
Fig:1.8
Chart for determining shell thickness of components under external pressere when constructed of austenitic
steel ( 18 Cr-8 Ni-0.035 maximum carbon, type 304L)

1.14 PIPING SPECIFICATION
Piping specification is a document specifying each of the components. Different material specifications are
segregated in different “Piping classes”. Identification of the “Piping classes” depends on each design engineer
and the logic adopted by the design engineer.
1.15 TYPES OF PIPES
Many different processes are used in the manufacture of pipe. They are grouped by definition into
several classification such as wrought seamless pipe, forged pipe, welded pipe and cast pipe. Within
each classification a number of specific processes are employed.
1.15.1 Wrought Seamless Pipe
Pipes produced by piercing a billet followed by rolling or drawing or both.
1. Hot rotary piercing
2. Pilger – mill process
3. Push – bench (cupping) process
4. Extrusion Process
1.15.2 Welded
Electric resistance welded (ERW)
Pipes having longitudinal butt joint wherein coalescence is produced by the heat obtained from
resistance of the pipe to flow of electric current in a circuit of which pipe is a part and by application of
pressure.
Furnace Butt Welded, Continuous Welded
Pipes having longitudinal weld joint forge welded by mechanical pressure developed in passing the
hot-formed and edge heated skelp through round pass weld rolls.
Electric Fusion Welded
Pipes having longitudinal butt joint wherein coalescence is produced in the performed tube by manual
or automatic electric arc welding. Weld may be single or double.
Double Submerged-arc welding
Pipes having longitudinal butt joint produced by at least two passes, one of which is on the inside of
the pipe. Coalescence is produced by heating with an electric arc between the bare metal electrode or
electrodes and the pipe. Pressure is not used and filler material is obtained from electrode.
Spiral welded
Pipes having helical seam with either a butt, lap, lock-seam joint which is welded using either an arc
resistance, electric fusion or double submerged arc welding process.
1.15.3 Forged and bored
1.18.1 Forged and bored pipe
1.18.2 Hollow forged pipe
1.15.4 Cast
1.18.3 Static casting
1.18.4 Centrifugal casting

1.16 PIPE ENDS
a Beveled ends
Beveled ends are specified when pipe to pipe and/ or pipe to fittings joints are done by butt welding.
b Plain ends
Plain ends are specified when pipe to pipe and/or pipe to pipe joints are done by threaded
connections.
c Screwed ends
Screwed joints are specified when pipe to pipe and/ or pipe fittings are done by threaded connections.
d Flanged ends
Flanged ends are specified to provide bolted connections between pipe and between pipes and/or
fittings.
e Spigot/ Socket ends
Spigot/ Socket ends are specified when lead caulked/ cemented joints are provided between pipes
and between pipes and fittings.
f Buttress Ends
Buttress Ends are used in glass piping and are joined by bolting with the use of backing flanges.
1.17 PIPE JOINTS
1. Butt Weld Pipe Joints
Advantages
 Most practical way of joining big bore piping
 Reliable leak proof joint
 Joint can be radiographed
Disadvantages
o Weld Intrusion will affect flow
o End preparation is necessary
2. Socket Weld Pipe Joint
Advantages
 Easier alignment than butt welding
 No weld metal intrusion into bore
Disadvantages
1.28.1 The 1/16”(1.5 mm) recess pockets liquid
1.28.2 Use not permitted by code if severe erosion or crevice corrosion is anticipated.
3. Screwed Pipe Joints
Advantages
 Easily made at site
 Can be used where welding is not permitted due to fire hazard.
Disadvantages
 Joint make leak when not properly sealed.
 Use not permitted by code if severe erosion, crevice corrosion, shock or vibrations are anticipated.
 Strength of pipe is reduced as threads reduce wall thickness.
 Seal welding may be required.
 Codes specify that seal welding shall not be considered to contribute for strength of joint.

4. Flanged Pipe Joints
Advantages
1.16.1 Can be easily made at site.
1.16.2 Can be used where welding is not permitted due to material properties or fire hazards.
1.16.3 Dismantling is very easy.
Disadvantages
1.21.1 It is a point of potential leakage.
1.21.2 Cannot be used when piping is subjected to high bending moment.
5. Spigot Socket Pipe Joints
Advantages
 Can be easily made at site.
 Can accept misalignment up to 10° at pipe joints.
Disadvantages
 Suitable for low pressure application.
 Special configuration at pipe ends required.
6. Buttress End Pipe Joints
Buttress end pipe joints are used only for glass piping and not capable to hold high pressure.
1.18 PIPE FITTINGS
Flanged End Pipe
Spigot / Socket End Pipe

Fittings are mainly classified into two, based on the method of manufacture. They are forged fittings and
wrought fittings. Apart from these cast fittings are also available.
1. FORGED FITTINGS
Forged fittings are available with socket-welding ends and threaded ends. The types of fittings available are
90-degree elbows, 45-degree elbows, Tees, Crosses, Couplings, Half Couplings, Caps, Plugs and Bushings.
DIMENSIONAL STANDARDS
ASME B 16.11 – Forged fittings, socket welding and threaded
MSS – SP – 79 – Socket welding reducer inserts
MSS – SP – 97 – Forged carbon steel branch outlet fittings
(Manufacturers Standardization Society of the valve and fitting industry – Standard Practice)
2. WROUGHT FITTINGS
Wrought fittings are available with butt-welding ends. The types of fittings available are 90-degree elbows, 45
degree elbows, 180-degree returns, Tees, Crosses, Lap joint stub ends, Reducers and Caps.
DIMENSIONAL STANDARDS
ASME B 16.9 – Factory made wrought steel butt-welding fittings
ASME B 16.28 – Wrought steel butt-welding short radius elbows and returns
MSS – SP – 43 – Wrought stainless steel butt-welding fittings
 Socket Weld / Screwed End Fittings
For socket weld / screwed end fittings, four pressure classed are available. They are:
2000# Class
This class is applicable only for screwed fittings and is covered only in ANSI B 16.11. The
corresponding pipe thickness for this class is Sch 80 or XS.
3000# Class
This class is applicable from both screwed and socket weld fittings. The corresponding pipe
thickness for this class is Sch 80 or XS for socket weld end connection and Sch 160 for screwed
end connections.
6000# Class
This class is also applicable for both screwed and socket weld fittings. The socket weld fittings
under this class are normally used with Sch 160 pipes and screwed fittings with XXS pipes.
9000# Class
This class is applicable only for socket weld fittings and are normally used with XXS pipes. The
screwed end fittings can be with parallel threads or with taper threads. Taper threads are
preferred for the fittings. These could be to NPT or to relevant Indian Standard specifications.
General material standards applicable for fittings, flanges and valves are given below

MATERIAL TYPE STANDARD
CS
FORGED ASTM A 105
WROUGHT ASTM A 234
CAST ASTM A 216
AS
FORGED ASTM A 182
WROUGHT ASTM A 234
CAST ASTM A 217
SS
FORGED ASTM A 182
WROUGHT ASTM A 403
CAST ASTM A 351
LTCS
FORGED ASTM A 350
WROUGHT ASTM A 420
CAST ASTM A 352
 Sw/ Scrd Fitting Materials
 ASTM A105 - Forged Carbon Steel
 ASTM A181 - Forged Carbon Steel for General purposes
 ASTM A182 - Forged Alloy Steel and Stainless steel
 ASTM A234 - Wrought Carbon Steel and Alloy Steel pipe fittings
for moderate and elevated temperatures
 ASTM A350 - Forged Alloy Steel for low temperature services
 Beveled End Fittings
These types of fittings are connected to piping by means of butt welding. The thickness of these fittings is to
be specified the same as that of pipes because the bore of the pipes and the attachments should match. That
means both the items should have the same schedule number. There are certain exceptional cases where
fittings of higher thickness are used.
The material of construction specified in the American standards for the butt fittings are:
Bw Fitting Materials
ASTM A 234 - Carbon Steel fittings
ASTM A 403 - Austenitic Stainless steel fittings
ASTM A 420 - Alloy Steel for lower temperature services
3. Flanged End Fittings
Fittings with both ends flanged are used where welding is not possible or permitted. Normally these are made
by casting. Classification of these fittings are based on the pressure temperature ratings same as that of
flanges.
Dimensional standard is the same as that for flanges. The fittings fabricated from standard butt weld or socket
welded flanges do not cover under this standard. The material specification is the same as that for castings.
Normally used materials are
1 ASTM A 216 - Carbon Steel castings
2 ASTM A 351 - Stainless steel castings
3 ASTM A 352 - Alloy Steel Castings
4 ASTM F1545 - Plastic Lined Fittings
5 IS 1538 - Cast Iron Fittings

 Spigot Socket Fittings
Spigot Socket fittings are used in cast iron piping for low pressure services. The joints are sealed by Lead
caulking. Flanged sockets and flanged spigots are used for connection to flanged equipments and valves.
 Buttress End Fittings
Buttress ends fittings are used in glass piping. These fittings are bolted together with the help of backing
flanges and PTFE inserts.
1.19 TYPES OF FITTINGS
There are various types of fittings used to complete the piping system. These are used to change the direction,
change the diameter or to branch off from main run of pipe. The special feature of the same is as below.
There are two types of 90 deg, butt welding elbows available for use. These are the long radius and short
radius elbows. The long radius elbows have a bend radius of 1.5D, where D is the nominal size, whereas the
short radius elbows have a bend radius of 1D.
1. Tees
Branch connections of equal/ reducing sizes are achieved by Tees. For low pressure services, branching off is
done by direct welding of pipe instead of using a standard fitting. In certain cases, reinforcing pads are used
for structural stability of such connections. The branching schedule specified along with piping specification
explains what sort of a branching schedule specified along with piping specification explains what sort of a
branch connection is to be use for that particular piping class.
The manufacturing restrictions do not allow reducing Tees of all sizes. To arrive at available sizes of reducing
tees in the standard, use the thumb rule of dividing the major diameter by 2 and consider the next lower size.
For Example, the minimum size of reducing tee available for 4” NB size is 4” * 1 ½” (next lower size of 4/2= 2”
).
2. Reducers
There are two types of reducers, the concentric reducers and the eccentric reducers. When the centre line of
the larger pipes and smaller pipes are to be maintained same, then concentric reducers are used.
When one of the outside surfaces, of the pipe lines are to be maintained same, then eccentric reducers are
required. There are no eccentric reducers in a socket weld fitting and swage nipples used for such service. The
thumb rule to check the available size of reducers is same as that of Tees.
3. Stub Ends
To reduce the cost of piping, stub ends are used with backing flanges for flange joints when exotic materials
are used in piping. ANSI B16.9 specifies two types of stub ends, the long stub ends and the short stub ends.
The length of stub ends as per MSS-SP-43 is the same as that of short stub ends. MSS-SP-43 also specifies two
classes, Class A with radius and Class B without radius. Class B can be used with slip on flanges. Designers use
stub-ends to B 16.9 up to 40NB and MSS-SP-43 for sizes 50 NB and above depending upon the flange
construction. When Class A stub ends are used the inner surface of backing flange is machined for better
seating.
4. Couplings
a. Full couplings
b. Half couplings
c. Reducing couplings
Full couplings are used to connect small bore pipes as projection of welding inside the pipe bore reduces the
Flow area.
Half couplings are used for branch connections.

Reducing couples are used for size reduction. Reducing coupling maintain the pipe centre lines same and
eccentric swage nipples are required to maintain the outside surface same.
5. Swage nipples
Swage nipples are like reducers but is used to connect butt welded pipe to smaller screw to socket welded
pipe. These are covered under the regulating code BS 3799. There are two types of swage nipples, the
concentric and the eccentric. Various combinations of end connections are possible in swage nipples. These
are designated as
 PBE - Plain both Ends.
 TBE -Threaded both ends.
 PLE - Plain large end
 PSE - Plain small end
 BLE - Beveled large end
 TSE - Threaded small end
6. Unions
Unions are used when dismantling of the pipe are required more often in small bore non-critical piping. Union
can be with threaded end or with socket weld ends. There are three pieces in a union, two end pieces to
attach to the run pipe and the third threaded piece to connect these two.

1.20 SPECIAL FITTINGS
These are fittings which have restrictive use. The items referred under special fittings are3
1. Weldolet
It makes a 90-degree branch, full size or reducing, on straight pipe. Closer manifolding is possible than
with tees. It is used for butt-weld branch connection where standard Tee is not available due to size
restriction and the piping is of critical/high-pressure service. Flat-based weldolets are available for
connecting to pipe caps and vessel heads.
2. Sockolet
It makes a reducing tangent branch on long-radius and short-radius elbows. It is used for socket welding
branch connection, which require reinforcing pad.
3. Threadolet
It is used for threaded branch connections.
4. Elbolet
It is used for Branch connection on elbows and have the profiles made to suit the elbow
5. Sweepolet
It makes a 90-degree reducing branch from the main run pipe. Primarily developed for high yield pipe used
in oil and gas transmission lines. It provides good flow pattern, optimum stress distribution. It is used for
integrally reinforced butt weld branch connection.
6. Latrolet
It makes a 45-degree reducing branch on straight pipe. It is used for branch connections at an angle.

1.21 FLANGES
Flanges are used when joints needs dismantling. These are mainly used at equipment, valves and specialties.
In certain pipelines where maintenance is a regular feature, breakout flanges are provided at definite intervals
on pipelines. A flanged joint is composed of three separate and independent although inter-related
components: the flange, the gaskets and the bolting. Special controls are required in the selection and
application of all these elements to attain a joint, which has acceptable leak tightness.
Classification of Flanges
 Based on Pipe attachment
 Slip-on
The slip-on type flanges are attached by welding inside as well as outside. Normally, these flanges
are of forged construction and are provided with hub. Sometimes, these flanges are fabricated
from plates and are not provided with hub.
 Socket weld
The socket weld flanges are welded only on one side and are not approved by IBR.
 Screwed-on
The screwed-on flanges are used on pipelines where welding cannot be carried out.
 Lap Joint
The lap joint flanges are used with stub ends when piping is of costly material. The stub ends will
be butt welded to the piping and the flanges are kept loose over the same. The inside edges of
Weldolet Sockolet Latrolet
Threadolet Sweepolet Elbolet
Slip-on Socket weld

these flanges are chamfered to clear the stub end radius. With Class B type stub ends slip-on
flanges are used for the same duty.
 Welding Neck
The Welding neck flanges are attached by butt welding to the pipes. These are used mainly for
critical services where all the joints need radiographic inspection. While specifying these flanges,
the thickness of the welding end also is to be specified along with.
 Blind Flanges
These are used to close the ends which need to be opened later.
 Reducing Flanges
The Reducing Flanges are used to connect between larger and smaller sizes without using a
reducer. In case of reducing flanges, the thickness of the flanges should be that of the higher
diameter.
 Integral Flanges
Integral Flanges are those cast along with the piping component or equipment. There are some
types of flanges developed by manufacturers which are not covered in code. They are mainly
modification on the welding neck such as:
 Long Welding neck flange
 Expander/ Reducing Flanges
 Based on facing
The flanges can also be classified based on the facings as:
1. Flat faced (FF)
2. Raised face (RF)
3. Tongue and groove (T/G)
4. Male and Female (M/F)
5. Ring type joint (RTJ)
Flat face flanges are used when the counter flanges are flat face. This condition occurs mainly on
connection to cast iron equipments, valves and specialties.
For 150# and 300# flanges, the raised face is 1/6 inch and is included in the thickness specified. For higher
rating, the flange thickness does not include the raised face thickness. The raised face thickness for higher
rating is ¼ inch.
 Based on face finish
There are two types of finishes done on the facings. They are smooth finish and the serrated finish. The
smooth finish flanges are specified when metallic gaskets are specified and serrated finish is provided when
a non-metallic gasket is provided on the facing. The serrations provided on the facing could be concentric
or spiral (phonographic). Concentric serrations are insisted for face finish when the fluid being carried has
very low density and can find leakage path through the cavity. The serration is specified by the number,
which is the Arithmetic Average Roughness Height (AARH). This is the arithmetic average of the absolute
Lap Joint Welding Neck

values of measured profile height deviations taken within the sampling length and measured from the
graphical centre line.
 Based on pressure – temperature rating
The Flanges are classified based by the pressure – temperature rating in ANSI B 16.5 as:
a) 150 #
b) 300 #
c) 400 #
d) 600 #
e) 900 #
f) 1500 #
g) 2500 #
Pressure – temperature rating charts, in the Standard ASME B 16.5. Specify the non- shock working gauge
pressure to which the flange can be subjected to a particular temperature. The indicated pressure class of
150#, 300#, etc. is the basic ratings and the flanges can withstand higher pressures at lower temperatures.
ASME B 16.5 indicates the allowable pressures for various materials of construction vis-a -vis the temperature.
ASME B 16.5 does not recommend the use of 150# flange above 400° F.
 Based on material construction
The Flanges are normally forged except in very few cases where they are cast or fabricated from plates. When
plates are used for fabrication, they should be of weldable quality. The normal material for construction used
is:
ASTM A105 - Forged Carbon Steel
ASTM A181 - Forged Carbon Steel
ASTM A182 - Forged Alloy Steel and stainless steel
ASTM A350 - Forged Alloy Steel for low temperature services
 Miscellaneous
Certain British Standards, German Standards, Indian Standards are also followed in India for Flange dimensions
BS-10 is the most popular among them even though British Standards Institute themselves have withdrawn
the same. DIN flanges are also popular because it has a wider range of pressure temperature classes. BIS has
developed IS 6392 in line with DIN Standards and the same is also in use.

1.22 GASKETS.
 Selection
Proper Selection of gasket depends upon following factors.
1. Compatibility of the gasket material with the fluid
2. Ability to withstand the pressure-temperature of the system.
 Type
Based on the type of construction, gaskets are classified as:
 Full Face
 Inside bolt circle
 Spiral wound metallic
 Ring type
 Metal jacketed
 Material
Experience on the job and published literature shall be used to select the gasket material with respect to
the compatibility of the same with the fluid.
The material which is commonly used is the Compressed Asbestos Fibre . Indian Standard IS 2712
specifies three different materials at three different grades.
IS 2712 Gr W/1 , W/2 and W/3 - for Steam , alkali and general applications.
IS 2712 Gr A/1 - for acid applications.
IS 2712 Gr O/1, O/2 and O/3 - for Oil applications
Asbestos free gaskets are also available for above application
For very corrosive applications, PTFE or PTFE enveloped gaskets are used. The selection of material of
construction for winding depends upon the corrosiveness and concentration of the fluid, the operating
temperature and the relative cost of winding materials. The most commonly used are the Austenitic
stainless steel 304,316 and 321 with Asbestos. For very high temperatures, graphite filler is also used.
Alternate winding materials can also be used depending upon the services. ANSI B 16.5 do not
recommend the use of 150# rating spiral wound gaskets on flanges other than welding neck type.
Spiral wound gaskets are provided with carbon steel external ring known as centering ring to position to
gasket. When used in vacuum services, an internal ring is also provided. The material of inner ring should
be compatible with the fluid.
 Dimensional Standards
Gasket dimensions are covered under the following standards.
API 601 - Metallic Gasket for Refinery Piping
BS 3381 - Metallic spiral wound gaskets
ANSI B 16.20 - Metallic Gasket for Pipe flanges
Tounge and Groove Flange Expander or Increaser Flange

ANSI B 16.21 - Non-Metallic Gasket for Pipe flanges
1.23 BOLTING
Depending upon the service, its pressure/ temperature and the type of gasket, type of bolting is selected. For
low pressure, low temperature services, machined bolts are used and studs are used otherwise. Normally, the
bolts are provided with hexagonal head, hexagonal nut and a round washer. Studs are provided with two
hexagonal nut and two washers. The length of bolts and nuts required for the flange joints of all pressure
classes are specified in the ASME B 16.5 .ASTM F-704 specifies the standard practice of selecting bolt lengths
for piping system flanged joints.
Flanged joints using low strength carbon steel bolts shall not be used above 200°C or below -29°C.
1. Material of Construction for Bolting
Bolting materials used normally are:
ASTM A 307 - Low carbon steel bolting material
ASTM A 320 - Alloy steel bolting for material for high temperature services
ASTM A 193 - Alloy steel bolting for material for high temperature services
ASTM A 194 - Alloy steel nut material for high temperature service.
IS 1367 - Threaded steel fasteners
2. Dimensional Standards for Bolts
ANSI B 18.2.1 - Square & Hexagonal Head bolts
ANSI B 18.2.2 - Square & Hex nuts
BS 916 - Black bolts & nuts
IS 1367 - Threaded steel fasteners.
1.24 INTRODUCTION TO NON FERROUS PIPING AND PIPING SYMBOLS
The non ferrous piping is used depending upon the corrosion properties and the temperature at which the
fluid is handled. Special technology is involved in the fabrication of these piping. The commonly used
materials are :
Aluminium, Alloy-20, Hastalloy, Lead, Monel, Nickel and Titanium
These materials are specified under ASTM section II part B and the numbers are prefixed with the alphabet ‘B’.
Due to economic considerations either carbon steel flanges with lining/ bonding of these materials or lap joint
backing flanges wherever possible are used in this piping.
1.25 NON METALLIC
Non metallic piping is used where the problem of corrosion is severe and it is difficult to get a suitable
economical metallic piping. Temperature limitations restrict the use of these non-metallic piping. The most
commonly used materials are:
ABS- Acrylonitrile-Butadiene-styrene
CPCV- Chlorinated Polyvinyl chloride
ETFE- Ethylene Tetraethylene
FEP - Fluoro Ethylene propylene
FRP- Fibreglass reinforced plastic
HDPE- High density polyethylene
LDPE- Low density polyethylene
PFA- Perfluoro Alkoxyalkane

PP - Polypropylene
PTFE- Polytetrafluoroethylene
PVC- Poly vinyl chloride
PVDF- Polyvinyliedene Flouride
1.26 LINED PIPING
1.18.1 Glass
1.18.2 Cement
1.18.3 Ceramic
1.18.4 Rubber
1.18.5 Wood
1.18.6 Plastic
The lined pipes and pipe fittings have flanged ends and are joined by bolting. Of late flangeless lined piping is
used. In this case the liner is butt-welded and the outer carbon steel of the pipe is connected by ‘lorking’
mechanical coupling.
The use of gasket is not recommended in the use of piping lined with resilient materials, but this can damage
the lining. The glass pipes & fittings have either buttress end or beaded ends and are connected with flanged
assembly.
1.27 PIPING SPECIFICATION/ PIPING CLASS -- PREPERATION
A document indicating the dimensional and material specifications of pipe, fittings and valve types is called a
PIPING CLASS. Each class represents distinct features such as pressure-temperature conditions, corrosion
resistance and strength abilities or a combination of these abilities. There could be a number of them selected
and used for one project. While selecting care should be taken to minimize the number to rationalize the stock
facilities. The designation of these piping classes varies with the company. While designing the piping system
for a project, the component which is not mentioned in the piping class should be avoided.
Preparation of piping specification
Materials
1.19.1 Carbon steel shall be used for temperature upon 425°C (800°) only.
1.19.2 Low temperature shall be used for temperature below -29°C (-29°F)
1.19.3 Alloy steel shall be used for corrosive fluids. Basic material of construction specified by Process
Licensor to be referred for the type.
1.19.4 Galvanized steel piping shall be used for services such as drinking water, instrument air, nitrogen (LP)
etc.
1.19.5 Selection of Non- ferrous and non metallic / Lined piping shall be as per the recommendation
from the process Licensor.
Piping Joints
1.20.1 Butt welded connections shall normally be used for all Alloy/Carbon steel piping 2”NB and
larger.
1.20.2 Alloy/carbon steel piping 1 ½” NB and below shall be socket welded.
1.20.3 Threaded connections shall be avoided except in galvanized piping.
1.20.4 Flanged joints shall be minimized as it is a point of potential leakage. It may be used to
connect piping to equipment or valves, connecting pipe lines of dissimilar materials, where spool
pieces are required to permit removal of servicing of equipment and where pipes and fittings are with
flanged ends.

1.28 PIPING COMPONENTS
1. Pipes
1.23.1 All pipe lines carrying toxic/ inflammable fluids shall be seamless.
1.23.2 Utility piping can be ERW or seam welded.
1.23.3 Steam pipe lines shall preferably be seamless.
2. Fittings
1.28.1 Fittings shall preferably be seamless.
1.28.2 Butt weld fittings shall be used for pipe sizes 2” NB and above for all Alloy/carbon steel piping.
1.28.3 For stainless steel piping where thickness is less, all fittings could be butt welding type.
1.28.4 Welding tees shall be used for full size branch connections and for reduced branch sizes up to
less than run diameter it can be fabricated. For smaller sizes half couplings shall be used. Full size
reinforced branch welding can be done where pressure temperature conditions are low.
3. Flanges
1. Rating shall be based on the pressure-temperature conditions. However 150lb Flanges are not permitted
beyond 200°C (400°F).
2. Screwed flanges shall be used for galvanized steel/cast iron piping
3. Socket welding flanges may be used for all pressure ratings up to 1 1/2 “ (40mm)NB size except on
lines subjected to severe cyclic conditions.
4. Slip-on flanges shall be used for galvanized steel/cast iron piping.
5. Flat faced flanges are used to mate with Cast iron valves and equipments.
6. Raised face is used for flanges up to 600lb rating. For flanges 900Lb rating and above RTJ is recommended.
Tongue and groove facing shall be used selectively.
7. Depending on pressure and temperature, gasket shall be either CAF, spiral wound metallic for raised face
flanges or selected based on the corrosive nature of the fluid.
8. Use Spiral wound gasket with inner ring for vacuum service. Low strength carbon steel bolting shall not be
used above 200°C and below -29°C.

Process Equipment Symbols

Symbols for Butt-Welded Systems

Symbols for Valves and Valve Operators

Miscellaneous Symbols for Piping Drawings

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