Power Plant Pipings-rajeshk

7/29/2019 Power Plant Pipings-rajeshk

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POWER PLANT PIPINGS

Rajesh Kumdale Pune India

[email protected]


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INTRODUCTION

The plant and systems are designed to achieve the best possible efficiency under the specifiedoperating conditions. The Power Cycle shall be designed with one low pressure feed waterheater (de-aerator). The steam requirement of the de-aerator shall be met from the bleed of the

turbine.

The cooling medium is filtered water, which is circulated through a cooling tower. The water issupplied by owner at the terminal point (Raw Water Tank) from where it will pumped at therequired pressure to the Cooling Tower. The cooling water temperature considered is 32 Deg Cwith a temperature rise of 8 Deg C across the Condenser. The Design wet bulb temperature forthe cooling tower has been considered as 27 Deg C. The efficiency of the Power plant isdeepens upon the water.

The required quantity of raw water shall be stored in the raw water tank of capacity 1500 m3.We have considered river water oflow hardness as CaCO3 and negligible Silica as SiO3for the water treatment plant design. This is the basis for the selection of the multi-grade filter /RO plant and DM water treatment plant. Any change in the limits of this water analysis willimpact the water treatment plant design and cost. We have not considered water softeningplant for cooling tower.

The raw water after filtration and required dosing will be taken to the cooling tower (make up)

for the condenser cooling water system. For the boiler makeup, the filtered water will be takenthrough the RO/DM Water treatment plant and then stored in the DM water storage tank of 20m3. The boiler make up water stream is designed for 2 m3 / hr capacity. In case if any otherwater source is available for the power plant, the same may be indicated to us for design.


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INPUT CONDITIONS

Ambient conditions and other inputs (assumed)

Temperatures :

Design temperature for performance : 35 Deg C

Design Temperature for Electrical : 45 Deg C

Relative Humidity :

Plant Design Relative Humidity : 65.0% Design Wind Velocity : As per IS: 875

Seismic Coefficient : As per IS: 1893

Soil Bearing Capacity at 2.0 m Depth : 20 T/m2

(To be reconfirmed after site location is finalized & soil investigationsare conducted)

Cooling Water temperature : 32 Deg C


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FEED WATER SYSTEM

Boiler Feed water pumps (2 Nos.) complete withcoupling, base frame and drives arrangement.

Feed regulating station for maintaining uniform level ofwater in steam drum.

Stand by flow path of 100% capacity.

Feed pump re-circulation flow under low feed pump flowconditions by automatically controlled solenoid valveinstalled in between feed pump and de-aerator.

Strainers at the suction of feed water pump.

Feed line from de-aerator to feed pump suction, feedpump discharge to economizer and from economizer tosteam drum.


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DE-AERATOR CUM STORAGE TANK

De-aerator with de-aerated water storage tank.

Minimum and essential valves and fittings. Saddle support for placement of de-aerator on

control room top.

Level control valve with required isolation.

Pressure control valve with required isolation. Feed water piping from de-aerator outlet to feed

pump suction.

Feed water piping from the outlet of level control

station to de-aerator. Steam piping from the outlet of pressure control

station to de-aerator.


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DEAERATION TANK

SPECFICATION Type :Horizontal spray type

Design code :As per US standards

Design pressure :22.0 Kg/cm

Design material temperature :200 Deg. C.

Storage tank capacity at NWLm316 Deaeration capacitym3/hr.60

Hydraulic test pressure :24 Kg/cm

Operating temperature :120 Deg.C.

Operating pressure : 0.35 Kg/cm2 Deaerator water inlet temp. :45 Deg.C.

Deaerator water outlet temp. :120 Deg.C.

Oxygen content in deaerator water :0.01 ppm


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WATER REQUIREMENT

The raw water shall be from the day storage hold up, under groundtank (owners scope) of 2000 m3 capacity (1500 m3 for Power Plantand 500 m3 for fire fighting) and supplied at the inlet to the rawwater pumps and passed through multi grade filter (MGF) at 3.5kg/cm2. One stream of the filtered water shall be taken to theCooling Tower. The other stream shall be taken to RO / DM Plant as

per the scheme. The chlorine dozing system shall be provided to prevent Algae

formation and Bacteria.

The Raw Water is pumped by the Filter Feed Pump through theMulti Grade Sand Filter (MGF) for the removal of Suspended Solids.The unit consists of quartz sand media for the purpose. The unit

should be backwashed in a day or whenever the pressure dropexceeds 0.8 Kg/cm2, whichever is earlier.


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WATER PROPERITES

Hardness (ppm) : 0

pH @ 250C : 8.8 9.2 (after pH correction)

Conductivity @ 250C : 0.5 (microsiemen / Cm)

Total Silica (maximum) (ppm): 0.02

Residual Hydrazine (ppm) : 0.01 0.02


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PIPING & PIPING MATERIALS

All piping system will be designed as per ASME B 31.1 and IBR.

Stress Analysis shall be carried out for all critical piping as per ASME B 31.1 / IBRrequirements.

Supports, Spring Supports, guides, directional anchors will be selected to satisfy allthe operating conditions.

Drains and traps will be provided as required.

The piping material selection will be based on the following recommendations

For temperature above 4240C up to 5100C - SA 335 Gr. P11 / P12 will be used

For temperature up to 4240C - SA 106 Gr. B will be used

For HP / LP chemical dosing - - SA 312 TP 304, stainless steel willbe used.

For cooling Water, Raw Water, Service Water, Safety / Relief Valve Exhaust

IS:1239 / IS:3589 ERW / EFW pipeswill be used.

For service air applications, the piping will be - IS:1239.

For instrument air applications: Galvanized pipe (Iron Pipe)- IS:1239 Part I will be used.


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PIPING

Codes, Standards & Regulations

ASME

DIN

TRD

BS

IBR


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Codes and Standards:

Several groups have written codes and

standards for materials, inspection, design,

stress analysis, fabrication, heat treatment,welding and construction of pipes and piping

components. Regulations, practices, rules and

laws are also available for use of piping. Certain

aspects are mandatory and certain aspects arerecommendatory. The commonly used

American Codes and Standards on piping


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1. ASME B31.1 -Power Piping

2. ASME B31.2 -Fuel Gas Piping

3. ASME B31.3 -Process Piping

4. ASME B31.4 -Pipeline Transportation Systems for Liquid

Hydrocarbons and other Liquids.5. ASME B31.5 -Refrigeration Piping

6. ASME B31.8 -Gas Transmission and Distribution Piping

Systems

7. ASME B31.9 - Building Services Piping8. ASME B31.11 - Slurry Transportation Piping Systems.


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Through the use of codes and standards, safety and uniform economyare obtained. The codes and standards primarily cover the followingaspects:

1. Factors safety

2. Material property

3. Thickness calculation

4. Loads

5. Load combinations

6. Stress limits

7. Stress intensification factors

8. Flexibility factors

9. Supports

10. Flexibility analysis.

COMPARISON OF CODES


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IBR 1950 ASME SEC.I BS 1113 DIN TRD 300 REMARKS

DESIGN PRESSURE DESIGN PRESSUREWITH PRESSURE

DROPDRUM DESIGN

PRESSURE DRUM DESIGNPERSSURE DRUM DESIGNPRESSUREDESIGN

TEMPERATUE

ALLOWANCE

RADIATION50C

ACTUAL METAL

TEMPERATURE

371C (MIN)

50C 50C

CONVECTION 39C 35C 35C

ECONOMISER 11C 25C (15 + 2 Se) CMax. 50C Se - ACTUAL WALLTHICKNESS in mm.

WATER WALL 28C 50C 50C

TUBE THICKNESS

FORMULA tminPD

--------- + *C2f + P

PD--------- + 0.005D2f + P

PD---------

2f + PPD

---------

2f + P

P=DESIGN PR.

D=OUTSIDE DIAf=ALLOWABLE STRESS

CORR. TO DESIGN

METAL TEMP.

FACTOR OF SAFETY Et R1.5 , 2.7SR SC1.5

Et R

1.5 , 3.5SR SC1.5

Et R

1.5 , 2.7SR1.3

Et R

1.5 , 2.4SR1.0

Et = YIELD STRENGTHR = TENSILE STRENGTHSR = RUPTURE

STRENGTHSC = CREEP STRENGTH

FOR ASME MATERIALS ALLOWABLE STRESS CAN BE TAKEN DIRECTLY FROM ASME SEC.II PART-D

COMPARISON OF CODES

*C = CORROSION ALLOWANCE = 0.75mm FOR P 70 bar; 0 mm FOR P > 70 bar


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Sl. Nominal MATERIAL SPECIFICATION Temp.No. Composition ASME Section-I DIN TRD 300 BS 1113 Limit C

01. Carbon Steel SA178 Gr.C, Gr.D,SA192, SA210 Gr.A1& Gr.CSA106 Gr.B, Gr.C

St 35.8St 45.8 BS3059 P2 S2 360, 440BS3602 P1 360, 430, 500Nb

427

02. Mo SA209 T1 15 Mo3 ( TUBE) ---- 482

03. 1 Cr Mo SA335 P12SA213 T12 13 Cr Mo 44 BS3059 P2 S2 620BS3604 P1 620 440 535

04. 1 Cr Mo SA213 T11SA335 P11 ---- BS3604 P1, 621 552

05. 2 Cr 1 Mo SA213 T22SA335 P22 10 Cr Mo 910 BS3059 P2 S2 622-490BS3604 P1, 622 577

06. 9 Cr 1 Mo V SA213 T91SA335 P91

X 10 Cr Mo V

Nb91----- 635

07. Carbon steel ASTM A 53 Gr B ST 32 325

08. 18 Cr 8 Ni SA213 TP304 H ----- BS3059 P2 304 S51BS3605 304 S59 E 704

09. 18 Cr 10 Ni Cb SA213 TP347 H ----- BS3059 P2 347 S51BS3605 347 S59 E 704

TEMPERATURE LIMITS FOR VARIOUS STEEL GRADES OF TUBES / PIPES


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AREA IBR ASME SEC.I BS 1113 DIN TRD 300

Tubethickness

PD+ C

2f + P

PD+0.005D

2f + P

PD

2f + P

PD

2f + P

Shellthickness

PR+ 0.75

fE 0.5 P

PR

fE (1 Y) P

PR

fE 0.5 P

PR

fE 0.5 PE

Dished end

thickness

PDK+ 0.75

2f

PR

2f

0.2 P

PDK

2f

2PR 1+ 1

2f

P

Flat endthickness

CPd + C

f

CPd

fP

Cdf

PCd

f

DESIGN - CALCULATION OF THICKNESS REQUIRED IN VARIOUS CODES


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Diameter and Thickness:

The diameter of the piping is usually decided

based on flow and heat transfer considerations.

In normal practice, the outside diameter isspecified for procurement. These are based on

the convenience and convention in manufacture.

After finalizing the diameter, the thickness of the

piping is computed based on the imposed loads.

PIPING


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PIPING

Diameter

Based on flow requirements

Based on economic requirements

Based on size availability


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PIPING

Thickness

Based on strength requirement

Based on process allowances

Based on thickness tolerances

Based on availability


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Fluids and Pressure Drop:

The piping under present discussion may carry a single-phase fluid or two-phase fluid. The following fluids arecommonly handled by the piping:

1. Liquid 2. Gas 3. Liquid-solid slurry 4. Gas-solid mixture 5. Liquid-vapor mixture.

PIPING


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Mixture of solids, liquids and gases are rarely

used. In a maze of piping, flow distribution plays

a major role in the design of piping. To calculate

the flow in various branches of piping (in a mazeof piping), the pressure drop in various branches

are to be calculated. The following formula is

commonly used to calculate the pressure drop in

a fully developed flow in a hollow circular pipe.

PIPING


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f W2 L

P = ----------

2gd

Where,

P = Pressure loss in terms of head, mm of fluid column f = Coefficient of friction

W = Velocity of fluid, mm / sec.

L = Total length of pipe, mm

g = Acceleration due to gravity = 9806.65 mm/sec2

d = Average inside diameter of pipe, mm

PIPING


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The following formula is commonly used calculate the pumpingpower required:

P p WA

HP = ---------------

75 x 109

Where

HP = Pumping power, HP

p = Density of fluid, gm/cc

A = Flow area = d2 / 4 Sq.mm

Example (Water at ambient temperature)

PIPING


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Flow = 100 tonne / hr = 100 cu. m / hr = 100 / 3600 = 0.0278 cu.m / sec

d = 102.26 mm (for 4 STD pipe = 114.3 x 6.02 mm x mm) W = 0.0278 / ( * 0.102262 / 4) = 3.38 m / sec = 3.380 mm / sec L = 100 m = 100,000 mm

f = 0.02 (approximate)

p = 1.0 gm / cc (for water at ambient temperature)

P = 0.02 * 33802 * 100,000 / (2 * 9806.65 * 102.26) = 11.392 mm water column

P p W A (11.392 mm wc) x (1.0 gm/cc) x 3.380 mm/sec) x (8.213 sq.mm)

HP = --------------- = --------------------------------------------------------------------------------------

75 x 109 75 x 109

= 4.22 HP. Considering a motor efficiency of 80%, motor rating = 4.22/08 = 5.28 HP.

Use a 6 HP Motor.

PIPING


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Nominal Pipe Size (NPS):

The Nominal Pipe Size (NPS) in an ASME method of indicating the

approximate outside diameter of the connected pipe in inches. Note

that the unit (inch) is not followed after the designation.

Class of Fittings:

The class of fittings is an ASME method of indicating the pressure

carrying capacity of the fittings.

PIPING


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I. Pipe sizing and Pressure drop Calculations:

Pipe Sizing:

Before proceeding beyond a preliminary / design of pipingsystem, it is necessary to determine the pipe inside diameter which

allow reasonable velocities and friction losses. The maximum

allowable velocities of the fluid in pipeline is that which corresponds

to the permissible pressure drop from the point of supply to the point

of consumption or is that which does not result in excessive pipe lineerosion.

PIPING


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Trade Practice Steel pipes are designated by their OD or theirNominal ID.

Due to manufacturing conditions, OD is constant.

Slight deviations from normal wall thickness, modify only the ID alsocalled clear width.

Why a pipe is generally not referred to by its ID.

Common Engineering practice to use nominal bore NB to indicate theproper size of the individual parts employed in a pipeline (pipes, flanges,fittings and valves).

Nominal bore = actual inside diameter.

PIPING


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Selection of the diameter (flow rate anticipated pressure headavailable).

Pressure head (provided by booster pumps, compressors, naturalhead as in the case of gravity main).

Pressure head is necessary for transmission to overcome losses in

the flow rate due to internal friction in the moving fluid or to rough insidesurfaces of pipe.

Pressure drop increased through turbulence and separation of flow ofbends or in branch connections, fittings, valves and similar parts (reduce theeconomy of any pipe line.

PIPING


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Velocity profile in Different System:

The mean velocities of steam and water in different system

shall be as follows:

PIPING


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Q = A W

A = --------- d2

4

354025 x Qv

d = --------------------

w

Where A = Area, mm2

PIPING


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d = inside diameter, mm

Q = flow rate, Tonnes/hr.

w = Velocity, m/sec

= Volume of medium, Kg/m3

Pressure drop calculation:

The pipe sizes calculated based on the above recommended

velocities do not relieve the designer to check the adequacy of pipesize from the flow friction consideration.

PIPING


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Pressu re drop calculat ions are of p r ime necessi ty indetermining:

a) The selected inside diameter meets the available

pressure drop in the case of main steam, cold reheat,hot reheat and auxiliary steam lines and miscellaneouswater lines.

b) The discharge pressure of the pump (boiler feedpump and condensate extraction pump).

PIPING


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For finding the frictional pressure drop in pipelines

Darcys Formula can be universally used for almost all

the fluids. With suitable restrictions for gases and

vapours. As long as the pressure drop is around 10% of

starting point pressure (which is true in most of thesteam lines in thermal power station). Darcys formula

for pressure drop can be used since the specific volume

change in the line due to pressure loss will have little

effect on calculated pressure drop.

PIPING


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Calculat ion to determin e the pressure drop in the pipe is madeaccord ing to formula:

a) For straight pipe

flw2

P = ----------------- kg/cm2

20000 g c dv

b) For bends, elbows, tees, valves, etc. Kw2

P = ----------------- kg/cm2

20000 g c v

PIPING


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Where,

f= Friction factor found from a graph between Reynolds No. and

Relative roughness.

K= resistance coefficient for fittings there are established based on

experiments and are available in a standard table in various books.

l= length of pipe in meters

V= velocity in m/sec

gc= gravitational constant 9.81 m/sec2

d= inside diameter of pipe in meter

v= specific volume in m3/sec.

PIPING


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a) Water (non-expansive flow) in compressible fluids.

l w2 x

P= ---- x ------------ h x

di 2g

P= absolute pressure in lb/ft2

l= length of pipe line in ft.

di= inside diameter of pipe in ft.

PIPING


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w= velocity of flow in ft/sec

= specific gravity in lb/cu.ft (water = 62 lb/cu.ft)

g= acceleration due to gravity (=32.2 ft/sec2)

h= geodesic height in ft for lines other than horizontal

= friction factor number dimension

+= ascending lines

= descending lines

0= for horizontal lines.

Pressure decreases in linear perspective with the lengthof the line, while the velocity remains unchanged.

PIPING

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