POWER PLANT PIPINGS

INTRODUCTION

The plant and systems are designed to achieve the best possible efficiency under the specified operating conditions. The Power Cycle shall be designed with one low pressure feed water heater (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 is supplied by owner at the terminal point (Raw Water Tank) from where it will pumped at the required pressure to the Cooling Tower. The cooling water temperature considered is 32 Deg C with a temperature rise of 8 Deg C across the Condenser. The Design wet bulb temperature for the cooling tower has been considered as 27 Deg C. The efficiency of the Power plant is deepens 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 of low hardness as CaCO3 and negligible Silica as SiO3 for 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 will impact the water treatment plant design and cost. We have not considered water softening plant 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 taken through the RO/DM Water treatment plant and then stored in the DM water storage tank of 20 m3. The boiler make up water stream is designed for 2 m3 / hr capacity. In case if any other water source is available for the power plant, the same may be indicated to us for design.

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 investigations

are conducted)• Cooling Water temperature : 32 Deg C

FEED WATER SYSTEM

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

• Feed regulating station for maintaining uniform level of water in steam drum.

• Stand by flow path of 100% capacity.• Feed pump re-circulation flow under low feed pump flow

conditions by automatically controlled solenoid valve installed in between feed pump and de-aerator.

• Strainers at the suction of feed water pump. • Feed line from de-aerator to feed pump suction, feed

pump discharge to economizer and from economizer to steam drum.

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.

DEAERATION TANKSPECFICATION

• 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

WATER REQUIREMENT

• The raw water shall be from the day storage hold up, under ground tank (owners scope) of 2000 m3 capacity (1500 m3 for Power Plant and 500 m3 for fire fighting) and supplied at the inlet to the raw water pumps and passed through multi grade filter (MGF) at 3.5 kg/cm2. One stream of the filtered water shall be taken to the Cooling 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 the Multi 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 drop exceeds 0.8 Kg/cm2, whichever is earlier.

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

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 / IBR

requirements. • Supports, Spring Supports, guides, directional anchors will be selected to satisfy all

the 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 will

be used.• For cooling Water, Raw Water, Service Water, Safety / Relief Valve Exhaust • – IS:1239 / IS:3589 ERW / EFW

pipes will 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.

PIPING

• Codes, Standards & Regulations– ASME– DIN– TRD– BS– IBR

• 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 are recommendatory. The commonly used American Codes and Standards on piping

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 Piping

8. ASME B31.11 - Slurry Transportation Piping Systems.

Through the use of codes and standards, safety and uniform economy are obtained. The codes and standards primarily cover the following aspects:

1.      Factors safety2.      Material property3.      Thickness calculation4.      Loads5.      Load combinations6.      Stress limits7.      Stress intensification factors8.      Flexibility factors9.      Supports10.   Flexibility analysis.

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

DESIGN PRESSURE

DESIGN PRESSURE

WITH PRESSURE DROP

DRUM DESIGN

PRESSURE

DRUM DESIGN

PERSSURE

DRUM DESIGN

PRESSURE

 

DESIGN TEMPERATUE ALLOWANCE RADIATION

50C

ACTUAL METAL TEMPERATURE

371C (MIN)

50C

50C

 

CONVECTION

39C

35C

35C

 

ECONOMISER

11C

25C

(15 + 2 Se) C

Max. 50C

Se - ACTUAL WALL THICKNESS in mm.

WATER WALL

28C

50C

50C

 

TUBE THICKNESS

FORMULA tmin

PD--------- + *C2f + P 

PD--------- + 0.005D2f + P 

PD--------- 2f + P 

PD--------- 2f + P 

P=DESIGN PR.D=OUTSIDE DIAf=ALLOWABLE STRESS CORR. TO DESIGN METAL TEMP.

FACTOR OF SAFETY

Et R 1.5 , 2.7 SR SC 1.5

Et R 1.5 , 3.5 SR SC 1.5

Et R 1.5 , 2.7 SR 1.3

Et R 1.5 , 2.4 SR 1.0

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

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, 500 Nb

 427 

 02.

 ½ Mo

 SA209 T1

 15 Mo3

 ----

 482

 03.

 1 Cr ½ Mo

 SA335 P12SA213 T12

 13 Cr Mo 44

 BS3059 P2 S2 620BS3604 P1 620 – 440

 535

 04.

 1¼ Cr ½ Mo

 SA213 T11SA335 P11

 ----

 BS3604 P1, 621

 552

 05.

 2¼ Cr 1 Mo

 SA213 T22SA335 P22

 10 Cr Mo 910

 BS3059 P2 S2 622-490BS3604 P1, 622

 577

 06.

 9 Cr 1 Mo ¼ V

 SA213 T91SA335 P91

 X 10 Cr Mo V Nb91

 -----

 635

 07.

 12 Cr 1 Mo ¼ V

 -----

 X 20 Cr Mo V 121

 BS3059 P2 S2 762BS3604 P1 762

 700

 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

 AREA

 IBR

 ASME SEC.I

 BS 1113

 DIN TRD 300

 

 Tube thickness

  PD + C 2f + P

  PD +0.005D 2f + P

  PD

2f + P

  PD

2f + P 

 Shell thickness 

  PR + 0.75fE 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 end thickness

CPd + C f

  CPd f

PCd f

PCd f

DESIGN - CALCULATION OF THICKNESS REQUIRED IN VARIOUS CODES

• Diameter and Thickness:•  The diameter of the piping is usually decided

based on flow and heat transfer considerations. In normal practice, the outside diameter is specified 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

PIPING

• Diameter– Based on flow requirements– Based on economic requirements– Based on size availability

PIPING

• Thickness– Based on strength requirement– Based on process allowances– Based on thickness tolerances– Based on availability

• Fluids and Pressure Drop:• The piping under present discussion may carry a single-

phase fluid or two-phase fluid. The following fluids are commonly handled by the piping:

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

PIPING

• 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 maze of 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

• 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

• The following formula is commonly used calculate the pumping power 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

• 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

• 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

• I. Pipe sizing and Pressure drop Calculations:•  • Pipe Sizing:•  • Before proceeding beyond a preliminary / design of piping

system, 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 line erosion.

PIPING

• Trade Practice – Steel pipes are designated by their OD or their Nominal ID.

•  • §         Due to manufacturing conditions, OD is constant.•  • §         Slight deviations from normal wall thickness, modify only the ID also

called clear width.•  • §         Why a pipe is generally not referred to by its ID.•  • §         Common Engineering practice to use nominal bore NB to indicate the

proper size of the individual parts employed in a pipeline (pipes, flanges, fittings and valves).

•  • §         Nominal bore = actual inside diameter.•  

PIPING

• §         Selection of the diameter (flow rate anticipated pressure head available).

•  • §         Pressure head (provided by booster pumps, compressors, natural

head 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 inside surfaces of pipe.

•  • §         Pressure drop increased through turbulence and separation of flow of

bends or in branch connections, fittings, valves and similar parts (reduce the economy of any pipe line.

•  •  

PIPING

• Velocity profile in Different System:•  • The mean velocities of steam and water in different system

shall be as follows:

PIPING

•  • Q = A W•  • • A = --------- d2

• 4•  • 354025 x Qv• d = --------------------• w•  • Where A = Area, mm2

•  •

PIPING

• d = inside diameter, mm•  • Q = flow rate, Tonnes/hr.•  • w = Velocity, m/sec•  • r        = 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 pipe size from the flow friction consideration.

PIPING

• Pressure drop calculations are of prime necessity in determining:

•  • 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 miscellaneous water lines.

•  • b)   The discharge pressure of the pump (boiler feed

pump and condensate extraction pump).•  

PIPING

• For finding the frictional pressure drop in pipelines Darcy’s 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 the steam lines in thermal power station). Darcy’s 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

• Calculation to determine the pressure drop in the pipe is made according 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

• 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

• 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

• 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 length

of the line, while the velocity remains unchanged.

PIPING