10erpip

STEAM TURBINE500 MW

ERECTION

SPECIFICATIONS FOR ERECTION OF PIPING

1 ERECTION OF PIPING

NOTE: These guidelines are intended to provide advice to lay and

support pipings at site, especially non-prefabricated pipes < Nb

50.

1.1 GENERAL

These guidelines apply to turbine and generator piping forming part of

the BHEL scope of supply and delivered to the site in the form of

prefabricated pipe sections and straight lengths of piping.

Generally Applicable Specifications

Prefabricated lines > Nb 50

In case of deviation the site erection engineer to decide in alternate

routing.

1.2 LAYING OF PIPES WITH ROUTING SPECIFIED IN PIPING PLAN.

1 Lay the lines as specified in the piping plans.

2 Support them at the defined points.

3 Cold bending method and special pipe-bending equipment should

be used for bending of pipes.

4 Care should be taken to ensure that the deformation is well within

the tolerance limits.

1.3 ACCOMMODATION OF MOVEMENT AND EXPANSION.

1 Care is to be taken to ensure the movements at pipe terminals

and thermal expansion of the pipes themselves are

Bharat Heavy Electricals LimitedRev 00, 7-98

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2 accommodated by adequately long legs and expansion loops.

3 For lines connected to emergency stop valves (main steam valve,

stop valve, bypass valve ) allowance of ± 20 mm in all

directions shall be made.

4 Determine with the aid of the diagram (Fig. 1 & 2 ) the pipe legs

required to accommodate terminal movement and thermal

expansion.

5 Ensure the valid coordinate system of that power plant (Fig 13) is

adhered.

6 If it is not possible to obtain values for movement of the terminal

point taken from Fig 14, add a 50% safety margin to the

thermal expansion calculated for the connecting pipe Figs 3 &

4.

1.4 ASCENDING AND DESCENDING GRADIENTS

1 Install all lines with the ascending or descending gradients

appropriate to their function.

2 Lay supply lines with a constant ascending or descending gradient

- at least 5 mm/m - with at the very least a 5O slope (-90

mm/m).

3 Lay drain and vent lines with a descending gradient of a least 20

mm/m.

1.5 PIPE SUPPORTS


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1 Pipe supports should not restrict pipe movements. Where spring-

loaded supports are used, the additional load or load relief

exerted by spring force on the pipeline at maximum deflection

from its unloaded position should not exceed 25% of the

supported pipe weight. (Fig. 6).

2 The Table (Fig. 5) gives reference values for pipe supports.

3 When fabricated pipe supports and guides, only flat steel pipe

clamps and aluminum clamps serve as the pipe bearing

surface.

4 The use of round -steel shackles should be avoided in all cases.

ATTENTION: Suspension supports are to be preferred to support

from beneath. Friction points should be avoided.

2 WELD PREPARATIONS AND WELDING OF PREFABRICATED

AND NON-PREFABRICATED PIPES.

2.1 WELD PREPARATIONS

1 Ensure proper edge preparation as per drgs.

2 Remove scale, rust, paint etc. from weld joints.

2.2 WELDING

1 Complete welding as per WPS/drgs.

2 Nitrogen purging to be done wherever required.

3 Complete N.D.T.


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2.3 SPECIAL SYSTEM REQUIREMENTS

Lubricating Oil System

1 Match up, weld and examine the prefabricated connecting pieces

of the discharge and suction nozzles prior to the final erection

of the first bearing pedestal.

2 Other matching and welding work to be done when the bearing

pedestal is full assembled.

3 The direction of flow of the oil temperature control valve should be

ensured as indicated by markings on the valve itself.

Jacking Oil Lines

4 Where possible, lay jacking oil lines so as to be protected by other

lines of larger nominal diameters against being used as an aid

to climbing.

5 Once the line has been welded to the bearing pedestal, fit a

protection plate to protect the line in this area.

6 Oil Vapor extraction lines

7 Ensure that oil vapor extraction lines are laid with a gradient

descending constancy towards the main oil tank without low

points. A drain loop at the lower end of this line upstream from

the blowers return drains to the oil tank.

8 Fire Prevention

9 To avoid fire hazards, do not route oil lines near lines or

components at high temperature.


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10 If the laying of oil lines in these areas cannot be avoided, ensure

that no detachable connections or valves are erected directly

above high-temperature lines or components.

Control Fluid System

Single Fluid Lines

11 Signal fluid lines comprise all those lines in which some

kind of signal or pulse is transmitted from one point to

another (in other words, almost all fluid lines which do

not lead directly from pump via filter to component).

These includes : primary oil lines, secondary auxiliary

secondary and bypass signal fluidlines, trip, auxiliary

trip, test and return fluid lines, by[pass startup fluid

lines, and water filled (condensate-filled) impulse lines.

12 They do not include : turbine start-up and auxiliary start-up

oil lines, pilot fluid line (between pressure transducer

and pilot valve on Nb200 and Nb250 bypass stop

valves with LP hydraulic system).

13 To ensure correct functioning of signal fluid lines, lay them

with an adequate ascending or descending gradient to

prevent air pockets from forming and accumulating. A

number of different routing strategies are available for

this purpose (the control medium flows from the control

equipment) Fig. 7.


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Version 1.

If a line is installed from the control equipment to the load with

an ascending gradient (ascending in the direction of flow)

there must be a minimum gradient of 67 mm Fig. 7.

Version 2.

If a line is installed from the control equipment to the load with

a descending gradient (ascending gradient counter to the

direction of flow) there must be a minimum gradient of 175

mm/m Fig. 7.

If it is not possible to install the line as shown in Version 1&2,

two other strategies may be adopted (Fig.8)

Version 3.

If local conditions make it necessary to install the line with one

or more high points, each high point must be provided with

permanent venting facilities (orifices with a diameter of 1.5mm).

Fig.8.

Version 4.

If local conditions make it impossible to observe the 10OC

minimum gradient in installing a line as shown in Version-2, then

reduce the gradient required from 175 mm/m to 67 mm/m by

introducing an external supply to reverse the direction of flow

Fig.8.

Installation of Damping Devices


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14 The as-installed configuration of each damping device is indicated

in symbolic form on the system flow chart. As the flow is

generally directed via the installed orifice plate, i.e. pressing

the ball downward against the valve seat, care must be taken

to interpret the symbol correctly.

If the system flow chart indicates that the damping device should

be installed as shown in Fig.9 the flow passes via the orifice plate

(slow flow) if the damping device is to be installed the other way

around the ball is lifted away from the seat and thus permits a

rapid through - flow.

3 SEAL STEAM SYSTEM

3.1 Seal Steam Lines, valve Stem Steam Leak-Off Lines and Seal Ring

Steam Leak-Off Lines.

1 In laying these lines, provide sufficient compensation for thermal

expansion. The service temperature for all lines can be assumed

to be approximately 450OC. These pipes expand by approximately

6 mm/m between the cold state (initial temperature 20OC) and the

hot state.

ATTENTION : Always include a safety margin.


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3.2 Leak-Off and Seal Steam Extraction Lines in the Steam Seal

Casings.

1 Insert leak-off and seal steam lines, though the pipe penetrations

in the LP end walls before mounting the LP bearing pedestals.

Connect the lines up when the LP steam seal casings have

been fully assembled.

2 Ensure that the lines are concentric within the penetrations to

accommodate the insulation to be installed subsequently.


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3.3 Pressure Sensing Line Terminals for the Seal Steam Control

system

1 Erect the pulse lines to the pressure transducers in a manner

which will prevent the generation of fluctuating pressure

pulses. Refer Fig.12.

2 Lay the header, with an ascending gradient from the terminal point

to the pressure transducers, making sure that the pipe leg

below the transducers has a gradient of 30OC.

3 From this pipe leg, in which two Nb 25 nozzles are welded, erect

two lines 500 mm long, to the pressure gauge cutoff valves of

the pressure transducers.

NOTE: The header should not be insulated over the last 2-3m so as to

ensure that all condensation takes place below the final

connection to the transducers. Fig.12.


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4 DRAIN SYSTEM

4.1 Drain Lines

1 All drain lines shall have as steep a gradient as possible, an all

cases at least 20 mm/m.

2 In erecting these lines, provide sufficient compensation for thermal

expansion. The service temperature in plant can be assumed

to be approximately 450OC.

3 These pipes expand by approximately 6mm/m between the cold

state (initial temperature 20 OC) and the hot state. Determine

from the diagram (Fig.2) the minimum legs required to

accommodate movement.

ATTENTION : Always include a safety margin.

4 On drain lines made from thick-wall piping, ensure straight pipe

sections at least 500 mm long between the drain sockets (on

casings and pipes) and the first bend in the pipe.

5 PRESSURE SENSING LINES, GENERAL

In laying these lines, observe the following:


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1 Lines under pressure must be laid with a constant descending gradient.

2 Lines under vacuum must be laid with a constant ascending gradient.

3 The above lines must have an adequate gradient - at least 1:15 (67

mm/m) - between their connection point and the transducer rack.

4 Lay pressure sensing lines such that the primary cutoff valve forms an

anchor point, which entails laying the line between the connection

point and the primary cutoff (anchor point) with the sufficient flexibility

to accommodate movement of the connection point. A compensating

leg extending 1 meter in each of two planes should be provided in the

lubricating oil, control fluid and drains system on account of the

minimal terminal movement there. (Refer Fig. 10 & 11).

Locking Devices for Threaded Connections.

5 All Fasteners should be locked using tab washers or a suitable thread

lock adhesive.


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6 DESCRIPTION OF THE COORDINATE SYSTEM

1 When isometric are drawn of piping, an indication of the three orthogonal

axes X, Y and Z as in Fig.3 is required.

2 Projections of these axes in the corresponding drgs. shall be as under :

X axis = view toward generator

Y axis = view upward generator

Z axis = view to the right

3 This axis designation shall be positive where no prefix is used.

4 A minus sign prefix shall be used to indicate the opposite direction.


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