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11.01.00 All process connection , piping etc shall be  conform to ANSI/ISA SP 77.70- 1994 (R 2005) “ Fossil Fuel Power Plant Instrument  Piping Installation” , ANSI B 31.1 Power Piping ,ANSI/ASME B 1.20.01 ,ANSI/ASME B 16.5 ,PTC 19.11.1997,PTC 23.2003 & IBR .


11.02.01 Impulse Piping/ Tubing System


         Instrument   impulse   piping,   tubing   fittings   and


         accessories  for  the  connection  of  instruments   and


         control equipment to the process and to make the  system


         complete  shall  be furnished. All  materials  furnished


         shall  meet the requirements of ASTM and ANSI  standards


         for  the  equivalent of these  standards.   The  impulse


         piping, tubing, fittings and accessories shall have  the


         same design pressure and material temp.as applicable for


         the particular main process piping.


11.02.02 For instruments/ devices mounted inside enclosures racks


         also  the  impulse pipes of the same  material  as  main


         process pipe shall be employed except that tubes (as per


         ASTM  A 213)shall be employed for connections  from  tee


         (inside   the  transmitter   enclosures/racks)to   value


         manifolds  and instruments.  The impulse  tube  material


         for  high pressure application shall be 316 H  stainless


         steel and low pressure application 316 L stainless steel.


        11.02.03  All  impulse  pipe shall be of seamless type  and  shall


         conform  to  ANSI B 31.1  for  schedule  Nos .sizes  and


         dimensions etc. 


11.02.04 The valve manifolds shall be  of stainless steel 316 with         pressure rating suitable for intended application.2valve manifold  and 3 valve manifold shall be  used for  pressure measurements using pressure  transmitters/pressure switches and Diff. Pressure transmitters/switches respectively. 5 valve manifold shall be used for remaining applications like DP, flow and level measurements.

11.02.05  Condensate  pots, also referred  to as reservoirs, shall be designed in accordance with ANSI B 31.1.

11.02.06 Fittings and fitting components shall contain no metallic mercury or mercury compounds and shall be free mercury contamination, except as alloying elements of the required base or bonding corrosion resistant plating.

Fittings and fitting components shall not contain low melting-point metals (such as lead, antimony, arsenic, bismuth, cadmium, magnesium, tin or zinc)in concentrations greater than 250 ppm, except as alloying elements of the required base materials. Asbestos shall not used .


  11.02.07 All fittings shall be  forged steel and shall conform to ANSI B 16.11.The material of  forged tube fittings for shaped application (e.g. Tee, elbow etc.)shall be ASTMA 182 Gr.316 H for high pressure/ Temp. applications and  ASTMA 182 Gr.316 L for other applications.  The material for bar stock tube fitting (for straight application) shall be 316 SS.  Metal thickness in the fittings shall be  adequate to provide actual bursting strength equal to or greater than those of the impulse pipe or SS tube, with which they are to be used.

11.02.08 The source shut-off(Primary process root valve) and blow down valve shall be of half inch size globe valve type for all applications except for air & flue gas service wherein no source shut-off valves are to be provided.  The disc and seat ring materials of carbon steel and alloy steel valves be ASTM A-105 and ASTM A-182, Gr.F22, hard faced with stellite (Min. hardness 350 BHN). The surface finish of 16 RMS or greater is required in the area of stem packing.  The valve design shall be such that the seats can be reconditioned and stem and disc may be replaced without removing the valve body from the line.

11.02.09 Blow down valve shall be gradual open type.

11.03.00 Air Supply Piping


      (a)The  bidder  shall include in his scope,  all  pneumatic


         piping,  fittings,  valves air filters,  regulators  and


         other  accessories required for instrument air  for  the


         various pneumatic devices/ instruments from the  Owner’s


         instrument air terminal point to the bidder’s  pneumatic


         devices/ instrument. The instrument air scheme shall  be


         subject to owner’s approval.  The pneumatic piping shall


         be  of heavy duty GI( as per IS 1239).  The quality  and 


         itemized  consumption  of instrument  air  required 


         shall be  indicated  by the bidder.


    (b)  Copper tubing of 1/4″size , thickness of cu tubing shall not be less than 0.065 inch & light  drawn  temper  tubing conforming  to  ASTM  B-75. Copper  tubing  shall be PVC coated  and  tube  fittings shall be  of flare less brass.


11.04.00 Installation and Routing of Instrument Piping and Tubing


         The  primary  impulse piping system  shall  include  the


         instrument  piping  and all  required  accessories  from


         process  tap off up to the respective  instruments.   The


         Contractor  shall  provide the  necessary  fittings  and


         accessories  along with impulse pipes  for  completeness.


         Special accessories such as condensing pots,  reservoirs


         and  other devices etc. shall be provided and  installed


         wherever  required by the design of the  instruments  in


         accordance  with  the  instructions  of  the  instrument


         manufacturer.  In  any  case Bidder  shall  provide  and


         install  condensing pots for all level  measurements  of


         steam  and  water services.  All  flow  measurements  in


         steam services and water services above 120 Deg.C.


         Impulse  piping shall include a blow down line  and  shut


         off  valve  adequate for the duty requirements  and  for


         withstanding  continuous  design  pressure  and  temp.of


         process  medium. For process pressure equal or above  40


         Kg/Sq.Cm.g or temp. above 300 Deg.C double valves  shall


         be  used before connecting to the blow down header.   The


         blow  down  header  shall have to be  connected  to  the


         nearest  plant drain by the bidder and pipes of  ASTM-A-

         105  Gr. B to be provided by bidder on as required  basis

         for this purpose.

11.05.00 All  impulse  piping shall be supported  rigidly  at  an


         interval  not  exceeding  1.5 meters so  as  to  prevent


         excessive  sag  in piping. Process piping shall  not  be


         used for supporting impulse piping.


         Impulse  piping  shall be installed  to  permit  thermal


         expansion without placing excessive stress on the piping


         and  without  affecting  the  gradient  of  slope.  Long


         continuous  straight  runs  of piping  shall  always  to


         avoided. If required, expansion loops shall be  provided


         atleast every 2.5 meters to break the continuity.


         Cold  bending of impulse pipes shall be  performed  with


         the  use  of a proper pipe bender with  radius  of  bend


         greater than 5 times the outside dia of the pipe.  Bends


         shall  be  true to angle and radius and  shall  be  true


         circular cross section of the pipe without buckling. Any


         pipes  damaged  during  bending  operation  shall not be 




11.06.00 All welded and acre wed fitting shall conform to  ANSI-B-


         16.11.  Threads of piping components shall be taper pipe


         thread in accordance with ANSI-B-2.1.  All threads shall


         be  clean machine cut with all burrs and chips  removed.


         Lubricant shall be of dry file type.            


11.07.00 Provision for continuous purging requirement is to be made  for all air & flue gas applications.

11.08.00 Testing at site


a)    Hydrostatic and pneumatic tests shall be performed on

all pipes, tubes, systems and shall confirm to ANSI-B 31.1 and ANSI/ISA SP 77.70- 1994 (R 2005).

All instrument piping/ tubing shall be hydrostatically  

tested upon completion of erection.  The test pressure

shall be 1.5 times the maximum process pressure.

b) Air header & branch pipes shall be air tested by pressure

         Decay method as per ANSI – B 31.1 after completion of     


11.09.00 Material  Certification


11.09.01 Material  of  Construction


        All material used in construction of piping and components  

        shall be certified by the manufacturer with a  certificate of compliance to the ASTM/ASME specifications.  The manufacturer

       shall submit quality assurance program for material control and verification.


11.09.02 Certificates  of  Compliance


       All  certificates of compliance applicable to material used in a component should be furnished by the manufacturer with the  material at the time of shipment.


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