Boiler Codes For Power Applications

Codes for Power Applications What Standards Apply? B16.34 API 6A &D

B16.34 Annex A

B16.34 Annex A

V1-1

Full Port Valves ANSI Pressure Class

Reduced Port Valves ANSI Pressure Class

Pipe to Port Effect There is a considerable impact on Flow, when port sizes do not match Pipe ID With the usage of P91 pipe, pipe ID’s have increased, which has reduced the valve Cv The following slide gives an example of Cv for a 2” P91 pipe, with port sizes of 2.125, 1.5 and 1.3

Pipe to Port Effect 2 1/2” P91 pipe, with a 2.125 pipe ID Port Size 2.125 1.5 1.3

Cv 348 140 63

ASME TDP 1 Recommended Practices for the prevention of water damage to steam turbines used for electric power generation. 3.3.3 Minimum pipe and valve ID 1” for all drain valves and valve ports just upstream of the Turbine intercept valve.

ASME TDP 1 3.3.5 Before seat drains should have a minimum port and pipe ID of ¾”. 3.3.6 Drains after the Mainsteam stop valve should have a minimum port and pipe ID of ¾”. 3.4.3 Cold Reheat drain pots. Should have a minimum pipe ID and Port size of 2”

ASME TDP 1 3.6.5 Hot Reheat drain lines should have a minimum ID of 1-1/2” with a full ported drain valve. 3.11.7 Drains Systems The minimum pipe ID and valve porting should be ¾”

ASME Code Section I • Double Valves are a code requirement for Blow Off Valves, or drain applications that are used as both drains and blow offs.

1ASME B&PV Code Sect. 1 PG Blow Off Valves ASME B&PV Code Sect. 1 PG 59.1.1.4 Blowoff Piping not exposed to combustion must have bolted flanged joints (if exposed must have tapped joints). PG-PG 59.3.5 Blowoff connections shall be between NPS 1 - 2 1/2 (except for boiler's with less than 100 sq.ft. heating surface which may have connections of NPS 3/4).

ASME B31.1 PG 122.1.4 (A) Two shuff off valves are required. PG 122.1.4 (A1) Design Pressure shall be 125% of maximum allowable working pressure or shall exceed max. working pressure by 225 psi whichever is less but shall not be below 100 psig.

ASME B31.1 PG 122.1.4 (A2) The allowable stress value of the piping material shall not exceed that permitted for the temperature of saturated at the maximum allowable working pressure of the boiler. PG 122.1.4 (A3)All pipe shall be steel and greater than Schedule 80. PG 122.1.4 (A4)Blowoff piping shall not be less than that of boiler connection

ASME B31.1 PG 122.1.7 (C1) Valves can not have dams or pockets where sediment can collect. PG 122.1.7 (C4)Each bottom blowoff pipe shall have two slow-opening valves, or one fast opening valve followed by a slow opening valve. PG 122.1.7 (C5)When design pressure doesn't exceed 250 psig valve may be of bronze, cast iron, ductile iron or steel.

ASME B31.1 PG 122.1.7 (C6)When design pressure exceeds 250 psig valve must be steel and be manufactured to ASME/ANSI Class 300 or greater.Minimum pressure rating shall be equal to the design pressure. PG 122.1.7 (C8)A slow-opening valve is defined as one needing five 360 degree turns to open. PG 122.1.7 (C9)A boiler with multiple blowoff pipes needs only one single master pipe. PG 122.1.7 (C10)The two independent valves may be combined in one valve body.