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Section I Safety Sizing & Selection

23 and 24 January 2007 Boiler Set Sizing

RHO

SHO Drum

RHI Total Relieving Capacity of all Code must be equal to or greater than the maximum continuous rating of the boiler(Drum & SHO) or reheater (RHO & RHI).

23 and 24 January 2007 Boiler Set Sizing

Drum

Steam Drum Valves must relieve a minimum of 75% of boiler capacity.

23 and 24 January 2007 Basic Section I Sizing Rules

Basic Section I Sizing Rules - LdlLow set drum valve set at didesign pressure - Other valves shall have staggered settings - Not permitted to rise more than 6% above MAWP, taking into account 3% accumulation

All valves open/full flowing 106%

Low Set Drum Valve open/full flowing (High Set Drum Valve set pressure) 103%

Design Pressure (MAWP) ((pLow Set Drum Valve set pressure)100%

23 and 24 January 2007 Sizing

• Basic Section I Sizing Rules • outlet safety valve must be set to insure opening prior to drum safeties

RHO SHO

23 and 24 January 2007 Data Needed to Properly Select Boiler Safety VlValve Set • Total Boiler Capacity • Maximum Allowable Working Pressure (MAWP) • Drum Operating pressure • Superheater Operating Pressure • Superheater Operating Temperature

•Cappyacity •MAWP • Inlet Operating Pressure • IltTInlet Temperat ure • Outlet Operating Pressure •Outlet Oppgperating Temperature

23 and 24 January 2007 Sizing

• To determine SHO Safety Valve Set Pressure, the pressure drop through the superheater must be considered: • To determine the pressure drop: • DOtiPDrum Operating Pressure • Less SHO operating pressure

= Superheater Pressure Drop

23 and 24 January 2007 Sizing

• Superheater SV Set Pressure is then determined by: • Design Pressure • Less SHO pressure drop • Less 20 PSIG safety factor *

=

Superheater Set Pressure

23 and 24 January 2007 Application: Recommended Valve Selection

15-600 601-2000 2001-3000 System (psig) (psig) (psig)

DRUM HSJ/HL HCI HE

SUPERHEAT OUTLET HSJ/HL HCI HCI

REHEATER OUTLET HSJ/HL HCI HCI

REHEATER INLET HSJ/HL HCI HCI

23 and 24 January 2007 Boiler Specifications

Total steam generation: 813,036 lbs/hr Design Pressure: 2190 psig Drum Operating Pressure: 2018 psig SHO Operating Pressure: 1948 psig SHO Design Temp: 1064°F SHO Operating Temp: 1054°F

23 and 24 January 2007 ASME Code Requirements

• Drum valves must relieve a minimum of 75% of total required relieving capacity. • Two drum valves typically required.

23 and 24 January 2007 Drum Safety Valves Capacity

• To determine minimum flow through all drum valves: 813,036 lbs/hr x .75 = 609,777 lbs/hr

• Approximate flow through each valve: 609,777Ü 2 = 304,888.5 lbs/hr (per valve)

23 and 24 January 2007 Drum Safety Valves Set Pressures

• To determine drum valve set pressures: • Low set valve = 2190 psig (design pressure) • High set valve = 2254 psig (design pressure x 1.03)

23 and 24 January 2007 Valve Capacity

• Saturated steam capacities (Catalog CROMC-0295): Smallest valve to flow approximately 304,888 lbs/hr – K2 orifice • Low set drum K2 orifice- 2190 ppg@sig @ sat steam 274,145 lbs/hr • High set drum M orifice- 2254 psig @ sat steam 401,428 lbs/hr

• Total through both valves: 675,573 lbs/hr

23 and 24 January 2007 SHO Valve Capacity

• The balance of the total required capacity must pass through the superheater outlet safety valve (typically between 15% - 25% of total capacity).

23 and 24 January 2007 SHO Valve Capacity

• Minimum SH Outlet Valve flow for this example: Total required capacity: 813,036 lbs/hr Less total drum valve capacity: 675,573 lbs/hr Mini mum SH capacit y: 137,463 lb s /hr

23 and 24 January 2007 SHO Valve Set Pressure

• To determine Superheater Outlet Valve Set Pressure, the pressure dthhthhtdrop through the superheater must tbidd be considered:

To determine the pppressure drop: Drum operating pressure: 2018 psig Less SH outlet operating pressure: - 1948 psig

Superheater pressure drop: 70 psig

23 and 24 January 2007 SHO Valve Set Pressure

• Set Pressure is then determined by: DiDesign pressure: 2190 ps ig Less SH outlet pressure drop: - 70 psig Less safety factor* : - 20 psig

SHO valve set pressure: 2100 psig

* Saf ety facto r pr ovi ded by Cr osby En gin eerin g to en sur e SHO safety valve opens first.

23 and 24 January 2007 Valve Capacity

• Saturated Steam Capacities (Catalog CROMC-0295): Smallest valve to flow a minimum of 137,463 lbs/hr – K2 orifice SHO Safety Valve - 2100 psig @ 1054°F*: 192,014 lbs/hr

* At set pressure, SHO operating temperature is above sat steam temperature, therefore K2 saturated capacity is multiplied by correction factor (Ksh) is 0.736.

23 and 24 January 2007 Boiler Set Safety Valve selection

Set % of Valve Valve Pressure Temp Capacity Total Location Size Model (PSIG) (F) (Lbs/Hr) Capacity Low Set Drum 2-1/2 K2 6 HE-86 2190 Sat. 274,145 Safety Valve PSIG Steam Lbs/Hr High Set Drum 3 M 6 HE-86 2254 Sat. 401,428 Safety Valve PSIG Steam Lbs/Hr Total Flow thru 675,573 83.1% Drum SV’s Lbs/Hr SHO Outlet 2-1/2 K2 6 HCI-99 2100 1054F 192,014 23.6% Safety Valve PSIG Lbs/Hr Total Flow thru 867,587 106.7% of all SV’s Lbs/Hr MCR

23 and 24 January 2007 Safety Valve Sizing & Selection

• Boiler Set Sizing Program • Available September 2007 • Datasheets / Calculation Sheets • Marketing-linked catalog pdf ’s • Reaction Forces • Noise Calculations

23 and 24 January 2007