Reference Data

Often when dealing with boiler room equipment the "how much" and "how often" questions arise as to size, capacity, flow rates, etc. While acknowledging there are specific formulas and methods for arriving at the answer, most often a portion of real time information necessary for the formula to make it specific is not readily available. Given that, a good assumption must often be made to move forward. The following basic "Rule of Thumb" formulas and data may be influenced by things like specific gravity, altitude, pressure, actual constituents, operational efficiency and so on, but are suitable for use in day to day estimates. All information is general in nature and subject to exception based on specific application conditions. Specific application criteria should be discussed with W. C. Rouse & Son. This information is organized as follows:

1. COMMON CONVERSION FORMULAS

2. TYPICAL FUEL VALUES

3. BASIC HEATING FORMULA FOR WATER

4. BOILER SYSTEM CONSIDERATIONS
   A)  Boiler Operating Pressure:
   B)  Boiler Design Pressure:
   C)  Emissions & Permitting:
   D)  Piping & Valve Considerations:

5. THERMAL SHOCK

6. FUEL CONSIDERATIONS

7. REFRACTORY or WATER (it's someone's money)

8. FEEDWATER TREATMENT (mechanical & chemical)

9. EFFICIENCY

10. SATURATED STEAM TABLE

1) COMMON CONVERSIONS:
The following assumes a nominal boiler efficiency of 80%, and capacity from and at 212.F for steam boilers as cataloged in most boiler manufacturer's data and performance sheets:

2) TYPICAL VALUES FUEL VALUES:
1 GAL No.2 Fuel Oil = 140,000 BTU/GAL
1 GAL No.5/6 Fuel Oil = 150,000 BTU/GAL
1 CU/FT of Natural Gas @ 60.F = 1000 BTU/CU/FT (typical @ .60 SG)
1 GAL of LPG (propane) @ 60.F = 91,600 BTU/GAL
1 CU/FT of LPG vapor (propane - raw) @ 60.F = 2500 BTU/CU/FT (typical @ 1.53 SG)

3) BASIC HEATING FORMULA FOR WATER:
GPM / 2 x DELTA-T = LB/STM/HR
(Example: 34.5 GPM / 2 x 140.F rise = 2,415 LB/STM/HR req'd)
or
GPM x 500 x DELTA-T = BOILER BTU/HR OUTPUT (Example: 34.5 GPM x .500 x 140.F rise = 2,415 MBH gross boiler output req'd)

4) BOILER SYSTEM CONSIDERATIONS:
A) Boiler Operating Pressure: A boiler will not operate at its "design pressure." The pressure vessel is protected by safety valves designed to open at or near the vessel design pressure. Due to simple mechanical limitations, these valves will begin to open (or weep) at or near the set point. Increases in valve accuracy are available at a larger expense, permitting closer tolerance. But still, if the safety valves are applied per the ASME code, they will still attempt to open at, or as they near the vessel design pressure.

B) Boiler Design Pressure: Often referred to as the boiler "working pressure" - in North America, boilers are constructed in accordance with the ASME code. Low Pressure Steam Boilers to 15 PSIG WSP (Working Steam Pressure) and Hot Water Boilers up to 160 PSIG WWP (Water Working Pressure) with up to 250.F (max) operating temperature, are governed by the construction requirements of the ASME Code Sect.4. High Pressure Steam Boilers (16 PSIG and over) are covered by the ASME Code Sect.1, and typically have design pressures (or working pressures) of 125 PSIG, 150 PSIG, 250 PSIG, and higher. Hot Water Boilers above the 160 PSIG / 250.F limitation are governed by this section also, and are referred to as Medium Temperature, or High Temperature Hot Water Boilers. As you might expect, high pressure boilers constructed to the ASME Sect.1 code are more expensive than the low pressure boilers constructed to the ASME Sect.4 code.

C) Emissions & Permitting: The EPA advises that the products typically requested by a solicitation for a boiler or burner may be subject to Subpart Dc of NSPS, and that any facility subject to Subpart Dc is required to comply with 40 C.F.R Part 60, Subpart A, the General Provisions of NSPS. W. C. Rouse & Son, and the boiler and burner manufacturers represented by W. C. Rouse & Son, provide proposals for components, and/or equipment designed for this compliance only if performance criteria is specifically outlined in the solicitation for this equipment and the proposal provided specifically addresses that criteria. Interpretation of compliance requirements must be handled at the local EPA level by the purchaser.

What does that mean? It means, that in the United States you have to have an air emissions permit, typically designated as a "Permit for Construction" prior to installing a combustion source of any kind. In some areas this is interpreted as simply issuing an order for the equipment. This does makes sense, as how can the equipment be provided with an emission control device or method, if the level of emissions has not been established prior to order entry?

Allowable source emissions performance is established by the state or local EPA group, utilizing the Federal Regulations, regional air quality conditions, growth considerations and coordination with adjacent EPA jurisdictions. The requirements for each area will vary as to the size and type of the source equipment, and according to localized modeling done by that group. It is not prudent to assume that existing fuel(s), an existing permit, or a manufacturer's typical cataloged emissions reduction equipment is suitable for an application without first submitting for, and obtaining a "Permit for Construction." The responsibility for this permit falls to the Owner, or the Owner's "designated representative." This permitting procedure must be a part of the initial project design process, and typically requires the involvement of a properly licensed and registered Consulting Engineer within the state the equipment is to be installed. Some areas require a waiting period with advertisement for public comment. Failure to address this permit may induce project delay, undue equipment modification cost, and possibly fines.

Assuming the emission requirements, or automatically providing equipment advertised with the lowest possible emissions performance, without an actual "Permit for Construction," is not a good practice. This method (or guess) may incur undue capital costs and elevate maintenance costs unnecessarily over the life of the equipment. As emissions requirements will certainly change as time passes, it is suggested that the boiler/burner method of construction be modular in nature, to lend itself to future modification and retrofit. Systems with fixed integrated methods of emission reduction may require substantial or perhaps wholesale burner or boiler change out to address future requirements. Please keep in mind that "Permits for Construction" are typically issued based on aggregate tons of pollutants emitted per year, not necessarily the immediate PPM performance of the source on a particular fuel. Given that, a system burning primarily natural gas, with No.2 fuel oil as a standby (used perhaps 2 weeks per year) may comply with the total emissions allowed per year with just good emissions performance on natural gas. This gas fuel performance may offset the higher emissions experienced when burning the oil fuel. No extra emissions controls may be necessary. As such, initial application for a "Permit for Construction" should reflect standard source emissions without additional emissions control, allowing the local EPA to advise what may actually be required for the specific application.

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