Energy Efficiency Reference/Boilers/SteamMaster Users Guide

Introduction

SteamMaster is a software tool based on an Excel spreadsheet with a Visual Basic interface to simplify steam system characterization. SteamMaster has the following features and capabilities:

Features

System Features:

• Software accepts multiple boilers
• Four firing rates (and efficiencies) for each boiler
• Matches boiler furl use for multiple boilers and firing rates
• Visual Basic Interface
• Online Help
• Custom Menus

Combustion Efficiency:

• ASME indirect method of calculating combustion efficiency
• Fuel properties lookup table that includes gas, oil, coal, and wood

Boiler Efficiency:

• Part load efficiencies
• Radiation and convection losses that are important at part loads
• Cycling losses are also important at low loads

System Losses:

• Uninsulated Steam Piping
• Steam Leaks
• Trap Leaks
• Flash Steam

Databases:

• Boiler manufacturer specification database
• Steam trap manufacturer specification database

Calculates Savings from Five Steam Recommendations:

• Tune Boilers
• Insulate Steam Pipes
• Repair Steam Leaks
• Repair Trap Leaks
• Recover Flash Steam

Using SteamMaster SteamMaster was created using Microsoft Excel 2002. Protection was enabled to prevent accidental overwriting of calculated cells, although there is no password required. Excel 2002 allows protected cells to be selected, formatted, and pivot tables to be used. Other versions may not allow these functions. Therefore you may need to unprotect sheets to use SteamMaster.

Open SteamMaster A dialog box will tell you that SteamMaster contains macros. Enable them. SteamMaster may also ask if you want to open as ready-only. Select no to allow editing and data entry.

Calculations Many steam properties are calculated using equations (curvefits) that match values from steam tables or properties books. The equations are not reproduced in the guide because they are visible in the spreadsheet cells.

SteamMaster Custom Menu When you open SteamMaster, a custon "SteamMaster" menu is added to Excel. SteamMaster is fully functional as a spreadsheet, without the need to use any of the automated features in the SteamMaster Menu. However, the custon menu can facilitate the following functions:

Add Boiler You can add a boiler manufacturer and model to the analysis from the database. A new worksheet tab is created and the boiler is added to the summary page. If the current model is not currently in the database, you can add one.

Add boiler to Database You can add a boiler to the database by entering manufacturer, model and specifications.

Add Trap Manufacturer You can add a steam trap to the database by completing manufacturer, model and specification fields. If the manufacturer is not in the pull-down menu, enter the new manufacturer.

Boilers The Boiler Navigator will take you to specific Boiler tabs.

Summary The Navigator will take you to the Summary Sheet.

Delete Boiler Sheets You can add or delete boilers from the current project. For example, if you have two boilers, and SteamMaster was saved with four boilers, you can delete boiler sheets. This operation will also delete a boiler from the Summary Sheet. SteamMaster will ask if you want to delete each sheet one at a time. If you want to keep boilers 1 and 2, run "Delete Boiler Sheets" and respond "no" to the dialog box, "Do you want to delete boiler number 2?" Repeat "no" until you reach the last boiler that you want to delete, and respond "yes."

Calculate Savings Summary Normally, SteamMaster recalculates changes automatically. If however, you reset calculation to manual, this function will recalculate the results.

Help This manual is available in online help format, indexed by worksheet tabs.

Summary Sheet

The Summary Sheet allows you to enter information that is common to all boilers in the steam system and operating conditions for each boiler. It allows you to match boiler fuel use to fuel bills, and summarizes results from five potential system improvements. Data entry cells have a blue font. Other cells have labels and formulas that are protected. There is no password, but they are protected so you cannot inadvertently overwrite a formula.

Operating Conditions

Company ID Identify the company in an appropriate manner.

Annual Operating Time (hours) Enter the number of hours per year that any boiler operates. Individual boiler operation is specified later for each firing rate. The time that the system is hot is used to calculate losses from uninsulated pipes, and steam and trap leaks.

Elevation (feet) Elevation in feet above sea level is used to calculate the atmospheric pressure, and therefore air density and steam properties at the boiler location.

Condensate Return(%) Enter percentage of steam condensate that is returned to the boiler. Steam flow can be estimated from boiler firing rate (input Btu/hr) x boiler efficiency [default = 80%]/steam enthalpy [default = 1000 Btu/lb]. Look for a makeup water meter reading in a log or a chemical treatment company report.

Steam System Volume (ft3) Steam Volume is used to calculate boiler cycling times (boiler shuts down) when system load is less than the minimum-firing rate. Many boiler manufacturers specify the "steam chest" or "steam volume" as the volume above the water level in a boiler. A curve fit for scotch marine boilers produced a default value [default = 0.2 ft3/hp]. System volume also includes piping. The Pipe Loss tab includes columns for surface area and volume for piping that you enter in the table.

Air Humidity Ratio (lbv/lb dry air) The absolute humidity, specific humidity, or humidity ratio is the ratio of the mass of water vapor in a volume of air to the mass of dry air. It is used to calculate the boiler efficiency loss due to heating water vapor in combustion air. Absolute humidity can also be found from relative humidity and other air properties in psychometric charts.

Temperatures

Operating Steam Temperature (F) The saturated temperature (F) is calculated for the existing system Operating Pressure.

Proposed Steam Temperature (F) The saturated steam temperature (F) is calculated for the Proposed system operating Pressure in the case you recommend reducing system pressure.

Condensate Temperature (F) The condensate temperature is calculated from the condensate return system pressure. For example, an atmospheric condensate system would have a condensate temperature of 212 F. Condensate temperature is used to calculate flash steam losses. Condensate loses heat in the process of returning to the boiler, and might arrive at 160-180 F. However, we base the flash steam calculation on the saturation temperature at the steam trap.

Inlet Air Temperature (F) Combustion air is heated from inlet conditions to boiler stack conditions. Inlet air properties and used in combustion efficiency calculations. [default = 80 F]

Inlet Water Temperature (F) Water is heated from inlet temperature to saturated steam at the system pressure. Well water and city water temperature both vary with location and season. [default = 50 F]

Pressures

Operating Pressure (psig) System pressure varies with load and control range set points. Enter average operating pressure for existing system.

Proposed Pressure (psig) Enter a higher or lower pressure if you recommend changing the pressure. Efficiency and losses are calculated using the proposed pressure and presented in the "proposed" columns.

Condensate return pressure (psig) Condensate is usually reduced to atmospheric pressure (0 psig) at the steam trap and collected in a condensate tank. The condensate is then pumped back to the boiler room, usually to a feedwater tank. When saturated liquid is reduced in pressure, it becomes superheated. Some of the liquid flashes to vapor until the liquid temperature reaches the saturation temperature at the lower pressure. For example, when condensate at 100 psig is reduced to 0 psig. 13% of the condensate flashes to steam, which represents a significant system loss. A pressurized return will supply low-pressure steam that can be used for other purposes, including heating makeup water. Enter existing condensate return pressure. [default = 0 psig]

Atmospheric pressure (psia) Atmospheric pressure (0 psig) is calculated in terms of absolute pressure (psia), compared with a perfect vacuum base on elevation and above sea level. For example, atmospheric pressure at sea level is 14.7 psia. Enter elevation and observe the calculated pressure, which is used in the calculations.

Pressure range (psi) System pressure is maintained in a pressure range by the system controls, provided there is adequate boiler capacity to meet the load. When the boiler operates at pressure falls until the boiler restarts. Enter this control pressure range, which is used to calculate how long the boiler runs to raise the pressure this amount, and how long it stays off. Pressure range is used in the cycle loss calculations.

Fuel

Fuel Type Choose the fuel type from a pull-down menu of six fuels (coal, No. 2 fuel oil, No. 6 fuel oil, natural gas, propane, and wood). Fuel properties affect efficiency calculations and are considered in more detail in the Fuel Sheet.

Fuel Cost ($/MMBtu) Enter fuel cost dollars/ million Btu.

Boiler Summaries

The boiler summary tables allow you to enter firing rates and operating hours for each boiler and to match total fuel use for all boilers to fuel bills. It then summarizes existing and proposed efficiencies and energy use and savings for each firing rate, total for each boiler, and total for system.

Firing Rate Enter up to four firing rates, expressed as a percentage of full fire, for each boiler and hours that each boiler operates at each rate.

Annual Hours Enter hours that each boiler operates at each firing rate. Note that total operating hours for each boiler at all firing rates is calculated at the bottom of each table.

Efficiencies Calculations of efficiencies for existing and proposed conditions are calculated in each boiler sheet and summarized.

Cost Savings The difference between existing and proposed conditions yields energy and cost savings, at the fuel cost you entered.

Boiler Annual Energy Use (MMBtu/yr) Annual energy use for existing and proposed conditions is totaled for each boiler individually and for the system in the Savings Summary table at the bottom.

Savings Summary

Recommendations Savings for five potential system improvements are summarized. Not all opportunities apply to all systems, and there are other opportunities that are not included. The five recommendation are:

 - Tune Boilers
 - Insulate Steam Pipes
 - Repair Steam Leaks
 - Repair Trap Leaks
 - Recover Flash Steam

Tune Boilers Existing and proposed boiler efficiencies are calculated using the AMSE Indirect Method in the individual boiler sheets. Energy and cost savings for steam system are included in the summary table.

Insulated Steam Pipes Results from insulating uninsulated steam pipes are summarized from the Pipe Loss sheet. The efficiencies are losses expressed as a percentage of use. The proposed conditions assume that most of the pipe heat loss will be recovered with insulation. Enter the proposed heat loss as a percentage of uninsulated heat loss for the insulation you select in the Pipe Heat Loss Factors table on the Pipe Loss sheet. [default = 10%]. We divide heat loss savings by system boiler efficiency to calculate energy and cost savings.

Repair Steam Leaks Heat losses for steam leaks are calculated on the Steam Leaks tab and summarized here. Enter the proposed steam leaks as a percentage of existing steam leaks. [default = 10%]. We divide heat loss savings by system boiler efficiency to calculate energy and cost savings.

Repair Trap Leaks Heat losses for steam traps are calculated on the Trap Leaks tab and summarized here. Enter the proposed trap leaks as a percentage of existing trap leaks. [default = 10%]. We divide heat loss savings by system boiler efficiency to calculate energy and cost savings.

Recover Flash Steam Condensate is usually reduced to atmospheric pressure(0 psig) at the steam trap and collected in a condensate tank. The condensate is the pumped back to the boiler room, usually to a feedwater tank. When saturated liquid is reduced in pressure, it becomes superheated. Some of the liquid flashes to vapor until the liquid temperature reaches the saturation temperature at the lower pressure. For example, when condensate at 100 psig is reduced to 0 psig, 13% of the condensate flashes to steam. Because the latent heat of vaporization at atmospheric pressure is 970 Btu/lb this represents a significant system loss. The existing efficiency and energy column presents this heat loss for the system and condensate system pressure, divided by system boiler efficiency.

A pressurized condensate return system will allow you to recover some or all of the flash steam. Low-pressure steam can be used for other purposes, including heating makeup water, using existing condensate return (%). The savings column show the calculation for the amount of flash steam that could be used to heat makeup water directly in the makeup water or deaerator tank without adding additional heat exchangers. The proposed column shows the remaining quantity of flash steam that is available. If you identify a use and a system to apply it, then reduce the proposed steam use, and the savings will increase proportionately. Note that both the flash steam quantity and use for makeup water vary with condensate system pressure and condensate return percentage.

Total System efficiencies are boiler efficiencies, including radiation, convection and cycling losses, minus the four identified system losses: uninsulated pipes, steam leaks, trap leaks, and flash steam. Total existing and proposed system energy use is less meaningful because boiler use (shown on the tune boiler recommendation row) includes system losses. However, the total energy and cost savings for the five recommendations is the result of system improvements.

Boiler Sheets

Enter information in the cells where font is in blue. For each individual boiler sheet, enter information that is specific to the corresponding boiler.

Boiler Nameplate

Manufacturer There is a database of boiler manufacturers, models and specifications on the Boiler Mfgrs sheet. you may add a boiler from the database or add a new boiler to the database.

Model Enter the model from the nameplate.

HorsePower Boiler horsepower is different than electrical or mechanical horsepower. If boiler horsepower is not on the nameplate, you might find one of the following conversions helpful:

 - 1 boHP = 33,500 Btu/hr
 - 1 boHP = 34.5 lb/hr of steam
 - 1 boHP = 5 ft^2 of heat transfer surface (rule of thumb)

Maximum Firing Rate Enter in MMBTU/hr for all fuels. This is input rate, and therefore should be around 40,000 Btu/hr-BoHP.

Boiler Type Choose the boiler type from a pull-down menu among five types:

 - Cast Iron Sectional
 - Fire Tube
 - Hot Water
 - Scotch Marine
 - Water Tube

Minimum Firing Rate The lowest rate at which the boiler can operate is usually between 10 and 40%, the smaller rate for larger boilers. Turndown is the ratio of maximum to minimum fire. Minimum fire affects boiler cycling losses at loads below minimum fire.

Control Type Choose the control type from a pull-down menu among three types:

 - Full Modulating
 - Low-High-Low
 - On-Off

Cycling Losses

When a boiler cycles off and on, air is blown through the combustion chamber to remove unburned fuel before ignition for safety reasons. Purge cycles carry energy from the system and constitute a loss, the magnitude of which depends on cycle times. The following is a combination empirical and calculated approach to estimating cycle losses.

Purge air temperature During the purge cycle air is blown through the boiler. In theory the exit temperature can be calculated; in practice it is a complicated calculation. Based on several measurements, we use the exit air temperature as percentage of saturated steam temperature, both relative to inlet air temperature, in our heat loss calculations. [default = 75%]

Purge Cycle Time This value is the time during which air is blown through the boiler without fuel for the purge cycle. Enter the average time in seconds for both pre (before burner) and post-purges. The program assumes both purges are the same and multiplies by 2 to account for both pre and post purges. [default = 30 seconds]

Standby Cycle Time It is the time for a complete boiler cycle when the standby load is less than the boiler minimum firing rate. The approach is the calculate the amount of time that the boiler will require to raise the pressure in the system volume by the controls pressure range amount. It further considers the ratio of the boilers load to the minimum firing rate to calculate how long the boiler can stay off. The cycle time includes pre and post purges, burner operation, and the time boiler is off. Cycle time is used to calculate the cycling losses when the boiler is on standby firing rate.

Stacking Conditions

o2 (%) Most combustion analyzers or stack gs sensor measure the volumetric percentage of oxygen in the stack gas. Enter the measured value.

CO2 (%) SteamMaster calculates Carbon dioxide concentration on a volumetric basis. Some test equipment measures CO2 instead. If your does, you will have to lookup the corresponding O2 concentration to use SteamMaster.

CO (ppm) Carbon monoxide concentration is quantifiable measure of unburned fuel. Most combustion analyzers measure CO in parts per million (ppm). Levels over 400 ppm are considered dangerous for people. Many combustion analyzers do not measure levels above 400 ppm. Note that this level (0.04%) has a negligible effect on combustion efficiency, but may be an indicator of burner or other boiler problems. SteamMaster calculates the effects of CO, which can be significant at dangerously high concentrations. If you encounter stack concentrations of CO over 400 ppm, advise plant management to have the boiler maintained immediately.

Stack Temperature (F) The temperature of stack gases is used to calculate the amount of heat leavings the boiler.

Net Stack Temperature (F) Stack minus Inlet Air Temperatures is used to calculate the amount of heat the boiler adds to the fuel and combustion air mixture.

Efficiency

Combustion efficiency is calculated using the ASME indirect method (see COMBUSTION EFFICIENCY DEFINITIONS section) in which the following losses are calculated and subtracted from 100%. The method and formulas are documented in the ASME standards.

Dry Gas Lossesrepresent sensible heat leaving the boiler stack.

Moisture Formation is the loss calculated from burning hydrogen in the fuel.

Moisture in Fuel (wet basis) is the loss required to evaporate and heat moisture contained in the fuel. Most fossil fuels contains little or no moisture. Wood fuel often has a significant moisture content.

Carbon Monoxide are losses from the energy of formation of CO that have not been fully released in the combustion process.

Losses due to ash Wood generally contains ash, which does not combust. Therefore, ash concentration (generally small) is subtract from the heating value of the fuel.

Moisture in the air is another source of water that removes heat from the system.

Combustion Efficiency Subtract the previous losses from 100% to calculate combustion efficiency.

Radiation/Convection Losses Hot boilers lose heat to their surrounding by radiation and convection. SteamMaster uses a curvefit of a graph found in the ASME Steam Unit Generation standard. ?????