BOILER EFFICIENCY

FACTS YOU SHOULD KNOW ABOUT FIRETUBE BOILERS AND BOILER EFFICIENCY

Today’s process and heating applications continue to be powered by steam and hot water. The mainstay technology for generating heating or process energy is the packaged firetube boiler. The packaged firetube boiler has proven to be highly efficient and cost effective in generating energy for process and heating applications.

Conducting a thorough evaluation of boiler equipment requires review of boiler type, feature and benefit comparison, maintenance requirements and fuel usage requirements. Of these evaluation criteria, a key factor is fuel usage or boiler efficiency.

Boiler efficiency, in the simplest terms, represents the difference between the energy input and energy output. A typical boiler will consume many times the initial capital expense in fuel usage annually. Consequently, a difference of just a few percentage points in boiler efficiency between units can translate into substantial savings. The efficiency data used for comparison between boilers must be based on proven performance to produce an accurate comparison of fuel usage. However, over the years, efficiency has been represented in confusing terms or in ways where the efficiency value did not accurately represent proven fuel usage values. Sometimes the representation of “boiler efficiency” does not truly represent the comparison of energy input and energy output of the equipment.

Remember, the initial cost of a boiler is the lowest portion of your boiler investment. Fuel costs and maintenance costs represent the largest portion of your boiler equipment investment. Not all boilers are created equal. Some basic design differences can reveal variations in expected efficiency performance levels. Evaluating these design differences can provide insight into what efficiency value and resulting operating costs you can expect.

However, every boiler operates under the same fundamental thermodynamic principles. Therefore, a maximum theoretical efficiency can be calculated for a given boiler design. The maximum value represents the highest available efficiency of the unit. If you are evaluating a boiler where the stated efficiencies are higher than the theoretical efficiency value, watch out! The efficiency value you are utilizing may not truly represent the fuel usage of the unit.

In the end efficiency comes down to value. The value of the boiler. The value of the burner. The value of the support provided throughout the life of the equipment.

Why choose the most efficient boiler?

When you buy a boiler, you really are putting a down payment on the purchase of steam or hot water. The payments to generate the power are ongoing over the life of the equipment and are driven by fuel to steam efficiency and maintenance costs. Even with economical fuel costs, the selection of a high efficiency boiler will result in substantial cost savings. A boiler installation costing $75,000 can easily consume over $400,000 in fuel every year it operates. Selection of a boiler with “designed-in” low maintenance costs and high efficiency can really provide savings and maximize your boiler investment.

Efficiency is only useful if it is repeatable and sustainable over the life of the equipment. Choosing the most efficient boiler is more than just choosing the vendor who is willing to meet a given efficiency value. The burner technology must be proven to be capable of holding the air/fuel ratio year in and year out. Make sure the burner design includes reliable and repeatable features. How do you tell? Ask any boiler technician who has worked on a variety of boiler/burner designs. Burners with high pressure drop design, quality fan and damper design, and simple linkage assemblies are easy to tune and accurately hold the air to fuel ratios. Burners with blade or louver damper designs and complex linkage assemblies tend to be harder to

set-up over the firing range of the boiler and tend not to accurately hold the air to fuel ratio as the boiler operates. 

Why choose the most efficient boiler? Because the dividends paid back each year far outweigh any initial cost savings of a less efficient design. What is the most efficient boiler? One that not only starts up efficiently but continues to operate efficiently year in and year out.

Replace or Repair.

The decision to purchase a new boiler is typically driven by the needed replacement of an old boiler, an expansion of an existing boiler room, or construction of a new boiler room facility.

When considering the replacement of an old boiler, review the following points to make sure you are performing a comprehensive evaluation of your situation.

1. Maintenance Costs

Review your maintenance costs carefully. The old unit is costing you money in various ways, including emergency maintenance, downtime, major maintenance requirements (past and pending), difficult–to–find and expensive parts requirements, operator time in keeping the unit on-line, and overall vessel, burner, and refractory problems. Many of these costs can be hidden within your overall maintenance budget. You are paying the price for having outdated boiler room equipment. But the costs need to be investigated and totaled.

2. Boiler performance

New packaged firetube boilers have much higher performance standards than older design units. Turndown, excess air, automatic operation, accurate-repeatable air/fuel ratio burner designs, computer linked combustion controls, low emission technology, and high guaranteed efficiency all are now available on premium designed packaged firetube boilers. The result is low operating costs and automatic power generation for your facility. All cost saving reasons to consider a new packaged firetube boiler.

3. Fuel Usage

If your old unit is designed to fire low grade fuel oil, or if you need to evaluate propane or any other different fuel capability, review the conversion costs along with existing maintenance, performance, and efficiency issues to see if the time is right to consider a new boiler purchase. Many times an investment is made in an old unit when the costs associated with the next major maintenance requirement will justify a new unit. The result is wasted money on the old unit upgrade. 

4. Efficiency

Your Cleaver-Brooks representative can help check out the efficiency of your old boiler with a simple stack analysis. The data will give you a general idea of the difference between the fuel cost of the existing boiler and a new unit. Based on the results of the stack evaluation, a more comprehensive evaluation of your boiler room requirements should be performed. Boiler size, load characteristics, turndown requirements, back- up requirements, fuel type, control requirements, and emission requirements, all should be evaluated. The result will be an accurate review of the potential savings in fuel, maintenance, and boiler room efficiency that can mean sub-stantial cost improvement for your facility.

Summary

Selection of a boiler with “designed-in” low maintenance costs and high efficiency can really pay off by providing ongoing savings and maximizing your boiler investment. Remember, first cost is a relatively small portion of your boiler investment.

High boiler efficiency is the result of specific design criteria, including:

• Number of boiler passes
• Burner / boiler compatibility
• Repeatable air/fuel control
• Heating surface - Pressure vessel design

Boiler efficiency calculations that are accurate and representative of actual boiler fuel usage require the use of proven and verified data, including:

• Proven stack temperature
• Accurate fuel specification
• Actual operating excess air levels
• Proper ambient air temperature
• Proper radiation