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Technical Tips & Information
Need a Boiler Room?
Many factors should be considered when installing a new boiler room for your facility. First considerations include the required steam demand and operating pressure. An undersized boiler installation will lead to production and maintenance problems. An oversized boiler installation without proper lead lag controls will waste large amounts of fuel. The forecast for this year points to instability in fuel prices. Boilers operate at best efficiency when the load is within 60– 80% of the boiler capacity.Miura Boilers are offered in 170 and 270 psig ratings. Due to safety valve settings, the actual operating pressure of a boiler will be 10-15 psig less than its stamped working pressure. Higher pressure ratings escalate not only the price of the boiler but all steam related pipe and fittings. Virtually all states require ASME code installations which means any piping above 150 psig must be schedule 80 and equivalent ratings for valves and fittings.
Miura Boiler water tube boilers are offered in sizes of 25-300 horsepower and in pressure ratings to 270 psig. High tech controls permit boilers of this type to operate at efficiencies of 85% from 10-100% of full load. Boilers can come to full pressure in five minutes which avoids boilers on idle to meet load swings. When coupled with a PLC style lead lag control system, 85% efficiencies can be maintained over a wide load range.
Although the boiler selection process is important, usually the cost of the boilers represent about 45% of the total installed cost for a complete new boiler room.
On the water conditioning side, costs will be incurred for a water softener, feedwater heater or deaerator, and chemical treatment system.
Feedwater heaters are non ASME code vessels and designed to heat water to 200 F. Eliminating oxygen and carbon dioxide is handled through the addition of chemicals to bind the gases and prevent damage to the boilers and steam system.
Deaerators are ASME coded pressure vessels which heat water to 225-227 F at 5-7 psig pressure. Dissolved gases are driven from the feedwater by boiling the water which substantially reduces the amount of chemical treatment required to condition the water. Deaerators cost 2-3 times as the equivalent sized feedwater heater. The higher initial cost is typically recovered within two years by reduced chemical costs.
Blowdown separators permit separation of the vapor from the liquid when doing blow down on the boilers. Blow down includes flash steam and water at 212 F. Most local codes require that blow down to a drain be cooled to 160 F to prevent growth of bacteria. Blowdown separators include a temperature control water cooling valve to maintain blowdown water waste at temperature below 160 F.
ASME code requires that multiple boilers be connected to the main steam header through two primary isolation valves, one check valve, and include a blow off vent valve. Any welding of piping through the final valve must be certified.
Fuel efficiency should be considered in the cost evaluation. The final bid for a complete boiler will generally break out as follows; 45% boilers, 25% auxiliaries with piping, and 30% labor.
As an example, consider an installation with two 200 HP boilers at $250,000.00 installed with all auxiliaries. As a quick estimate, boilers would cost about $100,000.00. Type “A” boiler has an efficiency of 81%, type “B” 85%. Assume gas cost is $6.00 per MCF and the boilers are operated at a 70% firing rate 52 weeks per year. Fuel savings over a year for the more efficient boiler is $29,050.00 per year.
When considering final costs for a new boiler installation, consider at a minimum a three year total cost window. In this three year window total your installed cost for the new boilers, fuel operating costs, maintenance costs, manpower costs, and inspection costs. This type of approach will provide for the best overall return and not a decision based on lowest initial costs for boilers only.
Operating in a facility with a single boiler where steam is critical to the operation of the plant is akin to flying the Pacific Ocean in a single engine airplane. Doable but very risky.
If you are in the market for new boilers or a boiler upgrade, please give us a call for a complete review of your requirements and a single source installed price.