This specification defines the minimum requirements that must be obtained for the design and fabrication of the vertical gas flow, horizontal tube economizer. No deviation from this specification is permissible without documented approval.

1. DESCRIPTION OF OPERATION

The purpose is to recover waste heat utilizing the established principle of a gas to liquid heat exchanger. The heat exchanger should be a bare, welded or extruded finned tube coil assembly installed either inside or parallel to the boiler exhaust stack or duct. Feedwater under pressure will circulate in the tubes of the coil and the heat from the exhaust gases is transferred to the water.

2. THE HEAT EXCHANGER

The heat exchanger shall be constructed and stamped in accordance with the most recent edition of the ASME Code, Section I.

1. Design

1. The unit shall have, but will not be limited to the following connections:

1. Feedwater inlet
2. Feedwater outlet
3. Flue gas inlet
4. Flue gas outlet
5. Vent
6. Drain
7. Thermometers (2)

2. The design pressure shall meet or exceed the boiler design pressure.

3. Maximum allowable pressure drops shall be 15 PSIG for the feedwater

and 1.5 inches W.C. for the flue gas.

3. Tubes to be welded with a two pass TIG process.

4. Return bends shall be cold bent or manufactured by a forging process.

5. Cold bent tubes will be assumed to have 30% thin out for code calculations. Forged return bends shall have no thin out of wall thickness.

6. Method of tube supports shall allow for the free flow of hot gases around the welds, return bends and manifolds.

7. The unit shall be non-steaming (30° F minimum approach), suitably arranged for internal tube acid cleaning, fully drainable and soot-blowing with air, steam or water as washing medium.

8. Units in #2 oil or heavier oil firing should include provisions for soot-blowers.

9. A gas tight inner seal welded steel casing of a minimum of 10 Ga. thick shall be insulated and covered with 27 Ga. Thick galvanized corrugated steel lagging. Uninsulated surfaces shall be painted or galvanized.

10. The unit shall be a shop assembled package type and shipped within shipping limitations and protected to prevent damage during transit.

11. Spiral Fintube Economizers:

1. The tube pitch shall be square to insure ease in cleaning.

Fin Pitches – Maximums:

• Coal Fired         2 per inch
• #5 and #6 Oil    3 per inch
• #4 Oil                  3 ½ per inch
• #2 Oil                  4 ½ per inch
• Natural Gas       6 per inch

2. Minimum clearance between fin tips – 5/8 inch.

3. Fins shall be welded to tubes. Tension wrapped, embedded, cast iron or brazed fintubes are not acceptable.

4. One 16" square bolted access door shall be provided per sootblower wall box.

2. Performance

1. Economizer shall be designed to operate at 100 percent load without

bypassing any flue gas or feedwater.

2. Fouling factors to be used for various fuels:

• Coal Fired            0.01
• #4 and #6 Oil       0.005
• #2 Oil                     0.003
• Natural Gas          0.002

3. The proposal shall include the following information:

1. Tubes and Bends

• Maximum allowable working pressure
• Minimum tube wall
• Minimum bend wall
• Number rows wide and rows high
• Outside diameter of tubes
• Material of tubes and fins
• Fin description

2. Shell/housing/transitions (if furnished)

• Type of material
• Thickness

3. Insulation

• Type material
• Thickness

4. Metal lagging

• Type of material
• Thickness

5. Flue gas connections

• Inlet size
• Outlet size

6. Feedwater connections

• Size
• Connection type

7. Dimensions

8. Weight

9. Degree of assembly

10. Performance for full, average and low loads:

	Tube side	Shell side
Total Fluid Entering	LB/HR	LB/HR
Temperature In	° F	° F
Temperature Out	° F	° F
Pressure Drop (psi)	PSIG	In. W.C.
Specific Heat
Fouling Resistance
Heat Exchanged
U External
LMTD
External Surface