Steam Audits Continued from page 74


and provide a great opportunity for significant fuel sav- ings. The audit will delineate the detail, providing the basis for an informed decision. It’s also important to investigate whether the boiler has


been overheating. If so, there might be problems with either the boiler’s insulation or its gasketing, which could lead to damaged and unsafe equipment. The cost of repairs to correct these issues is relatively nominal. Investigation


sure can be reduced, fewer Btu per hour will be used, cut- ting the customer’s energy costs.


Piping conditions A complete facility audit will review steam piping for


energy loss through radiation and steam leaks. Heat loss through radiation can be reduced by insulating the pipes and associated valving.


Feedwater system An auditor will investigate the feedwater supply to the


boiler and condensate returns. A main objective is to determine whether water sent


directly into the boiler is free of dissolved gases such as oxygen and carbon dioxide, which can cause destructive corrosion to the boiler and condensate lines. If such gases are present, the auditor may recommend installing a deaerator. Deaerators are an option if the boiler operates at 75 psig or greater, has limited standby capacity and is using 25 percent or more cold water make-up. Auditors will examine the condensate return system


Steam audits often consist of a review of the pipe layout design. A complete facility audit will review steam piping for energy loss through radiation and steam leaks.


may indicate that the boiler is seriously scaled on the waterside. If so, it may have to be acid cleaned, which could be costly, or it could be time to replace the boiler. During the efficiency analysis, the auditor is checking


for specific elements in the flue gas that indicate the effec- tiveness of the burner to efficiently oxidize the fuel. Additionally, the auditor is looking for the level of nitro- gen oxides and the stack temperature above the saturated steam temperature within the pressure vessel. Results could lead to recommending an oxygen trim system sens- ing flue constituents and automatically adjusting to help improve combustion efficiency. If the nitrogen oxide level is high and the boiler is in a non-attainment area for ozone, a flue gas recirculation (fgr) system may be recommend- ed and retrofitted to bring the boiler package into air qual- ity compliance. If the stack temperature is high it may mean the boiler


is scaled or sooted, inhibiting proper heat transfer. A cleaning and re-tuning of the burner will, in most cases, alleviate this problem, bringing the boiler/burner package back to an acceptable fuel-to-steam efficiency. The stack temperature may also indicate that the boiler


is an excellent candidate for a feedwater economizer, reducing the stack temperature and adding to the boiler’s efficiency by transferring Btu in the stack to usable ener- gy in the boiler’s feedwater.


Reducing operating pressure An audit will also determine whether it’s possible to


reduce the boiler’s operating pressure. Auditors look at the process and the existing piping layout to determine whether the diameter of the piping, controls, steam traps and control valves can tolerate lower pressure. If the pres-


Plumbing Engineer


It is important to determine whether water sent directly into the boiler is free of dissolved gases such as oxygen and carbon dioxide, which can cause destructive corrosion to the boiler and condensate lines. If such gases are present, the auditor may recommend installing a deaerator such as the one shown above.


Continued on page 78 January 2011/Page 77


and how much (hot) condensate is being returned to the boiler’s feed tank. It takes less heat to turn condensate back into steam because it returns with much of its sensi- ble energy. The result could be thousands of dollars in sav- ings annually.


Steam trap audits Steam trap audits are typically performed during a com-


plete facility audit. Examiners look for traps that are “blowing through” (pressurizing the condensate line or lines) and causing water logging and excessive flash steam venting. Water hammer occurs when steam condenses in a hori-


zontal section of the steam distribution piping, usually caused by a poor condensate drainage strategy. Steam picks up the water, forms a “slug” and hurls it at high velocity into a pipe elbow or other restrictive device, cre-


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