Dry Firing in Boilers

Dry Firing pic

Dry Firing
Image: preferred-mfg.com

As the president of Preferred Utilities Manufacturing Corporation, Redding, CT-based industrial equipment professional David Bohn led the fuel oil and boiler equipment manufacturer to a 380 percent increase in annual corporate revenue. In addition to his administrative accomplishments, David Bohn has expertise in multiple technical areas including the prevention of dry firing in boilers.

A big problem in the boiler industry, dry firing occurs when something interferes with the regular supply of boiler feedwater. If the boiler runs out of water, and safety features fail to engage, steam pressure will soon drop to zero. Although the true cause of this drop is a complete lack of boiling water (and, therefore, steam), the boiler will automatically attempt to make up for the lack of steam pressure by increasing internal temperature. Within minutes, high temperatures can irreparably damage the boiler due to a phenomenon called metal creep.

Boiler owners and/or operators can reduce the risk of dry firing by ensuring that advanced safety controls are set to trip the boiler offline when water supply is interrupted. They can also prevent dry firing by installing header-pressure transmitters on variable-speed-drive pumps, monitoring stack temperature closely, and performing regular automated low-water cutout tests.

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Preventing Dry-Firing in Boilers

Preferred Utilities Manufacturing Corporation pic

Preferred Utilities Manufacturing Corporation
Image: preferred-mfg.com

Since 1995, David Bohn has served as president of Preferred Utilities Manufacturing Corporation in Danbury, near Redding, CT. David Bohn draws on a 30-year history with the Redding, CT-area company, during which time he has gained an in-depth knowledge of boilers and the risk of dry-firing.

A boiler depends on balanced temperature and pressure levels to operate correctly. If a boiler ever becomes empty of water, pressure drops to zero and the boiler works harder to restore pressure. The lack of water leads the boiler to overheat and can permanently damage the metal mechanism, assuming an emergency feedwater pump does not first introduce cold water to the hot metal and cause an explosion.

Testing and monitoring are key to the prevention of dry-firing. Contemporary controller systems have mechanisms for monitoring stack temperature, so that excess heat would prompt a shutoff. Similar shutoff procedures may occur with automated low water testing.

Plant owners can also help to prevent dry-firing by installing redundant feedwater pumps, which engage in the case of pump failure and can help the mechanism avoid drying. Similarly, a feedwater header-pressure transmitter can emit an alarm and engage a second pump if pressure drops, thus reducing the chance of a dry boiler.

A Brief Look at the Advanced Performance Inject-Aire Low NOx Burner

 

The president of the Preferred Utilities Manufacturing Corporation, David Bohn directs new product development and handles corporate revenue and growth efforts. David Bohn took the helm as president after joining the company’s Redding, CT, office and working his way up the ranks. He has spearheaded a number of projects in his leadership role, including the development of the Advanced Performance Inject-Aire (API-AF) Low NOx Burner.

The API-AF offers extensive fuel-burning capability and an impressive efficiency that significantly reduces greenhouse gas emissions and the overall carbon footprint of users. Designed to produce a stable flame regardless of firing rate, the burner can fire a range of fuel oils and natural gas. It incorporates variable-frequency drive motor controllers for enhanced control of the forced-draft fans, which in turn provides more air for combustion and results in a reduction of energy consumption.

Preferred Utilities engineers constructed the burner for use in single-burner applications, such as cast iron sectionals, watertube boilers, and high temperature hot water (HTHW) generators. Its installation at the Stapleton Houses managed by the New York City Housing Authority has contributed to prolonged boiler life, a reduced carbon footprint, and increased electrical and fuel savings. In addition, the API-AF limits NOx emissions and meets compliance standards for Local Law 87, a green building and energy efficiency ordinance set forth by the New York Mayor’s Office of Sustainability.

For additional information on the burner, visit preferred-mfg.com/products/wn/API-AF-Burner.

FAQ: What is Boiler Dry-Firing?

Preferred Utilities Manufacturing Corporation pic

Preferred Utilities Manufacturing Corporation
Image: preferred-mfg.com

Redding, CT resident David Bohn serves as president of the Preferred Utilities Manufacturing Corporation in nearby Danbury, CT. The firm engineers and manufactures commercial and industrial utility products such as boilers. Accordingly, David Bohn remains apprised of developments in the HVAC industry as well as relevant safety concerns.

Dry-firing is a common concern for those who work with boilers, especially on an industrial scale. Keep reading to learn about the common causes of dry-firing and the best ways to prevent it.

Question: What does in mean when a boiler dry-fires?
Answer: Boilers rely on carefully-managed levels of pressure and temperature. When a boiler runs out of water, the steam pressure plummets. The boiler works overtime to create more pressure, but the lack of water also causes a cooling failure. This causes the boiler to become very hot very quickly.

Q: How is dry-firing caused?
A: Dry-firing is a perfect storm of problems. First, the feedwater supply must be interrupted. Safeguards such as a low-water cutout alarm and a flame safeguard system must also be disabled or malfunctioning, as these safeguards would usually turn an emptying boiler’s flame off. Lastly, operator error or failure to observe the previous problems is usually a contributing factor.

Q: How can dry-firing be prevented?
A: Installing redundant feedwater pumps allows for continued boiler function if one pump fails. Special pressure transmitters can help operators monitor pressure more efficiently, and a combination of regulations and equipment for boiler testing can help operators catch problems early, before a dry-fire occurs.