Pumps & Systems, October 2008
Since municipal codes frequently deal with the most crucial areas of public life-covering the safety of life and property-it is understandable that preference is given to tools and methods that are "tried and true" over ones that are untested. The challenge becomes how to take advantage of new advances in technology while recognizing the importance of maintaining an uncompromising level of safety and security. The answer can lie in close cooperation between officials who champion the integrity of the municipal code system and individuals experienced in the implementation of innovative technologies.
Over the years, sprinkler systems have proven to be an indispensable tool in reducing risk related to fire damage. In most cases, it is a relatively simple process to connect the sprinkler system to the municipal water supply, which ensures an acceptable flow rate and static pressure. In rural areas where the municipal water supply is inaccessible, however, the process can be decidedly more rigorous. Brian Peterson at Schwab, Vollhaber, and Lubratt, Inc., recently encountered two such installations, and was able to provide a solution that is not only safer and more reliable, but also easier to install and own.
Elk River, Minn.
The Renner family has been drilling wells in the Minneapolis area ever since Max Renner brought the trade with him from Berlin, Germany, back in the late 1800s. In 1932, his son Edwin founded the E.H. Renner Well Company. Today, the company is still family owned and operated-and growing. The company, now called E.H. Renner and Sons, Inc., recently needed a new building to house their growing fleet of well drilling equipment. The new 12,000-sq ft building required a sprinkler system to comply with Minnesota State fire code. Normally, it would have been a simple matter to connect the sprinkler system to the municipal water supply, which would ensure ample flow rate and capacity in the event of a fire. Elk River, Minn. (just outside of Minneapolis) was not served by a municipal water supply, so the sprinkler system needed to be served by a well.
Since well drilling is E.H. Renner and Sons' business, drilling the well would be the easy part. However, ensuring that a fire suppression system has the necessary capacity would typically require excavating a massive reservoir to store water that the system could draw from in the event of a fire. In fact, a furniture mall located very close to the Renner facility had just such a fire protection reservoir located below their building (a sort of "wet basement"). Of course, this solution would add significant expense to the Renner project and would create additional maintenance responsibilities and costs.
Another possible solution lay in subdividing the building into several individual "bays" in which to store the vehicles. This would nullify the requirement for the sprinkler system, since the building would no longer be one contiguous space. However, this plan came with some costs and drawbacks. The several interior walls that would need to be erected would require extra costs in both labor and materials. Additional heaters would need to be installed to serve each of the individual bays in order to protect the vehicles from the cold Minnesota winters.
Roger Renner contacted Brian at SVL, who worked with Danfoss Drives to develop a solution using variable frequency drives. Working closely with the state's fire marshal and electrical inspector, Brian and Roger were able to implement an innovative VFD-based solution that was more cost-effective, reliable and compact than the traditional reservoir approach.
A 3-hp drive operates a submersible pump that provides water at a flow rate of 40-gpm for regular processes in the building such as irrigation. A pressure transducer monitors the sprinkler system, which is pressurized with air instead of water to protect against freezing. When the pressure drops suddenly, indicating that one or more of the sprinkler heads have been triggered by a high heat condition, the fire protection water supply automatically switches over to a 30-hp drive. The fire protection water supply is connected to a separate submersible pump capable of supplying water at 385-gpm for the fire suppression.
Using two different sizes of variable frequency drives and pumps allows the system to meet the needs of both everyday activities and a fire emergency, while realizing significant energy and cost savings on a daily basis. The smaller drive and pump are able to cost-effectively serve the lower flow requirements of the everyday activities of the facility, while the larger drive and pump ensure that the fire suppression system will have ample capacity in the event of a fire. Both are able to provide constant pressure at variable flow rates, which provides reliable constant pressure operation under both conditions.
VFDs made a separate reservoir unnecessary and allowed the building to remain one contiguous structure served by a single heating unit. In the end, the solution saved the company both money and time, while providing the flexibility and safety they needed.
Atwater, Minn.
Not far away, the Central Lakes Cooperative (CLC) fertilizer plant in Atwater, Minn., serves as a similar example. Like the Renner facility, CLC also lacked access to a municipal water supply. CLC looked to Mike Steffl of Steffl Drilling and Pump to drill their well and provide the necessary components to meet fire code requirements.
The typical solution in this case likewise required installing a submersible pump and a 100,000-gallon reservoir to ensure adequate water capacity for the system. This reservoir would not only require a large excavation and a significant amount of concrete, but would also take up a lot of space. Mike had also previously worked with Brian and knew that there might be a more cost-effective solution available using VFDs. Working closely with the state's fire marshal and electrical inspector, Brian and Mike were able to put together a system that was far easier to install and maintain than the traditional alternative.
CLC has a similar installation configuration to the Renner facility, but uses a single drive instead of two.
