The risk of catastrophic fires in industrial forging facilities is a reality the industry faces daily. However, the risk can be mitigated with the proactive installation of an appropriate fire-suppression system. In many situations a water-mist system is the ideal solution.
Industrial forging facilities are no strangers to intense heat and fire. Unfortunately, these conditions frequently lead to unintentional fires, which can result in catastrophic facility damage.
“We had a couple of fires in our pump room and in one of our press pits that almost got out of hand about a year ago,” said the operations manager at one of the largest forging facilities in North America. “This got us thinking about a fire just a few years ago that started in the pump room of another very large forging plant. That fire ultimately caused a facility that had been operating for over 100 years to close its doors. We knew we needed to do something.”
Fortunately, proven fire-suppression technology is available that can help you avoid such disasters.
This operations manager and other members of the forging facility’s project team spent several months evaluating various technologies to satisfy their requirements and concerns. Top priorities for the fire-suppression system were as follows:
- It must be effective and reliable in a forging environment.
- It must protect critical assets to minimize downtime.
- It must be safe for personnel.
Based on their consultation with other facilities and fire-protection professionals, this facility ultimately selected a water-mist fire-suppression system as the preferred technology.
Facility Background and Hazards of Concern
Industrial forging facilities produce a wide variety of products for aerospace, automotive and other industries. Many are produced using open-die forging techniques with multiple hydraulic presses. A central hydraulic pump room is used to supply pressurized hydraulic fluid to these presses via steel hydraulic piping installed in shallow trenches between the pump room and presses. Each of these areas poses unique fire hazards that, in the event of a fire, could result in significant damage and extended unplanned shutdown of operations.
Considering that such a facility – by the very nature of its operation – must bring a mass of steel weighing several tons at a temperature of near 2000˚F (1093˚C) in close proximity to highly combustible hydraulic and lubricating oils, this should come as no surprise. While good housekeeping can help to reduce the probability and severity of fires in these areas, this alone is not sufficient to satisfactorily mitigate the fire risk. The following are summaries of primary concerns for each of these areas.
Hydraulic Presses/Pit Areas
While small fires around the presses are quite common in normal operation as hot scale is removed, these fires generally extinguish themselves in a few seconds or with minimal manual intervention. The areas of primary concern for a larger fire event that could get out of control are:
- The surfaces on and around the press itself that may have a coating of hydraulic oil
- The potential for a spray fire from a leaking hydraulic joint or piping
- The pit area below the press where oil or other combustibles could be ignited from hot scale falling into the pit during forging
Local application protection (where the fire-suppression system provides local protection for an individual piece of equipment, not a complete enclosure) is required for these hazard areas.
The central hydraulic-pump room is isolated from any direct impact from the forging operation. However, this area poses a tremendous fire risk due to the large fuel load (hydraulic oil) it contains. Potential ignition sources and fire scenarios include bearing failure on a motor or pump; fire from outside the room reaching into the room via the pipe trenches to the presses; and electrical fires originating from motors, electrical panels or any other electrical source. A fire event could result in damage to other piping or pumps in the room. This, in turn, could lead to spray fires, as well as overheating and significant leaking from the hydraulic-oil recycle tank, which could result in exponential growth of the fire. Total flood protection (where the hazard is completely enclosed and the entire volume is protected) is required for this type of hazard.
Trenches themselves do not generally pose significant risk because there is no inherent ignition source or critical equipment in these areas. Since these trenches connect areas that do have serious fire risk and contain critically valuable assets (the hydraulic pump room and presses), however, it is highly recommended to provide suitable protection to mitigate the risk of fire propagation in the trench. Local application protection is required for these hazards.
Evaluation of Technologies
In order to select the best-available technology to meet the facility design requirements, a variety of suppression-system technologies was considered.
• Carbon dioxide (CO2): Carbon dioxide has a long history in fire suppression. It has been used in fixed fire-protection systems since before WWI, and an NFPA standard has existed since at least 1929. These systems have been demonstrated to be very effective at extinguishing Class-B fires. This includes both total flood application and local application. Although it is a very effective agent, CO2 can be lethal to personnel and is generally not recommended for use in areas where there is potential for personnel to be present during discharge.
• Hybrid: Hybrid systems use an inert gas and water, both of which are critical to the extinguishment of a fire. Hybrid systems are a relatively recent development for which the first FM standard, 5580, was introduced in 2009. However, the standard does not provide testing protocols or recognize hybrid systems for local application use. Currently, there is no NFPA standard for hybrid systems.
• Clean agent (HFC-227ea, FK-5-1-12, IG-55, etc.): The extinguishing mechanism for these agents varies, but all require achieving and maintaining a volumetric agent concentration specific to the agent used. Clean-agent suppression systems, for which the first NFPA standard was introduced in 1968, are waterless fire-extinguishing agents most commonly used for protection of sensitive electronic equipment such as that found in data centers, server rooms, etc. However, none of the agents are approved for local application use as needed in a forging environment.
• Water mist: Water mist technology was introduced in the 1940s for maritime applications and has been used extensively in industrial applications since the late 1980s. FM Approvals Standard 5560 and NFPA 750 for water mist were introduced in 1995 and 1996, respectively. These systems produce very fine micro-droplets resulting in a very large surface-to-volume ratio, making them very efficient at absorbing heat. Fire extinguishment is achieved as these droplets provide cooling via evaporation, which displaces oxygen in the vicinity of the fire. Water mist does not require an air-tight enclosure and offers additional benefits such as very low “agent” cost and scrubbing of smoke/toxic gases. Both total flood and local application approvals and test protocols are in place from FM and IMO (International Maritime Organization).
After a thorough evaluation of technologies, water mist was selected because it was the only technology deemed acceptable for protecting all the identified hazards that was also safe for plant personnel.
Hazards Requiring Protection
The areas requiring protection may be broken down into three distinct types: the central hydraulic-pump room, hydraulic presses with pits, and the trenches that are the connection path between the hydraulic room and the presses.
The hydraulic-pump room measures approximately 65 feet long x 45 feet wide with a 30-foot ceiling. The room contains high-pressure hydraulic-fluid pumps that are mounted at a mezzanine level along with transfer pumps at the main floor level adjacent to the hydraulic-oil recycle tank. This approximately 15,000-gallon tank is supported on concrete piers approximately 3 feet above the main floor. The hydraulic-pump room is protected using total flood design. Equally spaced nozzles are mounted at the ceiling, with additional nozzles used to protect the trench area below the mezzanine and below the hydraulic-oil recycle tank.
Two large hydraulic open-die forging presses are protected with local-application design using a nozzle grid just above the top of the press and two additional rows of nozzles around the press perimeter. Nozzles and piping are located to avoid interference with operating equipment. The pit areas below each press are protected using equally spaced ceiling-mounted nozzles throughout the pit.
Trenches (approximately 3 feet deep) contain piping that connect each hydraulic press to the pump room. These trenches are protected using local application design with equally spaced nozzles running the full length of each trench.
Water Mist Fire-Suppression System
System Design/Nozzle Layout/Pump Sizing
The first step in the system design requires laying out the nozzles for each hazard in accordance with the manufacturer’s testing and approvals. The layout dictates the water-flow requirement for each hazard, with a zone valve provided for each separate hazard. Next, a determination must be made based on a risk assessment of the hazards as to which will require simultaneous protection. Once these determinations are made, the pump system is sized to meet the demand requirements of the largest zone or combination of zones requiring simultaneous discharge. For this system, protection of the pump room simultaneously with the connecting trenches determined the pump size required.
System Equipment Summary
- Nozzles (open/deluge-type)
- All stainless steel pipe network (combination of schedule-40 and seamless tubing)
- Zone valves for protection of individual hazards
- Pump system (three pump modules)
- Detection and controls – optical detection for pump room, heat detection for trenches, manual activation from constantly attended control room for presses
System Operation Summary
Input from the detection or manual station will be processed at the releasing control panel to open the appropriate zone valves and start the appropriate number of pump motors. The pump system will continue to operate for a minimum of 30 minutes unless reset at the panel. The system is capable of extended discharge for as long as water is available.
Due to the unique fire-protection challenges within this industrial forging facility, a water-mist system was found to be the ideal solution. Systems are available with suitable approvals from manufacturers having considerable experience with the hazards typically found in an industrial forging environment. Ultimately, living with the risk of catastrophic fires in industrial forging facilities is unnecessary. It can be mitigated with the proactive installation of a proper fire-suppression system.