How the needs of the marine industry prompted a closer look at membrane enclosures—and resulted in revisions to NFPA 33 that could affect a range of industries
BY NANCY PEARCE
FOR YEARS, THE MARINE INDUSTRY has followed a practice of constructing large membrane enclosures, located both inside and outside buildings, designed to contain dust and fumes associated with sanding and painting vessels. Typically, the enclosures are constructed of a metal scaffolding, to which a type of plastic shrink-wrap is attached. The enclosures are large enough to surround most or all of the vessel, and painting or other spray work can be conducted inside the space to contain a variety of materials and fumes produced by the finishing and refinishing processes.
While there were issues with using the enclosures outdoors, the more serious problems involved their use inside sprinklered buildings. The industry felt the approach was safe, even if spraying inside membrane enclosures did not meet the requirements of NFPA 33, Spray Application Using Flammable or Combustible Materials. The chief concern was that membrane enclosures inside a building could delay sprinkler activation in the event of a fire inside an enclosure, and could also prevent water from ceiling sprinklers from getting to a fire inside the enclosure, potential problems that conflicted with NFPA 13, Installation of Sprinkler Systems.
According to NFPA 33, spray finishing could only be performed inside spray booths, spray rooms, or open spray areas, and all spray areas were required to be protected by automatic fire protection systems. The problem was that extra-large standard spray booths were not available for many industries; marinas, for example, often needed enclosures as long as 150 feet to cover large vessels, and the only way to accomplish that was by constructing a temporary enclosure where the processes could take place. In addition, the vessels were heavy and were not easily transported from the marinas to off-site spraying or refinishing facilities. Authorities having jurisdiction (AHJs) were left to decide whether or not to allow the practice.
The marine industry wasn’t the only one interested in conducting spraying operations inside such enclosures. Many other industries that produced large components requiring sprayed-on applications of protective coatings—from aircraft to bridges to hydro-electric facilities—were looking at how to use enclosures for certain finishing processes, and shared the marine industry’s concern that the practice was not technically allowed by the standard.
NFPA’s Technical Committee on Finishing Processes, the committee that oversees NFPA 33, was aware of the limitations on the use of such enclosures for spray finishing, and recognized that the overlapping concerns about placing such enclosures inside sprinklered buildings could really only be addressed by changes to NFPA 13. Without those changes, the committee could not allow such spraying inside sprinklered buildings. The committee needed to clarify that membrane enclosures were meant to be temporary structures set up for a single workpiece. Additionally, they needed to ensure that the electrical equipment, ventilation, and other protections inside membrane enclosures provided an equivalent level of safety as those established for other spray areas.
Necessary but nonconforming
In 2012, the technical committee held a pre–first draft meeting to discuss, among other topics, a proposal for a revision to the 2016 edition of NFPA 33. The proposal originated with an enforcer from the building department in Broward County, Florida, who had been dealing with an issue involving spray painting large yachts at local marinas. These vessels were difficult to move, and the marinas were trying to figure out how to perform spray painting for vessels that remained in the water, in the boatyard, or inside marine buildings while ensuring fire safety for the facility, the vessels, and workers.
The proposed revision called for allowing the industry to continue the practice of spraying inside membrane enclosures, which the enforcer noted had originated in Europe about 20 years earlier. He described the membrane material as complying with NFPA 701, Standard Methods of Fire Tests for Flame Propagation of Textiles and Films. In addition, the enclosed space is provided with an interlock that shuts down the spray apparatus if the ventilation fails to minimize (or limit) a particular concentration of flammable vapors and mists in the exhaust stream. Means of egress, sources of ignition, and electrical classifications were also considered in the design of the membrane enclosures.
Committee members were faced with several key concerns. First, they needed to decide whether or not any changes to the standard should be specific to the marine industry or if they should be generic enough to cover other large workpieces, such as aircraft or smokestacks, that may need to be sprayed in locations away from traditional spray booths. How could the standard allow a membrane enclosure for one industry and not for another? It became clear that whatever changes were made, they would have to be applicable not just to the marine industry but to other industries faced with a similar dilemma.
Another issue was the difference between the use of membrane enclosures outside buildings versus inside. The committee recognized that the use of membrane enclosures for spraying workpieces outside a building could readily be incorporated into a change in the standard, but that the use of those same enclosures inside a building created challenges in the form of delays in sprinkler activation and in water getting to a fire inside the enclosure. NFPA 13 contained strict requirements prohibiting the installation of materials below sprinklers that could severely obstruct the discharge of water, with the exception of components such as listed drop-out ceilings, which can be installed below ceiling sprinklers because they are designed to drop out in the event of a fire to allow ceiling sprinklers to activate in a timely manner. Other special rules, such as those for cloud ceilings, also determine the extent of obstruction that can be tolerated. The plastic material used for the membrane enclosures did not meet those criteria, however, and it became clear to the committee that the membrane enclosures could not be installed inside buildings without violating NFPA 13 requirements.
In the marine industry, enclosures are created with scaffolding and a special plastic shrink-wrap. Portable systems filter and exhaust spray vapors. Photographs: Southern Cross Boat Works; Nancy Pearce; Jim Parks.
As the NFPA 33 committee was discussing these issues, the 2016 edition of NFPA 13 was also in revision. The technical committee for NFPA 33 contacted the NFPA 13 committee to ask for representation on an NFPA 33 task group formed to look at the enclosure problem. The task group ultimately concluded that unless there was an approved method for enclosing structures inside a membrane without obstructing sprinklers, the use of these enclosures inside buildings could not be incorporated into NFPA 33.
However, during the second draft meeting of NFPA 13, information was submitted to the committee about a new material that had been evaluated by Underwriters Laboratories and that seemed to offer a promising solution to the enclosure problem. The plastic material contained seams designed to fail during a fire; with the material split open, water from sprinklers above could reach the fire with minimal delay in activation time. With this information, the technical committee for NFPA 13 modified the standard to allow the use of this material below sprinklers. The change opened the possibility of a corresponding revision to NFPA 33.
To observe the membrane enclosure setup and see first-hand what safety precautions were—and should be—in place during the spraying of vessels, tours of two Florida marinas were arranged as part of a pre–first draft meeting for the NFPA 33 revision. At Lauderdale Marine Center and Broward Shipyard, the committee observed the setup of the ventilated membrane enclosure used for spray painting and saw a demonstration of a vapor detection system used inside an enclosure that was interlocked with the ventilation system. While there were still some concerns, the committee in general understood the need for addressing the concerns of the industry, and the change was eventually approved. The enclosures, by definition, are temporary (180 days or less) and can only be used for the piece in which the enclosure was erected. The enclosure material, referred to as the membrane enclosure, must be NFPA 701 compliant, and if installed inside beneath a sprinkler it must be listed in accordance with the new listing requirements in NFPA 13. The enclosure can only be used one time.
Jim Parks, operations manager for Lauderdale Marine Center, was a longtime advocate for the change to NFPA 33 and was part of the process from the beginning, attending every meeting and answering questions posed by committee members. Parks told the committee that the marina had been using this method for the past eight years as a way to control dust and grit during preparation work, and that following the preparation stage the membrane is removed from the scaffolding and discarded. All dust and deposits are vacuumed. A new membrane is then installed for the spray-painting sequence to control vapors and overspray. Initially, the fire department stopped the operation because it was not compliant with NFPA 33, prompting his involvement in working toward changes that would satisfy both the technical committee's concerns and provide a workable solution for the industry.
Read Eye of the Storm
How a Florida marina landed at the center of the NFPA 33 discussion. Photograph: LMC.
With the change to the standard, industries with large workpieces that cannot easily be prepped or treated in traditional settings (such as spray booths, spray rooms, or spray areas) now have a method to safely apply the spray-finishing requirements in NFPA 33. The committee attempted to make the new Chapter 18 generic enough for use by all impacted industries, but also recognized that most of the input during the last revision cycle came from the marine industry. The 2018 edition of NFPA 33 is currently under revision, and a task group involving other stakeholder industries is reviewing the requirements to ensure the code as written can be applied effectively across a broad range of industrial practices.