DEPARTMENT OF LABOR
OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION
Docket No. H054A
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OSHA’S PROPOSED RULE CONCERNING
“OCCUPATIONAL EXPOSURE TO HEXAVALENT CHROMIUM”
69 FED. REG. 59305 (OCTOBER 4, 2004)
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TESTIMONY OF
KENNETH GOULD, REGULATORY COUNSEL
OWENS CORNING
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February 9, 2005
TESTIMONY OF
KENNETH GOULD, REGULATORY COUNSEL
OWENS CORNING
INTRODUCTION
I am Kenneth Gould, Regulatory Counsel for Owens Corning (OC). Among the various products
produced by Owens Corning are fiber glass insulation, continuous strand glass fibers for
reinforcement and textile applications and cement based stone veneer products which are
marketed under the brand name of Cultured Stone. OC appreciates the opportunity to present
testimony that augments its previously submitted written comments concerning OSHA’s
Proposed Rule on Occupational Exposure to Hexavalent Chromium and its potential impact on
those products and their production.
Owens Corning supports and incorporates the positions expressed by the North American
Insulation Manufacturers Association (NAIMA) specifically with respect to fiber glass insulation
and generally regarding the glass manufacturing industry and the proposed rule. I am here today
to briefly address issues relating to the effect of OSHA’s Proposed Rule on Occupational
Exposure to Hexavalent Chromium and Owens Corning’s continuous strand glass fiber and stone
veneer businesses.
CONTINUOUS STRAND GLASS FIBERS
Owens Corning incorporates the concerns and positions expressed by NAIMA regarding
OSHA’s failure to analyze all segments of the glass manufacturing industry in its feasibility
analysis, especially all portions of the glass industry using chromium-rich refractory. One such
segment of the glass manufacturing industry is continuous strand glass fibers. Owens Corning
appreciates the opportunity to provide OSHA with information relating to that product.
However, even given that opportunity, the lack of available exposure data, the timing limitations
for gathering additional data and the unique instances of exposure associated with the production
of continuous strand glass fibers, create uncertainty with respect to the effect of the proposed rule
on Owens Corning’s continuous strand business. This lack of data includes the absence of
information on the continuous strand industry in OSHA’s feasibility analysis.
Manufacturing Continuous Strand Glass Fibers
Continuous strand glass fibers are produced by melting raw materials consisting primarily of
Silica, Clay, Limestone, Dolomite and Soda Ash. Chromates or materials containing chromates
are not used in the production of continuous strand glass fibers. The furnace is a direct melt
operation, meaning that the raw materials are mixed, pneumatically transferred to and melted in
the refractory-lined furnace. The temperature of the molten glass in the furnace is approximately
2900 Deg. F. As with the production of glass fiber insulation, the molten glass is kept at a
constant level by feeding the raw material into one end of the furnace at the same rate that
molten glass flows out of the other end. The attached schematic generally shows the
manufacturing process.
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Typical Continuous Strand Glass Fiber Manufacturing Line
Batch
Furnace
Forming
The molten glass flows out the furnace through refractory lined channels where the temperature
of the molten glass is adjusted to obtain the proper viscosity. The molten glass then flows into
the fore hearths where the bushings are located. A furnace may supply a number of bushings
based on furnace size, pull rate (i.e., the rate at which glass comes out of the furnace), product(s)
and bushing design. The number of bushing positions on a typical furnace range from 20 to 112.
Attached is a schematic of a typical bushing.
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Direct Melt Bushing
The furnace, channels and fore hearths used to produce continuous strand glass fibers are
different than those used to produce glass fiber insulation. The refractory lining is multi-layered,
and each layer contains a varying percentage of chromium. Fugitive emissions in the furnace
area generally are low. The attached schematic shows in greater detail the construction of the
furnace, channel and fore hearth.
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Cutaway of Typical Continuous Strand Furnace, Channel and Fore hearth
Sources of Hexavalent Chromium
The principal source of potential hexavalent chromium exposure is from the chrome refractory
used in critical high-wear areas of the furnace, channels and fore hearths for glass contact. The
refractory used for glass contact is a high purity, dense chromic oxide (>90% Cr2O3) material.
Trace levels of impurities in the refractory, such as sodium, in combination with operating
conditions can lead to the conversion of trivalent chromium to hexavalent chromium.
Chrome refractory is used in continuous strand glass fiber production because of the extreme
temperatures experienced during manufacturing. At those temperatures, the raw materials and
molten glass are highly corrosive. High chromic oxide refractory is the most suitable material for
the temperatures necessary to produce these products. The chrome refractory is corrosion
resistant and has a low stoning potential.1 Typically there is little exposure to these refractory
except during furnace demolition, rebuild and repairs.
At the end of a furnace’s life and during the subsequent furnace rebuild, chrome containing
refractory are removed and replaced. Certain repairs during a furnace campaign may also
necessitate the removal and/or replacement of some chrome refractory. The persons involved in
the demolition and construction during a rebuild or a repair may be exposed to hexavalent
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Stoning occurs when extremely small pieces of the refractory break off or are dissolved in the molten glass,
reforming when the glass cools, and travel through the channels, the fore hearth and then pass through a bushing tip.
Because of the different viscosity of the stone versus the glass, the strand of glass breaks eventually causing all of
the strands flowing from the bushing to break and interrupting production until the bushing can be restarted
manually.
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chromium that may have been formed. A typical furnace lifetime is 12+ years with one major
furnace repair during the life of the furnace.
Continuous strand glass fibers are drawn through platinum alloy bushings. The bushings are set
in a castable refractory with a flat top surface. Each bushing nests to a piece of refractory called
a bushing block that is in contact with the fore hearth flow block. High purity dense chromic
oxide refractory is used in flow block and bushing block applications. A bushing has a limited
lifetime. A typical bushing lifetime is on the order of 200 days after which it needs to be replaced.
It takes about 45 – 60 minutes total to replace a bushing. During a bushing change, the bushing
block may need to be either ground to remove glass penetration that has occurred between the
bushing and the bushing block, or replaced. Bushing blocks typically remain in place for 3
bushing changes. Grinding of the block surface to remove glass is performed to provide a flat
surface for the installation of the new bushing. Flowblocks are not changed, but may be ground
during a bushing block change, again to provide a flat surface. These grinding operations, which
typically take approximately 20 minutes of the total replacement time, may be a source for
exposure to hexavalent chromium which has formed on the chromium bearing refractory.
Exposures to Hexavalent Chrome
Because the furnace, channels and fore hearths are sealed and fugitive emissions from these
sources are low, exposures to hexavalent chrome during routine production of Owens Corning’s
continuous strand glass fibers are expected to be low but insufficient industrial hygiene data is
available to sufficiently quantify those potential exposures. Exposures might also occur during
demolition of the furnace, channels and fore hearths and the grinding that can be part of the
replacement of a bushing. Owens Corning was not able to collect exposure data during
demolition of a continuous strand furnace, channel and fore hearth during the comment period
for the proposed rule because no furnaces were scheduled to be replaced.
Owens Corning has collected a small amount of data during normal bushing changes. Task-based
samples collected during the grinding operation showed exposures during that task ranged from
0.94 – 1.1 g/m3. During a typical workday, no more than 4 bushings are replaced by a
maintenance crew. Thus the total duration of the exposure to hexavalent chrome would be less
than two hours during the work day.
Controlling Exposure to Hexavalent Chrome
Typical Rebuild Operation
Owens Corning already takes steps to minimize potential exposures to dust during furnace,
channel and fore hearth rebuilds. Considering the nature of these demolition jobs, it is virtually
impossible to install enclosures, ventilators or similar engineering controls to minimize the
employee exposure. The furnace is demolished by specialized, skilled personnel. Owens
Corning’s employees may be in the area performing related tasks. All refractory is removed to
minimize potential damage to the refractory bricks. The refractory is then segregated and stored
in closed containers. The used refractory is sent to a recycler. The demolition operation typically
lasts for two weeks. The refractory removal is completed within a week. Appropriate PPE are
worn during the demolition process, including respiratory protection.
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Bushing Change Operation
It is extremely difficult to employ effective local dust collection during the replacement of a
bushing because the working space is very crowded. Each bushing is a plate approximately 8
inches by 4 inches and the bushings are set 1 – 2 feet apart. There are numerous bushings
attached to each fore hearth. The space is further crowded as a result of the presence of electrical
connections and cooling water loops.
Possible Replacement of the Chrome Containing Refractory
Owens Corning has tried to identify potential replacements for chrome containing refractory.
Considering the operating conditions and highly corrosive nature of molten glass, we have been
unable to do so. All replacement refactories, including zircon, greatly reduce the life of the
furnace and result in significant cost penalties to Owens Corning.
In the U.S., Owens Corning operates 6 continuous strand glass furnaces, at 3 different plants all
of which could be impacted by the proposed Rule. These are some of the largest continuous
strand glass furnaces in the world.
The current operating life of one of these furnaces is approximately 12 years. Replacing the
dense chrome refractory with an alternate material, like a zircon, would reduce furnace life by 35
to 50% and reduce Conversion Efficiency (CE) between 2 and 3%, primarily as a result of
increased stoning.
In Conclusion
Owens Corning requests that OSHA include furnace rebuilds under the construction standard.
When the furnace, channels and fore hearths are being rebuilt there is no industrial activity
taking place in that part of the plant. The only activities involve the demolition and construction
of the new equipment. Contractors hired by Owens Corning to do the demolition and rebuild will
be covered by the construction standard. Owens Corning‘s employees, working in the same area,
will otherwise have to comply with the general industry standard. The application of the two
standards, with their different requirements, to the same immediate working area will create
confusion and conflict.
Owens Corning requests that OSHA modify the compliance deadline for the installation of
engineering control devices in recognition of the potential need for manufacturers to obtain
environmental permits to undertake the required modifications. There is a significant likelihood
that the normal delays associated with obtaining those permits will make it impossible for Owens
Corning to implement any required changes within the time permitted by the proposed rule.
Additionally, the timing requirements must also take into consideration the rebuild schedules for
some of the equipment employed in this industry and the ability to turn off some of this
equipment. It is entirely possible that some engineering controls, if needed, could only be
installed when the furnace was shut down.
Finally, Owens Corning supports NAIMA’s position on the applicable PEL for Hexavalent
Chrome and joins NAIMA in requesting that OSHA establish a PEL similar to that
recommended by the ACGIH and most major U.S. trading partners.
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CULTURED STONE
Owens Corning agrees with the positions expressed by the Portland Cement Association (PCA),
the American Concrete Pipe Association (ACPA), the National Concrete Masonry Association
(NCMA) and the Colorado Ready Mix Concrete Association (CRMCA) in the comments they
submitted earlier in this proceeding. The purpose of this testimony is to supplement Owens
Corning’s earlier comments and support the recommendation by those trade groups that OSHA
exclude Portland cement from the general industry standard of the proposed rule as it has
proposed to do in the construction standard.
Cultured Stone’s Manufacturing Process
Owens Corning’s, Cultured Stone Division manufactures stone and brick veneer used in
residential and commercial construction. The Cultured Stone product line includes hundreds of
pre-cast stone veneers and architectural trim products that replicate an extensive variety of
textures, sizes, shapes and colors of natural stone. Cultured Stone products are cast in molds
taken from carefully-selected natural stone.
Cultured Stone products are produced at three manufacturing plants in the U.S. The primary
materials used to manufacture the stone and brick veneers are Portland cement, fly ash,
aggregates, sand and water. The Portland cement arrives at the plants in closed tanker trucks. It is
pneumatically offloaded into enclosed storage silos. The production process begins by weighing
aggregates and sand in weight hoppers and transferring them to the batch mixer. Water is
immediately added to the batch mixer which reduces or eliminates further airborne dust. The
appropriate proportions of Portland cement and fly ash are acquired through enclosed cement
weigh hoppers that utilize dust collection systems and are pneumatically conveyed through a
dense phase piping system into a secondary enclosed collection hopper. The Portland cement and
fly ash constituents are then introduced into the aggregate and water slurry in the concrete batch
mixer. Additional water, coloring agents and admixtures are then added to the mixer to produce
the desired batch. The wet batch material is fed to the pouring station and the required quantity
of batch is placed into a mold that has been prepared by applying the appropriate coloring to the
surface of the mold. The newly formed stone and brick veneers are allowed to cure in the mold.
When sufficiently cured, they are removed and no further finishing is required. The stone and
brick veneers are then packaged and shipped to customers. The attached flow chart depicts this
production process.
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Flow Chart Showing Production Process for Cultured Stone
Raw Materials Suppliers
Aggregates Cement
Water Admixtures Color
&Sand &FlyAsh
Wet Color
MIxer Station
Coloring
MOLD Pouring
Curing Molds
Molds
Empty
Mold
MOLD
Demolding Stones into
Racks Dryer
Packaging
Repack
Distribution Center Cure time
& Dealers & FG Inventory
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Sources of Hexavalent Chromium
The apparent source of hexavalent chromium in Cultured Stone’s manufacturing process is the
cement. The Portland Cement Association characterized the amount of hexavalent chromium
typically reported in Portland cement at page 2 of its comments on the proposed rule, dated
December 23, 2004. The PCA stated in pertinent part:
…This study concludes that the water soluble hexavalent chromium content in Portland
cement manufactured in the United States and Canada ranges from zero to seven parts per
million. Another study cited in the German table puts U.S. cement concentrations at zero to
5.2 ppm. This number has declined in recent years as fewer cement plants utilize refractory
materials and grinding balls containing chromium in the production process.
The batch used by Cultured Stone, to produce these stone and brick veneers, consist of
approximately 8 – 8.5 % Portland cement. As was pointed out in comments already received by
OSHA, the effect of the batch mixing is to reduce the already low levels of hexavalent chromium
even further.
Owens Corning has discussed, with its current Portland cement suppliers, the amount of
hexavalent chrome present in the material they provide. They have indicated that they no longer
use any processing equipment, such as grinding balls, that contains Hexavalent Chromium.
Owens Corning intends to discuss with its suppliers, modifying its product specifications to
specifically prohibit the use of such processing equipment.
Exposures to Hexavalent Chromium
A limited number of industrial hygiene samples, measuring exposures to hexavalent chromium
have been taken at Cultured Stones manufacturing facilities. In each case the level of Hexavalent
Chromium was less than the detection limit of the test (0.5 ug/m3). Because the measured levels
were so low, in comparison to the existing Permissible Exposure Level (PEL) for Hexavalent
Chromium, Cultured Stone has not conducted additional sampling as part of its regularly
scheduled workplace exposure assessments.
In Conclusion
Owens Corning requests that OSHA extend its proposal for excluding Portland cement from the
construction standard to the general industry standard.
Thank You
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