REFRACTORY MATERIAL WITH STAINLESS STEEL AND ORGANIC FIBERS

CROSS-REFERENCE TO RELATED APPLICATION

The present Application claims priority from United States provisional patent application 60/773,055, filed February 15, 2006, entitled "Removable Fire Walls," the contents of which are incorporated herein by reference in their entirety.

HELD OF THE INVENTION

This invention relates generally to refractory materials and large fire walls made from such refractory materials.

BACKGROUND OF THE INVENTION

Large fire walls, such as fire walls capable of providing protection against fires in oil refineries and large electrical transformers are traditionally made from ordinary concrete. The problem with fire walls constructed from ordinary concrete is that they must be extremely thick to adequately withstand the high temperatures created from large hydrocarbon pool fires with long durations (typically 2000 ⁰ F and lasting six hours or more).

Accordingly, there is a need for new materials from which large fire walls can be created which provide sufficient protection against large, very long-lasting and hot fires without requiring excessive thickness to simultaneously meet severe mechanical requirements.

SUMMARY

The invention satisfies this need. The invention is a refractory composition comprising a cement, a binder and a matrix material, wherein the matrix material comprises both stainless steel fibers and organic fibers. The refractory can be easily cast, without

additional steel reinforcement, into large fire wall panels capable of meeting the requirements of testing conducted in accordance with ASTM E- 119, Standard Test Methods for Fire Tests of Building Construction and Materials in support of IEEE Std. 979-1994, Guide for Substation Fire Protection. The fire wall assembly withstood the fire endurance test without passage of flame and gases hot enough to ignite cotton waste during a four-hour fire exposure. The assembly also withstood a 45 psi water stream for five minutes immediately following the four-hour fire exposure period. This is a stringent mechanical requirement, as all fire walls must maintain their integrity before, during and after a fire, per the Universal Building Code's definition of a true fire wall.

DRAWINGS

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description, appended claims and accompanying drawings where:

Figure 1 is a side view of a fire wall having features of the invention;

Figure 2 is a perspective view of a partially completed fire wall having features of the invention; Figure 2 A is a cross-sectional view of a vertical beam from Figure 1, showing the insertion of two walls disposed on opposite sides of the vertical beam;

Figure 2B is a first alternative cross-sectional view of a vertical beam, showing the insertion of two walls disposed at right angles with one another;

Figure 2C is a second alternative cross-sectional view of a vertical beam, showing the insertion of three walls into the vertical beam;

Figure 2D is a third alternative cross-sectional view of a vertical beam, showing the insertion of four walls into the vertical beam;

Figure 3 is a detail plan view of a vertical beam useable in the invention;

Figure 4 is a side view showing rebar reinforcement disposed within the vertical beam illustrated in Figure 3 ;

Figure 5 is a front view showing rebar reinforcement disposed within the vertical beam illustrated in Figure 3 ;

Figure 6 is a rebar tying diagram for rebar reinforcement useable in a vertical beam within the invention;

Figure 7 is a plan view of a vertical beam useable in the invention showing the vertical beam's attachment to a base plate; Figure 8 is a cross-sectional view of the vertical beam illustrated in Figure 7, taken along line 8-8;

Figure 9 is a cross-sectional view of the vertical beam illustrated in Figure 8, taken along line 9-9;

Figure 10 is a detail view of the attachment of the base plate to rebar reinforcement within the vertical beam illustrated in Figure 8;

Figure 11 is a front view illustrating the installation of a vertical beam useable in the invention to a foundation;

Figure 12 is a side view illustrating the installation of the vertical beam illustrated in Figure 11 ; Figure 13 is a plan view of the vertical beam showing an enclosure for the protection of its base plate;

Figure 14 is a cross-sectional view of the vertical beam illustrated in Figure 13 taken along line 14-14;

Figure 15 is a side view of the vertical beam illustrated in Figure 13; Figure 16 is a second plan view of a vertical beam having a base plate protected by a protective enclosure;

Figure 17 is a cross-sectional view of the vertical beam illustrated in Figure 16 taken along line 17-17;

Figure 18 is a front view of the vertical beam illustrated in Figures 13 and 16; Figure 19 is a rear view of the vertical beam illustrated in Figure 13; and

Figure 20 is a side view of a stainless steel fiber useable in the invention.

DETAILED DESCRIPTION

The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well.

The invention is a refractory comprising a cement, a binder, water and a matrix material. The matrix material comprises both stainless steel fibers and organic fibers.

The cement can be any suitable cement, such as Portland cement. The binder can be any suitable binder, such as calcium silicate or aluminum silicate.

Where the refractory comprises calcium silicate and Portland cement, the water content is typically between about 10% and about 15% of the combined weight of the calcium silicate, Portland cement and water, more typically between about 11% and about 12%.

In addition to stainless steel fibers and organic fibers, the matrix typically comprises a variety of other mineral fillers. A typical premix of cement, binder and the non- stainless steel and non-organic portion of the matrix contains 40% to 60% (by weight) aluminum oxide, 0% to 20% (by weight) aluminum silicate, up to 30% cement, smaller amounts of crestobalite silica and quartz silica, and water.

An exemplar of such typical premix contains 44.5% (by weight) silicon dioxide, 34.1% (by weight) aluminum oxide, 16.5% (by weight) calcium oxide, 1.8% (by weight) ferric oxide and 13% water. This exemplar premix is capable of forming a concrete having the following typical characteristics:

Permanent Linear Change %

After heating to:

110 ⁰ C (230 ⁰ F) -0. 10

425 °C (800°F) -0. 15

650 ⁰ C (1200°F) -0. 30

Density pcf

After heating to:

110 ⁰ C (230 ⁰ F) 2.12 2120 132 425 °C (800°F) 2.10 2100 131

650 ⁰ C (1200°F) 2.08 2080 130

Modulus of Rupture MPa kg/cm ² psi

As cured: 8.00 81.58 1160 After heating to:

110 ⁰ C (230°F) 8.62 87.91 1250 425 °C (800 ⁰ F) 6.55 66.81 950 650°C (1200°F) 4.48 45.71 650

Cold Crushing Strength MPa kg/cm ² psi

As cured:

1 day 31.0 316.46 4500 3 days 37.9 386.78 5500 7 days 39.3 400.84 5700 28 days 50.0 499.30 7100

Thermal Conductivity W/m°K BTU4n/hr*ft ² *°F

(Hot Wire Method ASTM C- 1113) After heating to: 100 ⁰ C (210 ⁰ F) 1.17 8.11

250°C (480°F) 1.15 7.97

450 ⁰ C (840 °F) 1.26 8.74

600 ⁰ C (I IlO ⁰ F) 1.27 8.81

Coefficient of Thermal Expansion

From ll0°F-1600°F 3.75 x 10V ⁰ F

From 38°C-871 °C 6.72 x 10V ⁰ C

In the matrix, stainless steel is used instead of ordinary steel because of stainless steel's higher temperature resistance, higher strength, non-corrosion characteristics and nonmagnetic properties.

The stainless steel fibers can be 304 type stainless steel fibers. Other types of stainless steel from the 300 Series can also be used to make the fibers, such as: 301, 302, 303, 309, 316, 321 and 347. Typically, the weight percentage of the stainless steel fibers within the dry refractory mix (before water is added) is between about 1.2% and about 1.6% (by weight) of the dry refractory mix.

The stainless steel fibers are preferably corrugated to increase the effective surface area of the fibers and to facilitate their bonding and attachment within the matrix. In one embodiment of the invention, the stainless steel fibers each have a length of about one inch, a width of about 0.045 inch and a thickness of about 0.02 inches. These exemplary stainless steel fibers are corrugated such as the stainless steel fiber 2 illustrated in Figure 20. Each stainless steel particle 2 has a base section 4 having a length of about 0.18 inch, followed by nine alternating positive and negative corrugations 6. Each corrugation 6 has a height h of about 0.0075 inch and a length 1 of about 0.08 inch long. After the series of nine corrugations, the particle terminates with a second, oppositely disposed base section 8 having a length of about 0.1 inch. Such stainless steel fibers can be purchased from Fibercon International of Evans City, Pennsylvania.

The organic fibers are important in the refractory to provide minute channels (upon melting during a fire) to facilitate gas venting without fracturing the refractory. These fibers also mitigate crack formation during curing.

The organic fibers can comprise polypropylene fibers, preferably in excess of 90% polypropylene fibers. Typically, at least about 90% of the organic fibers have a length between about 0.2 inch and about 0.3 inch and a diameter between about 0.001 inch and about 0.002 inch.

The organic fibers are typically about 1% by weight of the dry refractory mix. The fibers have a variety of shapes and are not necessarily linear. The length of each of the organic fibers is most typically 0.25 inches. Typically, the fibers have a relatively constant circular cross-section with a diameter between about 0.001 and about 0.004 inches. In a typical embodiment of the invention, smaller diameter organic fibers greatly outnumber larger diameter organic fibers, for example by at least a ratio of 50:1. Such organic fibers can be purchased from Allied Mineral of Columbus, Ohio.

Both the stainless steel fibers and the organic fibers are randomly oriented within the refractory.

Refractory panels 10 can be conveniently cast from the refractory of the invention. Cure time for even very large panels 10 is as little as 12 hours at ambient temperatures. Kiln drying is not required.

A typical refractory of the invention has the following characteristics:

1. Mechanical properties at ambient temperature: a. Specific gravity: 134 pcf b. Modulus of elasticity, E, ksi:

2,500 - 5,000 Unreinforced (UR); 15,000 - 25,000 Steel Reinforced (SR) c. Shear Strength, F _v , ksi (reported as Modulus of Rupture for ceramics and refractories): 1.1 (UR);

14.4 (SR) d. Bending Strength F _b , ksi: Not applicable for UR matrix; 34.8 (SR) e. Tension and compress strength, F _t and Fc ksi:

5.25 (UR - compression; F _t < 290 psi, hence not usually used for characterizing inelastic materials); 52 tension and 48 compression (SR)

2. Electrical conductivity and other electrical properties (UR):

Dielectric strength = 90 v/mil; Dielectric constant about 5; Resistivity = 52 x 10 ¹⁰ ohm-cm

3. Thermal properties:

a. Thermal conductivity (Hot Wire Method ASTM C- 1113)

After heating to Btu-in/hr-ft ² -°F

400 ⁰ F 4.20

8000 ⁰ F 4.41

1200 °F 4.69

1825 ⁰ F 4.90

b. Thermal expansion coefficient

From 100 ⁰ F to 2000°F 3.75 x 10 ^"6 / °F From 38 ⁰ C to 1093 ⁰ C 6.72 x 10 ^"6 / ⁰ C

c. Fire rating requirement

1,205 ⁰ C working temperature

d. Mechanical strength at high temperatures:

Modulus of Rupture (unreinforced) MPa kg/cm ² psi

As cured:

7.58 77.36 1100

After heating to:

110°C (230°F) 8.27 84.39 1200

540 ⁰ C (1000 ⁰ F) 4.48 45.71 650

1205 °C (2200°F) 7.58 77.36 1100

Cold Crushing Strength (unreinforced) MPa kg/cm ² psi

As cured:

1 day 36.20 369.2 5250 3 days 39.92 407.2 5790

7 days 39.78 405.8 5770

28 days 39.30 400.0 5700

After heating to: 110 ⁰ C (230 ⁰ F) 38.61 393.8 5600

540°C (1000°F) 29.17 297.5 4230

1205 °C (2200°F) 38.27 390.3 5550

The refractory composition of the invention can be conveniently cast into an infinite variety of shapes. For example, the refractory composition of the invention can be cast into large panels 10 suitable for use in constructing a high temperature fire walls. Such large panels 10 are typically between about 5 feet and about 10 feet in length, between about 2 feet and about 5 feet in width and between about 1 inch and about 3 inches in thickness. Such panels 10 typically weigh between about 400 pounds and about 800 pounds.

The refractory of the invention can be conveniently mixed within an ordinary cement mixer. After adequate mixing of all of the ingredients, the wet mixture can then be poured into molds. The molds are preferably gently vibrated to eliminate air pockets and to evenly distribute the stainless steel fibers.

Surprisingly, even such large panels 10 do not require additional steel

reinforcement within the panel, such as steel frameworks and rebar cages. In fact, the use of such additional steel reinforcement has been found in many cases to be detrimental to the integrity of the panel 10 when subjected to high heat followed by a rapid cool down. Cracking can occur during cool down of panels 10 having additional steel reinforcement due to the disparity in coefficients of expansion between the additional steel reinforcement and the refractory composition.

Fire walls 16 made with such large panels 10 can comprise a plurality of panels 10 disposed between vertical beams 12, such as illustrated in Figures 1 and 2. Both the panels 10 and the vertical beams 12 can be cast from the refractory of the invention.

The vertical beams 12 weigh typically in excess of 5000 pounds. Each vertical beam 12 preferably comprises a slot 14 into which a plurality of panels 10 can be stacked one on top of the other to form fire walls 16 of various shapes (see Figures 2A-2B and 3).

Unlike panels 10 cast from the refractory of the invention, vertical beams 12 cast from the refractory are typically reinforced with rebar cages 18 in the same manner as ordinary concrete beams are reinforced with rebar cages (see Figures 4, 5, 6, 8 and 9).

The vertical beams 12 typically are attached to a traditional concrete foundation

20 using a base plate 22 which is welded to steel reinforcement bars 24 disposed within the vertical beams 12 (see Figure 10). The base plate 22 is made of steel and attached to the foundation using steel bolts 26, and so must be protected in the event of a fire. Such protection can be provided by installing a base plate cover 28 made from the refractory of the invention around each of the base plates 22 (see Figures 13-17).

Alternatively, the vertical beams 12 can be standard I beams or H beams (not shown) which have been clad with the refractory of the invention.

An optional door (not shown) can be created within the fire wall 16. Such a door can be used for access by maintenance personnel. The door can be made of short panels of the present refractory and can be made to slide into a door frame. Typically, the door is located

next to a vertical beam 12 with hinges for the door attached to the beam 12.

Such modular fire walls 16 provide easy assembly and disassembly at the site and are completely removable. The modular characteristics of the fire wall 16 simplify specification, assembly and disassembly, and minimize manufacturing and insulation costs without compromising thermal or mechanical performance.

Large fire walls 16 of the invention have been found to comply with the standards for a four-hour rating under ASTM E- 119 as previously stated.

The refractory of the invention provides many advantages over most refractories of the prior art. The invention provides a high-strength refractory having excellent fire resistance. Expansion and contraction between temperatures below freezing and temperatures in excess of 900 ⁰ C are relatively small. The refractory is corrosion, mold, rot and infestation resistance. It is impermeable to moisture, to air and to other gases. Cracking during curing is minimal, as is cracking during initial temperature increases (up to about 150 ⁰ C) and when subject to high temperatures (temperatures higher than 150 ⁰ C). The refractory has the built-in ability to relieve trapped gases at medium and high temperatures. The refractory can be fully cured at ambient temperature and pressure.

Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the present invention.