SUPERVISORY-GAS-ADJUSTED FRICTION-LOSS COEFFICIENT BASED FIRE SUPPRESSION SPRINKLER SYSTEM

Abstract

A supervisory-fluid-adjusted friction-loss coefficient based fire suppression sprinkler system has an array of pipes in fluid communication with an arrangement of sprinklers. A supervisory fluid sub-assembly is fluid communication with the array of pipes. The supervisory fluid sub-assembly provides a supervisory fluid other than air to the array. A diameter of each respective pipe of the array is determined by a friction-loss formula having a friction-loss coefficient representing a metric corresponding to a corrosion-induced internal surface roughness of each respective pipe of the array The friction-loss coefficient is determined by empirical testing of a representative pipe of the array in accordance with a nationally recognized testing procedure.

Claims

1. A supervisory-fluid-adjusted friction-loss coefficient based fire suppression sprinkler system comprising: an array of pipes in fluid communication with an arrangement of sprinklers; and a supervisory fluid sub-assembly in fluid communication with the array of pipes, the supervisory fluid sub-assembly providing a supervisory fluid other than air to the array, wherein a diameter of each respective pipe of the array is determined by a friction-loss formula having a friction-loss coefficient representing a metric corresponding to a corrosion-induced internal surface roughness of each respective pipe of the array, the friction-loss coefficient determined by empirical testing of a representative pipe of the array in accordance with a nationally recognized testing procedure.

2. The fire suppression sprinkler system according to claim 1, wherein the friction-loss formula is a Hazen-Williams formula modified to account for a coefficient of friction of the representative pipe of the array when a fluid other than air is the supervisory fluid, the modified Hazen-Williams formula providing, $p=\frac{4.52.Math.Q^{1.85.Math.}}{{\left(C+\right)}^{1.85}.Math.D^{4.87}}$ where =frictional resistance (psi/ft of pipe), Q=flow (gpm), C=coefficient of friction for air as the supervisory gas D=actual internal diameter of pipe (in.), and where is a constant representing a difference in a coefficient of friction for an aged pipe for which air is a supervisory fluid and a coefficient of friction for an aged pipe for which a fluid other than air is the supervisory fluid.

3. The fire suppression sprinkler system according to claim 2, wherein the supervisory fluid is nitrogen.

4. The fire suppression sprinkler system according to claim 3, wherein is at least about 10.

5. The fire suppression sprinkler system according to claim 3, wherein is twenty or more.

6. The fire suppression sprinkler system according to claim 3, wherein is about thirty to forty-five.

7. The fire suppression sprinkler system according to claim 3, wherein is at least up to sixty but no more than seventy.

8. The fire suppression sprinkler system according to claim 1, wherein the friction-loss formula is a Darcy-Weisback formula modified to account for a coefficient of friction of the representative pipe of the array when a fluid other than air is the supervisory fluid, the modified Darcy-Weisback formula providing, $.Math..Math.P=0.000216.Math.\left(f-\right).Math..Math.\frac{l.Math..Math..Math..Math.Q^2}{d^3},$ where =friction loss (psi), f=friction loss factor from Moody diagram, l=length of pipe (ft), =density of fluid (lb/ft.sup.3), Q=flow in pipe (gpm), d=inside diameter of pipe (in.),and where is a constant representing a difference in a coefficient of friction of an aged pipe for which air is a supervisory fluid and a coefficient of friction of an aged pipe for which a fluid other than air is the supervisory fluid.

9. The fire suppression sprinkler system according to claim 8, wherein the supervisory fluid is nitrogen.

10. The fire suppression sprinkler system according to claim 8, wherein is at least about 10.

11. The fire suppression sprinkler system according to claim 8, wherein is twenty or more.

12. The fire suppression sprinkler system according to claim 8, wherein is about thirty to forty-five.

13. The fire suppression sprinkler system according to claim 8, wherein is at least up to sixty but no more than seventy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The following detailed description of preferred embodiments of the invention will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

[0038] FIG. 1 is schematic of a prior art fire sprinkler system piping layout for a Tree type dry pipe system having a C-factor of 100;

[0039] FIG. 2 is schematic of a prior art fire sprinkler system piping layout for a Tree type dry pipe system identical to the system of FIG. 1 with the exception that the C-factor is 140; and

[0040] FIG. 3 is a schematic diagram of a prior art Potter INS-2000 nitrogen generation sub-assembly.

DESCRIPTION OF THE DISCLOSURE

[0041] Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0042] As used in the description of the invention and the appended claims, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. The words and/or as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The words comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0043] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, the description of a range such as from 1 to 10 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 10, from 3 to 10 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, 7, 8, 9, and 10. This applies regardless of the breadth of the range.

[0044] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases ranging/ranges between a first indicate number and a second indicate number and ranging/ranges from a first indicate number to a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0045] Referring to the drawings in detail, wherein like numerals indicate like elements throughout, there is shown in FIGS. 1 and 2 two examples of a prior art fire sprinkler system piping layout. The two fire sprinkler system piping layouts are identical Tree type dry pipe systems. The pipe sizes are the same for both examples. The only difference in the two systems is the C-Factor of the piping. The difference in C-Factor value is presumed to be due to the hypothesis that the system in FIG. 1 uses air as the supervisory fluid and the system in FIG. 2 uses nitrogen as the supervisory fluid and accordingly, the internal surface roughness of the pipe in the FIG. 1 system is greater than the internal surface roughness of the pipe in the FIG. 2 system.

[0046] Presently, Underwriters Laboratories (UL) is conducting under applicant's direction a study simulating a nitrogen filled dry pipe system after 50 years of use. In view of data from industries other than the fire sprinkler system industry using nitrogen to mitigate metal pipe corrosion, applicant believes the UL study will conclude that the difference in C-Factor will be in the range of 20-50 greater for the nitrogen system).

[0047] The system piping in FIG. 1 utilizes a C-Factor of 100. This is the typical required C-Factor within NFPA 13 for dry pipe systems utilizing steel pipe. The system piping in FIG. 2 utilizes a C-Factor of 140. A standard Hydraulic Design Area of 2000 square feet is utilized for the calculations. The systems are both calculated discharging a density of 0.60 gpm/sq. ft. The hydraulic calculation program used is the Tyco Fire Protection Products SprinkCalc III; Program Version 3.2.22.272.

[0048] With a C-Factor of 100, the system demand at the point of connection to the source for the system piping in FIG. 1 is 111.9 psi at a 1,297 gpm flow rate. Conversely, when the C-Factor is increased to 140, the ensuing system demand at the source system piping in FIG. 2 is 81.3 psi at a 1,255 gpm flow rate. The increase in C-Factor saved 30.6 psi. This pressure savings may now be used to the designers benefit as stated above.

[0049] Although the foregoing examples are for a Tree type dry pipe fire sprinkler system using black raw steel pipe, internally galvanized pipe may be used instead. Initially thought to mitigate corrosion, internally galvanized pipe was assigned a C-Factor of 120 in NFPA 13; however, sampling over time showed that the galvanized pipe with compressed air deteriorated dramatically. As a result, NFPA 13 reduced the C-factor back to 100, the same C-Factor as black steel pipe.

[0050] Nitrogen as a supervisory gas may be used to mitigate corrosion not only in dry pipe systems but also in wet pipe systems where nitrogen may replace trapped oxygen. For example, the trapped oxygen by a process referred to as wet interting in which a wet pipe system is pre-filled with nitrogen before filling with water.

[0051] Broadly stated, a preferred embodiment of the present invention is a supervisory-gas-adjusted friction-loss-coefficient based fire suppression sprinkler system comprising an array of pipes in fluid communication with an arrangement of sprinklers. A supervisory fluid sub-assembly is in fluid communication with the array of pipes and provides a supervisory fluid other than air to the array. A diameter of each respective pipe of the array is determined by a friction-loss formula having a friction-loss coefficient representing a metric corresponding to a corrosion-induced internal surface roughness of each respective pipe of the array. The friction-loss coefficient is determined by empirical testing of a representative pipe of the array in accordance with a nationally recognized testing procedure. One representative example of a nationally recognized testing procedure may be found in Chapter 9, Friction Loss Along A Pipe, Frederick Institute of Technology Online Course, Jun. 9, 2010, the contents of which are incorporated in the entirety herein by reference.

[0052] Another preferred embodiment of the present invention is a supervisory-gas-adjusted friction-loss-coefficient based fire suppression sprinkler system comprising an array of pipes in fluid communication with an arrangement of sprinklers, such as the Tree type dry pipe systems shown in FIGS. 1 and 2.

[0053] A diameter of each respective pipe of the array is determined by a modified Hazen-Williams formula providing,

[00005]$p=\frac{4.52.Math.Q^{1.85.Math.}}{{\left(C+\right)}^{1.85}.Math.D^{4.87}}$ [0054] where =frictional resistance (psi/ft of pipe), [0055] Q=flow (gpm), [0056] C=coefficient of friction for air as the supervisory gas, [0057] D=actual internal diameter of pipe (in.), and
where the Greek symbol is a constant representing the difference in the coefficient of friction of a pipe for which air is a supervisory fluid, such as the piping in the system in FIG. 1 having a C-Factor of 100, and the coefficient of friction of a pipe for which a fluid other than air is a supervisory fluid, such as the piping in the system in FIG. 2 having a C-Factor of 140, as determined by empirical testing of representative pipes of the array in accordance with nationally recognized testing procedures.

[0058] Preferably, the supervisory fluid is nitrogen. Suggestedly, is at least about 10; desireably is twenty or more; preferably is about thirty to forty-five; and less preferably, is at least up to sixty but no more than seventy.

[0059] A supervisory gas sub-assembly (see, FIG. 3) is in fluid communication with the array of pipes. The supervisory gas sub-assembly provides a supervisory gas to the array. Preferably, the supervisory gas sub-assembly is a nitrogen generator, such as the Potter INS-2000 nitrogen generator (see, Potter INS-1500/2000 Nitrogen Generators Installation, Operation, and Instruction Manual Number 5403646, Rev B, 2/18, the contents of which are incorporated in the entirety herein by reference) and comprises an air compressor and air storage tank, a nitrogen cabinet housing a nitrogen membrane that separates nitrogen from oxygen and other gases in the air and a nitrogen storage tank connected. The supervisory gas sub-assembly is connected to the array of pipes by an air maintenance device, (see, Globe Model H-1 Air Maintenance Device, Glone Fire Sprinkler Sorp. Brochure GFV-545 June, 2017).

[0060] Another preferred embodiment of the present invention is a supervisory-gas-adjusted friction-loss-coefficient based fire suppression sprinkler system comprising an array of pipes in fluid communication with an arrangement of sprinklers, such as the Tree type dry pipe systems shown in FIGS. 1 and 2.

[0061] A diameter of each respective pipe of the array is determined by a modified Darcy-Weisback formula modified to account for a coefficient of friction of the representative pipe of the array when a fluid other than air is the supervisory fluid, the modified Darcy-Weisback formula providing,

[00006]$.Math..Math.P=0.000216.Math.\left(f-\right).Math..Math.\frac{l.Math..Math..Math..Math.Q^2}{d^3},$ [0062] where =friction loss (psi), [0063] f=friction loss factor from Moody diagram, [0064] l=length of pipe (ft), [0065] =density of fluid (lb/ft.sup.3), [0066] Q=flow in pipe (gpm), [0067] d=inside diameter of pipe (in.),and
where is a constant representing a difference in a friction loss factor for an aged pipe for which air is a supervisory fluid and a friction loss factor for an aged pipe for which a fluid other than air is the supervisory fluid as determined by empirical testing of representative pipes of the array in accordance with nationally recognized testing procedures.

[0068] Preferably, the supervisory fluid is nitrogen. Suggestedly, is at least about 10; desireably is twenty or more; preferably is about thirty to forty-five; and less preferably, is at least up to sixty but no more than seventy.

[0069] Those skilled in the art of fire sprinkler system design will appreciate that the constant in the modified Hazen-Williams formula and the modified Darcy-Weisback formula can have a range of values depending on the type and size of the pipe, the initial internal surface roughness and the degradation of the surface due, in part, to corrosion depending of the supervisory fluid used. Further, those skilled in the art will appreciate that the C-Factors for the Hazen-Williams formula and -factors Darcy-Weisback formula in the currently approved standards documents are empirically determined by test procedures that do not take into account the use of different supervisory fluids and must be adjusted.

[0070] Still further, it will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that the invention is not limited to the particular embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the disclosure.

[0071] All references, patent applications, and patents mentioned in the foregoing disclosure are incorporated herein by reference in their entirety.