DESC:TECHNICAL FIELD
[0001] The present disclosure pertains generally to technical field of pressurized gas cylinders. Specifically it pertains to O-rings for LPG cylinders and self closing valve assemblies using these O-rings.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Liquefied Petroleum Gas (LPG) is a by-product of the oil industry and over the years, it has emerged as one of the preferred sources of energy for household and commercial use because of its ease of storage, transportation, relatively large availability and low cost. LPG has many other applications but because of its global availability, environmental benefits and transportation flexibility has become most preferred and sought after cooking fuel. LPG for domestic and commercial applications is stored and supplied in cylinders. However, because of its inherent properties, LPG is a potential explosive and if not handled correctly can be the cause for major damage. Therefore, it is imperative that all users and handlers of LPG understand the potentially dangerous nature of LPG and handle/use it in safe and correct manner. It also become imperative for producers and suppliers of LPG to design systems and methods whereby safety during handling, transportation and use of LPG can be guaranteed and ensured at all times. Because of this, producers and suppliers of LPG, strive to constantly work, evaluate and improve on the existing safety features.
[0004] LPG cylinder essentially consists of a steel/metal cylinder and a self closing valve (SC Valve) assembly. LPG is stored under pressure in the LPG cylinder and SC Valve assembly is used during filling of LPG, during filling of LPG gas, containing the LPG safely inside cylinder during storage, transportation and supply of LPG during use. In addition, LPG cylinder is closed with a tamper proof seal during storage and transportation. LPG is withdrawn from the LPG cylinder by coupling with a domestic pressure regulator (DPR).
[0005] Safeties are incorporated in LPG cylinder through SC Valve. SC valve ensures that there is no leakage of pressurized LPG gas from the cylinder during transportation, storage and during usage. Leakage protection is ensured through ‘O’ rings, gasket and spindle assembly (FIG. 1 – prior art). The spindle (106) and gasket (104) of SC valve ensures that the pressurized LPG is contained in LPG cylinder, and allows the pressurized LPG to flow from the LPG cylinder through SC valve/ around spindle (106) and gasket (104) assembly when required to do so. Gasket (104) along with spindle (106) rests against the valve body (102) because of the force exerted by spring assembly (108) of SC valve. The sealing action can be provided by ensuring proper seating of spindle gasket against valve body. Pressing of spindle (106) against the spring (108) force creates a gap between gasket (104) and valve body (102) that allows the LPG to flow from LPG cylinder to burner. O-ring (110) seals the space between domestic pressure regulator and SC valve that is filled with LPG withdrawn from the cylinder, as shown in FIG. 3. This O-Ring 302 acts as a secondary sealing and prevents leakage of LPG to the atmosphere when the DPR connected to the SC Valve is turned ON.
[0006] Any failure of O-ring (110) can cause for leakage of LPG into the atmosphere and lead to a potentially dangerous situation. However, this component is prone to failure primarily due to chemical (LPG) degradation, compression set and abrasion, thereby resulting in leakages.
[0007] Existing O-ring for SC Valve are made from Nitrile butadiene rubber (NBR) or nitrile rubber that has good resistance to oil, fuel, and other chemicals. Resistivity to oil, etc. increases with increase of nitrile but it also makes the component more and more rigid. Therefore, there is a constant endeavor to find better materials that can retain flexibility while retaining the resistivity to hydrocarbons.
[0008] The existing material used for the SC Valve O-Rings is Nitrile Butadiene Rubber (NBR), which though presently being used for this application, does not have very good properties with respect to abrasion resistance, which is indicative of reduced impact bearing property of the component due to which the components suffers mechanical wear thereby leading to leak due to the damage, resistance to hydrocarbons (which is indicative of the chemical degradation property when subjected to LPG environment), permeability (which is the measure of the ability of the material to allow diffusion of gases through it) and lastly, the compression set property that is indicative of the loss of ability of rubber to retain its elastic properties after prolonged action of compression stress.
[0009] With discovery of newer materials and by incorporating newer designs, there is further scope for improving the existing safety related to use of LPG.
[0010] There is therefore a need in the art to design and develop O-Ring of SC Valveby which existing shortcomings and disadvantages can be overcome and safety related to use of LPG can be further enhanced.
[0011] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0012] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0013] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0014] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0015] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

OBJECTS OF THE INVENTION
[0016] It is an object of the present disclosure to provide improved O-ring for SC valve of LPG cylinder.
[0017] Yet another object of the present disclosure is to provide an O-ringfor SC valve of LPG cylinder that has enhanced flexibility while retaining its resistance to hydrocarbons.
[0018] Yet another object of the present disclosure is to provide an O-ring for SC valve that possesses increased compression set property leading to increased safety in usage of LPG.
[0019] Yet another object of the present disclosure is to provide an O-ring for SC valve with increased abrasion resistance property that leads to improved performance of the valve and thus increases its life.
[0020] Yet another object of the present disclosure is to provide an O-ring with increased resistance to hydrocarbons resulting in reduced SC valve leaks.

SUMMARY
[0021] As set forth in the detailed description, in accordance with various embodiments of the present disclosure, safety device for LPG cylinder and specifically pertains to self closing (SC) valve assembly and self closing (SC) valve assemblies using these devices are provided. An embodiment of the present invention provides O-rings of SC valve of LPG cylinder, wherein O-rings can be made of FKM material. O-ring according to the embodiments of the present invention can be of the FKM material having preferably but not necessarily hardness value of 65 +5/-4 International Rubber Hardness Degree (IRHD).
[0022] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components

BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0024] FIG. 1 (Prior art) illustrates sectional view of SC valve in accordance with an embodiment of the present disclosure.
[0025] FIGs. 2, 3, and 4 illustrate exemplary views of the O-Ring configured as a secondary sealing between the Domestic Pressure Regulator (DPR) and the SC Valve.
[0026] FIG. 5 illustrates an exemplary view of the dimensions of the FKM based O-Ring for the SC Valves in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0027] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0028] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[0029] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0030] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0031] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. Reference will now be made in detail to the exemplary embodiments of the present invention.
[0032] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0033] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0034] Various embodiments according to the present disclosure provide safety device for LPG cylinder and specifically pertains to self closing (SC) valve assembly. An embodiment of the present disclosure provides an O-ring of SC valve of LPG cylinder, wherein the O-ring can be made of FKM material. Preferably but not necessarily, hardness value of the FKM material used for the manufacture of O-ring can be65 +5/-4 IRHD. Another embodiment of the present disclosure provides self closing (SC) valve assembly using O-rings made of FKM material having preferably hardness value of 65 +5/-4 IRHD.
[0035] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0036] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0037] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0038] Embodiments of the present disclosure and their advantages can be best understood by reference to attached drawings.FIG. 1illustratesprior art 100 wherein a cross-sectional view of SC valve assembly containing SC spindle and gasket has been shown.
[0039] FIG. 2 illustrates an exemplary view of O-ring200 in accordance with an embodiment of the present disclosure. The O-ring 202 can be of round cross section of diameter ‘d’ with an outside diameter of ‘D’. Cross sectional diameter ‘d’ and outside diameter ‘D’ can be configured to suit corresponding groove in the SC valve and diameter of the domestic pressure regulator so as to provide sealing between the two. In an embodiment, profile of O-ring can be manufactured as per specification drawing as given in FIG.5from Flourocarbon Elastomer (FKM) material while maintaining the hardness within the specified value of 65 +5/-4 IRHD. The O-ring manufactured with FKM material and having hardness in the range of 65 +5/-4 IRHD can give the best sealing for the longest period of time have better abrasion resistance and thus enhance customer safety. With respect to FIG. 3, O-Ring 302 acts as a secondary sealing and prevents leakage of LPG to the atmosphere when the DPR connected to the SC Valve is turned ON. FIG 4 illustrates exemplary view of the O-Ring configured as a secondary sealing between the Domestic Pressure Regulator (DPR) and the SC Valve. FIG. 5 illustrates an exemplary view of the dimensions of the FKM based O-Ring for the SC Valves in accordance with an embodiment of the present disclosure.
[0040] In another embodiment O-rings manufactured with Flourocarbon Elastomer (FKM) can be of a color such as but not limited to blue that is different from existing black colour to help distinguish these from existing O-rings.
[0041] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
[0042] Tests have been conducted with O-rings manufactured from various other materials such as hydrogenated nitrile butadiene rubber, carboxylated nitrile butadiene rubber, PVC material, Fluorocarbon Rubbers (FKM) (also referred to as Flourocarbon Elastomer), PTFE, EPDM, etc. and it has been found that O-rings manufactured from Fluorocarbon Elastomer (FKM) with a hardness of 65+5/-4 IRHD in give the best sealing for the longest period of time have better abrasion resistance and thus enhance customer safety. Tests were conducted to compare the properties of the existing Nitrile Butadiene Rubber (NBR) and Flourocarbon Elastomer (FKM) and it was found that FKM has doubly superior properties than the existing NBR.
[0043] In an aspect, fluorocarbon elastomer has a hardness value in the range of 65+5/-4 international rubber hardness degree (IRHD).
[0044] Following is a list of example of tests conducted on NBR and FKM material:
S/N Name of Test Test method / Description Results Remarks
Nitrile Rubber FKM
1 Compression Set –

Indicative of percentage deformation of the material after the compressive stresses have been removed ASTM D95 Cl 13
Specimens are compressed for 24 hrs at RT & 100ºC, 168 hrs at 100 ºC. After the rest period, final thickness is measured and compression set calculated. 16.2% at RT for 24 hrs

18.86% at 100°C for 24 hrs

32.85% at 100°C for 168 hrs 8.46% at RT for 24 hrs

7.1% at 100°C for 24 hrs

12.9% at 100°C for 168 hrs The restoration property of FKM is doubly superior to NBR which will lead to better leak-proofness.

2 Compression Stress relaxation ISO 3384 Method B.
After ageing at 90 ºC Retained sealing force observed – 23% Retained sealing force observed – >55% FKM exhibits better sealing force after ageing.
3 Resistance to n-pentane –

Indicative of percentage of hydrocarbons absorbed and extracted. Weigh Sample. Immerse in pentane for 72 hrs, Remove and expose to atmosphere. Reweigh sample. Expose to atmosphere for 24 hrs. Reweigh and calculate.
Extractable–max.20%
Absorbed – max. 20% Absorption – 3.2%

Extraction – 3.7% Absorption – 0.037%

Extraction –0.13% FKM exhibits better resistance to n-pentane absorption & extraction i.e the absorption and extraction is very less compared to NBR.
4 Abrasion Resistance (before and after ageing) –

Indicative of mechanical strength of the material. As per DIN-53516 using an DIN Abrader.
Weight loss of specimen measured in mm3. Before ageing – Abrasion loss is 280 mm3
After ageing – Abrasion loss is 295 mm3 Before ageing – Abrasion loss is 150 mm3
After ageing – Abrasion loss is 156 mm3 FKM exhibits superior abrasion resistance characteristics which will result in less loss of material due to mechanical wear thereby increasing component life.

Table 1: Summary of tests conducted on NBR and FKM material.
[0045] Therefore based on the test results, the existing nitrile based O-Ringof SC valve of LPG cylinder can be replaced with Flourocarbon Elastomer (FKM) as per the drawing specifications as per the S C Valve technology document, having a hardness of 65 +5/-4 IRHD. In another aspect, the O-rings manufactured with Flourocarbon Elastomer (FKM) can be of blue colour to help distinguish these from existing O-rings.
[0046] Prototypes of FKM based O-Rings were developed and from the lot, random samples were selected and subjected to laboratory tests. These random samples of FKM based O-Rings were fitted inside new valves and these valves were subjected to all the tests as per the relevant BIS standard IS 8737 and checked for Dimension Conformance &the Hardness Measurement. The results of the laboratory tests are summarized below:-
Tests were carried out as per IS 8737:1995, of which summary is given below:

Sr No. Name of Test Test method / Description Remarks

1. Compatibility with LPG (As per IS 9798:1995) Weigh sample and immerse in pentane maintained at RT for 72 hrs. Remove sample and expose to atmosphere. Take the weight of the sample and expose it further to atmosphere for 24 hrs and reweigh the sample. Calculate for absorption and extractable.
Extractable – max. 20%
Absorbed – max. 20% Extractable – 0.088%
Absorbed – 0.059%
Found Conforming to Specifications

2. High Temperature Test Exposure to high temperatures @ 65ºC for 10 minutes. After attaining 65ºC, it is removed and exposed to atmosphere so as to return to ambient condition and then tested for pneumatic tests. Found Conforming to Specifications
3. Low Temperature Test Exposure to Low Temperature @ 20ºC. After attaining -20ºC, it is removed and exposed to atmosphere so as to return to ambient condition. Then sample is tested for pneumatic tests. Found Conforming to Specifications

4. Tightness of Joint Packing and Valve Spindle With spindle in closed position, test pressure of 1000mm water column applied to valve outlet and leak to be observed. No leak observed. Found conforming to specification.
5. Tightness of Valve Housing and Valve Spindle With valve spindle in closed position, a test pressure not less than maximum working pressure (17 kg/cm2) applied to inlet of valve housing body and leak to be observed. No leak observed. Found conforming to specification.
6. Tightness of Joint Packing and Housing With valve spindle in open position, a test pressure not less than maximum working pressure (17 kg/cm2) applied to inlet of valve housing body and leak to be observed. No leak observed. Found conforming to specification.
7. Cycle Test Valve shall perform satisfactorily at not less than 5000 cycles of opening and closing operations with valve inlet connected to an air supply not less than 7 kg/cm2 and the opening travel of the spindle shall not be less than minimum of designed travel during the test. After this test, the valve shall be subjected to pneumatic tests. Found conforming to specification.

Table 2: Summary of tests performed on FKM based O-Rings
[0047] The samples of FKM O-Ring were checked for dimensional conformance as per the component drawing enclosed in Fig 5 and it was found meeting requirements.
[0048] The samples of FKM O-Rings were checked for hardness and they were found meeting the requirements of 65 +5/-4 IRHD.
[0049] Leak Test – Random sample of FKM O-Rings were selected and fitted inside SC Valves and subjected to a pressure of 17 kg/cm2 to check for any leakage. No leakage was observed and the valves fitted with FKM O-Rings were found meeting the requirements.
[0050] Compression Set – Random samples of FKM O-Rings were selected and subjected to a Compression Set Test. The Compression Test is performed on 02 sets of samples, one at Room Temperature and the other aged at 100°C for 24 hrs. Initial height of the samples is taken and then they are subjected to a compression set load in a Compression Set Flange set up for a period of 24 hrs. After completion of the time period, the samples are removed from the Compression Set flange and the final height is taken. The difference gives the deformation of the sample which indicates its Compression Set property.

S/N Name of Test Test method / Description Results Remarks
1 Compression Set ASTM D95 Cl 13
3 set of Specimens are taken and individually they are compressed as per ASTM D95 for 24 hrs at RT & 100ºC and for 168 hrs at 100 ºC. After the rest period, final thickness is measured and compression set is calculated. 9.48% at RT for 24 hrs

12.85 % at 100°C for 24 hrs

Meeting the specifications

Table 3: Result and remark for Compression set test onFKM based O-Rings
[0051] Samples of SC Valves with FKM based O-Rings was fitted in 2000 nos. of LPG Cylinders and these LPG Cylinders were circulated to customers, for monitoring the performance of the FKM based O-Rings in actual field conditions for a period of usage of 06 months. After a period of 06 month of usage, the SC Valves fitted with FKM based O-Ring was checked for O-Ring leak. There was no rejection of SC Valves on account of O-Ring Leak.

ADVANTAGES OF THE INVENTION
[0052] The present disclosure relates to an improved O-ring of SC valve of LPG cylinder.
[0053] The present disclosure relates to an improved O-ring of SC valve of LPG cylinder that has enhanced flexibility while retaining their resistivity to hydrocarbons.
[0054] The present disclosure relates to an improved O-ring with increased compression set property leading to increased Customer Safety.
[0055] The present disclosure relates to an improved O-ring with increased abrasion resistance property leading to improved performance of the valve and thus increase in its life.
[0056] The present disclosure relates to an improved O-ring with increased resistance to hydrocarbons resulting in reduced valve leaks.
[0057] The present disclosure relates to an improved O-Ring with low permeability resulting in increased customer safety.
,CLAIMS:1. An O-Ring for a Self Closing (SC) assembly of a pressurized gas cylinder, wherein the O-ring is made of a fluorocarbon elastomer.

2. The O-ring of claim 1, wherein the fluorocarbon elastomer has a hardness value in the range of 65+5/-4 international rubber hardness degree (IRHD).

3. The O-Ring of claim 1, wherein the O-Ring has a hardness of 65+5/-4 IRHD.

4. A self closing valve assembly comprising an O-ring, wherein the O-ring is made of a fluorocarbon elastomer.

5. The self closing valve assembly of claim 4, wherein the fluorocarbon elastomer has a hardness value in the range of 65+5/-4 international rubber hardness degree (IRHD).