FIELD OF THE INVENTION;
This invention relates to the field of quality control of Fire Resistant Fluid (FRF) used as lubricants and Electro-Hydraulic fluids in the steam and gas turbines up to 1000MW.
This invention further specifically relates to development of a novel 85 fast method for determination of composition of trixylenyl phosphate ester based Fire Resistant Fluid (FRF) by using Nuclear Magnetic Resonance (NMR) spectroscopy.
BACKGROUND OF THE INVENTION:
A family of triaryl Phosphate Ester based fire resistant fluids are used as lubricants and Electro-Hydraulic fluids in the steam and gas turbines up to 1000MW to meet the requirements of high fire resistance temperature (500-550°C) and high hydraulic pressure (150 psig or 10 bar) encountered during the operation of the power plant.
The Triaryl Phosphate Ester fluids are derived from the chemical reaction of Phosphorus Oxychloride with alcohol or organic compound containing hydroxyl group. They have built in fire resistant properties due to

phosphorus element in their molecular structure. The basic chemical structure of Triaryl Phosphate is according to formula I below

A family of Triaryl Phosphate Ester fluids commercially available are listed in Table 1.


All these fluids differ in their chemical structure in respect of size and type of the alkyl groups (R) present as substituents on the phenyl ring. As a result, they offer different properties like hydrolytic 8B oxidation stability and air release etc. which determine the service life of the power plant.
Among these fluids, trixylenyl phosphate is currently preferred for turbine control system because it has best hydrolytic stability and air release properties thereby resulting in trouble free long service life of the power plant.
The fluid is further modified by mixing it with other fluids or by adding property improver additives by the suppliers to obtain various grades of Fire Resistant Fluids. These fluids vary considerably in their properties to suit different applications. Hence, most of the trixylenyl phosphate ester fluids are proprietary as to their chemical composition. The selection of a brand of a fire resistant fluid (FRF) for a particular application depends upon a number of factors such as physical and chemical properties the oil, safety requirements, design of oil conditioning system and operating temperature etc. Therefore, the fluid is selected on the basis of reputation and reliability of the supplier and/or approval of designer of OEM (Original Equipment Manufacturer).

The changes in the chemical composition of the trixylenyl phosphate can be due to either variation in the composition of the feedstock of xylenol used for its manufacture or changes made by the suppliers intentionally for obtaining price competitiveness. The changes in the chemical composition of trixylenyl phosphate fluids can deteriorate its hydrolytic & oxidation stability thereby resulting in formation of deposits, sludge & foams in the system during its use.
At present, the quality assurance of the purchased/ selected brand of a FRF is based on the conventional tests used for determination of physical and chemical properties. These tests, usually, are not adequate to detect the formulation changes made by the suppliers. . In view of above, a need was felt for a test which could detect the above referred formulation changes made by the suppliers .
OBJECTS OF THE INVENTION:
It is therefore an object of this invention to a process for the quality control of Fire Resistant Fluid (FRF), which can detect the formulation changes in a FRF sample.

It is a further object of this invention to a process for the quality control of Fire Resistant Fluid (FRF), which is simple, reliable and cost-effective.
Another object of this invention to a process for the quality control of Fire Resistant Fluid (FRF), which uses simple, easily available chemicals and equipments.
These and other objects and advantages of the invention will be apparent from the ensuing description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig. 1 shows the 1H NMR spectrum of sample A. Fig. 2 shows the 1H NMR spectrum of sample B.
DESCRIPTION OF THE INVENTION:
This invention relates to a process for the quality control of Fire Resistant Fluid (FRF).
In accordance with this invention the FRF to be used in the turbine control system is subjected to Nuclear Magnetic Resonance (NMR). The

1H nuclei absorb energy from a radio frequency (RF) source at certain characteristic frequencies. The position of the nuclei in the molecule affect the electronic environment of the nuclei and thus affect the absorption frequency. Depending on the local chemical environment, different protons in a molecule resonate at slightly different frequencies. The frequency differences observed in the resultant spectrum define the molecular structure of the sample. Variations in molecular structure and/or composition of the sample are determined through changes in the NMR spectra.
The area under each peak is proportional to the number of hydrogens that are giving rise to that peak. The ratios of the areas of the NMR peaks observed for different kind of protons (H) determines the composition of the FRF.
The NMR spectrum is obtained for a sample and the integrated area for a proton in each environment is separately calculated. For instance, in a compound containing both methyl (CH3) and ethyl (CH2CH3) groups, the integrated area for each proton in each group is calculated. The integrated area for one proton in each group having a different electronic environment is then added up. The value obtained is used to calculate the percentage of the FRF compound which contains a single type of

functional group containing hydrogen and therefore, the percentage of other chemical units in the sample.
The invention will now be explained in greater detail with the help of the following non-limiting examples.
Experiment:
The NMR spectra were taken at frequency of 400 MHz on instrument model UNITY INOVA of M/S Varian Inc, U.S.A. for both samples. The spectra obtained are shown in Fig. 1 & 2 respectively.
Assignment of NMR Spectra:
The assignment of different NMR peaks obtained for spectra of sample-A is given in Table 2.

Table 2. Assignment of NMR peaks & their areas for Sample A

Calculation for composition for sample A:-
Integrated area per proton for the five Nos of H nuclei of -CH3CH2 -group from NMR peaks appearing at chemical shifts of 1.21 & 2.62 ppm= (12.88+8.76) / 5 4.3 Units Integrated area per proton for six Nos of H nuclei present in two number of -CH3 groups of xylol from NMR peaks appearing at chemical shift of 2.2ppm = 40.75/ 6 = 6.79 = 6.8 Units

Total integrated area per proton for both -CH3 & -CH3CH2 --groups =4.3+6.8
= 11.1 Units Percentage of TXP (which contains two -CH3 groups) = (6.8 x 100) / 11.1
= 61.2% Percentage of other chemical unit i.e. tri ethyl phenyl phosphate containing ethyl group (-CH2-CH3) = 38.8 %
The assignment of NMR peaks obtained for sample-B is given in Table 3.
Table 3. Assignment of NMR peaks 85 their areas for Sample B


Calculation for composition for sample B:
Integrated area per proton for the five Nos of H nuclei present in -CH3CH2 - groups from NMR peaks appearing at chemical shifts of 1.21 8s 2.62 ppm = (10.92+7.72) / 5
3.7 Units Integrated area per proton for six Nos of H nuclei present in two number of -CH3 - groups of xylol from NMR peak appearing at chemical shift of 2.2ppm = 43.99 / 6 = 7.3 Units Total integrated area per proton for both -CH3 85 -CH3CH2 groups = 3.7+7.3
= 11.05 Units Percentage of TXP containing two methyl groups = (7.3 x 100)/ 11.05
= 66.06% Percentage of other chemical unit containing ethyl group (-CH2-CH3) Triethyl phenyl phosphate = 33.5%
Percentage of chemical unit containing butyl group i.e.Tertiary Butyl Triphenyl Phosphate additive = 0.45 %

The chemical compositions of fire resistant fluids of two suppliers A and B determined by NMR spectroscopy are given in Table 4.
Table 4. Compositions of Fire Resistant Fluids of suppliers A 85 B

The XH NMR spectra of sample A is shown in Fig. 1 and that of sample B in Fig. 2.

WE CLAIM;
1. A process for the quality control of fire resistant fluid (FRF) comprising subjecting the FRF sample to Nuclear magnetic resonance (NMR) spectroscopy to obtain the NMR spectra, calculating the ratio of the area under the NMR peaks obtained for the protons present in different electronic environments, followed by computing the quantity of individual constituents present in the sample of FRF, and estimating unacceptable variation in the chemical composition of the FRF.
2. The process as claimed in claim 1, wherein the ratio of the area for the protons present in different electronic environments is obtained by calculating the integrated area per proton present in each substituent in a different electronic environment, obtaining therefrom, the total integrated area per proton for all the substituents in different electronic environments, followed by obtaining the percentage of the FRF compound containing the given quantity of hydrogen and determining the percentage of the FRF compound in the sample.
3. The process as claimed in claim 1, wherein the FRF is selected from trixylenyl phosphate, triphenyl phosphate, tricresyl

phosphate, isopropyl phenyl phosphate and tertiary butyl phenyl phosphate.

ABSTRACT

TITLE: METHOD OF DETERMINATION OF COMPOSITION OF
TRIXYLENYL PHOSPHATE ESTER BASED FIRE RESISTANT FLUID
(FRF) BY NMR SPECTROSCOPY
A process for the quality control of fire resistant fluid (FRF) comprising subjecting the FRF sample to Nuclear magnetic resonance (NMR) spectroscopy to obtain the NMR spectra, calculating the ratio of the area under the NMR peaks obtained for the protons present in different electronic environments, followed by computing the quantity of individual constituents present in the sample of FRF, and estimating unacceptable variation in the chemical composition of the