Hi Saravanan,
welcome to our forum and thank you for your interest in the ADS1147.
Would you mind sending us the schematic of your implementation and how you test for an open RTD?
If you use a ratiometric measurement approach where you excite the RTD with the integrated current sources and use the same current to generate a reference voltage for the ADS1147 across a reference resistor you will run into problems. If your RTD would fail open, the positive input where the excitation current source is connected to would be pulled to the positive supply and the reference voltage would probably be close to zero. In this case the ADS1147 will not provide reliable data.
Regards,