I would like to know if we can use glycerine filling as well as heat tracing for same differential pressure impulse tubing, will either one is sufficient or both have a better result?
If the service is hot water or steam then a condensate pot should keep the impulse line full of water.
You should use a fluid similar to your working fluid so that the density difference is not too large and the impulse line compensation will not be too large. Density in impulse lines may also change as the fluid is diluted by the process fluid.
We have used water/glycol mixes in water service to prevent freezing.
But heat tracing will also prevent this. In oil and hydrocarbon service you might use silicone oil or have a clean HC purge that keeps the impulse line clear and full of a known fluid.
It would help if we knew what you are trying to measure. often you can avoid the need for heat tracing by your installation method, for example, taking advantage of the process heat to keep the impulse lines warm. I would avoid intermediate fluids as too hard to maintain.
Diaphragm capillary systems are ok provided the ambient temperature is stable or the DP is high enough, not so good for low DP for example measuring Interface level.