Turbine steam flow always showing low (i.e. 4 TO 5 TPH) compare to boiler output. This different is increasing while load is increase. Both side same value used for steam compensation (max pressure and temperature value as per OEM recom)---is there any issue?

Boiler side 0-5000 MMWC TX range used and turbine side 0-10000 MMWX TX used. There is no much long from boiler to turbine and pipe insulation also good. Let me know any correction need in DCS.

In general how to desire the max TPH value for maxium DP in TX or DCS. What are all the parameters need to consider for that (like density, pipe dia, temp, PR, etc)?

 

Your design reference should be closer to actual. i.e. if you're working pressure is 45 kg/cm2, then you should take design pressure @ 45 kg/cm2, desig temp @ 45 is equal to 260 degc, & density 23.71 kg/m3.

The final calculation depends upon the iteration taken for equation ir, we are going to first iteration only.

If your design & actual parameter are so far, it may create diff in second iteration & it always to be considered.