Thank you very much for your support. You really knew what I´m looking for. I`m going to explain the reason for what I want this and what I preted to do:
-I have a flare stack that will flare or burn Gas with some composition. It will produce SMOKE so the flae will be assisted with steam up to 20% of total flaring. The quantity of steam is 40,000.00 kg/hr. I have my pipe of 8"Ø sch 80 with a insulation of 2" thickness. The total length of 8" piping is almost 120 mts including loops and so on. My client is asking me for a MINIMUM QUANTITY OF STEAM ON PIPING IN ORDER TO PREVENT OR AVOID THERMAL SHOCK BUT HE IS ASKING ME FOR THE CALCULATION. In order to solve this I was thinking in the following:
--I have the flow of steam for maximum scenario, including temperature and pressure, even enthalpy and entropy and specific heat can be calculated or obtained. Thermal shock is a SUDDENLY CHANGE OF TEMPERATURE ON MATERIAL SO IT MAY CRACK. So, I was thinking to obtain the minimum temperature which thermal shock can be produced. In any case a formula for minimum temperature does not exist, I was thinking to make a stress analysis with thermal conditions from 0 celcius to 300 celcius in order to know the stresses which pipping can be able to resist without problem. Having the minimum temperature (it will be according to results from thermal analisys) I`m going to be able to have the range of temeperature which a thermal shcok can be produced. Then using a formula for calculating the HEATING ( q = m cp dt/t ) and ( ms = q/he) and having the temperatures (one will be 0-300 celcius and the other from 0 to minimum temperature in celcius) and with that I can have the Heat for minimum temperature so I`m gonna be able to calculate the MINIMUM QUANTITY OF STEAM.
Accordint to your writing, I can see that THERMAL SHOCK is no produced on steams lines for flare stack issures.....but my client thinks that this effect can be prodcued when on pipping exists suddenly different temperatures conditions......what do you think about it.
I do not consider the insulation because the temperature for thermal shock is the temperature on my piping, not on the outside layer of my insulation. So in order to NOT TO CONSIDER MORE ELMEENTS THAT MAKE MY EQUATION LARGER, I think I can reduce it or limit it to just piping temperature and work with that. I think insulation purpuse is to not to have any heat loss from origin of steam to the end in which the steam will be used (n my case to the top of my flare) but I do not care what is the heat loss because I have the insulation and its thickness by original specs....I`m just thinking about the temperature (internal temperature of piping)so a thermal shock can be produced....what do you think?