Thermal Insulation of Piping

May be it has a relation with personnel protection as wind conditions make up an important design criterion in designing for personnel protection. In open areas in coastal regions, for example, there is usually a prevailing wind that can be considered in the insulation system design. In this situation, less insulation would be required than if the piping system were in an enclosed space sheltered from the wind. This provides an additional source of heat loss—convection—which occurs at the surface in this case. This heat loss cools the surface of the insulation; however, it also decreases the effectiveness of the overall insulation system.

, So you need to determine the reason of insulation for hot or cold service or PP.

Also I want to add another point of view because vessels are normally surrounded by other equipment and structures, making less convection (as thermal conduction and convection are the controlling modes of heat transfer ), so increasing wind speed may be to compensate this less convection to maintain same insulation thickness within the same design criteria.

Finally insulation thickness based on pipe size, insulation thermal conductivity or material, and range of temperature service.

The answer to this is . . . drafting . . . generally the design criteria of insultation is based on worse case conditions . . . thus it is likely that an indoor insulated pipe may be located in a natural draft area that sees air velocities due to ducting or air conditioning, that may expose that insulation to a higher constant air velocity condition.

Logically, it is right to say that wind speed inside is greater than outside. If you recall that velocity is volume divided by x-sectional area. Since inside the plant area, there is a lot of structure and piping and vessel etc. this reduces the x-sectional area and therefore the wind speed increases. in your cases it seems that the x-sectional area inside the plant is reduced by 2.

A quick check on the heat of conduction, .5 m/s heat loss is about 20% more than that at 0.25 m/s.

As far as know there is no general guidelines with regard to wind speed for insulation calculation. What I suggest is that you check with local meteorology department on the average wind speed in your area. If not available then you need to conduct a survey a year round and take the average.

I suggest that you conduct a sensitivity study using both wind speed for the inside and most probably it make very little difference in term of insulation thickness, since normally insulation thickness selected is the next higher standard available than what have been calculated.

Hope the above helps.