Leakage of hydrocarbons can lead to fire, so it is the leakage that needs to be addressed to prevent fire. Most well-run refineries will have rigorous procedures for flange bolting that prevent it.

Insulation will slow down heat losses and gains, and its use has a substantial effect on the economics of operation, as well as having a role to play in operative safety. If one uses the rule-of-thumb that every uninsulated flange costs 3kW, the savings soon justify the cost of insulation.

The issue of leakage and fire comes from the issue of poor assembly and or the lack of timely maintenance. Insulation has nothing to do with fires and leakage.

The fact is that flanges do leak, and when they are insulated, the leak is not evident for some time. Yes, smoke and fires are possible when hot oil leaks into porous insulation. (The oil degrades creating "lights" that have a low autoignition temperature). Non-porous insulation does exist and should be used in this type of service. Not insulating the flanges is another option, but the heat loss can be excessive as well as increased operator exposure to hot surfaces.

Another consideration should be the temperature of the fluid, vs. the flash point and autoignition point of the fluid.

If you would like to discuss alternatives, please call me at 216-401-1845.

Dear Pau,

I understand your concern regarding heat loss thorugh flanges, but safety first. In my experience of various project of various client using various specification, i have come across one thing common.

"THE LINES WITH HYDROCARBON, SOUR SERVICE, LETHAL SERVICE AND HAZARDOUS SERVICE SHOULD NOT BE INSULATED."

Please get back if any doubt.

Mr mehta,

Thkx 4 ur reply . As per your statement if it is uninsulated and if there is any chance of leak of hydrocarbon , what wil be scenario and also uninsulation of these flanges and valves will lead to more heat loss .

Dear Paul,

I have worked with process plants, and believe me leakage not only is hazardous but also cause problems like corossion. An insulated flange with such service in case of leakage is difficult to catch attention and only with insulation is not able to hold the leakage, it becomes prominent.

As I empasized before, heat loss is important but not as important as safety. So the flange joints with such hazardous services should not be insulated.

Again for valves, i never say, they should not be insulated. Big valve bodies can be insualted, but not the valve flange joints.

as per B31.3: The ability of thermal insulation to protect piping against failure under fire exposure

(e.g., its stability, fire resistance, and ability to remain in place during a fire)

Pl provide box type insulations which can be removed and inspected for leakages in the case of doubts. The insulation should have small hole of about 10mm dia at the bottom right through the thickness insulation so that oil drip can be observed in the case of liquids.