This International Standard specifies requirements and givesrecommendations for the design, materials, fabrication, inspection,testing, preparation for shipment, and erection of fired heaters,air preheaters, fans and burners for general refinery service. Published By:American Petroleum Institute (API).We will take up another issue in the next few weeks. Thanks to all the participants who have donated their time and know-how in improving this standard. The primary purpose of this standard is to establish minimum mechanical requirements.ĪPI subcommittee of heat transfer (SCHTE) meets twice a year and all the efforts and hours put into this standard are voluntary and selfless service. The heat pick up by each pass can be predicted to ensure thermal symmetry of passes.ĪPI Specifications (standards) are published by American Petroleum Institute as an aide to procurement of standardized equipment and materials API publications may be used by anyone desiring to do so.ĪPI-560 standard for fired heater for general refinery service is based on accumulated knowledge and experience of petroleum refiners, fired heater manufacturers and engineering contractors. These days we have powerful CFD analysis tools that can easily model the heat distribution in fired heaters. We strongly recommend that the thermal symmetry requirement of passes should be put back in API-560 design requirements. If you have a heater having pass imbalance problem, please contact us and we can help you with the heat distribution. FIS worked with the client to fix this problem.
This was causing the heater to coke up very fast. The upper passes were receiving 30% more heat than the lowest two passes. In real life, the situation is very different and firebox heat distribution dependent upon the burners flame length. When we are designing fired heaters, we assume that radiant section is acting like a continuously stirred tank reactor and flue gas temperature is uniform from top to bottom. This problem is very common in cabin heaters where the passes are laid out in upper and lower section. This was leading to very short run lengths. The heater was experiencing high tube metal temperatures in the upper section near the arch. We looked at a crude heater at one of our clients facility. We have seen several heaters which have severe pass imbalance or firing imbalance. Operators want to have same flow in all the passes and want to ensure that outlet temperature of the fluid should be identical.
It is important that all the passes receive equal amount of heat. Most of the heaters have multiple passes on the fluid side. In our opinion, this was diluting one of the most important requirements of fired heater design. Multipass heaters shall be designed for hydraulic symmetry of all passes.” Thermal symmetry requirements were removed. Multipass heaters shall be designed for hydraulic and thermal symmetry of all passes” This was changed in the 2nd edition to “Heaters shall be designed for uniform heat distribution.
We found that the first edition of API560 stated in clause 2.1.1 - “Heaters shall be designed for uniform heat distribution. Our team decided to compare all the five editions and see how the standard evolved from 60 pages to more than 320 pages. We would like to share with you some important changes in the standard over the time. API-560 first edition came out in 1986 and its fifth edition was issued in 2016. Some companies issue addendums to API-560 to cover the items that are not addressed in the standards. Almost all companies follow API-560 Standard for Fired Heaters religiously for specifying and purchasing fired heaters all over the globe.