API-650 Tank Hot Tap Size Limit
API-650 Tank Hot Tap Size Limit
(OP)
Hi All,
For performing hot-tapping on API-650 storage tanks, API-653 Table 9.1 only list nozzle size up to NPS18. Does it limit the hot-tap nozzle size up to NPS18? For certain cases if larger size hot-tap is needed, which code/standard shall be followed to validate the design?
Thank you!
For performing hot-tapping on API-650 storage tanks, API-653 Table 9.1 only list nozzle size up to NPS18. Does it limit the hot-tap nozzle size up to NPS18? For certain cases if larger size hot-tap is needed, which code/standard shall be followed to validate the design?
Thank you!





RE: API-650 Tank Hot Tap Size Limit
RE: API-650 Tank Hot Tap Size Limit
RE: API-650 Tank Hot Tap Size Limit
RE: API-650 Tank Hot Tap Size Limit
RE: API-650 Tank Hot Tap Size Limit
RFI: In API-653 the table 9.1 only lists hot-tap up to NPS18. Is this for a specific reason? For hot-tap over NPS18 which code/standard shall be followed to validate the design?
API Standard Dept. Answer:
Thank you for your recent inquiry. Due to limited committee resources, API staff cannot respond to questions seeking the rationale or intent for requirements in its standards. These requirements are based upon consideration of technical data and the judgment and skill of experienced engineering and technical personnel representing both users and manufacturers who serve on the standards-writing committees. Also, the American Petroleum Institute (API) is not able to provide an answer to your inquiry because API does not provide consulting on specific engineering problems or on the general understanding of its standards. Based on the information you submitted, we recommend you seek the assistance of a consultant or engineering company familiar with the requirements of the standard.
RE: API-650 Tank Hot Tap Size Limit
RE: API-650 Tank Hot Tap Size Limit
RE: API-650 Tank Hot Tap Size Limit
There are two viewpoints on this:
1) you can do anything the code does not specifically prohibit
2) you can only do the things that the code describes
Your company must choose which philosophy to follow.
RE: API-650 Tank Hot Tap Size Limit
For ASME, if it is not forbidden I proceed carefully, with a LOT of research. ASME is VERY well documented, and there is very little chance that somebody else has not already run into the same problem, and generated a Code Case. And if it is still silent, I proceed.
RE: API-650 Tank Hot Tap Size Limit
When asked if your work is "per the code" do you say "yes" if you have done something that the code is silent on, like a 24" hot-tap? My view is that this would not be "per the code" because the code stops explicitly at 18". Would you PE seal a 24" hot-tap and note it is per API 653?
RE: API-650 Tank Hot Tap Size Limit
653 does not forbid Hot Taps over 18", they just do not have it listed as pre-approved. Thus I would handle it like an Alteration - the document(s) directing the work would require the approval of a tank engineer and an API 653 Inspector. Would probably use the wording "in the manner of API-653", assuming that what is calculated looks like the preapproved 18" nozzle.
RE: API-650 Tank Hot Tap Size Limit
API says that their publications are to facilitate the broad availability of proven, sound engineering and operating practices without obviating the need for applying sound engineering judgment while not inhibiting anyone from using any other practices.
The text says "the connection size and shell thickness limitations are shown in Table 9.1.". This would appear to expressly limit the size of a hot-tap to 18 inches. A 24 inch hot tap would be outside the code. Would it be in violation of the code? Perhaps that depends on the reader's inclination ( engineer, lawyer, inspector, owner, insurance agent, etc ), interpretation and appetite for risk. I also consider the present and possible future circumstances of an inquiry ( initial design, after the fact inspection, incident investigation, deposition, etc ).
I am always cautious when scaling things up, as you mentioned earlier there is a concern of the repad and shell interaction. There may be other issues to consider...if this opening is near the corner weld, if this were a cyclically heated tank, if this nozzle were to experience piping stresses, etc.
I would also be cautious because as we all know, temporary modifications often become permanent and used for unforeseen applications beyond the original intent.
RE: API-650 Tank Hot Tap Size Limit
Absolutely. Thus the comment about taking care with the repad calc and attachment weld details. When you are above [or below] the 'cookbook' API-650/653 sizing details, proceed very carefully and conservatively. ASME PCC-2 has some excellent methods of Post-Construction additions.
RE: API-650 Tank Hot Tap Size Limit