Spiral stairs must meet the vertical clearance requirements in paragraph (d)(3) of this section.Winding stairways may be used on tanks and similar round structures when the diameter of the tank or structure is at least 5 feet (1.5 m).The requirements of paragraphs (c)(2) and (3) do not apply to standard stairs installed prior to January 17, 2017.
OSHA will deem those stairs in compliance if they meet the dimension requirements specified in Table D-1 of this section or they use a combination that achieves the angle requirements of paragraph (c)(1) of this section. In addition to paragraph (b) of this section, the employer must ensure alternating tread-type stairs. The stairs were attached to the tank by welding the stair to a reinforcing plate and welding the reinforcing plate to the shell. Spiral Stairs On Shop Built Tank Api 650 How To Properly DesignI was hoping you guys could answer a few questions for me about how to properly design and install the spiral staircase for a tank. In regards to the spacing of the steps, I am looking at the requirements on figure 5-18 and 5-19 that have all the guidelines for staircase design. The question is, are there any notes anywhere on tolerances for this The stairs that got installed have a rise and run spacing that is about 12 to much. Spiral Stairs On Shop Built Tank Api 650 Plus The RunI have walked up the stairs and dont feel any unease, so I would think they are just shy of proper spacing (twice the rise plus the run 26 max.) I guess the contactor that installed them just wasnt hugely careful. Is this a major problem that should need to be corrected - Second question is in regard to reinforcing plates, used to attach the steps to the tank. Some of these plates cover the tank seems and they are not much larger than the steps themselves. Thus they do not exceed past the seems by the required 6 called out in API-653 9.10.3. I was going to recommend that these plates be removed and the plates be replaced with proper size plates. In order to do this, they may have to combine reinforcing plates from two or three steps together. I am going to recommend that any deficiencies be corrected Am I going to an extreme Opinions are welcome. If you measure the rise x 2 plus the run at the tank shell or perhaps at the stairway centerline, is it within the API numbers On the repads, API 650 does not require them. Is this a new tank or a repair Section 9.10.3 is for bottoms - are you in another section for shell. As stated that stairway on the tank is in compliance with the 28 rule and most of the steps are about 14 out of level from end to end. Measured at the tank and then measured at the support rail side. The measurement of twice the rise plus the run is just over the API numbers. Are these recommended guidelines or are they requirements That is really my question. So far I had suggested all the steps be corrected to the proper API dimensions, but I dont want to make someone do a tremendous amount of work, when it is not required by the code governing the installation. You guys seem to be correct in regards to my API653 reference. I was also looking at figure 9-6, but that also seems to be for tank bottom repairs. There do not seems to be any restrictions on attachment of stairs or other localized loads. In that case I think we will follow good pratice and not overlap welds HAZ Etc. Note that OSHA does not require that you use the exact rise and run in the OSHA table, as long as the angle of the stairway is between 30 and 50 degrees with a 1 inch overlap and at least an 8 in tread. Also see OSHA 1920.24. API only cares about permanent attachment welds when the shell is above group 3. See section 5.8.1.2. API is silent on other grades of steel and therefore there are no requirements for permanent attachment weld spacing on these tank shells. Im not aware of there being a minimum tread depth or overlap requirement, either. One last question - The figure I was looking at with regard to reinforcing repair plates is API653 figure 9-1.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |