TICO welded steel storage tank can be designed to meet various of standards for different countries and regions, including GB、API 650、API 620、BS、JIS, etc. Welded steel storage tank accessories like breather valves, relief valve, manway, spiral stairs and so on are also can be designed and fabricated in our manufactory facility and then. HMT Fabrication Services offers repairs and modifications to aboveground storage tanks as well as fully engineered new build projects. Our turn-key shop will meet all project design, cutting, machining, welding, NDE inspections and blasting requirements. Full in-house capabilities help ensure lead times and quick turnaround.
API 650 Spiral Staircase Design Issues
API 650 Spiral Staircase Design Issues
Hi Everyone, I don't usually post in these forums as I dont get to much involved in API work but recently I embarked on a project to correct a defective installation on an oil storage tank. I 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 1/2' to much. I 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. Also the steps are not perfectly level. Some of them are 1/4' off across the 28' span of the step. 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. Am I being way to extreme here? Is this requirement on API 653 actually supposed to deal with staircase reinforcing plates or for actual spots where the tank is worn or cracked and needs to be reinforced?
Again, this staircase feels perfectly fine and is not by any means un-usable or uncomfortable to use. So I am wondering if you guys have any experience here. I am going to recommend that any deficiencies be corrected? Am I going to an extreme? Opinions are welcome.
Thanks,
Rob
- 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 1/2' to much. I 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. Also the steps are not perfectly level. Some of them are 1/4' off across the 28' span of the step. 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. Am I being way to extreme here? Is this requirement on API 653 actually supposed to deal with staircase reinforcing plates or for actual spots where the tank is worn or cracked and needs to be reinforced?
Again, this staircase feels perfectly fine and is not by any means un-usable or uncomfortable to use. So I am wondering if you guys have any experience here. I am going to recommend that any deficiencies be corrected? Am I going to an extreme? Opinions are welcome.
Thanks,
Rob
Spiral stairs for storage tank
Spiral stairs for storage tank
Customer has requested this instead of the usual ladder/cage, never prepared drawings for one before.
Anyone have experience with these and care to share some insight:
1. What program was used to model it? Trying to do it in Bricscad but it's 3D capability is not up to snuff.
Main issue is modeling the channels to form around a helix.
2. Where can one find any standards? Only PIP specs. I've found are for linear type stairs.
The basic design we were going to go by:
Vessel: 204' OD
Height: from to grade to top of grating/platform = 235'
Span: roughly 120 degrees. Too steep?
Stair Risers: channel 12x20.7#/ft
handrails: 2.5x 2.5x 1/4 angle
treads - 12-1/8 x 36 galv. grating
Any help or insight would be greatly appreciated!
Anyone have experience with these and care to share some insight:
1. What program was used to model it? Trying to do it in Bricscad but it's 3D capability is not up to snuff.
Main issue is modeling the channels to form around a helix.
2. Where can one find any standards? Only PIP specs. I've found are for linear type stairs.
The basic design we were going to go by:
Vessel: 204' OD
Height: from to grade to top of grating/platform = 235'
Span: roughly 120 degrees. Too steep?
Stair Risers: channel 12x20.7#/ft
handrails: 2.5x 2.5x 1/4 angle
treads - 12-1/8 x 36 galv. grating
Any help or insight would be greatly appreciated!