# Drilling Holes in Pressure Vessel Flanges

• chris812
In summary, the conversation is about designing a pressure vessel and the concern about how to include drilled holes in the design. The person mentions using ASME code and needing to calculate the stress acting on the flange with the added holes. They also mention the materials and dimensions of the vessel. They are seeking help and a book recommendation for calculating stress concentration factors.
chris812
Hello,

I have been designing a pressure vessel for the last week. I have based all my maximum allowable stresses on ASME code but can't figure out how to include drilled holes. I plan to be using a pipe welded to a cap at one end and attached to a blind flange with holes drilled in it at the other.

I am sure that the added holes will compromise the stress acting on the flange but don't know how to measure (or calculate) this. I also imagine that there would be a minimum distance between holes allowed.

If needed I am using pipe with ID of 1.1" and wall thickness of 0.11". The cap is elliptical and the flange is a nominal 1" 300 class slip on. All material is 304H stainless steel. I plan to drill a 1/2 diameter hole in the center of the blind flange.

Any help would be greatly appreciated,

Chris

It's going to be geometry-dependent, but you'll have to take a look at the stress concentration factor for the hole and/or run an FEA model of the vicinity you're worried about.

Here is a book I have that helps with calculating stress concentration factors of features like holes in plates:

https://www.amazon.com/dp/0471538493/?tag=pfamazon01-20

Last edited by a moderator:

## 1. What is the purpose of drilling holes in pressure vessel flanges?

Drilling holes in pressure vessel flanges allows for the installation of additional components such as valves, gauges, or instruments. These components are necessary for the proper functioning and monitoring of the pressure vessel.

## 2. How are the holes drilled in pressure vessel flanges?

The holes in pressure vessel flanges are typically drilled using specialized tools and machinery, such as a drill press or a vertical boring machine. The size and placement of the holes must be carefully calculated to ensure the structural integrity of the flange is not compromised.

## 3. What materials are used for drilling holes in pressure vessel flanges?

The most commonly used materials for drilling holes in pressure vessel flanges are high-speed steel and carbide drills. These materials are able to withstand the high pressure and temperature conditions within the vessel, and are also strong enough to penetrate the thick metal of the flange.

## 4. What precautions should be taken when drilling holes in pressure vessel flanges?

Safety is of utmost importance when drilling holes in pressure vessel flanges. The area should be properly ventilated and personal protective equipment, such as goggles and gloves, should be worn. It is also important to follow strict procedures and guidelines to prevent accidents and ensure the structural integrity of the vessel is not compromised.

## 5. Can holes be drilled in pressure vessel flanges after they have been installed?

In some cases, it may be possible to drill holes in pressure vessel flanges after they have been installed. However, this is not recommended as it can compromise the structural integrity of the flange and potentially lead to failures or leaks. It is best to plan and drill all necessary holes before the flange is installed on the vessel.

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