What is a LPG cylinder?

It is a container in which propane and butane are mixed in certain quantities so that they can be used a fuel for various applications.

What is LPG cylinder made of?

As per the Bureau of Indian Standards, the LPG cylinders are made from carbon steel. Wall thickness is a major aspect that needs to be considered while designing a cylinder. The factors that affect the thickness of the wall are:

  • Cylinder test pressure
  • Shape of cylinder dome
  • Length of straight flange
  • Outer diameter of cylinder
  • Ratio of domed end diameter to height
  • Yield strength of material
  • Dishing radius
  • Weld joint factor
  • Knuckle radius

What is the pressure inside and LPG cylinder?

LPG cylinders are thin pressure vessels. When the cylinders are filled with LPG, a pressure ranging from 12 – 18 bar gets created inside the LPG cylinder.

What are stresses inside the cylinder?

Due to the pressure in the cylinder, stresses get created. They are of two types:

  • Circumferential Stresses
  • Longitudinal Stresses

Both are tensile stresses. During analysis it is often found that the circumferential stress is usually more than the longitudinal stress. Hence, the circumferential stress is a major principle stress and is often blamed for failures in the cylinder.

Why is the welding on a cylinder circumferential?

Circumferential stress is a major principal stress and longitudinal stress is a minor principal stress. If the major principal stress exceeds the strength of the material, there is a chance of failure. Thus, we need to keep it minimum.

If we weld longitudinally, the circumferential stress will rise. On the other hand, if we weld circumstantially, the longitudinal stress will rise. We can afford the longitudinal stress to rise as it is a minor principle stress. Rising the circumferential stress will lead to failures. Thus, welding done is circumferential.

What welding is done on an LPG cylinder?

The welding done on the cylinder is known as Submerged Arc – Welding (SAW). In SAW the strength of the weld junction is more than the strength of the parent material. The strength is more in order to prevent leakage which can be catastrophic. It is called SAW due to the welding electrode being submerged into the flux in the form on grains. The flux is poured via the feed hopper. The slag that floats on the top is later removed.

Why are most LPG cylinders in red color?

The color red is known to have the highest wavelength in the visible spectrum, thus, making it visible from a long distance. It is a color usually associated with anything that is flammable.  However, cylinders (especially non – commercial) are painted in oxford blue with a red band of 4 inches in the middle of the cylinder. This is done due to stop diversion of cylinders.