Ovality in Pipes. Abstract— Ovality in Pipes. Ovality generally known as ‘Out of Roundness’ is one of the most common defects in pipe manufacturing. Ovality in early stages makes manufacturing process time consuming and less efficient. After dispatching, because of improper handling, ovality turns into barrier of proper welding of two pipes on site. In this paper, there is inclusion of causes of ovality, stages of ovality, drawbacks of oval pipes, manufacturing difficulties due to ovality and how to control it is included.
Keywords— Ovality, L-SAW pipe, Spiral welded pipe, Expander, Hydraulic press, Cross-weld.
I. INTRODUCTION
In API 5L out-of-roundness is defined as the difference between the maximum (or minimum diameter) and the nominal diameter, expressed as a percentage of the nominal diameter. In ISO 3162, out-of-roundness is defined as the difference between the maximum and minimum diameters, expressed as a percentage of the nominal diameter. Ovality in Pipes. Assuming symmetric ovality, the API 5L definition gives half the percentage ovality of the ISO 3162 definition. Ovality or ‘out of roundness’ is one of the common defects while manufacturing L-SAW or Spiral welded pipes. Which in turns of excess manufacturing work to remove it or directly turns into rejection of product. It is an undesired phenomenon because of which many manufacturing operations cannot be done properly and ovality in dispatched pipe makes it unsuitable for welding with other pipes. A. OVALITY Fig.1. Ovality Generally, ovality is measured by difference between maximum diameter and minimum diameter (ID or OD). According to the utility and requirement it has some acceptance limit like 4mm, 5mm to 6mm. Beyond this, product is treated as rejection or rework. Acceptable ovality of a pipe should be determined by user, but as a guideline, 5% is a typical acceptance criterion, and ASME defaults to 8% [1] . Ovality % = Max OD – Min OD X 100 Nominal OD
B. GENERATION OF OVALITY
Following are the main causes of ovality in pipes –
If all the rollers at pipe mill are not inclined at proper
angle with respect to each other then there will be
chances of generation of ovality.
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