High Collapse Service - HC Series

These proprietary Grade designed for wells where high external pressures are anticipated, and Collapse pressures higher than API values are required to be guaranteed.


Steel Grades Properties

Tenaris provides high-collapse-pressure resistant products in grades rated for 80.000 psi. These products have a consistently higher resistance to collapse than the specified in API 5C3 Spec.

Tenaris Actual Results TN 95HC

Based on the more difficult and complex conditions of the oil and gas production, it has been necessary to design collapse products with minimum performance properties higher than the ones obtained with API products. A well casing must have adequate collapse strength to withstand high external pressures without reaching an unstable condition.

The design and fabrication of tubular products for high collapse require special care at some stages of the manufacturing process. One of the key factors is to control closely all processes, so that, appropriate mechanical characteristics and dimensional parameters can be obtained. Therefore, all processes (rolling, heat treatment, sizing and straightening) are designed and closely monitored to produce a tubular body with outstanding characteristics for resisting collapse.

The goal is to have as a result products with guaranteed collapse pressure well above API rates.

There are two critical aspects to be considered during the design and manufacturing of the high collapse tubular.

1. Dimensional tolerances
2. Mechanical properties

Wall thickness variation and ovality are detrimental to collapse pressure and should be held down at minimum values. Therefore, the latest rolling and sizing technology is used in order to obtain high dimensional accuracy.


Mechanical properties

• Low residual stress.
• High true elastic limit
• Fully tempered martensitic structure.


Yield Strength:

High uniformity of yield strength is essential to produce high collapse products with consistent collapse properties. This uniformity is achieved through a careful process control during heat treatment, resulting in a narrow yield strength distribution.


Microstructure homogeneity:

All special products for high collapse resistance have fully tempered martensitic structures by means of a remarkable quenching and high temperature tempering process.


Residual stresses:

Residual stresses impair the collapse properties of tubular. Therefore, hot straightening is carried out to reduce residual stresses. The minimum temperature of 410°C is kept for all grades at the exit of the straightening machine.


Chemical Composition

Chemistry is designed focusing on remarkable hardenability and high tempering temperature. The chemical composition of steels is carefully controlled according to a tight range during the steelmaking process.


Collapse Test

A collapse test is carried out on each production run. Tenaris has its own testing facility, where collapse tests are normally performed. Collapse testing chambers.