Landing Pipe Variable Wall Thickness Fatigue Resistance

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Solution Overview

Problem

Drill and landing string components face challenges with fatigue failure and notching due to repetitive loading and unloading by gripping slips, making it difficult to manufacture components that can withstand high tensile and compressive loads, bending, and rotation while minimizing weight and hydraulic turbulence.

Innovation Solution

A landing pipe with an integral design and varying tube wall thickness, using high-strength low-alloy steel, and localized heat treatment to achieve balanced mechanical characteristics, reducing weight and enhancing resistance to fatigue and cracking without welds, and maintaining a smooth bore for improved handling and fluid flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If tube wall thickness is increased in the slip area to resist slip crushing and hoop stresses, then strength and resistance to fatigue failure improve, but weight increases

Engineering Contradiction:

Improveresistance to slip crushing and hoop stressesVSAvoidlanding pipe weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The landing pipe features variable wall thickness with a thickened slip area (protector tube) specifically where slips engage, while other portions maintain standard wall thickness. This localized thickening provides enhanced strength and resistance to slip crushing and hoop stresses only where needed, rather than uniformly increasing weight throughout the entire pipe length.

Inventive Principle:

Principle #3Local quality

2Strength

If high-strength low-alloy steel with high Rockwell Hardness is used to increase strength and resistance to slip crushing, then material strength improves, but brittleness increases and resistance to crack initiation and propagation decreases

Engineering Contradiction:

Improveresistance to slip crushingVSAvoidresistance to crack initiation and propagation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies localized heat treatment (such as induction heating) specifically to the slip area to achieve high Rockwell Hardness and resistance to slip crushing. The non-slip areas maintain lower hardness and better ductility, providing a balance between local strength requirements and overall toughness to prevent crack propagation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes heat treatment processes to change the material parameters (hardness, strength, ductility) of the steel in specific regions. By controlling temperature, heating rate, and cooling rate during induction heating, the slip area achieves high strength and hardness while the rest of the pipe maintains more ductile properties.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If an integral design without welds is used to simplify manufacturing and improve reliability, then manufacturing complexity decreases and reliability improves, but the ability to add reinforcement in specific areas is limited

Engineering Contradiction:

Improvemanufacturing simplicity and reliabilityVSAvoidcapacity to provide localized reinforcement

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent achieves localized reinforcement in the integral pipe design by varying wall thickness through controlled deformation processes such as rotary draw bending and localized stretching or rolling. This allows the slip area to have increased wall thickness without requiring separate welded sections, maintaining the benefits of an integral design while providing necessary local strengthening.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution reduces weight, increases part life, and enhances landing operations by minimizing hydraulic turbulence and hang-ups, while maintaining high tensile loading capacity and reducing the time required for pipe setup.

Implementation Method 1

increasing tube wall thickness where slips are applied on a landing pipe increases the landing pipe's resistance to stresses applied by the slips

Methodology Applied

Scientific EffectStress distribution:

Implementation Method 2

localized heat treatment to achieve balanced mechanical characteristics, reducing weight and enhancing resistance to fatigue and cracking

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS11408234B2Landing pipe

Publication Date: 2022.08.09 GRANT PRIDECO LP

AI summary

A landing pipe includes a first tool joint, a second tool joint, and a main section extending from the first tool joint to the second tool joint, the main section having a first portion and a second portion. The first tool joint outer diameter is greater than both the main section first portion outer diameter and the main section second portion outer diameter. The main section third portion wall thickness is greater than the main section second portion wall thickness, and the main section second portion has a length range of 40% to 85% of an overall length of the landing pipe.