Vacuum Insulated Tubing - I-Tubing (VIT)

I-Tubing (VIT) – Vacuum Insulated Tubings with threaded connection

MAJUS is a supplier of vacuum insulated tubing featuring major innovations for the insulation material and for the design of the connection that guarantees together long term thermal performance with an overall U-value less than 0.8 W/(m².K), even at high temperature.

I-tubings factory in Sultanate of Oman
I-tubings factory in Sultanate of Oman

How I-tubing works

Majus I-tubing were designed in order to drastically reduce the heat losses at the junction between tubings where industry consider that 90% of heat losses occur in conventional insulating tubings, leading to overall U-values over 5 W/(m².K) (or 1 BTU/hr-ft²-°F) even if k-value on the body are as low as 0.0026 W/(m.K) (or 0.0015 BTU/hr-ft-°F). Ref.: SPE paper 90151 “The Heat Transfer Characteristics of Vacuum Insulated Tubing

Bayonet connection design

MAJUS unique connection design, called bayonet, contributes to the global thermal performance of the I-Tubing.

The coupling is the weakest thermal point for existing insulated systems. For a classically insulated tubing more than 90% of the heat loss is through the threaded connection. By adding a dedicated bayonet system, the I-tubing dramatically reduces the heat loss at the connection. Indeed the three main heat transfer mechanisms are kept to a minimum at the connection:

  • Convection – Thanks to bayonet geometry, no convection cell is possible as no external fluid can be in contact with the hot surface of the tubing and move to the external environment
  • Conduction - There is vacuum insulation material on each section of the tubing, even above the connection.
  • Radiation - The hot surface of the tubing never faces the external environment as there is vacuum insulation material on each section of the I-tubing, even above the connection.

Why I-tubing instead of standard VIT?

The benefits of the I-Tubings over standard vacuum insulated tubing are a reduced overall heat loss and longer life time:

  • Reduced heat loss - I-Tubing's overall thermal performance is less than 0.8 W/(m².K) (or 0.14 BTU/hr-ft²-°F), 5 to 7 times better than standard VITs. The bayonet connection design of the I-tubing allows to reduce the heat loss at the connection much better than standard connection of VIT. The difference is even more important at high temperature (steam application for example) where the radiation and convection heat transfer mechanisms increase significantly for standard VITs but not for I-tubings.
  • Increased life time - I-tubing vacuum is about 10 000 times higher than the conventional VIT therefore there is no degradation of the insulation performance over time due to outgassing or hydrogen permeation. Outgassing process is the release of gas molecule trapped into material such as the pipes.
  • No hot spot – No hot spot appears on the external wall of the I-tubing, even at the connection.
  • Fits every connection - The bayonet design of the I-tubing fits any kind of tubing and coupling.


This revolutionary vacuum insulated tubing can be used to transport:

  • Oil from the reservoir to the surface while keeping the crude hot and avoiding wax deposition
  • High quality steam downhole

The I-tubing can be used with benefits in several application categories:

  • Production assurance - To ensure the flow of the upward recovered oil or gas. For example, waxy and paraffinic oilfields may require a highly insulated tubings to keep producing. For the gas wells, many studies show the benefit of a high insulation to postpone the gas well self-killing.
    Eg: paraffin or wax deposition, gas well self-killing, hydrate formation
  • Protect the completion - In cold environment or in case of annular pressure build-up, the I-tubing strongly reduces the heat transfer between the transported fluid and the tubing's environment to protect the well integrity.
    Eg: annular pressure build-up, permafrost, cementation cracking, casing dilatation,…
  • Steam injection - To optimize the oil recovery, I-tubing helps maintaining a much better downhole steam quality. Its design have been developed for HPHT conditions: the conducted fluid in the I-tubing can be at a temperature up to 600°F (315°C)
    Eg: SAGD, steam flooding,…

Rig operations with I-tubings in Gabon
Rig operations with I-tubings in Gabon

Long term performance

The overall thermal performance of a VIT is given by the U-value. The U-value is the overall heat transfer coefficient of the system, including the connection. See thermal considerations in the glossary.
Thanks to the technical advantages, the U-Value of the I-Tubing is less than 0.8 W/(m².K) (or 0.14 BTU/hr-ft²-°F). This performance remain constant over time.

U-Value in W/(m2.K) Day 1 Long term
Comparison of thermal performance between I-Tubing and Standard VIT
I-Tubing 0.8 0.8
Standard VIT > 6.0 if connection non insulated
> 3.0 otherwise
High sensibility to temperature

Thermal test of I-Tubing at high temperature
Thermal test of I-Tubing at high temperature


The insulation material, Izoflex, gives its best thermal performance with a soft level vacuum (low to medium vacuum): 10 000 higher than the vacuum used for standard VIT (high vacuum). This specificity of the Izoflex leads to a cost less characteristic: no degradation of the thermal performance over time due to outgassing or hydrogen permeation. Moreover, this soft vacuum is easy to achieve in industrial conditions with proper QA/QC control. As a comparison, the vacuum used in the I-Tubing is equivalent to the vacuum used in an incandescent light bulb.

As the outgassing or hydrogen permeation has no effect on this level and quality of vacuum, there is no need for getters.