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VACUUM INSULATED TUBING

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1. Coupling 2. Optional Seal ring 3. Insulation sleeve 4. Insert
5. Outer tube 6. Insulating material 7. Inner tube

Vacuum Insulated Tubing (VIT) was first introduced in Alaskan North Slope Oil Fields to help protect the environment. Permafrost extends as much as 600 meters from surface and rarely melts. Introduction of warm fluids and resulting transfer of heat had a damaging effect on the surrounding area. To help protect the permafrost and the environment, Vacuum Insulated tubing was introduced.
VIT technology has now moved to enhance the steam injection process in SAGD type oil wells as well as in reducing wax buildup in producing wells. .
In SAGD application, VIT allows for delivered steam to the injection point at a higher temperature resulting in a more cost effective operation.
For the prevention of Paraffin or wax buildup which occurs when the producing fluid falls below the cloud point, VIT maintains the fluid temperature and reduces the occurrence of paraffin buildup thus reduction costly well shut down and production loss.

The pre-stress technology will compensate the tubing expansion caused by temperature difference between the inner and the outer tubes so as to ensure reliable operation under high temp.
Gas absorbing materials are packed inside the annulus to clean up harmful gas and maintain good insulating property in service.

Process:

The first step in fabricating VIT is to cut both tubes to the desired length, up to Range 3 or 12 meters but normally Range 2 or 9-10 meters. The tubing material is typically carbon steel, but 13-chrome material is also used.
During assembly, a vacuum port is drilled into the outer tube, and both tubes are blasted to remove scale. The inner tube is then wrapped with foil and hydrogen-scavenging ©"getter" is
installed. Next, centralizers are mounted on the inner tube, which is subsequently run into the outer tube and fillet-welded in place. A vacuum pump is then attached to a port in the outer tube, and the entire assembly is run into a convection oven and heated.
The heat activates the getter, which vaporizes any contaminants in the annular space. The annulus is then voided by the vacuum pump. Upon completion of this stage, the vacuum pump is removed, the port is plugged and welded, and the thermal efficiency of the assembly is measured to verify that the desired thermal properties were achieved. The completed assembly is threaded (with premium threads, if desired) and shipped to its destination.

© A getter is a deposit of reactive material that is placed inside a vacuum system, for the purpose of completing and maintaining the vacuum. When gas molecules strike the getter material, they combine with it chemically or by adsorption. Thus the getter removes small amounts of gas from the evacuated space.

Availability:

OD	ID	Connection	Coupling OD	Insulating Grade *	Pipe Grade
177.8	139.7	API or Semi Premium	194.5	B, C	J, N, L, P
139.7	88.9	API or Semi Premium	153.7	D, E	J, N, L, P
139.7	101.6	API or Semi Premium	153.7	D, E	J, N, L, P
127	76	API or Semi Premium	141.3	C, D, E	J, N, L, P
114.3	62	API or Semi Premium	127	C, D, E	J, N, L, P
114.3	76	API or Semi Premium	127	C, D, E	J, N, L, P
88.9	40.9	API or Semi Premium	108	B, C, D, E	J, N, L, P

COFFICENT OF HEAT CONDUCTIVITY

INSULATING GRADES	B	C	D	E
k-factor (λ)(W/m.℃)	0.06＞λ≥0.04	0.04＞λ≥0.02	0.02＞λ≥0.006	0.006＞λ≥0.002

Vacuum-insulated tubing can help prevent problems by reducing the outward movement of heat. In VIT, fluid temperature loss is approximately 6 Celsius degrees over 1,500 meters, compared to a loss of 45 Celsius degrees or more over the same length of conventional tubing.