• For Transfer of Liquefied Gases and Extreme-Temperature Fluids.
• Flexible SIVL is a highly developed transfer system for any extreme-temperature fluid and is most commonly used for the transfer of liquid gases.
• Flexible SIVL is 10 to 30 times more efficient in reducing heat flow than even the best conventionally lagged pipes; saving you money in operation costs.
• Flexible SIVL is manufactured almost entirely of high grade stainless steel; a durable asset saving you money in maintenance.
• The line has a hygienic finish (polished stainless steel) and is therefore eminently suitable for use in food, medical and research establishments as well as in general industry.

Applications
Flexible superinsulated vacuum lines have many applications. The following are a few examples for which liquid helium and nitrogen flexible lines have already been supplied:

• Trials and temporary installations.
• Transfers from mobile bulk tanks (liquid helium).
• Supply of cryogens to moving or vibrating reservoirs.
• Installation in hostile environments where lines need to be moved away or aside.
• Routing pipe work through congested areas where the installation of rigid lines would be difficult, if not impossible.

Servicing Advantages
The line is virtually maintenance free (no crumbling insulation to be replaced every year or so). Any deterioration in vacuum will only affect that section and not the whole line.

Construction and Testing
The line is virtually maintenance free (no crumbling insulation to be replaced every year or so). No need for continuous evacuation and therefore no vacuum pump maintenance.

• Superinsulation is applied to clean factory conditions.
• Line sections are evacutated using large diffusion pumps fitted with liquid nitrogen cold traps.
• After satisfactory completion of pumping, each flexible line is helium leak tested, using a mass spectrometer, to < 3 x 10^-9 std cc/sec air equivalent.
• Line sections are pneumatically pressure tested to a minimum of 10 % above design pressure.
• Each flexible line is cold tested before removal from the diffusion pump. A second helium leak test is then performed at 77 K. Line sections are thus thoroughly cold tested before they leave the factory.

Specials / Non-Standard
This section sets out our standard range, but we would welcome the opportunity to quote against your specific requirement and believe you will find our 'one-off' prices very competitive.

Considerations to be taken into account
There are, however, other factors to be taken into account when considering using flexible rather than rigid lines:

• For a given line diameter the heat loss will be greater with a flexible line.
• Higher driving pressures (typically 30% greater) are required to overcome the additional frictional flow losses in a flexible line.

Standard Size Range

Table 2: Standard Size Range
Line bore size-----------Line outer diameter------Typical heat leak------Typical flow rates
(mm)-----------------------(mm)---------------------------(W/m)---------------------(kg/hr)
10---------------------------56-------------------------------1.00---------------------------150
13---------------------------67-------------------------------1.25---------------------------300
20---------------------------85-------------------------------1.60---------------------------900
25---------------------------95-------------------------------2.50-------------------------2500
Spool lengths up to 20 metres

Flexible Hoses (for vacuum use, but with over pressure failure modes)
Our Vacuum Pressure range of Flexible Hoses are designed for vacuum applications. The weld between the end fitting and the flexible is a clean back purged edge weld with minimal trapped volumes. The flexible is oxygen degreased prior to assembly. To avoid 'loose fitting' outer braids on larger sizes, the flexible hose is braided when it is at its evacuated length. It is because of this, that the overall lengths listed will be accurate to + 50 mm. The hoses will be helium leak tested to 3 x 10^-9 std cc/sec prior to braiding. After braiding, the hose will be subjected to a standard strength test of 10 bar (pneumatically with dry nitrogen).

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