SEMIFLEX®
is a bendable piping system consisting of two concentric,
corrugated tubes separated by a Teflon spacer. The space
between the tubes is continuously evacuated by a pump
to provide “dynamic vacuum” insulation that
will not deteriorate.
SEMIFLEX® is available in five different sizes in
copper or stainless steel. The outside is protected
with polyethylen coating.
SEMIFLEX® provides fast cool-down, constant liquid quality and trouble free operation.
With the temperature of the outer tube being only some degrees below ambient temperature the system is free of moisture and ice.
SEMIFLEX® is a system which allows for any length of vacuum insulated pipe, outdoor and indoor. Tees, crosses, bayonets, end traps, vents and phase separators allow any system configuration and guarantee that SEMIFLEX® is easily adjustable to any modification.
Advantages ofSEMIFLEX®
Cost Savings
With SEMIFLEX® you enjoy significant reductions in LN2 consumption on a continuous basis since SEMIFLEX® Systems have a very low cool down and steady state heat loss.
Easy Installation
SEMIFLEX® systems are designed for quick low-cost installation that does not interfere with production. Factory fabricated and tested, the pipe is simply hung and connected to equipment. The bendable nature of SEMIFLEX® pipe greatly simplifies installation. There are no critical field joints. Bayonet connections avoid costly welding of sections.
Minimal Maintenance
SEMIFLEX® pipe requires no maintenance. The MlCROtorr 11 vacuum pumping station needs only routine care, easily handled by your own personnel. Since the pipe's vacuum insulation is dynamically maintained, it does not deteriorate with time.
Worldwide service support
With offices throughout the world and a service network in Europe VBS Europe and VBC provide support at each of your facilities on a timely and personal basis.
Points to consider inLN2 Pipe System Design
Heat losses
In any vacuum insulated pipe system, the LN2 losses attributable to heat leak in the pipe are miniscule compared to the losses which occur in the system as a whole. The major portion of heat loss occurs from the following factors:
Tank connection
In a typical pipe system connected to a bulk storage tank, the interface between the tank and the vacuum insulated pipe is bare copper pipe with a main shut off valve and safety relief valve assembly. This connection will normally have a loss rate of 2 to 7 kg of LN2 per hour or more. Losses here flow through the entire pipe system as gas (GN2) along with the liquid. SEMIFLEX® systems can effectively eliminate tank connection losses by using a vacuum insulated tank bayonet and valve. Equipment connection
This part of the system, between the end of the vacuum insulated pipe and the actual use point, is typically copper tube with a shut off valve, safety relief valve assembly, and a solenoid valve connected to a sensor control. Losses average 1 to 4 kg of LN2 per hour. To minimize these losses, controls should be configured so that connections are active only to satisfy equipment requirements, and not constantly. SEMIFLEX® systems minimize equipment connection losses.
Flash loss "Flash" is caused by the reduction of pressure when a valve is opened to withdraw liquid or when liquid is passed through a pressure reducing valve of any kind. At 7 bar, flash losses approach 30% of liquid used. Since SEMIFLEX® systems substantially reduce overall consumption of LN2, flash losses are also minimized.
Two phase flow
Even a small heat leak in an LN2 delivery system generates a large volume of gas. At – 196°C, LN2 converts to GN2 at a ratio of 177 to 1; as LN2 warms to ambient temperatures, the ratio approaches 700 to 1. Since all LN2 pipe systems will have some flash loss and pipe heat leak, two phase flow (liquid/gas) will occur in the pipe.
For many applications, however, a supply of LN2 in pure liquid form is preferable. Only SEMIFLEX®/Triax Systems are capable of completely eliminating two phase flow of LN2 to use points.
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2003 - Vacuum Barrier Systems - All right reserved
