FLEXIBLE METALLIC AND PTFE HOSES
FLEXIBLE METALLIC HOSES
Flexible metallic hoses are obtained from drawn tubes with or without a longitudinal weld. They are placed on special machines that mechanically or hydraulically produce parallel or helical corrugations depending on the use to which the hose will be put.
It is of fundamental importance that flexible metallic hoses destined to withstand extremely high pressure be covered externally with one or more braids as the corrugation alone can only support relatively low pressure.
HOSES MADE WITH PTFE
PTFE hoses offer the ideal solution for difficult and hazardous cases, as PFTE, with its unique combination of low friction and expansion coefficients, chemical inertia, dielectric properties, resistance to heat and humidity, non-stick surface and high resistance, is the best of all polymers.
These hoses have been tested for use in presence of oxygen and hydrogen, heat shock, and for the elimination of static energy. They can be used in temperatures ranging from -55°C to 240°C, with peaks of 260°C.
G-FLEX HOSES: technical note
G-FLEX hoses are guaranteed to last and are extremely reliable. However particular attention must be paid when fitting them, and the instructions must be closely followed. The Giorgi technical team is always available to provide advice or assistance in case of doubt.
MATERIAL AND PRODUCTION CHECKS
As an ISO 9001 certified company with PED homologation, Giorgi Engineering analyzes all materials entering its production facilities, checking that quality and specifications conform to the clients’ requirements.
Each individual component can be individuated in the production facility at each step in the production cycle.
The pressure or acceptance test is carried out on Giorgi Engineering’s premises before the order is delivered to the client.
Every component is tested either with the pneumatic system at 6 bar, or the hydraulic system, applying a pressure 1.5 times heavier than the operating pressure. If testing at higher pressures is required, this must be indicated during the definition of the offer.
RADIUS OF CURVATURE
This is the radius on which the axis of the tube can be continuously and constantly bent without causing the steel to crack or the corrugations to lose their form.
The bend radius must be maintained for all applications that require static movement, and the radius of curvature applied for dynamic movements.
Never twist flexible hoses, either folded or corrugated. Twisting can cause a modification of the diameter of folded hoses, and in standard folded hoses may cause unclinching. Always follow the technical assembly instructions for corrugated hoses.
High fluid speed may cause resonance inside flexible hoses, reducing their service life; 5 m/sec is the recommended speed. Dry gas inside flexible hoses without external braids may safely flow at 30 m/sec and at 45 m/sec in braided hoses.
Rated pressure is calculated at room temperature; the safety factor is four times the burst pressure.
PTFE FLEXIBLE HOSES
CLEANING AND STERILIZATION
PTFE hoses are chemically resistant to all CIP, SIP and autoclave systems. If electrostatic charges develop during cleaning, which may happen when solvents, steam or hot water are used, a PTFE anti-static should be adopted.
PTFE hoses reinforced with a sleeve of stainless steel braiding are resistant to autoclaving as long as the operating conditions of the flexible hose are respected. With additional coverings of EPDM or silicone, they can withstand 300 30 minute cycles at maximum temperatures of 121°C and 135°C respectively.
USE WITH ALKALI METALS, HALOGENS AND CHEMICALS CONTAINING HALOGEN
PTFE hose liners react chemically with chlorine, fluorine, chlorine trifluoride and alkali metals. It must be remembered that if a PTFE lined hose is used for chlorine and bromine, the fluids will tend to permeate the liner, allowing traces to combine with the atmosphere and corrode the braid or rubber outer sleeve. Other fluids such as hydrogen fluoride, hydrogen chloride, phosgene (carbonyl chloride), carbon tetrachloride will also permeate the PTFE hose liner.
GAS AND FLUID CYCLES
Some applications entail alternating cycles of gases and fluids, which normally involve brusque changes in temperature or sharp increases in pressure. This type of usage will damage any type of hose, including those in PTFE.
Hoses must be connected using the appropriate instruments. When tightening the connections, it is important not to damage the fittings, particularly if the liner protrudes from the extremity. If the hose is to be used for critical or hazardous substances, it must be tested before being put into use.