Nanofiltration (NF) is a de novo class of membrane filtrations with unique properties ranging from ultrafiltration to reverse osmosis. Thanks to their high removal performance, NF membranes have gained increasing attention from both academia and industry for various applications, especially in water and wastewater treatment and desalination. However, the NF process still requires further improvement in terms of selectivity, separation efficiency, membrane fabrication, operation requirements, and sustainability.


This Special Issue on “Nanofiltration Membranes: Recent Advances and Environmental Applications” of the Membranes seeks to include but is not limited to recent progress in emerging NF membranes fabrication and modification, polymeric and ceramic NF membrane, hybrid and composite NF membranes, organic solvent NF, positively charged NF membranes, NF module and process design, NF removal mechanisms, fouling mitigation strategies, new environmental applications of NF, and predictive modelling of NF membrane processes. Authors are invited to submit their latest original results as full papers or short communications. Furthermore, state-of-the-art and critical reviews and analysis papers are welcome.


Advantages of GRE pipes


Glass Reinforced Epoxy or GRE pipes are a valid alternative to carbon steel pipes especially for corrosive, aggressive and normal environments.

GRE pipe technology is based on the Discontinuous Filament Winding process using high strength fiberglass (E-glass) and amine cured epoxy resin as basic material. Numerically controlled machines manufacture the product on a mandrel according to the cross section filament winding process. The continuous glass fibers are helically wound at predetermined angles and bonded with the epoxy resin.

Lightweight and easy to handle and install GRE pipes have a smooth internal surface that reduces friction and enables a high pipe flow capacity. Low thermal conductivity of GRE pipes in comparison to steel (only 1% of steel values), minimizes the cost of insulation and the heat loss. Another major benefit of GRE pipes is that once installed they are virtually maintenance-free.

GRE pipe is well suited for environments where the corrosion resistance at competitive prices is required.

GRE pipes offer a unique combination of high mechanical, thermal and chemical resistance which is obtained by the selection of high performance components and a proper design of the structure. The inner liner, which is made by a resin rich layer reinforced with C-glass or synthetic veil, guarantees the pipe water tightness, its chemical and temperature resistance. The mechanical resistant layer is composed of successive layers of pre-stressed glass roving impregnated with epoxy resin and orientated with a precise, predetermined angle selected in order to achieve the properties required. The resin and the hardener system are selected with the consideration of the combination of properties required from the finished product. The glass reinforcement in the form of continuous roving is chosen base on its compatibility with epoxy resin. It is applied on the rotating mandrel following the hoop (radial) winding pattern combined with a helical winding pattern at an angle ranging from 45?° to 90?°.

Glass tape or unidirectional reinforcements can be used to obtain local reinforcement. An external resin coating reinforced with a synthetic veil adds a finish to the pipe. Should weathering be a problem a UV inhibitor will be added to the coating.

GRE pipes are generally manufactured with an integral joint, which means that the socket (for bonding, lock, or thread) is produced simultaneously with the pipe body by winding on a specially designed metallic mould fixed at one end of the mandrel. The pipes are wound on precisely machined steel mandrels, the mandrel is extracted only when the pipe is cured.




ADVANTAGES


Wide range of diameters from 1 " (25mm) up to and including 54 " (1400 mm).


Standard lengths of 12 m.


Adhesive, locked bell/spigot, lamination and flanged jointing systems.


Anti corrosion system


Long life (50 years) + zero maintenance = low life cycle cost.


UV Resistant - can be safely installed above-ground.


Conductive pipe and fittings are available.


Fast, low cost assembly due to light weight and simple jointing techniques.


Lighter support needed for above-ground systems.


Low Hazen williams number due to the smoother internal surface.





GENERAL CHARACTERISTICS OF THE PIPING


Excellent resistance to corrosion and long service life.


Superior Flow characteristics.


Low paraffin's and solid build-up.


Installation cost much lower than steel.


Installation unaffected by weather conditions.


The pipes weight about ?? the weight of steel.


Fast and reliable installation. API 8 RD EUE Threads and 4 TPI available.


Operational pressures in line pipe, tubing and casing up to 3500 PSI.


Exceptional performance against pressures and high capacity load.


USES OF GRE


Transport lines.


Fire Fighting networks.


Line for chemical disposal.


Injections lines.


Lines for gathering and gas transportation.


Line for universal insolutions and water injection in mines.


Acid transportation.


Line for recirculation.


Production wells, Tubing and casing.


Line for chemical transportation.


Water injection, tubing and casing.


Line for disposal formation waters.


The Early Rotor Blades


Early helicopters like the famous Bell 47 came with main rotor blades made of wood. The inherent characteristic of wood being strong and flexible provided the perfect material for early rotor blade designs.


There were problems however as wood can easily be damaged by woodpeckers, dust and stones, and even rain causing the blade to swell leading to severe vibrations from an out of balance rotor system.


As the realization of the versatility of the helicopter become more popular, the design and evolution of the airframe and the rotor blades began to move forward.


Materials Development


A rotor blade needs to be strong but also very flexible. You have probably seen that when a helicopter is parked the main rotor blades droop down, but in flight centrifugal force keeps them flat. Not only that, but the blades also flex in flight, especially when affected by turbulence and they need to be able to withstand these loads as well as keeping the helicopter in the air.


To be able to withstand these stresses placed on the blades they need to be designed to be strong in certain areas, but yet flexible in others. Although wood is great at doing this they are limited to the weight they can lift and the speed at which the tips can rotate. This is where new materials were needed.


One of the first advances into rotor blade design was the skinning of the blade’s leading edge with corrosion-resistant steel to aid in erosion control, especially towards the tips of the rotor blade where it is moving the fastest.


The Hiller UH -12B was one of these aircraft to adopt such a design on its blades during the 1950’s.


Metals


As testing and development into metals really began to take stride it became inevitable that rotor blades would find themselves made of them.


As metals solved some of the problems presented in wooden blades, they presented their own. Constant flexing of certain metals over time can cause it to break. Think of what happens to a paperclip when you twist it back and forth. The other problem with metal is that a crack can rapidly spread causing catastrophic failure – Which is not generally welcomed by pilots!


This was one of the first reasons that rotor blades started to have a time limit on their use. Until this point, wooden blades were considered to last indefinitely!


Honeycombs


The addition of honeycomb technology into rotor blades really helped to improve the design and lifespan of a rotor blade. Used in conjunction with other metals, rotor blades can be produced strong, flexible, light, and cheaper than their advanced composite younger brothers.


To ensure the long-term safe operation of the FRP membrane housing, please observe the following regulations and recommendations:


1. The shrinkage expansion rate of the FRP membrane housing is relatively small. Please observe the rated design pressure index during use. Operate it within the allowable pressure range.Long time overpressure operaton is strictly forbidden!


2. The service temperature of FRP membrane housing is generally from ﹣7 ℃ to 49 ℃. It is strictly forbidden to work under the condition beyond this temperature range.


3. The back pressure of the two-end permeate water outlet shall not exceed 125 PSI.


4. Strictly abide by the pressure level of each medium, such as clean water, sewage, seawater, etc. If you use water with special media, please contact our company in advance to avoid accidents.


5. When the RO system is working or there is pressure in the frp membrane housing, it is strictly prohibited to knock, disassemble or move the membrane housings. The surrounding vibration source environment must be strictly controlled.


6. It is strictly forbiden to apply pressure or gravity to the upper part of the membrane shell, or to its corresponding accessories.


7. In order to ensure the inner surface of the fiberglass membrane housing clean, manufacturer use a neutral cleaning solution to clean. It is strictly forbidden to use concentrated hydrochloric acid, concentrated sulfuric acid, etc. as cleaning fluid.


The above is all the content that the editor introduces to everyone, we need to maintain and clean the FRP membrane housings regularly during use.