High-quality String Filter
As a top-rated string filter manufacture in China, Filson has the ability to offer you customized string filters. Our string filter is durable, heat-resistant and in high filtration efficiency.
- Customized available in materials and sizes
- High quality certified by FDA standards
- Reliable and quick delivery
- Stainless steel and polypropylene as center core
What is String Filter
Filson string filter, also known as string wound filter cartridge or string wound water filter cartridge, is mainly made of durable threads to remove rust, dirt or sediments. And the material of core is PP or stainless steel to crate a robust structure.
With designed micron rating ranging from 0.5 to 200 micron and consistent winding process, Filson string filter has huge flow rate up to 30 gpm at 4.5’’ diameter. More importantly, our string filter can retain efficiency around 99.9% to remove most unwanted particles.
Comparing with stainless steel filter or sintered stainless steel filter, Filson string filter provides an economical solution on both domestic and commercial filtration. It can be used in absolute and deep filtration with excellent chemical property and compatibility.
Filson string filter has a variety of types, including fiberglass string wound filter, cotton string wound filter, PP yarn string wound filter, nylon string wound filter, 5 micron string wound sediment filter, etc. You can select from them based on your unique application.
String Filter Categories
Mainly made of anti-heat fiberglass material, Filson fiberglass string wound filter can resist high temperature up to 400℃. Having excellent insulation and strong mechanical strength, our fiberglass string wound filter can filter liquids with high corrosion, acid and alkali.
Filson provides both bleached and natural cotton to manufacture cotton string wound filter in order to meet your different application needs. As bleached cotton is certified by FDA standards, our products can be widely used in distilled water, beverages, vegetable oils or other fields.
Filson PP yarn string wound filter is usually fabricated with standard polypropylene and fibrillated polypropylene, featuring in good acid and alkali resistance. Besides, since fibrillated PP has the lowest static propensity, our filter is good at filtering ultrapure liquids, electronics, etc.
Having nominal 5 micron rate, Filson 5 micron string wound sediment filter has high efficiency in capturing sand, rust, silt or other sediments. Mainly made of nylon, cotton and fiber glass, our filter has high temperature resistance and anti-rust capability in moisture condition.
String Filter Outstanding Benefits
Utilizing standard materials, the designed lifespan of our string filter is 6 months. But it depends on the contamination and maintenance of your filtered liquids.
Due to its good compatibility and customized materials, our string filter offers wide usages from food&beverage to water filtration, from chemical to electronics industry.
Filson string filter features in high heat resistance. For example, fiberglass can withstand 400℃, polypropylene of 180℃, cotton of 160℃ and polyester of 121℃.
Since Filson has good relationship with DHL/Fedex/TNT or other deliveries, we can deliver string your string filters in a quick and economical way.
String Filter Advantages
By using Filson string filter, you may obtain following advantages:
- Materials certified by FDA without BPA, toxic or odor
- Customized materials and sizes suitable for your filtration system
- 222 or 226 DOE end caps available
- No chemical additives, minimum pollution to filtered liquids
- Continuous strings to stop media migrating
- Allowable to clean for long service life and replace every 6 months
- Twice higher dirt-holding capacity then conventional filters
- Dense inner layers and loose outer layers to improve filtration process
- Experienced specialists and skilled workers
String Filter Technical Features
Filson string filter provides an effective and reliable solution with following characteristics:
- Multiple materials available based on your requirements
- High temperature resistance up to 400℃ with stainless steel or fiberglass
- Superior dirt-holding capacity up to 20000 gallons
- Robust construction to withstand lower differential pressure of 2.5 bar
- Consistent winding process for stable filtration efficiency
- High corrosion resistance to filter acid and alkali liquids
- Good chemical compatibility for most fluids, solvents and chemicals
- 100% polypropylene with lower cost
String Filter Working Principle
Filson string filter has a gradient density with tighter core layer and lighter outer layer.
When water or other liquids passes through filter cartridge, bigger particles will be captured at first.
Then, smaller sediments can be filtered out at each layer with liquids entering cartridge from outside.
Finally, filtered clear liquids will enter the core of string filter and flow out.
In fact, the accuracy of string filter depends on the tightness of the string. The tighter the line, the accuracy the filter is.
Why Choose Filson String Filter
Filson string filter usually has a PP or stainless steel core to resist high heat, corrosion and acid condition. Besides, our string filter fits standard filter housings with the length from 5’’ to 40’’ and has twice greater dirt-holding capacity of 20000 gallons than conventional ones.
To provide you high-quality string filter, Filson controls the production process strictly and chooses standard materials certified by FDA. In addition, our filter undergoes various tests before transportation, such as destructive test, bubble point test, pressure hold test or diffusion test.
As a one-stop string filter manufacturer in China, you can not only find various string filters in Filson, but also standard end fittings like 222 or 226 DOE end caps and gaskets to complete your filtration system.
Do your still have questions about Filson string filter? Please contact with our technicians immediately!
- Core Material: stainless steel 304/316L, polypropylene, tinned steel
- Micron Rating: from 0.5 to 200 micron
- Filtration Efficiency: around 99.9%
- Common Length: 5’’, 10’’, 20’’, 30’’, 40’’
- Inner Diameter: 28mm
- Outer Diameter: 62 – 114mm
- Maximum Operating Temperature: 400℃
- Flow Rate: up to 30 GPM for a diameter of 4.5’’
- Connection: thread, flange
For different applications and design, you can choose material from the listed substances:
- Glass fiber
- Natural cotton
- Bleached cotton
String Filter Applications
As an economical solution in filtering industrial oil, our string filter can provide huge capacity up to 20000 gallons. And you can use Filson string filter in many applications, such as desalination of seawater, filtration of hydraulic, lubricating, cutting and other industrial oil.
Filson string filter can work normally under corrosive environment, like sulphuric acid, iodides, chlorides, etc. Therefore, our string water filter is suitable for all kinds of water treatment, including laser cooling water filtration, ultrasonic cleaning liquids or pre-filtration of RO.
String Filter: The Ultimate FAQ Guide
I know you’re looking for an efficient and reliable string filter.
That’s why this guide will answer all questions you have been asking about string filters.
So, before importing string filters, read this guide.
This is a filter that is capable of eliminating rust, dirt, and other sediments from water by using fibers.
It is considerably cheap, offers good filtration, and has a strong resistance to chemicals.
The string material can be from nylon, polyester, cotton, etc.
It wraps on a center core like stainless steel or polypropylene.
String wound cartridge filters date back several years.
The first one was sold in the United States in the mid-1930s.
The construction was a woven wire mesh bound in cotton wool, that was in a diamond pattern.
The edges of the diamond forms were the key points at which the contaminants would stick.
This was rather than filtering the sand through the entire formation.
Regular cartridges are built from ‘roving’ or ‘friction spun’ fiber.
Also, considerations like media displacement and chemical leaching have been among the main drawbacks to the efficacy of cartridges.
With recent innovation in filter media for the production of string wound cartridges, issues such as media migration and chemical leaching are on the minimum.
Filter cartridges, consisting of cotton yarn materials and metal frames, came about in the mid-1930s.
By the late 1970s, polypropylene (PP) core cartridges and yarn were becoming popular.
This is since they had a wide range of chemical resistance and one could use it in many applications.
Also, they could capture and resist the growth of microorganisms.
This era of string wound cartridge filters usually uses roving rather than conventional yarns.
These were rolls that twist or fiber strands that were more budget-friendly.
Also, the lifespan of the filter cartridge went up.
This is because more water was flowing through it easily.
In subsequent years, ‘friction spun’ wool took over.
The friction spun wool is only similar in appearance to roving but is relatively bigger and heavier.
The result of this is an increase in dirt-holding capability and lower resistance to fluid movement.
Several industries use this filter cartridge in cleaning water.
- Food and beverage industries
- Water filtration
- Beverage processing filtration
- Edible oil
- Electronic industries
- Pure water
- Organic solvents
- Printed circuit board
- Chemical and petroleum industries
- Pre-filtration of RO/DI
- Photographic washing liquids
- Filtration of alkali and acids
- Raw acrylic materials
- Chemical filtration
- Industrial oil
The applications include:
- Desalination of seawater
- Filtration of power plant condensation water
- Plating bath filtration
- Filtration of hydraulic, lubricating, cutting, and other industrial oil
- Pharmaceutical industries
- Filtration of syrup, alcohol, injections, etc.
- Preparation water filtration
- VC raw materials
- Other uses
- Laser cooling water filtration
- Filtration of electroplating liquids
- Ultrasonic cleaning liquids.
The string that goes around the core forms a gradient density in a string would cartridge filter.
Also, the core of the string wound filter cartridge is tighter and the exterior is lighter.
The light outer weaving makes it possible to filter out large contaminants first.
Then as the water continues to pass through the string, fine sediments get caught in each layer.
The winding technique and the specific thickness of the string wound cartridge filter will enhance the dust holding capability.
Also, it will lengthen the service life and the efficiency of the string wound cartridge filter.
The accuracy of the string would cartridge filter depends on the tightness of the string.
One can control the machine to ensure the inside of the string is tight and the outside is loose.
Water with contaminants will pass via the string wound and as it passes, contaminants remain behind.
The clean water will then pass through and enter the core of the string wound cartridge filter.
It then exits the filter as more water gets in to undergo filtration.
String-wound cartridge filters originate from the new media that provides an efficient and cost-effective solution.
The advantages include:
- The spinning method ensures that no chemicals leach in during the filtration process.
- Also, the string wound will allow no media to migrate since it has continuous filaments.
- The filter has high structural integrity thus the media will not move therefore offering an impressive knife-edge sealing.
- Besides, it has an impressive solid to void ratio which enhances the dirt holding capability.
- The dirty liquid will flow via the whole string wound cartridge filter as there is a low-pressure drop.
- Also, the sturdy and firm media configuration will enhance the resistance to the dirt unloading.
- A string would cartridge filter will offer more consistent performance.
- Also, it improves the filtration process as the inner layers of the strings are dense and the outer layers are loose.
These features and specifications may vary from one string wound cartridge filter to the other.
The technical features include:
- A maximum differential pressure of 2.5 bar.
- An inner diameter of 28 mm and an outer diameter of between 62 mm and 114 mm.
- The length of the string wound cartridge filter can be 5, 10, 20, 30, or 40 inches.
- Also, it has a filter rating of between 0.5 μm and 150 μm with the option of customizing on request.
- The maximum working temperature of cotton is 160 °C, polypropylene is 180 °C, polyester is 121 °C, and fiberglass is 400 °C.
- A maximum flow rate of 5 to 28 GPM and 10 to 30 GPM for a diameter of 2.5 and 4.5 inches respectively.
- Besides, it comes in a wide array of micron ratings.
On the other hand, the specifications of a string wound cartridge filter are:
- It has a large dirt holding capability and is also durable.
- Besides, it offers an absolute and depth filtration process.
- Also, one can customize the configuration and the particle retention.
- The end caps or O-rings are some available options you can include in the filter.
- Also, they conform to Food and Drug Administration [FDA] standard that is suitable for food and beverage usages.
- It can meet a wide array of applications as they have high-temperature resistance and chemical compatibility.
- They also come in varying lengths to fit onto existing filter housings.
The components are the:
Inner Support Core
This is the core that supports the filtration material.
It has pores on it to allow clean water to pass through after undergoing the filtration process.
inner support core
This part can be from one of the following substances:
- Tinned steel
- Stainless steel
- Glass-filled polypropylene
- Polypropylene [PP]
It operates by filtering out contaminants from the water.
The outer side is loose hence it allows the capture of large contaminants.
On the contrary, the inner side is tightly wound to capture the small contaminants.
This material can be one of the following substances:
- Glass fiber
- Polypropylene [PP]
- Natural cotton
- Bleached cotton
Here is how these two compare:
melt brown filter
String filters have a large and effective surface area than melt blown filters.
This is because the wound yarn will overlap with each other.
Structure of the Filter Cartridge
String filters have a yarn of a specific diameter that you will wind on a support core to create diamond-shaped patterns.
For melt blown filters, you will blow specific fibers from nozzles and then bond them thermally on rotating shafts.
This creates a dense and porous form that will offer the same porosity level where the fluid passes.
Also, it has no supporting core as the string filter as it is firm independently.
However, you can decide to add a core to provide extra structural support.
Path of the Process Fluid
The fluid in string filters passes via diamond-shaped winding while the path of melt blown filters is almost straight.
Number of Filtration Points
String filters have 16 or more paths while melt blown filters have an average of 8 paths.
Single or Multi Matrices Suspended Solids
It is possible to produce string filters in multi-gradient structures.
This makes it possible for suspended contaminants to penetrate deep within the stricture thus achieving true depth filtration.
One can produce melt blown filters in multi or dual gradient structures.
However, it mainly traps contaminants on the outer surface thus does not use the inner part for filtration.
This makes it have less dirt-holding capability than string filters.
String filters can have an inner core from stainless steel, polypropylene, or tinned steel.
Melt blown filters have an inner core from polypropylene [PP].
Dirt Holding Capability
String filters have a high dirt holding capability.
This makes it suitable for pre-filtration.
On the contrary, melt blown filters have a low dirt-holding capability.
Nominal or Absolute Cartridge Filter
The nominal rating for string filters is at an efficiency of around 95%.
Melt blown filters have a nominal rating with an efficiency of around 97%.
The string filter has a micron rating that ranges from 0.5 to 150.
Melt blown filter has a micron rating that goes from 1 to 20.
Available Filter Media
String filters have filter media from sources like glass fiber, cotton, and polypropylene.
On the other end, melt blown filters use filtration media from nylon and polypropylene.
The string filter can operate on applications that need a temperature of 350 °C.
Also, is it suitable for applications that have a high dust load and requires depth filtration.
On the other hand, melt blown filters need a temperature rating of up to 120 °C.
Melt blown filters are suitable for applications that need an end or final filtration point.
Also, they need applications where the liquid has undergone pre-filtration.
Besides, in melt blown filters, you can use them in applications that do not have pre-filtration but minimal life cycle.
It is possible to filter river water and wastewater with string filters.
However, you can filter spring water, city council water, and pharmaceutical water with melt blown filters.
It is possible to use one of the following yarns when making a string wound cartridge filter:
- Glass fiber
- Polypropylene [PP]
- Natural or bleached cotton
It is worth noting that a string wound filter cartridge has a high dirt holding capacity.
This characteristic makes it last for long periods.
Besides, the durability will also depend on the water you are filtering.
If the water always has lots of contaminants, the life span will be lower than when the water is relatively clean.
A micron is a unit of measurement which is similar to one one-thousand of a millimeter.
This is the size of the opening in a string filter that allows it to filter out dirt or sediments.
Large micron size allows large sediments to pass through than a small micron size filter.
Any size below 40 microns is not visible to the naked human eye.
A string filter has a micron rating that can be anywhere between 0.5 and 150.
The micron rating depends on the type of water you are filtering.
This is because dirty water has contaminants of varying sizes.
Always have a micron rating that allows the removal of microorganisms that you cannot see with your naked eye.
An absolute string filter contains pore sizes that are exact to its micron rating.
Nominal string filters contain pores that are an approximation to their micron rating.
For instance, a nominal 20-micron string filter can allow a small fraction of debris than have a 20-micron size to pass through.
Absolute string filters have an efficiency of over 95% thus they will not permit particles with their micron rating to pass through.
For an accurate filtration process, it is suitable to acquire an absolute string filter and not nominal string filters.
Nominal string filters are the most common but you can find absolute string filters.
Here is a guide that can assist you to consider the micron rating depending on the contaminants you are eliminating:
- Contaminants with a thickness like human hair require a micron rating of 50.
- When the contaminant is not visible to the human eye, you require a micron rating of 40.
- If you have contaminants the size similar to white blood cells need a micron rating of 25.
- A micron rating of 8 will eliminate contaminants the size like that of red blood cells.
- One can eliminate contaminants the size of bacteria with a micron rating of 2.
The length and dimension will depend on the filter housing you plan to place the string filter.
If you need more filtration, you can use long string wound cartridge filters as this increases the surface area.
The end caps are several and provide the necessary filtration need for every application.
Examples of end caps you can find are:
- Custom end cap
- Fin end cap
- Poly 22 end cap
- Stainless steel core extender end cap
- Flat or closed-end cap
- Poly 222 end cap
- Plastisol molded end cap
- Flat open gasket end cap
- Closed-end stainless steel 222 end cap
- Open-end stainless steel 222 end cap
- Polypro 226 end cap
- Polypro core extender end cap
- Ease of disposal
- It should form a complete seal
- Also, it should comply with FDA standards for the food and beverage industries.
- Chemical compatibility.
- Melt blown over carbon
- String wound over melt blown
Pleated surface filters have thin filters that capture contaminants from the surface.
pleated surface filter
Also, they have a large surface area which makes them have a high dirt holding capacity.
When the external surface is full of contaminants and particles, you can dispose of this filter.
Its wide surface area allows it to capture particles that have a uniform size.
Besides, the filtration happens on the surface and you can remove and wash it once the pressure drops.
The main features of pleated surface filters are:
- It will provide an efficient and dependable filtration process.
- One can use it in the food and beverage industries.
- A high maintenance efficiency will offer great protection to downstream filters.
- For broad applications, you can use O-rings.
- It has a high surface area than other cartridges.
On the other hand, depth filter cartridges will also eliminate contaminants from water.
They are also known as string spun and string wound cartridge since it has 2 layers of filtration.
The first layer will capture large particles and the inner layer captures the tiny particles.
Also, you need to clean and change depth filters more often than pleated filters.
depth cartridge filter
Some traits of depth cartridge filters are:
- Large particle containment increases pressure.
- It is durable and a cost-effective filtration method.
- The inner attachments will eliminate contaminants.
- Also, it can work at high speeds since it has a great diameter.
- When manufacturing, you will not use adhesives or other external materials.
This is a string filter that you can use in the food and beverage industries and pharmaceuticals.
- High dirt holding capability
- True depth filtration
- Free from chemical substances.
The core can be of the following materials:
- Gas-filled polypropylene
- Stainless steel
- Polypropylene [PP]
- Tinned steel
Polypropylene String Wound Cartridge Filer Core
This is a cost-effective option for water, aqueous solutions with wide pH ranges, and a wide array of organic chemicals.
The appropriate maximum temperature is 82 °C [180 °F].
Glass-filled Polypropylene String Wound Cartridge Filer Core
This is a great substitute for applications that need more core stability for high temperatures.
Also, it replaces chemically compatible polypropylene.
Besides, it has a compatible fluid maximum temperature of 93 °C [200 °F].
Tin Plated Steel String Wound Cartridge Filer Core
It is a core great for solvents, paints, oils, and high-temperature applications.
The suitable maximum temperature for compatible fluids is 204 °C [400 °F].
304 Stainless Steel String Wound Cartridge Filer Core
This material is good for corrosive fluids or those that have chemicals that make polypropylene expand or soften.
The suitable maximum temperature for compatible fluids is 399 °C [750 °F].
316 Stainless Steel String Wound Cartridge Filer Core
It is suitable for some acids and corrosive agents that are not good for 304 stainless steel.
The suitable maximum temperature for compatible fluids is 399 °C [750 °F].
Nylon String Wound Cartridge Filer Core
This is good for several organic chemicals and fuels.
It has a suitable fluid maximum temperature of 135 °C [275 °F].
Polyester String Wound Cartridge Filer Core
It is a suitable core substance for several oils, fuels, and caustics.
Besides, it has a suitable fluid maximum temperature of 149 °C [300 °F].
PVDF String Wound Cartridge Filer Core
It is a premium-priced fluoropolymer substance.
Also, it offers compatibility with acids, fuels, oils, and oxidizing chemicals.
It has a suitable fluid maximum temperature of 121°C [250 °F].
PTFE String Wound Cartridge Filer Core
This is also a premium-priced fluoropolymer substance.
It offers a broad array of chemical compatibility.
The suitable maximum temperature for compatible fluids is 149 °C [300 °F].
If you use a yarn that is round and smooth to make a wound cartridge filter, it can easily roll and move in that position.
The rolling and displacement effect of the yarn can occur during these two processes:
- Knife-edge sealing.
- Pressure and fluctuations of the flow.
When this happens, it will dismantle the pattern and form gaps between the filtration medium.
This will compromise the efficiency of the filtration.Also, achieving an accurate micron rating will be a challenging task.
When chemicals leach into the liquid, it will cause a major concern as it will compromise the quality of the filtrate.
When you start using the string wound filter, chemicals that begin to leach include:
- Resin binders
- Release agents
These chemicals will begin to mix with the filtrate hence lowering the efficiency and quality of the filtration process.
There are two solutions to combat this effect:
- Prewashing the wound cartridge filter before using it.
- Allow the liquid to flow via the material for some time before you start to officially use the wound cartridge filter.
One of the best ways of ensuring minimal leaching is to ensure filters that are 100% free of these chemical compounds.
Using good quality yarn is one of the determinants to achieve the best filtration with a wound cartridge filter.
When you use short and chopped fibers, they will loosen and move with the filtration liquid.
Some extra deterioration may happen due to:
- Rough handling of the wound cartridge filter.
- Poor and bad packaging.
- Wear and tear can occur during knife-edge sealing.
- Inconsistent flows.
Here is how you can install a cartridge filter and ensure it operates properly:
- Locate the inlet and outlet ports.
- Properly align the piping system while avoiding it from pressing the cartridge filter.
- It is possible to include shutoff valves that enable draining contents while replacing the cartridges.
- Select stable support and volt down the system.
- Install the right size of cartridge filter on inlet and outlet valves, then connect the piping.
- Use the cartridge filter manual to connect all components and cartridges.
- Make sure you align the seal and gaskets, then close them.
- Allow fluid to enter the cartridge filter by opening the shut-off valves.
Cross-check the manual to ensure differential pressure reading is correct
- Maximum operating temperature
- Maximum Differential Pressure
- Change-out Differential Pressure
Maintenance ensures it operates optimally and offers quality filtration processes.
Do not backwash the string filter but rather replace it once it is full of dirt and contaminants.
Clean the filter regularly to eliminate any dirt and impurities.
If possible, ensure the yarn is always wet to prolong its use time.
These limitations include:
This happens when you use short and chopped fibers, as they loosen and move with the filtration liquid.
This happens when chemicals will leak into the fluid and cause health hazards.
Roving and Friction on Spun Yarns
This happens when the yarn starts to shift and form tunnels.
It may tend to roll on one side thus give an inconsistent outcome as the fluid passes via a less resistant path.
Some of the tests it undergoes include:
- Destructive test
- Non-destructive test
- Bubble point test
- Pressure hold test
- Diffusion test
These developments will combat any drawbacks of these filters.
New media has a continuous filament and not short chopped fibers.
This means each filament will span the whole length of the yarn this combating the media migration effect.
These new filaments have no spin-finish chemicals.
Also, the yarns form a stable and bulky yarn as the filaments are random, intermixes, loops, and intertwines over each other.
With this new development, every yarn will trap the neighboring yarn thus achieving a stable configuration.
These yarns lock in place and do not shift side to side.
This effect enables it to overcome particle unloading and offers great knife-edge sealing.
Winding technology also assists in controlling the start and finish of the yarns.
It allows one to form tight inner weaves with no change in tension thus enhance a consistent performance.
Also, the new winding technology will form stable cartridges with no diamond patterns.
Selecting the best filter ensures that the filtration process is accurate and of good quality.
Some of the components of a string wound cartridge filter are the core, yarn, gasket, and endcap.
The best string wound cartridge filter applies the best materials and the weaving is of good quality.
This is to ensure you achieve the best filtration process.
Some suitable qualities to look out for in a string wound cartridge filter are:
- High precision manufacturing
- A durable and sturdy core
- The best quality yarn
When you use good quality materials, you will enhance the performance of the filter.
Also, it will achieve a high filtration capability and be durable.
Always select a string wound cartridge filter from a reputable manufacturer who uses the latest technology.
Changing a string filter depends on the quality of water that it is filtering and this is dependent on each supply.
When it is full, simply change the string filter.
To change it, start by turning off the supply and then unscrew the housing and empty the fluid from inside.
Take the filter out and replace it carefully until you achieve a suitable seal.
As you can see, there are many factors you should consider when choosing string filters.
However, if you have any question regarding string filters, FilSon team is here to help – contact us now.