Ballasting Flow Rates: The True Cost of Delays & How to Avoid Them

In today’s maritime industry, ship owners and operators are required to make new, costly investments to ensure that vessels comply with the latest environmental regulations. This includes the Ballast Water Management Convention (BWMC), which requires most vessel owners to install and operate an effective ballast water management system (BWMS). Typical BWMSs have a primary treatment component, in most cases a filter, then a secondary treatment component to neutralize the organism found in the ballast water. With profit margins under pressure, and numerous products to choose from, many shipowners see BWMS and filter selection as a weighty decision with long-term CAPEX and OPEX implications.

To make a smart decision, it is essential that shipowners understand both the regulatory and technical benefits of specifying a BWMS that includes a suitable filter – one that promotes proper filtration to avoid ballasting delays and non-compliance with the BWMC.

 

Regulation and non-compliance

In order to comply with the International Maritime Organization (IMO) Ballast Water Management Convention and the additional US Coast Guard (USCG) ballast water regulation, it is essential to select and operate a high-performing BWMS to ensure long-term and reliable treatment of invasive aquatic species. In practical terms, most ships ballast in port or river estuary waters, where sediment is significantly higher than out at sea. This can significantly impact flow rates if a low-quality filter is installed, which can then extend ballasting times.

 

Flow rates impact finances

Ballasting rates for a vessel are designed alongside the rates of cargo loading and discharge. For vessels to safely load and unload cargo, the ballast pumps must be able to either load ballast water or discharge ballast water to maintain the stability of the vessel. The slowing of the flow during ballasting can have dangerous consequences for vessels during cargo discharge if the stability of the vessel becomes compromised, such as listing.

A decreased flow rate occurs for two primary reasons: firstly, during heavy loading, when filling the tanks to maximum capacity as quickly as possible, the filter will often go into continuous backflush and a significant portion of the water will be diverted through the backflush line. Secondly, filter loading and increased differential pressure across the mesh places a larger discharge head on the ballast pump, causing the pump to flow less water to the tank.

In reality, the time it takes to move ballast can range from 12 hours to nearly 90 if the filter is not designed for heavy loading. In comparison, a filter appropriately designed for a vessel’s loads and the waters where it will be ballasting may be able to move more than three times as much water than a filter that slows or clogs.

The exact amount of money that can be lost will depend on the market, the type of vessel, whether the vessel is in port, how busy the crew is, and what the costs may be for additional time alongside. However, as an example, a VLCC tanker earning a typical $36,000/day, every hour of delay can cost $1,500 plus any port charges. These costs can rapidly add up and should be kept in mind when considering CAPEX and OPEX for a BWMS installation.

 

The challenge of sediment

An additional factor that can decrease flow rates is the level of sediment being collected while ballasting. Two particular locations, the Mississippi River Delta and the Yangtze River, show exceptionally high Total Suspended Solids levels and present a particular challenge to many BWMS technologies.

Sediment is one of the critical factors in filter clogging but allowing sediments to accumulate has further implications to the vessel. The buildup in the ballast tanks between drydocking periods can create an unpumpable, permanent ballast that, if not removed, reduces the vessel’s cargo capacity over time.

For vessels contracted in the bulk and oil trades, this may affect the charter agreement and cause vessels to carry less than the obligatory cargo amounts as per the voyage plan, with potentially significant implications for a ship’s earning ability. Vessels are designed to carry a specific amount of cargo based on weight and displacement, so vessels ferrying around even a few inches of sediment over the entire bottom of ballast tanks can quickly see tonnes of additional weight added to their dead weight. This additional dead weight may offset cargo loads.

The choice of a BWMS and its filter is critical for shipowners and operators to avoid non-compliance and expensive ballasting repercussions. It must be economically sound, both from a CAPEX and long-term OPEX standpoint. The filter within a system has a big effect on its ability to perform effectively, efficiently and within the regulatory parameters. As such, it is an investment with potential implications for many company departments, including technical, operations and finance. This makes BWMS and filter selection a business critical issue.

For more information on this topic, please download our whitepaper on the cost of compliance here: https://filtersafe.net/the-true-cost-of-compliance-in-the-marine-bwms-industry/

Filtersafe provides high performing BWMS filters for ConocoPhillips Fleet

Filtersafe multifilter installed on Polar fleet

Learn why ConocoPhillips chose the De Nora BALPURE® BWMS with Filtersafe filters for their entire Polar Vessel fleet.

ConocoPhillips, Alaska’s largest crude oil producer and the largest owner of exploration leases, operates a series of vessels traveling between Alaska and San Francisco. This west coast route has particularly challenging conditions due to widely ranging water quality, including high sediment waters in San Francisco Bay.

ConocoPhillips Polar route with Filtersafe filtersConocoPhillips recognized the need for high-performing ballast water management system (BWMS) filters to ensure regulatory compliance and operational efficiency. In 2015, the company invested in independent testing to assess and choose the right BWMS filter for the fleet’s operational route.

It was through this testing that they came to the conclusion to install the De Nora BALPURE® BWMS with Filtersafe filters across the fleet.

The BallastSafe BS300-T filter . The filter is designed to perform under high sediment loads in poor water quality areas and has a flow rate of 750 m3/hr. Due to the enormous size of the ships in the fleet, it was decided that in addition to 2 BallastSafe BS300-T filters, that 2 additional BallastSafe BS1204H filters should be added when the BWMS is installed in each ship.

 

Filtersafe solution

Most filters build a “cake” i.e. an uncleanable part of the filter created over time as a result of a decrease in water pressure in the filter system. For the filter to return to optimum performance levels, the filter must be manually cleaned. In contrast to most filters, Filtersafe’s solutions are the only technology available to the global shipping industry today which is self-restoring.

This means the filters have no uncleanable areas and are able to remove even the toughest build-up, with the filter returning to its original clean state after every heavy use in less than three minutes. For example, in the Shanghai Test our filter fully recovered from an unimaginable TSS load of 2,450 ppm in 182 seconds. 

Filtersafe has an exclusive, upgradeable cleaning mechanism that can be modified even after installation to improve cleaning efficiency. This means the filter can be configured according to the vessel’s trading waters and then changed as those trade routes are altered over the life of the ship. This is significant as it removes the limitations that ballast water management systems (BWMS) have traditionally placed on ships, allowing vessels to move between low and high sediment routes, such as the tankers navigating around high sediment areas of San Francisco, without being prohibited by filter performance.

 

Results

The filter operated under various conditions for several months, monitoring and recording hundreds of hours of valuable operation data. The results of the tests demonstrated flow rates varying between 400-750 m3/hr. These rates were recorded during testing and varied according to inlet pressure levels and sediment loads, which reached as high as 400 Nephelometric Turbidity Units (NTU) (TSS 350- 400mg/L). The filter performed very well during high sediment loads, especially at known turbid locations such as the Shell Terminal in San Francisco Bay and the ports of Anacortes and Valerio in Washington, recovering quickly from the high dirt load conditions. In addition, the filter operated without the need for manual cleaning throughout the duration of the test.

Following the successful installation and the test results on board the pilot Polar vessel transporting fuels regularly between Alaska and other major energy producing ports along the North American West Coast, ConocoPhillips decided to install Filtersafe filters on the entire Polar fleet.

Following the initial test, all five crude oil tankers in the Polar fleet will feature filtersafe filters as an integral part of their BWMS, with 2 ships already past installation and commissioning and the rest with planned installation datesin 2022: Polar Endeavour, Polar Enterprise, Polar Resolution, Polar Adventure and Polar Discovery, as outlined above. Each vessel was assessed according to its ballasting needs to ensure the right filters and flow rates were chosen. Filtersafe also worked with a leading class society, the American Bureau of Shipping (ABS), to complete a successful remote pressure test survey to certify the filters ahead of installation to ensure the highest standards for ConocoPhillips.

To read more about the installation, please download the case study here:

Download: ConocoPhillips & De Nora BALPURE® BWMS Case Study

What the Shanghai Test Results Tell Ship Owners About a Ballast Water Filter

Shanghai River with Muddy Water

Savvy ship operators know that the right filter is key to not only complying with IMO and USCG regulations but also to ensure that their ship can sail and ballast anywhere, in addition to costing or saving a ship money by how long it takes to filter and fill a ship’s ballast water tanks.

Shipowners and operators regularly ask Mr. Louis Peperzak (Technical Manager Ballast Water Services at Control Union) and his colleagues: “How am I supposed to trust that a ballast water filter will work in severe circumstances?” they continue: “since IMO regulations account for 50 mg/L of TSS but in Shanghai Harbor, TSS concentrations can reach up to 1,000 mg/L?”

They turned to Control Union specifically as they are a highly respected 3rd party certifier of various maritime QA/QC evaluations, including for ballast water management systems. The Control Union as a whole is a collection of international companies that offer certification in various industries, including marine and ballast water.

What is the ‘Shanghai Test’?

This is how Control Union came to create their ‘Shanghai Filter Test’, which seeks to mimic the muddy, turbid waters of the popular Shanghai Port. If a ballast filter could manage to filter the 1,000 TSS mg/L of suspended solids that can be found in the waters of Shanghai without clogging, then they could be confidant that their ship can sail to and ballast in any port without fear that the filter would clog from water with high total suspended solids (TSS).

The test puts water with mud the similar consistency and particle size distribution as the mud found in the Port of Shanghai through the filter at increasing amounts until the filter has less than 5% outflow and effectively clogs. Since the Port of Shanghai can have a maximum TSS of 1,000 mg/L that is the benchmark Control Union has set for whether a filter passes the test or not. If a filter can work at 1,000 mg/L without clogging, it is considered to have passed the test.

A clogged ballast water filter is an expensive and time-consuming problem for shipowners. A clogged filter means:

  1. The ballasting process must stop while the filter is cleaned, halting loading or unloading of cargo from a ship;
  2. Seafarers must invest manpower and spend time cleaning the filter instead of attending to their other important, onboard duties;
  3. More time spent in port, having to pay port fees, and time lost on the delivery route.

If a shipowner can know that a ballast water filter comes tested & certified by Control Union as having passed the test and not clogging at 1,000 mg/L of TSS, they can have more confidence in their entire BWMS. This means a certified ballast filter is also of interest to BWMS manufacturers and naval architects who help ship operators pick and install their BWMS.

Filtersafe’s Shanghai Test Results

Filtersafe sent 5 configurations of its ballast water filter to the Control Union location in the Netherlands for the test (a combination of 25 micron and 40 micron screens paired with standard, turbo and superturbo automatic self-cleaning options in a BS101 filter body).

Filtersafe is proud to announce that not only did all 5 of the configurations pass the 1,000 mg/L challenge, all filters were challenged with increasingly turbid water, up to 2,450 mg/L, and none of them clogged.

We invite you to take a look at the results yourself. You can download the Shanghai Test Report to receive an explanation in detail of how the test was conducted and the results of each of the 5 tests.

Please fill out the form below to immediately download your copy of Filtersafe’s Shanghai Test Report.

316L vs. 904L Stainless Steel: What’s the Difference?

PMI gun testing 904L steel

The global maritime industry has been shifting towards greater environmental protection efforts in recent decades. The International Maritime Organization’s Marine Environment Protection Committee (IMO MEPC) works to address issues that affect and threaten our oceans, including air and water pollution, disaster preparedness, and ship recycling.

However, this organization also studies an environmental issue hardly known to the public: ballast water management.

Ballast water tanks keep a ship balanced as she transports cargo, but it must be fully filtered and treated before being released at her port of call. The IMO guidelines require that ships only discharge ballast water, that is:

  • < 10 viable organisms/m3 that are ≥ to 50 micrometers in minimum dimension
  • < 10 viable organisms between 10 micrometers and 50 micrometers in minimum dimension per ml
  • < 1 colony-forming unit (CFU) per 100 milliliters of Toxicogenic Vibrio Cholerae
  • < 250 CFU per 100 ml of Escherichia coli
  • < 100 CFU per 100 ml of Intestinal Enterococci
Organism SizeSize UnitNumber of OrganismsStatusAmountAmount UnitType
Over 50μm10viable organisms1m3Any
10 to 50μm10viable organisms1mLAny
--1Colony-forming units100mLToxicogenic Vibrio Cholerae
--250Colony-forming units100mLEscherichia coli
--100Colony-forming units100mLIntestinal Enterococci

These guidelines have solidified the importance of ballast water management systems (BWMS), making them a vital part of every ship. It is also more important than ever to maintain (and in some cases, upgrade) these systems – mainly because, as Filtersafe Head of Marine Mark Riggio recently said, “[the] global maritime industry [is] shifting its focus to operational compliance.”

The Best Alloy for Ballast Water Management Systems

Seawater filtration systems have a unique challenge to overcome. They must effectively filter debris and microorganisms while also withstanding the high chloride levels in the water, which constantly threaten to corrode the filter and its filtration screen. To achieve this goal, manufacturers often design BWMS with a filter that has a filtration screen made from a durable stainless steel alloy.

For many years, the industry-standard alloy of choice for filter screens has been 316L stainless steel. But due to the rising need for operational compliance, some of its shortcomings in seawater environments are coming to light. This has led some manufacturers to opt for the higher-grade 904L stainless steel when producing filtrations screens for seawater applications. Both these alloys can be applied in seawater filtration, but what are the differences between these two types of steel? And ultimately, as many shipowners are left to wonder, which is the right alloy for their BWMS, and their bottom line?

What is 316L Steel?

316L stainless steel is an austenitic alloy commonly known as “marine grade stainless steel” because it can be used for nearly 90% of marine applications – including filtration. In addition to metals like iron and nickel, 316L contains 16-18% chromium and 2-3% of molybdenum. These elements are important because they increase the alloy’s corrosion resistance; the chromium interacts with oxygen in the seawater to create a protective layer of chromium oxide, and molybdenum improves the metal’s ability to resist pitting corrosion. Additionally, 316L has lower levels of carbon (hence the “L” in its name), which gives it greater protection against corrosion.

What is 904L steel?

While 316L has long been the primary alloy ballast water filtration manufacturers use for their filter screens, it is not the only alloy available on the market. In fact, Filtersafe has been examining the value of 316L for many years now. As global leaders in the seawater filtration industry, our engineers sought to improve filtration standards by improving our materials. Our studies concluded that 316L stainless steel was not durable enough to meet our requirements – and so we opted instead to manufacture filter screens from 904L stainless steel In fact, Filtersafe – the global leader in seawater filtration – has been examining the value of 316L for many years now.

Like 316L, 904L stainless steel is a low-carbon austenitic stainless steel. However, its chemical composition includes greater numbers of chromium (19-23%) and molybdenum (4-5%), which gives the alloy greater corrosion resistance than 316L. Some people are familiar with 904L stainless steel as a metal commonly used to produce Rolex watches, which speaks to its high quality and durability. However, the same benefits that make it a must-use for Rolex also make it hugely beneficial for seawater applications.

316L vs. 904L: Durability

Seawater is highly unpredictable. It can have dramatic variances in temperature, chloride level, and the presence of microorganisms or debris. Therefore, a BWMS filter must be durable enough to withstand these changes.

Both 316L and 904L stainless steel contain chromium, which reacts with oxygen in the air to form a thin, protective layer of chromium oxide on the surface of the alloy. However, it is important to note that 904L contains more chromium than 316L. This means it is likely to provide greater protection over a longer period of time.

types of corrosion that afflict stainless steel in seawater applications

904L vs. 316L: Corrosion Resistance

Perhaps the most important feature of any alloy used in marine applications is its ability to handle constant exposure to corrosive substances. Seawater filters are prone to several different types of corrosion attacks, including from chloride, microbiologically induced corrosion, and crevice corrosion. The filter is particularly susceptible to these three corrosion types during the 1-3 week period between ballasting, when the filter is immersed in stagnant water, which can allow the development of a biofilm inside the filter and on the screen, and lead to corrosion. Therefore, a ship owner needs a filter with as much corrosion resistance as possible.

Shipowners and manufacturers can measure corrosion resistance by looking at an alloy’s PREN value. This formula looks at the amount of chromium (Cr), molybdenum (Mo), and nitrogen (N) in an alloy to determine just how well it will hold up against corrosion. In this case, 904L stainless steel is the clear victor over 316L; with an average PREN value of 36.7, it is much stronger than 316L (which only has a PREN of 26.1). Therefore, 904L is more likely to withstand the corrosive power of seawater.

904 vs. 316: Steel Hardness

To further understand the differences between 904L and 316L stainless steel, we must examine the hardness of both metals. The best way to do this is to look at the Rockwell Scale, which measures the indentation hardness of a material. Metals that score highly on the Rockwell scale are harder, which implies that they will be strong and withstand any bumps or bruises.

Both 904L and 316L stainless steel have a Rockwell hardness value below 95, which is typical for most stainless steel. This means that they will be able to withstand most forces, which is important for BWMS. However, it is far more important that seawater filter screens withstand the internal dangers like chloride and other corrosion attacks. 904L offers greater protection overall, which sets it above 316L.

904 vs. 316: Cost

904L stainless steel and 316L stainless steel are both readily available for purchase. Many industries and companies use 904L stainless steel, and the alloy has some brand recognition as it is famously used by watch manufacturers like Rolex and OMEGA. 316L stainless steel is commonly used for exhaust manifolds, heat exchangers, jet engine parts, and much more. As a result, BWMS manufacturers can introduce either alloy into their supply chains without suffering a delay in supply or a product bottleneck.

But which alloys offer the most “bang for your buck”?

If you look solely at the numbers, 316L may seem like the more attractive choice. Because of its widespread use across so many industries, this metal is both easy to purchase and available for a lower price. 904L tends to cost about 1.3 times more than 316L, which can make some manufacturers balk at the idea of producing all their filter screens from this material.

However, it is important to remember that filter screens made from 904L stainless steel will last longer and require fewer repairs than filters made from less durable materials. The enhanced corrosion resistance capabilities of 904L stainless steel make it less likely to wear down and break from corrosion, and therefore it will require fewer repairs over its lifespan. This is ideal for shipowners who do not want to incur additional costs to keep their ship in compliance with industry environmental and operating standards.

What is the Difference Between 316 and 904L Stainless Steel?

When ship owners are deciding between filters for their BWMS, they must consider a variety of factors before making their choice: cost, availability, value, etc. On the surface, the differences between 316L and 904L stainless steel may seem negligible, but in actuality, they have huge impacts on the long-term value of the filter.

To the Filtersafe team, the choice is clear: 904L stainless steel is the best choice for BWMS filters. 904L stainless steel offers greater durability, which makes it more effective and less costly over time (despite a higher initial cost). This alloy will help boost standards across the seawater filtration industry – and, in turn, improve environmental factors in oceans across the globe.

The choice is also clear where to look for spare parts for your ballast water system filter – only from Filtersafe! Only Filtersafe can guarantee the steel type and quality of our spare parts to ensure your filter continues to work as expected for years to come.

To learn more, download our white paper on Overcoming Corrosion of Stainless Steel in Seawater Applications for more extensive research on the common alloys used in seawater.

The Top Alloys For Use In Seawater Filtration Applications

a comparison of the top seawater worthy stainless steel alloys

Filtration of seawater is a necessity across a diverse range of industries – such as intake for a desalination plant, ballast filtration for an oil tanker, or to maintain pressure and the production rate. When running a complex operation there are plenty of unexpected expenses to deal with on a regular basis, and the last thing anyone wants is a preventable failure of their filtration equipment. This is especially pertinent when dealing with seawater because it is filled with corrosive elements that can lead to material failure like corrosion or strength degradation. Therefore it’s important to have a quality, durable filtration system.

desalination pipeAs part of the search for the best system, an often underappreciated but critical component to its success is dependent on which alloy the screen filter, the heart of the system, is made of. The filter screen is the physical barrier that prevents particles (organic and inorganic alike) that are larger that its pore size from passing through with the water. Corrosion to the screen can damage its ability to be cleaned, clog its open area and inhibit water flow, or degrade the screen’s structural integrity, letting particles larger than its pore size to get through and compromise the integrity of the system. Various seawater filtration industries struggle with the same decision as to which is the best.

Seawater filters have unique and specific requirements: they need to be non-corrosive, as well as effective at removing debris of various sizes, which can harm down-stream processes. This is extra important in industries that rely on very fine filtration (100-5 microns), such as in desalination and ballast water filtration. In these cases, the screens must also be highly effective at removing phytoplankton and zooplankton from the water. Any seawater processing application requires a durable pre-filtration protection system so that time and money isn’t wasted over the years to repair poorly protected systems. With this in mind, let us look at the most common alloys used in seawater filtration and determine which alloy best suits your system.

316L

316L stainless steel, also known as “marine grade stainless steel,” is the second-most common stainless steel used in manufacturing today (after 304 stainless steel). This alloy is made up of iron, chromium (about 16%), nickel (10%) and molybdenum (2%), as well as trace amounts of quantities of silicon, phosphorus, and sulfur. Although it is a popular choice, the latest advice from the International Stainless Steel Forum is that AISI 316 and its derivatives “are no longer recommended for permanent contact with seawater.” We’ll see some of the reasons behind this decision in the Cons section.

Pros

316L stainless steel is a popular choice for seawater filtration. This is in part due to the alloy’s widespread use throughout many industries, making it widely available, as well as the benefits described below.

Some Corrosion-Resistance

Like all of the alloys discussed here, 316L stainless steel contains chromium. This element is an important part of the chemical makeup; it creates a thin film over the alloy when exposed to oxygen, which helps prevent the steel from becoming corroded over time.

The chromium in the alloy does provide a degree of protection that prolongs the steel’s – and by extension, the filtration system’s – lifespan. However, it is important to note that 316L does not provide complete protection from corrosion. While the alloy can offer reasonable protection in the short term, its particularly susceptible to pitting corrosion caused by inconsistent salinity levels in the seawater.

Tolerant to Higher Temperatures

Temperature fluctuations are most acutely felt in the shipping industry, as seawater can vary wildly in temperature between locations, seasons or even times of the day.  316L can tolerate water temperatures up to Celsius (68 degrees Fahrenheit), which means it is able to successfully stand up to most seawater.

Low Cost

One of the biggest benefits of 316L stainless steel is its relatively low cost and wide availability. Manufacturers can purchase 316L scrap relatively inexpensively, which makes it a highly accessible material for filtration system engineering.

Cons

Despite 316L’s popularity, there are some industry experts who believe that this stainless-steel alloy is inappropriate for use specifically in ballast water treatment systems. These professionals cite issues with the welding process as a major drawback – and the consequences of these issues certainly warrant a second look in other seawater applications as well.

High Ferrite Content

One of the biggest drawbacks in using 316L stainless steel for seawater filtration can occur during the welding process. 316L must be welded under very strict conditions, or else it might develop a high ferrite content in the weld seam.  Ferrite can diminish an alloy’s ability to resist corrosion. Even a small amount (around 2%) of ferrite content in a weld seam can result in a less effective finished product.

Since 316L stainless steel is prone to developing excess ferrite during production, it can make some filtration experts leery of using this alloy in their systems. In fact, some argue that the potential for high ferrite content in 316L stainless steel can lead to greater incidence of pitting corrosion or crevice corrosion. This kind of damage can require significant repair or even a completely new filtration system – effectively counteracting the reduced costs of using the 316L alloy.

Duplex 2205

Duplex 2205 is a stainless steel characterized by its strength. With a makeup of 22% chromium, 3% molybdenum, and about 5% nickel, it is about on par with 904L in terms of corrosion resistance. However, duplex 2205 is (as the name suggests) a duplex stainless steel; this means that it contains both austenite and ferrite phases in its metallurgical structure, giving the alloy a greater overall durability.

Pros

Duplex 2205 is the most popular of the duplex stainless steels, and it is often used in pipework systems for offshore oil and gas. This alloy’s strength and chemical composition, as well as its durability against
seawater in offshore uses, makes it a logical choice on paper.

seawater filtration for oil and gas applications

Good Corrosion Resistance

Duplex 2205 has a PREN average of 35.9 – just shy of 904L stainless steels average of 36.7. This indicates that this alloy would be able to fair just as well as 904L when dealing with pitting corrosion, crevice corrosion, or any other type of destructive wear and tear within the filtration system. Theoretically, duplex 2205 would be a reasonable alloy for a seawater filter.

Cons

While duplex 2205 has had plenty of success within the oil and gas industry when used as a solid structure such as piping, it’s not used often in complex manufacturing procedures such as a weaved screen mesh used in seawater filtration. This is likely due to two main issues: There are challenges when working with it and its lower temperature threshold for corrosion.

Hard to Work With

One of Duplex 2205’s assets, it’s strength, is actually a double-edged sword. Since the alloy is so strong, it makes it difficult to work with, and requires special heavy machinery that is not commonplace. In addition, it makes it very challenging to mold the steel into the very tiny and delicate structures, such as ballast water filters or desalination filters that require filtration down to 10 microns.

Corrodes Faster than 904L

While Duplex 2205 has better corrosion resistance than 316L, it still corrodes at a lower temperature than 904L (50C vs 55C for 904L).

904L

Another popular alloy used in seawater filtration is 904L stainless steel. This alloy contains many of the same elements as 316L steel, but it is comprised of higher levels of chromium (about 19%), nickel (23%), and molybdenum (4%).

904L stainless steel is most famously used in luxury watches (Rolex, for example, swears by this alloy), but it is also a popular metal for seawater filtration. This is because the high amounts of nickel in this alloy
makes it particularly corrosion resistant, protecting your seawater filter from damage.

Pros

Choosing the right alloy is essential for a durable and effective seawater filtration system. When alloys have similar compositions, like 316L and 904L, the decision may seem insignificant; however, 904L stainless steel has some major benefits that can make a big difference for a seawater filter.

Highly Corrosion-Resistant

As we mentioned above, 904L is highly resistant to corrosion due to the high levels of nickel in its composition. This means that seawater filtration systems made with 904L tend to have a longer lifespan than their competitors.

In fact, 904L stainless steel has an average pitting resistance equivalent number (PREN) of 36.7 – more than 10 points higher than 316L’s PREN average (26.1). This is an important parameter to consider when
designing seawater filters, as it will help determine how effective the filter’s corrosion resistance and durability will be over its life.

Widespread Availability

Another benefit 904L has to its credit is its availability in the market. This alloy is readily available from most suppliers, which means that engineers and manufacturers can procure the metal and produce filtration systems much more easily than they might with other metals.

Cons

While 904L stainless steel offers both practical and logistical benefits, it is not a perfect alloy. Some engineers or manufacturers may opt for another metal due to the one major flaw that accompanies using this metal: the cost to use it.

Higher Cost

The costs of most alloys vary based on the amount of chromium and molybdenum in the metal. As we’ve mentioned previously, 904L stainless steel has higher levels of both these elements compared to 316L – which means that it tends to be about 1.3 times more expensive.

This price difference might drive some budget-conscious manufacturers to a lower-quality alloy. However, it is important to mention that the greater strength and durability of 904L stainless steel means that filters made from this alloy are less likely to need repairs during their lifespan. The cost savings you will earn from this lack of repairs more than offsets the cost of the alloy itself.

254 SMO

Like the two alloys we’ve already mentioned, 254 SMO is an austenitic stainless steel. However, this alloy was originally developed for use in chloride-heavy environments – such as seawater cooling pipes, heat exchangers, pulp and paper plants and more. The metal contains a similar amount of chromium as 904L, but it has a greater amount of molybdenum (6% vs. 4% in 904L).

With this composition in mind (not to mention the alloy’s intended use), it is no surprise that 254 SMO is an alloy that generates lots of interest among seawater filtration engineers. There are unquestionable benefits that come with using this alloy – but there are also a few drawbacks that can complicate its use.

Pros

The greatest benefit of using 254 SMO for seawater filtration is its corrosion resistance. The chemical composition of this alloy makes it highly resistant to both microbiologically induced corrosion and chemical corrosion – making it incredibly durable against seawater even after prolonged exposure.

Excellent Corrosion Resistance

254 SMO has a PREN average of 43.8, which means it has the greatest protection against corrosion of all the alloys studied here. It also has a low carbon content (around .02%), which means that there is little risk of ferrite development during production. These two facts mean that 254 SMO is one of the best alloys for protecting your seawater filtration system from the corrosive effects of seawater.

Cons

The excellent protective qualities of 254 SMO might make it seem like the gold standard in seawater filtration materials. However, at least in their ballast water treatment systems, few developers use it – why? 254 SMO is often passed over due to two flaws in its practicality.

High Cost

As we mentioned earlier, alloy costs vary depending on the amount of chromium and molybdenum in the steel. 254 SMO contains higher levels of these elements than both 316L and 904L stainless steel – which means that it tends to cost much more than its competitor alloys.

254 SMO can cost as much as three times more than 316L, and many manufacturers are unwilling to spend more to produce their filtration systems. This cost is above the threshold deemed “acceptable” by most industry professionals (unlike 904L stainless steel, which has a slightly higher cost but offsets the cost of maintenance).

Limited Availability

One of the hinderances that limits 254 SMO from being suggested for more seawater filters is that this alloy is not produced regularly due to its higher costs.

Which Alloy is Best?

radar diagrams for common stainless steel alloys

Due to the nature of seawater filtration and its association with heavy industry, engineers of all applications endeavor to build filtration systems standing up to the ravages of seawater — all without costing you too much money. At the same time, the cost of using a lower-quality alloy will corrode more easily and lead to expensive problems – specifically more frequent maintenance and reduced filtration capabilities as corrosion overtakes the screen. These outcomes will, in the long run, increase operating costs, as equipment owners will have to pay for more frequent servicing, and where applicable such as in regulated industries like ballast water management systems (BWMS), potential fines for non-compliance of malfunctioning systems.

The solution? Invest in a filtration system that’s made from a durable, yet cost-efficient material. And when it comes to choosing the best alloys for seawater filtration without consideration of cost – SMO 254 is definitely the favored alloy. When dealing with a high end application where even the smallest downtime can be very costly such as in the oil & gas or desalination sector, the initial investment in using a Filter with an SMO 254 screen pays off in the long run. However, when a cost-effective solution is required, there is one option that stands head and shoulders above the competition: 904L stainless steel.

904L stainless steel is the ideal marriage of strength, corrosion resistance, and accessibility – all at a reasonable cost to manufacturers. Seawater filters made from this alloy will stand up to corrosion and keep your filtration system running effectively for many years, saving you thousands in fees and maintenance costs.

For a deeper investigation into the alloys discussed above for use in seawater applications please download our peer-reviewed white paper on the topic – Overcoming Corrosion of Stainless Steel Screens in Seawater Applications.

10 Most Invasive Marine Species

Ships worldwide transport over 10 billion tonnes of ballast water every year and by doing so inadvertently bring small plants and animals from one port to another, when they load and unload the water. Running the risk of ecological disaster via invasive species.

This is is why the International Maritime Organization decided vessels need to install ballast water management systems – to clean and treat the water before it is loaded into the ballast tanks. This way when the ship reaches its next port and needs to dump the water in its ballast tanks overboard, it won’t introduce any invasive species into a new ecosystem.

The following infographic shows the top ten invasive marine species that were transported by international shipping and the impacts they had.

Filtersafe is proud to be a leader in the movement to end the spread of invasive species and to protect our marine resources.

top 10 most invasive marine species
Click on the Top 10 Most Invasive Marine Species image to see in high quality.

Sizing Up BWTS Filter Options To Reduce Operational Compliance Risk

In a recent panel discussion for Riviera’s Ballast Water Webinar Week, Dr. Guillaume Drillet, Regional Manager at SGS, shared his views on the main reason for ballast water treatment system (BWTS) failures during compliance testing. Speaking on the webinar titled “BWMS commissioning testing: making it work in practice”, he said that organisms over 50 microns in size are responsible for clogging BWTS, subsequently leading to test failure.

His comments underline the critical importance of BWTS filters – the component responsible for preventing organisms from entering the tanks. Without a strong and robust filter, the effectiveness of the entire BWTS could be compromised, leaving manufacturers open to criticism from ship owners and operators, who must repeat unsatisfactory tests at a later date.

 

Compliance challenges

Selecting the right filter brings significant rewards to the shipping industry, from driving compliance, to preserving marine biodiversity and increasing operational efficiency.

Each BWTS and vessel is unique and faces its own set of challenges and specific stresses. These are impacted by the BWTS used and the conditions it must operate in. For example, there are challenging testing conditions in shipyards with poor water quality, shallow harbors with a high silt load, and difficult initial loading conditions. If a filter is unable to withstand these conditions and clogs, water flow through the BWTS will be limited or even prohibited.

 

Regulation requirements

Under IMO G8 requirements, filters must prove their ability to perform effectively in water with total suspended solids (TSS) up to 50 mg/liter. However, the threshold to pass this test is not reflective of water quality standards in some key maritime locations. For example, TSS in the Ports of Shanghai and Hamburg are twenty times higher than IMO G8 requirements for BWTS type-approval testing. This means high-quality filters that exceed IMO performance standards are critical.

Fortunately, filter performance in more challenging marine environments can be tested through the Control Union Shanghai filter test (Procedure CUW-HBR-P-2), which uses proxy mud up to and beyond 1,000 mg/L to test filter performance.


Size is part of the solution

In order to prevent organisms over a certain size from impacting BWTS and compliance testing, filters need to be engineered with a design that has effective mesh sizes.

Filtersafe use mesh sizes from 10 microns upwards, at flow rates from 50-5000m³/hr in a single unit. Using these fine mesh sizes ensures the system prevents organisms from entering or impacting the system by settling into the ballast tanks or clogging the system.

A filter capable of withstanding the highest TSS conditions found in the world’s oceans will provide confidence to shipowners that the BWTS will pass compliance tests in any port around the world. In its Shanghai Test, which simulates an excessively high particle load, Filtersafe filters did not clog, even when the test reached 2,500 TSS.

With compliance testing coming ever more to the fore, BWTS manufacturers, shipowners, and operators need to be confident that systems are capable of performing effectively throughout the lifecycle of the vessel across all marine environments, including areas where water quality challenges are acute. It is important to remember – mesh size matters.

Filtersafe’s NozzleX: An Innovation that will Save Your Filter Screen

Filtersafe's nozzleX, the only nozzle your filter will ever need

At Filtersafe, we understand that water filtration is essential to helping many industries run smoothly. However, we also understand that today’s filtration technologies can always be improved — which is why we strive to be a leader in the world of water filtration. Our engineers have decades of experience in the industry, and they’re dedicated to creating the top technologies for automatic filtration.

nozzlex nozzle head in filter

One such technology is the NozzleX suction scanner – an innovative tool that enables the cleaning of organic and inorganic material from your filter’s screen, without wearing down the nozzle or wearing out the screen. With a typical automatic screen filter, the nozzles sit on a bar called a raiser. The raiser moves the nozzle heads back and forth along the length of the screen, while also rotating the nozzles in a corkscrew motion. The nozzles scan the surface, and by using negative pressure, dislodge debris one square inch at a time. While this does help the screen filter water effectively in the short term, the force from the nozzle can damage the screen and shorten its lifespan.

NozzleX, by contrast, uses low head pressure (as low as 23psi) to clear off all the buildup on the screen without damaging it. First, the raisers move the nozzles in such a way that 100% of the screen is scanned and cleaned. Next, in contrast to other filters, NozzleX nozzles safely come into contact with the screen, utilizing gentle pressure to pull materials off of the screen without impacting the screen’s integrity. This results in improved performance and a longer lifespan for your ballast water filter or other filtration technologies.

 

Why It’s Important

The importance of a properly functioning nozzle is simple – a water filtration system only works when it’s clean. Whether you are filtering ballast water before filling your tanks, protecting your oil and gas exploration equipment safe from organic oceanic materials, or prefiltering water for desalination, each filtration system should have the same thing in common  a reliable nozzle to clean your screen.

 

How it Works

The NozzleX uses passive suction to remove organic matter like debris and sediment from the filter screen. Through an innovative combination of consistent force and passive pressure, whereby the nozzle both actively removes material from the filter while allowing the naturally occurring changes in pressure to carry it away, this nozzle makes cleaning your filtration system an easy and automatic process.

This patented system moves around the filter screen automatically, using as little as 1/32nd the force of typical cleaning nozzles to offer a thorough cleaning with minimal wear. Then, the nozzle disposes of reject water through the system’s flushing chamber, guaranteeing that buildup won’t remain on your screen.

NozzleX is part of Filtersafe’s Everclear cleaning system, which includes the Smartweave screen filter. Working together, these two technologies provide exceptional filtration power while minimizing space. This ensures that operators can use their filtration system as long as possible.

A Closer Look At Other Nozzles

NozzleX vs Dynamic Spring-Loaded NozzlesFiltersafe nozzle nozzlex force chart

While Filtersafe relies on its patented proximity nozzle to consistently clean the screen at any pressure, dynamic spring-loaded nozzles use brute force to ensure their nozzles clean sufficiently at low operating pressure. More force means that both the nozzle and screen wear out faster, in fact, some dynamic spring-loaded nozzles need to be replaced every few weeks!

Floating & Brush-Loaded Nozzles vs Patented Proximity Nozzle

Some nozzles ‘float’ along the screen, never coming into contact with the screen. This reduces nozzle wear but decreases cleaning efficiency and in fact allows dirty backflow to slip out of the nozzle back into the filter’s interior, since there isn’t enough pressure keeping the dirty water inside of the nozzle head and moving towards the flush valve. Brush-loaded nozzles are intended to provide more ‘elbow grease’ to the nozzle’s cleaning capacity. However, the bristles wear out incredibly quickly, leaving the filter owner with what is essentially the previously described undesirable floating nozzle. Even before the bristles break and deform, they can push particles into the screen.

 

The Patented Concept That Sets Us Apart

Our nozzle is one of the most highly engineered aspects to our filter. Let us explain how this simple yet unique design provides the most effective and durable nozzle available.

Efficient Design

Each nozzle contains just 4 individual pieces. The low number of moving parts reduces the opportunities for something to break. In addition, you will not find a spring anywhere inside our nozzles! While other nozzles use springs to force the nozzle head close to or onto the screen when there is low operating pressure, our patented nozzle design equalizes the pressure inside and outside of the nozzle head, allowing it to be on the screen without utilizing damaging force.

Optimal Screen Interface

Because the nozzle is always firmly on the screen with minimal force, it causes absolutely no damage to the screen. Firstly, the nozzle is always applied with minimal, gentle force on the screen at all pressure ratings, and always less than 350 g/cm2. This means that the nozzle does not push dirt and suspended solids into the screen. This is a not uncommon occurrence that not only reduces the filtration capability of the screen, but can also create holes and invalidate the promised micron rating.

 

Additional Benefits of NozzleX

In the world of water filtration, NozzleX is truly a revolution. This unique cleaning tool offers several significant benefits to an automated filtration system, which can make a real difference in the quality and longevity of a system. Here are just a few of the unique benefits you can get from using NozzleX:

Continual System Operation

Firstly, NozzleX runs as part of the automated filtration system. There’s no need to halt system operation and clean out your filtration screens; instead, NozzleX will clean your screens throughout the filtration process.

Minimal Surface Area

In addition to its consistent cleaning functionality, the NozzleX is exceptionally compact. The nozzle takes up a mere 1% of the screen area, which allows your filtration system to continue running even while it’s being cleaned, and without significantly hindering the flow rate. This will result in greater filtration capacity and greater overall efficiency for your system.

Improved Performance

Dirty or clogged filters can have a serious impact on a filtration system’s efficacy. In fact, Filtersafe testing has shown that some systems lose performance in as little as six hours due to a buildup of a ‘cake’ like layer of dirt. In that time, a system’s flow rate can drop 37%, but NozzleX maintains a consistent flow rate throughout its operations. With NozzleX, your system always fully recovers so you’ll be able to get the optimum performance from your filtration system all day long.

Zero Screen Wear

Finally, one of the greatest benefits NozzleX provides is the way it minimizes screen wear. Other nozzle-based cleaning systems use significant force to remove debris from their filters, which can lead to punctures and other damage that cuts the screen’s lifespan short. NozzleX, in contrast, equalizes system pressure to use far less force — around 1.6 Bar (23psi) of head pressure. This means your filter screens suffer next to zero wear, allowing them to operate much longer than other screens.

Filtersafe nozzle cleaning screen

Let NozzleX Clean for You 

NozzleX ensures that a filtration system stays clean throughout operations, thereby making sure that the system remains effective and efficient. As part of Filtersafe’s Everclear system, NozzleX will provide users with a completely clean filter screen — and that will help guarantee superior performance from your filtration system.

To learn more about the NozzleX cleaning technology, contact Filtersafe today. Our team will be happy to answer questions and help you find the system that best suits your industry and your organization’s unique filtration needs.

Advancing filtration standards in the ballast water industry

E Series Filter BS-804E

Filtersafe boosts filtration standards in the ballast water treatment industry by removing 316L grade stainless steel from its filter supply chain

 

Commitment is part of Filtersafe’s $10m market-feedback program and will see the company manufacture its filter screens with the more durable 904L grade steel

 

ISRAEL; Monday 15th February 2021:  Filtersafe, a world leader in automatic seawater filtration, has today announced the removal of 316L grade stainless steel from its supply chain for ballast water treatment system (BWTS) filters. The commitment will see Filtersafe switch to 904L grade stainless steel at its manufacturing facilities in Israel and Hong Kong, which produce filters for around 25% of the global BWTS market. Filtersafe’s pledge comes as the company introduces a plethora of technology upgrades as part of a $10m market-feedback program designed to boost the quality, durability, and turnaround time of BWTS filters – all without impacting filter affordability.

 

Founded with the aim of tackling the world’s most complex water filtration challenges, Filtersafe supplies filters to many of the shipping industry’s leading BWTS manufacturers including De Nora, Ecochlor, Group, Evoqua, ERMA FIRST, SunRui, TeamTec, Techcross, and Wärtsilä. The initiatives announced today mark a step-change for Filtersafe, as the company aims to enhance the agility of its maritime business in response to the shipping industry’s increasingly dynamic regulatory and operational landscape.

 

Until now, 316L steel has been widely used across the global maritime industry as the material of choice for BWTS filter screens. However, the alloy is prone to early pitting corrosion, which can compromise the overall effectiveness of the filter and the entire BWTS. In contrast, 904L steel is up to 82% more durable, meaning it can more effectively support the longevity of filter systems, as well as lowering maintenance costs. To guarantee the quality of steel used in its filters, Filtersafe has invested in two x-ray fluorescence (HHXRF) analyzers that will enable the company to carry out positive material identification (PMI) testing on every metal alloy that enters its manufacturing facilities.

In addition to the x-ray analyzers, other upgrades that form part of the $10m market-feedback program include an FS laser cutting machine designed to improve repeatability in the manufacturing process, thereby minimizing the margin of error and further reducing the possibility of filter screen corrosion. A newly digitalized warehouse system also brings additional accuracy to the manufacturing progress, adding an additional layer of quality assurance as well as optimizing the production line so that filters can be delivered in four to six weeks – the fastest lead time in the global maritime industry.

Commenting on Filtersafe’s latest initiatives, Mark Riggio, Head of Marine at Filtersafe, said: “With ballast water regulations maturing and the global maritime industry shifting its focus to operational compliance, the critical role of filters within overall the BWTS has really come to the fore – with ship owners increasingly understanding that a strong and robust filter is critical to overall system reliability.

 

“As the core material used to build filters, stainless steel should be viewed as a key factor in determining a filter’s long-term performance; it is the first critical building block from which ship owners can realize greater value from their BWTS. By being the first manufacturer to transition away from 316L grade steel, the typical steel used in maritime applications, to 904L we hope to elevate standards across the entire industry and deliver a more efficient balance between filter durability and affordability. At the same time, we’re making a huge effort to introduce new technologies and systems that instill quality across the entire filter supply chain, from start to finish, creating better value for BWMS manufacturers, as well as ship owners and operators.”

 

Commenting on Filtersafe’s decision to use 904L grade stainless steel to produce its filter screens, Marcie Merksamer, Vice President at EnviroManagement, Inc, said: “Filtersafe’s switch from 316L grade stainless steel to 904L is a step-change for the maritime industry. The move will not only increase the longevity of Filtersafe’s filters but also minimize maintenance and increase the run-time of ballast water treatment systems (BWTS). This, in turn, improves OPEX for both BWTS manufacturers as well as shipowners, as there will be less potential for system failures.

 

“Filtersafe’s investment in developing and improving technology demonstrates the company’s commitment to providing quality BWTS filters. With the implementation phase of ballast water regulations underway, shipowners need confidence their systems are meeting the requirements. New innovations, including the introduction of 904L steel, will play a key role in supporting compliance. With more data available to measure and drive progress, ongoing ballast water treatment research and development is more essential than ever.”

 

Following the introduction of the 904L steel and supporting technology at Filtersafe’s manufacturing facilities, the company is working on an industry outreach program that will see it work with BWTS manufacturers to assess the performance of filters currently in operation. Filtersafe intends to extract lessons learned and share them with others in a further bid to increase standards across the industry. The industry outreach program is underway now and is set to accelerate once the COVID-19 pandemic subsides and international travel mobility improves.

 

 

How Does Filtration Purify Water: Filtration processes across the spectrum

Membrane Filtration Spectrum Infographic

Clean water is essential for all living things. Humans, animals, and plants all need clean water to live — which is why water filtration is a massive industry today. Whether you’re watering crops on a large farm, pumping ballast water at a foreign port, or simply getting a glass of water from your refrigerator, you are likely to be using water that’s gone through some form of filtration.

As the name suggests, filtration “filters out” harmful substances from our water, making it debris-free and usable in commercial systems. But how exactly does this process work? The answer depends on the type of filtration system you use.

Why Water Filtration Matters

Before we can discuss how filtration purifies our water, it is first important to understand why we filter water at all. According to the United States Geological Survey (USGS), water is a “universal solvent” — in other words, it can easily dissolve a great number of other substances.

While water solvency makes it an effective cleaning tool, it also makes it easy for contaminants to combine with the water itself. Debris, bacteria, and microorganisms can make themselves at home, and this can cause real harm to plants and animals who are exposed to contaminated water.

Membrane Filtration Spectrum Infographic
This membrane filtration spectrum chart shows the process of separation for various materials at increasingly smaller sizes.

Filters are necessary to protect your system from any debris or other contaminants in your water. If particles manage to get into a system, the equipment can suffer from buildup, clogging, and a host of other issues that can shorten the lifespan of the machines. In fact, these risks are so great that many organizations also implement a prefiltration stage. Systems that use ultrafiltration, for example, often use prefiltration to keep out larger particles and protect their primary filter from clogs or other damage.

For people working in industries like agriculture, water treatment, desalination, and much more, having clean water is vital to keeping your customers healthy and your business thriving. Therefore, these industries must rely on filtration to keep their water in safe and healthy conditions.

How Filtration Helps

Simply put, filtration removes the impurities from water, nearly eliminating the risk from any debris or particles that might have been present. This results in filtered water that is cleaner and purer than in its original state, making it safe for use in ballast tanks, industrial systems, and much more.

Filtered water can help prevent contamination of other things. For example, farmers use filtered water to prevent chemicals or bacteria from changing the pH levels in their soil. pH balance is a key component in growing various crops, and therefore farmers cannot have unexpected contaminants changing their soil composition.

Similarly, filtration is necessary for cargo ships that plan to dump ballast water at their next port. The ocean is a wide and varied ecosystem, and microorganisms from one area could drastically alter the ecosystem in another place. Filtering ballast water before dumping it at a port will prevent animals or bacteria from entering a new part of the ocean and drastically altering its biodiversity.

Ultimately, any industry that uses water to run their business can benefit from filtering their water before use. Investing in filtration will result in cleaner and safer water for everyone.

How Filtration Works

Water filtration has been a part of society since 500 B.C.E. when the Greek scientist Hippocrates developed a cloth filter for purifying water. Since that time, humans have developed and tested countless filtration methods for their water, from boiling it under the hot sun to using charcoal to chlorine to kill microorganisms.

But how does filtration work today? Some of the earliest filtration methods (like charcoal filters) are still used in some capacity. However, modern technology has opened the door to a wide range of different filtration methods. The most common filtration systems are:

  • Particle Filtration (two types are discussed below)
  • Membrane Filtration
  • Reverse Osmosis

Particle Filters

Screen Filters

One of the most common types of water filtration system is a screen-based filter. The vast majority of all commercial and industrial filtration systems first start with a screen to filter out as much suspended material as possible, before heading to treatment or use.UF and RO pre filtration

Screen filters use a mesh screen (usually made from polyester or stainless steel) to trap dirt, sediment, and other debris that might be in the water.

Screen filters were one of the earliest filtration tools developed by mankind, and they remain a highly effective method for purifying water even today. However, it is important to note that screen filters have one major drawback: they’re a flat, 2-D system. The standard screen filter doesn’t have any depth, and that means that the screen can become clogged very easily. Many get around this issue by regularly cleaning the filter – either by removing and cleaning it routinely or by using a self-cleaning system that removes debris automatically and keeps the screen fully functional throughout its life cycle.

There are different levels of screen filters that use varying sizes of mesh, which allows you to determine how many particles your filter captures. Additionally, some manufacturers, including Filtersafe, have created multi-layered screens, which capture a greater number of contaminants as the water moves through them. These tools make removing sediment, sand, and microorganisms a quick and painless process, thereby making it easier to have clean and pure water for your operation.

Candle Filters

Candle filters are another approach for removing fine particles.

Also known as backwashing tubular filters, candle filters are not automatic like many screen filters are, instead of using gravity to produce clean water. Named for its candle-like shape, this filtration system uses a filter cartridge (which is usually made from ceramic or a fine sieve) to filter particles out of the water as it runs through the filter. This system can be an effective way to eliminate sediment, bacteria, and other particles from your water, though most industrial users prefer automatic filtration systems.

Membrane filtration: Micro-, Ultra-, and Nanofiltration

When filtration needs to be done to a much finer degree than particle filters can manage (below 10 microns), membrane filters are the solution (though screen filters are the first step for filtering water, before they pass through membranes). This means that the system uses hydrostatic pressure to force water through a membrane; as the water passes through, any particles or contaminants in the water become trapped, resulting in pure filtered water.

There are three main types of membranous filtration: microfiltration, ultrafiltration, and nanofiltration. While these three types use the same process to filter water, they differ in the size of particles they can trap. The key difference is the size of the pores in each membrane:

  • Microfiltration membranes have a pore size of around 0.1 microns, which means it can catch particles, but not dissolved substances. Microfiltration (MF) membranes developed specifically to solve complex process challenges such as microbial removal, protein fractionation, and pretreatment to other membrane processes. Microfiltration membranes have the most open pore sizes of all polymeric membranes. With a pore size range of 0.1 to 10μm, microfiltration membranes are capable of separating large suspended solids such as colloids, particulates, fat, and bacteria, while allowing sugars, proteins, salts, and low molecular weight molecules pass through the membrane.
  • Ultrafiltration membranes have a pore size of around 0.01 micron, which means it can catch smaller particles and smaller contaminants such as viruses. However, ultrafiltration cannot trap dissolved substances.
  • Nanofiltration membranes have a pore size of 0.001 microns. As one of the smallest pore sizes available (only reverse osmosis membranes are smaller), this filtration type can trap virtually all organic matter, multi-valent salts, and other particles in the water. In addition, nanofiltration membranes are capable of rejecting multivalent salts and larger molecules, while selectively rejecting varying amounts of monovalent salts.

 

Reverse Osmosis (RO) Filters

The term “osmosis” refers to the phenomenon of a solvent (like water) passing through a semipermeable membrane into a solute or dissolvable substance. When this happens, the water will dissolve and “pick up” some of the solute molecules, resulting in a water-and-solute mixture that is equally concentrated on either side of the membrane.

Reverse osmosis, as the name suggests, reverses this phenomenon – removing particles from a water source through the use of a membrane. This type of filer is most commonly used for desalination in conjunction with a media filtration or ultrafiltration system as a prefilter.

In reverse osmosis, the semipermeable membrane (which is most commonly made of cellulose acetate) does not allow the water to dissolve the solute; instead, it acts as a barrier that keeps material such as minerals or microorganisms from passing through the filtration system. Through this method, you can get purified water that is debris free. The membranes are very delicate and need an additional layer of filtration to protect them from debris that can puncture, or biofilm that can contaminate the water. Typically, this filtration is done by cartridge filters, but using Filtersafe’s automatic self-cleaning filters instead is both more sustainable and brings significant cost savings to desalination plants.

Compared to traditional filtration technologies that rely on a screen or filter to remove particles, reverse osmosis (RO) is a pressure-driven separation process that employs a semipermeable membrane and the principles of crossflow filtration.

Reverse osmosis water treatment provides the finest level of filtration. The RO membrane acts as a barrier to all salts and inorganic molecules, as well as organic molecules with a molecular weight greater than approximately 100 Da (Daltons). It is therefore a highly effective process for removing contaminants such as:

  • Endotoxins/pyrogens.
  • Insecticides/pesticides.
  • Herbicides.
  • Antibiotics.
  • Nitrates.
  • Sugars.
  • Soluble salts.
  • Metal ions.

Get the Best Filtration System for Your Needs

There are a variety of water filtration systems available today, and they each serve a unique purpose. Whether you are purifying water for a water treatment plant, to nourish your crops, or for any other industrial purposes, it is critical to have the right tools at your disposal to do your work effectively – and that means finding the right filtration system for your needs.

And no matter which filtration technology you use for your system, you will need a prefiltration screen to protect and increase your system’s lifespan. A simple prefiltration system will prevent excess wear and tear on your machinery and save you in maintenance costs! Filtersafe has over 30 years of experience in advising and supplying the best system for your needs, helping you protect your systems and reduce costs and downtime. Contact us today to learn how our team can help your facility get cleaner, better water.