Commonly used Cleaning methods for filter elements

If you are considering the filter from HYDAC Process technology, choose the following factors:

·         Inline filters in single and duplex versions

·         Strainer filters in single and duplex types

·         High pressure filters in stainless steel

·         Automatic backflushing filters

·         Filter systems with combinations of wide range of components

There are main design principles that should be taken into consideration:

a.       Material resistance to the medium, for which variety of materials and solutions are chosen.

b.      Flow rate

c.       Pressure

d.      Pressure drop

e.      Temperature

f.        Connection sizes

g.       Filtration rating

h.      Economic factors

The core of every filter is the filter element. It provides solutions for the varied filtration applications, diverse filter materialsof sintered wire mesh and element models are chosen. Many filter materials can be cleaned, hence preventing the significant costs of purchase and storage.

Filtration Process

Nominal filtration rate: The filtration ratings are based on a factory standard filter test, that is conducted by introducing a large magnitude of dust, in the beginning of the filter test and after separating the contamination particles over 60 minutes. The test filter retains 90 to 95% of all particles larger than the specific filtration rating.

Absolute retention rate: The filtration ratings are found by the multi-pass test performed on the test rig. At nominal 99% of particles larger than the specific filtration rating should be helped and this up to the maximum permissible differential pressure across the filter element.

Cleaning Filter elements

The filter elements should be divided into cleanable and noncleanable filter materials. The selection of filter materials should be made as per economic, ecological and system specific factor. For process filtration, a cleanable filter material is often used.

The selection of cleaning methods is based basically on the type of contamination and filter material. For a better cleaning effect, specific processes can be combined together. It ensures that the cleaning parameters and selected solvents do not corrode the filter material.

Not all types of cleaning can be performed by the operator. Specialized firms can perform this by using cleaning elements. Common cleaning methods used are:

High pressure cleaning: Fit for cleaning coarse and loose particles manually and automatically with high pressure jets.

Ultrasound cleaning: Cleaning filter elements in ultrasound bath works by breaking down and flushing the contamination particles that is embedded in the element. The ultrasound bath is conducted in the range of 20 to 40 kHz using water and surfactant additive. Or specific solvents can be used.

Scalding in solvents: Scalding of the filter elements used where the elements are kept in a closed circuit, acting as a rinsing machine. The system operates with solvents at the elevated temperatures.

Scalding of the filter elements used where the elements are kept in a closed circuit, acting as a rinsing machine. The system operates with solvents at the elevated temperatures.

Pyrolysis: This cleaning method is based on the degradation of organic material that has accumulated on the element. The organic material is vaporized at high temperatures in a low oxygen condition. 

Corrosion performance of Incoloy 825 and Monel 400 in sulfuric acid

The corrosion resistance of precipitation hardening stainless steels is based on their structure and chemistry. Aging causes chromium carbide precipitation and reduces corrosion resistance. There are various alloys in this classification.

As end grain and side grain corrosion occurred to a larger extent on the bar stock than on the sheet samples, the corrosion rates on the bar samples were much higher than on the sheet samples.

Manganese and nitrogen have austenite stabilizers and in durations of short nickel supply, these elements have replaced a part of nickel in austenitic stainless steels. Normally, the corrosion resistance of SS 316, 216L is superior to SS 316, SS 316l. Although in dilute sulfuric acid, nickel is an essential alloying element and the corrosion resistance of SS 216 is lower to SS 316.

Besides to stabilizing austenite, manganese and nitrogen reinforce austenitic stainless steels and enhance resistance to abrasion and galling.

Incoloy 825 has outstanding resistance to sulfuric acid, particularly in the concentration range of 40%. It provides suitable performance in sulfuric solutions to 40% at atmospheric boiling temperature, to 78% concentration at 80oC and in all concentrations of the acid up to 65oC or 150oF. It is stabilized against carbide precipitation by inclusion of titanium so that it can be used in the as-welded condition.

Corrosion rate of Incoloy 825 is independent of specific heat of alloy or if the corrosion analyses were conducted in technical grade. The corrosion rate was based on the type of condenser used for the test equipment. Metal ions exist in acid from dissolution of the stainless steel act as oxidizing agents and lower the corrosion rate by a factor of about 10. This prevention was independent of the concentration of dissolved stainless steel in the range of 5 – 50 g/l of dissolved stainless steel. This influence was higher than that received by bubbling air in the solution, feasibily due to the limited solubility of oxygen in the boiling acid solution. It also shows that prevention could also be achieved by anodic protection.

Corrosion rates were about the same in liquid and vapour on samples of 1/4^th inch thick plate welded by the Tungsten insert-gas process.

Use Monel 400 bar for handling sulfuric acid is popular in reducing conditions. It provides an alternative to stainless steels and other alloys of similar behaviour when the sulfuric acid solutions are not firmly oxidizing. Alloy 400 attains low corrosion rates in air-free sulfuric acid up to 85% concentration at 30oC and about 60% concentration at 95oC. At the boiling temperature, Monel 400 has supreme resistance to 20% sulfuric acid concentrations are nominal.

While air saturation speeds up the corrosion of Monel 400 in various applications the corrosion rate will be approximate to the air-free rates as continuous air saturation is rare.

The rate at which air can be reused at a quite solution air interface is nominally compared to the rate at which oxygen can be eliminated by corrosion. As a result, in an open tank, a high level of aeration would occur only at the liquid line.

Decorative Wire Mesh Screens for Operational Structures

Heanjia is specialized in weaving and fabrication of comprehensive line of mesh cloth. Many mesh specifications are made using different metals like mild steel, stainless steel, aluminium, copper and super alloys. Our screens provide flexibility in design, uniform fit and minimum waste. Combining different mesh patterns, different metals, custom sizes and shapes allow a designer a wide range of flexibility.

Different metal surfaces of mesh screens create optical contrast with other materials. The screens it takes on the color of surroundings and reflects them. Used indoors or outdoors, mesh screens assist to merge design and environment.

Wire mesh terms

Mesh: Number of openings in a lineal inch measured from the center of one wire to point one inch distant.

Clear opening: Space between adjacent parallel wires.

Crimp: Corrugations in wires to allow locking in place when perpendicular to each other.

Double crimp: Wires pre-crimped before weaving, wires in every crimp

Slotted opening: Weave where the wires are organized to offer rectangular openings.

Material Properties

Sizes: The architectural wire meshes can be developed to required specifications. It allows in preventing many measurement restrictions. Standard applications without seams are possible with materials having own stability.

Resistance to corrosion or weathering: Choosing a stainless steel or aluminium, corrosion and weathering are virtually eliminated in any condition.

Nominal maintenance: Mesh needs no special maintenance after its configuration.

Sound absorption: Outstanding acoustic values are attained mesh is used for suspended ceilings and wall covers. Sound is obstructed through mesh structure.

Flexibility:  Different requirements can be met by using mesh. Air and light can pass through large opening weaves or can be limited with tighter and smaller holes.

Flammability: Mesh screens are not flammable hence they can be used in residential, commercial and domestic buildings without concerns for the fire.

Turn your place from drab to dramatic. Hide mechanicals in plain sight with bold shapes and colors. Make you place memorable. The possibilities are numerous. With unlimited shape options, a modern, aesthetic profile is added providing clear and pen sightlines.

The contoured screens provide an attractive contrast to the wing shaped roofline, that blend harmoniously with a wide expanse of glass, adding light, airy and attractive look. The horizontal screens have an added bonus of helping to reduce sun glare and heat gain like sunshade.

The screen profile adds a strong exterior providing great lift from clean and graceful lines. Although conventionally used on the rooftop as a visual barrier for mechanical system, the screen clothes look graceful. Made from extruded aluminium in different styles, they are long lasting, economical and attractive and needs nominal maintenance.

Using architectural decorative wire mesh screens, parking structures are made to not look like parking structures. The screens add one step further in the beauty of parking structures maintaining the ventilation and vision control properties. Heanjia has extensive experience in designing screening systems to meet specific parking requirements like free area, load and fire resistance. Use of durable decorative screens reduces the magnitude of material required as well as labor that adds up to an economical way to add texture and span. 

Why Nickel base superalloys are recommended for high stress applications

The nickel base super alloys used for jet engine structural components are subjected to high stresses and extreme environmental conditions. At the high temperatures in the jet engines, molten salts form, and thin films of salt coat the internal components. An extremely corrosive gas phase comprising of oxygen, SO2 and SO3. A combination of stress and corrosive environment results in decreased component life and eventual failure. Research on high temperature materil properties and environmental degradation is a crucial part of the technology base for engine life prediction and alloy development.

This study evaluates the effect of a molten salt condition on the high temperature creep properties of Inconel 718. Sustained-load creep tests were conducted at a temperature about 1472oF, in lab air at stress levels about 10 ksi – 30 ksi. High strength round Inconel bars are coated with 90% Na2SO3/ 10% NaCL salt mixture by spraying a heated sample with an aqueous salt solution.

Creep data is studied over a 72 hour test period. Tests conducted with salt coated samples were compared with tests  conducted with uncoated samples.

Degradation of high temperature creep properties of Inconel 718 due to the presence of molten salt. It is because of primarily to oxide penetration in metal that has been depleted of alloying elements and after cracking oxide-metal interfaces. Additionally, grain boundary sliding and void developed along the grain boundaries occurred in the alloy- depleted region of corrosion attack. The influence of stress in the corrosion process and the microstructural changes and mechanisms that occur during corrosion mechanical property interactions .

Static hot corrosion tests on samples were also conducted. Cylindrical pins were salt coated and analyzed for 72 hours at a temperature of 1652oF in lab air.

Nickel base super alloys are high temperature, heat resistant alloys retain high strength in the temperature range of 1400oF to 1000oF. These complex alloys have supreme oxidation and corrosion resistance and supreme resistance to creep and cracking at high temperatures. Nickel base super alloys are precipitation hardenable alloys. The major phase of these alloys is gamma phase and gamma prime phase and carbides. The phase is reinforced by solid solution elements like chromium, molybdenum, tungsten, cobalt, columbium, titanium and aluminium.

Iron in the austenitic matrix decreases the cost and enhanced workability and weldability, however it also significantly lowers the strength and oxidation resistance of alloy. The gamma prime phase can be precipitated in nickel-phase super alloys by precipitation hardening heat processing. Gamma prime precipitate in high nickel matrices is usually the intermetallic phase Ni3(Al,Ti). In presence of cobalt, it replaces nickel as (Ni,Co),(Al,Ti).

The gamma prime phase has outstanding long term stability and a high volume fraction of gamma prime provides the significant high temperature strength. As carbides are harder and more brittle than alloy matrix, their distribution along the grain boundaries will influence the high temperature strength, ductility and creep properties. If continuous chains of carbides extend along the grain boundaries, grain boundary sliding will be prevented. Wide stresses will develop during deformation and result to premature failure along the regular fracture paths at the carbide interfaces. 

Durable woven mesh filtration media for heavy duty applications

Replacement of sensitive, low-grade filter components is common place. The automatic self-cleaning filters are used in upstream of UV disinfection systems. High grade alloys are used in saline lake beds, shipboard reverse osmosis desalination, plant desalination, and designed water applications to minimize replacement components due to corrosion, to enhance sustainability and decrease maintenance and labor costs.

Applications

·         Petrochemical

·         HVAC

·         Metal works

·         Seawater

·         Water-car wash

·         Food processing

·         UF pre-filtration

·         Membrane safety

·         Drinking water

·         Wastewater

·         Recycled water and reuse

·         Desalination

·         Golf- turf

·         Agriculture

·         Greenhouse

·         Nursery

100% of particles removed above the degree of filtration, even one can also receive a significant particle reduction of 25 to 50% in 5 to 50 micron size due to the filter cake effect. The filter cake effect simply shows the fact that degree of filtration becomes finers as a screen accumulates dirt. It explains 25% reduction in particles at 5 to 15 range.

Advantages

·         Automatic backwash

·         No need to replace cartridges

·         Less system downtime

·         Less time used on regular maintenance

·         Nominal water used for backwash

·         Durable stainless steel design

·         Predictable solid filtration barrier

·         Does not need a minimum velocity

·         Removes solids, irrespective of density

·         Static filtration barrier

·         Higher flow rates

·         Robust MOC

Custom automatic self-cleaning water filter for shipboard reverse osmosis desalination, the custom fabricated sintered wire mesh filter screens are developed using duplex stainless steel to withstand corrosive seawater conditions.

Advanced automatic self-cleaning filters used in the reverse osmosis desalination system, conventional solid-liquid separation technologies in various aspects including decreased service costs. The level of pre-filtration allows continuous operation without any reduction in system performance or increase in service costs or maintenance.

Surface finishes and processes

·         Mill finishes

·         Mechanical smoothing

·         Sandblasting

·         Beadblasting

·         Electropolishing

·         Chemical vapour deposit

·         Hydrogen annealing

Second generation of duplex steels was developed with enhanced welding properties through nitrogen alloying. Common duplex grade is 2205 that has a nominal composition of 22% chromium, 5% Nickel, 3% Molybdenum and 0.16% Nitrogen. The steel is used in varied applications in a wide range of product forms. Various grades have become popular for their chromium and nickel concentrations. Alloy 2205 is a nitrogen improved duplex stainless steel grade. Nitrogen significantly improves the corrosion resistance properties that also include a yield strength that is more than double of conventional austenitic stainless steels particularly in the welded condition.

Earlier duplex grades had medium resistance to general corrosion and chloride stress corrosion cracking, however experienced a major loss of properties when used in the as-welded condition. Duplex 2205 stainless steel offers corrosion resistance in various conditions that is better than SS 304, 316 and 317 austenitic stainless steels. The duplex stainless steel is usually used in the form of welded pipe or tubular components and formed sheet product and welded sheet product in conditions where resistance to general corrosion and stress corrosion cracking is crucial. High strength develops opportunities for reduction in tube wall thickness and prevents damage. 

Welding Procedure of Nickel base superalloy Inconel 718

Inconel 718 is age hardenable because of the inclusion of columbium instead of titanium and aluminium as present in other nickel base age hardenable alloys. Studies have described that Inconel 718 is hardened basically by Ni3(Al-Ti-Cb), a columbium bearing gamma prime. It is special in this fact. Due to its particular age hardening properties, Inconel 718 is welded in the age hardened condition and in more highly restrained conditions than the other alloys. In regions up to minimum 0.5 inch it is not essential to use stress-relief treatments after welding. Some heat affected zone softening is occurred when welding the hardened alloy. The sluggish precipitation of submicroscopic age hardening columbium bearing compounds allows annealing and welding without extreme hardening during heating and cooling.

The usual joint preparation and cleaning needs are feasible to Inconel 718. Fusion welding often is done by the inert gas tungsten gas tungsten arc process. Good gas coverage on face and root of the joint is needed. Various filler metals are evaluated for Inconel 718. Inconel 718 and Hastelloy X are some of them. When the joints are restrained, Rene 41 is the recommended filler metal because of the higher melting point.

General electric has also evaluated the weldability of Inconel 718 by using a circular patch weld restraint test. The outcomes showed that the alloy could be welded and heat processed under restraint without cracking. The material was 0.063 inch thick was the filler metal used. Tensile and rupture properties were determined. The joint efficiencies received for tensile and 100 hour rupture life were very good, about 92% for tension tested and 88% for rupture tested welds. The welding procedures were not mentioned.

Welding of thick Inconel bar by a multipass welding technique and the manual inert gas tungsten arc process is evaluated. Sufficient weld joints were made up to 0.5 inch thick. Hastelloy R 235 filler metal provided the best tensile and rupture properties. It was noticed that argon gas in the torch and backup was not sufficient for thicknesses above 0.125 inch. Helium was recommended for the thicker material. Helium allowed better penetration and provided less porosity. Double U- joints were chosen to aid penetration. The weldability of Inconel 718 has made it an attractive alloy for use where age hardenable nickel base alloys are required.

Resistance Welding

 The standard methods of resistance welding are useful for the welding of nickel base precipitation hardening alloys. Low thermal conductivity and high resistivity of nickel base alloys as compared with steel should be taken into consideration when using the welding cycles. The complex heat treatments and high strength of nickel base alloys at high temperatures also influence the welding factors. Cleanliness cannot be over emphasized.

Normally these alloys can be welded using the same welding factors as are implemented for the non-heat treatable nickel alloys. Commonly more pressure and less current is needed. It is due to higher strength and supreme resistance of these alloys. Inadequate pressure results into cracking. Extensive current supply causes ejection of the molten metal.