How to install a Gasket?

Equipment - Clean and Examine -  Align Flanges -  Install Gasket -  Lubricate Load Bearing Surfaces -  Tighten -

The Fluid Sealing Association, (FSA), in conjunction with the European Sealing Association, (ESA), have created a Gasket Installation Procedures pocket book (available in nine languages on the FSA and ESA websites, fluidsealing.com, europeansealing.com) to help installers focus on the key points of proper gasket installation. Following is a summary of the six principal areas of focus in sequential order.Prior to starting any installation, it is important to follow all company safety procedures and policies to ensure the system has been depressurized, drained and de-energized (lockout and tagout procedures) and have all the necessary personal protection equipment (PPE) and tools to help the job go as smoothly and as safely as possible.

At minimum, equipment should consist of:

• calibrated torque wrench or other tightening device

 • wire brush

 • hard hat

 • safety goggles and/or face shield

 • lubricant

 • other plant specified equipment

Step 1: Clean and Examine 

Once the gasket has been removed from the flange, remove any foreign materialor gasket debris from the sealing surface. Using a wire brush, physically remove any material embedded in the sealing face or flange serrations. Be careful not to use a grinder, hammer and chisel, or abrasive material that could further damage the flange sealing surface. Inspect the sealing face for dents, dings, mars or pitting that could cause sealing issues. If there is any noticeable flange face damage, youcan refer to ASME PCC-1 Appendix D—guidelines for allowable gasket contact surface flatness and defect depth, to determine if repairs to the flange are required. Inspect fasteners such as bolts, washers and nuts for defects, cracks and burrs. If fastener components are determined to be defective then discard and replace.Examination Tip: When inspecting bolts and nuts, make sure that nuts run freely over the threads prior to installation to ensure there is no damage to the threads.

Step 2. Align Flanges

To create an effective seal, the installer must ensure that the flanges are parallel as they are brought together. This gives the best chance of applying a uniform maximum gasket load, creating the best seal. ASME PCC-1-2013 Appendix E—Flange Joint Guidelines, gives the recommended allowable limits for:

• flange parallelism

• centerline high/low (the alignment of inner diameter (ID) of the flangebore or outer diameter (OD) of the flange meet)

• rotational-two hole (rotational alignment of bolt holes to allowthe insertion of fasteners without inding)

• excessive spacing, which is defined as when the distance between the two flanges is more than twice of the gasket thickness selected If the system piping requires more than normal force to bring the two flanges together, contact or consult with an engineer. Do not try and over tighten the bolts in hopes of bringing the flanges together.

Alignment Tip:

Avoid using a pry bar or screwdriver to align flanges. Proper tools are available to help with both linear and rotational alignment that are safer and easier to use.

Step 3. Install Gasket

Before installing, inspect the gasket to ensure that it is free of defects and that it was cut cleanly with no rips or tears.

Carefully insert the gasket between the flanges, making sure it is centered between the flanges. In the case of difficult or horizontal installations, never apply release agents or joint compounds on the sealing surface of the gasket. Doing this causes two main problems:

1. The joint is now lubricated making it easier for the gasket to extrude from the flange as a result of internal pressure and hydrostatic end forces that are acting upon the joint.

2. The material can cause a chemical attack on the gasket, compromising the gasket properties and its service life expectancy.

Installation Tip:

For full face gaskets, inserting two to three bolts through both flanges and gasket will help locate the gasket and keep it from moving while bringing the flanges together, reducing the risk of pinching or damaging the gasket.

Step 4. Lubricate Load Bearing Surfaces

Lubrication or anti-seize is a critical step in any gasket installation. It helps with the assembly and in the case of anti-seize, also helps with the disassembly. It is important to consider factors such as temperature, particle type and size when selecting the proper lubrication or anti-seize paste. Without using a high-quality lubricant/anti-seize with a consistent K factor, tightening the bolt to the manufacturer’s recommended torque value will not actually transmit the tensile forces that are required. The application of lubricant is important, and the installer must ensure it is applied uniformly to all thread, nut and

 washer load-bearing surfaces. The installer should also ensure that they do not apply lubricant or anti-seize to either the gasket or the sealing surface. Refer to Step 3 for more information.

Lubrication Tip:

Not sure how much lubrication is enough? If you can’t see it applied on the fasteners from less than five feet away, then it’s probably not enough.

Step 5. Install & Tighten Bolts

Before tightening the nuts, consult the gasket manufacturer for recommended torque values. It is important to ensure that bolt stresses created by the recommended torque are within the allowable limits for the bolting material. Otherwise a failure can occur. When tightening the nut, it is important that the installer try to bring the flanges together in parallel as much as possible.

The best way to achieve this is to always tighten nuts using the legacy method or cross bolt pattern and by using multiple (three to four) tightening rounds during installation. During the tightening rounds, using a gap measurement tool or Vernier calipers to measure the spacing between the flanges is good way to ensure the flanges are parallel during the tightening process. In cases where the gap measurements are not similar, it may be necessary to reduce the bolt torque or untighten a nut in the appropriate location until the flange gap measurement is uniform.

To Tighten:

• Tighten all nuts by hand but do not exceed 20 percent of the recommended torque.

• Round 1: Torque each nut to approximately 30 percent of the recommended torque.

 • Round 2: Torque each nut to approximately 60 percent of full torque.

• Round 3: Torque each nut to approximately 100 percent of the full torque.

• Round 4: Apply at least one final full torque to all nuts in a clockwise position until all nuts are a uniform torque.

Tightening Tip:

It is a good idea to number the bolts in the order of tightening, so that you can easily

follow them for multiple tightening rounds. This is especially important for large diameter flanges that have a lot of bolts. It has been well documented that relaxation in a bolted joint flange assembly occurs within the first four to 24 hours after initial installation due to gasket creep, and bolt and flange relaxation. It is strongly recommended that users retorque within this four to 24 hour window, while the system is still at ambient temperature and atmospheric pressure, before being put back online. In some cases, this simply cannot be done and the system is to be put back online for service immediately after the gasket is reinstalled. In this case, using the maximum allowable torque is recommended to help combat some of the joint relaxation.

At no time is it recommended that an elastomer-based soft gasket material be retorqued after the material has been exposed to elevated temperatures (known as hot torqueing). Doing this with an elastomer-based material can cause the gasket to crack, possibly causing a blowout and severe injuries.

Retightening Tip:

When retightening within the appropriate time frame of four to 24 hours, start at Round 3 noted in Step 5 and torque each nut to approximately 100 percent of the full torque, followed by a rotational round at the final full torque to ensure all nuts are a uniform torque. Doing all of this cannot guarantee that your gasket will not leak, but if you focus on these six main areas, the bolted joint flanged assembly has the best chance of creating an effective and reliable seal. These procedures are for standard flanges. There is some specialty equipment that may require special steps. In all cases, adhere strictly to safety procedures.

(Source: Chett Norton C.E.T. Member of the FSA Technical Gasket Committee 06/2017)

What are Mechanical Seals?

Pump Mechanical Seals - How a Mechanical Seal Works -  Pump Mechanical Seals Components -  Types of Mechanical Seals  - 

Pumps mechanical seals

Mechanical seals are devices which keep or seal the pumped fluid in the pump casing, thus avoiding leakages and costly loss of pumped product. Since approximately 1950s, mechanical seals have almost totally eliminated inefficient and costly gland packings. They are installed at the place where the pump shaft enters or leaves the casing. There are various styles, configurations and sizes of mechanical seals. However, all of them employ the basic principle of stationary and rotating face combinations.

How a pump mechanical seal works

A mechanical seal works though the use of two very flat lapped faces which make it difficult for leakage to occur. One face does not rotate with the shaft (stationary), whereas the second one rotates with the shaft (rotary).
As the faces rub together, a fluid film migration between the 2 faces is applied for cooling and lubrication purposes. The pumped fluid will ideally weep between the faces, entering as a liquid and remaining until it is vaporised as it reaches atmosphere.

It must be pointed out at this point that all mechanical seals leak some very small amounts of vapor and consqequently, even with the best mechanical seal design, a small portion of the pumped fluid is lost.

Pump mechanical seals components

All mechanical seals are typically made of three basic sets of components:

1) A set of primary seal faces: one that rotates and one that remains stationary.
2) A set of secondary seals known as shaft packings and insert mountings, such as O-rings, PTFE or Grafoil wedges, or V-Rings.
3) Various hardware like gland rings, collars, compression rings, pins, springs, retaining rings and bellows.

In general, there are various types of mechanical seals. In terms of design and arrangement, mechanical seals are generally divided into the following categories:
 
- Mechanical seals classification by design
 
- Mechanical seals classification by arrangement

Types of mechanical seals

Inside seals: An inside seal is designed in such a way that the rotary portion of the mechanical seal is located inside the pump seal chamber. With inside seals, the fluid and pressure are exerted on the outside diameter (O.D.) of the seal. Typically, inside seals are used for higher pressure applications compared to outside seals.

Outside seals: An outside seal is designed in such a way that the rotary portion of the mechanical seal is located outside the pump seal chamber. Quite often, outside seals are applied for chemical service in non-metallic parts: the pumped fluid does not come in contact with the metal parts of the seal and as a result, the need for expensive and/or exotic materials is often eliminated.

Pusher seals: A pusher seal is a design which pushes a dynamic secondary seal, which is either an o-ring, wedge or other type of equipment, across the shaft as a means of compensation for face wear and/or shaft movement.

Non-pusher seals: This type of seal is designed in such a way that the dynamic secondary seal is not used. Typically, non-pusher seals are metal bellows or elastomeric bellow seals.

Balanced seals: At balanced seals, the hydraulic pressure which acts to close the seal faces is significantly reduced. Balanced seals present the advantage of generating less heat because of the reduced pressure forcing the faces together. Consequently, they can withstand much higher pressures compared to unbalanced seals.
pic 1 - Balanced Seal

Unbalanced seals: At unbalanced seals, the full hydraulic pressure of the seal chamber acts to close the mechanical seal faces, without any reduction whatsoever. Unbalanced seals are intended for use only in low-pressure applications.

pic 2 - Unbalanced seal

Double seals: In this arrangement, two (2) mechanical seals are used face to face, back to back or in tandem (facing the same direction), thus allowing a buffer fluid or gas to be introduced between the two sets of seal faces. Double seals are mostly used for the purpose of sealing a product that is a volatile organic compound, dirty,non-lubricating, or very viscous. Also, they are used for products that solidify or otherwise change state.
 

What is Compression Packing?

Compression Packing -  Packing Construction -  Stuffing Box -  Test Results -

Compression Packing (A.K.A.: Mechanical Packing / Packing Rope / Sealing Rope)

Packing is braided yarn made from a variety of materials such as graphite, aramid, and PTFE. Many braided packings will also incorporate blocking agents and other coatings to minimize leakage through them and provide cooling and lubrication during startup. The braided packing is cut into rings, inserted into a stuffing box and compressed using a bolted gland. Under axial compression, the packing expands radially, creating a seal between the stationary body of the equipment and the dynamic surface, usually a rotating shaft.The perception is often that this is an outdated technology suited to the steam-powered equipment of past centuries rather than one capable of meeting the needs of modern industry. But nothing could be further from the reality of contemporary packing products. Current technology utilized to design and manufacture high performance ensures that packing will be keeping up, not only with current but also with future needs and requirements.

Packing Construction

Many factors need to be considered for a properly functioning sealing system, starting with packing construction, the fiber utilized for sealing, the reinforcements to prevent extrusion, and the blocking agents and lubricants to prevent permeation and to reduce friction. Then, it is necessary to establish the load sufficient to compress the packing against the stem to achieve sealing while maintaining friction as low as possible.

Packing Braider at Robco Inc.

The fibers used to braid the packing have evolved from natural fibers, either vegetable or mineral, toward high-performance synthetic fibers. Some of the materials that are currently used to make the fibers are carbon, graphite and Polytetrafluoroethylene (PTFE). The fibrous material is then braided into a square shape. Typical constructions are square braid (Figure 1) or lattice braid (Figure 2). Each have their own characteristics in terms of formability and malleability.

Figure 1. Square Braid
Figure 2. Inter-Braided Structure

But a compression packing is much more than braided fibers. Braided mechanical packing is a “system” made of fibers, braid style, lubricants for break-in or blocking, and corrosion inhibitors. General requirements for packing are resilience, chemical resistance, strength and temperature resistance. Compression packing is considered a cost effective sealing solution, particularly in applications with larger shaft diameters for which other sealing options are more costly. The standard packing designs and materials in use today can handle some pretty extreme conditions, i.e. pressures to 500 psi (34 bar), shaft speeds to more than 4,000 feet per minute (more than 20 meters per second) and temperatures to more than 600 degrees F (more than 315 degrees C).

In mining operations, there are applications in which ore slurry has to be moved from the mining site to the processing facilities. This is done with pumps in series that develop enough pressure to move this viscous abrasive fluid long distances. The particulates are abrasive and can wear packing fibers, pump shafts and sleeves and increase frictional heat. The elevated pressure creates high compression on the packing that can increase packing friction and wear, cause extrusion of the packing through clearances between the gland and shaft and make controlling leakage difficult. Leakage control can be complicated at these pressures because small adjustments of the gland bolts can cause drastic changes in leak rate and, subsequently, the frictional heat and operating temperature of the packing set.

Stuffing box

A stuffing box is an assembly which is used to house a gland seal. It is used to prevent leakage of fluid, such as water or steam, between sliding or turning parts of machine elements.
Components

A stuffing box of a sailboat will have a stern tube that's slightly bigger than the prop shaft. It will also have packing nut threads or a gland nut. The packing is inside the gland nut and creates the seal. The shaft is wrapped by the packing and put in the gland nut. Through tightening it onto the stern tube, the packing is compressed, creating a seal against the shaft. Creating a proper plunger alignment is critical for correct flow and a long wear life. Stuffing box components are of stainless steel, brass or other application-specific materials.

Gland

A gland is a general type of stuffing box, used to seal a rotating or reciprocating shaft against a fluid. The most common example is in the head of a tap (faucet) where the gland is usually packed with string which has been soaked in tallow or similar grease. The gland nut allows the packing material to be compressed to form a watertight seal and prevent water leaking up the shaft when the tap is turned on. The gland at the rotating shaft of a centrifugal pump may be packed in a similar way and graphite grease used to accommodate continuous operation. The linear seal around the piston rod of a double acting steam piston is also known as a gland, particularly in marine applications. Likewise the shaft of a handpump or wind pump is sealed with a gland where the shaft exits the borehole.
Other types of sealed connections without moving parts are also sometimes called glands; for example, a cable gland or fitting that connects a flexible electrical conduit to an enclosure, machine or bulkhead facilitates assembly and prevents liquid or gas ingress.

In a common type of stuffing box, rings of braided fiber, known as shaft packing or gland packing, form a seal between the shaft and the stuffing box. A traditional variety of shaft packing comprises a square cross-section rope made of flax or hemp impregnated with wax and lubricants. A turn of the adjusting nut compresses the shaft packing. Ideally, the compression is just enough to make the seal both watertight when the shaft is stationary and drip slightly when the shaft is turning. The drip rate must be at once sufficient to lubricate and cool the shaft and packing.

The market offers improved shaft packing materials that aim to be drip-less when the shaft is turning as well as when stationary. There are also pack-less sealing systems that employ engineered materials such as carbon composites and PTFE (e.g. Teflon®).

Test Standards

Test standards have been developed to validate compression packing emission performance. These require sophisticated equipment for the packing tests per API 622, and for valve emission testing per ISO 15848 and API 624.
One of the areas that has been lagging is the predictability of performance. There is an increasing demand from valve end users for low-emission sealing systems, but it remains important that the valve continue to move smoothly and efficiently. Since the frictional load of the stem packing has a contrary effect on these two requirements, valve and valve packing manufacturers are challenged with respect to the prediction and improvement of packing behavior in a valve.
Development of a Predictability Tool

This is the reason the European Sealing Association (ESA), in collaboration with the Fluid Sealing Association (FSA) and the Fluid Equipment Committee of French research house CETIM (a working group composed of French valve and sealing product manufacturers who initiated this program) are developing a tool to predict the initial packing tightening force required to reach certain characteristics in relation to friction and sealing performance. Part of the project is the development of a testing procedure that determines the packing ring characteristics needed for use in a calculation method for the torque required to achieve certain performance characteristics.

Mechanical tests will be carried out on individual rings, but the test rigs have been developed to be able to test full packing sets up to 6 rings. The application of a gland stress, applying stem movements, heating the stuffing box assembly to the test temperature and then repeatedly reducing the stress while applying stem movements and measuring the friction will generate data to establish a number of parameters, including the ring compression as a function of applied stress, the dynamic coefficient of friction and the axial force to radial force coefficient of transmission. Further testing will generate the ring modulus of elasticity, the relaxation coefficient of the packing ring, the deflection variation over time of the packing ring due to creep and the coefficient of thermal expansion of the packing ring.

The last part of the test determines the sealing performance of the packing. After application of stress on the packing and actuating the stem several times, the leakage is measured by helium mass spectrometry. Then the stress on the packing is reduced a number of times after which the leakage is measured at the lower stress level. This procedure is repeated several times to determine a reliable relational curve between packing stress and leakage.

The test setup consists of a hydraulic cylinder to actuate the stem, a stem movement transmission section with load or torque sensor, a hydraulic press to apply the gland load, and a test cell containing a stuffing box with up to 6 packing rings (Figure 3).
  Figure 3. Test Setup

The test cell can be interchanged depending on whether leakage or mechanical behavior is to be measured. The stuffing box is dimensioned and to tolerance as defined in API622. The sealing test cell is able to measure the leakage rate of 1’’ stem diameter packing for internal helium pressures up to 8 MPa.

The mechanical test cell allows the testing of a variable number of packing rings. It is equipped with strain gauge chains each made of 10 strain gauges to measure the stuffing box external diameter deformation. This enables determination of the value of the axial-to-radial contact pressure transfer coefficient. The test cell is also equipped with a load sensor to measure the transferred axial load to the bottom of the packing, and the three displacement transducers positioned at 120-degree angles to measure the packing deflection.

Preliminary test results show the leakage is indeed dependent on the stress level applied to the packing, and that extremely low leakage levels can be achieved. Figure 5 details the relationship between stress level and leakage rates.

The ISO 15848 Valve Testing Standard sets three classes of leakage performance. Class C was originally intended for graphite packing, class B for PTFE packing and Class A for bellows valves. It can be seen that the highest level of performance, Class A, can be achieved with the right amount of axial compression with 4 graphite rings. Certainly axial loads of 60 and 80 MPa are high, and the valve construction must be such that it can handle these loads without deformation, but these results show how modern packing formulation and manufacture can achieve the most stringent requirements.

Testing of packing in a fixture such as that specified by API 622 is not a guarantee the same emission level will be achieved in a given valve. Factors such as surface finishes, concentricity, tolerances on diameters, bolt stress and deformation under load all affect emission results. After tests have been done to qualify the packing, further tests are then needed to qualify the valve with the packing. But information is now available to predict stress levels required for a given performance level. Cooperation between the valve and packing manufacturers is essential to achieve the best results.

What is High-temperature insulation ?

History - Ceramic-Impregnated Fabric -  Glass Insulation Wool - 

High-Temperature Insulation Wool in Detail

History

Humans have used fire for melting and heat treating metals for thousands of years. To ensure safe working with the fire, for melting and working metals (bronze, iron), special refractory materials were needed to enable the handling of liquid or hot metals. To meet the needs of the wide-ranging applications, a large number of shaped, dense materials (refractory bricks, chamotte), shaped heat-insulating materials (lightweight refractory bricks) and unshaped refractory materials (heavy- and lightweight ramming mixes) have been developed, which are used for special high temperature applications. For decades, however, other manmade materials have been used for thermal insulation, glass wool and rock wool being used in the low-temperature range (around 200 °C to maximum 500 °C).

In the 1960s aluminium-silicate-based "refractory ceramic fibre" were launched on the market in Europe. Due to their high temperature-resistance and good technical properties (i.e. good thermal shock resistance and low thermal conductivity), they quickly became the reference for industrial high temperature insulation. Due to the development of new material types the nomenclature of high-temperature insulation wool was redefined in Germany at the end of the 1990s. (VDI 3469.[1]). Although even today the term "ceramic fibre" or "refractory ceramic fibre" is commonly used it is inaccurate in terms of the materials available, their specific properties and limitations.

Thermal insulation with HTIW enabled a more lightweight construction of industrial furnaces and other technical equipment (heating systems, automobiles), resulting in many economic and ecological benefits. Consequences are smaller wall thicknesses and considerably lower lining masses.

Comparison of the mass for the different wall linings
•    Heavyweight lining: 1500–3500 kg/m³,
•    Lightweight lining: 500–1000 kg/m³,
•    Lining with HTIW: 160–300 kg/m³.

Ceramic-impregnated fabric

Ceramic-impregnated fabric is a fabric that has been impregnated with ceramic. Nanometric bioceramic can be incorporated into the polymer from which the fabric is manufactured. Bioceramic nanoparticles are added to the fused polymer.Some types of ceramics show thermally-induced photoluminescence, emitting light in the far infrared (FIR) region of the electromagnetic spectrum. When in contact with the body heat, the thermoluminescence of the fabrics with embedded bioceramic is enhanced. Bioceramics presents high reflection coefficient for the infrared radiation.

Method of production

One way in which fabrics can be impregnated with ceramic is the process of electrophoretic deposition or EPD in the industry. In this process, nanoceramic particles are put into a solution in which the fabric to be infiltrated will be placed. The solution is then heated to high temperatures and the fabric is placed into the solution. Next, a current is passed through and the nano ceramic particles coat and impregnate the fabric. The pH level as well as the amount of time and amount of current can affect how well the fabric is infiltrated and how it is coated. Other processing methods can be further broken down into what particles will be added.

There are two distinct groups:

•    The SiC group (which contains silicon, carbon as well as additives for oxidation processes). When using this group for the purpose of ceramic-impregnation, the textile must first undergo a treatment. This is usually pyrolytic carbon or BN, which is deposited using a chemical vapor infiltration (CVI). Next, an overlayer of SiC is deposited on the textile using the same method. After this step the matrix of the textile is infiltrated by a slurry made up of SiC particles which can either be put in a polymer or simply molten SiC. This process coats the entirety of the textile.

•    The oxide group. Oxides commonly used are alumina, silica, mullite, and rare-earth phosphates. The process for impregnation is quite simple: a slurry is prepared with the oxide desired and the textile is placed in it. Again, the slurry can be a molten state or a polymer-based one.
There are a few differences between these groups. The SiC group has over twice the fracture strength and thermal conductivity when compared to the oxides group. However, the oxides are more stable in combustion and oxidizing environments. The process by which the textile is impregnated depends on what materials will be used, as well as the intended purpose of that fabric.

Uses

Woven ceramic fabrics allow for the opportunity to create new, imaginative solutions for previously impossible problems. These fabrics are utilized for thermal, mechanical and electrical applications for a variety of reasons. Ceramic-impregnated fabrics are most importantly used in three main fields: aerospace, electronic, and industrial. In aerospace, the fabrics are used in space shuttles for the exit cone, door seals, micrometeorite shield, gaskets, booster access doors, shuttle tiles, and in the Whipple shield. Ceramic-impregnated fabrics are utilized in aerospace because they have low thermal conductivity and can be fabricated into high temperature thermal insulators. In the electronic industry, the fabrics are used primarily for insulation and seals, because of its low porosity. Ceramic fabric's industrial uses include furnace linings, furnace zone dividers, door seals, tube seals, gaskets, and expansion joints. In addition to being an effective thermal insulator, these fabrics do not shrink or elongate with high temperature changes, making them useful for industrial uses that involve high temperatures.

Glass insulation wool

Glass wool is an insulating material made from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties.

Glass wool is produced in rolls or in slabs, with different thermal and mechanical properties. It may also be produced as a material that can be sprayed or applied in place, on the surface to be insulated.
The modern method for producing glass wool is the invention of Games Slayter working at the Owens-Illinois Glass Co. (Toledo, Ohio). He first applied for a patent for a new process to make glass wool in 1933.[1]

Principles of function

Gases possess good thermal conduction properties compared to liquids and solids, and thus make a good insulation material if they can be trapped. In order to further augment the effectiveness of a gas (such as air) it may be disrupted into small cells which cannot effectively transfer heat by natural convection. Convection involves a larger bulk flow of gas driven by buoyancy and temperature differences, and it does not work well in small cells where there is little density difference to drive it.

In order to accomplish formation of small gas cells in man-made thermal insulation, glass and polymer materials can be used to trap air in a foam-like structure. The same principle used in glass wool is used in other man-made insulators such as rock wool, styrofoam, wet suit neoprene foam fabrics, and fabrics such as Gore-Tex and polar fleece. The air-trapping property is also the insulation principle used in nature in down feathers, and insulating hair such as natural wool.

Uses

Glass wool is a thermal insulation that consists of intertwined and flexible glass fibers, which causes it to "package" air, resulting in a low density that can be varied through compression and binder content (as noted above, these air cells are the actual insulator). Glass wool can be a loose fill material, blown into attics, or, together with an active binder sprayed on the underside of structures, sheets and panels that can be used to insulate flat surfaces such as cavity wall insulation, ceiling tiles, curtain walls as well as ducting. It is also used to insulate piping and for soundproofing.

High-temperature insulation wool in detail

High-temperature insulation wool is an accumulation of fibres of different lengths and diameters, produced synthetically from mineral raw materials. The group of the HTIWs include amorphous alkaline earth silicate wool (AES) and alumina silicate wool (ASW) as well as polycrystalline wool (PCW) (VDI 3469; DIN-EN 1094) with a classification temperatures >1000 °C. Besides the differences in the chemical composition, manmade fibres have parallel edges in contrast to natural fibres.

Alkaline earth silicate wool (AES wool)

Also known as “high-temperature glass wool" (HTGW), AES Wool consist of amorphous fibres, which are produced by melting a combination of CaO-, MgO-, SiO2 and ZrO2 (see also VDI 3469, Parts 1 and 5 ). Products made from AES are generally used at application temperatures less than 900 °C and in continuously operating equipment and domestic appliances.

Alumino silicate wool (ASW)

Alumino silicate wool, also known as “refractory ceramic fibre” (RCF), are amorphous fibres produced by melting a combination of Al2O3 and SiO2, usually in a weight ratio 50:50 (see also VDI 3469 Parts 1 and 5, as well as TRGS 521). Products made of Alumina Silicate Wool are generally used at application temperatures >900°C and in intermittently operating equipment and critical application conditions (see Technical Rules TRGS 619).

Polycrystalline wool (PCW)

Polycrystalline wool consists of fibres containing greater than 70 wt.% Al2O3; they are produced by a "sol-gel method" from aqueous spinning solutions. The water-soluble green fibres obtained as a precursor are crystallized by means of heat treatment (see also VDI 3469 Parts 1 and 5[1]). Polycrystalline Wool is generally used at application temperatures greater than 1300 °C and in critical chemical and physical application conditions, also at lower temperatures.

HTIW and REACH

Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) is a European Union regulation of 18 December 2006. REACH addresses the production and use of chemical substances, and their potential impacts on both human health and the environment. A Substance Information Exchange Forum (SIEF) has been set up for each type of HITW. AES, ASW and PCW have been registered before the first deadline of 1 December 2010 and can therefore be used on the European market.

Regulation (EC) No 1907/2006 of the European Parliament and the Council of 18 December 2006 concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) require manufacturers, importers and Only Representatives of non-European manufacturers to share data on potential health and environmental hazard and provide data to the European Chemicals Agency (ECHA) in a formalized registration process.
ASW/RCF, AES and PCW were registered using a joint registration dossier before the first deadline of 1 December 2010. They can therefore be used on the European market. The registration process required that manufacturers, importers of substances >1 t/year agreed on classification, labelling and uses of ASW/RCF, AES and PCW.

The REACH and the CLP Regulation being based on the principle of self-classification by industry; however prior harmonized classification of substances contained in Annex 1 of Directive 67/548 remains valid and has been transferred to Annex VI of CLP. Classification in Annex VI of the CLP Regulation is the mandatory classification; industry has to evaluate whether additional/stricter classification may apply.
•    ASW/RCF is therefore classified as carcinogen category 1B
•    AES is exempted from carcinogen classification based on short term in vitro study result
•    PCW are not classified; self-classification led to the conclusion that PCW are not hazardous

On 13 January 2010 some of the aluminosilicate refractory ceramic fibres and zirconia aluminosilicate refractory ceramic fibres have been included in the candidate list of Substances of Very High Concern. In response to concerns raised with the definition and the dossier two additional dossiers were posted on the ECHA website for consultation and resulted in two additional entries on the candidate list. This actual (having four entries for one substance/group of substances) situation is contrary to the REACH procedure intended. Aside from this situation, concerns raised during the two consultation periods remain valid.
Regardless of the concerns raised, the inclusion of a substance in the candidate list triggers immediately the following legal obligations of manufacturers, importers and suppliers of articles containing that substance in a concentration above 0.1% (w/w):

•    Notification to ECHA -REACH Regulation Art. 7
•    Provision of Safety Data Sheet- REACH Regulation Art. 31.1
•    Duty to communicate safe use information or responding to customer requests -REACH Regulation Art. 33

Definitions

Classification temperature

The classification temperature is defined as the temperature at which a linear shrinkage of 4% is not exceeded after 24 hour heat treatment in the electrically heated laboratory oven and in a neutral atmosphere. Depending on the type of product, the value may not exceed the following limits: 2% for boards and shaped products, 4% for mats and papers. The classification temperature is specified in 50 °C steps (starting at 850 °C and up to 1600 °C). The classification temperature does not mean that the product can be used continuously at this temperature. In the field, the continuous application temperature of amorphous HTIW (AES and ASW) is typically 100–150 °C below the classification temperature. Products made of Polycrystalline Wool can generally be used up to classification temperature.

Wool

Wool is an ordered accumulation of fibres of varying length and diameter. HTIW fulfill this definition and are therefore covered by the term “wool”. Amorphous AES and ASW are produced by melting the raw materials in a melting pot by means of electrical resistance melting. The jet of melt discharged from the pot is accelerated in a blowing or spinning process and pulled into fibres with different length/diameter ratios.
Continuous fibres/textile glass fibres (VDI 3469 Part 1)
These fibres are produced by means of the continuous filament process with defined nozzle diameters, all fibres having the technical defined and required diameter. During handling, only fibres of the given diameter but different length are released.

Health hazards

Fibrous dust - Based on the total experience with humans and the findings of scientific research (animals, cells), it can be concluded that elongated dust particles of every type have in principle the potential to cause the development of tumours providing they are sufficiently long, thin and biopersistent. According to scientific findings inorganic fibre dust particles with a length-to-diameter ratio exceeding 3:1, a length longer than 5 μm (0.005 mm) and a diameter smaller than 3 μm (WHO-Fibres) are considered health-critical.

HTIW processed to products contain fibres with different diameters and lengths. During handling of HTIW products, fibrous dusts can be emitted. These can include fibres complying with the WHO definition. The amount depends on how the material is handled. High concentrations are usually found during removal of after-use HTIW and also during mechanical finishing activities and in the assembly of modules. Where fibre products are mechanically abraded by sawing, sanding, routing or other machining the airborne fibre concentrations will be high if uncontrolled. Dust release is further modified by the intensity of energy applied to the product, the surface area to which the energy is applied, and the type, quantity and dimensions of materials being handled or processed. Dispersion or dilution of dust produced depends on the extent of confinement of the sources and the work area, as well as the presence and effectiveness of exhaust ventilation.

Crystalline silica - Amorphous HTIW (AES and ASW) are produced from a molten glass stream which is aerosolised by a jet of high pressure air or by letting the stream impinge onto spinning wheels. The droplets are drawn into fibres; the mass of both fibres and remaining droplets cool very rapidly so that no crystalline phases may form.

When amorphous HTIW are installed and used in high temperature applications such as industrial furnaces, at least one face may be exposed to conditions causing the fibres to partially devitrify. Depending on the chemical composition of the glassy fibre and the time and temperature to which the materials are exposed, different stable crystalline phases may form.
In after-use HTIW crystalline silica crystals are embedded in a matrix composed of other crystals and glasses. Experimental results on the biological activity of after-use HTIW have not demonstrated any hazardous activity that could be related to any form of silica they may contain.

High-temperature insulation wool (HTIW), -  also known as kaowool (a portmanteau of the words kaolin and wool), known as ceramic fiber wool until the 1990s, is one of several types of synthetic mineral wool, generally defined as those resistant to temperatures above 1000°C. The first variety, aluminium silicate fibre, developed in the 1950s, was referred to as refractory ceramic fibre.

Due to the costly production, and limited availability compared to mineral wool, HTIW products are almost only used in high temperature industrial applications and processes.