Spiral Wound Gaskets Demystified

Oct 10, 2016

Spiral Wound Gaskets are what you reach for when a regular gasket won’t do the job. Regular flat gaskets seal parallel flanges with good surface finish. Over time though, those properties deteriorate and the joint becomes harder to seal. That’s when it’s time to go spiral-wound.

Spiral wound gaskets also work well in high-temperature and high pressure conditions and with corrosive media. That’s why they’re the gasket of choice in many petrochemical plants where their long life helps reduce downtime.

Edge Sealing

Most gaskets are cut from sheet material and that means they seal on their flat surfaces. When flanges are out of parallel the gap between them varies, forcing the use of thicker material. Where the gap is smaller the material must compress more. Pretty quickly the material reaches the limits of what it can do.

In contrast, the spiral wound gasket seals on its edges rather than a flat surface. To do this a long thin strip of gasket material is coiled up to create a ring. Placed between flanges, it’s the sides of the strip that make the seal.

Built-In Spring

To add elastic recovery, ensuring that a seal is maintained regardless of how the joint moves, the gasket material is interleaved with a metal strip. The combined materials are then formed into an approximate ‘V’ section during the coiling process. That metal ‘V’ acts like a spring, pushing outwards against the flanges.

Spiral Wound Gasket Material Options

The choice of gasket material is critical. Usually a spiral-wound gasket is made from PTFE or graphite, both of which come in various grades. In addition, the metal is also selected for the appropriate degree of springiness combined with corrosion resistance and durability.

Spiral-wound gaskets usually come with both an inner metal core and an outer metal ring. These are thinner than the coiled gasket material, so limiting how much the gasket can compress. The inner core also increases blowout resistance; one reason this design works well with high pressures.

For ease of identification, the outer edge of every spiral-wound gasket is color-coded. These codes follow an ASME standard, make it easy to identify and order the replacement part before the joint is taken apart. That helps minimize downtime!

Ask About Going Spiral Wound

The spiral-wound gasket was invented by Flexitallic back in 1912 but today there are a number of manufacturers. The gaskets follow ASME standards but are not all the same as each company has their own materials and designs.

If you have a challenging joint to seal, ask if a spiral-wound gasket would be a good option. If you’re replacing an existing spiral-wound gasket, check the color-code and order the new part before taking the joint apart.  As a spiral wound gasket supplier, Hennig Gasket stocks a large variety of spiral wound gaskets ready to ship.  Contact us today.

Spiral Wound Gaskets
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Custom Gasket Cutting

Sep 26, 2016

At Hennig we provide custom gasket cutting services. If the material is in stock we can usually get a new gasket shipped out the day it was ordered.

The key to this rapid turnaround is cutting process flexibility. With flash, die and water jet cutting equipment on-site we’re able to select the fastest and most cost-effective process for your order. Whether you need one gasket or one thousand, prototype or production runs, we have a process that works.

Accuracy and appearance are important considerations too. A gasket that fits poorly or has rough, uneven edges leaves a negative impression of the equipment it’s installed on, and probably won’t last as long. Our cutting processes provide a range of finishes to suit your needs.

Flash Cutting Services

Flash cutting uses a  gantry machine that moves an oscillating knife over sheet material up to 60” x120”. The knife cuts straight edges or curves in material up to 1/2” thick, leaving smooth vertical edges. Knife motion is computer-controlled with the cutting path programmed directly from a CAD file, and nesting software maximizes material utilization.

Die Cutting Services

A die cutter uses a metal blade shaped to the profile of the gasket and embedded into a wood block or panel. With die cutting it’s possible to cut to a precise depth, which is useful when you don’t want to separate individual pieces from the sheet. Technically described as “kiss-cutting,” this allows gaskets to be kept together on a sheet or roll and peeled off as needed. It’s a good method for producing gasket kits.

Unless a die already exists, die cutting will incur a tooling charge along with some lead time. However, it is a fast and repeatable process, which makes it economical for quantity orders. We can die cut gaskets as large as 36” x 72” from sheet material. Cut edges are smooth although thicker material may show a small degree of curvature.

Water Jet Cutting Services

Also a gantry-style machine, water jet cutting cuts with a jet of fast-moving water just 0.010” wide. The thin jet means minimal material waste, and tolerances as tight as +/-0.007” can be maintained. Depending on the material, it’s possible to cut up to 6” thicknesses and the largest size we can produce is 72” x 96”.

Like flash cutting, a water jet is programmed directly from a CAD file of the gasket required. One strength of water jet is that there’s no material deformation during the cut, which improves edge appearance.

Ask about custom gaskets

Many sealing applications need a custom gasket. At Hennig we have a range of equipment for cutting sheet gasket material and this lets us provide a rapid turnaround. Many custom gaskets ship the day they were ordered.

Gaskets & Seals
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Why Use PTFE Seals in Food Industry Applications?

Sep 12, 2016

Commercial cooking kettles used for boiling and preparing foods usually have a food grade gasket around the lid. By creating a good seal this helps the vessel build and retain pressure. This raises the boiling point of water, shortening cooking time while also destroying pathogens. A defective gasket can result in food not reaching the required temperature, potentially creating a health hazard. Additionally, the gasket itself can provide places for bacteria to become established.

This gasket leads a hard life. Not only must it withstand the heat and pressure of cooking, but it’s also expected to go through multiple cleaning cycles. In addition, it’s essential that it not transfer anything or impart any taint to the food being cooked. Several materials are available for such gaskets, but in many situations the best sealing option is PTFE.

A Versatile Sealing Material

Polytetrafluoroethylene, or PTFE, better known by it’s DuPont tradename of Teflon, has a number of properties that make it an excellent choice for a food grade gasket. At the atomic level it consists of a long chain of carbon atoms, each one of which links to two fluorine atoms. This linkage is so strong that PTFE won’t bond to anything else, hence its non-stick properties.

PTFE doesn’t melt until 635°F and is usable at temperatures up to 260°F. At lower temperatures it remains flexible well below freezing, as low as -100°F or even lower, depending on formulation. It’s also a good electrical insulator. Of particular relevance for food industry gasket applications, it doesn’t absorb water and it’s biologically inert. It does however resist attack by almost all chemicals, including aggressive cleaning and disinfecting agents like chlorine dioxide.

PTFE Seal Alternatives

Other materials have properties that are close or superior to PTFE in some regards. Silicone for example is flexible at low temperature, has good compressibility and a higher upper temperature limit. However, silicone does not fare well with steam, which is found in many food preparation environments. It also lacks resistance to acids, alkalies and chlorinated solvents, so is limited in its potential as a food grade gasket.

FDA Approved Seal Material

Gaskets & Seals made entirely of PTFE are covered by 21 CFR 177.1550, meaning they have FDA approval for food industry use. (PTFE incorporating filler material may not meet FDA requirements.) At Hennig we can supply PTFE sealss in thicknesses ranging from 0.015″ to 0.50″. Call or email for further information.

Food Grade Gaskets, PTFE Gaskets
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The Popularity of Garlock Gaskets

Aug 29, 2016

Everyone has favorites – favorite teams, favorite food, and some of our customers have a favorite gasket material manufacturer. At Hennig Gasket we want to give customers the gasketing solution that meets their needs, which is why we stock material from all the leading manufacturers.

“Leading” is key. We’re not going to sell you a material or product that will disappoint, so we’re particular who we deal with. The materials we stock and distribute come from established manufacturers with long track records and deep understanding of sealing and gasketing. One of those manufacturers, and certainly one of the best known, (customers ask for it by name,) is Garlock.  Hennig Gasket is a stocking distributor of all Garlock Gasket Material.

About Garlock

Part of EnPro Industries, who specialize in engineered industrial products, Garlock is in the business of sealing fluids and protecting pipelines. They manufacture around the world, including in the US, and their products are used in industries ranging from food and pharmaceuticals to petrochemicals.

Technology-Driven

Garlock prides itself on the quality of application engineering (AE) support provided, and backs that up with extensive testing and product development capabilities. They continually invest in their production facilities and use R&D to ensure a steady flow of new product innovations.

Non-Asbestos Sheet Gasket Material

We carry two lines of Garlock compressed gasket material: Blue-gard and the Garlock 9000 series. The Blue-gard sheet materials consist of aramid heat-resistant synthetic fibers, fillers, and an elastomeric binder. This can be SBR, NBR, EPDM or neoprene. The 9000 series materials are similar but replace the aramid with carbon fibers. The 9800, 9850 and 9900 all handle continuous maximum temperature of 650°F.

Why Garlock?

When replacing a gasket it’s usually a safe strategy to make the new gasket the same as the old. As Garlock gasket material is among the most widely used, it makes sense to stay with that, unless it wasn’t performing.

Global reach means Garlock gasket material is available around the world. That’s useful for multinational manufacturers wanting to standardize on their gaskets: they just have to ask for Garlock.

Garlock are undisputed experts in sealing technology and have AE facilities second-to-none. When a joint proves particularly difficult to seal they have experts who can usually find a solution.

You don’t stay in business a long time without being dependable, (and at Hennig we’ve 90 years experience to back that up!) Garlock has been around a long time too, and we believe that speaks to their reliability and customer focus.

If You Want Garlock Gasket Material …

… we’ve got it. We know Garlock is a favorite of many of our customers, and they make a quality product. That’s why we’re happy to offer Garlock gaskets and gasket materials.

Garlock Gaskets
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Eight Tips for Maximizing the Life of Boiler Seals

Aug 15, 2016

Taking a boiler out of service is both expensive and disruptive. It can leave a building without heat, hot water, or steam for days, meaning lost production and unhappy customers or tenants. That’s why it pays to schedule boiler maintenance some time out, preferably for shutdowns or holiday periods. Many facilities make this an annual event, so the manhole and handhole boiler gaskets as well as the seals used in pipe flanges need to last at least that long.

  1. Don’t assume any rubbery material will do the job. It won’t. Buy good quality boiler seals from a reputable supplier. (Look for those made from EPDM as they hold up well to steam.)
  2. Clean the surfaces to be sealed thoroughly. The new seal should contact only the metal surfaces, not scale, corrosion, or scraps of old seal. Take care to avoid scratching the metal surfaces though as that will create a leak path.
  3. Avoid using any adhesives, sealants or anti-seize compounds on the seal or flanges. These can lower friction and allow the seal to move as the joint is tightened.
  4. Center the seal in the flange. This ensures clamping loads are distributed evenly across the surface. Not doing so creates areas of high and low load that reduce gasket life and let leaks form.
  5. Minimize the surface area of the seal exposed to atmosphere. Hot air leads to oxidation of the seal material, quickly reducing it’s life. If necessary, add shields to protect against hot air.
  6. Don’t overtighten the joint. This accelerates the process of the material taking a compression set and will lead to premature failure.
  7. Excessive heat and pressure shorten seal life. Temperatures and pressure above 380°F and 180 Bar should be avoided.
  8. Never reuse old gaskets. The material will have taken a compression set.

It’s worth investing time and money in buying quality boiler seals and fitting them carefully. When the job’s done properly the seals should function as intended for at least twelve months. That reduces the chance of premature failure, which would almost certainly require an unplanned, and expensive, shutdown.

Boiler Gaskets
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What to Look for in Boiler Gasket Material

Jul 18, 2016

Gaskets are part of every boiler and steam or hot water system. They’re used around the many handholes and manholes provided for access and inspection, to prevent leaks in exhaust ducting, and wherever pipes are joined. If a boiler gasket fails the consequences are usually serious. Hot water, steam, or exhaust gas leaks are dangerous and reduced efficiency increases operating costs. That’s why safety experts recommend boiler gaskets be inspected regularly and replaced every year.

Boiler Basics

Every boiler consists of a burner or heating element and some form of heat exchanger. Water, often chemically treated to prevent corrosion, enters the heat exchanger and is heated to a target temperature. In a steam-producing boiler temperatures and pressures can exceed 380°F and 180PSI.

Exhaust gases go up a flue and steam or hot water enter the piping system. In steam systems the vapor condenses as it cools and the condensate returns to the boiler to be reused. Condensing boilers tend to produce a corrosive condensate, (actually carbonic acid,) in the exhaust stack.

Boiler Maintenance

Shutting down a boiler is expensive and disruptive, so it’s always better done as part of scheduled maintenance rather than in response to a leak. Most boilers benefit from an annual inspection and clean. Removing accumulated soot and scale improves efficiency and components should be checked for correct operation. As that involves opening handholes and manholes, it’s also a good opportunity to replace gaskets, even if they show no sign of leaks. (And never reuse a gasket as that could lead to an unplanned shutdown!)

Boiler Gasket Materials

On the fire side of the boiler gasketing is usually done with fiberglass rope or tape. This can handle temperatures of more than 1,000°F. Another option is graphite foil, often formed into a spiral wound gasket for sealing flanges.

On the water side the primary consideration is tolerance to steam. Secondary requirements are good tensile strength, (to resist the internal pressures,) and resistance to corrosive acids and water treatment chemicals. Heat and oxygen tend to oxidize many elastomeric gasket materials, and this should also be considered when selecting boiler gaskets.

All-in-all, the water side environment usually leads to EPDM gaskets. They have a wide temperature range, good compressibility, and the excellent steam resistance that’s needed.

Boiler Gasket Selection

Downtime is expensive, so it’s important to ensure the new gaskets will provide at least 12 months of trouble-free service. Boiler gaskets should be selected based first on performance and secondly, on ease of installation and replacement. A well-made gasket will fit comfortably, providing good coverage of the mating surfaces. Contact a Hennig specialist today to ask what’s recommended for your boiler.

Boiler Gaskets
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Understanding EPDM Gasket Material

Jul 04, 2016

When buying elastomeric material to seal a joint many people go straight for neoprene gaskets. Neoprene works well in many applications, but there are cases where other materials will perform better. One such material that should be considered for outdoor use, or situations where abrasive wear is possible, is EPDM.

EPDM is rubber-like in appearance and properties, so good compressibility and recovery is a hallmark of EPDM gasket material. Like all gasket materials though, it has strengths and weaknesses. This overview should help prospective buyers decide whether to consider EPDM gaskets.

Chemistry and properties

EPDM is an acronym for ethylene-propylene diene monomer. Ethylene and propylene are hydrocarbons and gases at room temperature, yet combine to make solid polymers like polyethylene and polypropylene. By adjusting the proportions and controlling the polymerization process it’s possible to create long molecular chains with more rubbery properties. That’s EPDM.

Sometimes referred to just as EPM, EPDM is a very stable material that resists heat, oxidation, and the aging effects of ultraviolet light. Unlike many other elastomers it’s flexible at low temperatures, and depending on how it’s formulated, works over a range of -60°F to 300°F.

EPDM has good mechanical properties too. Tensile strength is in the range of 7 to 21 Mpa, which is higher than other elastomers like silicone (5 – 10 MPa), nitrile (12 – 15 MPa) and neoprene (5 – 8 MPa). It’s also resistant to abrasive wear, which can’t be said for silicone.

In terms of chemical resistance, EPDM holds up well to acids and alkalies and is a good choice when dealing with both brake fluids and ketones. It also has good resistance to steam. Where it fares less well is against hydrocarbon oils and petroleum products as these produce swelling.

EPDM gasket applications

Relatively immune to sunlight, water and low temperatures, EPDM is often a smart choice for gaskets that will be outside. Good compression set resistance means it recovers well in applications where a joint may open up from time to time, and high electrical resistance means EPDM gaskets may be appropriate for some electrical installations.

A silicone competitor

In the gasket world silicone is known as a high performance material with a wide temperature range and good flexibility. In many applications though, an EPDM gasket could be a more cost-effective choice. Its temperature range is almost as wide and it’s a stronger, more durable material.

Consult the materials specialists

EPDM is available in a wide range of formulations with properties that vary considerably. To get a better understanding of EPDM gasket material options for your application a discussion with the specialists at Hennig Gasket & Seals Inc. is recommended.  Contact us today.

EPDM Gaskets
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Non-Stick Graphite Gaskets Reduce Downtime

Jun 20, 2016

Study our website and you’ll see gaskets can be made from a wide range of materials. One of the most versatile yet under-appreciated of these is graphite. Graphite gasket temperature range handles temperatures from -400°F to +875°F, provide excellent dimensional stability and resist chemical attack. On top of that, they have an additional advantage that’s not obvious: they don’t stick to flanges.

The Cost of Flange Cleaning

When replacing a gasket it’s essential to clean flanges thoroughly. Many gasket materials stick to these flanges and have to be scraped off. That’s a problem, for two reasons. First, there’s a risk of scratching the faces while scraping, and that can create leak paths. Second, doing the job properly, (and avoiding early replacement,) takes time.

As explored in “Focus on the Cost of Sealing,” (December 2015,) gasket replacement almost always means taking equipment, or even an entire plant, offline. Each application is different, but the cost of downtime usually dwarfs the price of even the most expensive gasket. The less time that’s needed to swap out the old gasket for the new one, the faster the plant gets back into production, so anything that reduces down time is worth considering.

Just Carbon

Graphite is one form of carbon. That’s the same element that forms diamonds. It’s strong, inert and resists temperature and pressure extremes, but what makes graphite special is its slipperiness. In graphite the carbon atoms are formed into layers that can slide over one another. That helps when closing up a gasketed joint because the material moves easily to fill uneven gaps and take up flange deformation or surface imperfections.

Graphite Gasket Materials

Here at Hennig Gasket we carry graphite material in a range of sheet thicknesses and widths as well as flexible homogenous graphite rolls. These can be cut to practically any desired shape and provide excellent sealing in many different applications. For especially challenging applications ask about the graphite-sided kammprofile gasket. Whichever graphite gasket you choose though, you can be sure of one thing; you won’t waste time scraping old material off the flanges!

Graphite Gaskets
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Buna-N (Nitrile) Gaskets and Oil

Jun 06, 2016

When working with a gearbox, a pump, or part of a fuel system, it’s essential to select a gasket material with resistance to hydrocarbons. Mineral and vegetable oils, along with diesel, gasoline and similar fuels, attack many materials, causing them to swell or break down. The notable exception is nitrile rubber. Nitrile rubber gaskets, often referred to as Buna-N or NBR gaskets, offer excellent resistance to oil.

Nitrile Rubber Chemistry

Nitrile rubber is made from a blend of acrylonitrile (chemical formula C3H3N) and butadiene (C4H6.) Each component is mixed with water as an emulsion before being combined in a polymerization reaction. This makes the carbon (C) and hydrogen (H) atoms form into long chains that tangle round another to form a rubbery compound.

Increasing the proportion of acrylonitrile makes the rubber stronger and reduces its gas permeability. The trade-off is that it results in a rubber that’s stiffer at low temperatures.

Rubber and Swelling

Most rubber absorbs oil and swells up in size. This is a problem in gaskets used in gearboxes and engines because it can lead to leaks. However, acrylonitrile reduces this tendency. So the greater the proportion of acrylonitrile used in the nitrile rubber formulation the less it will swell.

Swelling is covered in the ASTM D2000 specification. Most nitrile gasket materials are classed as ‘BF,’ ‘BG’ or ‘BK.’ The ‘B’ indicates an upper temperature limit of 100°C and the second letter shows how much the rubber will swell. ‘F’ is swell of 60% by volume, (under specified conditions,) while ‘G’ is 40% and ‘K’ 10%.

When and When Not to use Nitrile Gaskets

Good applications are those where peak temperatures are moderate and there’s exposure to oils. However, nitrile rubber does not hold up well to ozone and oxygen, so should not be used in places where these are present. Water purification equipment is one such location.

The Application Dictates the Gasket Material

If there’s any question about the properties of various gasket materials, consult the specialists at Hennig Gasket. They can explain the material choices available for your application.

Buna N, Nitrile Gaskets
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How Flanges Influence Gasket Material Selection

May 23, 2016

If flange and enclosure door surfaces were perfectly smooth and perfectly aligned, gaskets wouldn’t be needed. In the real world though, uneven gaps are always present and must be sealed to prevent leaks or contamination. Sealing options range from inexpensive red rubber and buna N materials to advanced silicone rubber gaskets, and include materials as diverse as graphite, PTFE and paper.

When replacing gaskets it’s common to use the same material that’s just been removed. If joints never change, that approach is often adequate. But by considering the nature and design of the sealing surfaces or flanges, it may be possible to select a longer-lasting material.

Impact of flange material

Some flanges can’t take high clamping forces, especially as they age. Plastics tend to become brittle and some metals lose ductility as they age, particularly if put through repeated temperature cycles. This means a soft, easily compressed gasket material is needed.

Impact of flange geometry

Bolt patterns or the position of clamps and latches can distort the mating surfaces, leading to uneven gaps. For example, an enclosure door with a single central latch can leave large gaps at the corners when closed. Also, a flange that’s been assembled and dissembled repeatedly for many years will start to distort, creating uneven gaps.

Flange alignment can change over time. After years of service it’s possible that piping will have moved, with the result that flange faces are no longer parallel. Again, the result is an uneven gap. Another problem is surface imperfections resulting from careless gasket removal.

These problems demand thicker gasket material that provides more compression. But thicker material needs higher loads to compress down in the joint, and those loads can lead to more distortion in the flanges.

Things change

Flanges and mating surfaces change over time and products that performed well, perhaps red rubber or buna N gaskets, may no longer be up to the job. When replacing gaskets, consider the condition of the sealing surfaces or flanges. A different material may last longer in the joint.

 

FAQs, Flange Gaskets
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