2 Main Factors that Influence the Sealing Potential of a Spiral Wound Gasket

Spiral wound gaskets, from their inception in the early 20th century, have become a main stay in the fluid sealing industry.  Off the shelf spiral wound gaskets are built to fit standard ASME B 16.5 flanges and applications. And are used extensively in standard pressure class rated flanges.

In what I think is an important spiral wound gasket study (PVP2013-97036) documented and presented for the ASME 2013 Pressure Vessel and Piping Division Conference, a number of factors were discussed pertaining to the influences that enhance a spiral wound gaskets sealing potential. While I do not go into all of the details from this study for this blog post, I do cover 2 of the essential findings.  Clicking on the link will take you to the full report.

Your typical spiral wound gasket consists of the following main components:

  1. An outer guide ring that helps center the gasket properly between the flange bolts.
  2. Windings that make up the sealing element which by design, combine the best of two technologies.
    1. First, metallic windings designed in a “V” shape and act like a chevron ring, providing resiliency and mechanical strength.
    2. Second, a filler material.  Most often a flexible graphite filler is wound in between the metallic V shaped windings, adding excellent sealing capabilities as the graphite (or other filler material), flows and seals into the grooves of the flange faces.
  3. And lastly an inner ring which helps prevent the windings from inner buckling, thereby increasing the seal of the gasket and keeps the windings from extruding into the flange bore and possibly unwinding and causing equipment damage downstream of the gasket.

Typical Cross Section Diaphragm of a Standard Spiral Wound Gasket

2 Main Factors That Influence The Sealing Potential of Spiral Wound Gaskets

1.Winding Density

The metal strips are wound around a mandrel the size of the internal dimensions of the particular gasket being made.  Once the metal strips form the ID, the filler material is placed in between the metal windings and wrapped together under pressure. The more windings per inch of sealing surface,the higher density of the sealing area the better the seal.  This factor has a greater influence on the sealing ability of the gasket then anything else. This should be taken into account when choosing a spiral wound gasket to use.

2.Filler Protrusion

Filler material that protrudes above the metal windings (0.008 in) of a spiral wound gasket enhances the seal of the gasket. The filler material comes in contact with the flange face, flowing into the grooves machined into the sealing surface. Filler material that is flush with the metal windings exhibit higher leakage rates. By simply taking a close look at the windings of a spiral wound gasket, one can see if the filler material is flush with the metal windings or completely covers the metal windings.

Beyond winding density and filler protrusion, additional influences that enhance a spiral wound gasket to seal better are:

  1. An inner ring which prevents radial flow of the windings thereby creating a “tighter” seal. And prevents the winding from inner buckling and coming unwound and causing equipment damage.
  2. The integrity of the flange finish.  Flange faces that are free of nicks and scratches and are parallel to each other and have a recommended 125-250 rms finish, provide the best sealing surfaces.
  3. No radial grooves, nicks or scratches.
  4. Proper compressive load applied on the gasket by using the proper torque values per flange classification. And by using a proper torque wrench when tightening the bolts.
  5. And by following the proper use of gasket installation best practices as outline by ASME PCC-1.

Spiral wound gaskets are dependable across a variety of applications. According to the need, different metals and fillers can be used in various combinations to meet just about any sealing application. For more information about a particular application you have, please don’t hesitate to contact one of our sealing professionals at Four States gasket and Rubber, Inc.

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5 Characteristics of Flexible Graphite

 

Graphite – A Little Background

Graphite was first discovered in Cumbria, North England at the beginning of the sixteenth century.

graphite

Natural Graphite Specimen

From it’s discovery – graphite has been useful. First it was used to mark sheepskins by shepherds wanting to distinctly “mark” their property .  Latter it was used in the moldings for cannon ball production.  Then it became popular as a material used by artists.

The first documented use of graphite as a pencil occurred in 1565. The use of graphite as an art material became popular, sold by Flemish merchants throughout Europe. At first, pencils consisted of rough pieces of graphite wrapped in sheepskin. The Italians first began using pencils that consisted of pieces of graphite embedded in wood. (University of Waterloo Earth Science Article)

Graphite is a mineral composed exclusively of carbon. Interestingly enough, graphite has the same chemical makeup as diamonds, which is also carbon, but the molecular structure of Graphite and Diamonds is entirely different. This causes opposite characteristics in their physical properties. And it’s in these differences that make flexible graphite a superior performing packing and gasket material.

Flexible graphite is the first fluid sealing material made exclusively from natural graphite flake. Graphite flake is exfoliated or expanded (by various methods either chemically or through rapidly heating the graphite flake) making it flexible and soft. Ideal for gasket material.

5 Characteristics of Flexible Graphite.

1.Flexible Graphite is a Natural Lubricant:

Graphite has a natural greasy, slippery characteristic that makes it a good lubricant.  For example, flexible graphite yarn is very popular for use in compression packing around pump shafts.  The lubrication it provides minimizes shaft wear and can be used on higher speed rotating equipment.

2.Flexible Graphite is Heat Resistance:

Graphite has three notable thermal properties that make it unique.  First, graphite has a high melting point.  Which makes it a good gasket material in higher temps (continuous service up to 700F in inert atmospheres) Second, graphite has remarkable heat transfer properties, dissipating heat away from critical, heat sensitive components.  And Third, graphite has low thermal expansion.  In heated environments, graphite doesn’t expand all that much relative to other materials.

3.Flexible Graphite is Chemically Resistance:

Graphite is insoluble.  It cannot be dissolved in a liquid, especially water. And graphite is infusible.  Making it one of the most chemically resistance gasket materials.  However at operating temperatures at or above 842 degress F, it is advisable to contact your local provider for additional information.  Graphite chemical resistant charts are available upon request.

4.Flexible Graphite Has the ability to Compress and Conform: 

Because flexible graphite can be compressed it conforms to flange surfaces and “flows” into irregularities in flange faces under a wide range of compressive loads.  Once in place, flexible graphite’s low creep relaxation characteristics maintains stability, enhancing sealability.

5.Flexible Graphite Can Oxidized Under Certain Conditions

One of the more typical concerns when using flexible graphite is thermal oxidation. Thermal oxidation is a function of time and temperature.  The longer flexible graphite is at high temperatures (850F and above) where oxygen is present within the process fluid oxidation (the breakdown of the graphite to carbon monoxide and carbon dioxide) occurs. This conversion creates microscopic voids and weight loss in the material, which can reduce compressive load on the gasket and begin to leak.  Other factors to consider:

  • Oxidation of a flexible graphite gasket occurs most often at the edges of the gasket.  Where the gasket comes into contact with an oxidizing environment.
  • Oxidation of a flexible graphite gasket can be reduce by adding a oxidation inhibitor such as a phosphate. Your typical flexible graphite material already comes with an oxidation inhibitor added.
  • Oxidation of a flexible graphite gasket can be reduce by ensuring the gasket is properly crushed as the then denser material is less permeable.
  • Oxidation of a flexible graphite gasket can be reduced with a change in the design of the gasket. Such as including a high temp barrier material.

Flexible Graphite Gasket Applications

Over the years we’ve seen flexible graphite gaskets, and compression packing, used effectively in many industrial applications with great success.  Here’s a few application examples:

  • Compressor engine exhaust stack piping flanges.
  • Fire tube gaskets on separators and dehydrators.
  • As a filler material in spiral wound gaskets.  Widely used in standard piping flanges.
  • As a facing material on double jacketed, camprofile or corragated gaskets for industrial processing vessels.
  • Pump and valve compression packing.
  • Oval manway tank gaskets that are normally hard to seal due to uneven flange surface finish and irregularities.
  • Flanges that have irregularities where other materials cannot flow and fill those imperfections.
  • Some styles of flexible graphite have a stainless steel substrate that improves the mechanical strength and rigidity of the material.

If you have questions or need assistant with a gasket application, please feel free to contact any of our personnel here at Four States Gasket and Rubber.

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Leading Through Uncertain times

It’s no joke.  We are living through some of the most uncertain and unsettling times many of us have ever experienced.  And it’s also no joke that the burden for leaders to, well lead, is needed now as much as ever.  To be able to stay focused on what’s important, remain calm, take appropriate action and help others do the same is critical to the long term success of the organizations, departments or the work teams we are a part of.

In renowned leadership expert John Maxwell’s blog post Leading Through Frightening Times , he provides practical and common sense guidance on how best to lead through the times we find ourselves in.

Here’s a brief Summary of Maxwell’s main points.

  1. Be a visible presence.  Your presence, physically, mentally and emotionally can do a lot to curb the fear and uncertainty that your team may be experiencing.  Don’t hide away behind closed doors.  That does nothing to foster the confidence camaraderie your people need.
  2. Acknowledge the fear, but don’t empower it.  Our job as leaders is to define reality.  However, stick to the facts.  Don’t over blow the situation.  We’re all getting enough of that from everyday media.
  3. Paint a brighter picture. Be forward thinking.  All things will pass.  Point towards the future and how things will be better and how we all we be stronger as a result of our present trial and challenges.
  4. Be cautious with predictions, but generous with hope.  As you point to the future, remember, you can’t predict with 100% certainty what will happen.  But you can think of others first and help them through to a better future.  Be thankful for each day, praise the good work of others, be generous with your interactions. Hope is the fuel that helps people move foward.

When fear and uncertainty seem to rule the everyday messages we all are constantly bombarded with.  Maxwell offers a dose of sanity for those of us responsible for keeping things together, getting the job done and moving forward in the most productive, safe and thriving way possible.

Stay safe, do all you can to stay healthy and move forward with a clear, accurate and hopeful attitude.  What you say and do matters.  Faithfulness to your duty will reap rewards that lesser leaders will never know.  This too shall pass.  Keep the faith.

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Four States Gasket COVID-19 Update

Dear Valued Customer.
We at Four States Gasket & Rubber want to let all our customers know that we are taking all government and local precautions regarding the COVID-19 virus. Keeping our employees, customers and communities safe and healthy is a top priority at all times, and even more so during times like these.
We are very thankful to say at this time all employees are healthy and we are operating at full capacity at both Farmington, NM and Brighton, CO facilities. Both facilities are open normal business hours 7am to 5pm and can fully serve the gasket and sealing of all customers. We are also working closely with our manufactures daily to avoid any delays or shipping problems that may arise during this time. As updates affecting our day to day operations, or any delay that may cause problems supplying product arise, we will keep all customers posted as soon as possible.
Four States Gasket & Rubber thanks all our loyal customers and we want to let you know we are here and can take care of any needs you may have. Contacts for both offices are below if you have any questions, need to request a quote, or order placement.
Farmington, NM-  (505) 325-9806
Brighton, CO- (303) 655-8315
Please contact paula@fourstatesgasket.com with any AR/AP needs you may have for both locations
Thank you for your continued support and please stay healthy
 Scott Blades
Owner / General manager

 

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I Need a Round Gasket with Holes In It?

Like any service oriented business, fluid sealing companies, which include your local gasket shops, work hard to provide great customer service, professional fluid sealing advice and “right-now” gasket fabrication. Taken as a whole service package, this is one of the top advantages of having a great working relationship with your local gasket shop.

The variety of fluid sealing problems that customers bring into a gasket shop cover a wide range of gasket materials, shapes, sizes and applications. On a regular basis a customer will walk in and ask if we can make them a gasket for a piece of equipment immediately. When asked about the dimensions or for more information on the gasket they need they’ll say something like, “you know,” “it is a round gasket with holes in it.” Since there are many gaskets that are round with holes in them, that description doesn’t help. Everyone ends up frustrated.

If you ever find yourself in a situation where you need a gasket made, before you walk into your local gasket shop it helps if you have the information needed to fabricate or select the right gasket for you. A simple way to gather the info needed is to follow The S.T.A.M.P. method.

The S.T.A.M.P. Method

S. – Size. What are the physical dimensions of the gasket you require. If the gasket is an odd shape, bringing in a sample is helpful. In addition, knowing what thickness of! material you need would help too.

T. – Temperature. What is the minimum and maximum temperatures the gasket will have to withstand.

A. – Application. What type of equipment will the gasket go on. I.E., pumps, valves, mixers, vessels, engines, dehydrators, etc.

M. – Media What are you trying seal? If you guess at this one your gasket provider will be guessing as to what will work for you.

P. – Pressure. What is the operating pressure you expect the gasket to hold up to?

S. – Speed. This applies to rotating equipment. What is the shaft speed in fpm?

If you have the answers to the above applicable questions for your needs, your gasket provider has everything they’ll need to supply you with the right gasket for the job.

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