How to Prevent Gasket Blow-Outs in Flanged Piping Connections.

flangedConnectionThis blog post was adopted from Jim Drago, PE, Senior Manager, Marketing Intelligence, Garlock Sealing Technologies, Palmyra, New York, USA article entitled “Initial gasket compression is key to safe, reliable flange joints”

A question that we are often asked is “what pressure rating is the gasket material I need good for?”  Obviously, the concern is for the gaskets ability to maintain a good seal and not “blow-out”  According to Jim Drago the answer to that questions depends on a number of variables.

Blow-out resistance is not primarily a function of gasket tensile strength, but rather a number of other factors, including clamping force, flange surface texture, temperature, gasket creep resistance, joint rigidity and internal pressure.

1) The clamping force of the bolts transferred through the flanges produces compressive stress (force per unit area) on the surface of the gasket. Different types of gaskets require different minimum compressive stresses in order to effect and maintain a seal.

2) Surface-finish determines how effectively flanges grip a gasket. It is especially important to bear this in mind when dealing with soft, sheet-type gaskets. A serrated flange surface, as specified by ASME B16.5 section 6.4.5.3 will “bite” into a gasket – holding it in place and preventing it from splitting and shearing as it would with a
smooth flange.

3) Temperature and gasket creep are directly related. When the temperature increases, flange bolts relax as their yield strength decreases. Gasket materials become thinner without an increase in compressive load. Bolt relaxation and gasket creep effectively reduce the clamping force on a gasket, increasing the probability of a leak.

4) Flange rigidity affects how bolt load will be transferred to a gasket.

5) Internal system pressure develops forces within a joint that concurrently work to pull apart the flanges and push out the gasket.

Finally, In the case of soft-sheet gaskets, compressive stress and not the tensile strength of the material is the major determinant of flanged joint reliability. Therefore, gasket installation demands the utmost diligence. The use of torque wrenches and following gasket manufacturers’ guidelines will go a long way to assuring reliable joints for improved worker safety and plant productivity.

To read the full article, including testing data, go to

http://www.garlock.com/en/technical-information/technical-articles/

Posted in Industry Standards, Technical Info | Leave a comment

High Temperature Textiles

High temperature textiles fiberglass tapes provide a safe, durable and effective thermal barrier for a wide variety of applications in the manufacture of metals, petroleum, chemicals, glass, paper and wherever flames and extreme heat can be a danger. Key industries where textiles are used include:

+ Refinning

+ Power Generation

+ Mining/Metals

+ Natural Gas Processing Plants

fiberglass-tape-250x250

AMI-GLAS TAPE

STYLE #GL08

(PLAIN OR 9383 HEAT CLEANED)

TYPE: PLAIN OR BOLT HOLE
NOMINAL THICKNESS: 0.125″ (BOLT HOLE TAPE MAY MEASURE DIFFERENTLY)
STANDARD PUT UP: 100FT/RL
STANDARD NOMINAL WIDTHS: .5″, .625″, .75″, 1″, 1.5″, 2″, 2.5″, 3″, 4″, 5″, 6″, 7″
TEMPERATURE RESISTANCE: 1000˚F
STANDARD COLOR: WHITE, OTHER COLORS AVAILABLE PLEASE CALL FOR DETAILS
CONTENT: 100 % FIBERGLASS YARNS

WEAVE: PLAIN
AVAILABLE WITH A HIGH PERFORMANCE PRESSURE SENSITIVE ADHESIVE
• ADHESIVE TEMPERATURE RESISTANCE: 300˚F
• ADHESIVE IS ONLY USED TO AID THE INSTALLATION PROCESS, AFTER THE MATERIAL IS IN PLACE, IT IS USUALLY MECHANICALLY BONDED SO THAT THE ADHESIVE IS NO LONGER NECESSARY.

ALL UNCOATED FIBERGLASS TAPES ARE NONCOMBUSTIBLE MEETING USCG 164.009
OTHER: MATERIAL SHOULD BE TESTED FOR ITS SUITABILITY IN ANY APPLICATION.

USERS SHOULD ALSO FAMILIARIZE THEMSELVES WITH THE MSDS BEFORE
HANDLING.

For more information contact Four States Gasket:

In Brighton CO – 303-655-8315

In Farmington NM – 505-325-9806

Posted in Uncategorized | Leave a comment

O-RING BASICS

DefinitionOring_Geometry

An O-ring is a doughnut-shaped object or torus.
The opposite sides of an O-ring are squeezed between
the walls of the cavity or “gland” into which the O-ring
is installed. The resulting zero clearance within the
gland provides an effective seal, blocking the flow of  liquids or gases through the gland’s internal passage. An O-ring is defined by its dimensions (based on inside [hole] diameter and cross section), durometer
(Shore A hardness), and material composition.

Why an O-Ring Works

A properly designed sealing system incorporates some degree of initial O-ring compression. At atmospheric pressure, only the resiliency of the compressed O-ring provides the seal. However, as system pressure activates the seal, the O-ring is forced to the low pressure side of the sealing surface. Designed to deform, the O-ring “flows” to fill the diametrical clearance and blocks any further leakage.

Dimensional Considerations

Inside Diameter

To provide an effective seal, the O-ring’s inside diameter (I.D.) must be smaller than the piston groove diameter, so that the O-ring is slightly stretched, fitting snugly in the groove. This stretch should be between 1%-5% with 2% as the ideal in most applications. A stretch greater than 5% is not recommended. The resulting stress on the O-ring will cause accelerated aging and cross section reduction. Exception to this rule is a floating seal. These are O-rings that are allowed to sit in grooves freely or “float”. These are used in applications where some leakage is allowed and less friction is required.

Summary
For optimum sealing performance, correct O-ring selection is the direct result of a number of design considerations. These considerations include: size, squeeze, stretch, chemical compatibility, and the ability to resist pressure, temperature, and friction.  Your final selection will usually be a compromise in the sense that you have to balance all of these considerations.

The content for this portion of this post was adopted from an article entitled “O-Ring Basics”.

Types of O-Ring Elastomers

Nitrile (Buna-N)

The most widely used O-Ring elastomer. Excellent resistance to petroleum products. Excellent compression, set, tear and abrasion resistance. Does not have good resistance to ozone, sunlight, or weather (unless specifically compounded). Should not be stored in direct sunlight or near motors or other electrical equipment which may generate ozone.
Temperature range: – 40° to +250°F.

Fluoroelastomer [Viton® (E.I. duPont)]
Excellent mechanical and physical properties. Good resistance to petroleum products, low compression set, and high temperature resistance. Wide spectrum of chemical compatibility. Good for vacuum service and low gas permeability. APG stocks the Type “A” Grade Fluoroelastomer. Other grades are available ─ please inquire.

Chloroprene (Neoprene)

Moderately resistant to petroleum products. Good ozone and weather resistance. Good compression set. Excellent for sealing refrigeration fluids such as Freon®. Temperature range: -65° to +250°F.

Silicone
Recommended for applications requiring a wide temperature range and good dry heat resistance. Good weather and ozone resistance. Limited oil resistance. Not normally recommended for dynamic sealing applications due to relatively poor tensile and tear strength and relatively low abrasion resistance. Temperature range: -80° to +450°F.

Highly Saturated Nitrile (HSN, HNBR)
Better resistance to high temperatures, superior physical properties, and improved chemical resistance over traditional nitrile compounds. It also has better resistance to ozone, sunlight, and other atmospheric conditions. Excellent resistance to compression set. Green HSN is used in refrigerant R134a applications. Temperature range: -40° to +325°F.

Ethylene Propylene (EPR, EPDM, EPM)
Excellent resistance to Skydrol® fluids used in commercial aircraft hydraulic systems. Also recommended for hot water, steam, and phosphate ester type hydraulic fluids. Resistant to some acids, alkalies, and ozone. Not recommended for petroleum fluids or diester lubricants. Temperature range: -65° to +300°F.

Aflas® (Asahi Glass Co., Ltd.)
Advantageous combination of high temperature, chemical, and electrical resistance properties. Recommended for oils and lubricants, hydraulic and brake fluids, transmission and power steering fluids, sour oil and gas (H2S), amine corrosion inhibitors, ozone, steam, acids, bases, alcohols, and a variety of other chemicals. Temperature range: -25° to +450°F. (+500°F short term).

Posted in Uncategorized | Leave a comment

An Alternative to Conventional PTFE

expanded teflon gasketsTEADIT’S EXPANDED TEFLON

Quimflex SH gasket sheet is manufactured by expanding 100% virgin PTFE using a proprietary process that produces a uniform and highly fibrillated microstructure with equal tensile strength in all directions. The resulting product exhibits characteristics significantly different than conventional PTFE sheet. This style is much softer and more flexible than regular PTFE sheet and thus conforms easily to irregular and rough surfaces. In addition, the material is easier to compress and minimizes creep and cold flow.

TEADIT 24SH gasket material complies to FDA regulations for food contact and EU 1935/2004

APPLICATION / SERVICE

Quimflex SH is an all purpose gasket sheet that can replace all other types of PTFE sheet. It will seal all aggressive chemicals over the entire 0-14 pH range except for molten alkali metals and elemental fluorine. Made from 100% virgin PTFE, it not only resists chemical attack, but it will not contaminate or discolor end products.

For more information contact Four States Gasket and Rubber, Inc

Posted in Uncategorized | Leave a comment

Expansion Joints

Expansion Joints are another product line that we can help our customer with.  Proco is just one product line we distribute.  If you need more information on the other types and styles of expansion and flu duct joints we handle, give us a call.

Posted in Uncategorized | Leave a comment