Jjenco PerfectSeal Constant Seating Stress Gaskets A Revolutionary Approach To Improved Flange...


Copyright © JJENCO, Inc. 2009. All Rights Reserved. 2

Introduction

The PerfectSealEOS constant seating stress gasket:• Does not rely upon (i) highly-trained assembly technicians, (ii) properly calibrated

tooling, (iii) complex flange tightening patterns, (iv) time-consuming multiple flange tightening passes, or (v) correct piping alignment in order to achieve a ‘perfect seal’ every time

• Cannot be ‘misinstalled’, regardless of flange orientation• Is at least 7X faster to install than conventional gaskets, even on small 8-bolt

flanges• Is a direct replacement for all semi-metallic gaskets, including spiral-wound

gaskets (SWG) and kammprofile gaskets• Is immune to (i) radially-inward buckling (RIB), (ii) foreign material cast-off into

the process fluid, (iii) flow-induced gasket degradation, (iv) system vibration and (v) thermal transients

• Is the least expensive semi-metallic gasket solution when gasket installation costs are included

• Can be inexpensively refurbished and reused



Sealing IssuesConventional Gasket Products

Product Issues• Unknown or imprecise gasket factors• Compression Variability (SWG)• Wrong Gasket for Application• Spent After Single Use

Calculation Errors• Required Seating Stress• Required Fastener Preload• Friction Estimate (Nut or ‘K’ Factor)• Required Torque Value

Tooling Issues• Torque Wrench Accuracy• Calibration Errors• Off-Axial End Effectors• Incorrect Torque Wrench Setting

Assembly Issues• Incorrect Wrench Reading (Dial/Beam)• Improper Torquing Technique• Insufficient Fastener Lubricant• Improper Lubrication Placement• Poor Fastener Thread or Bearing Surface• Improper Tightening Sequence• Piping Misalignment• Uneven Gasket Loading• Insufficient ‘Finishing’ Passes

In-Service Issues• ‘Soft Joint’ Assembly >>CR• Plant Thermal Cycles >>CR• High System Vibration >>CR• Radially-Inward Buckling (SWG only)• Foreign Material Intrusion [to System]• External Blowout• Environmental Degradation (eg. Fire)• Process Degradation (eg. Oxidation)

SWG = Spiral Wound GasketCR = Creep Relaxation > Loss of Bolt Stress



Sealing SolutionsPerfectSealEOS Gaskets

Product Issues Unknown or imprecise gasket factors Compression Variability (SWG) Wrong Gasket for Application Spent After Single Use

Calculation Errors Required Seating Stress Required Fastener Preload Friction Estimate (Nut or ‘K’ Factor) Required Torque Value

Tooling Issues Torque Wrench Accuracy Calibration Errors Off-Axial End Effectors Incorrect Torque Wrench Setting

Assembly Issues Incorrect Wrench Reading (Dial/Beam) Improper Torquing Technique Insufficient Fastener Lubricant Improper Lubrication Placement Poor Fastener Thread or Bearing Surface Improper Tightening Sequence Piping Misalignment Uneven Gasket Loading Insufficient ‘Finishing’ Passes

In-Service Issues ‘Soft Joint’ Assembly >>CR Plant Thermal Cycles >>CR High System Vibration >>CR Radially-Inward Buckling (SWG only) Foreign Material Intrusion [to System] External Blowout Environmental Degradation (eg. Fire) Process Degradation (eg. Oxidation)

SWG = Spiral Wound GasketCR = Creep Relaxation > Loss of Bolt Stress



Presentation Overview

This self-paced technical tutorial is intended to:• Explain the revolutionary ‘constant seating stress gasket concept’• Illustrate the application of that concept to flange joint assembly• Showcase different styles of the PerfectSeal gasket for specific

applications• Present test data and field demonstration experience• Compare performance vs. conventional semi-metallic gaskets• Highlight the benefits of constant seating stress gaskets over

traditional gasket technologies in real-world applications• Demonstrate the cost-benefit of using PerfectSeal gaskets compared

to conventional gaskets This tutorial should take approximately 25 minutes to complete



UNDERSTANDING THE CONSTANT SEATING STRESS GASKET CONCEPT

SECTION I



What is a ‘Constant Seating Stress’ Gasket?

A constant seating stress gasket is defined by two common characteristics:• The initial seating stress of the sealing material achieved

on assembly does not change appreciably over time• The seating stress of the sealing material is relatively

uniform radially across the entire sealing area JJENCO holds the patent on constant seating stress

gasket technology Constant seating stress gaskets are only available

directly from JJENCO



Why is Constant Seating Stress Important?

Gasket leakage occurs primarily due to one of the following 6 reasons:• Flange sealing surfaces too defective to achieve a seal• Initial gasket seating stress too high• Initial gasket seating stress too low• Initial gasket seating stress sufficient to achieve a seal, but gasket creep

relaxation leads to loss of seating stress over time• System conditions (thermal cycles, high vibration, etc) cause transient or

permanent reduction in gasket stress enabling leakage to occur• Gasket sealing material not compatible with environmental or process

conditions Assuming the sealing surfaces are acceptable and the sealing elements

are compatible with the process fluid, PerfectSeal constant seating stress gaskets can mitigate all remaining factors



Simple Design Premise

The design premise for the PerfectSealEOS gasket recognizes that:• A specific amount of gasket seating stress is needed in order to

create an effective seal between two flange faces• Gasket stress tends to change over time, primarily due to the

gasket sealing material’s continued response [creep relaxation] to the external force used to create the initial seal, or due to other forces resulting from thermal cycling, vibration, etc

• If you can achieve the initial seating stress necessary to achieve a seal, and control other factors that can change that seating stress over time, then in-service leakage can be averted in most cases



Achieving Correct Gasket Stress

Flange deflection – also known as ‘flange rotation’ – occurs at the outer flange circumference in response to increasing preload of the fasteners during flange assembly

Finite element analysis (FEA) can accurately predict the degree of flange deflection that occurs at various radial distances from the flange axis at a given bolt preload for a specified flange size, material and pressure class.

Therefore, flange deflection can be used in lieu of applied bolt torque to accurately determine required gasket tightness

The PerfectSealEOS gasket profile models flange deflection predicted for a desired preload, making ALL assembly factors associated with achieving the target bolt preload unimportant



Maintaining the Correct Gasket Stress

Creep relaxation of the gasket sealing material is the main cause of loss of gasket seating stress in service

Gasket ‘creep’ occurs as the sealing material seeks to move from a region of higher stress to a region of lower stress, thereby causing an overall reduction in peak gasket stress

A leak may result if the peak gasket stress drops below the threshold necessary to maintain the seal between the flanges

By fully containing the sealing material within opposing channels on either side of the gasket carrier ring, creep cannot occur in service, thereby self-mitigating the opportunity for a leak to occur



GENERAL APPLICATION TO FLANGED JOINTS

SECTION II



PerfectSealEOS General Description

The PerfectSeal gasket is comprised of a carrier ring (20) and a sealing material elements (22)

The carrier ring has three important features:• Inner pivot point (30)• Inner compression stop (32)• Visual Compression Indicator (40)

The sealing elements can be any compressible material (e.g., expanded graphite, vermiculite, expanded polytetraflouroethylene, etc.) as appropriate to the application



On Assembly

As the fasteners (16) are tightened, the flange faces (10A, 10B) begin to compress the sealing elements (22) into their respective channels (24) of the carrier ring and ultimately contact the inner pivot point (38) of the carrier ring

Continued tightening of the flange fasteners causes normal flange rotation to occur, thereby further compressing the sealing elements into their respective channels

A proprietary process controls the compression of the sealing elements into their respective channels



At Full Compression

As the flange faces rotate* about the inner pivot point, they finally engage the inner compression stop (32)

The sealing elements are fully compressed, resulting in achievement of the desired gasket seating stress

The sealing elements are fully contained, therefore no change in gasket stress can occur in service

The sealing elements are also completely protected from both the internal process flow and external environmental factors

*flange rotation exaggerated for illustration



Achieving Uniform Stress

Due to flange rotation, gasket seating stress generally increases with the distance from the axial centerline of the flange

This results in the achievement of the target seating stress only at the outer edge of the sealing area – the actual gasket stress over the majority of the sealing area is less

By matching the angle of the gasket profile with the calculated degree of flange rotation for a given flange size, pressure class, and material, the desired seating stress can be achieved over the entire sealing area – not just at the gasket’s outer edge



The Visual Compression Indicator

By calculating the degree of flange rotation occurring at two points, • the outer compression stop (40) • and the inner compression stop (32), • the outer compression stop thickness can

be sized to provide a positive visual indication for the assembly technician that the flange faces have positively engaged the inner compression stop

• thus fully compressing and capturing the sealing elements in their grooves

This outer compression stop also makes the use of calibrated assembly tooling, complex bolt tightening patterns, and sequential finishing passes completely unnecessary, as overcompression of the gasket cannot occurr



Installation Benefits

Sealing element channel prevents ‘crushing’ or overcompression when inserting gasket, aligning flanges, or tightening fasteners

The outer compression stop enables one-pass at 100% tightness, rotationally-sequential, tightening of fasteners

1

2

45

7

6

8

3

Single Pass Tightening in Sequential Rotation

Regardless of Flange Size



APPLICATION CONSIDERATIONSSECTION III



PerfectSealEOS Style

Ideal for all raised and flat face flanges

Carrier ring extends outward of the bolt circle

Provides real-time proper compression indicator to the assembly technician

Prevents misinstallation or gasket misalignment from occurring, regardless of flange orientation

Unique bolt hole configuration improves ability to insert fasteners without perfect flange alignment



PerfectSealCRG Style

Ideal for specific flanges• Male-female • Tongue and groove

Eliminates flange fit and tolerance concerns

Sealing element protected from process flow degradation

Can be manufactured with or without exterior alignment ring



In-Service Performance

Impossible to:• Cast-off foreign material into plant systems or components

(e.g., no radially-inward buckling (RIB) as with spiral-wound gaskets)

• Inadvertently ‘crush’ the gasket due to overcompression• Leak due to plant thermal cycles or high system vibration• Degrade sealing elements due to process flow impingment• Impact sealing element performance by direct external

contact



Application Specifications

Carrier ring normally made from 304/316 stainless steel, but can be manufactured from any appropriate material according to client requirements

Standard bolt preload emulation is 45ksi, but can be manufactured to emulate bolt preloads from 10-100ksi, according to client requirements

JJENCO has FEA design data available for ASME B16.5 carbon and stainless steel flanges:• RFWN flanges in all pressure classes and sizes from 0.5”-24”• RFSW flanges in all pressure classes and sizes from 0.5”-2”• Other flange types or configurations available (additional design fee applies)

Sealing elements are normally expanded graphite, expanded PTFE, or vermiculite, but can be made from any compressible sheet material according to client requirements



PERFORMANCE DATASECTION IV



Creep Relaxation Comparison

PerfectSealEOS gasket (red) vs. all other semi-metallic gaskets, including:• Spiral-wound gaskets (SWG)• Kammprofile gaskets• Semi-metallic sheet gaskets

Demonstrated less than half the creep (>24hrs) of the best gasket on the market

Less creep = less chance of leakage in service



Comparison to ‘CG’ Style SWG

Industry testing proves that torque required to compress spiral-wound gaskets (SWG) can vary widely between gaskets

CG-style* SWG without inner ring can creep in-service, resulting in leakage

CG-style SWG are prone to radially-inward buckling (RIB) of their windings that can introduce foreign material into system causing damage to components and system operability concerns

Most concerning, not all RIB-degraded SWG in service result in an identifiable leak

Multiple catastrophic buckles with filler material completely washed out and winding material extending well into the flow path

One of several pieces of SWG metal winding material removed from tube bundle of steam generator during routine inspection

*The ‘CG’ designation is used here as a generic identifier for a SWG possessing an outer compression stop ring, but no inner stop ring, and should not be construed to represent any particular manufacturer



Comparison to ‘CGI’ Style SWG

‘CGI’-style* SWG can reduce creep relaxation

However, due to the inability of ‘CGI’-style gaskets to relieve stress by moving radially inward:• The same torque levels used for

‘CG’-style SWG can cause extreme radial loads in the gasket sufficient to seriously deform the gasket

• Or, cause general deformation and buckling of the inner ring itself*The ‘CGI’ designation is used here as a

generic identifier for a SWG possessing both an outer and inner compression stop ring and should not be construed to represent any particular manufacturer

Illustration of severe ‘CGI’-style gasket deformation

Evidence proving generalized inner ring buckling can occur



Comparison to Kammprofiles

Kammprofile gaskets represent ‘the best of the best’ among semi-metallic gaskets, with respect to creep resistance

However, as with SWG, all kammprofiles perform differently

Using identical test equipment and procedures, the PerfectSealEOS gasket (red) is proven to creep 60% less than the best available kammprofile gasket

In addition, research shows that kammprofile gaskets also vary in their ability to seal minor surface defects in flange face finish – making excellent sealing surfaces a prerequisite for success



Field Test Example

Demonstrated in 4”-Class 150 service water system flange at Duke Energy ‘Riverbend’ fossil station

Installed under blind flange by one technician in under 45-seconds using standard combination wrench

Inspected after 1-hour at system T/P with no leaks



COST BENEFIT CASESECTION V



Cost Benefit Considerations

‘Unit Cost’ basis is NOT a smart procurement strategy for parts performing a critical function

‘Cost of Ownership’ procurement strategy for critical parts takes into account:• Installation costs• Cost benefits of increased service reliability and availability• Future maintenance costs

‘Total Cost of Ownership’ also takes into account future avoided costs



Initial Cost-of-Ownership*

*4-in Class 150 gasket

COST COMPARISON ($USD)Conventional

GasketPerfectSeal

GasketUnit Cost (estimates) 10 75

Installation Labor (20 min avg.) 40 22 mechanics @ $60/hr each

Calibrated Tooling 12 05% of $250 torque wrench l ife before req'd rebuild

Tooling Calibration Labor 20 01/3 labor-hour

Fastener Lubricant (8oz.) 10 0

Hardened Steel Washers (8) 4 0

TOTAL 96.00$ 77.00$

Radiation Dose (Nuclear Only) 30 1.50Estimate 0.1mR dose received x 2 persons @ $15K/man-rem

TOTAL w/ Dose Factor 126.00$ 78.50$



Subsequent Reinstallation Cost*

*4-in Class 150 gasket

COST COMPARISON ($USD)Conventional

GasketPerfectSeal

GasketUnit Cost (estimates) 10 10

(PerfectSeal sealing elements replaced only)

Installation Labor (20 min avg.) 40 22 mechanics @ $60/hr each

Calibrated Tooling 12 05% of $250 torque wrench l ife before req'd rebuild

Tooling Calibration Labor 20 01/3 labor-hour

Fastener Lubricant (8oz.) 10 0

Hardened Steel Washers (8) 4 0

TOTAL 96.00$ 12.00$

Radiation Dose (Nuclear Only) 30 1.50Estimate 0.1mR dose received x 2 persons @ $15K/man-rem

TOTAL w/ Dose Factor 126.00$ 13.50$



Potential Avoided Costs

Production Penalties • Forced plant outage, outage extension, production reduction

Replacement Production • e.g., replacement power

Maintenance Effort Radiation Exposure (nuclear only)

Third-Party Services • Leak sealant injections, environmental cleanup, flange remachining,

etc. Consequential System or Component Damage Regulatory Fines Response to Regulatory Scrutiny



CONCLUSIONSECTION VI



Direct Benefits

Simpler Tooling – No need to rely upon torque wrenches, stud tensioners, or other calibrated tooling

Simplicity of Installation– No complicated assembly patterns, multiple tightening passes

Speed of Assembly – Proven at least 7X faster to install on even small 8-bolt flanges

Reduced Training – Technicians require limited training to assemble flanged joints successfully

Increased protection from environmental- (e.g., fire, etc.) and process-induced degradation

No Possible Foreign Material introduction to system Reusable Carrier Ring dramatically reduces future replacement costs Increased Personnel Safety during installation and in-service Potential to Reduce Personnel Radiation Exposure (nuclear)



Indirect Benefits

Simplified job planning Reduced risk of

• Future maintenance requirements• Collateral or consequential equipment damage• Production losses attributable to leakage events• Replacement power acquisition (power industry)

Potential for reduction in insurance costs Reduced gasket inventory Reduced maintenance administrative burden Increased availability of plant staff Reduced potential for regulatory scrutiny due to leaks



Conclusion

The constant seating stress gasket design: • Uses commonly accepted materials• Is based upon simple, proven principles aggregated in a novel manner

It should be easy to install and require no follow-on maintenance

It is the least expensive gasket solution when gasket installation costs are included

It provides both immediate and future benefits in terms of• Personnel safety• Plant availability and reliability• Total cost of ownership



Maintenance Self-Assessment

Do you have gasket leaks at your site? If so, is your Maintenance department using

PerfectSeal constant seating stress gaskets? If not, Why Not?



For More Information…

To obtain:• Information on purchasing

PerfectSeal constant seating stress gaskets, or

• Subject-matter expertise for fluid sealing issues…

John M. JencoPresident

Research, Technology & ConsultingUniversity Research Park | Prosperity Place on Mallard Creek10130 Mallard Creek Road | Suite 300 | Charlotte | 28262 | USA(T) +1.704.944.5568 | (F) +1.704.944.3101 | [email protected]

Jjenco PerfectSeal Constant Seating Stress Gaskets A Revolutionary Approach To Improved Flange...

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Transcript of Jjenco PerfectSeal Constant Seating Stress Gaskets A Revolutionary Approach To Improved Flange...