engineered ferrules for high temperature waste heat boilers from blasch precision ceramics

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Engineered Ferrules for High Temperature Waste Heat Boilers


• Ferrule Systems• Round Ferrules• Hex Ferrules• Hex Ferrule Design• Hex Ferrule Experience

Engineered Products


• Round Ferrules• Hex Ferrules• Hex Ferrule Design• Hex Ferrule Experience

• Basic Design• Disadvantages• Can Performance Be

Improved?

Ferrule Systems


For many decades simple round ferrules embedded in a monolithic refractory have been the standard for high temperature waste heat boiler tubesheet protection.


Improved?

Round Ferrules


Reliability of a round ferrule installation is strongly influenced by:

• Selection of refractory • Type of anchors used • Skill of the installers• Care of the cure out• Operating temperature and cycling


Improved?

Any deviation from the optimal in any of the elements shown to the left can result in cracking, sometimes even catastrophic failure, even before introduction of acid gas

Round Ferrules


If concrete requires expansion joints to survive 100 deg C temperature swings over periods of many months, how can one expect refractory to survive 1,700 deg C swings in days without them? That is why sidewalks have expansion joints

every meter.


Improved?

Round Ferrules



• Overview• Advantages• Installation

Ferrule Systems



– Ferrules are specifically designed to fit each application’s tubesheet and unique set of operating conditions.

– Have been successfully used in waste heat boilers with tube diameters from 20mm to 200mm.

– Particularly compatible with systems that use oxygen enrichment and those with very large tubesheets.

– Available in a range of alumina compositions to suit, up to 99.6%

Hex Ferrules


• Overview• Advantages• Installation • Available with a range of design

options to address different tubesheet situations.

– 1-Piece. The one-piece hex ferrule design, now more than a decade old, has been used in hundreds of successful installations in a wide variety of chemical applications worldwide.

Hex Ferrules



• Available with a range of design options to address different tubesheet situations.

– ProLok 2-Piece. Produced with Blasch’s patented Engineered Expansion Joint Design. Segmenting the ferrule increases the available expansion management capacity while maintaining the unique Blasch fiber seal mechanism. ProLok interlocking system prevents stems from walking out under the most severe vibration

Hex Ferrules


• No castable is required between the ferrules. During installation, some castable would be needed around the perimeter of the ferrules, but the amount needed would be quite small in comparison to a conventional installation. This system can typically be installed in about one third of the time it would take to do a conventional installation. Additionally, refractory cure times can often be reduced during startup.

Hex Ferrules• Overview• Advantages• Installation


• Replacement costs are quite low. If the plant owner wishes to inspect the tubesheet, they would typically need to remove the ferrules. For a conventional installation this is a time consuming and costly activity because the castable must be removed and the ferrules cannot be reused. For Blasch precast ferrules, such activities are much simpler; typically only 10% of the ferrules need to be replaced, which substantially reduces maintenance costs and downtime.


Hex Ferrules


• Ferrules tend to have a lower pressure drop than conventional ferrules, which can either lead to improvements in waste heat boiler thru-put or lower plant energy consumption.


Hex Ferrules


– Ferrules are supplied complete with all necessary refractory fiber wraps and gaskets.

– Installation involves simply sliding each ferrule into the tube sheet.

– Installation is typically completed from the bottom of the tubesheet to the top.

– The assembly is finished with a castable or plastic refractory periphery.

– No metal anchors are required. Ferrules are held in place through friction with the boiler tube ID’s coupled with the peripheral refractory.

Hex Ferrules• Overview• Advantages• Installation



• Basic Refractory Design• Ferrule Design Philosophy• Ferrule Design Features

Hex Ferrule Design



• Refractory is not a metal– It does not act the same way under high

temperature conditions.– It is not characterized to the degree that

metals are.– All 95% Aluminas are not created

equally.

• Design guidelines– Never design with interior sharp angles.

Anything that looks like an interior corner will amplify stress and act as an origination site for cracking.

– Whenever possible, design to avoid placing refractory in tension. Thermal gradients can place refractory in tension.

– Never interfere with the need for refractory to expand and contract

– Design so as to work with thermal cycling, not against it.

Basic Refractory Design


• Blasch hex ferrules should never be mortared together, or kept from acting independently in any way.

• This is particularly critical in very large tubesheets, where enormous stresses can develop.

• Any given hex ferrule is impacted only by a maximum of six neighboring ferrules.


Ferrule Design Philosophy


Mortaring ferrules together creates the same sort of situation as in a cast

monolithic tubesheet

And yields similar results after a number of thermal cycles

Ferrule Design Philosophy



• Generous Radius Under the Head

• Recessed Groove Around the Head

• Aggressively Profiled Inlet• Required Operating

Parameters

Ferrule Design Features


• Generous Radius Under the Head• Recessed Groove Around the Head• Aggressively Profiled Inlet• Required Operating Parameters

• Minimizes stress concentration between head and stem.

• Proven very reliable.

Please Note large recess filled with insulating fiber



• Maintains space for the ceramic fiber wrap around the head.

• Allows for a tight hot face seal at operating temperature.

Recessed groove with high alumina fiber installed



ExpansionJoint


• Significantly reduces pressure drop across the ferrule as compared to straight and chamfered bore ferrules.




• Tube OD• Tube material, wall thickness and

applicable tolerances• Pitch (distance and angle

between center of tubes)• Tubesheet tube center

tolerances – both tube to tube and cumulative

• Normal operating temperature and any likely spikes

• Any unusual gas components, or specific temperature profile requirements

• Specifics of tube to tubesheet weld for clearances

• Tubesheet Thickness

Ferrule Design Features• Generous Radius Under the Head• Recessed Groove Around the Head• Aggressively Profiled Inlet• Required Operating Parameters



• Operating Experience• Partial List of Users

Hex Ferrule Experience


• First installation commissioned more than 20 years ago

• Nearly 250 successful installations

• Many operating near or over 3,000F (1,650C) on oxygen enrichment

Hex Ferrule Experience

• Operational Experience• Partial list of users

engineered ferrules for high temperature waste heat boilers from blasch precision ceramics

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