MST Offset Analysis of Bauer High-Pressure Rotary Feeder Valve

MST Corporation White Paper Study—Offset Analysis of Bauer High-Pressure Rotary Feeder Valve (HPRFV): Rotor Offset v Bore Profile v Alternatives v CenterSeal™ © Page 1 of 13 1659 SW Baldwin Road Prineville, OR 97754 (541) 416-9000 www.mstcorp.com

1. WHY A ROTOR OFFSET WAS, OR IS, USED ON A BAUER HIGH-PRESSURE ROTARY FEEDER VALVE (HPRFV)?

2. WHAT IS THE TRUE REASON AN OFFSET ROTOR EVOLVED AS GENERAL PRACTICE 3. A HISTORICAL PERSPECTIVE 4. THE PHYSICS INVOLVED 5. BETTER ALTERNATIVES OR METHODS THAT CAN BE USED TO ENHANCE VALVE OPERATIONS BASED ON STUDY AND ANALYSIS OF THE HISTORY AND PHYSICS INVOLVED?

By MST Corporation Table of Contents:

Page

INTRODUCTION ........................................................................................................................................2 EXECUTIVE SUMMARY ............................................................................................................................2 STRAIN ENERGY ELASTICITY PHYSICS VERSUS DEFORMATION FOR A HPRFV .....................3 STRAIN ENERGY PHYSICS AS IT APPLIES TO A HPRFV .................................................................4 IS THE PREMISE FOR THE OFFSET CORRECT? ................................................................................5 SO WHY DOES A ROTOR-AXIS-OFFSET-DOWN SEEM TO WORK? ..............................................8 ATTACHMENTS ...................................................................................................................................... 11

MST Corporation White Paper Study—Offset Analysis of Bauer High-Pressure Rotary Feeder Valve (HPRFV): Rotor Offset v Bore Profile v Alternatives v CenterSeal™ © Page 2 of 13

Introduction The purpose here is to provide knowledge to Bauer high-pressure rotary feeder valve owners about offset specifications; related problems and solution options for technological and operational improvements.

The analysis reported here demonstrates to Bauer valve owner-users that there are other ways of looking at the operational and mechanical issues. Users are given a perspective that leads to important improvements and cost savings in maintenance, environmental control and energy consumption.

Executive Summary Bauer documents allege elastic deflection (bending) of the drive shaft is the reason for the odd offset, sets. For example, on high-pressure size 18, the nominal offset is, 0.028” for the rotor and 0.020” for the inner bearing seal bore. Bauer assert, based on pressure forces, that the shaft recentered due to bending.

Quotes from Bauer et al documents important to this thesis: (1) “The effects of the bending or deflection [emphasis mine] of the rotor is further controlled by the adjustment of the relative position of the offset of the rotor in relation to the body to provide minimum running clearances under the influence of pressures with minimum pressure loss.” From: (United States Patent; by H. S. Messing [of M&D], 1960/1964)

(2) “Eccentric bearing sleeves installed at the factory provide radial bearing offset to compensate for elastic deformation [emphasis mine] at operation conditions.” From: (Bauer Maintenance Manual 451 (18); Important Notes Section; Paragraph 2)

(3) “eccentric inserts . . . accommodate various conditions of differential pressure to which the rotor may be exposed. . . . where different portions of its rotor are exposed to different temperatures and pressures the rotor will inherently center in its housing [emphasis mine].” From: (United States Patent; By James R Starret; Bauer Bros Company; 1971/1973)

There is not enough pressure force in a vessel to cause the amount of bending/deflection claimed.

See the attached FEA analysis. We tested the bending theory based on two FEA analyses; two different software programs, same results.

However, if one arbitrarily programs the shaft to deflect that much, then the fits; the seal, the centerline et al tend to line up. Reverse engineering analyses points to several factors that are behind the bending theory circulated by the Bauer people.

Here, we offer information that will help the Bauer user to have a better understanding of the physics involved. This will help users‟ develop a healthier understanding of the effects that cause valve operational problems in general Owners of Bauer style HPRFV‟s can benefit by reassessing the soundness of having the rotor and shaft in an axis-offset-down1 position. The forensic data does not support using it.

(4) “Another object of the invention is to provide simple but improved means to pre-set a rotor unit and precondition the bearing support therefore so that in use the rotor will center in its housing and operate .relatively free of friction and imbalance [emphasis mine].” From: (United States Patent; By James R Starret; Bauer Bros Company; 1971/1973)

1 The endbell registers, in the body, are on the same centerline as the body bore axis/centerline.

Axis-offset-down defines the situation where one is directed to use eccentric sleeves around the outer bearing races to cause the rotor to be positioned in the body bore with the rotor axis different from the end bell registers; different from the body bore centerline.

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 3 of 13 © February 22, 2003 Issue 10-0207

A faulty posture of speculation and conjecture (belief) is the reason for the axis-offset-down rotor status publicized for decades by Bauer. Heuristics effectively demanded they (Bauer) devise a rationale. The rationale‟s worth is seriously flawed based on physics.

The heuristic justification Bauer derived and publicized as fact is wrong. The theory behind their belief was based on the idea that elastic bending (force induced deflection) dominated the subject matter.

The true problem was not deflection; it was shape change from heat combined with the affects of torsional friction versus available HP (horsepower) at the valve drive stub connection.

The forensic evidence does support the use of a slight change of the relationship of the rotor to the surface profile of the body bore to aid the operators on first startup of a new valve. This is not the same thing as offsetting the drive shaft relative to the head register fit.

The basis for HPRFV design and function hinges on strain-energy physics as a property of metals used.

In this paper, we will show that an axis-offsetdown rotor setting is not required when the installation is correct and the HP is proper for the application. Point of interest: it is better if the axis offset is not used; instead profile the body bore surface to accomplish the intended goal.

Presetting the rotor axis offset (axis-offset-down) different from the primary bore axis is counterproductive. It increases the wear-in cycle time and it increases the time to form a quality circumferential seal fit. That is, the seal fit, rotor to body bore.

Removing the current rotor axis-offset-down, and replacing it with a CAD (computer-aided design) body bore surface profile—in the upper-bodybore-quadrants—permits operating the rotor on the correct natural centerline. This way, the right relation to the stuffing box, bearing oil seal, and etcetera, are protected.

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Current Bauer specifications; for a typical highpressure application, calls for approximately 0.028” axis-offset-down of the rotor to bore center and 0.020” offset for the bearing oil seal bore.

These fits belong on center. It lessens the wear-in time, permits replaceable stainless steel stuffing box conversions; SealRyt™ type packing systems, and makes the startups and break-in period friendlier; more operator friendly.

The valve does not know the difference if the rotor axis is offset relative to the body-bore or if the rotor and body axes are the same and the bodybore is shaped so the rotor thinks it is offset for the break-in cycle. The rotor does not know the difference.

Placing a prescribed bore profile (CAD designed shape) in the upper quadrant to help compensate for the startup quirks does provide dimensional tolerance for heat distortion effects.

An on-center shaft provides improvements in sealing technologies; longer packing life, simplifies maintenance and the lifecycle run-time is improved.

Knowledge of how the valve truly works will explain the ideas here and decrease typical startup annoyances.

The object of CenterSeal™ technology is to reconfigure the seal and packing relation so they are true to the rotor-shaft axis; the natural centerline of all components.

Keeping the natural centerline for both the rotor and the rotor shaft allows for packing and stuffing box upgrades. Example: upgrades like use of enhanced packing systems. Oil seal reliability is also improved.

Instead of a rotor axis-offset-down, the Bauer valve works better when a specific surface profile is placed into the upper quadrant of the body bore itself.

Strain Energy Physics versus Deflection for a HPRFV

Page 3 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 4 of 13 © February 22, 2003 Issue 10-0207

Strain (in the context here) is defined as elastic deflection (shape change) caused by the pressure forces. Heat causes shape change, but this is a metallurgical property which is treated differently.

Two primary dynamics contribute to shape-change in a HPRFV. They are heat caused metal growth and pressure forces; elastic deflection, called strain.

The elastic deflection side of the problem is easy to deal with based on strain energy physics. That is, when the cross-sectional thickness of the valve components involved is increased then the distortion and deflections, due to pressure, is controlled.

In the beginning, Bauer assumed the effects of thermal shape change observed was a result of pressure forces. They state that in their historical writings. Using an offset rotor, they believed, compensated for their alleged deflection theory.

Bauer‟s premise about this is documented in the Bauer maintenance manuals, patents and other internal papers. These references infer the deflection was multi-faceted and included the endbells—the reason for the bizarre jacking bolt arrangement found on the endbells.

The strain (elastic deflection) comes about in proportion to stress (symbolized here as σ [Greek letter sigma]) based on the elastic modulus (symbolized as Ἓ [Greek letter epsilon]). The deflection, i.e., strain is symbolized here as ἐ [Greek small letter epsilon]. If one pulls a steel test specimen to failure, the stress-strain curve looks like Figure 1. „F‟ symbolizes the Force (the resultant of applied digester pressure in this case). Letting „A‟ symbolize area, then: σ =

F . By inspection, one A

can see that as the area „A‟ increases and the force „F‟ stays the same, the stress „σ‟ decreases. It is the equivalent of moving the stress level down on the vertical axis. See Figure 1.

Existing HPRFV‟s yield very little at their connections, deflection is controlled based on strain energy physics, as described. That said, per the stress strain curve shown in Figure 1, theoretically, the maximum elastic yield (in/in) of the shaft-bearing and endbell connections would be approximately the 0.0012”/in, pointed out. See FEA report at the end of this document.

Strain Energy Physics as it Applies to a HPRFV Using strain energy physics in design means one spreads the load over enough cross section so the deflection (from pressure) is under control and elastic deformation becomes a non-issue in a rotary valve.

Strain energy physics involves working with the slope of the curve for metals within their elastic range. In general, for a typical HPRFV, the goal is to keep the unit stress on the metal to about 2000 psi maximum. There is a functional relationship between psi and deflection (strain) amount. In this case, the maximum psi value effectively sets a design limit for deflection.

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Competent designers would not design up to the limit; therefore, the strain (deflection) value would be significantly less. Strain is defined as  



L

, in

inches/inch. Where „δ‟ equals the change in length and „L‟ equals the original length.

Based on the typical section strength design for a HPRFV, the strain (elastic movement) would be about seven-millionths (0.000007”) of an inch.

This is far below the rotor-axis-offset settings used on a Bauer rotary feeder.

Page 4 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 5 of 13 © February 22, 2003 Issue 10-0207

Most of the claims for deflection center on bending of the shaft. Bending deflection is the strain (deflection) affects of a moment due to an applied load—pressure in this case.

To factor that variable in we contracted with JHI Engineering to perform a finite elemental analysis (FEA) to find out the maximum deflection under the condition of 150-psi digester pressure. Near the maximum digester pressure one would normally encounter.

The maximum deflection—in bending—came in at about 0.0012”. See the JHI report below. This figure is a maximum because we negated the resistance effect of the rotor-shaft combination; the resistance effect of the rotor touching the body bore and the resistance effect of the packing, etcetera.

Let us round the 0.028” number to 0.030”for simplicity. Per the FEA work, the pressureinduced strain (deflection) affect, combined, would be less than two-thousands (0.002”) of an inch. This begs the question, how did they (Bauer) come up with the roughly thirty-thousand inch that is common, and why?

The people that do the FEA work agree the basic thesis in this document is valid and the reason for the much larger offset Bauer promoted all these years is not related to deflection as Bauer claimed.

The information here points to several considerations Bauer overlooked or analyzed incorrectly, as follows: 1. The original idea (Bauer‟s justification for the offset) was based on flawed assumptions.

2. Bauer failed to take into account the profile of the valve based on heat distribution (profile) at hot thermal equilibrium—hot versus cold— after a prolonged stable runtime.

3. Non-equilibrium thermal conditions, in terms of time (transients), are not accounted for in their theory.

5. Improper startup procedures, and their affects, are not accounted for using their stated conclusions.

Is The Premise For The Offset Bauer (Institutionalized all These Years) Correct?

Elastic deflection does not explain the use of an axis-offset-down rotor. Only thermal affects on metals; startup and torsional friction issues, can explain the run problems that caused them (Bauer) to construe the need for their offset theory.

One can calculate the strain-equivalent „ε‟ for a section of each metal type based on the temperature profile. That value can be introduced into the stress-strain curve to find its force equivalent on the curve.

Comparison and analysis about true deflection from a force versus shape change, due to heat, helps in understanding the ideas presented here.

For example, it only takes a temperature differential of about 185 °F to change 1-inch of the body material an amount equal to the 0.0012” mark on the curve in Figure 1.

A typical size 18 valve body-bore can vary about 10 times that amount based on a normal stable thermal profile. It may vary far more when startups are rushed, like operational upsets and transient events that imitate conditions as on a startup.

Another variable: the stainless steel rotor has a higher coefficient of expansion rate and a higher equilibrium temperature by comparison. The stainless steel can vary radially about 54 times the amount above.

The point is: the different metal properties are reacting simultaneously to the heat variations. The combinations are complex, however, the forces producing deflection due to steam pressure, on the metal cross sections involved, cannot account for the offset figures.

4. HP coupled with torsional friction, resisting rotation, is a (key) factor that should have been considered, but was not.

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Page 5 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 6 of 13 © February 22, 2003 Issue 10-0207

The original beliefs by the pioneers in this technology lead to wrong thinking. Likely, they based their theories on damage assessments and sketchy field experiences that were not accurate.

Bauer references damage assessment factors in their patent documents as grounds for “improving [their] prior art.”

The offset engineering was reactionary engineering based on operational problems in the field. The real issue was—and is—how the thermal profile versus dimensional relationship variables (metallurgically speaking) affect how the torsional friction and HP requirements factor into the mix.

In real life, uniform heating of the rotor takes place because it (the rotor) rotates over the heat source. This is not the case for the housing.

The housing bolts to the heat source and therefore is subject to a thermal profile (gradient) disparity, bottom to top. During start-up and/or transient conditions the thermal profile variations are dynamic.

The housing bore will change from its (round) close tolerance cold setting to a slight, complex, egg-shape like form when heated. The rotor, because of even rotational heating, will stay round.

The included angle-rotor-to-housing relation will change because the large end of the rotor grows (from heat) a greater amount compared to the small end.

The rotor carves out (wears-in) the bore to remove the egg-shape and also wears-in to compensate for the thermally induced different included angles; rotor versus body-bore.

The included angle of the rotor taper versus bodybore taper changes from heat and each change differently with respect to each other because of the metallurgy involved.

The body bore starts out life round at room temperature; in the shop. The heat difference at startup causes the body bore to take on an eggshape. As noted, the rotor stays round because it is rotating over the heat source. Imagine what we have just described:

By MST Corporation

hprfv; bauer; offset; physics; strain energy

We have described a condition whereby a new or cold valve is trying to fit a round rotor into an eggshaped body bore; both conditions due to the nature of the thermal effects on startup. It is the round peg into a square hole allegory. In this case, a round peg into an egg-shaped hole.

The offset was a tool (if you will) used to compensate for that round peg into the egg-shaped hole dilemma. In addition, this dilemma effectively increased the power requirement as a direct result of the high torsional friction load it caused.

In sum, the offset was not needed because of deflection, it was needed because the valves did not have enough power to drive through the breakin period. After about 8-hours of uninterrupted operation the rotor and body become thermally stabilized.2 Bauer does not deny the fact it takes about 8-hours; they refer to it in their manuals, etc.

After stabilization has occurred, the body bore is still egg-shaped because the body is static; not rotating like the rotor; different temperature bottom-to-top.

The offset rotor did not seal as well as one fully worn to fit, but it got them by the fitful stalls etcetera related to the torsional friction problem for the duration of the time needed to wear into the bore until it fit, creating an optimal seal, rotor to body.

The full offset amount (nominally about 0.028” on high pressure applications) requires the body-bore to wear-in (become round at hot equilibrium status) until the offset, in effect, disappears, or, more correctly stated; until the egg shape disappears at hot equilibrium operation.

Moving the rotor down 0.028” toward the bottom doubles the clearance at the top, 2 x 0.028"  0.056" , the true offset relative to the body bore surface.

2 Thermally stabilized defines the status whereby the valve parts stay at their normal temperature, and start-out shape (known as a hot equilibrium state), for a prolonged period of time. Long enough to reshape the body bore back to a round condition based on the rotor wearing to fit.

Page 6 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 7 of 13 © February 22, 2003 Issue 10-0207

The taper ratio is 6 to 1 per side. The design for the valve calls for the ability of the rotor to move toward the small end 1-inch during a valve lifecycle.

By design, the Bauer valve unit has a theoretical lifecycle equal to the 1-inch of axial travel. The rotor will fit the body bore all around (at hot equilibrium) when the axial travel reaches about 3 /8”, i.e., 6 x 0.056"  0.360" .

The effect is the bore—in operation—moves (because of wear) to the same axis of the rotor.

This occurs over time, as the rotor is moved (wears-in) axially toward the small end; known as the break-in period.

The break-in period varies depending on the skill of operators in combination with the usable horsepower at the drive shaft. Overcoming torsional friction variables during the shaping (rounding) time period is functionally realted to these two chief variables.

The valve is designed for a lifecycle defined as 1inch total axial travel, then by definition, after the 0.056” top gap disapears; because the rotor effectively laps itself into the body bore until it fits all around.

At the point the 0.056” top gap is gone; and because the rotor is fixed in the bearing centers, the rotor and its shaft centerline become the same as the lapped in bore. This leaves about ¾” of axial lifecycle left.

One could ask: if the rotor being offset is a requirement why the discrepancy; most of the designed lifecycle of the valve takes place after the offset is gone?

Assuming one has enough HP to overcome the torsional friction, then that last approximately ¾” of movement takes place without the existence of any offset (radial difference), top, sides, or bottom.

It is very important to recognize the part HP plays in the successful (trouble free) operation of a Bauer valve.

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Horsepower is what determines if the users can maintain a close (minimal radial clearance) rotor to body seal fit. One can see there is a functional relationship between; (1) radial clearance, (2) HP and (3) amperage. These three factors can be varied to improve opetations.

The power available at the drive is a controlling factor as to how friendly the valve will seem to the operators throughout the valve lifecycle. Higher HP always will help make operations seem friendlier during startups and/or transients.

In a metallurgical sense, it takes about eight hours for a HPRFV to reach true thermal equilibrium.

When the startup is pushed too quickly or there is operational thermal upsets. The bottom to top thermal gradient causes shape change.

The thermal bore distortion increases and there is a greater torsional frictional resistance. That is, a greater demand for power to compensate for the increased frictional resistance. The valve tends to stall or act erratically.

Operationally, a taper plug rotary valve is all about power (usable HP) because the rotor-tobody clearance control is functionally regulated by monitoring—and maintaining—the amperage (friction) range for the drive.

The amperage range (by Bauer‟s definition of how to operate) tells the operators when the taper rotor is seated, based on amperage, functionally related to an acceptable level of friction versus the functional relation to motor size There has been a tendency—over the years—to increase horsepower to compensate for amperage kick-outs compared with the original lower horsepower units. Nothing is more frustrating to an operator than to be saddled with an underpowered valve or a valve that looses too much power through the drive train, etcetera.

The higher HP helps, as the rotor-to-body seat tightens up over time. However, reserve power is what eases the burden on the operators and operations.

Page 7 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 8 of 13 © February 22, 2003 Issue 10-0207

The worn-in fit makes the better seal, but is more sensitive to the increased friction loads related to the thermal transients described. The transient friction factors, in general, increases the HP demand based on higher torsional friction.

The thermal issues outlined above (in combination or individually) give rise (no pun intended) to false speculations and analyses. The original theory for the offset persists based on perpetuated and mistaken conclusions first promulgated in the 1950‟s.

Using the knowledge condensed here, it is possible to pre-shape the body bore to provide all the benefits an offset may provide with the added improvements available when all axial relationships are coincident—the same.

Benefits like improved sealing and sealing options. Longer life in the packing system; the bearing seals and packing are truly on center; simpler maintenance (no offset bearing sleeve required) and etcetera.

So Why Does a Rotor &Shaft-Axis (Original Bauer)-Offset Seem to Work?

The exact events leading to the false conclusion for the offset value are lost in the past. However, based on forensic analysis and reverse engineering work the following conclusions can be inferred: 

The rotor is stainless steel and the body is mild steel.



Originally they manufactured the rotor and the body without an offset.



The coefficient of thermal expansion between these two metals is a net difference of: 3.56 x [(Operating temp  Room temp ) in / in /deg F

x (total inches )]



The greatest growth takes place with the stainless steel.

By MST Corporation

hprfv; bauer; offset; physics; strain energy



The top side of the bore is less temperature than the bottom side. Hence an inherent egg shaped bore surface on a new or cold valve.



The real time reaction to too much friction (high amp loads) is not quick enough because it is fundamentally manually controlled and the information feedback for the operators‟ places the operator at a disadvantage.

The rotor back-off (after touching) specification for startup (see Bauer startup procedure) of the valve is 3 to 4 seconds on the limit torque based on amperage feedback (the touchdown indication).

This translates to about 0.003” axial movement; about 5-ten thousands (0.0005”) increased radial clearance. Note: based on the limits of amperage (HP) the correct running clearance, by definition, becomes the ongoing seated rotor control reference.

Based on the differential growth of the body versus the rotor and the uneven profile, bottom to top of the body, these factors can lead to rubbing contact severe enough to cause stalling problems.

Depending on the rate of heat-up (thermal shape change) the interference at the top (rotor versus body-bore) may range from a theoretical minimum of 0.012” to a maximum of about 0.060” for the high pressure units on new valve startups.

The actual values depend on warm-up rates and/or rates of change initiated by transient events.

Originally, they (Bauer) misinterpreted the difference as “deflection” of the rotor due to pressure. In the case of steam there is a functional relation between pressure and temperature. As such, there is a quasi metallurgical relationship; temperature versus pressure.

Different temperatures at different pressures (the functional relationship) better explains the historical offset range of 0.012” to 0.040” (0.024” to 0.080” at the top) based on pressure and valve size for all sizes of valves, as noted in the Bauer documentation—tables.

The rotor stays round because it rotates over the heat source (like a Bar-B-Q spit); heats uniformly and is equal to the vessel temperature.

Page 8 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 9 of 13 © February 22, 2003 Issue 10-0207

For the tapered rotor to seat, it is necessary to wear-in the egg-shape body bore to fit the round rotor and to rematch (wear-to-fit) the included angle of both rotor and body-bore, over a steady hot-equilibrium run-time period; the time is functionally related to available power.

The perceived contact at the top of the bore— because of thermal shape change—lead to the view they (Bauer) needed to back off the rotor axially. That is, move the rotor back, then down,3 which lead to the general rotor setting on a cold valve assembly.

In the one sense they overlooked the thermal dimensional changes described. However, in another sense, by shifting the rotor to a rotor-axisoffset-down—in a crude way—it dealt with the thermal distortion problem—albeit a quasi do-ityourself (partial) solution.

The “round” (heated) rotor will have to wear-in (all) surface contacts until its axis matches a mostly round bore when the valve is at thermal equilibrium.

Most importantly, the offset helped lower the torsional friction, or stated another way, helped make it possible to operate based on the limited HP available in those days.

Torsional friction effectively sets (defines) the HP that needs to be available for the intrinsic radial clearance established for a good operational seal.

When it comes to the HP versus torsional friction, it is, metaphorically, the proverbial chicken or egg problem. Generally, not enough attention is given to the HP requirements versus operational troubles.

At the same time they were closing the rotor to body clearance on the pressure side of the rotor; essentially, providing a quasi seal on the pressure side long enough for the rotor to wear (round up) the egg-shape bore profile.

What the data here demonstrates is the true rotor to body fit is not a deflection problem per se. It is a thermal profile problem in conjunction with the limits placed on the operation of the valve related to real-time torsional friction and the available HP to overcome the friction.

Creating an axis-offset-down-rotor was an indirect way to make operation friendlier, specifically when the HP was inadequate for the operational conditions. That is, when the valve assembly distorts from uneven heating.

Because it is a thermal profile issue, the better course of action is to predefine the body bore using an obround-like (shaped) bore. That is, precondition the bore shape to deal with the problem.

Some wear-in is always required, especially on start-up and during the break-in period because of heat distortions; noted. The Bauer offset is effectively a crude built-in HP (amperage) control mechanism when the body is moving around due to uneven heating and initial wear-in is taking place.

Using the rotor offset approach is a crude alternative for dealing with heat variation. It leads to other problems and interferes with important improvements that make operation and maintenance easier.

Summarized, the true effect of an offset rotor was to provide room, mostly at the top and sides of the body-bore to compensate for thermal variations in shape of the body-bore, especially on startup.

Shaping the bore surface profile allows a truer seal at the bottom bore quadrant and near ideal seal on the entire circumference of the rotor-to-bore fit.

In addition, as noted before, the packing and oil seal fits can then operate on true center with the rotor, allowing a number of changes that improve the mechanical reliability of the valve units; improve packing seal options; save on steam consumption, to name a few.

3 It is the taper that requires the rotor be moved back then down.

The 6 to 1 taper per side requires one to move the rotor back axially six units for every one unit of offset desired. This is also the reason the clearance doubles at the top.

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Page 9 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 10 of 13 © February 22, 2003 Issue 10-0207

The goal here is to make known information that will help Bauer valve users see ways for Bauer valve improvements that will advance technology in this field and promote the advantages of having the seal area, packing area and rotor to body coaxial relationship.

The Better Method(s)- ReassessmentTime Tested MST-Bauer CenterSeal™ Design & Related Improvements:

Summing up, a controlled bore surface profile method, i.e., CenterSeal™ design—coupled with reassessment of one‟s HP and drive limitations, etcetera—directly deals with the true issue outlined here.

That is, the historical offset rotor method was based on a flawed theory and is cause for numerous operational problems to this day.

Ray Lackey Go to attachments:

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Page 10 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 11 of 13 © February 22, 2003 Issue 10-0207

Attachments

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Page 11 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 12 of 13 © February 22, 2003 Issue 10-0207

BAUER SHAFT WIREFRAME SHOWING LOADING DISTRIBUTION JHI Engineering, Figure ‘1’

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Page 12 of 13

Print Date: 3/2/2010

WHITE PAPER - THE NATURE OF USING AN OFFSET ROTOR FOR A BAUER HIGH PRESSURE ROTARY VALVE—ANALYSIS OF THE TOPICS; PROMOTE BETTER ALTERNATIVES Page 13 of 13 © February 22, 2003 Issue 10-0207

BAUER SHAFT DISPLACEMENT GRADIENT PLOT ‘Y’ DIRECTION JHI Engineering, Figure ‘2’

Appendix A

By MST Corporation

hprfv; bauer; offset; physics; strain energy

Page 13 of 13

Print Date: 3/2/2010