1200-01082-rpt-001r0 boilers ongoing service assessment

Engineering

TES Group Inc. 9021 – 24 Street

Edmonton, Alberta T6P 1L2 Phone: 1-587-760-3200

Fax: 1-587-760-3467 Form No.: EF-012 Revision No: 00 Technical Report

Page: 1 of 19 Form Rev Date: 20190701

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Client: University of Regina

Site: Central Heating Plant

Document Title: Boilers On-Going Service Assessment

TES Job No.: 1200-01082

Rev. No.: Date Description Prepared by: Checked by: Approved by: YYYY-MM-DD

0 2021-01-19 Final Report M MacKenzie J Giles J Milne

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Revision Summary

Revision Description of Changes

B Corrected Mud Drum Material in Table 3‐5. Added list of key procedures to Recommendation

#8. Added Boiler Scorecard A Draft

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Contents 1. Executive Summary ...................................................................................................................................... 4

2. Background / Project History ..................................................................................................................... 5

3. Overview of Boiler Design ........................................................................................................................... 6

3.1 Original Design Data ..................................................................................................................................... 6

3.2 Significant Retrofits ....................................................................................................................................... 6

3.2.1 Common Retrofits .................................................................................................................................. 6

3.2.2 Boiler 3 Burner Upgrade. ...................................................................................................................... 6

3.2.3 Boiler 3 Economizer Addition ............................................................................................................... 7

3.3 Pressure Part Details .................................................................................................................................... 7

3.4 Suitability of Pressure Part Material for Continued Service .................................................................... 8

3.5 – Prohibited Materials ................................................................................................................................... 9

3.6 – Balance of Plant Equipment ..................................................................................................................... 9

4. Review of Operating and Maintenance History ................................................................................... 10

4.1 Boiler Operating Data ................................................................................................................................. 10

4.2 Review of Start Ups .................................................................................................................................... 12

4.3 Operating Procedures Review .................................................................................................................. 13

4.4 Water Treatment Program ......................................................................................................................... 13

4.5 Water Treatment Operational Data .......................................................................................................... 13

4.6 – Maintenance and Inspection History ..................................................................................................... 16

5. Possible Regulatory Issues ...................................................................................................................... 17

5.1 – NOx Emissions .......................................................................................................................................... 17

5.2 – Greenhouse Gas / Efficiency ................................................................................................................. 17

Appendix A Boiler Scorecard ........................................................................................................................... 18

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1. Executive Summary

At the request of the University of Regina’s Maintenance & Utilities Department, TES Technical Services has reviewed design, operational and regulatory issues to assess if the existing boiler in the Central Heating Plant can be kept in service for approximately another 10 years. This review has determined that the original design and materials of construction should be suitable provided the boiler operation is standardized and that a more proactive inspection program is developed and undertaken.

Full details are provided herein. Specific recommendations are as follows:

Recommendation #1 – U of R should undertake a random spot check of tube thickness to verify margin is still available.

Recommendation #2 – U of R to include an inspection specifically looking for pressure part corrosion. This should initially consist of visual inspections of hot side and cold side of tubes as well as inside of drums.

Recommendation #3 – U of R to inspect specifically for deposition in boiler tubes and drums.

Recommendation #4 – U of R to review possible roadblocks should repairs or modifications be required for SA 212 GrB drums.

Recommendation #5 – As a proactive measure U of R to review if asbestos containing material are present and if so to mark affected areas.

Recommendation #6 – U of R to inspect non-critical equipment for corrosion and structural issues.

Recommendation #7 – A standardized procedure should be developed to monitor pressure raising from both cold and standby conditions.

Recommendation #8 – U of R should review key operator activities and document them using procedures.

Recommendation #9 – U of R to review reasons for non-adherence to water treatment criteria and develop procedures to ensure maximum compliance.

Recommendation #10 – U of R to develop an overall plan to undertake recommended inspections as expeditiously and practically as possible.

Recommendation #11 – U of R to monitor regulatory environment and develop a budget price for burner retrofit on Boiler 1 and 2.

Recommendation #12 – U of R to monitor regulatory environment and develop a budget price for economizer retrofit on Boiler 1 and 2.

In addition a Boiler Scorecard summarizing key major issues reviewed can be found in Appendix A.

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2. Background / Project History

The University of Regina Central Heating Plant (U of R CHP) operates three boilers. These boilers are all over 50 years.

The objective of this independent study is to determine the present condition of these steam generators and looking out approximately (10) years, determine if these boilers are suitable for continued operation or alternatively, due to their age are candidates for replacement. The University of Regina Maintenance & Utilities Department is undertaking this initiative because of the critical nature of these boilers in supplying safe, clean, and reliable heat for the needs of the campus infrastructure. Of major concern is public safety and an appreciation that such fired pressure equipment has a finite life.

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3. Overview of Boiler Design

3.1 Original Design Data

The U of R CHP has three package boilers. Key design parameters are presented in Table 3-1.

Units Boiler 1 Boiler 2 Boiler 3 Start Up Year 1966 1966 1971 Rated Steam Flow Lb/hr 30,000 60,000 60,000 Steam Drum Pressure Psig 182 182 197 Feedwater Temperature Deg F 225 225 225 Gas Temperature to Stack Deg F 580 545 593 Estimated Operating time including pressurized standby

Hours 450,000 450,000 400,000

Manufacturer Babcock & Wilcox – Goldie Mccullough

Babcock & Wilcox Canada Ltd.

Table 3-1 Original Design Data

3.2 Significant Retrofits

The U of R has regularly invested in maintaining and upgrading the CHP. Some of the more significant retrofits

are discussed below.

3.2.1 Common Retrofits

The control systems have been upgraded over several years. Key instrumentation has been updated and a PC based Delta V control system is used on all three boilers.

3.2.2 Boiler 3 Burner Upgrade.

In 2008 the original two burners on Boiler #3 were replaced with a single low NOx burner. This burner was provided by Process Combustion Systems. The nameplate data for this upgrade states the intent of the retrofit was to lower NOx emission to no more than 50 ppm while also maintaining the original 10% excess air levels.

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3.2.3 Boiler 3 Economizer Addition

In 2007, an economizer was added to boiler No 3. Table 3-2 provides a comparison of MCR performance before and after the retrofit.

Parameter Units Original Economizer Added

Steam Flow Lb/hr 60,000 60,000 Feedwater Temperature to economizer

Deg F N/A 225

Feedwater Temperature to boiler

Deg F 225 288

Stack Gas Temperature Deg F 593 356 Boiler Efficiency 76.6 % 82.2 % Natural Gas Flow Cubic feet /

hr 75,300 70,220

Table 3-2 Boiler 3 Economizer Addition Details

3.3 Pressure Part Details

The University of Regina has provided original design information related to materials of construction.

Component Material Diameter Design Pressure

ASME minimum

wall thickness

Minimum wall thickness specified

Furnace Wall Tubes

SA 178 A 2.0 in. OD 250 psig 0.032 in. 0.095 in.

Generating Bank Tubes


Steam Drum SA 212 Gr B 36.0 in. ID 250 psig 0.507 in. 0.75 in. Mud Drum SA 212 Gr B 24.0 in. ID 250 psig 0.338 in. 0.625 in.

Table 3-3 Boiler 1 Pressure Part Details


ASME minimum

wall thickness

Minimum wall thickness specified

Furnace Wall Tubes




Steam Drum SA 212 Gr B 36.0 in. ID 250 psig 0.507 in. 0.75 in. Mud Drum SA 212 Gr B 24.0 in. ID 250 psig 0.338 in. 0.625 in.


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ASME minimum

wall thickness

Minimum wall

thickness specified

Furnace Wall Tubes




Steam Drum SA 515 Gr 70 41.875 in. ID 250 psig 0.507 in. 0.75 in. Mud Drum SA 515 Gr 70 24.0 in. ID 250 psig 0.338 in. 0.625 in. Economizer Tubes

SA 178 A 2.0 in OD 275 psig .034 in. 0.105 in.

Economizer Header

SA 106 Gr B 4.5 in. 275 psi 0.065 in. 0.272 in.


3.4 Suitability of Pressure Part Material for Continued Service

The components summarized in Tables 3-3 to 3-5 are all Carbon Steel. The CHP boilers operate at ~ 165 psig. The boilers produce saturated steam. The operating temperature of the pressure parts will be very close to the saturation temperature of 373 oF.

The pressure parts original design has substantial margin. A random check would be useful to verify thickness.

Recommendation #1 – U of R should undertake a random spot check of tube thickness to verify margin is still available.

Carbon Steel service life is not limited by Creep until operating temperatures meet or exceed 750 oF. With this in mind, there is no reason why the boilers could not continue to operate unless one or more of the following occurs:

Corrosion causing wall thinning. This can occur either at high temperature during operation or at low temperature when the boilers are out of service.

Excessive waterside deposition leading to local temperature excursions. Excessive stress due to improper operation, particularly during start ups.

Recommendation #2 – U of R to include an inspection specifically looking for pressure part corrosion. This should initially consist of visual inspections of hot side and cold side of tubes as well as inside of drums.

Recommendation #3 – U of R to inspect specifically for deposition in boiler tubes and drums.

It should be noted that the Steam and Mud Drums for Boilers 1 and 2 are fabricated from an obsolete material specifically SA212 GrB. Should the need arise to modify or repair these components procedure qualification would not to be done on an exception basis and may require significant review by TSASK.

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Recommendation #4 – U of R to review possible roadblocks should repairs or modifications be required for SA 212 GrB drums.

3.5 – Prohibited Materials

Given the age of the boilers it is possible that asbestos containing material may have been used in refractory and/or insulation. It would be a useful activity to audit for the presence of any such material. This would allow for avoiding delays if repairs were needed in affected area and asbestos only discovered during any such repair.

Recommendation #5 – As a proactive measure U of R to review if asbestos containing material are present and if so to mark affected areas.

3.6 – Balance of Plant Equipment

While this review has focussed specifically on the boiler, units of this age typically have corrosion and/or structural issues on non-critical equipment including ducts, windbox, flues, expansion joints and stack.

Recommendation #6 – U of R to inspect non-critical equipment for corrosion and structural issues.

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4. Review of Operating and Maintenance History

As noted in Section 3, all boilers in the Heating Plant have been retrofitted with new control systems. A review of operating data provided to TES demonstrates that the current control system and related logic provide reliable boiler operation. Specific comments follow below.

4.1 Boiler Operating Data

As shown in Figure 4-1. below, during the Fall and Winter Months Boiler 3 is the primary steam source. During this time boilers 1 and 2 are occasionally operated with Boiler 1 operating most often. In the late spring and summer Boiler 3 is taken out of service and any required steam is typically provided by boiler 1.

Figure 4-1 Typical Steam Demand

How a boiler responds to load variations can cause detrimental effects if not controlled with consistent and minimal changes to other parameters.

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Drum pressure variations with load changes are presented in Figure 4.2. Control is very stable typically staying within a band of ~ 2 psi.

Figure 4-2 Drum Pressure vs Load

Gas temperature exhausting the unit follows an expected pattern and is presented in Figure 4.3. The absence of any excursions ensures flues and expansion joints would not be overstressed. Also avoiding excursions avoids overheating in the economizer.

Figure 4.3 Stack Gas Temperature vs Load

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As shown in Figure 4.4 Stack gas oxygen follows load in a typical manner. It is noted that excess oxygen varies from 2.5 to 3.5% from ~ 50 -100% of rated capacity. This ensures that heat losses are minimized.

Figure 4.4 Stack Oxygen Level vs Load

4.2 Review of Start Ups

The review of operations above shows that while operating the boilers are well controlled. One other aspect of operation that can affect boiler reliability is limiting the rate at which boiler pressure is raised. More specifically limiting the increase in saturation temperature is key to avoid overstressing the drums and rolled tube seats. For drum boilers such as those in the heating plant it is typically advisable to limit saturated temperature increase to be less than 100 deg F/ hour. This can be ensured by either using thermocouples on the steam drum or by monitoring drum pressure. Figure 4.5 summarizes both approaches.

Figure 4.5 Boiler Start Up Recommendations

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At the present time, the control system does not record drum pressure when the unit is not producing steam. TES has been advised that typically the start up goes very slowly taking up to 8 hours. Thus, although undocumented the intention of current operating practice is correct.

Further, the nominated standby boiler is held at 100 psig. It is much easier to avoid excessive pressure raising rates.

Recommendation #7 – A standardized procedure should be developed to monitor pressure raising from both cold and standby conditions.

4.3 Operating Procedures Review

At the present time there are no site specific operating procedures. While the existing staff may be well trained and experienced documenting current practices would ensure adherence in the future. Based on TES’s experience, key operator activities that should be captured in procedures include:

Start up Shutdown Lay up Blow Down Boiler Water Chemistry Control Low and High PH Excursions Drum Level Gauge Glass blow down. (In the event of a failure, this will be looked for and

scrutinized) Upset Conditions Trip Testing and Instrumentation Calibration

Recommendation #8 – U of R should review key operator activities and document them using procedures.

4.4 Water Treatment Program

The U of R CHP boiler and feedwater treatment program is administered by PACE Solutions. In addition to providing recommended water chemistry and chemicals they also have remote monitoring capabilities. PACE has established an all-polymer program. The chemicals and control points meet or exceed ASME/ABMA recommendations.

4.5 Water Treatment Operational Data

Water treatment data was provided by U of R CHP for review.

Key to any water treatment is ensuring chemical dosage. Polymer levels are checked indirectly by measuring for a tracer included in the formulation. Typical results are shown in Figure 4.6.

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Figure 4.6 Polymer Tracer

This data shows that the recommended tracer levels are not often met. Of course, the practical impact is adherence to key water chemistry parameters. Sodium Sulfite is used to control corrosion and pitting. As can be seen in Figure 4.7 adherence was good during Winter 2019/2020 and less so during the Fall of 2020.

Figure 4.7 Boiler Water Sulfite

Additional corrosion and pitting protection is provided by maintaining Hydroxide levels which are checked by measuring alkalinity. Again, adherence in the Fall of 2020 was not generally achieved as shown in Figure 4.8.

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Figure 4.8 OH Alkalinity

This same pattern is repeated when reviewing Conductivity which is important in avoiding deposition. Operating results are shown in Figure 4.9.

Figure 4.9 Boiler Water Conductivity

While only a single year of operation has been provided it is clear that adherence to water chemistry can vary significantly. Clearly a more consistent approach would be of value.

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50

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Dec‐2019

Jan‐2020

Feb‐2020

Mar‐2020

Apr‐2020

May‐2020

Jun‐2020

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Sep‐2020

Oct‐2020

Nov‐2020

Dec‐2020

Boiler 3 ‐Alkalinity

Boiler 3‐OH Alkalinity PACE Recommendation

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Recommendation #9 – U of R to review reasons for non-adherence to water treatment criteria and develop procedures to ensure maximum compliance.

4.6 – Maintenance and Inspection History

The only regular inspections are conducted by TSASK. These inspections are limited to ensure compliance with existing license requirements.

Since the greatest risk to boiler integrity are likely localized deposition and corrosion, additional inpsections looking at specific areas of the boiler would be recommended. Specific recommendations have been made earlier in this report. Prioritizing and linking them will be key to implementation.

Recommendation #10 – U of R to develop an overall plan to undertake recommended inspections as expeditiously and practically as possible.

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5. Possible Regulatory Issues

One consideration for keeping these boilers in service for the longer term would be the need to retrofit if legislation was enacted. At the present time TES is not aware of any pending legislation but can comment on how other operators have been affected.

Two areas we are aware of in other applications are:

1 – The need to retrofit burners to reduce NOx emissions; and,

2 – The need to improve thermal efficiency.

5.1 – NOx Emissions

Existing legislation that affects boilers similar to those operated by the U of R is contained in The Multi-Sector Air Pollution Regulations issued by Environment Canada in 2016. While many industrial boilers are affected, those in Institutional Settings (i.e., Education, Hospitals, etc.) are not included.

In order to assess if legislation of this type could be an issue in the future for the U of R it is possible to consider what others have to meet for similar boilers firing natural gas. Specifically, other users need to reduce NOx emissions to 26 g/GJ if the boiler is operated more than 500 hours per year.

The previous retrofit of boiler 3 would meet the required emissions level based on nameplate data. Boiler 2 would likely be exempt based on the low number of operating hours. Boiler 1 would need a retrofit similar to that successfully implemented on Boiler 3.

Recommendation #11 – U of R to monitor regulatory environment and develop a budget price for burner retrofit on Boiler 1 and 2.

5.2 – Greenhouse Gas / Efficiency

At the present there is no comparable Existing legislation that mandates boiler efficiency. In general terms new boilers would be required to include an economizer.

Boiler 3 has been retrofitted already while Boilers 1 and 2 would require economizers should a mandate be implemented in the future.

Recommendation #12 – U of R to monitor regulatory environment and develop a budget price for economizer retrofit on Boiler 1 and 2.

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Appendix A Boiler Scorecard

1200-01082-rpt-001r0 boilers ongoing service assessment

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