Design for Constructability A Method for Reducing SCR Project Costs J.A. Hines Babcock & Wilcox Construction Company Mt. Holly, New Jersey, U.S.A.
D.S. Fedock Babcock & Wilcox Construction Company Barberton, Ohio, U.S.A.
BR-1720
Presented to: The U.S. EPA/DOE/EPRI Combined Power Plant Air Pollutant Control Symposium: “The Mega Symposium” August 20-23, 2001 Chicago, Illinois, U.S.A.
Abstract Recognizing that construction costs for SCR Projects can exceed 50% of the total project cost, and given that the resources (labor and heavy equipment) required to complete these projects are a significant component of that cost, it is prudent to design the project for “constructability” of the assembled components, ensuring maximum efficiency of these valuable resources.
Introduction The cost of labor presents both the greatest opportunity and risk for any SCR project. With the limited availability of labor and demands upon labor across the country, it is essential that the labor on these projects be efficiently utilized. Work can be done up front with engineering and construction working together to integrate the construction plan into the process to ensure deviations from the plan (and their associated cost) are minimized. The goal of designing for constructability seeks to minimize impacts and improve productivity through the elimination of rework and/ or corrective work, material deliveries, and modularization (either off site or on site). Constructability is accomplished by designing “user friendly” connections between the components to be assembled. It involves up-front determination of splice locations and module limits that determine the erection plan. The plan (to the maximum extent possible) limits the amount of “leave-out” steel required during erection. Designing for constructability means the construction plan drives the engineering and procurement efforts, in effect,
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pulling the engineering outputs through the process rather than the opposite. To be most effective, the construction plan should be fully integrated into the overall project schedule, complete with ties to engineering, procurement and delivery. Designing for constructability will not reduce the cost of the design phase of the project; thus the concept may be rejected by some at the outset. The payoff requires vision. It manifests itself during construction, where all of the time constraints converge and all float in the schedule disappears, sometimes due to inefficiency or misdirection of the engineering and procurement efforts. The real savings and benefits lie in reliability and predictability. These savings are realized through productivity and the efficient use of labor and equipment. Since every job will have its share of delays due to equipment failure and acts of God, the goal of constructability is to pick those attributes of the project that can be controlled and exercise maximum influence over those attributes that offer the biggest payback.
Background The recent demand for construction labor and declining workforce have created a situation that requires increasing the ranks of skilled labor while maximizing the productivity of those workers that are available. The shear volume of anticipated work will likely lead to spot manpower shortages over the next few years. Significant increases in the ranks of skilled labor will not occur overnight. Therefore, even more focus is placed on maintaining and even improving labor productivity. See Figure 1.
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Boilermaker membership.
1994
This figure indicates the decline in active membership in the boilermaker ranks from 1994 until 1999. A variety of factors contributed to the decline, including uncertainty in the utility labor market due to deregulation and the deferment or delay in capital project decisions. Utilities were busy interpreting U.S. Environmental Protection Agency (EPA) regulations and determining an appropriate response. Also, activity on new boiler construction was virtually non-existent during this period. As a result, much of the skilled labor switched to other industries, or retired during this downturn, and the trend of an aging skilled labor force continued. The rate of attrition through retirement outpaced the number of apprentices added to the work rosters. Complicating matters has been the increase in demand for construction services. There are many factors driving the increased demand including owners investing in their newly acquired assets, low NOx burner retrofits, SCR installations, new power plant construction (primarily combustion turbine projects), as well as ongoing routine maintenance at operating facilities. That said, it should be noted that the demand for this skilled labor is not limited to the Utility Industry. See Figure 2. Projections of the demand for Construction Labor (specifically Boilermakers) are provided in Figure 3. It is evident from these projections that the largest increase in the demand for this labor will come from NOx Reduction Projects over the next few years. These factors have the combined net effect of creating nearly full employment in the industry. Figure 4 shows the trend over the last four years. Figure 5 presents geographic data on Boilermaker Utilization for 1998. Figure 6 presents the same geographic data for the first part of the year 2000. There is tremendous competition for these valuable labor resources. The competition is not only between contractors who employ labor, but also between Owners aggressively trying to complete projects in a narrow window of opportunity.
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Boilermaker manhour forecast.
Constructability Constructability begins early in a project’s design phase. Because these projects can require significant amounts of concrete, structural steel and fabricated platework, input from the erector is a key step toward ensuring scheduled completion. A typical SCR project can require the installation of 500 cubic yards of concrete or significant quantities of piles, 1,000 tons or more of structural steel and an equal amount of fabricated platework. Each project presents its own set of circumstances, due to the plant’s geographic location, available real estate, laydown area and interferences (both above and below grade). Once a general arrangement of the project is available, it can be utilized for constructability planning. If the site location, arrangement and access lend themselves to modularization, off-site modularization should be considered. If barge access is not available, chances are on-site modularization of sub-assembled components will be planned. When a location for the cranes required is determined, selection and sizing can be accomplished. A determination must be made as to the limiting component of the rigging scheme. Do the site conditions limit the crane size? If so, the largest module (or assembly) to be fabricated will be limited by the available hook capacity. If the space available is adequate for virtually any module size, a determination needs to be made as to the optimal module size or component to be lifted. (Many times, the limiting component may be a reactor support plate girder, and not a particular section of fluework).
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Boilermaker demand by industry.
* = Actual MHRs / Active Members x 2080
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Boilermaker employment level.
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0-60% 61-80% 81-100% Over 100% Figure 5
Boilermaker employment utilization - 1998.
0-60% 61-80% 81-100% Over 100% Figure 6
Boilermaker employment utilization - 2000.
Once the weight of this largest component is identified, crane selection can be accomplished. Project economics may drive the decision away from the largest (and most expensive) crane. In many instances, the best crane for the job is not the largest. Large cranes (over 250 ton capacity) can range in cost from $30,000 to $130,000 per month, and freight costs to the job can exceed $100,000. Jumping up in size to the next larger crane can increase the equipment cost by a factor of two or more. Typically, due to the arrangement of the SCR, two of these large cranes, equally sized will be required. For large projects posing unique or complicated arrangements, crane costs alone can run upwards of $250,000 per month. When projected over the duration of the project, the cost can be several million dollars. A crane placement arrangement drawing should be developed to convey the specific requirements relating to laydown area, fabrication subassembly area, crane swing radius, and lifting capacity at various points. Many times, early in the project, specific information about weights cannot be accurately ascertained due to the preliminary nature of the information available. This is a risk early on, but sound judgements can be made based upon the experience of the erector. Module identification will set the boundaries for assembly. The erector determines which locations are best from a variety of standpoints, including access, crane capacity and geometry. Once the sub-assemblies are identified, work can proceed to schedule the order of erection. But, the emphasis needs to be on the ability to work the erection plan to the maximum extent possible. Most large SCR Projects require some sequence of erection that involves erecting a lower tier of steel, setting portions of the SCR outlet flue and Reactor Box, then proceeding with the upper
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tiers of steel to a point where the inlet flue can be set. The biggest issues here become the coordination of subcontractors or the different trades assigned the work. In order that everyone involved in the process understands this erection sequence, a detail should be developed that conveys the pertinent information and sequence. Refer to Figure 7 for an example of an erection sequence drawing. The established erection sequence can also be used to focus priorities on detail design and fabrication efforts. If the project schedule is compressed, it makes sense to prioritize those efforts that support the erection plan. Receiving material far in advance of the time required at the job only adds costs and burdens the job with the additional cost of material handling. It may also force the job to work on activities that deviate from the intended plan. The most efficient projects will not deviate from the construction plan. Prior to the issuance of key design outputs, the erector should be asked to review and comment on the issues from a constructability standpoint. Many times a preliminary review can catch simple items missing or incorrect information that, if left unchecked, may lead to costly rework, or delays in production during critical path activities while waiting for revised engineering documents or pending engineering evaluation. Suggestions offered here can pay back many times over. Once the modules are identified and an erection sequence is established, the erector can work with the platework vendor and influence delivery. This allows the erector to review and approve the shop’s plan for panelization. The benefits of this are twofold. First, it provides the erector with valuable information and knowledge about the material to be received, including the extent of work required on-site to pre-assemble modules. It also enables the erector to suggest alternate shipping units that may save costly field labor and improve on-site productivity. In most instances, this adds no cost to the fabrication especially if a shop is awarded the material supply on a unit cost basis and is indifferent to the location of shipping splits. A subtle change here could reap huge rewards in the field where the cost of assembly is significantly greater. Flues should be bottom supported where possible, and ideally the identified modules will be self-supporting (even if this requires some shop-installed temporary supports). This self-supporting feature is ideal because it can allow modules to be released from the crane quicker than if the piece had to be held in place until welded out. Winds in excess of 25 mph can shut down crane operations. This can limit the window of opportunity for rigging components into place. The use of fit-up bolts between adjacent panels or modules can help improve productivity and limit adverse effects associated with weather and wind. There are other seemingly simple constructability items that can improve labor productivity. Due to the extensive amount of work that is required inside the fluework and SCR Reactor, large access doors assist in getting workers and equipment inside where they are required. There can be literally miles of welding to be accomplished inside the Reactor and flues. Module identification assists in door placement, and in many instances, a door can be added if it helps the construction effort. Since it is typical that a good portion of the welding for these projects consists of a continuous seal weld on the inside surfaces (with stitch welding on the outside), it makes no sense to limit access to the work areas. Assembly generally requires a significant amount of scaffolding. A good construction plan will identify those modules that require scaffolding to access welding locations. Once identified, scaffold brackets or fixtures can be installed on ground prior to lifting to save costly scaffolding labor.
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Figure 7
Erection sequence drawing.
It is also important to know the material type of any fluework being demolished. This may alter the demolition plan. Some materials suffer from temperature embrittlement, increasing the likelihood of material failure during demolition. Additional precautions are therefore required for safety and personnel protection, including specialty jigs or rigging equipment, or this may require demolishing the fluework in smaller pieces. It is also likely that demolition activities will occur over a longer period of time. The main point here is the recognition that there can be issues relating to the installed materials and clear communication is required between owners, engineers and erectors. For some organizations, designing for constructability is relatively straightforward. For others, it may involve embracing a change in their conventional way of doing business. Given that costs associated with construction labor are such a large part of any SCR Project, it is a good way to ensure the risks are addressed.
Project Specifics Figure 8 is a reference engineer-procure-construct (EPC) SCR Construction retrofit project spanning 26 weeks. The entire project was fast-tracked for completion in 9 months. The accelerated schedule required that all engineering, procurement and fabrication activities support the erection plan; it was imperative that all aspects of the effort be designed ultimately for constructability. The curves presented show actual productivity from the job. While specific man-hour data is not shown, we shall refer to this reference project as requiring “X” number of man-hours. While the productivity varied from week to week, the trend was upward, indicating the benefit of a learning curve. A productivity goal of 100 is the ratio of earned man-hours for the week vs. actual man-hours spent. Productivity measures of greater than 100 indicate that fewer man-hours are expended to earn a percentage of the job. As tracked on the job, the total man-hours spent for the week are divided into the hours earned. The average labor productivity for this project ended up at 119, indicating one of the benefits of constructability planning. Assuming a fantasy budget of $5M for the labor portion of this project, performance at this productivity level would result in a potential labor cost savings of $576,000. Additional potential benefits derived from productive labor can include schedule improvements and the associated indirect cost savings resulting from the shorter durations.
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Figure 9 (2) >600MW coal-fired SCR retrofit; 3.5X MHRS effects of constructability planning on labor performance.
Figure 9 indicates another project that had the benefit of designing for constructability. While considerably larger in scope (two units) than the reference project above, this project was planned well in advance, with the erector having direct influence over major details like module size, configuration, and field splices. These units had barge access as well, so off-site modularization was used. The benefit of all of this effort is shown in the productive performance trend. While also at times erratic, the performance trend was positive. Take note of the major dips in performance. Down time from equipment failure is evident here. The average productivity on this project ended up in the range of about 110. Assuming a factor of about 3.5X on the labor cost from the fantasy example above yields a $17.5M budget. At the actual reported productivity level, a savings of about $1.6M would be realized. Again, this accomplishment is due in large part to designing for constructability. Figure 10 presents yet another project that benefited from constructability planning. This project is perhaps the best evidence of careful planning and execution. It also shows the ultimate goals of constructability planning: predictability and consistency. At no point was the performance erratic; the trend was positive, and better than anticipated. This project also consisted of two retrofit SCRs, and it benefited from learning curves and spanned nearly a year in duration. (Only 36 weeks of performance are included in the graph due to the limited space available). The end result of the productivity on this project was 109. Referring back to the data in the
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Figure 8 >600MW coal-fired SCR retrofit; X MHRS - influence of constructability planning.
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Figure 10 (2) >600MW coal-fired EPC SCR retrofit; 2.5X MHRS - effects of constructability planning on labor performance.
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Figure 11 (2) >600MW coal-fired SCR retrofit; 3.5X MHRS effects of ZERO constructability planning.
fantasy example above, this project relative to that one would be about 2.5X or $12.5M in labor cost. Total savings from the efficient use of labor resources and constructability planning end up in the neighborhood of $1.03M. Figure 11 is the final project example presented. In theory, it had no benefit of constructability planning. This project also consisted of SCR retrofits on two units; however, it was not designed with erection as a consideration. This project is considered representative of the potential downside impacts of failing to design for constructability. A variety of labor productivity issues were absorbed throughout the completion of the project, each of them having adverse impacts on the project financials. The final productivity numbers came in around a 75. Using the fantasy example, the base labor cost for this job would be about 3.5X or $17.5M. The poor productivity performance would indicate an overrun of labor cost and translate into an additional $5.9M over and above the allowance. This is why labor is so critical to these projects. There exists a need to get consistent, predictable results to ensure completion of these important projects without harming the companies involved. Designing for constructability is one avenue toward these predictable results.
Conclusions Steps are being taken by responsible owners, contractors and labor organizations to ensure an adequate supply of labor is available to meet the anticipated demand. On the supply side, labor
Figure 12
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has stepped up its efforts to recruit, train and retain new apprentices. Pension rules have been revised to permit retirees to return to work for a limited period without penalty. Temporary solutions to labor availability issues include offering travel and subsistence or scheduling the project for extended work hours (overtime) to attract prospective workers to projects. Attracting qualified labor to projects paying 90% wages under the NMA is difficult especially when 100% wages can be earned elsewhere. Steps must be taken to attract quality labor to a project and into the trade itself. Failure to attract qualified labor to a job can be risky, both in financial and compliance terms. Faced with the risk of not being able to attract qualified labor, more and more contractors will likely require commercial language that makes labor availability a force majeure event. The ideal approach is for utilities, contractors and labor to work together to strategically plan the anticipated work and eliminate manpower demands that tax the available resources. Leveling manpower provides a more stable workforce and assists in attracting new recruits into the vocation, not only to the projects. It has the added benefit of helping to reduce the risk of accidents and safety incidents that typically occur with the rapid “ramping up” of manpower on the job. It also permits a learning curve to develop on a project that will lead to productivity improvements and thereby reduce costs. Figure 12 is an example of manpower projections required to complete a significant amount of work over the course of the next few years in a particular region of the country. It is evident that there are manpower peaks during the outage seasons. This graphic evidence is an aid to convince the owner of the value in trying to shift some of the work (like ground assembly of SCR components) into the off-peak season and level the manpower requirements over the duration of the projects. If the nature of the availability problem is understood by all parties (owners, engineers and constructors) there may exist some opportunities to exploit. This could include expediting some elements of the engineering effort to support non-outage, productive work. If the owner has some latitude regarding outage order, outage time or outage duration, the work can be sequenced to take advantage of some of this latitude. Perhaps an SCR tie-in outage to install a by-pass system can be accomplished prior to the construction of the SCR. This would make sense if there exists an extended outage prior to the planned completion of the SCR. This would eliminate the need for an additional extended outage in the near future to accommodate the tie-in. All of these focused efforts can reduce the peak manpower required and ease the burden of labor availability.
Project manpower projections.
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The limited availability of skilled labor (as well as near full employment in the industry), in conjunction with the significant cost of the heavy equipment required for these large capital projects, requires logistics planning in this industry like at no point in recent history. A successful project is measured not only by cost, but also by timely completion. Since these valuable resources represent both the greatest risk and greatest opportunity for any SCR project, designing for constructability should be of significant priority.
Acknowledgments Information relating to Boilermaker Statistics compiled from data provided by the National Association of Construction Boilermaker Employers.
Copyright © 2001 by The Babcock & Wilcox Company, a McDermott company. All rights reserved. No part of this work may be published, translated or reproduced in any form or by any means, or incorporated into any information retrieval system, without the written permission of the copyright holder. Permission requests should be addressed to: Market Communications, The Babcock & Wilcox Company, P.O. Box 351, Barberton, Ohio, U.S.A. 44203-0351. Disclaimer Although the information presented in this work is believed to be reliable, this work is published with the understanding that The Babcock & Wilcox Company and the authors are supplying general information and are not attempting to render or provide engineering or professional services. Neither The Babcock & Wilcox Company nor any of its employees make any warranty, guarantee, or representation, whether expressed or implied, with respect to the accuracy, completeness or usefulness of any information, product, process or apparatus discussed in this work; and neither The Babcock & Wilcox Company nor any of its employees shall be liable for any losses or damages with respect to or resulting from the use of, or the inability to use, any information, product, process or apparatus discussed in this work.
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