J.A. Hines

Babcock & Wilcox Construction Company

Mt. Holly, New Jersey, U.S.A.

A. Kokkinos

The Babcock & Wilcox Company

Barberton, Ohio, U.S.A.

	

		

BR-1725

D.S. Fedock

Babcock & Wilcox Construction Company

Barberton, Ohio, U.S.A.

Presented to:

POWER-GEN International 2001

December 11-13, 2001

Las Vegas, Nevada, U.S.A.

	

In years past, the term constructability was generally associated with the quality of engineering outputs. Specifically, it was

in reference to issues that could potentially preclude a component

from being satisfactorily built or inspected, including errors,

omissions, and to subjective notes or information requiring individuals to make assumptions about the Engineers’ intent. Information that lacked clarity was typically resolved through various

vehicles, including drawing revisions, requests for information,

engineering memoranda and nonconformance reports. Resolution almost always led to rework or at least some delay while

awaiting the Engineers’ disposition. The result was increased

cost. Recognizing this, and as a response, many long-term projects

implemented constructability reviews of design outputs prior to

issuance to preclude delays during construction. Therefore, from

its beginnings, constructability has always been an issue of worker

productivity.

Most projects are not so long-term and can ill afford to repeat

those lessons that should have previously been learned. As it is

defined today, constructability encompasses a wide variety of

practices that when incorporated into a project can improve productivity and, in most cases, reduce costs or project risks. Given

the recent trends in the availability of skilled labor to execute an

SCR project, issues relating to productivity take on even greater

importance.

Recognizing that construction costs for SCR projects can exceed 50% of total project costs, and given that labor and equipment are significant cost components, it is prudent to design in a

fashion that ensures the maximum efficiency of these valuable

resources.

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. Integrating the construction plan into the engineering process can improve the outcome. Once that is accomplished, the engineers can assess implications of changes or deviations from the plan. The goal of designing for constructability seeks to minimize impacts and improve productivity through the elimination of rework and/or corrective work, improve material deliveries, and incorporate some

type of modularization.

Constructability includes the design of “user friendly” connections between adjacent components. It involves to the extent

possible up-front determination of splice locations and module

limits that establish the erection plan. Designing for

constructability means letting the construction plan drive the

project execution, including engineering, procurement and delivery efforts. To be most effective, the construction plan should be

fully integrated into the overall project schedule, complete with

ties to engineering, procurement and delivery activities.

The payoff requires some vision. It is most evident during

construction, after the engineering and procurement efforts are

essentially complete and when, typically, no float remains in the

schedule. But it is at this point where a little float could go a long
 	


  



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way, especially when the project costs can reach $100,000 per

day during peak construction activities. In many instances, float

has been relinquished to engineering and procurement efforts

where there is little payback or cost for a day’s delay. The real

savings and benefits lie in the reliability and predictability it provides the construction plan through 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 to

exercise maximum influence over those that offer the biggest

payback. The goal of constructability then is to minimize project

risk (labor availability) while maximizing opportunities (through

productivity improvements).




The demands for construction labor and declining workforce

have created potential labor availability problems across the country. 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.

	


This figure indicates the recent decline in active membership

in the boilermaker ranks. A variety of factors were responsible

for the decline, including uncertainty in the utility labor market

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. The rate of

attrition through retirement actually outpaced the number of new

apprentices added to the work rosters, a consequence of which

has been the trend toward an aging skilled labor force.





Complicating matters has been the increased demand for construction services. There are many factors driving this increased

demand, including new owners investing in recently acquired

assets, low NOx burner retrofits, SCR installations, new power

plant construction (primarily combustion turbine projects), and

ongoing routine maintenance at operating facilities. However,

the demand for skilled labor is not limited to the Utility industry.

See Figure 2.

Projections of the demand for construction labor (specifically

Boilermakers) looking outward to calendar year 2004 are provided in Figure 3.





These projections show 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. But note, these are composite

figures and represent the total active membership.
	
 

Of perhaps greater significance is the breakdown of the data

presented in Figure 4 by geographic region to get a better look at

what has occurred at the local or regional level.

Figure 5 presents this geographic data on Boilermaker Utilization for the first six months of calendar year 2001.

There is tremendous competition for these labor resources,

not only between contractors who employ labor, but also between project owners and developers aggressively trying to complete projects in a narrow window of opportunity.


			

		

Each project presents a unique set of circumstances, due to the

plant’s geographic location, available real estate, laydown area

and interferences (both above and below grade), and project timetable issues. Since most of these projects are retrofits, a site

typically has limited access, with many interferences and obstructions. Therefore, Engineering and Construction will ideally

work closely during the design phase. To be most effective,

constructability should begin early by recognizing the magnitude

of the job. Because a typical SCR project can require the installation of 500 or more cubic yards of concrete, hundreds of piles,

thousands of tons of structural steel and platework, and miles of

cable and raceway, planning is essential. Input from the erector is

a key step toward transitioning from the design phase to construction. A comprehensive construction plan with its intended

rigging scheme is critical to a project’s success.



Once a general arrangement for the project is available, it can

be utilized for constructability planning. If the site location has

barge access or unloading facilities, off-site modularization should

be considered. If barge access is not available, chances are onsite modularization of sub-assembled components will be required. Once a crane location is spotted, actual selection and

sizing can be accomplished.

To select the appropriate crane, the limiting component of the

rigging scheme must be determined. Do the site conditions limit

the crane size? If so, the largest module (or assembly) to be

fabricated or ground-assembled will be limited by the crane’s

available hook capacity. If adequate space is available and crane

size is not an issue, a determination needs to be made about the

optimal or largest module to be erected. Often, the limiting component may be a reactor support plate girder, and not a particular

section of fluework.

Each project must be evaluated individually, as there are a

number of issues to be considered in determining the extent to

which a crane can be used. Each project is different.

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 project is not the one with

the greatest capacity (and cost). 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. Peace of mind can come at great cost. And, depending upon the arrangement, two of these large cranes may be required. For large projects posing unique or complicated arrangements, crane costs alone can exceed $250,000 per month.

When projected over the duration of the project, the cost can

be several million dollars. The project timetable should be

carefully considered.



Many times, early in the project, specific information about

weights cannot be accurately ascertained due to the preliminary

nature of available information. This is a risk early on, but sound

judgements can be made based upon the erector’s experience.

Module identification will set the boundaries for assembly. Ideally, the erector determines which splice locations are best from a

variety of standpoints, including access, crane capacity and geometry. Once the sub-assemblies are identified, the sequence

should be detailed on a drawing and work can proceed to schedule erection activities. This Erection Sequence Drawing can be

distributed to the project team, including sub-contractors, to ensure the intended plan is understood by all.

Refer to Figure 6 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 sufficiently in

advance of the time required at the job or out of order only adds

costs and burdens the job with additional material handling costs.

It may also force the job to work on activities that deviate from

the intended plan. The most efficient projects will not deviate

significantly from the construction plan.


		


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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 such as missing or incorrect information. If

left unchecked, these 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 at this time can pay back many times over.

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Once modules are identified and an erection sequence is established, the erector can work with the platework vendor and

  



 
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influence delivery. This lets the erector review and comment on

the shop’s plan for panelization.

The benefits are two-fold. First, it provides the erector with

valuable information and knowledge about the material to be received, including the extent of work required onsite to pre-assemble modules. Second, it 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.

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Flues should be bottom-supported where possible, and ideally the identified modules will be self-supporting (even if this

requires adding 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, or until the piece is safely lashed off.

For the cranes and boom geometry typically required on these

projects, winds in excess of 25 mph will shut down crane operations. This can limit the window of opportunity for rigging components into place.




For the same reason, the use of fit-up bolts between adjacent

panels or modules can help improve productivity and limit adverse effects associated with weather and wind. Reactor internal

support steel can also be designed with end connections that

allow quick removal from the crane hook to free it up for productive work elsewhere.

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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. 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 a good

portion of the welding for these projects typically 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 and adversely affect worker productivity.

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Assembly generally requires a significant amount of scaffolding. A good construction plan will identify those modules that

require scaffolding to access welding locations. In most cases,

scaffold brackets or fixtures can be installed on ground prior to

lifting to save costly scaffolding labor.

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It is also important to know the material type of any fluework

being demolished. This may alter the demolition plan. Some materials suffer from temper 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 to recognize that there can be issues relating to

the installed materials.

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During receipt inspection of galvanized structural steel, many

disparities may exist in color, texture and overall appearance,

even on the same member, resulting from the process or size of

the vats used for galvanizing. While this may be cause for concern upon initial receipt inspection, it is important to keep in mind

that these disparities may not indicate a problem. The primary

function of the galvanized coating is corrosion protection. Variations in the coating appearance are important only to the extent

that they impact the corrosion performance.

Also, on large galvanized beams or sections (web thickness

over 1⁄4 in.), high stress regions are prone to cracking, especially

in the area of a cope or cut out. This cracking is not evident until

after, or it is exacerbated by, the galvanizing process. While the

debate continues as to the cause of this cracking, steps can be

taken to preclude the occurrence of the cracks. One might be

welding a temper bead in the coped area prior to making the cut.

Non-destructive examination may be required to ensure cracks

are not present and the temper bead worked.


*

Some projects consider the use of insulated packed panels

versus a more conventional insulation and lagging system. The

goals here are to minimize onsite labor, and perhaps take advantage of the lower labor rates and greater quality control in a shop

environment. While these savings are real and can be achieved,

caution is appropriate in this approach, especially if there is a

concern for the quality of the onsite labor or subcontractor selected for installation.

Packed panels need to be stored properly and once installed, a

poorly executed panel job can hide defective workmanship. If

site access lends itself to barge shipment or modularization, an

alternate approach might be to shop-install insulation and lagging

on key areas or modules prior to erection. In this approach, minimizing scaffold requirements might lead to cost savings.

In a related issue, caution should be exercised if the plan is to

start the unit up prior to completely insulating the flues. The

temperatures involved can lead to thermal distortion and perhaps

thermal cracking, which could then lead to repairs and taking the

unit off line to accomplish the work.



*


Caution should be used when establishing cut lines from inline

components such as damper flanges or expansion joint locations.

When the cut line location is critical, such as the location of the

new tie-in point, dimensions and locations should be verified

from a more reliable source, such as a column line or other structural steel. The structural steel column grid may prove to be more

accurate than some inline component that may have been installed

under some previous modification. Even if the cut line is dimensioned from an inline component, it should be verified from another source or reference point.


+

Early in the project, consideration should be given to the turnover package requirements in support of commissioning or

startup. Many times these issues are customer-driven, and customers differ in their requirements. Also, depending on the project

team composition, responsibilities for startup and commissioning may vary. If the turnover requirements or system release
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requirements are known up front, then a system for filing, compiling and preparing vendor and construction documents and data

can be set up to provide a more fluid turnover.

	


		 	

Several Babcock & Wilcox Construction Company projects

have had the opportunity to benefit from the effects of designing

for constructability and resulting productivity improvements. The

next few paragraphs will present some backup data from a few of

these projects.

Figure 7 is a reference EPC SCR Construction retrofit spanning 26 weeks. The entire project was fast-tracked for completion in nine 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 ultimatelyfor constructability. The curves presented show

actual Babcock & Wilcox Construction Company productivity

for the job.

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, or output per unit of effort. Productivity measures of greater than 100 indicate that fewer man-hours

are expended to earn a given percentage of the job. The average

labor productivity for this project ended up at 119, indicating one

of the benefits of the constructability planning. Performance at















           

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this productivity level would result in a direct labor cost savings.

Additional potential benefits derived from productive direct labor can include schedule improvements and the associated indirect cost savings resulting from the shorter durations.

Figure 8 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 utilized.

The benefit of all of this effort is shown in the trend of productive performance. While also at times erratic, the 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. At the actual

reported productivity level, a labor cost savings would be realized. Again, this accomplishment is due in large part to the effort

to design with constructability in mind.

Figure 9 presents yet another project that benefited from

constructability planning. This project is perhaps the best evidence of careful planning and execution.

It shows also the ultimate goals of constructability planning:

predictability and consistency. At no point was the performance

erratic, but the trend positive, and also 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 contained here due to the limited space available). The

productivity at the end result of this project was 109, also

indicating a labor cost savings.

Figure 10 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 represents 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 having adverse impacts on the project

financials. The final productivity numbers came in around 75.

The poor productivity performance would indicate an overrun of direct labor cost. This is why labor is so critical to

these projects. There exists a need to get consistent predictable results to avoid the risks associated with poor labor productivity. Designing with constructability in mind is one avenue toward achieving these predictable results.

Constructability refers not only to the ability to construct or

the quality of the engineering outputs. It is more a model or

philosophy for successful project execution. This approach recognizes that the true measure of success on a project lies not only

in on-time completion within budgetary constraints, but in constructing productively, maximizing the efficiency of the available

human and equipment resources, and perhaps saving money.

The limited availability of skilled labor combined with near

full employment in the industry, and the significant cost of the

heavy equipment required for these large capital projects, requires owners, engineers and constructors to work together to

develop comprehensive execution plans. Since these valuable resources represent both the greatest risk and greatest opportunity

for any SCR project, designing for constructability should be of

significant priority.

Information relating to Boilermaker Statistics was compiled

from data provided by the National Association of Construction Boilermaker Employers.