7 Obvious Reasons to Use Wood Distribution and Transmission Structures

Posted by Brooke Brackett on Aug 27, 2014 11:17:47 AM

While many say “Out with the old and in with the new,” this might be true for hairstyles, tube socks or shag carpet, but with over 130 million wood utility structures across America that are still in service today, this is simply not the case.

Wood utility structures have an undeniable reputation for being reliable, versatile and cost-effective.Wood distribution and transmission structures remain highly preferred in the utility industry due to their ease of construction, climbability and design flexibility.

Wood Transmission Structures

Reliability Wood transmission structures have higher Basic Insulating Levels (BIL), which can help reduce lightning flashovers, cutting down on power outages.

Cost-effective With economical initial costs and low overall life cycle costs, wood can directly reduce the impact of operating expenses.

Safety Since wood transmission structures have been around for decades, utilities and lineman are very familiar with proper use and handling of the products.

Why use wood transmission structures?

  1. Lower cost
  2. Long and proven service life
  3. Adaptable to many different applications
  4. Easy to handle and store the structures
  5. Natural flexibility providing  high performance under load
  6. Can be easily modified in the field
  7. Can be supplied quickly in times of crisis

trans pic green

The general standards that wood transmission structures must meet include ANSI, RUS, NESC, WCLIB and AWPA. And just like steel, concrete and other materials, there are countless configurations for wood transmission structures. 

Just to name a few, there are:

  • Single Pole with Traditional Crossarms
  • Wishbone Structures
  • Two Pole H-Frame Structures
  • Multi-Pole H-Frame Structures

trans 2 green

When considering which manufacturer to choose, you might want to consider their history in the supply of products in the utility market, the location and number of facilities, in-house design capacity, access to raw materials and available inventory for standard items, especially when time is critical. All of these factors could make or break your recovery response when natural disasters strike.

 

Read More

Topics: utility industry, wood distribution crossarms, wood crossarms, utilities, transmission, wood crossarm, wood transmission structures, wishbone structures, H-Frame structures, wood structures

VIDEO: Manipulating Loads for Steel Transmission Pole Design

Posted by Brooke Brackett on Aug 18, 2014 1:50:00 PM

Check out our first DIS-TRAN Take2 where Bill Elliott, senior civil engineer at DIS-TRAN Steel, demonstrates in under four minutes how to transpose loads from the wire coordinate system into the structure coordinate system, while also pointing out one common mistake to avoid.

Terms you'll hear:

  • Longitudinal component
  • Transverse component
  • Longitudinal axis
  • Transverse axis
  • Vectors
  • Wire coordinate system
  • Structure coordinate system 

 

 

Subscribe_Pic

 

Read More

Proper Draining and Venting Provisions for Steel Structures

Posted by Brooke Brackett on Aug 7, 2014 1:33:00 PM

Something that might be viewed as a small, insignificant venting hole on a 10,000 pound steel structure, if not well thought out, could really have an adverse effect on production.

These mistakes, big or small, can delay or even put a halt to jobs. It’s key that all along the process, from engineering to detailing and quality control, there are people in place who know what to look for. Once the structure gets delivered to the galvanizer it can become difficult and more costly to make modifications because plates might already be cut, or everything might be welded up.

When creating fabrication drawings for galvanized structures, it’s important, as well as valuable, to know proper draining and venting provisions for these steel structures. If adequate venting and draining holes are not provided, the structures can run into many problems.

5 Negative Effects:

1. Air pockets can form, causing structures to rust out from the inside

2. Excess galvanizing buildup

3. Lead to longer fabrication times

4. Welded plate can blow out, causing safety concerns

5. Poor coating

Not having adequate venting and draining holes can really have an intangible effect: it’s hard to put a dollar amount on what happens when a structure either doesn’t have proper venting, or one of the five stated above occurs. It’s usually not too hard to correct if it’s caught up front, but the further it gets in the process, and closer to the delivery date, is when the scrambling might start. All the man hours it takes to call the engineer on record to approve revisions, or contact customers, plant personnel, the galvanizer, etc. can really put a stop to production, causing low production numbers and possibly delayed shipping. (But working with a trusted steel fabricator, can help to avoid these issues.)

excess galvanizing buildup

Some standard shape structures, such as square and rectangular tube columns and beams, are hollow, so provisions need to be made in order to allow galvanizing to easily flow and coat the inside portion of the structure. Sometimes fabricators will provide a small bar with a removable cover plate, attached with two (2) small stainless steel self-drilling screws. However, if the customer doesn’t feel this is sufficient enough, then the next suggestion could be to use a thicker bar with drill and tap holes, and two (2) A307-TAP bolts.  Some might suggest the use of expanded metal, but excessive build up can take place, which is unsightly and also impairs vision into the tube, hindering the Quality Control Department from being able to adequately determine if interior galvanizing coating is sufficient.

Other standard shape structures like channels, wide flanges and angles, are solid, with just the outside receiving coating. Some issues that can arise with this are air pockets and excessive galvanizing buildup. For these shapes, you need to watch where stiffeners, connection plates and brackets are welded that could form large pockets of air as the section is dipped into the kettle. Tapered tubular structures are also hollow like square and rectangle tubes.

As a designer, you are always trying to find the balance of putting enough holes for galvanizing while not putting too many to affect the structural integrity of the steel member. For example, if dealing with corners in a square and rectangular tube, slots or holes can be provided near these corners to prevent air pockets from forming, which can decrease the amount of galvanizing coating in the area.

The more you understand how the member is lifted and dipped in and out of the galvanizing kettle, the better you can locate the venting and draining provisions.

For more information about galvanizing and how it works, click here to read past articles.

  

Read More

Topics: standard shape steel structures, galvanized steel, steel fabricator, galvanized structural steel, rectangular steel tube, steel square tube

Increased Thickness Doesn't Always Give Enough Deflection in Steel Pole

Posted by Brooke Brackett on Jul 31, 2014 1:27:30 PM

 

In marketing, catchy titles and inspiring phrases are my forte. However, when it comes to numbers, let’s just say I rely heavily on my calculator app. But with civil engineers, numbers are their friends. There’s this “numbers game”, if you will, that they play daily. When designing steel structures, engineers first develop the loads and then apply the loads in their design. Once loads are applied, they are tasked with finding the best possible combination of steel members and connection types while paying special attention to section properties, weights, aesthetics, constructability, etc. 

Pretty straight forward, right? Well not exactly. There are two major things that the engineer must consider: first, make sure the structure doesn’t over deflect, and second, make sure it doesn’t over stress. If the steel structure experiences over deflection, especially in a substation, this could potentially damage the equipment that are mounted on the structure. If the structure over stresses, it could cause things like yielding, cracking or even falling down.

It’s important to take all possible loading scenarios into account, such as combined ice and wind loads, extreme wind loads, earthquake loads or wind-induced oscillations, and apply them to ensure the structures stay within their set limits required by code, contract documents, customer specifications, etc. These structures can consist of an assortment of pipe, channels, wide flanges, square tubes, or even custom shapes like tapered tubular poly members. 

While it’s important to find the best possible combination of section properties, an engineer should also always be looking at the most economical choice when designing the structure for the customer. Steel fabricators can design structures from standard shape steel, all the way to tapered tubular steel, so it’s important that the engineer takes a good look at the entire picture, because remember, at times there is a direct correlation between heavier steel and higher costs. This is where the numbers game comes into play.

So, let’s say an engineer is designing a basic shape like a square tube, also known as hollow structural sections, they might start out with HSS 6x6x3/16 and keep increasing the thickness, which immediately helps with the stress but doesn’t help as much with deflection. At this point they need to start paying attention to the section properties by finding the best possible combination between things like the I Value (moment of inertia) and the S Value (section modules) while watching for overall member weight. So while the tube itself is smaller, the walls are getting thicker, making the structure weigh more.

The example below shows that moving up to the larger size, HSS 8x8x3/16, gives a significant increase in the I Value, which helps deflection, while also giving a slight increase in the S Value, which helps the overall stress, as compared to the HSS 6x6x3/8. In doing this, there is a 38 percent increase in the section modules, while at the same time a 28 percent decrease in weight. So going with a smaller member doesn’t always give you more bang for your buck.

HSS 6x6x3/8

                wt = 27.41 lb/ft

                I = 39.5 in4 (deflection)

                S = 13.2 in4 (stress)

 

HSS 8x8x3/16

                wt = 19.61 lb/ft

                I = 54.4 in4 (deflection)

                S = 13.6 in3 (stress)

 

Structure Classifications & Deflection Limitations, Design Guide per ASCE 113

In substation design, there are three different structure classifications: Class A Structures, Class B Structures and Class C Structures.  This is slightly different the old NEMA SG 6 that just had the substation structures broken out into only two classes: Class A and Class B. With ASCE 113, for determining the maximum deflections, they are broken down by horizontal members and vertical members. Horizontal Members are where the span of a horizontal member is the clear distance between connections to vertical supporting members, or for the cantilever members, the distance from the point of investigation to the vertical supporting member. To determine the maximum deflections, the span of a Vertical Member is the vertical distance from the foundation support to the point of investigation on the structure. The deflection to be limited is the gross horizontal displacement of the member relative to the foundation support.

Deflection_Limitations_Chart

As an experienced engineer, they understand that all structures should be designed to withstand applicable loads from things like wind, ice, line tensions, electrical equipment or other unusual service conditions when providing reliable structures for substation and transmission projects. Make sure to subscribe to the DIS-TRAN Blog today in order to receive next week’s article on loading criteria for substation structures.

 

 

Read More

Topics: Deflection

Industry Standard Pre-Engineered Steel Pole Compared to RUS Requirements

Posted by Brooke Brackett on Jul 17, 2014 8:46:00 AM

Previously called Wood Pole Equivalents, Pre-Engineered Steel Poles are classified by the ground line moment that they can withstand. Using pre-engineered steel poles can be a practical way to minimize cost and time on certain projects. Generally, pre-engineered steel poles are used for distribution type projects rather than transmission lines due to the shorter spans and lower tensions used on distribution lines.

Pre-engineered steel pole design and classification follow a similar philosophy to that found in ANSI 05.1-2002 for wood poles. Per ANSI O5.1-2002, wood pole classifications can be determined by placing a horizontal tip load two feet from the top of the structure and determining the corresponding ground line moment. Pre-engineered steel poles are similarly designed and classified by applying an equivalent horizontal tip load two feet from the top of the structure. The equivalent horizontal tip load is found by multiplying the horizontal tip load found in ANSI 05.1-2002 by the ratio of factors of safety of steel to wood.

Many manufacturers have developed Pre-Engineered Steel Pole Catalogs for line designers to utilize when designing structures.  These catalogs normally include structural characteristics, weights and maximum ground line moments.  Most Pre-Engineered Steel Pole Catalogs take into account some industry wide assumptions as follows:

  1. Embedment depth is taken as 10% of the height plus two feet.
  2. Heights for pre-engineered steel pole catalogs range from 45-120 ft.
  3. Catalogs include Class 3 thru H10. Noting that Classes 1 thru 3 are typically not economical to fabricate using steel unless a round section can be utilized.
  4. Typically the same top diameter and taper are used per class.
  5. No deflection criterion is used.

Using pre-engineered steel poles may be a good option for a project if the owner and/or line designer is confident with the approximate ground line moment calculation on simple line designs or if the line designer is plugging in the structural properties of a pre-engineered steel pole from a catalog into a line design software.  Using pre-engineered steel poles can help give a good idea of the pole sizes the owner and/or line designer will need. This method of design is generally used for single pole structures that are subject to transverse and vertical loads. Engineering judgment must be carefully exercised when using pre-engineered steel poles in applications that can cause forces to be redistributed along the pole length. Also to keep in mind, the owner and/or line designer is typically responsible for determining the applicable loads and loading criteria, geometric configuration, type and degree of structural support, as well as any other required design or performance characteristics for pre-engineered steel poles.

One requirement to look for when considering using pre-engineered steel poles for a project is adherence to the Rural Utilities Service (RUS) Bulletin 1724E-214. If a project is required to adhere to the RUS Bulletin, there may be some deviations from the standard pre-engineered pole industry standards/catalogs to consider. Some of the deviations include the following:

  • Point of Fixity
  • Tip Load
  • Class Designations
  • Deflection 

The table below summarizes some of the differences that may be found between the RUS Bulletin and most Standard Pre-Engineered Steel Pole Catalogs. 

Deviation_Table_

*Class Designations may vary depending on manufacturer. 

 

Using pre-engineered steel poles in line design can be an effective way to minimize cost and time associated with a project. It’s important to note that there may be deviations between a standard Pre-Engineered Steel Pole Catalog and the requirements of certain specifications, and it is ultimately the line designer’s responsibility to review all applicable specifications, pole configurations and loadings to ensure that a pre-engineered steel pole is the right choice for a structure.  

*Content provided by Callie Lohman, PE, Civil Engineer at DIS-TRAN Steel, LLC. 

 

Read More

Headaches Customers and Steel Fabricators Run Into with Production Backlogs

Posted by Brooke Brackett on Jul 9, 2014 10:00:00 AM

We all appreciate on-time delivery. Whether it’s ensuring your new G. Loomis fishing rod is in before your next tournament or Amazon delivering your new sandals before you head to Florida; we all depend on the supplier. 

It’s critical that the supplier is organized, flexible and has an updated production backlog to make sure delivery is as promised, and not late because they have over-committed themselves.

A backlog is the total production that remains to be completed at any given time.  It may also include some tentative work that you are fairly sure you will be awarded, although you may not have an official purchase order yet.   The sold production is prioritized into a production schedule over the coming months depending on size and the promised delivery date. 

detailer

The backlog is important to all of the departments within an organization, all the way from estimating, to engineering/detailing, production, etc., so that each promised job has its required amount of resources available and scheduled before the fabricator promises any additional deliveries. It must be updated constantly as new jobs are won.  Any company who prides itself on customer service and on-time delivery must have a defined backlog that is current and that has been set to achieve 100 percent of promised commitments.

The backlog allows the estimating department to know exactly how much and where any capacity is available in any given month so that they can make their next commitment to a customer on the next project they are bidding on.   It will show any “holes” in the schedule where something may be worked in.  It will also show “premium hours,” such as weekends, that may be available for customers who have a project that requires an expedited schedule where overtime fees are acceptable to meet the required delivery date.

But as easy as filling a backlog might seem from the outside, it can get a little difficult and sometimes frustrating to the customer and fabricator.

Problem #1: If a customer knows that there is a specific size project coming up for them in the future and roughly when they will need it by, but say the market is so busy, that their chances of getting their project by the desired time is slim once the details are finalized. 

Solution: Fabricators can hold production space for customers based on a rough idea of the project scope and often without an exact purchase order for particular projects. If the customer knows when they need it delivered by and can estimate the scope of the project, then the fabricator will bid other projects around it as if the project remains on track.  This is beneficial to both the supplier and the customer. However, if the project schedule changes, this results in challenges for the supplier due to backlog holes.

Problem #2: Backlog holes can sometimes be one of the more frustrating aspects of managing a production backlog.  Holes in production can come from many sources, such as slow bookings, project slipping or approval hold-ups.  A backlog hole is a period when there is not sufficient work scheduled to meet the facilities capabilities. This results in lost revenue for the facility and lost productivity. 

Solution: From a customer’s prospective, this can be beneficial because if their project “needs” fit the supplier’s “wants” they could get their project at a really good price, a really good schedule or both! Make sure to always stay in contact with the supplier’s estimating department because opportunities like this might arise that work for both.

Problem #3: Often during the normal course of a project, various issues can cause the project schedule to slip.  When this happens the project now moves out into the next future open spot in the schedule.  If the backlog schedule behind the slipped project is full, the next available production spot could be several weeks out.  Often, as a customer, it can be hard to understand how only a week delay in the project schedule can result in a month or longer delay in production. But it’s similar to getting out of line for an amusement park ride and then coming back to find the line has taken your spot and now you have to get behind everyone else.  The issue for the fabricator is that the schedule slip could result in an open backlog hole that is unable to be filled, resulting in productivity loss. 

Solution: These cases don’t necessarily happen all the time, but when they do, they can be frustrating for both parties. Frequent open communication between the customer and supplier often goes a long way in alleviating this issue. Strong relationships between the customer and supplier or having an Alliance Partnership definitely doesn’t hurt in times like these, but other solutions like expediting can be arranged. The fabricator can bring in extra crews, work overtime, expedite shipping-anything to help ease the pain of this problem. (Expediting fees might be included though.)

Problem #4: Typical suspects for project scope change are engineering changes or customer revisions, which result in either an increase or decrease in project scope.  When changes become significant, the backlog schedule is impacted either by the production slot being overfilled (for increases in scope) or under filled (for decreases in scope).  The overfilled production slots often result in split deliveries, with some material delivered on the original schedule and the balance delivered at a later time based on the remaining backlog.  If the scope of the project is reduced and the supplier is unable to fill the resulting backlog hole, there will be a financial impact to the bottom line.

Solution:  By doing strong research, or “homework” on the front end, and not changing the project after it’s been ordered can help alleviate this problem. Staying in constant communication with the fabricator during the quote stage can also help iron out issues before they happen.

Problem #5: Another backlog gremlin is when Murphy ’s Law attacks the project with unforeseen fabrication issues.  Most experienced fabricators are able to negate normal production issues with production buffers and preventive maintenance programs.  However, there are times when either a new product type slows typical productivity, or overly difficult fabrication results in an underestimation of required production backlog time.  Despite the supplier’s best intentions, these issues do occur at times.   

Solution: Make sure that the fabricator has adequate capacity and experiencein the industry. Plant tours, sales visits or even just phone calls and emails exchanged can help build relationships and trust.  Developing a relationship with a fabricator who will be open about any fabrication issues can go a long way to ease any construction scheduling delays as well.

The good news is that often most of these backlog issues can be remedied by upfront and direct communication between the customer and the supplier.  With adequate notice, suppliers are usually able to adjust backlogs to suit project delays or scope changes.

  

problem_CTA

Read More

Bet You Didn't Know This About the Fourth of July

Posted by Brooke Brackett on Jul 1, 2014 10:41:50 AM

Fourth of July is no joke here in the United States: we take this holiday serious. Now whether that is because of the smell of BBQ cooking, the incredible firework shows, cold beer or the fact that we get to experience all of the above on a paid holiday, that’s up to you to decide, but either way, it’s one of the most patriotic holidays celebrated in the United States.

But before sparklers, yankee doodle-dandy or town fairs were associated with this day, a committee of five men, including Thomas Jefferson, wrote a statement explaining what the resolution of independence was, called the Declaration of Independence, which declared independence from Great Britain in 1776.

4julypic

Pictured on top from left to right are: Jennifer Smith, DT Alliance Coordinator and Shea Rax, DT Steel Drafter. Bottom row includes: Jackie Spain, Technical Service Assist., Brooke Brackett, Marketing Cooridnator and Desiree Hunter, Steel Drafter. 

Although we celebrate our independence from Great Britain on this day, July 4th, the United States was not technically independent yet when the Declaration of Independence was first adopted. When the 13 colonies first settled, they were allowed to develop freely without much interference from Great Britain, but that changed in 1763 when Britain decided to start taking more control over the colonies. Ever heard the phrase “no taxation without representation”?

This saying was derived when Britain decided that the colonies needed to return revenue to the “mother country” and pay for the colonies’ defense. However, the colonies did not agree since they were not being represented in Parliament, and considered it to be tyranny: no taxation without representation.

After Britain continued to tax, the colonies formed the First Continental Congress in order to persuade Britain to recognize their rights. Well, we know how this turned out: they said no and the American Revolution began. After things started to heat up, John Adams, Samuel Adams, Ben Franklin and others called Sons of Liberty, decided that it was time to unite the colonies to stand together against the British government.

During the American Revolution, a second Congenital Congress was formed and it was then that they adopted the final draft of the Declaration of Independence. All 13 colonies stood behind this declaration, which was approved on July 4, 1776. Although we declared independence, the American Revolution was still being fought, which meant the US was not independent just yet. But after the war ended in 1783, the fourth of July became a highly celebrated holiday in the US.

We often get wrapped up more in the “celebrating” rather than actually remembering why. It’s important that, as a country, we all know and understand our history. The section below is an excerpt from the second paragraph of the Declaration of Independence.  

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.--That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn, that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security.

The Declaration of Independence serves as a reminder to not lose sight of what our forefathers learned, documented and handed down to generations in the hopes that we don’t make the same mistakes again. History isn’t just a class in school, but real life accounts.  

So to make learning a little more interesting, let’s play a quick game of true or false to test your knowledge.

1. Both John Adams and Thomas Jefferson, the only signers of the Declaration of Independence later to serve as Presidents of the United States, died on the same day: July 4, 1826.

True. They both died on the 50th anniversary of the Declaration of Independence.

2. In 1870, the US Congress made Independence Day a paid holiday for federal employees.

False. In 1870 it was declared an unpaid holiday, but then changed to a paid holiday in 1938.

3. Fifty-nine places in the US contain the word “liberty” in the name.

True. Four are counties; Liberty County, Ga, Liberty County, Fla., Liberty County, Mont. And Liberty County, Tex.

4. There were a total of 46 signers to the Declaration of Independence.

False. There were 56.

5. The term “John Hancock,” a synonym for signature, was originated because John Hancock, President of the Second Continental Congress, was the first signer.

True and False. He was the first signer and the synonym was derived from his name, however this came about because his signature was so large that it is still one of the largest and most famous signatures in history.

 4th_July_CTA

Read More

How To Slip Joint Fit Up on Hermetically Sealed Steel Poles

Posted by Brooke Brackett on Jun 24, 2014 10:30:00 AM

When preparing specifications for weathering steel transmission pole projects, utilities will often require that the poles be hermetically sealed.  This means that the inside of the poles are sealed from the outside environment through welding.  The rationale behind this requirement is easy to see.  Weathering steel requires a number of wet/dry cycles in order to form the protective oxide coating that prevents further corrosion.  If water is allowed to rest against a weathering steel surface, this oxide coating cannot form and corrosion can be a result.  By eliminating water from inside the pole, this corrosion mechanism is eliminated.  The most common method of hermetically sealing steel poles is through the use of sealer plates that the top and bottom of a slip jointed section.

Problem:  Difficult slip joint fit up on hermetically sealed poles

Sealer plates are often used on weathering steel slip jointed poles to provide a barrier against air intrusion.  A sealer plate is placed at the very top of the lower section while a second sealer plate is placed above the point of maximum slip on the upper section.   These sealer plates can significantly stiffen the sections against deformation.  Often, steel pole sections will not be perfectly round when formed.  In order for the two sections to mate together properly, the sections need to conform to each other.  When sealer plates are present, the tubes are stiffened against deformation which can make it difficult to achieve the proper slip length.

sealer_plate

Solution:  Eliminate the upper section sealer plate

If the top of a section is sealed against moisture there is no way for moisture to travel up the slip joint.  Furthermore, the air gap between the top and bottom section allows any condensation or other moisture that finds its way inside the tube to drain out the bottom.  Following these recommendations will go a long way towards ensuring proper slip joint fit-up, as well as make the contractor's life easier.

Read More

Topics: slip fit pole assembly procedure

10 Tips: How to Save Money When Submitting a Bid to a Steel Fabricator

Posted by Brooke Brackett on Jun 19, 2014 11:25:00 AM

Every structural steel fabricator is different when it comes down to pricing substation and transmission steel structures. But, there are some commonalities that could help save you money when submitting a Request for Quote (RFQ). How do you do that you might ask?

Well, generally, there’s a rule of thumb to consider: the more information you give the Estimating Department, the better price you’ll receive. If very little information is given, it’s harder for the estimating department/engineers to easily go through and pick out requirements, design the structure and then send the RFQ back in adequate time. And sometimes the price might reflect the assumptions that had to be made. 

Different terms used:

  • Request for Quote (RFQ)
  • Request for Proposal (RFP)
  • Purchase Requisition
  • Inquiry
  • Bid Event / BidQuote / Proposal

DTS_Employee

So, if you’ve asked yourself, “what can I do to save money when submitting a bid,” here are five good starting points.

1. Well-Defined Scope of Work- this could include everything from what the fabricator’s responsibility is, to needing the structures galvanized or weathering, delivery process, how hardware should be shipped, etc.  

2. Technical Specifications- this tells the fabricator how you want the structures built, like what kind of steel to use, etc.

3. Commercial Terms- this is more on the legal side, meaning what type of payment or who to invoice, insurance requirements, warranties, damages, etc.

4. Structure/Electrical Layout- this gives the overall dimensions of a structure such as height and width or phase spacing.

5. Enough Time to Bid- it’s important to keep in mind that fabricators typically have a quote backlog already scheduled out. 

Often, in order to send a bid to a fabricator, customers require the fabricator to be on an approved vendor list in order to quote the project.  The approval process usually involves quality assurance / quality control (QA/QC) audit, industry experience, project references, customer references, commercial term agreement, credit approvals, etc. 

Facts That Could Affect Pricing:

6. Weathering steel generally costs less because unlike galvanized steel, it doesn’t get the galvanized coating. (Typically see weathering steel more with transmission structures.)

7. Usually, the more steel ordered at one time could help give you a better price. In this instance, if you had different structures for one substation, instead of ordering separately, try to coordinate to order all the structures together, which could save money on freight and other expenses.

8. Loads with over-length and over-width sections could get costly because you have to get freight permitting depending on the states along the delivery route. Typically, the price for wider structures is greater than longer structures.

9. Expedited lead times can increase price. Since a production backlog is already in place, fabricators would need to expedite engineering, detailing, rearrange product schedule or may have to include some overtime.

10. Special weld inspection requirements and tests that are beyond typical industry standards could raise the price. If the fabricator needs to pull in a third party to inspect, send material off for testing or bring in an expert, it could increase the price.

These are just a few suggestions, and are not meant to be taken as the rule in every situation when dealing with every fabricator. But it is good to know how your project was priced and what affected it so that there are no hidden surprises or confusion.   

So remember: supply ample information, receive accurate price. 

 

Read More

Topics: transmission structures, substation structures, structural steel fabricators, structural steel price, rfq request for quote, engineering estimating software, structural steel

3 Common Steel Structures Found Inside a Substation

Posted by Brooke Brackett on Jun 12, 2014 2:18:00 PM

In order to watch the fourth game of the NBA Playoffs when the Spurs trek into Miami territory to take on The Heat Thursday, June 12, you need a little thing called electricity. (Besides a television)

But before the electricity can travel into your home, it must pass through a substation first. A substation is an assemblage of equipment where electrical energy is passed in order to be stepped up or stepped down.

Transformers inside a substation change the voltage levels between high transmission voltages and lower distribution voltages. The high transmission voltages are used to carry electricity longer distances, like across the country, whereas lower distribution voltages travel to industrial, commercial or residential consumers.

In a T&D system, the major components typically consist of transmission lines, distribution lines, substations and switchyards.

describe the image

The three main types of structures found inside a substation include:

1.)    Dead-End Structures

2.)    Static Poles

3.)    Bus Supports/ Equipment Stands

Dead-end Structures are where the line ends or angles off. They are typically constructed with heavier steel in case they are needed to carry heavier tension. The two most common dead-end structures are H-Frame and A-Frame structures.

 H frame graph

A frame graph resized 600

describe the image

 

The second structure, a Static Pole, is a single, free-standing pole that creates a shield to protect all of the equipment inside a substation from lightning. Static poles may or may not have overhead shield wires attached to enhance protection. It depends on the size of the substation as to how many static poles are needed.             

NOTE: Tapered tubular design is typically efficient and economical in dead-end and static pole situations when compared to AISC standard shape structures.

Bus Supports are the most basic structure found inside a substation. Its main purpose is to provide support for rigid bus as it travels though the substation. Rigid bus is stiff and will not move around during weather events. Unlike rigid, flexible bus is typically used in high seismic describe the imageareas in order to be able to move and dampen the seismic forces that occur. 

Electrical equipment can be of significant weight and must meet specific guidelines for structural loads, deflection limits or clearance requirements. Equipment Stands are the structures that the actual equipment sit on.

Examples of some equipment stands include:

  • Potential Transformers (PT) Stands
  • Current Transformers (CT) Stands
  • Coupling Capacitor Voltage Transformer (CCVT ) Stands
  • Lightning Arresters (LA)
  • Switch Stands

When it comes to which type of steel is used, galvanized or weathering, inside a substation, I won’t say that you will never see weathering steel, but it is very rare. Weathering steel is used more in transmission structures than substation. One of the main reasons is because aesthetically, galvanized steel “looks” better inside a substation. Typically a substation is surrounded by a fence, has a metal building inside as well as white rock on the ground surrounding it. So the look of weathering steel, which is usually a dark brown color, aesthetically, goes better with a transmission line running through the woods to blend in versus in a substation.

So, I'm sure you'll be thinking about all of this tonight as the Spurs and Heat battle it out on the court!

 

 

 

Read More

Topics: electrical substations, Voltage, transmission lines, substation, power, distribution lines, switchyards, equipment, static

  

Subscribe

Posts by category

see all

Follow Me