fbpx
Tuesday, January 21, 2025
Home Blog Page 46

Sheet Metal Details and Specialties

Chapter #7 – Sheet Metal Details and Specialties

Most engineered drawings have a section for details, which allow for additional information to be provided. It is easier for the Mechanical Engineer to provide a detail showing exactly all the components required for a particular piece of equipment, duct specialty item or other building component that requires more information than what can be but on the plan view.

If the engineer was to put all the detail information on the building plan view, then this would make for a very messy and crowded drawing. It’s important that you review all the details as this is where cost impacts are usually incurred because of special requirements not identified anywhere else on the documents.

Utility Fan Exhaust Stack

Utility fan will often require that you install a length of sheet metal off the discharge side of the exhaust fan to ensure that the exhausted air doesn’t get entrained back into any of the building intakes. Often this stack will need independent supports like guy wires attached to a ring near the top of the exhaust stack and the other end of the wire attached to the roof structure. This will prevent the stack from being blown away on windy days.

Utility Fan Stack
Utility Fan Stack

Utility Fan Exhaust Stack

The two most common ways that Utility Exhaust fans support their discharge ducts or stacks are shown here. Above the discharge duct is support by the fan housing, while the exhaust stack (duct) shown below is support by the roof and has guy wires for additional stability during stormy weather. Of course, the detail below is going to have a greater cost impact. This is why its important to review the details.

Exhaust Fan Guy Wires
Exhaust Fan Guy Wires

Linear Diffuser Detail

Linear diffusers are used to provide a more pleasing look as envisioned by the architect, then the traditional square diffuser. Linear diffusers also cost more than the standard diffuser or grille. In this detail the engineer has also specified “Stainless Steel” duct bands (highlighted in yellow) which are more costly than the standard plastic pandit type. You would add this item to your sheet metal specialties page to include the additional cost. These bands hold the flexible duct securely in place to avoid becoming detached or so as to prevent leaking.

Linear Diffuser Details
Linear Diffuser Details

Linear Diffuser Detail

Acoustical Wall Penetration

When penetrating a wall that is acoustically rated to prevent the transmission of sound you would need to include the cost to sound proof your duct penetrating the wall. If you had a noisy room adjacent to a private office then you would want to make sure that none of the noise was transmitted from one space to the other.

Acoustical Sealing Duct Penetrations
Acoustical Sealing Duct Penetrations

Acoustical Sealing of Duct Penetration

Elbows at Diffusers or Registers

Engineers, certain facilities and various jurisdictions require that you install a 90 degree elbow at each piece of air distribution. This was most likely in response to projects where flex was installed incorrectly, causing kinks that reduced airflow to the space. To ensure proper airflow a 90-degree elbow is installed at the point of the diffuser or register as shown below. The traditional method is shown in the next detail where a flexible duct connection is used to attach the ductwork to the diffuser.

Flex with Elbow at Air Distribution
Flex with Elbow at Air Distribution

Air Distribution Connection Detail

There are several items that makeup a connection to a piece of air distribution. Each piece of air distribution should have a Balancing/Volume Damper to adjust the volume of air coming out of or into the air distribution. Some jurisdiction will allow a piece of flex duct to make the final connection between the duct and the air distribution grille.

Flexible Air Duct

Air Distribution Connection Detail

Steam Humidifiers

There are certain rooms that require that the RH (Relative Humidity) remain within a range, such as between 40% & 70% RH. A humidifier is installed in the duct to ensure proper humidity to the space. Since steam (moisture) is added to the air stream by the humidifier to maintain the required RH levels, the need for a non-corrosive duct material within a certain distance before and after the humidifier will be required, in addition to a drain.

As shown in the detail below, the engineer has specified that 4 feet before and 8 feet after the humidifier shall be constructed of welded stainless steel. Also, there are two access doors shown, one on each side of the humidifier to allow for easy viewing of the internal components of the humidifier.

Steam Humidifiers
Steam Humidifiers

 Roof Mounted Exhaust Fans

There are many types of roof mounted exhaust fans that require a curb to sit on. In addition there will be a Gravity Backdraft Damper to prevent outside air from being forced into the building under increased pressure from outside due to winds and storms.

A sheet metal transition is often required because the duct drop is a different size then that which connects to the exhaust fan. Check the vendors quote to make sure that the exhaust fan comes with the rood curb and BDD (backdraft damper). This also applies to exhaust and intake hoods that don’t have a motor, but strictly operate on pressure differentials.

Roof Exhaust Fan Detail
Roof Exhaust Fan Detail

CAV or VAV Detail

CAV (constant air volume) or VAV (variable air volume) air terminals may come with a sound attenuator as shown in the below detail. This is usually something provided by the air terminal manufacture, so you won’t need to price this as a piece of sheet metal, but you will need to confirm that the vendor has included them in their proposal. The sound attenuator (#3 below) muffles any noise coming from the CAV/VAV.

Also, if the inlet duct (#1 below) to the air terminal unit exceeds a certain distance then a requirement to increase the duct one size may be specified as shown in this detail. This is to ensure that the proper amount of air reaches the air terminal. There may also be a requirement to provide a high side flexible duct (#2 below) on the inlet side of the air terminal. When you look closely you will also see that there is a 90-degree elbow (#4 below) at the diffuser.

CAV Terminal Details
CAV Terminal Details

Remote Damper Operators

Used where dampers are concealed above inaccessible ceilings. The remote damper operator allows you to adjust the CFM (airflow) going through the duct by adjusting the damper position in the duct from a remote location like a wall or ceiling.

Remote Damper Operators
Remote Damper Operators

Sheet Metal Field Installation Course

Grease Exhaust Duct

Chapter #8 – Grease Exhaust Duct

Grease duct is welded in order to prevent fires caused by the flammability of the hot grease igniting construction materials surrounding the duct and fittings. The ducts and fittings need to be supported by hangers of non-combustible materials designed to carry the weight and seismic load if applicable.

No fasteners or support screws are allowed to penetrate the duct as this would provide a point of possible failure and fire. The grease duct must contain access doors for inspections and cleaning, so don’t forget to include them in your estimates.

Kitchen Exhaust System
Kitchen Exhaust System

The grease duct is required to slope to prevent the accumulation of grease in horizontal installations.

Grease duct is either routed through a fire rated shaft enclosure or wrapped with an approved fire insulating blanket that allows for zero clearances, such as that manufactured by 3M.

Grease duct can be made out of Black Iron, Galvanized or Stainless Steel material depending on the code of jurisdiction the project falls under. Areas that are exposed are usually made out of stainless steel because of its aesthetic properties.

In all cases the joints and seams will be welded, the only exception are those factory manufactured duct systems as defined latter in this chapter. The minimum duct thickness is defined by whatever code jurisdiction that the project is located in. Below are two code references related to the required thickness and material type for grease ducts.

IMC – International Mechanical Code 506.3.1.1

IMC Grease Duct Requirements
IMC Grease Duct Requirements

CMC – California Mechanical Code 510.5.1

CMC Grease Duct Requirements
CMC Grease Duct Requirements

Grease Duct Joints

There are several approved methods of making a welded joint for grease exhaust ductwork. The choices will depend on the code for your jurisdiction but should include flanged, telescoping, Bell type or overlapping joints. Flanged joints are made by bending the end of the raw duct or fitting to make a ¼” flange. Below is the code section for the International Mechanical Code for the allowed welded duct connections types.

IMC Welded Duct Connections
IMC Welded Duct Connections

Below is a sample of the Bell type joint. The male side of the joint belongs on the uphill side of a sloping duct so that the grease will drain back down. The female side of the duct contains the bell portion for which the male portions slips into, and then it gets welded completely around its perimeter.

Grease Exh Joint Type
Grease Exhaust Duct Welded Joints

Canopy hoods have requirements to extend at least 6” beyond cooking surface, this is to ensure the entrainment of any heat and smoke.

Factory Built Grease Ducts

These duct assemblies are required to be in accordance with UL 2221. CaptiveAire makes a double wall grease duct that has insulation between two metal walls. The duct sections are constructed of an inner duct wall and an outer wall with insulation in between. The inner duct wall shall is constructed of .036 inch-thick, 430 type stainless steel and is available in diameters 8″ through 36″. The outer wall is constructed of stainless steel at a minimum of .024 inch-thickness.

Watch the two video’s below of CapitiveAire’s single wall system which requires no welding.

Single Wall Grease Duct
Adjustable Single Wall Grease Duct

The duct, based on model number, shall include layers of Super Wool 607 Plus, Insulfrax Elite Blanket insulation, or Unifrax S16 Bulk Fiber insulation between the inner and outer wall. Grease duct joints are held together by means of formed V clamps and sealed with 3M Fire Barrier 2000+.

Grease Exhaust CaptiveAire
Grease Exhaust CaptiveAire

#1 Adjustable Grease Duct Section

#2 Double V-Band (Connects two duct sections together)

#3 Vertical Support – Installed under V-band

#4 Standard Length of Grease Duct

#5 Kitchen Hood

#6 Duct Sensor

Double wall grease ducts are listed for a continuous internal temperature of 500 degrees F and intermittent temperatures of 2000 degrees F.

Hood Types

There are several ratings for hood types, Type I and Type II.

Type I hoods are rated for use with Deep Fryers, Char Broilers, grills, Pizza Ovens and all solid fuel appliances (wood, Charcoal, Briquettes and Mesquite).

Core Fire Protection

Type II hoods are rated for use with Steamers, Dishwashers

Grease Duct Wrap

Using a fire blanket like that made by the 3M company allows you to eliminate the need for rated gypsum board enclosures, which take up valuable space. These fire blankets are rated to be installed with zero clearance, which means they can be touching building materials and don’t require a rated enclosure. and be safe from fire.

3M Fire Blanket
3M Fire Blanket

3M’s Fire Barrier Duct Wrap 615+ protects ducts for up to 2 hours. The fire duct wrap is applied in a single layer for protecting ducts from an external fire, and requires two layers of the Fire Barrier Duct Wrap for grease ducts.

  • 1-Layer (External Fire Protection)
  • 2-Layers (Grease Duct)
https://youtu.be/GOdj6XWbDbo
Grease Duct Wrap

The single layer can be used for life/safety systems like stairway pressurization ducts which provide for the pressurization of stairways in order to keep smoke from infiltrating into the stairwell every time someone opens a stairwell door.

Grease Duct Access Doors

Access doors in sheet metal are used to provide a means of accessing the inside of a duct or an internal component.

Access doors provided in grease ducts are required by code to allow for the periodic cleaning and inspection of the interior buildup of grease on the walls of the duct and fittings.

Sheet Metal Field Installation Course

Air Distribution

Chapter #9 – Air Distribution

The fan blows or sucks air through a duct and exits or enters a piece of air distribution. There are different types of air distribution devices based on types of ceilings and the engineer’s preference. In the image below there are three different ceiling types (1, 2, 3) shown for the Supply Air Diffusers.

Ceiling Types

#1 – No ceiling (There is no ceiling in this room because it’s used for the engineering dept.)

#2 – Gypsum board ceiling.

#3 – Acoustical tile (2’ x 4’)

Air Distribution Test Q1
Ceiling Types for Air Distribution

Remember that the Architectural Reflected Ceiling Plan shows the type of ceiling for each area. The Mechanical engineer may use that reflected ceiling plan has the starting background image before they design the HVAC system over it.

Supply air grilles and registers have options on the directional throw as shown in the image above, you have Supply Ceiling Diffuser (#1) shown as a 3-way throw, hence the three arrows. Supply Ceiling Diffuser (#2) is shown as a 2-way throw, and Supply Ceiling Diffuser (#3) is shown as a 4-way throw.

Have you ever been in a restaurant or other place of business and felt a draft drop down over you while you were sitting eating or conducting business? This is poor air distribution design, as you should never feel the air, it should just blend in without any draft on you.

Linear Diffusers

Linear diffusers are used in areas that require a more aesthetically pleasing look due to the ceiling design or layout.

The plenum will be installed first and then once the sheet rock is installed, the sheet metal field technician will return to install the actual linear diffuser.

Linear Slot Diffusers

Shown below is what a linear supply and return diffusers looks like on the actual drawings. Each engineer draws them slightly different, but it should show as a skinny long grille. The blue arrows show the supply linears and the orange arrow shows the return linear.

In this design, the return air is ducted as shown by the single line duct leading from the center of the back of the linear. Often in commercial buildings the return air will be non-ducted, in which case the air will travel back to the HVAC equipment through the attic space.

Linear Diffuser MEPAcademy
Linear Diffusers as Represented on Drawings

HEPA and ULTRA HEPA Filter Grilles

HEPA filters are used when cleanliness is a requirement for a space. This could be a pharmaceutical or micro-chip manufacturer, hospital or laboratory. There are various levels of cleanliness from ISO-1 through ISO-9, or Class 1 through Class 100,000. You don’t have to worry about this right now, but you will need to get pricing and provide labor to install. Watch the video below to see what a 2’ x 2’ HEPA filter grille looks like.

HEPA Filter

Fan Powered HEPA Filters

This is a special type of air distribution device where a fan is located within the housing that supply’s air through a HEPA filter to provide clean air to a critical space such as a cleanroom or operating room. You would request a quote from the manufactures representative and provide the appropriate labor to install them. It takes much longer to install these special air distribution devices than a normal diffuser, possibly 2 to 4 hours each depending on the type and hanging requirements.

Fan Powered HEPA Filtration

Flexible Duct Connections

The majority of air distribution connections from branch ducts are made with a flexible duct connector. This is represented by a little squiggly mark between the duct and the air distribution diffuser.

Air-Dist_test_Q4
Flexible Duct Connection

Some air distribution diffusers won’t need a flexible connector as they maybe located where there isn’t a ceiling as shown in the below image. In this case you would use a hard 90-degree elbow. In some jurisdictions, the use of a 90-degree elbow is mandated by code, so check your local code authority.

No Flex
No Flex

The following shows the proper method of attaching flexible duct to either the can or collar on the Air Distribution Diffuser or the branch duct.

Item #1 shown in the image below shows that a bead or lances provide the best method for keeping the flex secured in place. If the flex will be hanging vertically with gravity and its own weight pulling down, then its recommended to add sheet metal screws (#2) to hold it from slipping off.

Flex Duct Assembly
Flex Duct Assembly

Estimating Spreadsheet

Enter the information on your estimating spreadsheet under the HVAC Equipment Tab. Indicate the Quantity of each type (#2), the Total Quantity (#3), Unit of Labor per each (#4), the Vendor Name and Pricing (#5). This estimating spreadsheet from MEP Academy automatically picks the lowest bidder, but can be overwritten by the estimator by entering a different value in the “Plug or Quote” box highlighted in yellow.

Spreadsheet Air Distribution
Spreadsheet Air Distribution

Sheet Metal Field Installation Course

HVAC Equipment Labor

Chapter #12 – HVAC Equipment Labor

There are several sources for equipment labor values. But none is better than the contractors own historical data of the actual time required to set a piece of HVAC equipment in place. Below is a list of published data on equipment rigging and setting time. Read carefully the information contained in each reference as to what the labor units include and exclude, so that you can make any necessary adjustments.

MCAA (The Mechanical Contractors Association of America)

MCAA

MCA publishes labor hours for various pieces of HVAC equipment such as, Air Handlers, Chillers, Pumps, Cooling Towers and accessories. Each category of HVAC equipment has a range of sizes with varying amounts of labor required to set in place. Depending on the geographical location of your project, you will apply a factor to these values. Members get access to their online database of labor.

SMACNA (Sheet Metal and Air Conditioning Contractors National Association)

SMACNA publishes labor units for sheet metal duct and fittings in addition to certain HVAC equipment and accessories based on National averages. Air Conditioning Units, Coils, Fans, Filters, Sound Traps and miscellaneous items are available with various units of labor based on the size and or weight of the item. The SMACNA labor manual also provides a means to adjust labor based on difficult and very difficult conditions. The labor data was derived from surveys of sheet metal and air conditioning contractors in the United States and Canada, which included data from actual projects.

RS Means (Gordian)

Gordian publishes material and labor values for a wide range of construction components and assemblies for all trades. Many municipalities use the Gordian system for their procurement of construction services. The material and labor database is maintained and updated regularly by the Gordian Group.

PHCC (Plumbing-Heating-Cooling Contractors Association)

PHCC publishes labor data which you can purchase. Their database covers a wide range of pipe, valves and fittings in addition to some equipment.

Company Historical Data

Historical Data that your company keeps from projects that have been completed is the best data available for your estimates. The problem is that most companies done take the time or effort to document these values, so they will need to rely on one or more of the industry published databases mentioned above for their benchmark labor.

If your company doesn’t keep track of the time it takes to rig and set in place the various pieces of HVAC equipment, I would suggest starting such effort in order to understand what it takes in the way of man hours and effort. It doesn’t matter what some industry database says it should take if your company can do it faster or slower than the published productivity rate. So begin to establish a company standard with the cooperation of your project managers and field personnel to record the time it takes to rig and set equipment and the various factors and conditions involved.

Basic Assumptions in Published Labor Databases

The industry published labor data for the time required to rig and set HVAC equipment is based on certain assumptions which are usually listed at the beginning of their labor manuals. Be sure to read any of the footnotes (MCA) or Correction Factors (SMACNA) on any of the equipment labor tables contained within these industry databases, as they will indicate any additional conditions or assumptions to be aware of. Assumptions might include some of the following which you should be thinking about when you go to labor the equipment and accessories.

Part of the process of dealing with equipment and accessories is the unloading, stockpiling, assembling, erecting and preparing the equipment for startup and testing. Depending on how your company prefers to allocate their labor, there might be a separate category of labor called material handling in which different pay rates are utilized.

Things to Consider When Figuring Equipment Labor

Location of Equipment

The industry equipment labor databases assume that the equipment will be within a certain distance from where it is to be installed, such as with MCA it’s assumed to be received within 100 feet from its final destination.

Size and Weight of HVAC Equipment

Equipment that weights under 250 Lbs (per MCA) is considered to be handled by a two person crew with the use of chain falls, hi-jacks or similar tools.

Chain Falls
Chain Falls

Equipment that is over 250 Lbs might require a Roustabout, chain falls, crane, forklift, lift jacks, rollers, etc. to move them and get them in place. Below is a Genie Lift with varying capacity based on the model you own.

Genie Lift
Genie Lift

How heavy is the equipment? Cooling Towers, Chillers, Large Boilers and Air Handlers will require rigging by a crane, forklift or helicopter depending on its location in the building or on the roof. Is the physical size of the equipment too large to be handled safely by workers? Will you need equipment rollers or the use of a hoist? Does the equipment come in several pieces in order for it to fit on a truck from the factory?

roustabout
roustabout

You must become familiar with each piece of equipment and what is required to get it rigged and set in the location shown on the drawings. Is the equipment located indoors or outdoors?

Access to Equipment Location

  1. How will the equipment get into its designated location?
  2. If it is an existing building will the equipment fit in the service elevator or through doorways to its final resting spot?
  3. Does the equipment easily breakdown into smaller pieces for rigging?
  4. Is there room for a crane to setup on the side of the building closet to the equipment?
  5. Do you need a street closer permit in order to block traffic during the rig so the crane can setup in the street?
  6. Are there electrical overhead wires preventing a crane from operating in the area?
  7. Do you need a helicopter?
  8. Do you have to move other equipment or services to get your equipment in position?

Above are just a few of the things to think about when laboring equipment. You will need to adjust the standard labor based on the perceived risk and jobsite conditioned expected to be encountered during construction.

Method of Support

Is the equipment hung from above or set on the floor or roof? Does the equipment sit on vibration isolation? Do you need to build a support frame to hold the equipment, or does the equipment come with its own supports? Are seismic restraints required, as they add additional time to your equipment setting labor because of the additional time to install the restraints? Look at the detail pages on the drawings to find any engineered attachment or support methods.

Equipment Accessories

Does the equipment come with parts unattached for field assembly? Large filter racks need to be built up in place and then have their filters inserted. Sound traps can come with many modules needing assembling. Economizers are sometimes shipped loose and need to be attached. Backdraft dampers and roof curbs for exhaust fans. Vibration isolators for all types of equipment are a separate component that gets installed with the equipment. Cooling towers have ladders, motor davits and vibration isolators that ship separately.

HVAC Equipment Accessories
HVAC Equipment Accessories

Multiple Pieces

Does the equipment come in several pieces because they are too large to ship in one piece, or are too large to fit through an existing doorway? Air handlers can be shipped broken down into fan, coil and filter sections all separated for easy shipment and field assembly. Cooling towers and fluid coolers also come in multiple sections. Talk to your vendor about how they plan to ship any large equipment that could possibly come in multiple pieces.

Crew Size

How many men are required to rig and set in place each piece of equipment? Composite crews made up of piping and sheet metal union workers will set anything that has piping and sheet metal attached to it, each union claiming a part of the work. As such, any piece of equipment that has only sheet metal attached will be claimed by the sheet metal union and vice versus for the piping union. If you work for a non-union company then worrying about jurisdictional labor allocation isn’t a problem. (See chapter on Labor Crew Size)

What Information Should You Record

Most of the information that you will need to labor the equipment can be found on the equipment schedule of the plans and specifications, or from the equipment submittal of the manufacture. Below is a list of a few items and what characteristics you might list for each piece of equipment on your estimating spreadsheet to help you provide a value for labor.

Air Compressors: List the HP (Horsepower), Receiver Capacity, Dimensions and Weight.

Air Conditioners: List the type, Tons, CFM (Cubic Feet per Minute), Dimensions and Weight. Types might include “Self-Contained”, “Water-Cooled Vertical”, “Packaged Rooftop Gas/Electric”

Air Handlers: List the type, CFM, Dimensions and Weight. Types may include Multi-Zone, Floor or Ceiling mounted, Custom, Roof Mounted.

Boilers: List the Type, HP (horse power), If steam Lbs/Hr, BTUH (BTU per Hour), Weight.

Chemical Feeders: Tank Capacity, size and weight

Chillers: Type, Tons, Air or Water-Cooled, Accessories

Coils: Type, Area FT2, Dimensions, rows of coils and weight.

Compressors: Type, Tons and weight

Condensate Return System: GPM (Gallons per Minute), Dimension and weight.

Condensers: Type, Tons, Dimensions and weight

HVAC Equipment Tab – Estimating Spreadsheet

Equipment labor should be applied to every piece of equipment and accessories that the field labor will be required to rig and anchor in place, whether fasten to the ground or hung in the air, or sitting on the roof. Your estimating spreadsheet should allow for conveniently allocating hours for each piece of equipment alongside its pricing.

HVAC Equipment Spreadsheet
HVAC Equipment Spreadsheet

HVAC contractors can provide both the sheet metal and HVAC piping requirements for a project. Some pieces of equipment will require a composite labor crew; especially if they’re a union company with define roles for each trade. Equipment that has water or refrigerant connected to it along with sheet metal may require a composite labor crew.

Enter the quantity and description of the equipment, and then enter the unit of labor required for each piece of equipment. If you have four (4) Rooftop Upblast Exhaust Fans that sit on a roof curb, you might enter 4 hours each if they’re smaller units, which would give you a total of 16 sheet metal hours for the 4 small exhaust fans.

Retrofit Projects

If you are bidding on a project that is within an existing building, then you will need to consider additional labor items. Ducts and pipes will need to be disconnected from the HVAC equipment. Water will need to be drained out of any pipes connected to any equipment receiving any form of water or steam service.

To get large pieces of equipment out of existing spaces, often requires that it be taken apart or cut into pieces. If your company doesn’t do this type of work, there are specialty companies that you can subcontract this work to. If you are bidding on a turn-key project, one in where your company is responsible for all trades, then you will need to get other companies involved, this usually occurs under the design/build method of construction contracts.

What’s Not Included in the Labor Units

Start Up & Testing of Equipment

The time for startup and testing is a separate labor task that is usually done by trained technicians different than those installing the equipment. These specialized individuals are familiar with the procedures and documentation required for starting up and testing HVAC equipment.

Air and Water Balance

Often the specification will require a third party to perform the air and water balancing in order to avoid conflicts of interest that occur when the contractor self performs this work. Typically the specifications will call for the Air and Water Balance Company to use NEBB or ABBC certified technicians to perform the work.

Equipment Identification

Each piece of HVAC, Plumbing or Electrical equipment will get an identification tag that identifies what the equipment is, along with some of its capacity information and possibly the area it serves.

HVAC Equipment Tags
HVAC Equipment Tags

There will be a unit cost for material and labor for every equipment ID tag. A field laborer will need to fasten the equipment tag somewhere visible to the maintenance staff when accessing the equipment. The background and lettering color maybe dictated by the specifications and is often provided on some form of laminated plastic. Put this requirement on the sheet metal specialties tab of your estimating spreadsheet. (see chapter on Sheet Metal Specialties)

Sheet Metal Specialties
Sheet Metal Specialties – MEP Academy Estimating Spreadsheet

Get a copy of the MEP Academy Estimating Spreadsheet.

Sheet Metal Field Installation Course