British Columbia
FIXING A WORN METAL PART OR HAVING A NEW ONE MADE
Repair a part when the reason it failed can be fixed too. Have a new one made when the metal has thinned through, or the same crack would come back.
Sheet metal repair makes sense when there's sound metal left and you can deal with what made the part fail. A new part makes sense when rust has eaten through, or when a weld over the old crack would only crack again. Guards and load-bearing parts add rules of their own. This guide covers how each metal is repaired, which parts need an engineer, and how a new part is made from a worn one.
The damage itself tells you most of the answer. Find the closest match to your part, and the third column says why.
| What you see | Repair or a new part | Why |
|---|---|---|
| A crack at a bolt hole, a corner, or the end of a weld on a part that shakes | A repair only if the area is also stiffened, otherwise a new part with a stronger design | A crack welded over without changing the stress usually comes back |
| Rust that has eaten holes through the metal or left it thin | A new part | There's no sound metal left to weld to |
| A bend or dent with no crack | Often a repair, straightened in the shop | The metal is still whole and can be bent back |
| Galvanizing scraped or burned off in a patch | A repair to the coating | A zinc coating can be restored without replacing the part |
| A part on a crane, hoist, or lifting rig | Neither, until the manufacturer or an engineer decides | WorkSafeBC requires that sign-off on load-bearing repairs |
If you can't tell why the part failed, start there. A repair or a new part made the same way will fail the same way. If you still have the drawing, a new part made from it is often simpler than a repair.
Most cracks in a guard, bracket, or panel that shakes are fatigue cracks. A fatigue crack grows a little each time the part flexes from vibration or repeated loads. It usually starts at a sharp corner, a hole, or the edge of a weld. TWI, the UK welding research institute, notes that a weld repair often doesn't last as long as the original part. That's why the repair has to deal with the stress too.
Find what's flexing the part. Look for a loose mount, a missing support, or a sharp inside corner where the crack started.
Stop or remove the crack. It's ground out and welded, or the part is cut back to sound metal. A small hole drilled at the crack's tip can slow it, but only until the stress finds it again.
Add metal or change the shape. A stiffener, heavier gauge, or rounder corner spreads the load away from where the crack began.
A crack repair lasts when the shape that caused it changes too
Illustration of a mounting tab on a guard that vibrates. The crack started at a sharp inside corner.
Find the cause
The tab flexes at a sharp inside corner each time the machine runs.
Remove the crack
The crack is ground out and welded.
Add metal or change the shape
A stiffener spreads the load away from the corner.
If step 3 changes the part, it changes the drawing too. Drawing Revision Control on Repeat Parts explains when that needs a new revision letter.
Welding heat harms galvanized, stainless, and aluminum in different ways, and each needs its own fix after a repair.
| Metal | What a repair has to deal with | Commonly used for |
|---|---|---|
| Galvanized steel | Welding burns off the zinc next to the weld. The bare area is recoated with zinc-rich paint, zinc solder, or sprayed zinc, the three repairs ASTM A780 allows | Ductwork, roof curbs, filter boxes, and brackets |
| Stainless steel | The grade has to be known, because 304 and 316 take different filler wire. The coloured tint the weld leaves has to come off, or the metal rusts there first | Kitchen equipment, drain pans, and guards on equipment that gets washed down |
| Aluminum | Many aluminum alloys have been heat treated for strength, and welding undoes part of that. The metal beside the weld typically loses 30 to 50% of its strength | Enclosures, covers, and lightweight equipment parts |
A magnet won't tell you the stainless grade. Bent or rolled 304 and 316 can both pick up a magnet, so the grade comes from the original paperwork or a test. If neither is available, a new part in a known grade is often the safer call.
On galvanized work, welding also gives off zinc fumes, which WorkSafeBC links to metal fume fever, a flu-like illness. That's one more reason galvanized repairs belong in a shop with proper fume extraction.
A guard keeps hands away from moving parts, and a cracked or bent one is a safety problem before it's a repair job. Five sections of BC's Occupational Health and Safety Regulation apply to fixing it.
Section 4.11 says required safeguards must be in place and working before any machine is put into operation. If the guard is off for repair, the machine stays off.
Section 12.4 says a safeguard must be able to do its job. If a patched guard flexes into the moving parts or leaves a gap, have a new one made.
Section 4.12 rules that out, and a guard held on with tape or wire isn't a repair. Take the machine out of service, as section 12.10 requires, until the guard is fixed.
Section 4.3 says repairs follow the manufacturer's instructions or a professional engineer's. A new guard is made to the maker's drawing when you have it.
Some parts carry loads that would hurt someone if a repair failed. For these, the decision isn't the fabricator's, and the rules say who makes it.
| Part | Who signs off | Rule |
|---|---|---|
| Load-bearing parts of a crane or hoist | A professional engineer or the original manufacturer | WorkSafeBC OHSR section 14.13 requires their certification after any repair |
| Rigging and fittings repaired by welding | A professional engineer, before the rigging goes back into use | OHSR section 15.28, which also says alloy steel chain must never be welded |
| Welded steel that holds up a building | The structural engineer | CSA S16, the Canadian steel structures standard, requires a welding shop certified to CSA W47.1 |
| Welded aluminum that holds up a building | The structural engineer | CSA S157, the Canadian aluminum structures standard, requires a welding shop certified to CSA W47.2 |
If your part falls in one of these rows, start with the engineer or the manufacturer. Ask any welding shop for its certification before the work is booked.
A new part is only as good as the sizes it's made from, and a worn part has lost some of its original sizes. These steps get you back to them.
Look for the original drawing first. If you have it, or the part number and revision letter, the new part is made to that.
Without a drawing, measure the parts that didn't wear. Holes, bends, and faces that didn't rub or rust usually keep their original sizes.
Mark the worn edges on your sketch. Say which edges rubbed, rusted, or cracked, so nobody copies the damage.
Send the worn part, or clear photos with a tape in them. The part shows the bends and hole positions better than any sketch.
Check the first new part on the machine before ordering more. If it fits, keep the drawing for the next time it wears out.
A worn bracket has lost some of its original sizes
Illustration of a bracket with one rusted, rubbed edge, drawn over a dashed outline of its original shape.
Take sizes from what didn't wear
Holes, bends, and faces that didn't rub or rust keep their original sizes.
Mark the worn edge on the sketch, so the new part isn't made to it.
First Article Inspection for Sheet Metal Parts covers what to check on that first part. Spares you need once in a while are compared in Small Batch Metal Fabrication.
Each of these is an illustration, not a Duct Duct Goose job. They show how the cause and the metal left decide the answer.
An equipment maker's guard cracks where its tab meets the panel, at a sharp corner, on a machine that vibrates. A weld and a stiffener would hold, but there's no room for a stiffener here. So a new guard with a rounded corner is made, and its drawing gets a new revision letter.
A curb adapter, the galvanized frame that lets a new rooftop unit sit on an old roof curb, gets scraped during the lift. The steel is fine and only the zinc is gone, so the scrape is cleaned and coated with zinc-rich paint.
A drain pan under a unit drips at one welded corner. If the grade is known and the pan is clean, the corner is welded and the tint removed. If the bottom has pitted through, a new pan is the better buy.
Most failed repairs fix the damage and leave the cause behind. Six of the most common are below, with what to do instead.
| Mistake | What happens | Do this instead |
|---|---|---|
| Welding over a crack and changing nothing else | The crack comes back, often beside the repair | Add a stiffener, a heavier gauge, or a rounder corner |
| Copying the sizes of the worn part | The new part has the old one's wear built in | Make it from the drawing, or from the parts that didn't wear |
| Welding galvanized and leaving the weld bare | The bare steel rusts first | Recoat the area with zinc-rich paint, zinc solder, or sprayed zinc |
| Welding stainless with the wrong filler or leaving the tint | The weld rusts or stains before the rest of the part | Confirm the grade, match the filler, and clean the tint off |
| Welding a part still coated in grease or oil | A fire risk, and gas holes that weaken the weld | Clean the part fully before any welding, as WorkSafeBC requires |
| Running a machine with a taped-on guard | The guard can't do its job, and the rules are broken | Keep the machine off until the guard is repaired or replaced |
Repairs and new parts are both made on our floor in Pitt Meadows. Every job starts with a look at why the part failed, before anyone picks up a welder.
Send photos, the drawing, and what the part does. Close-ups of the damage and a full view with a tape help most.
We look at the cause and the metal left. Then we tell you whether we'd repair it or make a new part, and why.
We tell you what the repair can't fix. Thin spots or old damage away from the repair are named before the work is quoted.
The part comes to the shop. A repair is welded, ground, and finished, and painting is done here too.
A new part is made from the drawing. We keep that drawing on file for the next time the part wears out.
If a part we made fails because of our mistake, we fix or remake it at no charge. Repairs and new parts are both joined through our welding and assembly work. Guards and brackets are covered on our custom metal supports and enclosures page.
Most worn guards, brackets, and panels are a good fit for a local shop. Load-bearing repairs and a few kinds of used equipment belong with someone else.
If a repair won't last, we'll say so and quote the new part instead, even when the repair is the smaller job. A guard that cracks twice costs you more than one that's made right once.
The more we can see in your photos and notes, the sooner we can tell you whether to repair or replace.
For a part that wears out often, Reorder Quantity for Fabricated Parts shows how many to order at a time. More guides for repeat parts are in OEM, Prototype and Repeat Production.
Clear photos with a tape and a drawing from the original maker are both a fine place to start. We'll tell you what's missing before anything is cut or welded.
Standard ductwork and fittings price instantly on WebDuct, the online pricing and ordering portal, with a company account. Repairs, production parts, stainless, and other custom work start with a request or a call.
At Duct Duct Goose, we specialize in sheet metal fabrication and stainless steel services for commercial and industrial applications, including HVAC systems, ducts, and custom metalwork. Please note that we do not offer services for automotive-related projects, such as vehicle parts, repairs, or modifications.
