You’ve got a vessel ready for PWHT. You’re calling furnace shops, getting freight quotes, checking schedules. That’s the process most fabricators run — because for most fabricators, a heat treating furnace is the only option they’ve ever used.
It isn’t the only option. And for large pressure vessels, it’s often not the best one.
What shipping to a furnace actually costs you
The furnace shop price is one line item. The real cost of furnace PWHT on a large vessel runs deeper.
Freight both directions on a finished pressure vessel adds up fast — and that’s before you factor in the risk. A fully welded, inspected vessel represents weeks or months of fabrication work. Every time it moves, you’re adding lifts, road transport, and handling by people who weren’t on your floor when it was built. If something gets damaged in transit, you own that problem.
Then there’s schedule. You’re not the only customer at that furnace shop. If their queue is full when your vessel is ready, you wait. On a job with a delivery date attached, that’s not an abstraction.
And furnaces have fixed dimensions. Length limits. Diameter limits. Weight limits. The bigger your vessel, the shorter the list of furnace shops that can actually handle it.
There’s another way to do this
Direct gas fire on-site PWHT means a heat treating contractor comes to your facility. They bring everything: combustion equipment, insulation, thermocouples, strip chart recorders. Your vessel stays on your floor. They wrap it, install the gas train, run the heat cycle to full ASME Section VIII Division 1 compliance, document everything, and break down when it’s done.
No freight. No size constraint from a fixed enclosure. No waiting on another shop’s schedule. The vessel gets heat treated where it was built, then ships directly to the customer when you’re ready.
This isn’t a workaround. ASME Section VIII Division 1 doesn’t require furnace PWHT. It requires the right temperatures, heating and cooling rates, hold time, and documentation. On-site direct gas fire combustion meets every one of those requirements. The documentation package your customer receives is the same.
Your shop keeps moving the entire time. GCC works around your crew and your schedule during every phase — setup, the heat cycle, and breakdown. For a typical job, here’s how the timeline actually breaks down.
New to on-site PWHT? Start here.
The Fabricator’s Complete Guide to Pressure Vessel PWHT covers exactly how on-site direct gas fire combustion works — code requirements, heat cycle parameters, thermocouple placement, and what a complete documentation package looks like.
No vessel too large
Gulf Coast Combustion runs gas trains up to 6–8 million BTU. There’s no length limitation. We’ve performed on-site PWHT on vessels over 120 feet long. The vessel that won’t fit in a furnace anywhere in your region is a standard mobilization for a contractor set up to do this work.
If you want to see what the process looks like, the time lapse above shows a complete PWHT cycle on a 70-foot, 600,000-pound vessel — insulation wrap to strip-out, start to finish, in about 90 seconds.
This math gets even more favorable the farther you are from a major furnace shop. Fabricators in Midland, Beaumont, Corpus Christi, Victoria, and across Texas are moving vessels hundreds of miles to a furnace — paying freight both ways — when we can drive to them instead. Outside of Houston, the savings can be significant.
When furnace is still the right call
Smaller vessels with routine transport and no schedule pressure — furnace works fine. High-volume shops running standard-sized vessels through a shop they trust — keep running them. If your current process isn’t causing problems, there’s no reason to change it.
But if you’re pricing freight on a large vessel and something about it feels like a lot of exposure, it probably is.
Talk to us before you book the truck
Gulf Coast Combustion has performed more on-site pressure vessel PWHT per year than any other mobile heat treating company in the United States, since 2014. We mobilize anywhere in the country.
Call 713-425-3773 or visit our heat treating services page. If on-site makes sense for your job, we’ll tell you. If it doesn’t, we’ll tell you that too.
Ready to Get Started?
Talk to James About Your Next Project
Call or text the owner directly at 832-797-3428 — or reach the office at 713-425-3773.
Frequently Asked Questions
Do you need any special utilities or gas supply at my facility?
We bring everything for the heat cycle itself — combustion equipment, gas trains, insulation, thermocouples, and recorders. Fuel is typically propane, which we supply and bring to the job site, so no natural gas connection is needed at your facility. The one thing we typically use on-site is 480 volt 3-phase power for support equipment. Power draw is low because the actual heating comes from the gas burners, not electricity. Most fabrication shops have this available without any special arrangements.
Is on-site PWHT ASME compliant?
Yes. ASME Section VIII Division 1 specifies temperature requirements, heating and cooling rates, hold times, and documentation — it does not require a furnace. On-site direct gas fire combustion meets every code requirement. The heat treat record, strip chart recorder trace, calibration certificates, and execution plan your customer receives are identical to what a furnace shop provides.
Is on-site heat treating more expensive than sending a vessel to a furnace?
On large vessels, on-site is typically competitive or cheaper once freight is factored in. Oversized load permits, rigging, pilot cars, and two-way transport costs can easily exceed the difference in heat treating price. For very large vessels — those that require special routing or are over weight limits — on-site almost always wins on total cost.
How long does on-site pressure vessel heat treatment take?
It depends on wall thickness, vessel size, and the heat treat procedure. Most jobs run one to three days from setup through breakdown. For a detailed breakdown by vessel size and wall thickness, see our post on how long on-site pressure vessel PWHT takes.
Is there a size limit for on-site PWHT?
No fixed limit. Gulf Coast Combustion has performed on-site PWHT on vessels over 120 feet long. Because we’re not working inside a fixed enclosure, vessel length and diameter don’t constrain us the way they constrain a furnace shop. If it can be built, we can heat treat it on-site.
Can you mobilize on short notice?
Yes. Gulf Coast Combustion handles short-notice and emergency mobilizations. Call James directly at 832-797-3428 — you’ll reach the owner, not a dispatcher.
Do you work outside of Texas?
Yes. Gulf Coast Combustion mobilizes anywhere in the United States. We’re based in Spring, TX and serve fabricators across the Gulf Coast as our primary market, but we regularly work in other states when the job calls for it.
Where We Work
Serving Fabricators Across Texas and the Gulf Coast
Houston | Beaumont/Port Arthur | Corpus Christi | Midland/Odessa | Victoria | San Antonio | Dallas/North Texas | Baton Rouge | Nationwide mobilization available
