Onsite Post Weld Heat Treatment (PWHT) Services in San Antonio, TX
In San Antonio's critical energy, manufacturing, and infrastructure sectors, welding quality isn't optional, it's a safety and compliance mandate. When welds are exposed to high temperatures, cyclic stress, or corrosive environments, Post Weld Heat Treatment (PWHT) becomes essential.
At Onsite USA, we specialize in field-based PWHT services in San Antonio, TX, providing mobile, code-compliant heat treatment that comes directly to your location. Whether you're servicing a power plant, fabricating pressure vessels, or maintaining critical pipelines, we bring calibrated equipment and certified technicians to your site, avoiding the hassle and delay of moving your components offsite.
What Is Onsite Post Weld Heat Treatment?
Post Weld Heat Treatment is a carefully controlled heating and cooling process applied to welded materials to reduce residual stresses, refine grain structures, and meet mandatory code standards. Unlike furnace-based heat treatment, our onsite PWHT approach applies localized heat to the welded area using resistance heating pads or coils, with no need to relocate your part.
This method is ideal for heavy, immobile, or integrated components in industries such as oil refining, petrochemicals, power generation, and structural steel fabrication. We deliver full-service, traceable heat treatment right where your weld sits, anywhere in San Antonio and surrounding regions.
Why Do Welds Need PWHT?
Welding introduces intense localized heat, which then cools rapidly. This causes uneven expansion and contraction, creating internal stresses that can lead to long-term failure.
PWHT addresses multiple critical needs:
- Mitigates residual stress buildup
- Enhances ductility and impact toughness
- Reduces risk of cracking and brittle failure
- Improves metallurgical stability
- Ensures code and regulatory compliance
In industries operating under ASME, AWS, or API standards, PWHT isn’t a luxury, it’s often mandatory for pressure-retaining or load-bearing components.
Sectors in San Antonio That Rely on Field PWHT
San Antonio serves as a key node in Texas’ industrial network, with sectors ranging from aerospace and energy to pipeline and structural fabrication. Our mobile PWHT services are frequently called upon during:
- Power plant construction and maintenance
- Oil & gas equipment fabrication
- Refinery turnarounds and upgrades
- Pipeline welding and repair
- Chemical plant shutdowns
- Water treatment facility retrofits
- Structural steel welding in public infrastructure projects
We operate throughout the greater San Antonio area, including Live Oak, Converse, Leon Valley, Universal City, New Braunfels, and Seguin. No matter your jobsite, we can be there.
Our Step-by-Step Process of Mobile PWHT
At Onsite USA, we tailor every PWHT cycle to your specifications and code requirements. Here’s how our process works:
Assessment and Planning
- Review WPS, material grade, thickness, and applicable codes
- Identify weld zones and determine number/type of thermocouples
- Engineer a customized heating cycle for your application
Site Setup
- Prepare weld area for safe thermocouple installation
- Apply ceramic resistance heaters or flexible coils
- Insulate and establish heating/cooling zones
Holding Period
- Maintain required soak temperature (e.g., 1150–1300°F) for defined time, often 1 hour per inch of material
- Monitor all zones continuously for accuracy
Cooling Phase
- Reduce temperature at code-specified rate
- Avoid rapid cooling to preserve microstructural integrity
Field-Ready Equipment and Capabilities
Our mobile heat treatment equipment is built for reliability, flexibility, and precision. We use:
- Resistance heating consoles with multi-zone control
- Flexible ceramic pad heaters and metallic coil wraps
- Digital chart recorders with real-time logging
- K-type thermocouples and high-grade insulation
- Portable power sources and environmental shielding
We work safely and efficiently in all industrial environments, from chemical plants and construction sites to fabrication yards and remote rural facilities.
Materials and Welds We Service
Our San Antonio team is equipped to perform PWHT on a variety of materials and weld types, including:
- Carbon steels (ASTM A106, A105, A516, etc.)
- Low-alloy steels (P1, P11, P22, P91)
- Welded pressure vessels and process piping
- Flanged joints, nozzles, and pressure fittings
- Large-diameter storage tanks
- Overlay welds, hardfacing repairs, and structural connections
We also provide simulated PWHT for welding procedure qualification and offer preheat/post-heat assistance where applicable.
Compliance You Can Trust
We perform all heat treatment work according to major international and domestic standards, including:
- ASME Section VIII Div. 1, B31.1, B31.3
- API 650, 1104
- AWS D1.1 and A2.4
- NACE MR0175
- Client-specific fabrication and inspection specs
Our certified technicians follow strict documentation and reporting protocols to ensure every weld passes inspection.
Why San Antonio Contractors Choose Onsite USA
At Onsite USA, we tailor every PWHT cycle to your specifications and code requirements. Here’s how our process works:
We Are 100% Onsite Focused
We don’t operate a shop. Everything we do is at your jobsite. Our systems are mobile, adaptable, and proven in the field.
Rapid Mobilization
Based in Texas, our San Antonio team is ready to respond within hours. We support shutdowns, night shifts, and emergency projects 24/7.
Areas We Serve
We offer onsite post weld heat treatment services across San Antonio and surrounding cities, including:
- San Antonio
- New Braunfels
- Schertz
- Seguin
- Boerne
- Kerrville
- Universal City
Get a Quote for Onsite PWHT in San Antonio, TX
Need local PWHT for your project in San Antonio? Let Onsite USA bring certified heat treatment to your welds, no matter the size, scope, or location. We help minimize downtime, improve safety, and deliver audit-ready results.
Call 346-291-2058 or submit inquiries online to speak with a PWHT specialist.
Don’t move the weld to the heat. Let us bring the heat to your weld.
Post Weld Heat Treatment - San Antonio, TX
Frequently Asked Questions
When should post-weld heat treatment be done?
PWHT should be performed after welding and non-destructive testing (NDT) are complete, and before final coatings. It must follow project codes and material-specific temperature/time cycles.
Is post-weld heat treatment the same as stress relieving?
Stress relieving is a common form of PWHT, but PWHT may also include other metallurgical goals like altering hardness or ductility, depending on code or service requirements.
Why do you heat treat after welding?
To relieve internal stresses, restore mechanical properties, and reduce the risk of cracking or distortion in pressure-bearing or structural welds.
What is the most common type of post weld heat treatment?
The most widely used PWHT method is thermal stress relief, which involves heating the weld to a specific subcritical temperature, holding it, and cooling at a controlled rate.
How many times can PWHT be done?
PWHT can be repeated as necessary, but frequent cycles may degrade material integrity. Always refer to code limits and metallurgical recommendations before repeating.
What is the difference between PWHT and annealing?
Annealing is done at higher temperatures to change microstructure and soften metals, while PWHT typically operates at lower temperatures for stress relief without significantly changing material properties.
How to determine if PWHT is required?
PWHT requirements depend on material type, thickness, service conditions, and governing codes like ASME or API. Review the WPS or consult a qualified welding engineer.
