Fabrication and Modular Construction
HII Mechanical’s capabilities include the fabrication of tanks, pressure vessels, structures and shield panels and piping assemblies. Our capability ranges from fabrication of individual components to modular construction of fully outfitted equipment skids and complex modules. We have extensive experience working to AWS & ASME standards for commercial customers; as well as nuclear and pressure vessel projects for government and military (DOD & DOE) requirements. We also maintain certificates of authorization from ASME and the National Board for fabrication, modifications, and repair.
Commercial Nuclear Structural Fabrication: AP1000 Dry Shield Building
HII Mechanical has experience in construction with carbon steels, low and high alloy steels, super alloys and other weldable material. Components and modules are fabricated at our main facility in Newport News, Virginia allowing for ease of shipment and transportation. Larger fabrications can be manufactured at our high bay facility, also located in Newport News, Virginia, or at the installation site. HII Mechanical offers turnkey service with the capability for design, fabrication, testing and installation.
HII Mechanical is unique in that it maintains the capability to provide welding services for both military and commercial customers. The company’s welding procedures have been qualified to NAVSEA standards for ship structure and piping/machinery/pressure vessels. For commercial applications, HII Mechanical’s procedure base also includes numerous procedures qualified to ASME IX.
Our knowledge of the AWS Structure Welding Code (AWS D1.1) allows us to fit, weld and NDE a wide variety of structures to the highest quality standards. HII Mechanical welders are qualified for flux core and gas metal arc welding of carbon and low alloy steels.
Welding Process Expertise Areas
GTAW (gas tungsten-arc) including pulse GTAW
GMAW (gas metal-arc) semiautomatic and mechanized
SMAW (shielded metal arc)
SAW (submerged arc)
Orbital and fixed head GTAW for mechanized welding of piping
Pulsed GMAW for out of position welding, semiautomatic and mechanized
FCAW (flux core) semiautomatic and mechanized
ESAB Boom Saw (Boom Welder)
Material Welding Expertise Areas
Austenitic, martensitic, ferritic and duplex stainless steels
Nonferrous metals (NiCu, CuNi)
High strength low alloy steels (HY-80/100,HSLA-80/100)
Inconel’s (600,625, Hastelloy 276)
Weld Management System - WMS
HII Mechanical utilizes a proprietary weld record management system that streamlines the weld record process and protects final record quality. This system also improves the overall cost performance by reducing the time required to record a weld to mere seconds with nearly flawless accuracy. The system can provide a single report identifying all the welds with the inherent critical data and/or a highly reliable report for each weld. This system, when utilized, saves countless hours of administrative processing time over the standard ‘wet’ record process.
Project and Fabrication Examples
Example: DOE Confinement Vessels
HII Mechanical fabricated six confinement vessels for the DOE which were used in photographing the characteristics of high energy explosions. The vessels were built to ASME and U.S. Navy standards using a special high strength, low alloy material. HII Mechanical developed and qualified the unique weld procedures, welded the vessels and performed all machining.
Example: Western Refinery 55,000 Gallon Blow Down Tank
The pictured Blowdown Tank was designed and fabricated by HII Mechanical in accordance with the ASME Boiler and Pressure Vessel Code, Sec VIII, Div 1 for unfired pressure vessels. The 55,000 gallon tank is 11’ x 60’ with a design pressure of 50 psig and full vacuum with a temperature of 800 degrees F. The shell plates (five sections) were rolled, edge prepped and welded at HII Mechanical’s Newport News, Virginia site. Radiography requirement was 100 percent. The vessel was transported to the refinery where the nozzles and saddle supports were fabricated and installed on the vessel. A hydrostatic test was performed at the client’s site and the exterior painted. Final acceptance of the new vessel was completed.
Example: DOE High Level Liquid Waste Vitrification Melter
This 3,500 gallon pressure vessel was built for the vitrification of liquid high level radioactive waste with glass. This vessel has a 2 1/2” thick, T304L stainless steel shell with 15 psig internal pressure and 150 psig in the water jacket. The vessel was machined on the inside diameter, including the radii of the top and bottom heads. The tank was mounted in a stainless steel frame with instrumentation, electrical heating elements, process piping and connection ports for robotic interface. This project was completed and delivered to a Department of Energy site in 2011.