Jacketed Globe Valve
Valves / Globe ValveA jacketed globe valve features an outer pressure vessel (jacket) welded around the body that circulates steam, hot oil, or thermal fluid to maintain process media temperature, preventing solidification or viscosity increase of materials like sulfur, bitumen, polymers, and waxes.
Working Principle
The valve functions as a standard globe valve for flow control, but the body is surrounded by a welded jacket that creates an annular space for heat transfer fluid circulation. Steam or hot oil enters the jacket, transfers heat through the body wall to the process fluid, and exits through a return connection. The jacket covers the body and typically the bonnet area where process media contacts the valve. The jacket operates at a separate pressure from the process (usually lower), and has its own pressure rating. The valve must be designed so that the jacket does not interfere with body integrity — the process-side pressure boundary remains independent of the jacket.
Key Components
Jacketed body (inner process boundary + outer jacket), bonnet (may also be jacketed), disc, seat ring, stem, packing, jacket inlet/outlet connections, handwheel or actuator.
Types & Variants
| Type | Key Feature | Typical Use |
|---|---|---|
| Full-body steam jacket | Complete body jacket with steam | Sulfur, bitumen, wax processing |
| Partial jacket (seat area only) | Jacket covers seat zone only | Polymers, resins that gel at seat |
| Hot oil jacket | Thermal oil circulation jacket | High-temperature polymer processing |
| Extended bonnet + jacket | Jacket + extended bonnet | High-viscosity media at elevated temperature |
Common Materials
Inner body: ASTM A216 WCB or A351 CF8M per process requirements. Jacket: typically carbon steel (A36 or A516 Gr.70) for steam service, stainless for hot oil. Disc and seat: Stellite-faced or 13Cr per process. Packing: graphite for high-temperature. Jacket connections: flanged or socket weld per heat medium.
Applicable Standards
- API 600 (steel gate/globe valves, reference for body design)
- ASME B16.34 (pressure ratings for process side)
- ASME Section VIII Div.1 (jacket pressure vessel design)
- API 602 (forged jacketed valves, reference)
Industrial Applications
- Sulfur melting and processing plants
- Bitumen and asphalt handling
- Polymer and resin manufacturing
- Wax and paraffin processing
- Heavy fuel oil and pitch handling
- Chemical processes with high-pour-point fluids
Advantages & Disadvantages
Advantages
- Prevents process media from solidifying or gelling in the valve
- Maintains consistent process temperature through the valve
- Available for both isolation and throttling service
- Jacket pressure is independent of process pressure — safe design
Disadvantages
- Significantly heavier and more expensive than standard globe valves
- Jacket welds require special NDE and quality control
- Jacket introduces a second pressure boundary — leak potential between jacket and body
- Maintenance is more complex — jacket must be drained before valve service
Selection Guide
- Specify the heat transfer medium, temperature, and pressure for the jacket separately from the process conditions
- Full-body jacket is preferred when the process media can solidify anywhere in the valve cavity
- For sulfur service, specify 316L body with steam jacket at 4-6 bar to maintain sulfur at 140-155°C
- Ensure jacket pressure rating is lower than process pressure rating — if jacket fails, process fluid stays contained
- Jacket welds should be 100% radiographed to ASME Section IX
Practical Tips
- The most common failure on jacketed valves is the jacket-to-body weld cracking from thermal cycling — specify full-penetration welds with radiographic inspection
- Never isolate the jacket circulation while process fluid is in the valve — the process media will solidify and the valve will be impossible to operate until reheated
FAQ
What is the difference between a jacketed valve and a trace-heated valve?
A jacketed valve has a welded pressure vessel around the body for direct heat transfer fluid circulation. Trace-heated valves use external tubing or electric tracing. Jacketing provides more uniform and reliable heating but is more expensive and cannot be retrofitted.
What pressure is the jacket rated for?
Jacket pressure is typically much lower than process pressure — commonly 6-10 bar for steam, or 10-20 bar for hot oil. The jacket is designed per ASME Section VIII as a separate pressure vessel with its own rating.