Thermal Relief Valves (Liquid Thermal Expansion Relief)
Engineered to safeguard pipelines, heat exchangers, chemical loading arms, and storage manifolds against catastrophic hydraulic pressure spikes caused by solar radiation, heat trace runaway, or ambient thermal heating of trapped incompressible liquids. Features optical flatness disc lapping ensuring zero bubble leakage at 90% set pressure.
Design Criteria & Sizing Standards
Thermal relief valves designed and tested strictly according to API 520 Sizing Criteria, API 526 Flanged Dimensions, and API 527 Seat Tightness Protocols. Full EN 10204 3.1 material traceability provided with every factory unit.
| Engineering Parameter | Applicable Codes, Standards & Design Criteria |
|---|---|
| Governing Standards | API RP 520 Part I & II, API Spec 526, ASME Section VIII Div 1, ISO 4126-1 |
| Pressure Class Range | ASME Class 150, 300, 600, 900, 1500, 2500 (PN 20 to PN 420) |
| Standard Orifice Designation | API Orifice "D" (0.110 sq in / 71 mm²) & "E" (0.196 sq in / 126 mm²), Micro-Orifices available |
| Seat Tightness Protocol | API 527 Zero Leakage / Bubble-Tight at 90% of cold set pressure (tested with air or water) |
| Overpressure Allowance | 10% for non-fire thermal relief; 21% for fire contingency per ASME Section VIII |
| End Connection Geometry | Female NPT / Male NPT (ASME B1.20.1), Socket Weld (ASME B16.11), Flanged RF/RTJ (ASME B16.5) |
| Trim Hardfacing & Disc Seal | Precision Optical Lapped Stellite 6 / Dual Soft-Seat Inserts (Viton, PTFE, PEEK, Kel-F) |
| Sour & Marine Environmental | NACE MR0175 / ISO 15156 Sour Gas Resistance, Inconel X-750 Spring Options |
Thermal Relief Valve Standard & Engineered Models
TSV manufactures a specialized lineup of Thermal Relief and Small-Bore Hydraulic Expansion Valves for blocked pipeline segments, cooling water jackets, LNG vaporizers, and hydrocarbon loading terminals.
In-Line Flanged Liquid Thermal Expansion & By-Pass Valve
Flanged body geometry designed for seamless bolting into piping bypass headers. Provides smooth proportional pop action to absorb liquid expansion pressure surges.
Heavy-Duty Multi-Station Header Thermal Relief Valve Array
Designed for critical refinery tank farm manifolds and offsite pipeline headers, providing standardized relief capacity across multiple parallel process headers.
Duplex Twin Changeover Thermal Relief Safety Valve Unit
Dual safety relief valve configuration mounted on an integrated changeover diverter, enabling online valve servicing, recalibration, and statutory testing without shutting down the facility.
High-Temperature Jacketed Line Thermal Relief Valve
Exposed spring and open bonnet geometry preventing thermal spring relaxation on jacketed lines, asphalt services, and heat transfer oil loops up to 425°C.
Hydraulic Liquid Thermal Expansion Mechanics & Sizing Rules
Liquids are virtually incompressible. A slight rise in trapped liquid temperature without expansion volume results in catastrophic pressure escalation, frequently rupturing pipes or crushing valve seats.
Solar Radiation Entrapment
When pipeline block valves are closed on sunny days, solar heat raises the entrapped fluid temperature by 15°C to 30°C. For hydrocarbon liquids, pressure rises approximately 1.0 to 2.5 MPa (145 to 360 psi) for every 1°C increase, rapidly exceeding the pipeline rating.
API 520 Sizing Formulation
Required discharge capacity is calculated using V = (β · Q) / (500 · G · c), where β is the cubical expansion coefficient and Q is total heat transfer rate. Because required liquid volumetric relief is very small (often < 5 gpm), small-bore "D" or "E" orifices are ideal.
Zero Chatter Pop Action
Unlike standard gas safety valves that pop open violently, TSV Thermal Relief Valves feature contoured disc lips and dual adjusting rings to modulate relief rate smoothly without hydraulic shock waves (water hammer) or destructive rapid seat chattering.
Explore All 4 Safety & Relief Valve Sub-Categories
1:1 aligned with TSV factory catalog. Navigate to spring full-lift steam safety, modulating pilot-operated, parallelled back-flow, or thermal relief valves.
Spring Safety Valve
ASME I & VIII full-lift enclosed spring safety valve with blowdown control rings for boilers and vessels.
ASME I & VIII Full Lift View Details →Pilot-Operated Safety Valve
Modulating and snap-action pilot valves operating bubble-tight up to 98% of set pressure on gas pipelines.
API 526 Pilot Operated View Details →Parallelled Safety Valve
Specialized parallel dual-chamber safety back-flow valve for liquid discharge, LPG pump bypass, and vessel return.
AHN42F Parallel Back-Flow View Details →Thermal Relief Valve
Compact high-pressure thermal expansion relief valves protecting piping, heat exchangers, and liquid lines.
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