How Pressure Vacuum Relief Valves Work

A Pressure Vacuum Relief Valve (PVRV) is a low-pressure safety device installed on atmospheric storage tanks to protect against overpressure and vacuum conditions that could cause structural failure. Unlike conventional pressure relief valves designed for high-pressure vessels, PVRVs operate at very low pressures — typically 0.5 to 3.5 kPa (2 to 14 inches water column) above or below atmospheric.

The valve uses a weight-loaded or spring-loaded pallet system that opens when the pressure differential exceeds the set point. When tank pressure rises above the set point (during filling or thermal expansion), the pressure pallet lifts, allowing vapor to vent to atmosphere. When tank pressure drops below atmospheric (during pump-out or thermal contraction), the vacuum pallet opens, allowing air to enter and prevent tank implosion.

Modern PVRVs feature low-leakage diaphragm seals (PTFE or FEP) that minimize fugitive emissions during normal operation. The API 2000 standard defines the venting capacity requirements that PVRVs must meet, including thermal breathing, liquid displacement, and emergency fire exposure scenarios.

Key Technical Specifications

ParameterSpecification
Nominal SizeDN50 (2") - DN300 (12")
Set Pressure Range+0.5 to +3.5 kPa (pressure); -0.2 to -2.0 kPa (vacuum)
Design Temperature-50 to +150 C (standard); up to +250 C (high-temp)
Body Material316L Stainless Steel, Carbon Steel (painted), Aluminum (light-duty)
Seat SealPTFE diaphragm (low-leakage); Buna-N / Viton (economy)
Leak Rate< 0.1 SCFH at 75% set pressure (API 2000 compliant)
CertificationAPI 2000, ASME, EAC, GOST R

Applications

  • Atmospheric Storage Tanks: Crude oil, gasoline, diesel, jet fuel, chemicals (API 650 tanks)
  • Low-Pressure Vessels: Process vessels operating near atmospheric pressure
  • Breathing Loss Control: VOC emission reduction through low-leakage seals
  • Cold-Climate Service: Heat-traced models for ice prevention at -40 to -50 C ambient

Certifications & Standards

Wanan PVRVs are designed per API 2000 7th Edition for venting capacity, with set pressure accuracy per API 2000 Section 4. Body and pallet components are manufactured from 316L stainless steel with guaranteed low-temperature impact properties (down to -50 C). EAC and GOST R certifications are available for CIS market installations. Optional ATEX certification is available for Zone 1/2 explosive atmosphere installations.

Pressure Relief Valve

Pressure Relief Valve

Dual rail system for smooth strokes and low wear

Leakage is well below API2000 standards and guarantees high setting accuracy (±3%).

Full opening at 10% overpressure

Spool and seat assemblies are field replaceable

Supports ANSI, DIN, and HG/T20592~20635~2009 flanges.

Pressure Relief Valve - Pressure Vacuum Valves | Wanan Technology
Pressure Relief Valve - Pressure Vacuum Valves | Wanan Technology

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FAQ

A closed loop sampler is a safety device used to collect liquid samples from pipelines or storage tanks without exposing operators to hazardous chemicals. Wanan closed loop samplers comply with API MPMS 8.2 standard and feature a sealed design that returns purge fluid back to the process, eliminating VOC emissions.

Wanan flame arrestors are certified to ISO 16852, ATEX (European Explosive Atmospheres Directive), and EN 12874 standards. We provide type test reports for IIA, IIB, and IIC gas groups. All products are manufactured in our ISO 9001:2015 certified facilities.

Yes. Wanan Technology is a registered qualified supplier for Sinopec, PetroChina, CNOOC (China), ExxonMobil, LukOil (Russia), ENI (Italy), KazMunayGas (Kazakhstan), and PDVSA (Venezuela), among others.

Wanan Technology has manufacturing facilities in Germany, USA, and China. We also have inventory and sales service centers in UAE to serve Middle East and global customers with fast delivery.

Wan’an Technology’s closed sampler is suitable for liquid sampling scenarios involving toxic and hazardous media in petrochemical, natural gas, oil refinery, and tank farm industries. It complies with API MPMS 8.2 standards, prevents operators from coming into contact with hazardous substances, and meets HSE environmental emission requirements.

A: Standard products ship within 2-4 weeks from order confirmation. Custom-engineered solutions typically require 6-8 weeks depending on specification complexity. For urgent projects, we offer expedited production upon request — contact our sales team with your timeline and we will work out a schedule.

A: Our products comply with major international standards including ISO 3170 (petroleum sampling), API MPMS 8.1/8.2, ATEX for explosive atmospheres, ASME, and EAC. DOT and TPED certifications are available for sample cylinders. We provide full certification documentation and material test certificates with every order.

A: Yes. We offer sample units for evaluation purposes. Upon approval, we ship one or two units so you can verify compatibility with your application, materials, and site conditions before committing to a volume order. Shipping costs may apply depending on destination.