Precision Rupture Disc
Product Model: ZD-018 (Combined P/V Breather)
Design: Two discs in one assembly: a forward-acting disc for overpressure relief and a reverse-buckling disc for vacuum relief.
Key Feature: Protects vessels from both overpressure AND vacuum collapse in a single, compact unit.
Settings: Independent pressure and vacuum burst settings are available.
Typical Use: Storage tanks for solvents, chemicals, or oils; reactors subject to both heating and emptying; transportable containers.
Overview
Many tanks and vessels face dual hazards: overpressure from filling or heating, and vacuum from emptying or cooling. Installing two separate devices can be costly and space-consuming. This combination unit integrates both protections into one flange connection. It features a forward-acting disc that ruptures outward for overpressure relief, and a separate reverse-acting disc that buckles inward for vacuum relief. This provides complete tank protection with simplified installation and maintenance.
Features & Benefits
Dual Protection in One: Saves space, cost, and installation time compared to two separate devices.
Independent Settings: The pressure and vacuum relief values can be specified independently to match the vessel's design limits.
Clear Indication: Often includes indicators to show which disc has been activated (pressure or vacuum).
Compact Design: Fits on a standard tank nozzle, minimizing roof or shell penetrations.
How It Works
The assembly contains two separate rupture discs mounted back-to-back in a common holder. One disc (forward-acting) faces the tank interior and bursts open to relieve positive pressure. The other disc (reverse-acting) also faces the tank but is designed to buckle inward (towards the tank) when the internal pressure is sufficiently lower than atmospheric, allowing air to enter and prevent collapse.
Specifications (Descriptive)
Common tank nozzle sizes: DN80, DN100, DN150, and DN200. Pressure relief settings are typically low, e.g., 0.2, 0.5, 0.7 barg. Vacuum relief settings are also low, e.g., -0.05, -0.1, -0.2 barg. The overpressure disc is usually a scored forward-acting type. The vacuum disc is a non-fragmenting reverse-acting type. The holder body is typically carbon steel coated or stainless steel. The unit often comes with a weather hood and flame arrester option for outdoor flammable liquid tanks.
Q&A
Q: What happens after one disc bursts? Does the whole unit need replacement?
A: Yes. The unit is typically sealed and non-repairable in the field. If either disc activates, the entire combination unit must be replaced to restore both forms of protection.
Q: Can this replace a Pressure/Vacuum Relief Valve (PVRV)?
A: It serves a similar function but is non-reclosing. A PVRV opens and closes, conserving product vapor. This disc assembly is a relief-of-last-resort and vents to atmosphere. It is often used as a secondary safety device behind a PVRV or for products where vapor conservation is not critical.
Q: Is it suitable for pressurized tanks (e.g., LPG)?
A: No. This is designed for low-pressure atmospheric storage tanks. Pressurized vessels (ASME pressure vessels) require primary relief devices sized and set according to pressure vessel codes, which are different products.
About ZD Safety
We provide complete tank safety solutions. Our P/V breather discs offer a simple, effective, and economical way to achieve essential overpressure and vacuum protection for a wide range of storage applications.
