Class 4 (4th Engineer) SSEP 📅 Jan 2025

Exam Question

With reference to the cargo tanks of oil tankers:

(a) State:

(i) The purpose of the pressure vacuum valve;

(ii) The dangers of venting during loading via open tank hatches;

(b) (i) Sketch a high velocity vent;

(ii) Describe the operation of this vent and state why such a device is used.

Reference Answer

### (a) (i) The Purpose of the Pressure Vacuum (P/V) Valve
The primary purpose of a Pressure Vacuum (P/V) valve, as fitted to an oil tanker's cargo tank, is to provide automatic protection against structural damage from abnormal pressure differentials. It is a critical safety device mandated by SOLAS Ch II-2, Reg 11.
**1. Over-Pressure Protection:**
- **Cause:** Pressure builds up inside a cargo tank due to:

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