Page 72 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

In addition, at low rates of total gas flow, the initial momentum of the
plume may not be enough to counteract the tendency of the plume to sink
---ใช้เพื่อการศึกษาเท่านั้น---
because of its initially high density.

The results of the interaction of these different processes at low wind
Windชย์นาวี
speed are illustrated in Figure 2.3. The gas mixture used in obtaining
these diagrams was 50% by volume propane and 50% by volume air, and
is typical of that to be expected when topping-off a crude oil cargo. At the
lowest flow rate (Figure 2.3 (a)) the density effect predominates and the
gas sinks back towards the deck. At the highest flow rate (Figure 2.3 (c))
mixing is far more efficient and there is no tendency for the plume to sink.

approx 12 m

งานห้องสมุด ศูนย์ฝกพาณิ

approx
9 9 mm

ึ Deck

a) Total gas flow 9 cubic metres/minute. Approximate loading rate 465 tonnes/hour.

Wind

approxp
9 9 mm

within darker area

approx 17 m

Deck

b) Total gas flow 28 cubic metres/minute. Approximate loading rate 1400 tonnes/hour.
Both illustrations above show a vent riser 6 metres above the deck.

The plumes are based upon wind tunnel data of:
Gas mixture 50% by volume propane in the air
Diameter of opening 254 millimetres
Wind speed 1.1 metres/second

Figures 2.3 (a) and (b) – Indicative effect of gas flow rate on flammable zone

38 © ICS/OCIMF/IAPH 2006