Page 61 - International safety guide for oil tankers and terminals

HAZARDS OF PETROLEUM

3
---ใช้เพื่อการศึกษาเท่านั้น---
1Infra-red source
2Window
3 Mirror
4Window
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
5 Beam splitter
r
7 Measuring detector
8 Reference filter
9 Reference detector

4

2
8

9

ึ 6
1

5 7

Figure 2.2 – Infra-red sensor

2.4.7 Measurement of Low Concentrations of Toxic Gases

2.4.7.1 Chemical Indicator Tubes

Probably the most convenient and suitable equipment for measuring very
low concentrations of toxic gases on board tankers are chemical indicator
tubes.

Measurement errors may occur if several gases are present at the
same time, as one gas can interfere with the measurement of
another. The instrument manufacturer’s operating instructions
should always be consulted prior to testing such atmospheres.

Chemical indicator tubes consist of a sealed glass tube containing a
proprietary filling which is designed to react with a specific gas and to
give a visible indication of the concentration of that gas. To use the
device, the seals at each end of the glass tube are broken, the tube is
inserted in a bellows-type fixed volume displacement hand pump, and a
prescribed volume of gas mixture is drawn through the tube at a rate
fixed by the rate of expansion of the bellows. A colour change occurs

© ICS/OCIMF/IAPH 2006 27