Preface
The preparation of the seventh edition of this established book on marine auxiliary machinery has necessitated the removal of some old material and the inclusion of new topics to make it relevant to the present day certificate of competency examinations. It is hoped that the line drawings, many of which were provided by Mr R. C. Dean, a former colleague in London, will be useful for the certificate of competency and other examinations. The majority of other illustrations and much of the basic text have been provided over the years by the various firms listed in the Acknowledgements. I am grateful to those firms who have supplied me with material added in this edition.
H. D. McGeorge
15
Safety and safety equipment
Much that is written or promulgated with respect to safety at sea is concerned with the obvious sort of risks that threaten those who are careless in any work situation. The survival of seafarers is additionally jeopardized by special factors, many of which are not obvious and not always present. Thus entry to enclosed spaces whether they are ballast or cargo tanks, pumprooms, cofferdams or even dry cargo holds may be made hazardous by the presence of dangerous liquids, toxic or flammable gas from a cargo or ballast water or by the absence of oxygen.
Closed spaces
The fore peak is an example of a tarJc that can remain closed and unventilated for long periods. The atmosphere in such a tank may become deficient in oxygen due to corrosion resulting from the remains of sea-water ballast or condensation. Oxygen may also be depleted by the presence in sea water of hydrogen sulphide which tends to oxidize to sulphate. Hydrogen sulphide (which is toxic) is a compound which, like ammonia, is produced by bacteria in the water, reducing sulphates and nitrogen compounds. Water containing pollutants such as hydrogen sulphide are picked up when ballasting in esturial waters. Some countries have banned the discharge into their waters of ballast from certain areas due to the presence of harmful bacteria.
Whilst oxygen is depleted, carbon dioxide may be given off by sea water due to other chemical changes. Thus a tank, apparently safe because it has been isolated by being closed, is dangerous to enter due to lack of oxygen and sometimes the presence instead of carbon dioxide and possibly other gases. The small manhole for entry at the top of the tank will not give much natural ventilation of the compartment. Fatal accidents have resulted from entry to fore peak tanks which have not been properly ventilated.
Normal oxygen content of air is about 21%. Where a test shows that there is a lower value in an enclosed space, ventilation should be continued until the correct level is reached. The air changes necessary to improve the oxygen level will have the beneficial effect of lessening the possible presence of any gas or vapour which may be harmful. A lower than normal oxygen level can cause loss of efficiency; it may cause loss of consciousness resulting in a fall, with serious or even fatal injury.
In other closed compartments oxygen may be deficient due to being absorbed by chemicals or drying paint, or because it has been excluded by the presence of other gases or vapours (e.g. vapour from cargo, refrigerant, inerting gas, smoke or fumigant). Ventilation is required before entry to any ballast tank, cargo space, pumproom or closed compartment and must be maintained while work is being carried out.
Marine safety card
The General Council of British Shipping issued a safety card with precautions and a check list, to be used by personnel intending to enter a closed compartment.
Gas analysis
Fixed oxygen analysers are fitted to ships with inert gas systems. These continuously monitor the oxygen content of the flue gas and the inert gas. Para-magnetic type analysers are frequently used. These feed an electrical signal to the oxygen indicator which is calibrated in the range 0—10% by volume. The analyser is connected to audible and visual alarms which are activated when the oxygen level rises above the desired value.
Portable oxygen content meters are also carried and used to check that individual tanks are suitably inerted. Conversely a portable meter can also be used to check whether the atmosphere in a tank will support life and thus permit personnel to enter the tank with safety. If there is any doubt that a tank atmosphere is safe, then breathing apparatus should be worn when entering.
Oxygen analyser
In order to measure the amount of oxygen in a sample from the atmosphere of a closed space or from flue gas, there must be some way of isolating it from the rest of the sample. One physical property which distinguishes oxygen from most other common gases is its para-magnetism. Faraday discovered that oxygen was para-magnetic and was, therefore, attracted by a magnetic field. The field will also induce magnetism in the oxygen, i.e. a magnetic field is intensified by the presence of oxygen and its intensity will vary with the quantity of oxygen.
Most gases are slightly diamagnetic, that is, they are repelled by a magnetic field. Thus glass spheres filled with nitrogen and mounted at the ends of a bar to form a dumb-bell (Figure 15.1) will tend to be pushed out from the strong symmetrical non-uniform, magnetic field in which they are horizontally suspended.
The dumb-bell arrangement is used in the Taylor Servomex analyser. It is suspended by a platinum ribbon in the field and, being slightly diamagnetic, it takes up a position away from the most intense part of the field. The magnets and dumb-bell are housed in a chamber which has an inlet and outlet for the sample. When the sunrounding gas contains oxygen, the dumb-bell spheres are
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Preface
The preparation of the seventh edition of this established book on marine auxiliary machinery has necessitated the removal of some old material and the inclusion of new topics to make it relevant to the present day certificate of competency examinations. It is hoped that the line drawings, many of which were provided by Mr R. C. Dean, a former colleague in London, will be useful for the certificate of competency and other examinations. The majority of other illustrations and much of the basic text have been provided over the years by the various firms listed in the Acknowledgements. I am grateful to those firms who have supplied me with material added in this edition.
H. D. McGeorge
前言
这本已经出版过的关于辅机的书的第七版准备工作已经使得一些旧材料的移除和为了确保本书与当前的适任证书考试相关联而引入新的主题成为必要。本人希望划线部分会适应适任证书和其他种类考试的需要而有用。这些划线部分中的许多都由本人的一位伦敦的前同行R.C.Dean先生提供。其他的插图和许多的基础文本中的大多数已经被各种列在鸣谢中的公司证实过很多年。本人向那些在此版本中向本人提供了材料的公司致以感谢。
H.D.McGeorge
15
Safety and safety equipment
Much that is written or promulgated with respect to safety at sea is concerned with the obvious sort of risks that threaten those who are careless in any work situation. The survival of seafarers is additionally jeopardized by special factors, many of which are not obvious and not always present. Thus entry to enclosed spaces whether they are ballast or cargo tanks, pumprooms, cofferdams or even dry cargo holds may be made hazardous by the presence of dangerous liquids, toxic or flammable gas from a cargo or ballast water or by the absence of oxygen.
15
安全与安全设备
许多写下来或发表出来的有关海上安全的文件都是关于一系列显而易见的威胁到那些在任何一种工作场景下粗心大意的工作人员的风险。但除此之外，海员的安全有时还受到一些特殊的因素造成的威胁。这些因素当中的许多并不是显而易见的，也不是经常出现的。因此，进入一些封闭的空间，不管是压载舱，还是货舱，还是泵房，还是沉箱，甚至是干货舱，都可能因为一些危险的液体，来自货物或压载水的有毒或可燃气体，甚至是缺氧情况的出现，而变得危险。
Closed spaces
The fore peak is an example of a tarJc that can remain closed and unventilated for long periods. The atmosphere in such a tank may become deficient in oxygen due to corrosion resulting from the remains of sea-water ballast or condensation. Oxygen may also be depleted by the presence in sea water of hydrogen sulphide which tends to oxidize to sulphate. Hydrogen sulphide (which is toxic) is a compound which, like ammonia, is produced by bacteria in the water, reducing sulphates and nitrogen compounds. Water containing pollutants such as hydrogen sulphide are picked up when ballasting in esturial waters. Some countries have banned the discharge into their waters of ballast from certain areas due to the presence of harmful bacteria.
封闭空间
艏尖舱是一种长期保持封闭和不通风的舱室的例子。在这样一种舱室内的空气可能会由于一些由压载海水或冷凝水的残余而导致的腐蚀而变得缺氧。氧气也可能因为在海水中的硫化氢发生化学反应氧化转化成硫酸盐而消耗殆尽。硫化氢（有毒）是一种复合物。这种复合物，比如氨气，是由水中的细菌消耗硫化物和氮气的复合物而产生。含有比如硫化氢这样的污染物的水在泊地加压载水时被抽上船。一些国家已经禁止了向他们的水域排放来自因为有害细菌存在而特别划定的特定区域的压载水。
Whilst oxygen is depleted, carbon dioxide may be given off by sea water due to other chemical changes. Thus a tank, apparently safe because it has been isolated by being closed, is dangerous to enter due to lack of oxygen and sometimes the presence instead of carbon dioxide and possibly other gases. The small manhole for entry at the top of the tank will not give much natural ventilation of the compartment. Fatal accidents have resulted from entry to fore peak tanks which have not been properly ventilated.
与此同时，氧气被消耗，二氧化碳也会由于海水内其他的化学反应而放出。因此，一个舱室，尽管看上去由于已经通过封闭而隔离而显得安全，实际上，进入其中却是非常危险的，因为缺少氧气，以及有时候除了二氧化碳之外其他可能的气体的存在。在舱室顶部为人员进入准备的小洞不会给这个舱室进行多少自然的通风换气。进入没有被妥善通风换气的艏尖舱这种行为，已经导致过致命的事故。
Normal oxygen content of air is about 21%. Where a test shows that there is a lower value in an enclosed space, ventilation should be continued until the correct level is reached. The air changes necessary to improve the oxygen level will have the beneficial effect of lessening the possible presence of any gas or vapour which may be harmful. A lower than normal oxygen level can cause loss of efficiency; it may cause loss of consciousness resulting in a fall, with serious or even fatal injury.
空气正常的氧气含量大约21%。一项测试显示，在密闭空间内，氧气含量会低于这个值。所以，应该一直通风换气直到氧气含量达到正确值。为了增加氧气含量而进行的有必要的空气交换会对减少任何有害气体或水蒸汽的可能存在产生有益的影响。氧气含量比正常值低会导致人缺少效率；会导致人丧失意识，并由此导致摔倒，而产生严重甚至致命的伤害。
In other closed compartments oxygen may be deficient due to being absorbed by chemicals or drying paint, or because it has been excluded by the presence of other gases or vapours (e.g. vapour from cargo, refrigerant, inerting gas, smoke or fumigant). Ventilation is required before entry to any ballast tank, cargo space, pumproom or closed compartment and must be maintained while work is being carried out.
在其他的封闭舱室内，氧气也许会由于被化学物质或变干的涂料所吸收，或者由于其他的气体或蒸汽（比如来自货物，冷凝剂，惰性气体，烟雾或薰蒸剂的蒸汽）的存在驱除了氧气，而变得非常缺少。在进入任何压载舱室，货仓，泵房或密闭舱室之前都必须进行通风换气。而且，在工作正在进行的时候，必须一直保持通风换气。
Marine safety card
The General Council of British Shipping issued a safety card with precautions and a check list, to be used by personnel intending to enter a closed compartment.
船用安全卡
英国航运总协会发布了一个带有预防措施和核对表的安全卡，以备计划进入封闭舱室的人员使用。
Gas analysis
Fixed oxygen analysers are fitted to ships with inert gas systems. These continuously monitor the oxygen content of the flue gas and the inert gas. Para-magnetic type analysers are frequently used. These feed an electrical signal to the oxygen indicator which is calibrated in the range 0—10% by volume. The analyser is connected to audible and visual alarms which are activated when the oxygen level rises above the desired value.
气体分析
带有惰性气体系统的船舶都配有固定的氧气分析器。这些分析器持续不断地监控可燃气体和惰性气体的氧气含量。船上往往使用顺磁式的分析器。这些分析器发送一种电信号给氧气指示器。这种氧气指示器被精确量化，误差只有总量的百分之零到十。分析器连接着能使人听到和能使人看到的警报器。这些警报器每当氧气含量值超过预先设定的值时就会被激活。
Portable oxygen content meters are also carried and used to check that individual tanks are suitably inerted. Conversely a portable me
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