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A steam heated calorifier is to be used for heating the contents of the tank until the
evolution of inflammable gas is established, after which a gas fired boiler will be used.
With an experimental plant such as outlined above, information for guidance
on the large scale will be obtained on such points as period of digestion, optimum
temperature, heat requirements at different times of the year, net gas production,
reduction in sludge solids and de-watering of the residual solids to be sent to sea.
Precautions
against
explosions or
poisonous gas
in sewers.
With a view to making it possible to detect certain poisonous or explosive gases
in sewers by means of portable apparatus, several pieces of apparatus were examined
with known mixtures of air and coal gas, etc., for the purpose of checking their
reliability. Some were found to give quite accurate indications of the gas present,
whilst others gave erratic results, which might lead to unnecessary panic or give
a false sense of security. Generally speaking, these automatic devices are not sufficiently
"fool-proof" and require to be manipulated by a man skilled in handling
scientific apparatus. For purposes of detection only, the ordinary miner's testing
lamp is more convenient in the hands of workmen than these more elaborate devices,
and has been found useful when working in sewers. The matter of simple routine
test in the interests of safety in sewers is under consideration.
River subway
tunnels.
The systematic examination of the air in the river subway tunnels at Blackwall
and Rotherhithe has been continued during the year. Previous investigations having
shown that the worst conditions occur about 10 a.m. on weekdays, attention was
concentrated on this period of the day, so that it must be emphasised that the following
figures apply to the worst conditions normally occurring in the tunnels. At
Blackwall the average carbon monoxide content of 104 samples taken at regular
intervals during the year was 21.5 parts per 100,000, 39 of the samples exceeding
the recommended maximum figure of 20 parts per 100,000. Twenty-four determinations
of suspended matter gave an average figure of 6.2 on Owens' fog-shade scale,
10 of them exceeding the recommended limit figure of 6 (i.e., 1.92 milligrammes
suspended matter per cubic meter of air). In Rotherhithe tunnel the average carbon
monoxide content of 103 samples was 16.4 parts per 100,000, 25 of them exceeding
the limit figure of 20. Twenty-six determinations of suspended matter gave an
average of 7.3 on Owens' scale, 16 exceeding the limit figure of 6.
An analysis of the results showed clearly that the carbon monoxide concentration
tends to become much greater in summer than in winter; but the average
suspended solids content of the air remained fairly constant. A further portion of
the scheme for improving the ventilation of Blackwall tunnel, consisting of extraction
fans working in No. 1 shaft, was brought into operation in September. Results
obtained since then show a consequent improvement in the atmospheric conditions
at that end of the tunnel, but the full effect cannot be judged until the scheme has
been completed by the installation of the fans for blowing fresh air into the northernmost
section of the tunnel. No alteration was made in the ventilation system at
Rotherhithe during the year, but a scheme for improvement is being prepared by the
chief engineer.
British
Engineering
Standards
Committees.
The Council is represented by its chemist with other officers on two committees
of the British Engineering Standards Association, one on the Sampling and Analysis
of Coal and the other on Standard Definitions and Tests for Fire Resistance and
Incombustibility. The proceedings of the former committee have continued over
some years owing to the detailed nature of the problem involved and the necessity
for co-ordinating methods recommended with the requirements and conditions of
industry, but the proposed methods have been published in a tentative form and
after consideration of criticisms offered, will be issued in final form. The publication
of standard methods of sampling and analysis of coal, by a responsible association,
should do much to induce confidence in foreign buyers of coal who are used to much
more definite information as to the quality of fuel than satisfies buyers in this country.
The Committee on Fire Resistance and Incombustibility has set forth for