Fig. 85.
These attachments, also called Try cocks, are usually placed in a conspicuous and accessible position on the front of boilers. They are so arranged that one will blow only steam, one at the working level of the water, and the third at the lowest water level or say three inches above the highest point of the fire line of the boiler. The cut, [Fig. 85], exhibits them as commonly arranged.
It is not essentially requisite, that the cocks themselves should be placed at the point indicated, so long as they have pipes projecting internally into the boiler, with their ends corresponding to the height of water above mentioned. In order that these cocks may readily be cleaned out, a plug is usually fitted into bit of cock opposite the port or opening of the plug, upon removing which a pricker can be readily inserted.
The gauge or cocks should be tested many times each day, and when opened the top one should always give steam and the bottom one water. They should be allowed to remain open long enough to make sure whether steam or water is issuing from the cock. This is a matter of instruction, but the beginner with a little experience can detect the difference by the sound.
In so universal an appliance as this there are very many forms and arrangements, but they all work upon the same principle as stated above.
GLASS GAUGES.
These are the second and auxiliary arrangements for ascertaining the water line. Nearly all boilers are supplied with both try cocks and glass gauges, and so important is it considered to be correctly informed as to the water line that a third method consisting of a float which is carried on the water surface, is sometimes added to the two named.
Fig. 86.