TRANSACTIONS OP THE SECTIONS. 119. 



any yielding of the pencil will not affect the pressure but the length of the diagram ; 

 the pencil screws backwards and forwards to adjust the pressure on the paper. The 

 diameter of the cylinder of the indicator is two inches and three-quarters, so that a 

 diagram may be obtained seven inches long, which will enable the operator to read 

 off more quickly and accurately than from the ordinary indicator. 



On a Patent Safety Alarum for Steam-Boilers. 

 By Joseph Hopkinson, Engineer, Huddersfield. 



The safety alarum is one of those precautionary contrivances to give warning, 

 should any derangement take place within the boiler, either from want of water, or 

 too much water, or an over-pressure of steam. 



Numerous have been the methods resorted to, to give the alarm and call the 

 attention of the stoker. The steam-whistle has often been applied for this purpose, 

 but so attached to the float-wire that it has been tampered with, and was soon out 

 of order. The safety alarum is free from those objections ; it is similar in principle 

 to the compound safety valve, the one already brought before this Section. It 

 is 60 constructed that when the water in the boiler gets to an extreme distance below 

 or above the level fixed, the alarm instantly commences by a steam -whistle, suflSciently 

 loud to be heard on any part of the premises, which will not cease until the water 

 has gained its proper level. Should the steam get too high, the same whistle com- 

 mences with a loud noise different in its tone, that it is easily distinguished whether 

 it be from want of water or from an over-pressure of steam, and it is out of the 

 power of any person to prevent its operating when any of these casualties take 

 place. 



The simplicity of the apparatus is such that it is not liable to derangement, there 

 being no stuffing-box or float-wire, or parts liable to be tampered with ; it is free from 

 the objection against the alarm-whistle to steam-boilers when connected to the float 

 wire or to a hollow float ; the weight on the valve is locked up inside the dome, and 

 the key in the proprietors' possession, which makes it a complete check, and renders 

 it impossible for the steam to be raised above the proper pressure, or the water to 

 ba below the level fixed, without being detected, for the power of detection is the 

 only real check against wilful and negligent conduct on the part of those in charge. 



On an improved Compound Patent Safety Valve for Steam-Boilers. 

 By Joseph Hopkinson, Engineer, Huddersfield. 

 The valve is intended to provide against two contingences — over-pressure of steam 

 and deficiency of water in the boiler. There is a separate arrangement for securing 

 these objects. The valve is an ordinary flat or concave disc, but there is some 

 novelty in the fittings. All the weight is placed within the boiler and suspended 

 from the underside of the valve ; over the valve is a lever (and fulcrum), and at its 

 extremity a spring balance, which, by a screw, can be regulated to press down 

 heavily or lightly, according to the pressure required. This spring balance, how- 

 ever, operates precisely the reverse of those which may be seen on the top of 

 locomotive engines. The maximum weight to be carried is within the boiler, and 

 the effect of weighting the external lever is only to decrease the internal weight and 

 thus to diminish the pressure of steam at which the valve will open ; should any 

 additional weight be clandestinely applied within when the boiler is being cleaned, 

 the spring balance will indicate the fraud. ITie contrivance for preventing the 

 dangerous consequences of deficiency of water, consists of a long lever, suspended 

 from attachment inside the valve tube. At the end of the long limb of the lever is 

 the float, and at the opposite end a weight which counterbalances it, so long as 

 the float remains immersed in the water ; should there be a deficiency to a dangerous 

 fixed point, the short limb of the lever will push up the safety valve, and thus 

 allow the steam to escape. This is an important feature of the invention and pro- 

 mises to be of service. It thus renders the working of the boiler, when the water 

 therein is deficient, absolutely impossible, and thus affords the most valuable means 

 of preventing steam-boiler explosions hitherto applied. The compound safety valve 

 is wholly beyond the control of the stoker or the engineer. 



