GB140713A - Improvements in or relating to superheaters - Google Patents

Abstract

140,713. Yarrow, H. E. Oct. 20, 1919. Overheating of superheating-tubes, preventing. -In a steam-generator provided with a superheater, means are provided for automatically controlling the temperature to which the superheater is subjected, dependent upon the difference of steam pressure between the inlet and outlet of the superheater. The superheater tubes E, Fig. 1, are shown in connexion with a Yarrow boiler having a steam drum A and water drums B, B<1>. An oil burner G is supplied with oil through a tube H, which is controlled by a regulating piston valve K. The rod K<1> of the piston K may be in alinement with, or connected to, the rod M<1> of the piston M, which works in a cylinder L, and may be pressed downwards by a spring P. The upper and lower sides of the piston M are connected by pipes N, O to the outlet and inlet ends of the superheater respectively. When the amount of steam flowing through the superheater is insufficient to prevent overheating of the tubes, the pressure difference on the two sides of the piston M is insufficient to prevent the downward movement of the piston M and consequently the piston K, and the supply of oil from the pipes I to the pipe H is cut off. If the piston-rods M', K<1> are not rigidly connected, the restoration of the oil supply is effected manually. The piston K may be arranged to cut off the oil supply only partially instead of completely, so as to maintain a sufficient temperature, especially when there are several burners G, in which case some of the burners are left unaffected. In a modification, Fig. 2, the control piston M operates a valve Q controlling the passage from the lower side of the leaky piston K to the relief pipe K<0>. When the valve Q is opened on a decrease in the pressure difference at the two ends of the superheater, the pressure in the oil-supply pipe I forces the piston K down and closes the valve R leading to the pipe H and thence to the burners. In another modification, Fig. 3, the piston M is maintained by the steam pressure in its highest position, where it closes the valve Q' and interrupts the passage of steam from the pipe N to the pipe S‹ and thence to the cylinder U. When the pressure difference on the two sides of the piston M falls to a predetermined value, the valve Q<1> opens, and the piston T is forced down, thus closing the valve K. In another modification, the two ends of the superheater are connected to the supply and exhaust of a Pelton wheel which drives a pump which supplies the oil to the burners. The supply of oil is thus varied according to the pressure difference of the steam at the two ends of the superheater.