Document 1Q4NyZwvVL11NXXrrJO6w2xKo

American Society of Heating and Ventilating Engineers Guide, 1932 , steam leakage through the discharge valve due to unequal expansion of the valve and seat and the sticking of moving parts. The discharge from a float trap is usually con tinuous since the height of the float, and consequently the area of the outlet, is propor tional to the amount of water present. Bucket Traps. Bucket traps are of two types, the upright and inverted, and although they are both of the open float construction, their operating principle is entirely different. In the upright bucket trap, the water of condensation enters the trap and fills the space between the bucket and the walls of the trap. This causes the bucket to float and forces the valve against its seat, the valve and its stem usually being fastened to the bucket. When the water rises above the edges of the bucket it flows into it and causes it'to sink, thereby withdrawing the valve from its seat. This permits the steam pressure acting on the surface of the water in the bucket to force the water to a discharge opening. When the bucket is emptied it rises and closes the valve and another cycle begins. The discharge from this type of trap is intermittent. In the inverted bucket trap, steam floats the inverted submerged bucket and closes the valve. Water entering the trap fills the bucket which sinks, and through compound leverage opens the valve and the trap discharges. It is impossible to install a water gage glass on an inverted bucket trap, but if visual inspection is necessary, a gage glass can be placed on the line leading to the trap. No air relief cocks can be used, but this is Chapter 10--Devices for Handling Condensate and Air . a by-pass around the main trap. Sometimes this auxiliary air trap is an integral part of the trap. Blast-type thermostatic traps are sometimes used on vacuum heating systems for connecting old one or two-pipe gravity systems ini parallel Fig. 2. Method of Discharging High-Pressure Apparatus into Low-Pressure . Heating Mains and Vacuum Return Mains through a Low-Pressure Trap unnecessary, as the elimination of air is automatically taken care of by air passing through: the vent in the top of the inverted bucket regardless of temperature. Thermostatic Traps. Thermostatic traps are of two types, those in which the discharge valve is operated by the relative expansion of metals, and those in which the action of a volatile liquid is utilized for this purpose. Thermostatic traps of large capacity for draining blast coils or very large radiators, are called blast traps. Tilting Traps. With this type of trap, water enters a bowl and rises until its weight over-balances that of a counter-weight, and the bowl sinks to the bottom. As the bowl sinks, a valve is opened thus admitting live steam pressure on the surface of the water and the trap then discharges. After the water is discharged, the counter-weight sinks and raises the .bowl, which in turn closes the valve and the cycle begins again. Tilting traps are necessarily intermittent in operation. They are not ordinarily equipped with glass water gages, as the action of the trap shows when it is filling or emptying. The air relief of tilting traps is taken care of by the valves of the trap. Thermostatic traps are generally used for draining radiators and heaters, except for very large capacities where bucket, float or blast-type thermostatic traps are used. Thermostatic traps for this service usually pass both condensate and air and in the case of float and upright bucket traps the air is usually relieved through an auxiliary thermostatic trap in i 174 with vacuum return line systems, in which case the blast-type thermo static traps should not be provided with auxiliary air by-pass, as the action of this will allow the vacuum to draw air into the old system through its air valves, especially when the steam is wholly or partially cut off. The air from the returns of such old systems should be relieved just ahead of the traps by means of quick-venting automatic air valves, 175