Spray valves

In order to avoid a surge of helium when the spray valve is opened (as this would contaminate the entire environment) it is advisable to install a choke valve to adjust the helium quantity, directly before or after the spray pistol (see Fig. 5.15). The correct quantity can be determined easiest by submerging the outlet opening in a container of v/ater and setting the valve on the basis of the rising bubbles. riable-area flowmeters are indeed available for the required small flow quantities but are actually too expensive. In addition, it is easy to use the water-filled container at any time to determine whether helium is still flowing. 

This step is performed on all fdled units to remove any defectively spraying MDIs such as no-sprays or continuous spray units. Two general methods are used today, an automatic method and a manual method. The automatic unit may employ different techniques, such as light or sound. For example, the sounds of acceptable and unacceptable actuations are programmed and used for testing. Continuous or no-spray valves will sound different from a single-fire acceptable valve. 

The kiln operator selects the appropriate sehedule and adjusts the temperature and humidity as necessary by manipulation of the heating eoils (dry heat) and spray valves (steam), with occasional adjustments to the air inlet and outlet vents, which exchange hot, moist air from the kiln for cold, drier air from outside. The steam line raises and maintains the humidity while the kiln warms up. It should be used only infrequently thereafter as economy in operation depends on making maximum use of the moisture extracted from the lumber to maintain the required humidity in the kiln. As moisture evaporates the humidity rises above the schedule value and the vents open a little to bleed off some of the hot damp air. 

Plant operators have found inventive solutions, on a case by case basis. For example, a double sealing package with intermediate drainage has been tried on pressurizer spray valves, without much success, and a solution with a bellows and a reserve sealing pack with intermediate drainage as also been attempted with limited success due to frequent breaks in the bellows. For the leaks from the penetrations of check valves disc pins, the obvious remedy has been to weld a cap around the penetration. 

Open spray valve Mental belief of SGTR and reactor tripped... 

Set Ho. 2 - The second set of gages will automatically turn the fog Spray valve off should the pressure decay to about 3.2 inches of water gage. 

It is not possible to use reset in two controllers which operate on the same input. So proportional plus derivative is used to manipulate the spray valve. In this way, the valve will operate around a position determined by the bias set into the controller. The lead lag unit is used to... 

Water-spray valves and shutdown stations should be located so that they are at the battery limits in a weU-Ughted and easily accessible area. 

The secondary-side reactor operator ran to his station and immediately increased the speed of the No. 2 main feedwater pump to compensate for the decrease of feedwater flow from the No. 1 pump. The primary-side operator had already opened the pressurizer spray valve in an attempt to reduce the pressure surge resulting from the heatup of the reactor coolant system due to a decrease in feedwater flow. 

The plant s integrated control system attempted automatically to reduce reactor/turbine power in accordance with the reduced feedwater flow. The control rods were being inserted into the core and reactor power had been reduced to about 80%. At the same time the primary-side reactor operator held open the pressurizer spray valve in an attempt to keep the reactor coolant pressure below the high pressure reactor trip set point of 2300 psig (normal pressure is 2150 psig). However, the reduction of feedwater and subsequent degradation of heat removal from the... 

The average reactor coolant temperature increased at thi rate of about 4oF/minute for about 12 minutes. The system pressure also increased steadily until the operator fully opened the pressurizer spray valve (at about 1 42 a.m.). The spray reduced the steam volume in the pressurizer and... 

The operator did not know that the PORV had failed. He believed the RCS depressurization was due either to the fully open pressurizer spray valve or to the feedwater flow to the steam generators. He closed the spray valve and the PORV block valve as precautionary measures. But subsequent analyses showed that the failed PORV was responsible for the rapid RCS depressurization. Two minutes later, the reactor operator opened the PORV block valve to ensure that the PORV was available. Fortunately, the PORV had closed by itself during the time the block valve was closed. The failed PORV was the ninth abnormality that had occurred within 15 minutes after reactor trip. 

Spray valves benefit from three-stage microprocessor control, which manages prespray, spray and post-spray. Continuous spray can be initiated and terminated with a continuous signal. Atomizing air pressure also must be tightly controlled to ensure even fluid dispersion. 

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