51 UNLOADING
Open the discharge line control valve part way. Gradually open one of the product valves. Adjust the line control valves to maintain a steady tank pressure. As tank pressure decreases, close the line control valve a little bit to increase the tank pressure. If the tank pressure is increasing, open the line control valve wider to reduce the tank pressure.
The top of the hopper is not intended as a heavy work area. The ladder and walk surface are intended to provide access only when other facilities are not provided. Personnel should never be on top of the hopper while it is pressurized. The working line pressure of the unit is 14.5 psi. If there is a discrepancy between the gauges, check the system for clogs.
As the product level reaches within a few feet of the product valve on the hopper being unloaded, the pressure will begin to fall off. Close this product valve and open and adjust another one. Cycle through the hoppers in this manner in order to have the smoothest possible unloading.
All of the check valves must be operational to prevent product backup into the supply lines. Do not exceed the working pressure of the system. Check and maintain the vacuum and pressure relief devices regularly. Do not close the domes after cleaning until the hopper has cooled. (see TTMA RP No. 84) Opening the product discharge valve too fast may cause line plugging. When unloading, make sure all couplings and connections are secure to prevent spillage and material loss. Make sure the relief valve is operational and is set to operate at 5 psi over the operational pressure of the tank. The valve
NOTICE
NOTICE
NOTICE
As the hoppers start to empty out, it may become necessary to close the line control valve down further to divert more air to the tank.
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