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Publication Date: 2003-Dec-18
Document File: 15 page(s) / 49K

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The Prior Art Database

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Patrick Sullivan: INVENTOR [+2]


A low pressure tank is disclosed having: an upper section with a sloping surface; a port on the surface; a gable housing covering the port and having a front face oriented generally vertically; an aperture in the front face; a door aligned with and covering the aperture in the front face, and a door hinge above and aligned with the door and horizontally offset from said front face.

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This is the abbreviated version, containing approximately 15% of the total text.

storage tank in a pulp processing plant having freeze resistant overflow and over-pressure/Under Pressure doors

[0001]                      FIELD OF THE INVENTION

[0002]                      The present invention relates to overflow, pressure relief and vacuum relief ports on low-pressure chemical tanks. In particular, the invention relates to tanks, such as pulp storage tanks, in pulp processing plants that have pressure relief, vacuum relief and/or overflow relief doors.

BACKground of the invention

[0003]                      Low-pressure tanks are common in many chemical and industrial processes. For example, a pulp storage tank is typically used to store pulp at various locations within the system. These tanks can be used in storing various compounds including chemically produced cellulosic fibrous pulp, mechanically produced pulp, recycled fiber, etc. The tanks are typically used after the cellulosic fibrous material has been processed in a digester, using the chemical process both batch and continuous, mechanical process, thermo-mechanically processes, or material which has been re-fiberized in a recycle facility.

[0004]                      Storage tanks typically have outlets around their upper periphery that provide overflow fluid relief, and vacuum or over-pressure relief. These relief outlets are typically openings in the upper housing of the storage tank which allow fluid to flow out of the storage tank, when the fluid level in the storage tank becomes excessively high. In addition, these openings can be used to draw air into the tank for vacuum protection. These openings may be covered by gables (also known as dormers) on the top of the storage tank. The gables have an open vertical front face with a hinged door. Each overflow opening has a door that remains shut over the overflow opening until fluid fills the tank and flows out of the opening. The doors on the overflow openings prevent debris, rain, snow and ice from falling into the storage tank. The doors also reduce the amount of ambient air drawn into the tank as well as serving to prevent fluid splashing within the storage tanks from spilling out of the tank during non-overflow conditions.

[0005]                      Similarly, storage tanks may have one or more openings for vacuum or pressure relief. The tank operates at near atmospheric conditions. An over- or under-pressure condition may be where the pressure in the tank is either greater than atmospheric pressure or less than atmospheric pressure. A greater than two psi pressure (or 4 inches of water vacuum) variation in a storage tank may be sufficient to damage the tank or result in a dangerous operating condition. The pressure relief openings are normally closed by doors on the storage tank. If the pressure in the storage tank becomes excessive, the pressure forces the doors open and gases and/or fluids are allowed to flow out of the pressure relief apertures on the tank.

[0006]                      The metal doors on the overflow fluid, e.g., front face of the gables, and pressure relief openings tend to be noisy when they clang against th...