Vacuum sizing tank

The outside diameter of the pipe may be calibrated either by an internal air pressure of 1.3 to 2.0 bar, or by external calibration in a vacuum sizing tank (Fig. 6.17) operating at a pressure of 0.3 to 0.5 bar. For calibration by internal pressure, the diameter of the die ring is made approximately equal to the internal diameter of the finished pipe. For vacuum tank calibration, the die ring is made up to 25% larger and the haul-off is set for a wall thickness drawdown of up to 30%. 

Figure 6.17 Vacuum sizing tank used for pipe and tube extrusion. ...

Note This data pertains to extrusion lines using water-filled vacuum sizing tanks. ... 

PTFE membranes are highly hydrophobic and, therefore, are used as air filters. Air filters have to be highly hydrophobic to avoid water blockage due to moisture or condensate, especially after steam sterilization of these filters. Water blockage could be detrimental, if the filter is, for example, used in a tank venting application to overcome condensation vacuum of a non-vacuum resistant tank. If the filter would not allow a free flow of air into the tank, it may implode. Therefore, vent filters for this application have to be chosen and sized with care. PTFE membranes are also highly mechanical and thermal resistant, which is required, because such filters are used over several... 

Tubing and pipes Sizing rings and vacuum water tank... 

Fig. 10 Tubing vacuum water-bath calibration and take-off (1) tubing/pipe die (2) molten tube extrudate (3) baffle (4) vacuum water tank (5) sizing ring (6) solidified tube and (7) puller.

A small container of mineral spirits mounted above the sizing sleeve of a vacuum cooling tank so as to permit a slow, dropwise addition of mineral spirits on the hot vinyl profile just before entering the vacuum sizer will often keep sizing sleeves clean. 

Nutsche Filter. The nutsche filter (Fig. 8) is simply an industrial-scale equivalent of the laboratory Buckner funnel. Nutsche filters consist of cylindrical or rectangular tanks divided into two compartments of roughly the same size by a horizontal medium supported by a filter plate. Vacuum is apphed to the lower compartment, into which the filtrate is collected. It is customary to use the term nutsche only for filters that have sufficient capacity to hold the filtrate from one complete charge. The cake is removed manually or sometimes by reslurrying. 

NFPA 30 and API Standard 2000 provide gmdance for design of overpressure protec tion involving storage tanks that operate at or near atmospheric pressure. In particular, NFPA 30 focuses on flammability issues, while API 2000 addresses both pressure and vacuum requirements. The ASME code (Sections I and TII) and API RP 520 are the primaiy references for pressure rehef device sizing requirements. 

Pressure-Vacuum Relief Valves For apphcations involving atmospheric and low-pressure storage tanks, pressure-vacuum relief valves (PVRVs) are used to provide pressure relief. These units combine both a pressure and a vacuum relief valve into a single assembly that mounts on a nozzle on top of the tank and are usually sized to handle the normal in-breathing and out-breathing requirements. For emergency pressure rehef situations (e.g., fire), ERVs are used. API RP 520 and API STD 2000 can be used as references for sizing. 

Latent heat of vaporization 169 BTU/lb Tank size (nominal) 15 diameter and 20 high Operating pressure 1.5 oz/in.2 Maximum allowable tank pressure 3.5 oz/in.2 Maximum allowable vacuum 1.0 oz/in.2 Relief valve settings ... 

Where process, safety, and environmental considerations permit, vacuum protection may be provided by properly sized ever-open vents. Alternatively, active protective devices and systems are required. Vacuum breaker valves designed to open and admit air at a predetermined vacuum in the vessel are commonly used on storage tanks, but may not be suitable for some applications involving flammable liquids. Inert gas blanketing systems may be used if adequate capacity and reliability can be ensured. Where the source of the vacuum can be deenergized or isolated, suitably reliable safety instrumented systems (e.g, interlocks) can be provided. 

For more efficient deinking, flotation must be used. This is considerably more complex, and the mechanism by which it works is still somewhat speculative. It is necessary to make the detached ink particle hydrophobic so that it can adhere to an air bubble and be removed by flotation. For this to happen, it appears to be necessary for the particles to be in the size range 10—150 jum. The processs consists of a cell or tank with a high speed agitator to induce a partial vacuum which causes air to enter the system in the form of small air bubbles, these carry the ink particles to the surface. 

Document that the reservoir conforms to purchase specification and invoice. Verify and document that the vessel meets or exceeds the pressure rating (vacuum) specified in the purchase specifications. Perform vacuum hold tests on the tank and document. Acceptance ID tests will vary with the size of the system. A positive pressure test is often done in order to find leaks. Perform and document cleaning procedures used prior to placing the vessel in service. This completes the normal testing done on the tank prior to joining it to the vacuum system. 

Fig. 5. Vacuum calibrator for pipe and tubing extmsion A, molten tube from die B, tank C, hinged cover with gasket D, sizing rings E, circulated and temperature controlled water F, water level G, vacuum and H, inside of pipe open to atmospheric pressure (15).

Calculations were made. Engineers figured that a vent of about 30 inches (76 cm) in diameter would have prevented the destructive vacuum from collapsing the tank during the ammonia absorption incident. A giant-sized vent was impractical for this installation, hence they concluded that water should be added slowly through a restrictive orifice. [8]... 

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