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chamber belowground. The pressure chamber also has an isolation chamber and plumbing to be sure that gas from the process zone is removed from the exhaust and does not flow to the heater zone.

The high-pressure generator uses air to drive a large pis- ton connected directly to a smaller piston, which pressur- izes the gas used in the chamber. These simple pumps op- erate at pressure ratios between 10 and 1000 and are available with maximum pressures up to about 1,400 MPa. The piston-and-cylinder mechanisms of the pres- sure intensifiers can be seen in the high-pressure genera- tor system pictured in Figure 7-1.

The control console has an instrument panel with typi- cal industrial temperature and pressure control and recording instrumentation, as shown in the right of Figure 7-1. The console usually includes a computer and a keypad for entering data required to control the operation of the press. Isostatic presses can be quite large. A top and side view, respectively, of two different presses are shown in Figures 7-3 and 7-4. Notice the thick-walled pressure vessel and the large threaded plug in Figure 7-3. Another isostatic press is shown in the background of Figure 7-5.

Appe r nce ( s p ck ged): The components of an iso- static press system are likely to be shipped separately and assembled at the final work destination. Packaging varies with the requirements of the purchaser, but wooden pallets and crates with steel banding and rein- forcement are common. Two wooden crates containing components of an isostatic press system are shown in Figure 7-6; a different crate for a similar press is shown in Figure 7-7. Larger chambers are very heavy because of the thick walls and may be packaged in a cylindrical wooden crate with wide steel banding, as shown in Figure 7-8.

Addition l Inform tion: The distinction between a normal hot isostatic press and one modified for use in pyrolytic densification is that decomposition does not occur in the former and does in the latter. To avoid the carbon deposition on the heaters, which would other- wise cause an electrical short, the heater chamber for densification has plumbing connections and controls to pipe carbon decomposition products directly from the heated zone out to gas handling equipment.

Figure 7-3: A very large isos a ic pressure vessel and hreaded plug.

Pho o Credi : Engineered Pressure Sys ems, Inc.

Figure 7-4: Side view of a large isos a ic press.

ITEM 7

7-5

Pho o Credi : A Handbook for he Nuclear Suppliers Group Dual-Use Annex. Repor No. LA-13131-M (April 1996).

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