HARDWARE (Aug93)       furnace


hardware --- Real Quick Overview of Oven Hardware


The Oven is about 9.5 m. or 384 in. diameter, by about seven feet tall inside. There are 252 heaters covering the interior which can deliver over 193 kW. We can heat the Oven to 1200 C., and can hold its temperature constant to +- 0.5 C. in the anneal range. It can spin at 10 rpm for days on end.


The Oven is composed of several parts and subsystems, for which it is useful for us all to use the same names. The heated interior cavity of the Oven is formed by installing the Shell, consisting of Lid, Cone, and Walls, upon the Hearth. The Hearth is the floor of silicon carbide plates. The cavity is heated by Heaters on all surfaces. On the Shell, there are two heater Panels wired together in series to form each Heater circuit. In the Hearth, each Heater is a single coil of wound kanthal wire laying in grooves beneath the silicon carbide plates. There are two sets of Heaters in the hearth, the Primary Heaters are larger, heavier, coils designed to deliver maximum power, to heat to high temperature. The Anneal Heaters are smaller, more delicate coils that reside beneath the Primaries. They are for low power slow cooling, to deliver smoother, more controlled heat. Each Heater circuit is designated by its three-digit PFE number. PFE stands for Power panel (0-9), Fase (sic) in its panel (0-2), and Element number (0-29). Outside of the Shell, or under the Hearth, there is a Junction Box associated with each heater, with its PFE in big yellow numbers. A thick black Twistlock Cable emerges from each Junction Box, and goes to the appropriate Twistlock Recepticle for each Heater. Power to each Twistlock Receptical is switched by one Element in a Power Panel. Each Element is composed of an solid state relay, or SSR, and its associated fuse and circuit breaker. There is a Voltage Sensor (VS), a Local Current Sensor (LCS), and a Remote Current Sensor (RCS) associated with each Heater. The VCSs and LCSs are checked to see that the SSRs are switching correctly, and the RCSs are checked to assure that the power is going to the correct Heater. Power from the outside world is supplied to the nine Power Panels (PP0-8), through large Slip Rings, which allow juice to flow while the Oven is spinning. This power comes from some combination of four sources, Main SwitchBoard 0 (MSB0), Main SwitchBoard 1 (MSB1), Generator SwitchBoard 0 (GSB0), and Generator SwitchBoard 1 (GSB1). MSB0 is a 750kVA line from TEP Co., MSB1 is a 500kVA line, and GSB0 &1 are from two 500kVA generators.

Scattered around the Oven are lots of Thermocouples, or TCs, which read temperature. TCs are thin metal tubes with two special metal wires inside that are joined at the tip of the tube. It is filled with an insulating powder. Each TC has a color-coded connector on the end with three pins. Our normal type-N TCs are orange. Each TC is plugged into a special gold or orange TC Connector Cable which is designated by a four-digit DNTX number. DNTX stands for DCU (0-5), DCU card Number (0-5), TIC select number (0-3), and channel (X) on the TIC (0-4). Not every possible DNTX (or PFE) number is currently in use. The Connector Cable connects each TC to its Isothermal Junction Box, or IJB. Each IJB is a copper block with ten TC junctions and two thermistors attached to it, thermally isolated in a foam-rubber filled box. Each IJB is serviced by two TICs, whose DNT numbers are emblazoned on the cover of the box. The TICs live in seven Temperature Instrumentation Panels, or TIPs. Information from the TICs is directed through six Data Conversion Units, DCU 0-5, to the on-board computers.

The Oven is propelled around by two independent Drive systems, Drive 1 and Drive 2. Each Drive consists of a 40 horsepower motor, the electrical system to start and protect them, a gearbox, and pinion gear. Both Drives are controlled by the Rotation Control Panel

There are three computers which live aboard the oven to read and process temperature information, and to control the heaters. They are CPU0, CPU1, and CPU2. Besides sending instructions to the Power Panels to switch Heaters on and off, they also check to see what the Voltage (adcV), and Current draw (adcC), are for each Fase, and the current on the Neutral (adcN), of each Power Panel. In addition, the CPU sisters communicate with the two Control Room Computers, Crater and Dorado, which store data and serve as interface with you, the Oven Pilot.


All points of interest on the oven are described by regular cylindrical coordinates R, radial distance in inches from the Oven's center of rotation, Theta (T), measured clockwise (when viewed from above) in degrees around the circle from 0 to 360, and Z, measured in inches above or below the Hearth, which is defined as Z=0. The Heaters position is the approximate center of their areas, and a TCs position is the coordinates of its tip. For example: Heater 108 is at (192,98,36). This puts it in the upper wall section of the Shell, about quarter way around from zero degrees. and three feet up from the Hearth.

There are ports for four Video Cameras in the Cone at 70, 100, 215, and 340 degrees (not all cameras may be installed at any given time). Lights for the Video are mounted in the walls at 85, 175, 265, and 355 degrees. Each of the Shells Heaters Twistlock cable drops from its Junction Box to one of the main beams where they plug into their assigned Twistlock receptacles. These are numbered for our convenience, so a Heater has a Beam and Twistlock number to describe where it plugs in. For example: our friend Heater 108 has Beam 090, Twistlock 19 as a home. In the Hearth, each Heater circuit may connect to either the Primary (PRI) heater coil, or the Anneal (ANL) coil. This choice is made by changing the Twistlock cable which comes from the beam receptacle to one of two marked receptacles on the appropriate transition box. These boxes are hung on unistrut rails between the beams.

All of the information from the Shell IJBs and the Heater RCSs comes down the thick black cables with braided sheaths to plug into their appropriate transition boxes, and hence to the TICs and PPs.

The Oven electronics are arrayed around the carousel at ground level (Z=-60), with the Power Panels from Theta = 40 to 160 degrees, the access door into the pedestal at 180 deg., Rotation Control Panel at 200 deg., Temperature Instrumentation Panels from Theta = 220 to 310 deg., Interface Panel at 320 deg., CPU2 at 340 deg., CPU1 at 350 deg., and CPU0 at 10 degrees. All of these Panels shall be clearly marked.

Inside the access door there is the Pedestal, upon which is borne the entire Oven structure. There is a large crossed-roller bearing atop the Pedestal, the bottom race of which is toothed on the outside. The Drives turn their Pinion Gears around this ring. Emerging from the floor outside the Pedestal are nine large conduits which carry the power through the Pedestal walls to the nine sets of Sliprings, which are stacked on a shaft along the Ovens rotation axis. Below the large Power Sliprings (deep in the pit) are two sets of much smaller sliprings which carry low voltage housekeeping power, and information. At the bottom of the pit there is also a sump pump... just in case.


There exist a number of maps which show the location of every Heater, TC, IJB, Camera, and Light. These are located in the control room, the electronics shop, and out on the wall near the Oven. These are all subsets of a master AUTOCAD drawing called HEAT.DWG, copies of which reside on the Video Computer, and on floppy in the box nearby. This drawing has many layers which contain lots of obscure but useful information. There are also drawings which show oven wiring in schematic representation. (need names and numbers here.. see Index to Oven Schematics below) 4/22/91 DMW




duties, clocks, schedules, wait_states, zones, menus, furnace