Method and apparatus for taking metal samples

A method and apparatus for storing and releasing individual probes from a drop mechanism or probe rack which stores a number of these probes in a ready position for future use. The probe rack includes a plurality of radially projecting pins which are connected to, or comprise the piston rods of, a plurality of radially extending air cylinders. The individual probes are each provided with hanger loops which are suspended on the support pins in a ready position. Each of the probes may have a thermocouple assembly, or an oxygen sensor, or some other type of sensor. When it is desired to drop or release one of the probes, a switch is closed on a remotely located control panel to energize the appropriate air cylinders to withdraw the pin from the probe loop and allow the selected probe to drop into the additive chute of the vessel. The descent of the probe into the chute and through the chute into the molten metal bath is guided by the electric cable which has wires to connect the sensor to the instrumentation involved. The method includes dropping the probe so that an elongated pipe intermediate the length of the probe penetrates the slag and receives a skull of steel which adds to the weight of the second weight to add in maintaining the probe in an upright position.

FIELD OF THE INVENTION 
The invention relates to molten metal sampling apparatus for taking 
measurements in a molten metal bath. 
BACKGROUND OF THE INVENTION 
In the basic oxygen process for making steel, the furnace typically 
includes a tiltable vessel. A hood is located over the open top or mouth 
of the vessel for conveying fumes and smoke to a waste collection and 
purification chamber. Various devices have been involved for accessing the 
interior of the furnace to take oxygen readings and temperature 
measurements without turning the vessel partially on its side. U.S. Pat. 
No. 3,717,034 discloses a sublance arrangement which enables insertion and 
retraction of sampling equipment with a permanent installation. These 
types of sublances are very expensive and cost several million dollars to 
install. Moreover, they take considerable time to use increasing the time 
of completing a "heat". 
Typically the water cooled hood for the furnace is provided with a chute 
leading into the furnace for introducing various additives which may be 
required during the steel making process. The chute enables access to the 
interior of the vessel. Measuring devices are available which involve the 
use of expendable thermocouples which are weighted and supported only by 
an electrical cord. After use the thermocouple unit and cord are consumed 
by the high temperature bath. U.S. Pat. No. 3,374,122 is an example of an 
expendable sensor which is lowered through the chute into a metal bath. 
The disclosure in U.S. Pat. No. 4,881,824, of which applicant is a 
co-inventor, provides an improved expendable probe. The present invention 
provides apparatus for convenient use of this probe with the operator 
located at the furnace control station at the pulpit. 
SUMMARY OF THE INVENTION 
The invention provides a method and apparatus for storing and releasing 
individual probes from a drop mechanism or probe rack which stores a 
number of these probes in a ready position for future use. The probe rack 
includes a plurality of radially projecting pins which are connected to, 
or comprise the piston rods of, a plurality of radially extending air 
cylinders. The individual probes are each provided with hanger loops which 
are suspended on the support pins in a ready position. Each of the probes 
may have a thermocouple assembly, or an oxygen sensor, or some other type 
of sensor. When it is desired to drop or release one of the probes, a 
switch is closed on a remotely located control panel to energize the 
appropriate air cylinders to withdraw the pin from the probe loop and 
allow the selected probe to drop into the additive chute of the vessel. 
The descent of the probe into the chute and through the chute into the 
molten metal bath is followed by the electric cable which has wires to 
connect the sensor to the instrumentation involved. 
The electric cables for each probe are packed in separate canisters. The 
canisters are supported by a radially extending fixed pin on the probe 
rack which extends through loops fixed to the canisters. The length of 
cable needed to allow the probe to reach the molten metal is packed into 
the interior of the canister. When the probe is released the weight of the 
probe will withdraw the packed cable from the interior of the canister. 
The canisters are readily mounted to the probe rack and the electrical 
connections for each probe are made by simply plugging the free end of the 
cable into electrical outlets arranged around the probe rack. 
The release of the probes from the probe rack can be controlled either from 
the drop rack itself or from the pulpit. The control panel at each 
location is provided with indicator lights, such as light emitting diodes, 
to indicate which probes are ready and that a probe has been released. 
It has been found that it is desirable to adhere a layer or skull of steel 
on the elongated pipe weight which is exposed between the float and the 
lower weight. The added weight helps hold the probe submerged in the melt 
at the desired depth for accurate readings. The steel skull is acquired by 
dropping the probe in a free fall from a sufficient height to momentarily 
penetrate the steel below the slag before the buoyant forces buoy the pipe 
above the slag-steel interface into an equilibrium position.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Although the disclosure hereof is detailed and exact to enable those 
skilled in the art to practice the invention, the physical embodiments 
herein disclosed merely exemplify the invention which may be embodied in 
other specific structure. The scope of the invention is defined in the 
claims appended hereto. 
In the drawings, FIG. 1 discloses probe drop apparatus 10 with the 
individual probes 12 and 14 supported by a probe rack 16. The probes 12 
and 14 can be provided with sensors such as thermocouples or oxygen 
sensors in accordance with U.S. Pat. No. 4,881,824, the entire disclosure 
of which is incorporated herein by reference. 
The probes are positioned over an access hole to the chute 17 which is 
typically employed to add steel making ingredients through the conduit 18 
into the metal bath 20 contained by a vessel 22. Conduit 18 and chute 17 
are supported conventionally on the hood 24 of the steel making vessel 22. 
An oxygen blowing probe 26 is also shown in FIG. 1. 
In accordance with the invention, the chute 17 is provided with a gate 
valve 28 operated by power cylinder 29 to seal the chute to prevent toxic 
gases or corrosive gases from deteriorating the drop rack and components 
thereof. 
The probe rack 16 is supported on an adjustable boom arm 30 which is 
adjustably received in a sleeve 32, which is in turn rotatably supported 
by a sleeve 34 on a support post 36. Sleeve 34 can be pinned by a pin 38 
receivable in any of a plurality of apertures 21 in post 36 in the 
appropriate angular position to register the probe rack with the chute 17. 
Means are provided for supporting and releasing the probes 12 and 14. As 
shown in FIG. 5, the means comprises a probe drop rack or a boom head 16 
connected to the .boom 30. Boom head 16 includes two spaced walls 40 and 
42 connected by a cylindrical peripheral wall 44 to define a chamber 46 
which contains and supports elements of the drop mechanism. The probes 12 
and 14 are provided with an eye 50 with an aperture 52 (FIGS. 3, 4). The 
eye 50 is secured in the end of the probe 12. The apertures 52 interfit 
with retractable pins 56 on the drop rack 16. As shown in FIG. 5, 6 the 
pins 56 are connected to the piston 58 of an air cylinder 60. The air 
cylinder is provided with inlet and outlet ports 62, 64 to either advance 
the pins 56 to the advanced position shown in FIG. 5 to support the probes 
12, 14 in a really position, or retract the pins 56 to the retracted 
position shown in FIG. 3 when the probe is released. The pins 56 extend 
through apertures 66 in the cylindrical side wall 44 and through washers. 
or bearing surfaces 69. The eyes 50 are offset from pipe end 71 as shown 
in FIG. 5. 
FIGS. 9, 10 and 11 show a modified embodiment of a probe in which a 
paperboard sleeve or float tube 51 is arranged over the end of a pipe 53 
which extends to or is connected to the head containing sensor's or a 
sampler. A wire 55 extends through the sleeve 51 and pipe 53 to 
electrically connect the sensor head with instrumentation. An aperture 59 
is provided in the side wall of sleeve 51 to receive a pin or plug 52 
welded to the pipe 53. An aperture 57 is provided to receive pin 56 to 
support the probe on drop rack 16. The use of the paperboard aperture 57 
rather than the eye 50 reduces the likelihood that the wire 106 will be 
burned off when the probe is dropped in the bath thus breaking the circuit 
before a reading is obtained with the sensor. Eye 50 and exposed pipe end 
71 in FIG. 5 can cause slag to stick to these metal parts at the upper end 
of the probe with the concentration of hot metal burning through the wire 
over a brief period of time. 
Hold down arms 70 are pivotally connected at 72 to the top wall 40 and have 
a depending portion 74 which is aligned to engage the projecting pins 56. 
The arms 70 are manually placed in position when loading the rack and the 
depending portion 74 holds the eye in place on the pin 56 until the power 
cylinder 60 is energized to retract the pin and release the probe 12 or 
14. 
Electric control means 84 are provided at the probe rack and also a remote 
control means 86 is provided for operation from the pulpit. The circuit 
includes indicator lights which indicate when a unit is ready to be 
dropped and that it has been dropped. When a probe is installed and 
plugged into the receptacle as hereinafter described on the drop rack, a 
light on both the upper control box and the pulpit drop control lights 
indicate that the unit is in place and that the thermocouple is good and 
operating. 
While any suitable control box could be used, FIG. 7 shows an example of 
such a control box as would appear both at the probe rack and at the 
pulpit. It would be advantageous to have the same control box at both 
locations so as to fully enable an operator in either position to perform 
all control functions. As shown in the example in FIG. 7, each control box 
84, 86 may have one "Ready" light, such as a green light, and one "Used" 
light, such as a red light, for each probe. While the types of probes may 
be divided or allocated in any suitable way, the types of probes shown in 
the example in FIG. 7 are divided into two types, Oxygen probes and 
Temperature probes, with banks of indicator lights arranged to relate to 
each type. A separate "Drop" button 88 is provided for each type of probe. 
Shown in the schematic of FIG. 8 is a control circuit 90 constructed 
according to a preferred embodiment of the invention. According to the 
invention, as indicated above with respect to the control panel 84, 86 
shown in FIG. 7, the circuit 90 includes two identical control units CU 
and CL, for the upper and lower control panels respectively, and one probe 
circuit 92 for each probe 12, 14. The probe circuits 92 are connected in 
series as shown in FIG. 8 to both control units CU, CL. Each of the 
control units CU, CL includes a normally open push button switch SW1 which 
corresponds to the drop button 88 for a particular type of probe a- 
indicated on the control panel 84, 86 of FIG. 7. 
In accordance with the invention, means are provided for storing and 
releasing electric cable connected to the probes 12 and 14. In the 
disclosed construction of FIG. 5, the means includes canisters 94 which 
can be cylindrical in shape and which include a support eye 96 adapted to 
receive a radially projecting support hook 98 secured at 100 to the top 
wall 40a of the drop rack housing. The support loops 96 are secured to the 
top of the canister. Electric cable means 106 are wrapped around a cleat 
102 to secure the wire to the rack. Cable means 106 terminates in a plug 
107 which is plugged into- an electrical outlet 108 for connecting an 
electric circuit to the probe for the instrumentation associated with the 
probe. The cable length 110 which will extend from the drop rack into the 
molten metal is manually stuffed into the canister below the cross member 
104. A paper or frangible bottom 103 can be employed to retain the cable 
in the canister until the probe is dropped. When the probe is released the 
weight of the probe will pull the cable loops from the canister as the 
probe heads toward the molten metal bath. The probes can be prewired to 
the canister assemblies so that the probe and cable canister are installed 
as a unit for replacement. 
Referring now again to the control circuit 90 shown in FIG. 8, line power, 
such as at 110 volts, is supplied at power input terminals I1 and I2. This 
line voltage is stepped down to 24 volts at stepdown transformer TRl. When 
a probe 12, 14 is installed on the drop rack 16 and the plug 107 is 
plugged into the A outlet 108 or first probe outlet, the probe is 
electrically connected to the circuit 90. Since the probe has an internal 
closed circuit, this connecting action closes contacts Cl and C2 of the 
outlet 108. This in turn energizes relay R1A, switching contacts R1A1 and 
R1A2 from their normally closed contacts to their normally open contacts, 
thereby energizing the green indicator GA. Hence at the control panel 84, 
86 the first green light GA will light up. The rest of the green lights 
will light up when probes are plugged into their respective outlets 108, 
indicating that the probes are attached and ready to be dropped. 
In operation of the units, then, referring to FIGS. 7 and 8, pushing the 
drop button 88 on the control panel 84, 86 closes a switch SW1 (FIG. 8), 
which energizes a time delay relay coil TD besides energizing the coil of 
locking relay R1. Contacts TD remain open for a time, though contacts R1 
close to maintain coil TD energized. At the same time, coil R2A is 
energized, as is the solenoid SOLA, in turn energizing the power cylinder 
which directly releases the probe from the rack. Coil R2A closes contacts 
R2A1 and R2A2. Contacts R2A1 maintain the green light GA on even though 
the closed circuit of the probe may open. Contacts R2A2 energizes coil 
R3A. In turn, coil R3A switches contacts R3A2 from the normally closed 
position at outlet contact Cl to the normally open position, so that R3A 
in effect locks itself in, remaining energized as long as its own contacts 
are closed. In addition, contacts R3A1 energize coil R5A. When this 
happens, contacts R5A, at the very bottom of the diagram, switch over to 
connecting the probe to be connected to sensing instruments so that the 
measurements, such as for temperature and oxygen, can register from the 
probe on the instruments. Thereafter, when the time delay relay TD times 
out, the green light GA is turned off and the red light RA is turned on. 
In similar manner, each of the other probes 12, 14 is released, and each 
corresponding green light GB, etc. is turned off while the respective red 
light RB, etc. is turned on. Then, during reloading, the clear button CB 
is pushed so that the red lights RA, RB, etc. go out. The green lights GA, 
GB, etc. will then go on again when the new probes 12, 14 are plugged into 
the outlets 108. 
As those skilled in the art will appreciate, the cords and probes can be 
attached together so that the drop of each probe 12, 14 pulls out the 
dangling cord 106 of the previously dropped probe, so that cord is 
consumed along with the current probe. 
When the selected probe has been released by energizing the power cylinder 
to withdraw the pin 56, the probe will drop down the chute 16 through the 
pipe 18 into the molten metal bath. The probe and the wire 10 will be 
consumed after approximately 30 seconds. The canisters can be rewired with 
new wire assemblies and probes. 
FIG. 12 shows the probe of FIGS. 9, 10 and 11 with a sampler pod as 
disclosed in U.S. Pat. No. 4,881,824. The probe can be provided with an 
immersion sampler pod 130 which contains an outer protective coating of 
refractory fiber material as described above or other material as 
described in my U.S. Pat. No. 4,659,679 and can be provided with two 
spaced clam shell mold halves 132 with a fill tube 134 as shown in my U.S. 
Pat. No. 4,326,426. The entire disclosures of said patents are 
incorporated herein by reference. A small diameter paperboard vent tube 
140 extends onto the sample body to communicate with the interior 137 of 
the mold to provide a vent for the sample cavity 137 to promote filling of 
the sampler when the probe is immersed. A fusible cap 138 on the fill tube 
134 is typically employed to prevent entry of molten metal while the probe 
is lowered through the slag. The tube 140 extends up above the surface of 
the melt to ensure release of the air i the sample cavity as molten metal 
fills the cavity 137. The tube 140 can be connected to pipe 53. 
The sample pod 130 can be releasably clamped to the weight 112 with a 
fusible clamp 152, such as a standard hose clamp. A find braided stainless 
steel wire 154 is located inside of the sampler between the two mold 
halves. A knot 156 anchors the wire 154 to the mold halves which are 
clamped together with a slight gap therebetween. The wire 154 extends 
through the interior 158 of the tube 140 to provide recovery of the sample 
mold 130. The molten steel fuses to wire and knot to provide a secure 
connection to the sampler. 
The tube 140 can be made of a small diameter paperboard tube with an 
internal passage 158. A tube having a diameter three sixteenths of an inch 
can be formed or bent to conform somewhat to the shape of the handle or 
pipe 53. Paper tape can be used to releasably secure the tube to the pipe 
53. The tube 140 also protects the wire 154. The tube 140 can be used with 
or without the wire to vent any sampler to a position above the molten 
metal. The vent tube 140 can be used with other immersion samplers such as 
that shown in U.S. Pat. No. 4,069,715, the entire disclosure of which is 
incorporated herein by reference. The vent tube 140 would be used instead 
of the vents 48 shown in FIG. 4 of that patent. 
FIG. 13 is a view of the probe shown in FIG. 9 floating in molten steel 20 
which has a layer of slag 162. It has been found that in use the steel 
pipe 53 between the paperboard sleeve or float tube 51 and the weight 112 
acquires a steel skull 165. The skull 165 is formed on the pipe 53 when 
the probe is dropped into the steel by free fall. The weight of the probe 
causes the probe to momentarily penetrate the slag-steel interface 168 to 
a depth in the steel below level 170 which exposes the steel pipe 53 to 
the steel melt. Some steel forms an adhering layer or skull 165 shown in 
solid lines on the pipe 53 which remains adhered to the pipe 53 after the 
probe floats up the equilibrium position in FIG. 13 with the skull 165 in 
the latter position being shown in broken lines. The skull 165 may vary in 
thickness depending on conditions of the melt. One quarter inch wall 
thickness is typical for the skull 165. It is believed that the added 
weight from the skull 165 when the skull 165 is located in or above the 
less dense slag layer 162 assures proper positioning of the sensor and 
sampler in the steel below interface 168. Adequate penetration of the 
weight and sensor or sampler 130 into the steel with the probe remaining 
in vertical alignment prevents burn-through of the wires as described in 
U.S. Pat. No. 4,881,824. The skull 165 weight overcomes the buoyancy 
provided by some of the submersed cavities in the probe. Thus the length 
of exposed pipe between the float and weight is important both as a weight 
and as a carrier for the steel skull. A length L of exposed pipe of 24 
inches or more has been found appropriate to provide a good heavy skull 
165. The pipe described is thick walled such as one quarter inch wall 
thickness to provide added weight. The bomb 112 employed with this pipe 
was made from cast iron and had a length of 5 1/8 inches maximum diameter 
of 31/2 inches and a weight of 7 lbs. The central opening 181 was 1.685 
inches wide or in diameter at its maximum width and 1 5/8 inches deep. 
Cavity 189 was 11/8 inches in diameter. The surface 193 was 1.7 inches in 
diameter. Face 195 was 2 inches in diameter. Cavity 197 was 7/8inches deep 
and 1.7 inches in diameter.