Apparatus for controlling lubricating oil fires due to oil line failure

Fires caused by the leakage of lubricating oil spraying under pressure from lubricating oil conduits feeding bearings are controlled by stopping the flow of the lubricating oil in response to greater than normal flow of the oil through the conduit and simultaneously shutting down the machine having the bearing to which the oil is fed. A valve mounted in each conduit includes a valve element movable in response to the greater than normal flow through the conduit from a first position, to which it is biased and in which it is spaced from a valve seat, to a second position in which it engages the valve seat. A magnet mounted on the valve element actuates a magnetically operated switch connected in a circuit for shutting down the machine when the valve element moves at least part way from the first position to the second position. An alarm is activated as the machine is being shut down.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for controlling fires and, more 
specifically, to a device for preventing lubricating oil fires resulting 
from the fracture or separation of an oil line at the bearing of a machine 
having a pressurized lubricating system. 
The hazard of lubricating and hydraulic oil fires in electric generating 
stations has been of concern for many years. In 1964 the National Fire 
Protection Association published a pamphlet on fires in electric 
generating plants and highlighted three fires involving the spray of oil 
from broken oil lines. The total loss, in 1988 dollars, was $15,000,000. 
The inventor is aware of twenty-four fires of this type between 1951 and 
1988, with a total estimated loss of $125,000,000. Many of the fires 
burned until the lubricating oil was able to be shut off or its supply was 
exhausted. By the time the cause of the fire was determined and the 
spraying of oil from the failed oil line was able to be stopped, damage of 
many millions of dollars had already occurred. 
In pressurized lubrication systems, such as those used for steam and gas 
turbines, internal combustion engines, and rotating and reciprocating 
compressors, lubricating oil is delivered to the bearings at pressures of 
up to 35 psig. The flow to each bearing is controlled by a metering 
orifice in the bearing housing. This orifice reduces the pressure of the 
lubricating oil to atmospheric pressure in the bearing area. 
Lubricating oil fires often occur around the systems described above as a 
result of the fracture of an oil pipe to a bearing or the separation of 
such an oil pipe from its connections. The oil under pressure sprays out 
at the point of failure in a fine mist, which is readily ignited by 
adjacent hot surfaces or by other mechanisms. The resulting fire is 
torch-like, with a very high rate of heat release, such that the fire may 
ignite or overheat building structure and contents up to sixty feet away 
from the point of spray origin. 
Water sprinkler discharge, or even water spray discharge directly on the 
oil pipe at the point of oil release, is known to be ineffective in 
extinguishing or controlling such fires. Water may limit the damage 
caused, by cooling the target material or structure, if the water can be 
directed properly. The only effective extinguishments have been 
total-flooding agents, such as the Halons, and carbon dioxide. However, 
the use of these agents requires that the machinery protected from the 
fire be enclosed in a housing which can be sealed off to retain the 
necessary concentration of the extinguishing agent for as long as there is 
a danger of reignition. This is not usually practical, other than for some 
gas turbine installations. 
Oil-spray fires of the type described above are very similar to leaking gas 
fires in that the principal approach to the extinguishment of both such 
fires is to shut off the flow of the flammable fluid. However, in most 
installations affected by oil-spray fires, auxiliary oil pumps continue to 
pump oil to the bearings of the machinery after the machine is tripped off 
line. The problem here is that the oil lines in which the failures occur 
supply the bearings of huge and very expensive steam turbines rotating at 
very high speeds. The lubricating oil cannot simply be cut off to stop the 
fire, since very extensive damage is likely to occur as a result of the 
failure of the bearings and the damage that the failure of the bearings 
would have on the spinning turbines. Therefore, the flow of oil is 
maintained to protect the bearings while the machine is coming to a stop 
and, in the case of large steam and gas turbines, after it has been put on 
turning gear for slow rotation during cooldown. 
SUMMARY OF THE INVENTION 
By the present invention, the emission of an oil spray from a pressurized 
oil line feeding a bearing is shut off instantaneously upon the failure of 
the line in order to control and perhaps even prevent any fire from the 
emission of the oil spray from the line. The apparatus according to the 
present invention also minimizes damage to the bearings and prevents 
consequent damage to the machine due to oil starvation by instantaneously 
shutting down the machine. 
A significant problem in attacking fires of this type--the delay in 
recognition by the machine operators that the fire is being caused by the 
spray of oil from a ruptured or separated oil line--is avoided by the 
instantaneous actuation of the apparatus according to the present 
invention to shut off the oil flow in the affected line in response to the 
reduction in line pressure downstream of the apparatus. A device for 
stopping the flow of lubricating oil and simultaneously shutting down the 
machine is positioned in each line, or conduit, feeding lubricating oil to 
a bearing of the machine. The device comprises a valve defining a coupling 
having a first coupling member secured to a first portion of a pressurized 
lubricating oil line and a second coupling member connected between the 
first coupling member and a second portion of the pressurized lubricating 
oil line. A piston of non-magnetic material is slidably mounted in a 
sleeve in the first coupling member and normally biased to a position 
allowing the lubricating oil to flow from the first portion, through the 
device, and into the second portion. The piston includes a valve surface, 
and the second coupling member has a valve seat spaced from the valve 
surface to permit the flow of lubricating oil therebetween during normal 
operating conditions. The piston is responsive to a decrease in the 
downstream pressure due to a break or separation in the second portion of 
the lubricating oil line and an associated greater than normal flow 
through the line to move into a seated position in which the valve surface 
sealingly engages the valve seat and thereby prevents further flow of 
lubricating oil through the device. Thus, a break or separation in the 
lubricating oil line results in the cessation of the flow of lubricating 
oil through the device and, therefore, to the point of break or 
separation. 
A magnetically operated switch, such as a reed switch, is mounted on the 
second coupling member adjacent the path of movement of the piston. A 
permanent magnet is mounted on the piston in a place adjacent the 
magnetically operated switch, the magnet moving with the piston from a 
normal operating position in which the magnet does not influence the 
magnetically-operated switch to a position causing the actuation of the 
magnetically-operated switch when the piston reaches a position at least 
part way toward the seated position. The switch is connected in a circuit 
for controlling the shutting down of the machine, whereby actuation of the 
switch causes activation of the control circuit to shut down the machine. 
Actuation of the switch also activates an alarm in a control room so that 
the machine operators will immediately know what has happened.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As can be seen from FIG. 1, a steam turbine and generator arrangement, 
which is designated generally by the reference numeral 10, includes a 
generator 12 and a steam turbine including a high pressure turbine section 
14, an intermediate pressure turbine section 16 and low pressure turbine 
sections 18 and 20. All of the steam turbine sections 14, 16, 18 and 20 
are mounted on a common shaft 22, which is connected by a coupling 24 to a 
shaft 26 on which the generator 12 is mounted. A plurality of bearings 
B1-B9 support the turbine shaft 22 for rotation, bearings B1 and B2 being 
positioned between the high pressure turbine section 14 and the 
intermediate pressure turbine section 16, bearings B3 and B4 being 
positioned between the intermediate pressure turbine section 16 and the 
first low pressure turbine section 18, bearings B5 and B6 being positioned 
between the two low pressure turbine sections 18 and 20, and a bearing B7 
being positioned between the second low pressure turbine section 20 and 
the coupling 24. Bearings B8 and B9 are provided to support the generator 
12 for rotation. In addition, a thrust bearing B10 is positioned around 
the turbine shaft 22 between the bearings B1 and B2. Each of the bearings 
B1-B10 are lubricated by lubricating oil fed under pressure through 
individual pressure conduits or lines PL1-PL10 associated with the 
bearings B1-B10, respectively. The individual pressure lines extend from a 
pressure header 32 which receives lubricating oil under pressure from a 
pump (not shown). Individual lubricating oil drain lines DL1-DLl0 are 
associated with the bearings B1-B10, respectively. The individual drain 
lines are connected to a drain header 36 from which a drain 38 leads to 
the inlet of the lubricating oil pump. In normal operation, lubricating 
oil fed under pressure from the pump flows through the pressure header 32, 
through the individual pressure lines PL1-PL10, and through the bearings 
B1-B10 for lubrication purposes. The lubricating oil then flows out of the 
bearings through the individual drain lines DL1-DL10, through the drain 
header 36 and the drain 38 to be recirculated by the pump. 
A metering orifice (not shown) is positioned at the inlet to each bearing 
B1-B10 to reduce the pressure of the lubricating oil to atmospheric 
pressure at the bearing area, as is known in the art. The orifices are 
also the cause of back pressure between the bearings and the lubricating 
oil fire control devices D1-D10 positioned in the lubricating oil pressure 
lines PL1-PL10, respectively. A fracture or separation of a lubricating 
oil line usually results in a spray of the oil, which is flammable, and 
since there are so many hot surfaces near by, the oil spray is likely to 
ignite, starting a fire. A fracture or separation in any of the pressure 
lines PL1-PL10 downstream of its associated lubricating oil fire control 
device D1-D10 results in a greater than normal flow of oil through the 
line, a decrease in the back pressure caused by the associated orifice, 
and a consequent increase in pressure differential across the control 
device. As will be described more specifically hereinafter, the increased 
pressure differential causes the control device to shut off the flow of 
lubricating oil in its pressure line and, thereby, stop the supply of 
combustible material for the fire. Since lubricating oil control devices 
are associated with each of the pressure lines feeding the individual 
bearings, the lubricating oil flow in only the failed pressure line, and, 
therefore, the lubricating oil feed to only one bearing, will be stopped. 
The lubrication system will continue to provide oil to the remaining 
bearings. Thus, the likelihood of significant damage to the turbine or 
generator as a result of bearing failure is small. Furthermore, 
simultaneous with the stopping of the lubricating oil flow, the affected 
control device shuts down the turbine so that even a bearing whose 
lubricating oil supply has been cut off may avoid damage. 
Each of the control devices D1-D10 comprises a valve of a type which can be 
called a velocity fuse, the valve defining a coupling, as can be seen from 
FIG. 2, which is a cross section of one of the control devices, for 
example, control device D1. It is understood that the other control 
devices D2-D10 can have the same structure. The control device D1 includes 
a first coupling member 50 having threads 52 for connecting the first 
coupling member to mating threads on a portion of the lubricating oil 
pressure line PL1 extending from the pressure header 32. A sleeve 54 is 
positioned in the first coupling member 50, the sleeve 54 having a 
circumferential array of circular ports 56 and a flange 58 extending 
radially from one end of the sleeve. The flange 58 engages a land 60 
projecting radially inward from the first coupling member 50. The sleeve 
54 supports a piston 62 of non-magnetic material for sliding between a 
position permitting full flow through the device and a position stopping 
flow. The piston 62 is a hollow cylinder, having a closed end 66, a side 
wall 67, an open end 68 positioned on a side of the land 60 opposite from 
the closed end 66, and a circumferential array of elongated slots 69 
through the side wall 67 in alignment with the ports 56 of the sleeve 54. 
A flange 70 extends radially outward from the open end 68 of the piston 62 
and a spring 72 is positioned between the land 60 and the flange 70 of the 
piston 62. The spring 72 biases the piston 62 into the position permitting 
full flow through the control device D1, holding the flange 70 in 
engagement with an externally threaded preloading nut 74, which is held in 
a desired position in the bore of the first coupling member 50 by threaded 
engagement with the threads 52. The preloading nut 74 is adjustable by 
screwing farther into or out of the first coupling member 50 to determine 
the full flow position of the piston 62. The length of the elongated slots 
69 is sufficient to keep the slots lined up axially with the ports 56 for 
any anticipated installed length of the spring 72. 
An end of the first coupling member 50 opposite to the end having the 
threads 52 includes external threads 76 for mating with internal threads 
78 of a second coupling member 80. The second coupling member 80 includes 
a shoulder 82 which engages one end of a precisely machined annular spacer 
84. The other end of the spacer 84 engages the radial flange 58 of the 
sleeve 54 and holds the flange fixed against the land 60. The second 
coupling member 80 also includes a conical machined surface defining a 
valve seat 86. The valve seat 86 is aligned with, but spaced from, a valve 
surface 88 of corresponding conical shape defined on the closed end of the 
piston 62. The second coupling member 80 includes a reduced diameter bore 
90 defining a flow passage downstream of the valve seat 86, and the closed 
end 66 of the piston 62 includes an extension 92 projecting into the 
reduced diameter bore 90. A permanent magnet 94 is positioned in a recess 
defined in the extension 92. The portion of the second coupling member 80 
defining the reduced diameter bore 90 has a wall 96 at least a portion of 
which is relatively thin and a magnetically operated switch, such as a 
reed switch 98, is positioned on the external side of the wall 96 in a 
cavity 99 in the second coupling member 80. An end of the second coupling 
member 80 opposite the threads 78 includes threads 100 for connecting the 
device D1 to a threaded portion of the pressure line PL1 leading to the 
bearing B1. The parts of the device D1 are made of a material, such as 
brass, which is non-magnetic and which is non-corrodible by petroleum-base 
or synthetic lubricants. 
As can be appreciated from the block diagram of FIG. 3, the reed switch 98 
is connected in a control circuit including, for example, a relay (not 
shown), which is a part of a turbine shutdown system 101 for shutting down 
the turbine. Thus, when the reed switch 98 is actuated, by the proximity 
of the permanent magnet 94, the turbine shuts down. A visual and/or 
audible alarm 102 in a control room can also be connected in a circuit 
with each reed switch to immediately tell operators what has happened. 
In normal operation, lubricating oil under pressure flows from the portion 
of the pressure line PL1 upstream of the lubricating oil control device D1 
into the first coupling member 50. As can be seen from FIG. 2, the flow 
continues through the interior of the piston 62, through the slots 69 and 
through the aligned ports 56 in the sleeve 54. The flow continues through 
a space between the sleeve 54 and the annular spacer 84, through the space 
between the valve surface 88 and the valve seat 86, around the extension 
92 of the piston 62 and into the portion of the pressure line PL1 leading 
to the bearing B1. Due to the back pressure exerted on the fluid by the 
orifice at the inlet to the bearing, the flow is at relatively low 
velocity and the pressure of the lubricating oil flowing into the piston 
62 is insufficient to overcome the bias of the spring 72, so that the 
flange 70 of the piston 62 is held against the preloading nut 74, and the 
valve surface 88 is kept spaced from the valve seat 86. In this position 
of the piston 62, the permanent magnet 94 is not properly positioned 
relative to the reed switch 98 to actuate the switch, and so the turbine 
runs unaffected. 
In the case of a fracture or separation in the oil line PL1 downstream of 
the device D1, or even in the case of a serious leak, the lubricating oil 
will flow out of the pressure line PL1 more quickly than is normal, up to 
three or four times normal flow, and, thereby, will reduce the pressure 
downstream of the piston 62. The reduced pressure results in an increase 
in pressure differential between the upstream and downstream sides of the 
piston 62, so that the pressure of the entering lubricating oil is now 
sufficient to overcome the bias of the spring 72 and instantaneously move 
the valve surface 88 into sealing engagement with the valve seat 86, 
cutting off the flow of lubricating oil through the control device D1. 
Thus, the source of fuel feeding any fire around the downstream break in 
the pressure line PL1 is cut off, and the fire can be controlled. 
Furthermore, the movement of the piston 62 places the permanent magnet 94 
in a position properly aligned with the reed switch 98 to actuate the reed 
switch and thereby activate the turbine shutdown system 101 (FIG. 3), 
shutting down the turbine. Since the turbine is shut down, the oil 
remaining in the bearing B1 prior to the cutoff of lubricating oil by the 
actuation of the device D1 may be sufficient to prevent damage to the 
bearing B1. As can be seen from FIG. 3, the reed switches 98 of all of the 
pressure devices D1-D10 can be connected to an OR gate 104, so that 
actuation of any one of the reed switches, in response to a break in any 
one of the pressure lines PL1-PL10, results in activation of the alarm 99 
and the turbine shutdown system 101. 
The relative positioning of the permanent magnet 94 and the reed switch 98 
is preferably arranged so that the magnet 94 actuates the reed switch 98 
at a suitable point between the fully open and fully closed positions of 
the valve surface 88 with respect to the valve seat 86. As a result, the 
turbine shutdown system 101 and the alarm 102 are activated when the 
piston 62 is only part way between its fully open position and its fully 
closed position. This is done in order to shut down the turbine in case a 
break in a line does not occur instantaneously but develops from a crack 
over a short period of time. This limits damage to the bearing by shutting 
down the turbine before lubrication to the bearing served by the leaking 
oil line is shut off entirely, thereby maintaining lubrication to the 
bearing until the turbine is rotating at as low a speed as possible. 
When the turbine is tripped, an auxiliary lubricating oil pump takes over, 
as a part of the turbine shutdown system 101 to supply lubricating oil to 
the bearings. The lubricating oil is supplied by the auxiliary pump under 
a pressure which is somewhat less than the pressure developed by the main 
turbine pump. The spring 72 is designed so that, when the turbine is 
tripped off line by a failure in the oil pressure line PL1, the pressure 
under which the lubricating oil is fed by the auxiliary pump is sufficient 
to keep the valve surface 88 on the piston 62 in sealing engagement with 
the valve seat 86, overcoming the force exerted by the spring 72 on the 
piston 62 in the opposite direction. In the event of a surge of 
overpressure, up to the peak discharge pressure of the lubricating oil 
pump, during normal operation, the piston 62 will not move toward the 
closed position, even partially, by virtue of the pre-established preload 
in the spring 72. The spring 72 is never moved in the normal operation of 
the control device D1 and, therefore, the spring cannot fail in fatigue, 
which is the usual mode of failure of mechanisms in normal operation. If 
the spring 72 does become weakened, through corrosion, erosion or some 
other mechanism, the weakened spring 72 will allow the piston 62 to move 
to a position in which the permanent magnet 94 actuates the reed switch 98 
to trip the turbine shutdown system 101 and annunciate the alarm 102 in 
the control room before the supply of lubricating oil is completely shut 
off to the bearing Bl associated with the oil pressure line PL1 containing 
the control device D1. Furthermore, if the ports 56 in the sleeve 54 begin 
to plug gradually, from silt or dirt in the lubricating oil, the piston 62 
will move to actuate the reed switch 98, trip the turbine shutdown system 
101, and annunciate an alarm 102 before the lubricating oil to the bearing 
B1 is shut off completely, again by virtue of the positioning of the reed 
switch 98 relative to the permanent magnet 94. The actuation of the reed 
switch 98 of any of the lubricating oil control devices D1-D10 
instantaneously trips the turbine off line through the activation of the 
turbine shutdown system 101 and also activates the alarm 102. 
Although the lubricating oil fire control devices according to the present 
invention have been described in connection with a steam turbine and 
generator, it is understood that they can be used in connection with other 
machinery having force fed lubrication and environments which present the 
potential for a lubricating oil fire in case of a leak. In addition, the 
fire control devices according to the present invention can be used in 
connection with the pressure feeding of other flammable fluids, such as 
hydraulic fluid, to machinery. Although one embodiment of the control 
device according to the present invention has been particularly described 
herein, it is intended that various modifications can be made without 
departing from the spirit and scope of the present invention, which is 
defined in the appended claims.