Fluid pressure control and relief apparatus

Fluid pressure above a predetermined limit in a fluid pressure system is reduced by operating a relief valve, having its inlet port connected with the system, in a throttling action. A normally seated valve member is maintained in relief valve closed position by pneumatic pressure on a piston in a chamber of the relief valve. A fluid pressure sensor communicating with the inlet port generates a signal in response to fluid pressure above a predetermined limit received by a sensor signal processor energized by a source of electrical energy which releases pneumatic pressure in the chamber for a predetermined time interval allowing system fluid pressure to unseat the valve member and exhaust fluid pressure through the relief valve outlet port.

This invention relates to pressure relief valves and more particularly to 
an apparatus for monitoring and releasing fluid pressure before it reaches 
a critical value. 
BACKGROUND OF THE INVENTION 
1. Field of the invention 
In process and power plant operation fluid pressures must be constantly 
controlled for the safety of personnel and equipment. This is usually 
accomplished by utilizing known safety relief valves such as spring, 
frangible disc or shear pin. 
However, such valves are not always satisfactory for the reason over time 
the spring deteriorates in its accuracy of fluid pressure release. The 
frangible disc by being constantly flexed by the build up and decrease of 
fluid pressure crystallizes and may fail below the set pressure. 
Similarly, a sheared pin may be replaced by a workman, tired of constantly 
replacing a sheared pin, inserting a pin of higher shear value such as an 
ALLEN wrench, thus, defeating the purpose of the relief valve. 
This invention is an improvement over the above fluid control equipment by 
providing an independent fluid pressure sensing apparatus that monitors 
fluid pressure buildup and opens a fluid release valve to decrease fluid 
pressure before it reaches a critical value. 
2. Description of The Prior Art 
The most pertinent patent is believed to be U.S. Pat. No. 3,890,992 issued 
Jun. 24, 1975 to Wolz et al for METHOD AND APATUS FOR SAFEGUARDING 
PIPE-LINES AGAINST AN INADMISSIBLY HIGH INTERNAL COMPRESSIVE LOAD BY A 
CONTROL VALVE WITH A PNEUMATIC DRIVE. This patent discloses a relief valve 
on a pipeline pneumatically operated for relieving fluid pressure through 
a relief valve in which the fluid pressure in a pipeline is monitored and 
air supplied at a pressure that is a function of the monitored pressure to 
hold the relief valve in a closed position. If the rate of fluid pressure 
causes the rate of increase in air pressure to exceed a predetermined 
value, other valves are actuated to reduce the air pressure holding the 
relief valve closed, thus, allowing opening of the relief valve and the 
release of fluid pressure from the pipeline. 
U.S. Pat. No. 3,548,866 issued Dec. 22, 1970 to Kaiser et al for 
SERVO-CONTROLLED HIGH PRESSURE RELIEF VALVE and U.S. Pat. No. 5,152,316 
issued Oct. 6, 1992 to Dorr for SERVO DRIVE FOR SAFETY AND REGULATING 
VALVES are believed good examples of the further state-of-the-art. 
The Kaiser et al patent uses a servo controlled valve for pressure feedback 
to operate the servo-valve as a pressure relief valve. This is 
accomplished by a transducer sensing fluid pressure and amplifiers and 
compensation circuits compared with a reference voltage to operate of the 
servo-valve and through a manifold pass fluid to a hydraulic cylinder in 
turn operating a conical valve as a pressure relief valve. 
The Dorr patent discloses a servo-drive responsive to fluid pressure being 
monitored to operate a fast acting planetary gear arrangement that moves 
the spindle drive of a safety relief valve in an opening or closing 
direction for monitoring fluid pressure in a system. 
This invention is believed distinctive over the above named patents by 
providing electro-pneumatic components that applies a source of gas 
pressure against the valve of a fluid pressure relief valve to normally 
maintain the relief valve closed. Self resetting fluid pressure sensing 
components monitor fluid pressure applied to a fluid pressure release 
valve for activating other components for bleeding off fluid pressure 
before reaching a predetermined critical value. 
SUMMARY OF THE INVENTION 
In a preferred embodiment a pressure relief valve is axially connected by 
its inlet port with a source of fluid pressure to be monitored. The relief 
valve includes a seated valve normally closing the inlet port by a source 
of pneumatic pressure acting on a piston or diaphragm connected with and 
normally maintaining the seated valve closed. 
A first four-way solenoid valve is interposed between the pneumatic source 
of pressure and the piston or diaphragm. 
A second normally open solenoid valve communicates with the relief valve 
inlet port. A pressure switch responsive to fluid pressure in the relief 
valve inlet port is connected with a relay timer in turn connected with 
the pilot of the four-way solenoid valve and the second normally open 
solenoid valve. A source of electrical energy maintains the timer and 
pressure switch energized. 
In another embodiment the pressure switch is replaced by a pressure 
transducer and a microprocessor replaces the relay timer. 
The principal object of this invention is to provide a fluid pressure 
monitoring and release system, which includes a normally closed pressure 
release valve having a normally closed inlet port and normally open outlet 
port in which excess pressure in the inlet port is sensed by fluid 
pressure self resetting components that bleeds fluid pressure from a 
chamber biasing the relief valve closed to allow the relief valve to open 
and reduce fluid pressure in the system being monitored. 
A further object is to provide a fluid pressure relieving system of this 
class for monitoring very high fluid pressures in which monitored 
excessively high fluid pressure is lowered to an acceptable value by 
resetting pressure sensitive elements continually repeating the fluid 
pressure reducing function of the relief valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Like characters of reference designate like parts in those figures of the 
drawings in which they occur. 
Referring first to FIG. 1 the reference numeral 10 indicates the apparatus 
as a whole comprising a relief valve 12 monitoring fluid pressure in a 
vessel or line 14. The valve 12 is normally maintained in valve closed 
position by piston means 16 maintaining the relief valve closed by 
pneumatic means 18 connected with the piston means 16 through a four-way 
solenoid pilot operated valve means 20, having fluid throttling or bleeder 
valves 21 and 23, and responsive to fluid pressure sensing means 22 in 
combination with a source of electrical energy 24. 
The relief valve means 12 comprises a valve body 25 having an inlet port 26 
connected with the line 14 and an outlet port 28 forming a passageway 
through the valve body 25 normally closed by a valve 30 seated on a valve 
seat. 
The piston means 16 comprises a cylinder 32 axially connected with the 
valve body 25 opposite the pipe 14 to form a chamber 34 containing a 
piston 36 having a piston rod 38 connected with the valve 30 opposite its 
seat for normally maintaining the valve 30 seated as presently explained. 
The pneumatic means 18 includes a source of high pressure air 40 connected 
with a shuttle valve 42 through a control valve 44 and high pressure 
regulator 46 connected in series in one leg of a tubing loop 48, the 
shuttle valve 42 being connected in turn with the four-way solenoid valve 
means 20 through a needle valve 50. 
The other leg of the tubing loop 48 includes a compressed air reservoir 52, 
initially charged by the source 40 and connected with the shuttle valve 
through a series connected stop valve 54 and low pressure regulator 56. 
The pressure sensing means 22 includes a tubular fitting means 58 connected 
with the inlet port 26 of the valve means 12 by a restrictor valve 60. A 
normally closed pressure releasing solenoid valve 64 is connected with the 
tubing fitting means 58 downstream from the restrictor valve 60. A 
pressure sensitive switch 62 is interposed in the tubing fitting means 58 
between the valve 60 and the solenoid valve 64. 
The pressure switch 62 is connected with the source of electrical energy 24 
through a sensor signal processing and timing means, such as a relay timer 
66, in turn connected with the pilot of the four-way valve means 20 and 
the solenoid valve 64. 
The source of electrical energy 24 includes a battery 68 maintained charged 
by a solar panel 70 connected with the battery through a voltage regulator 
72. 
An auxiliary source of compressed air includes a compressor 74 connected 
with the battery 68 and reserve tank 52 through a check valve 76. The 
compressor 74 is energized by a pneumatic switch 78 in the event the air 
pressure in the pneumatic means 18, including the reserve tank 52, falls 
below a predetermined limit. 
Operation 
In the operation of the apparatus illustrated by FIG. 1, the pressure 
switch 62 is set at a predetermined fluid pressure value in accordance 
with the requirements of the system being monitored. When the fluid 
pressure in the inlet port 26 reaches this predetermined value the 
pressure switch 62 energizes the adjustable relay timer 66 which opens the 
normally closed solenoid valve 64 to relieve the fluid pressure in the 
tubing fitting 58, which triggered the pressure switch 62, and 
simultaneously shifts the four-way solenoid valve means 20 to exhaust air 
pressure from the cylinder chamber 34 through the adjustable flow 
restrictor valve 21. Decreased air pressure in the cylinder chamber 34 
allows the fluid pressure in the inlet port 26 to move the piston 36 and 
valve 30 off the valve seat to discharge excess fluid pressure through the 
valve outlet port 28. By adjusting the bleeder valves 21 and 23 on the 
exhaust side of the solenoid valve means 20, the opening cycle is 
throttled while pressure is being relieved. Similarly the needle valve 50 
in the air line leading to the piston chamber 34 provides a means to 
adjust and throttle the closing cycle. Such flow adjustment features play 
a significant role in the prevention of "chattering" or the creation of 
pressure surges caused by the relief valve mechanism being abruptly opened 
or slammed shut. 
When the relay of the timer 66 resets, the four-way valve means 20 is 
shifted to again apply air pressure to the chamber 34 and seat the valve 
30 while simultaneously closing the normally closed solenoid valve 64 
which completes one cycle of operation. 
However, if the fluid pressure in the inlet port 26 still exceeds the 
predetermined value, the pressure switch 62 again energizes the timer 66 
and the cycle is repeated which continues until the fluid pressure in the 
inlet port 26 has decreased to a value below the set value. 
Referring also to FIG. 2, in which like components have reference numerals 
identical with FIG. 1 and modified components have prime numerals. 
In the event the apparatus 10' is monitoring fluid pressure of extremely 
high values, the pressure sensing means 22' is modified by interposing a 
normally open solenoid valve 80 in the fitting 58' between the needle 
valve 60 and the pressure switch 62. 
Thus, in operation of the apparatus of FIG. 2 fluid pressure in the inlet 
port 26 above a predetermined value triggers the pressure switch 62 
energizing the pilot of the four-way valve means 20 to exhaust air 
pressure from the chamber 34 as described hereinabove. 
When the pressure switch 62 is triggered the timer 66 shifts the solenoid 
valve means 20, as described hereinabove, and the normally open solenoid 
80 is closed and the normally closed solenoid valve 64 is opened, by the 
relay timer resetting, creating a substantial pressure drop across the 
pressure switch 62 causing it to reset. If fluid pressure in the tubing 
fitting 58' is still above the predetermined limit, the cycle repeats and 
continues to repeat until the fluid pressure in the inlet port 26 reaches 
an acceptable value. 
FIG. 2 also illustrates the use of pneumatic valves as an alternative in 
place of the valves 80 and 64, in which conduits 82 respectively connected 
with the four-way valve means 20 is exhausted through the valve means 20 
fluid flow throttling valve 23 for limiting the rate of fluid discharge. 
Referring also to FIG. 3 in which like components bear identical reference 
numerals with respect to the other Figures and modified components have 
double prime numerals. 
In this embodiment, the pressure switch 62 is replaced by a transducer 84 
connected with the modified tubing fitting means 58". The timer 66 is 
replaced by a microprocessor 86, similarly connected with the electrical 
energy source 22. 
In operation of the apparatus 10" the transducer is similarly responsive to 
predetermined pressure values in the inlet port 26. The signal produced by 
the transducer is processed by the microprocessor 86 which shifts the 
valve means 20 to discharge fluid pressure from the chamber 34 through the 
throttling valve 21 allowing movement of the piston 36 in the ball valve 
opening movement for reducing pressure in the inlet port 26 to a 
predetermined value. Thereafter the microprocessor shifts the valve means 
20 to pressurize the chamber 34 and reseat the valve 30 thus, completing 
one cycle of the transducer version of the apparatus. 
In this embodiment, the microprocessor 86 is connected with the pneumatic 
switch 78 to energize the auxiliary compressor 74 for recharging the 
reserve air pressure tank 52. 
Obviously the invention is susceptible to changes or alterations without 
defeating its practicability. Therefore, I do not wish to be confined to 
the preferred embodiment shown in the drawings and described herein.