Electropneumatic pressure relief indicator

A pressure relief indicator including a housing connected in fluid communication with a fluid system to be relieved, a pair of rupturable diaphragms extending in closing relation across the housing and combining to define a closed chamber, the diaphragm adjacent to the system rupturing at a predetermined desired relief pressure and the other diaphragm rupturing at a lesser pressure, a pressure supply maintaining a control pressure in the chamber of a value between atmospheric pressure and the lesser diaphragm rupturing pressure, and an annunciator responsive to change in pressure differential between the chamber and atmosphere as upon rupture of the diaphragms.

BACKGROUND OF THE INVENTION 
As is well known to those versed in the art, pressurized fluid systems are 
generally provided with suitable relief means, serving among other 
purposes that of localizing the relief of excess pressure for safety, 
convenience and obviating or minimizing economic loss. Toward this end, 
burst discs have been employed in conduits, vessels and other parts of 
pressure systems, which discs are calibrated for breakage or rupture under 
a predetermined fluid pressure. While the use of burst discs has proved 
satisfactory for pressure relief, there has not been found entirely 
satisfactory means for indicating the existence and location of a ruptured 
disc, consistent with safety as from electrical hazards, speed and 
reliability of indication, and economy in manufacture, installation and 
maintenance. 
SUMMARY OF THE INVENTION 
It is, therefore, an important object of the present invention to provide a 
pressure relief indicator device for use with burst discs, which is 
extremely simple in construction for economy in manufacture and 
installation, while being highly durable and entirely reliable throughout 
a long useful life. 
It is a further object of the present invention to provide a burst disc 
indicator of the type described which is highly accurate for remote signal 
activation at any desired pressure, eliminates all electrical connections 
and wiring proximate to the burst disc location, is capable of indication 
with any panel board or alarm system at any location, can be pneumatically 
and electrically tested in position and without damage, and is adapted for 
installation and maintenance without special training. 
Other objects of the present invention will become apparent upon reading 
the following specification and referring to the accompanying drawings, 
which form a material part of this disclosure. 
The invention accordingly consists in the features of construction, 
combinations of elements, and arrangements of parts, which will be 
exemplified in the construction hereinafter described, and of which the 
scope will be indicated by the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now more particularly to the drawings, and specifically to FIG. 1 
thereof, a pressure relief device or burst disc indicator of the present 
invention is there generally designated 10, and shown in FIG. 2 as applied 
to a fluid pressure system or conduit 11. It is appreciated that the 
pressure relief apparatus of the present invention may be applied at any 
desired location to a fluid pressure system, say to a pressure vessel, 
conduit or other, and the term "conduit" as employed herein and in the 
claims is intended to cover all component parts of a fluid pressure system 
to be protected. 
The specific illustrated conduit, as shown in FIG. 2, may consititute a Tee 
section 15 interposed between pipe sections 16 and 17 and provided with an 
upstanding stem portion 18 including a flange 19. 
Spaced over the flange 19 of stem 18 is a vent section or tube 20, 
generally aligned with the stem 18 and provided with a flange 21 spaced 
over the flange 19. 
Interposed between the flanges 19 and 21 is a generally tubular housing 25 
being secured therein by suitable means, such as a circular array of tie 
members or bolts 26 extending between the flanges 19 and 21 at spaced 
locations about the housing 25. 
The housing 25 is generally tubular and open-ended, having its lower end 30 
proximate to and in alignment with the flange 19 of stem 18, say with a 
sealing gasket 31 interposed in sealing engagement between the lower 
housing end 30 and the flange 19. An upper end gasket 32 may similarly 
interposed between the upper end 33 of tubular housing 25 and vent flange 
21. 
Further, the tubular housing 25 may advantageously be constituted of a 
plurality of generally annular sections 35, 36 and 37 superposed in 
aligned relation with respect to each other and with lower stem 18 and 
upper vent 20. 
Annular section 35 is lowermost, and includes on its underside the annular 
surface 30 engaging sealing gasket 31. The upper side of lower section 35 
is formed with annular recess 40 opening upwardly through the top annular 
surface 41 of the lower section and radially inwardly through the 
generally cylindrical internal surface of the lower section. Thus, the 
annular recess 40 defines an annular internal shoulder 42 facing generally 
upwardly. The upwardly facing annular surface or shoulder 42 of lower 
section 45 serves as a seat for supporting engagement with a lower or 
primary burst disc 43 which extends in closing relation entirely across 
the interior of lower housing section 35. The primary burst disc 43 is a 
rupturable diaphragm, advantageously of graphite, but possibly of other 
material, so sized and structured as to burst or rupture under a 
predetermined fluid pressure. 
The intermediate annular housing section 36, immediately above and adjacent 
to the lower housing section 35 is generally axially aligned therewith and 
provided on its underside with an annular depending ridge or land 44 
spaced from the exterior surface of the housing section 36 for entry into 
and bearing engagement with the peripheral margin of primary diaphragm 43 
on the upper side thereof. 
The upper side or end of intermediate housing section 36 is formed with an 
annular recess 45 opening upwaradly and radially inwardly to define an 
annular upwradly facing internal shoulder 46, similar to the shoulder 42 
of lower housing section. The shoulder 46 is adapted to conformably seat a 
secondary rupturable diaphragm, disc or seal 47 which extends entirely 
across the interior of intermediate housing section 36 and closes the 
housing. 
The upper annular housing section 37 is superposed in aligned relation with 
and over the intermediate housing section 36, and is provided on its 
underside with an annular depending peripheral rib 48 for seating 
engagement on the upper surface of the diaphragm 47 about the 
circumferential margin thereof. 
It will now be appreciated that there is defined in the space between the 
diaphragms 43 and 47, and bounded within the intermediate housing section 
36, a closed chamber 50. 
The primary diaphragm 43 is calibrated for rupture at a fluid pressure 
desired to relieve the system 11; and, the diaphragm 47 is calibrated for 
rupture at a lesser fluid pressure than that of the primary diaphragm, so 
that its rupture is assured upon rupture of the primary diaphragm. In this 
manner the operation is fail-safe. 
A fluid conduit 51 comunicates between a source of control fluid pressure 
or air, as at 52, and the interior of chamber 50, as through port 53. 
Interposed in the conduit 51 may be a fluid pressure regulator 54 adjacent 
to the fluid source 52, a flow indicator 55 downstream from the regulator, 
a valve 56, such as a check valve downstream from the flow indicator, and 
suitable bleed means 57 between the valve 56 and chamber 50. An additional 
port 60 may communicate through the intermediate housing section 36 
between the interior of chamber 50 and the exterior thereof, for 
connection to a fluid conduit 61 which may connect at its other end 
through a port 62 to the interior of upper housing section 37 and 
communication therethrough to vent 20 and the atmosphere or environs. 
Interposed in the fluid line 61 may be a differential pressure sensitive 
device such as a normally open electric switch 63, which closes upon 
change in differential pressure sensed between the interior of chamber 50 
and the vent 20. Suitable electric connection means, such as 64 may be 
associated with the switch 63 and an annunciator, signal or alarm, as at 
65 for actuation of the latter upon closure of the switch 63. Of course, 
either or both of the switches 63 and annunciator 65 may be located remote 
from the housing 25, as desired, so that electrical connection to the 
switch and alarm provides no fire or explosion hazard. Of course, the 
switch 63 effectively closes the pressure conduit or line 61 while sensing 
or being responsive to fluid pressures in the line on opposite sides of 
the switch. 
In operation, the pressure regulator 54 is selected so as to pass fluid 
through conduit 51 into chamber 50 to a predetermined pressure which is of 
a value between the rupture pressure of the secondary diaphragm 47 and the 
environmental, vent or atmospheric pressure communicated through port 62 
to switch 63. In practice a differential pressue of 2" of water has been 
found satisfactory. The one-way check valve 56 prevents the transmission 
of even transient excessive pressure from the chamber 50 to the fluid 
source 52. If desired, the chamber 50 may be bled to reduce or eliminate 
the differential pressure applied to switch 63, in which case the switch 
should activate the annunciator 65, as for test purposes. Of course, it is 
understood that excessive pressure in the system 11 will rupture primary 
diaphragm 43 and immediately rupture secondary diaphragm 47, so that the 
change in differential pressure across switch 63 is sensed and promptly 
announced by indicator 65. 
From the foregoing it is seen that the present invention provides a 
pressure relief indicator device which is relatively simple in 
construction, foolproof in operation, and otherwise fully accomplishes its 
intended objects. 
Although the present invention has been described in some detail by way of 
illustration and example for purposes of clarity of understanding, it is 
understood that certain changes and modifications may be made within the 
spirit of the invention.