Replaceable flow-control assembly for use in a fluid flow line

A single-piece flow-control assembly is configured to be disposed within a pit assembly in a manner which allows the flow-control assembly to be easily and quickly removed and replaced. The flow-control assembly includes one or more rigidly connected regulators disposed between two coupling mechanisms and includes a bracket that mounts the flow-control assembly at a fixed location within the pit assembly. The coupling mechanisms provide a sealed engagement between the ends of the flow-control assembly and a fluid inlet pipe and a fluid outlet pipe when the flow-control assembly is properly installed within the pit assembly. A fluid passageway with a 180 degree bend therein may be provided as part of the flow-control assembly so that the coupling mechanisms simultaneously couple to or decouple from the fluid inlet and outlet pipes by movement of the flow-control assembly in one direction.

TECHNICAL FIELD 
The present invention relates generally to fluid flow lines and, more 
particularly, to a flow-control assembly having fluid flow control 
components that can be easily removed from and inserted into a fluid flow 
line. 
BACKGROUND OF THE ART 
Fluid flow systems, such as natural gas distribution systems, include a 
network of fluid flow lines that distribute fluid from a fluid source, 
such as a gas provider, to a number of individual users at, for example, 
houses, apartment buildings, etc. Typically, the fluid flow lines 
associated with a gas distribution system are disposed underground and 
have regulators, valves and/or other fluid flow control components 
disposed at advantageous control points within the lines. The control 
components regulate the flow of gas from a high-pressure side associated 
with the fluid provider to a low-pressure side associated with a fluid 
user. 
To aid in the maintenance of, for example, gas lines, the regulators, 
valves and other components at a control point are disposed in 
above-ground stations or pit assemblies that allow access to these 
components. Pit assemblies are usually located underground and are large 
enough so that a service person can enter the pit assembly to access, 
test, repair and/or replace the regulators or other flow control 
components within the pit assembly. 
In a standard configuration, each pit assembly includes two sets of 
redundant regulators connected in parallel between a gas inlet (coupled to 
a gas provider) and a gas outlet (coupled to a gas user). One of these 
sets of regulators comprises a main flow line that is used to control 
fluid flow during normal operation of the gas system while the other set 
of regulators comprises a backup line that remains unused while the main 
line is operational. In another standard configuration, two pit assemblies 
are placed in series separated by a length of pipe, per local 
requirements, with one set of regulators in each pit assembly. During 
operation, one of these sets of regulators may be used to actively control 
fluid flow during normal operation of the gas system while the other set 
of regulators may comprise a backup line that monitors flow when the 
active set is operational (a worker/monitor set-up). Alternatively, both 
of these sets of regulators may be used to control fluid flow during 
normal operation so as to maintain an intermediate pressure between the 
pit assemblies (a series regulator set-up). In either of these cases, 
by-pass lines would be included to allow isolation of the regulator sets 
from the main line. 
When one or more of the regulators or other components associated with the 
main line needs to be tested, repaired or replaced, the backup or by-pass 
line is switched into use to provide a constant flow of gas to the gas 
users. Thereafter the main line is disassembled and the components thereof 
are tested, repaired or replaced as necessary. This disassembly procedure 
can take a significant amount of time due to the number of nuts, bolts, 
and other fasteners which must be removed to disassemble the components of 
the main line. During this time, surface traffic flow around the 
installation may be disrupted. Furthermore, removal of components of 
either the main line or the backup line is impaired by the limited amount 
of space within the pit assembly and by the hard-to-reach nature of some 
of the components within the pit assembly. Sometimes, special precautions 
must also be taken before entering a pit assembly to perform test, repair, 
or maintenance work. Such precautions may include venting the pit 
assembly, which requires an external air supply and adds to the time and 
cost associated with performing maintenance. It is desirable to reduce the 
size of a pit assembly and to make fluid flow lines less expensive to 
build and faster, safer and easier to maintain. 
SUMMARY OF THE INVENTION 
The present invention is directed to a flow-control assembly disposed 
within a pit assembly in a manner which allows the flow-control assembly 
to be easily and quickly removed and replaced without requiring a service 
person to actually enter or crawl down into a pit assembly. This 
flow-control assembly also enables a pit assembly to be reduced in size 
because the pit assembly does not need to provide space for a service 
person to enter the pit assembly. Smaller pit assembly size means less 
space is required for installation and may help to reduce installed 
station cost. Reduced pit assembly size also eliminates the possibility of 
a service person entering a pit assembly which removes the dangers 
associated with entering confined spaces. 
According to one aspect of the present invention, a flow-control assembly 
includes one or more rigidly connected fluid control components, such as 
regulators, valves etc., and coupling mechanisms disposed on each end 
thereof. The coupling mechanisms are configured to engage a fluid inlet 
pipe and a fluid outlet pipe within a pit assembly in a sealed manner. 
Preferably, the coupling mechanisms comprise female or male coupling ends 
that mate with male or female coupling ends disposed on the fluid inlet 
and outlet pipes. If desired, the seal may be provided by an O-ring seal 
disposed in, for example, the female coupling ends. 
In one embodiment, the flow-control assembly includes a fluid passageway 
with a 180 degree bend therein so that the coupling ends on each end of 
the flow-control assembly simultaneously couple to or decouple from the 
coupling ends disposed on the fluid inlet and outlet pipes by movement of 
the flow-control assembly in one direction. 
The flow-control assembly may also include a mounting bracket adapted to be 
mounted on and fixed to a bracket disposed within the pit assembly to hold 
the flow-control assembly in sealed engagement with the fluid inlet and 
outlet pipes. The flow-control assembly may also include a handle disposed 
along the center of gravity thereof at an upper portion of the 
flow-control assembly to allow easy removal of the flow-control assembly 
from the pit assembly. In a preferred embodiment, the flow-control 
assembly is a rigid, single-piece assembly, having all of the components 
thereof welded or otherwise rigidly connected together.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, a flow-control assembly 10 constructed according 
to the present invention is disposed within a pit assembly 12 having a 
lower portion or can 14 and a cover assembly 16 disposed on the can 14. 
The cover assembly may be, for example, welded onto the can 14 and opened 
in a hinged manner. The pit assembly 12 is preferably constructed for use 
underground with the cover assembly 16 being disposed in an accessible 
manner. A number of bolts 18, for example, four, may be loosened to allow 
the cover assembly 16 to be opened and thereby provide access to the 
flow-control assembly 10. Of course, any other desired closure mechanism 
may be used with the pit assembly 12. FIG. 2 illustrates a top view of the 
flow-control assembly 10 with the cover assembly 16 of the pit assembly 12 
opened. 
As illustrated in FIG. 1, the flow-control assembly 10 is coupled between a 
fluid inlet pipe 22 coming from a fluid source nd a fluid outlet pipe 24 
going to a fluid user. The fluid outlet pipe 24 includes an extension pipe 
26 rigidly connected to the can 14 by a bracket 28 (illustrated in detail 
in FIG. 2). 
The flow-control assembly 10 is coupled to the fluid inlet pipe 22 via a 
first coupling mechanism 29 having a female coupling end 30 (illustrated 
in FIG. 1 in cross-section) disposed on the flow-control assembly 10 and a 
male coupling end 31 disposed on the fluid inlet pipe 22. The male 
coupling end 31 mates with the female coupling end 30 in a sliding manner. 
The female coupling end 30 is fluidly connected to a first regulator 32 
which, in turn, is fluidly connected to a second regulator 34. FIGS. 3 and 
4 illustrate the regulator bodies of, and the fluid passageways within, 
the regulators 32 and 34 in more detail. The regulators 32 and 34 may 
comprise pilot-operated regulators, such as the 399A regulator 
manufactured by Fisher Controls Regulator Division, or may be any other 
desired type of regulator, valve or other control component for 
controlling fluid flow between the fluid inlet pipe 22 and the fluid 
outlet pipe 24 in any desired manner. Of course the regulators 32 and 34 
may be the same or different types of regulators or other components as 
desired. 
The regulator 34 is rigidly connected to a 180 degree bend return pipe 36 
which, in turn, is coupled to the extension pipe 26 via a second coupling 
mechanism 37. The coupling mechanism 37 has a female coupling end 38 
(illustrated in FIG. 1 in cross-section) disposed on the return pipe 36 
and a male coupling end 42 disposed on the extension pipe 26 so that the 
male coupling end 42 mates with the female coupling end 38 in a sliding 
manner. O-rings 44 are disposed within, for example, the female coupling 
ends 30 and 38 to seal the fluid line at those connection points when the 
flow-control assembly 10 is properly installed within the pit assembly 12. 
If desired, the female coupling ends 30 and/or 38 may be disposed on the 
pipes 22 and/or 26 while the male coupling ends may be disposed on the 
flow-control assembly 10 in any fashion to provide a sealed engagement 
between the flow-control assembly 10 and the fluid inlet pipe 22 and the 
fluid outlet pipe 24. 
The flow-control assembly 10 may include a bracket 50 rigidly attached to 
the regulator 34 and/or the return pipe 36. The bracket 50 is designed to 
mate with a bracket 52 rigidly attached to the an inner wall of the can 14 
of the pit assembly 12. As illustrated in FIG. 2, the bracket 50 includes, 
for example, two bolt holes which accept nut and bolt assembles 54 
associated with the bracket 52. The bolts of the nut and bolt assemblies 
54 may be welded to the bracket 52 so that the holes of the bracket 50 can 
be inserted over these bolts to align the flow-control assembly 10 with 
the fluid inlet and fluid outlet pipes 22 and 24. When the nuts of the nut 
and bolt assemblies 54 are attached to the bolts and tightened, the 
flow-control assembly 10 is held rigidly in place by the brackets 50 and 
52 to assure a sealed engagement between the ends of the coupling 
mechanisms 29 and 37. 
A further bracket 56 (illustrated in slightly different positions in FIGS. 
2 and 3) may be attached to the flow-control assembly 10 and used to mount 
pilots 64 of the regulators 32 and 34 or to mount any other desired 
equipment. As illustrated in FIGS. 1 and 3, the flow-control assembly 10 
may also include a handle 68 welded or otherwise rigidly attached to the 
flow-control assembly 10. Preferably, the handle 68 is attached to an 
upper portion of the flow-control assembly 10 such as the return pipe 36 
when the flow-control assembly 10 is properly disposed within the pit 
assembly 12. Likewise, the handle 68 is preferably attached to the 
flow-control assembly 10 along the line of the center of gravity of the 
flow-control assembly 10 so that the flow-control assembly 10 may be 
lowered into or removed from the pit assembly 12 in a stable manner using 
only the handle 68. 
In the embodiment of FIGS. 1-4, all of the components of the flow-control 
assembly 10, including the regulators 32 and 34, the return pipe 36, the 
coupling ends 30 and 38, the bracket 50 and the handle 68 are rigidly 
connected together via, for example, welds, to form a single-piece 
flow-control assembly. 
When the flow-control assembly 10 is properly installed within the pit 
assembly 12 as illustrated in FIG. 1, the pilots 64 of the regulators 32 
and 34 may be connected to the extension pipe 26 via a return pipe 70 held 
within the bracket 28. It is understood that the pilots 64 and/or other 
parts of the regulators 32 and 34 may be connected to the return pipe 70 
via tubing not illustrated in FIG. 1. Likewise, the regulators 32, 34 
and/or the pilots 64 associated therewith may also be connected via tubing 
to an exhaust outlet 72 disposed within a wall of the can 14. The exhaust 
outlet 72 enables the flow-control assembly to exhaust fluid out of the 
pit assembly 12 to prevent pressure buildup within the pit assembly 12. If 
desired, the exhaust outlet 72 may be fluidly connected to a recovery 
container or may be vented to the atmosphere. For the sake of simplicity, 
the tubing between the regulators 32, 34, the pilots 64, the fluid return 
pipe 70 and the exhaust outlet 72 are not illustrated in FIGS. 1-4, it 
being understood that the connection of this tubing is known in the art 
and can be performed in any desired manner. 
During operation of the flow-control and pit assemblies 10 and 12, one of 
the regulators 32 and 34, for example regulator 32, may be configured as a 
working regulator while the other of the regulators, for example, 
regulator 34, may be configured as a monitoring regulator having a 
slightly higher downstream pressure set-point than the working regulator 
32. When fluid is provided through the fluid inlet pipe 22 to the working 
regulator 32, the regulator 32 controls the downstream fluid pressure at 
the fluid outlet pipe 24 to remain at a predetermined set-point value. 
When the working regulator 32 operates correctly, the monitoring regulator 
34 operates in an open condition to allow the working regulator 32 to 
control the downstream fluid pressure completely. If the working regulator 
32 malfunctions and allows the downstream pressure to exceed the set-point 
pressure of the monitoring regulator 34, the monitoring regulator 34 
thereafter operates to limit the downstream pressure to the set-point 
value of the monitoring regulator 34. If desired, a safety slam-shut valve 
may be disposed between the working regulator 32 and the fluid inlet pipe 
22. This slam-shut device may detect the downstream pressure and shut off 
the fluid flow through the flow-control assembly 10 if the downstream 
pressure reaches a predetermined amount above the set-point value of the 
monitoring regulator 34 (which occurs if both the working regulator 32 and 
the monitoring regulator 34 malfunction). 
Although the flow-control assembly 10 is described herein as including two 
regulators disposed in series, it is considered that any other number 
and/or any desired types of fluid flow control components, such as valves, 
filters, pressure control devices, etc. may be integrated into or used to 
form a flow-control assembly according to the principles described herein 
for any desired fluid flow control operation. 
As will be evident to those skilled in the art, the flow-control assembly 
10 can be easily and quickly removed from the pit assembly 12 by first 
closing isolation valves upstream of the fluid inlet pipe 22 and 
downstream of the fluid outlet pipe 24, and then loosening the bolts 18, 
opening the cover assembly 16 to expose the flow-control assembly 10, 
removing the nuts from the nut and bolt assemblies 54, removing the tubing 
between the regulators 32, 34, the pipe 70 and the outlet 72, and pulling 
on the handle 68 until the flow-control assembly 10 disengages from the 
fluid inlet and the fluid outlet pipes 22 and 24. A new and identical 
flow-control assembly 10 having functioning components may then be lowered 
into the can 14 until the coupling ends 30 and 38 of the new flow-control 
assembly 10 contact and completely engage the coupling ends 31 and 42 on 
the pipes 22 and 26 and so that the holes in the bracket 50 are disposed 
around the bolts of the nut and bolt assemblies 54. The nuts of the nut 
and bolt assemblies 54 may then be applied to the bolts thereof and 
tightened to hold the flow-control assembly 10 in the fluid flow line in a 
sealed manner. Thereafter, tubing is connected between the regulators 32, 
34, the pipe 70 and the outlet 72 and fluid flow is reestablished through 
the pit assembly 12 by opening the upstream and downstream isolation 
valves. The components of the removed flow-control assembly 10 may be 
tested, repaired and/or replaced at leisure in a suitable working 
environment. 
Because of the ease and quickness associated with removing and replacing 
the flow-control assembly 10, minimal traffic tie-ups are created during 
station testing and maintenance. Also, as will be evident, a service 
provider can quickly remove and replace the flow-control assembly 10 of 
the present invention without having to crawl down into the pit assembly 
12 and without having to remove and replace numerous bolts and nut 
assemblies or other connector fittings. This advantage enables the pit 
assembly 12 to be smaller because the pit assembly 12 does not need to 
provide space for a service provider to enter the pit assembly when 
testing, disassembling and reassembling the fluid flow components within 
the pit assembly. Removal of the need to crawl down into a pit assembly to 
test or maintain equipment provides a significant safety benefit. 
Notably, one of the reasons that the flow-control assembly 10 is so easily 
replaced is that the coupling ends 30 and 38 simultaneously disconnect 
from or connect to the fluid inlet pipe 22 and the extension pipe 26 by 
being moved in the same direction. In effect, one motion (e.g., pulling on 
the handle 68 or lowering the flow-control assembly 10 into the pit 
assembly 12) decouples the flow-control assembly 10 from or couples the 
flow-control assembly 10 to both the fluid inlet pipe 22 and the extension 
pipe 26 without having to remove any bolt and nut assemblies at the 
connection points between the flow-control assembly 10 and the rest of the 
fluid flow line. Furthermore, due to the placement of the brackets 50 and 
52, a service person does not need to get into the pit assembly 12 to 
test, remove or replace the flow-control assembly 10, which shortens the 
time needed to test, remove or replace the fluid flow control components 
within the pit assembly 12. 
While the coupling mechanisms 29 and 37 have been illustrated as having 
female and male ends that sealingly engage each other, other types of 
sealable coupling members may be used instead. Preferably however, the 
couplings used with the flow-control assembly 10 will not use nut and bolt 
or other types of fittings that take a protracted amount of time to engage 
or disengage and/or which require a service person to reach down into or 
crawl down into the pit assembly 12 to engage or disengage. 
While the present invention has been described with reference to specific 
examples, which are intended to be illustrative only, and not to be 
limiting of the invention, it will be apparent to those of ordinary skill 
in the art that changes, additions and/or deletions may be made to the 
disclosed embodiments without departing from the spirit and scope of the 
invention.