Note: Descriptions are shown in the official language in which they were submitted.
In a machine for hydrostatically testing reinforced
plastic pipe of relatively large diameter, a certain clamping
force against the open ends of the pipe is required to seal the
ends when the pipe contains water at zero gauge pressure.
Additional clamping force is re~uired to oppose the force
generated by increasing the internal water pressure to the
maximum test pressure. Should the maximum clamping force be
applied before the internal pressure in the pipe i5 increased
from zero gauge pressure, or if the internal pressure is released
suddenly from maximum test pressure to zero gauge pressure while
the maximum clamping force is applied, the machine is likely
to crush the ends of the pipe. An object of the invention is
to provide a pipe testing machine having an automatic control
system preventing crushing of the pipe.
According to a further aspect of the present invention
a pipe testing machine compris~es a pair of spaced clamping plates,
hydraulic actuating means for moving one of the clamping plates
selectively toward and away from the other for respectively
clampiny and unclamping a pipe therebetween at opposite ends,
hydraulic pumping means for supplying hydraulic flllid under
pressure to the actuating means to seal the ends of the pipe,
means for filling the clamped pipe with water through one of the
clamping plates, means for increasing the water pressure in the
pipe to test the pipe, means for sensing the magnitude of the
water pressure in the pipe, and means for proportioning -the
hydraulic fluid pressure in the actuating means -to the sensed
maynitude of the water pressure.
According to a further aspect of the present invention
a pipe testing machine comprises a pair of spaced clamping plates,
means for applying clamping pressure to the clamping plates to
. .
4~
seal opposite ends of a test pipe against internal test pressure,
means for subjecting the test pipe to internal fluid pressure,
means for continuously sensing the magnitude of the internal
pressure in the pipe and providing an electrical signal varying
in magnitude in accordance with the magnikude of the internal
pressure in the pipe, and electrically adjustable modulating
means for receiving the electrical signal and proportioning the
clamping pressure to the sensed internal pressure.
According to a further aspect of the present invention
a pipe testing machine comprises a pair of spaced clamping ~
members, means for applying clamping pressure to the clamping
members to maintain opposite ends of a test pipe sealed against
internal test pressure, means for subje~ting the test pipe to
internal fluid pressure, means responsive to changes in the
internal pressure in the pipe and providing an electrical signal
upon occurrence of such changes ana electrically adjustable
modulating means for receiving the electrical signal and
changing the clamping pressure in response to changes in the
internal pressure.
According to a further aspect of the present invention
a method of testing plastic pipe comprises clamying the pipe at
opposite ends with an initial clamping pressure sufficient for
sealing, subjecting the pipe to internal fluid pressure,
sensing the magnltude of the internal pressure in the pipe,
and proportioning the clamping pressure to the sensed internal
pressure.
Embodiments of the invention will now be described
with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram illustrating the control
system of the invention;
FIG. 2 is a time-pressure graph illustrating testing
cycles for pipes of various diameters; and
FIG~ 3 is a fragmentary sectional view of an end of
a pipe and the adjacent clamp of the testing machine.
According to the present invention a pipe testing
machine comprises a pair of spaced clampin~ plates, means for
supplying clamping pressure to the clamping plates to seal
opposite ends of a test pipe against internal test pressure~
means for subjecting the test pipe to internal fluid pressure,
means for sensing the internal pressure in the pipe and means
for proportioning the clamping pressure to the sensed internal
; pressure.
. With respect to the drawings, a pipe 10 is shown in
FIG. 1 clamped between a stationary clamping plate 11 ana a
movable clamping plate 12 of a hydrostatic pipe testing machine
13. A constant displacement pump 14 supplies hydraulic fluid
such as oil to a hydraulic actuator 16 through a directional
control valve 18. The actuator 16 includes a cylinder 16a, a
piston 16b reciprocable therein, and a piston rod 16c connected
at one end to the piston 16b and at the other end to the movable
clamping plate 12.
.
A water supply pipe 20 is connected to an inlet pipe
21 leading through the stationary clamping plate 11 to the
inside of the pipe 10 and haviny an electrically operable valve
22 therein. The supply pipe 20 is also connected to a pressure
pump 24 having its outlet connected to the pipe 21 downstream of
the valve 22 under the control of an electrically operable valve
26. The pressure of the water supplied to the pipe 10 by the
pump 24.is controlled by an adjustable relief valve or pressure
regulator 27 also connec-ted to the outIet of the pumpO A vent
~24~
pipe 30 extends through the movable clamping plate 12 for venting
water from the pipe 10 either under the control o an
electrically operable primary vent valve 32 or under the control
of an electrically operable controlled vent valve 34 having a
variable orifice.
The outlet from the hydraulic fluid pump 14 is also
connected to a manually adjustable high pressure relief valve 36,
to a p.ressure switch 37 having two sets of contacts operable at
different pressures, and to an electrically adjustable relief or
modulating valve 38. The relief valve 36 is provided with a
manually adjustable pilot relief valve 40 controlled by an
electrically operable valve 42.
The machine 13 is provided with electrical controls
including a sequence control means 44 comprising various switches
and relays and connected to the control valve 42, the pressure
switch 37, the directional control valve 18, the controlled vent
valve 34, the primary vent valve 32, a suitably mounted flow
controlled limit switch 46 subject to pressure of water
discharged through the primary vent valve 32, a reverse pressure
switch 47 ~ounted on the movable clamping plate 12 and subject to
water pressure in the pipe 10, the water supply valve 22, the
pump pressure water supply valve 26, the pump 24, and also in
four different modes to a programmable power supply 48 Eor the
electrically adjustable relief or modulating valve 38.
The electrical controls also include a pressure
transducer 50 mounted on the movable clamping plate 12 and
subject to the water pressure in the pipe 10. The transducer
50 is connected to a power supply and signal conditioner means
52 which supplies the transducer with power and converts the
pressure signal to a level that can be used to establish a
circuit in a program selector 54 connected thereto and comprising
four voltage dividers used selectively one at a -time in accor-
dance with the diameter of the pipe being tested. The program
selector 54 is connected to a millivolt transmit-ter or amplifier
56 which converts the signal from the program selector into a
signal compatible to the input of the programmable power supply
48 for the modul~ting valve 38. The millivolt transmitter 56 is
connected to the programmable power supply 48 through an offset
adjustment means 58. The sequence control means 44 determines
which input to the programmable power supply 48 produces the
output to the modulating valve 38.
FIG. 3 shows the preferred construction of the clamping
plate 11 of FIG. 1. A relatively thick metal plate lla is
covered on the side thereof ~acing the pipe 10 with a rubber
disc 60. A tubular member 62 fitting inside the pipe 10 has an
internal flange suitably removably secured to the plate lla as by
screws. Different sizes of tubular members such as the member 62
are provided for pipe of different diameters.
With the hydraulic fluid pump 14 running, the program
selector 54 adjusted for the diameter of the pipe, the test
pressure set on the relief valve 27~ and the pipe 10 suspended
in plate between the clamping plates 11 and 12, a "START TEST"
pushbutton (no-t shown) is depressed to cause the sequence control
means 44 to shift the directional control valve 18 to clamping
positi.on to feed hydraulic fluid to the left-hand end of the
cylinder 16a as viewed in FIG. 1. The sequence control means
44 opens the control valve 42 at the same time the directional
control valve 18 is shifted to clamping position, thus placing
the hydraulic pressure under the control of the pilot relief
30 valve 40, which for example may be set at 475 pounds per s~uare
~ 3~ 8
inch (p.s.i.). As the cylinder 16a is filling and the piston
16b ls moved to the right, but before the clamping plate 12
engages the pipe 10, the hydraulic pressure probably does not
exceed 200 p.s.i. When the clamping plate 12 engages the pipe
at one end and the other end is in engagemen-t with the clamping
plate 11, the flow of hydraulic fluid to the cylinder 16a ends,
but the hydraulic pressure builds up to the setting of the
relief valve 40. The low pressure set of contacts of the
pressure switch 37 closest for example at 400 p.s.i., signalling
the sequence control means 44 that the clamping plate 12~has
engaged the pipe 10 with sufficient force to seal the ends
: against the rubber discs such as the disc 60. The sequence
control means 44 then opens the water supply valve 22 and the
primary vent valve 32. The pipe 10 fills with water until the
level reaches the top of the vent pipe 30. Water then flows
through the vent valve 32 and closes the limit switch 46,
s.ignalling the sequence control means 44 that the pipe 10 is
substantially full. The sequence control mea.ns 44 up to this
time has, through the "idle" signal to the programmable power
supply 48, been directing the modulating valve 38 to operate,
~ for example, at 600 p.s.i. When the limit switch 46 closes,
- the sequence control means directs the programmable power supply
.. 48 to lock for its reference to the incoming water pressure
signal from the pressure transducer 50, which signal passes
through the signal conditioner 52, the program selector 54, the
millivolt transmitter 56, and the offset adjustment means 58
before entering the programmable power supply 48. The offset
adjustment means 58 may, for example, be set to provide a base
offset equivalent to a controlling pressure of 800 p.sci. for the
moclulating valve 38. Thus, when the limit switch 46 closes and
-- 6
,~
~ ZL~
the sequence control means 44 changes the signal to the
programmable power supply 48 from "idle" (600 p.s.i~) to
"pressure program", and the gauge pressure in the pipe 10 is
substantially zero~ the signal from the pressure transducer 50,
after going through offset adjustment means 58, will be
directing the programmable power supply 48 to adjust the relief
setting of the modulating valve 38 to 800 p.s.i. Then, as the
pressure in the pipe 10 is increased for the test, the signal
from the pressure transducer 50 will increase and direct the
programmable power supply 48 to .increase the relief set`ting
of the modulating valve 38 proportionately above 800 p.s.i.
When the limit switch 46 closes, the sequence control
means 44 also closes the control valve 42 and cuts off the pilot
relief valve 40. The high pressure relief valve 36 may be set,
for example, to open at 2100 p.s.i. Therefore, when the control
valve 42 closes, the control of the clamping pressure is shifted
to the modulating valve 38. As the hydraulic clamping pressure
increases from the 475 p.s.i. setting of the pilot relief valve
40 toward the 800 p.s.i. base setting of the modulating valve 38,
the high pressure set of contacts of the pressure switch 37
closes, for example at 750 p.s.i~, verifying to the sequence
control means 44 that the program;nable power supply 48 has
shifted from the "idle" to "pressure program" mode and that
control valve 42 has closed. The sequence control means 44 then
closes the water supply valve 22, opens the water pump valve 26,
starts the water pressure pUMp 24, and closes the primary vent
valve 32. The closi.ng of the vent valve 32 allows the limit
switch 46 to open. As the water pressure i.nside the pipe 10
increases, the reverse pressure switch 47 opens, for example at
10 p.s.i. The water pressure increases to the test pressure
determined by the set-ting of the relief valve 27 and the
hydraulic clamping pressure on the pipe 10 increases accordingly
under the control oE the pressure transducer 50, programmable
power supply 48, and modulating valve 38, and in accordance with
the selected setting of the program selector 54. The plastic
pipe expands slightly under the internal pressure.
To end a test, an "END TEST" pushbutton (not shown)
is depressed, causing the sequence control means 44 to close~the
water pump valve 26 and trap the water in the pipe 10 at the
test pressure with the pipe in the slightly expanded condition.
Then -the sequence control means 44 stops the water pump 24 and
opens the controlled vent valve 34. While the pipe 10 contracts
from its slightly expanded condition back to its normal condition,
the variable orifice o~ the controlled vent valve 34 allows the
water in the pipe 10 to escape gradually and the pressure to
decline suficiently slowly to enable the hydraulic clamping
pressure to be proportionately reduced therewith under the
control of the sensing pressure transducer 50, programmable power
supply 48, and modulating valve 38. When the water pressure has
20 decreased to the 10 p.s;i. setting of the reverse pressure
switch 47, the switch 47 closes and the sequence control means
44 closes the controlled vent val.ve 34, shifts the programmable
power supply 48 to its "idle" mode from the "pressure progxam"
mode of operation, thus effectlng control of the modulating
valve 38 at 600 p.s.i., opens a drain valve (not shown)
connected to the pipe 10 through the clamping plate 11, and opens
the pri.mary vent valve 32 to allow free flow of air into the
pipe 10 to displace the exiting water~ After a predetermined
time, the se~uence control means 44 shifts the programmable
water supply 48 from its "idle" to the "open" mode of operation,
~%~
whereill it directs the modulating valve to opexate, for example,
at 2000 p.s.i., shifts the directional control valve 18 to
clamp opening position, and closes the primary vent valve 32
and the drain valve (not shown). After the clamping plate 12 has
been retracted out of the pipe 10 by the piston 16b, it closes a
limit switch lnot shown~ which signals the sequence control
means 44 to shift the directional control valve 18 to a neutral
position and to shift the programmable power supply 48 from its
"open" to the '~idle" mode of operation.
The test cycle is illustrated in FIG. 2 r wherein
"clamp" means the movable clamping plate 12, "PS-l" means the low
pressure set of contacts of the pressure switch 37, "vent" means
the vent pipe 30, "PS-2" means the high pressure set of contacts
of the pressure switch 37l "pressure pump" means the water
pressure pump 24, "blocking valve" means the water pump valve 26,
"control vent" means the controlled vent valve 34, and "PS-3"
means the reverse pressure switch 47. Programs 1, 2, 3 and 4 of
the program selector 54 are for pipes of successively decreasing
diameter. As shown, for program 1, the pipe can be tested to a
water pressure of about 125 p.s.i. with clamping pressure in the
cylinder 16 a of about 2000 p.s.i. The higher water test
pressures for programs 2, 3, and 4 are accomplished with lower
unit clamping pressures because of the reduced cross sectional
areas of pipe to be clamped.
Various modifications may be made in the testing
machine shown and described without deporting from the spirit
and scope of the invention.
. _ g _
,~
.
, '
