Blowout preventor test system

A blowout preventor test system utilizes a pipe nipple being threaded, for example, at both ends, and having a central bore through which fluid can be conveyed. At the central portion of the bore is a reduced orifice which constricts flow through the bore. Trapped through the walls of the nipple, on either side of the orifice, are instrumentation taps for attaching a differential pressure recording device having dual pins and a recorder chart. To ensure during testing of the BOP stack that each and every ram on a BOP or blowout preventor stack is properly tested, the orifice within the test nipple provides a restriction in flow which will be apparent from an inspection of the recorder chart. Different readings of pressure drop are produced by the test pin if in fact on each ram, the BOP stack is pressurized and exhausted. Thus, there is provided a means for the inspector to know whether or not each and every ram is inspected.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates to a blowout preventor and methods of testing 
blowout preventors used in the drilling of oil and gas wells. 
Even more particularly, the present invention provides a method for testing 
successive rams on a blowout preventor stack which test system discourages 
attempts to only test a single ram rather than each and every one. 
General Background 
In the control of oil and gas wells, blowout preventor stacks are known for 
the control of the well in the event that the well comes in too quickly to 
be controlled by the drilling mud which is normally used for such control. 
Often the BOP or blowout preventor stacks utilize a plurality of ram type 
preventors or annular type preventors. The safety of personnel working on 
an oil or gas drilling structure depends to a degree upon the precise 
operation of the blowout preventor stack. Thus, a testing of the stacks on 
a regular basis is desirable. 
A problem in the testing of blowout preventor stacks involves the failure 
of personnel at the rig to spend the time and effort to test each and 
every ram or bag preventor in sequence. Indeed, the test could be run on a 
single ram and the same ram left shut and pressured up each time so that a 
chart or other instrumentation device with a recorder would appear to show 
a plurality of different tests, when in truth the same ram was in fact 
tested continually. It is to this problem that the present invention is 
directed. 
General Discussion of the Present Invention 
The present invention provides a test nipple apparatus for use in the 
testing of BOP or blowout preventor stacks. The present invention also 
provides a system for inspecting the testing of BOP stacks. 
The present invention thus provides a BOP testing system in which a nipple 
is provided which has a central bore with an orifice installed in the 
bore. Instrumentation ports are provided on each side of the orifice with 
the nipple being installed in the line to bleed off the pressure from the 
blowout preventor stack after each test. A quick opening valve is 
installed on the end of the orifice nipple to release the pressure from 
the BOP and through the test nipple at the end of each test. The rate of 
opening of the valve would be the same for each test of each ram. A two 
pin bellows type chart recorder, for example, is used to record the test. 
One pin is attached by appropriate instrumentation lines to each side of 
the orifice nipple respectively to the pair of instrumentation ports which 
are provided in the wall of the test nipple and communicating with its 
bore. As the first ram or bag preventor of the blowout preventor stack is 
pressured up to a desired test pressure or PSI, the two pins will have the 
same pressure reading. The pressure is maintained on the blowout preventor 
stack for the desired test period (e.i., a number of minutes) after which 
the test is finished and the quick opening valve is opened to release 
pressure from the BOP stack. As this pressure is released, the 
instrumentation line to the pin on the downstream side of the orifice 
would experience a rapid pressure drop and record this pressure drop on 
the chart. The pin on the upstream side of the orifice will sense a slower 
drop in pressure as fluid bleeds off through the orifice giving a base 
line to follow on the other tests. Each ram or bag would be tested in 
order, in the same manner as above mentioned. The time distance of 
bleed-off will show the ram being tested. Any different type of fluid 
could be used to test the BOP stack including water, drilling mud, and the 
like with the more viscous or heavier fluids bleeding off through the 
orifice at slower time periods.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 through 3 illustrate the preferred embodiment of the apparatus of 
the present invention designated generally by the numeral 10. FIG. 1 
provides a schematic illustration of a blowout preventor or BOP stack 20 
which is being tested. BOP stack 20 would be connected through suitable 
instrumentation lines designated schematically as 25 in FIG. 1, to test 
nipple 30, which is more particulary shown in FIGS. 2 and 3. 
In FIG. 1, nipple 30 provides an inner bore 32 which at its central portion 
is of reduced diameter at orifice 35. Instrumentation lines 40, 42 connect 
at one end portion to nipple 30 respectively at ports 37, 38 and connect 
at their other end portion to recorder 50 which could be, for example, a 
bellows type differential pressure recorder which is commercially 
available and conventional differential pressure recorder. A quick opening 
valve 60 attaches to nipple 30 at end portion 33 while instrumentation 
line 25 completes a connection of BOP 20 to nipple 30 at end portion 34 of 
nipple 30. 
Connections 51, 52 are provided on differential pressure recorder 50 which 
allow for the attachment respectively of the instrumentation line 40, 42 
thereto. 
FIGS. 2 and 3 show more particularly the construction of nipple 30. Nipple 
30 provides a cylindrical annular wall 31 which defines therewithin a 
continuous bore 32. Bore 32 is provided from threaded end portion 33 of 
nipple 30 to the other end portion 34 thereof. 
A thickened portion of wall 31 is provided at the central portion of bore 
32 which thickened zone is indicated in FIG. 2 as 36. This thickened 
portion defines an orifice 35 which as will be described more fully 
hereinafter provides a constriction for flow traveling through bore 32 
between threaded end portions 34, 33. 
Returning to FIG. 1 in the drawings, there can be seen BOP stack 20 which 
normally would be comprised of a plurality of rams which are indicated in 
FIG. 1 as annular ram 22, top pipe ram 24, blind ram 26, and bottom ram 
28. These rams are tested sequentially by closing each individual ram in 
sequence during its testing and putting a test plug at the bottom of the 
BOP stack which plug is indicated in FIG. 1 as test plug 70. When each ram 
in sequence is closed, the area below it pressurized for a period of time, 
with the area between the test plug and the particular closed ram being 
pressurized with fluid (water, drilling mud or the like). 
Each sequential ram is then closed and subjected to pressurization in order 
to test it. Each ram 22-28 or annular preventor bag is thus tested in 
order and in the same manner. The time difference of bleed-off will show, 
with the rams being tested in this sequential fashion. This is because the 
first instrumentation line 40 adjacent valve 60 will drop the pressure 
rapidly while line 42 will drop in pressure slowly because of the 
constriction provided in the form of orifice 35. 
Nipple 30 could be of any suitable structural material such as steel or the 
like as is known the construction of pipe with a heavy duty wall thickness 
being preferable. 
Or in one example constriction, nipple 30 was a 12 inch long by 2 inch 
diameter nipple having one-fourth inch NPT threads and being threaded at 
each end. 
Because many varying and different embodiments may be made within the scope 
of the inventive concept herein taught, and because many modifications may 
be made in the embodiments herein detailed in accordance with the 
descriptive requirement of the law, it is to be understood that the 
details herein are to be interpreted as illustrative and not in a limiting 
sense.