CA1322379C - High pressure rod sealing unit for fluid pressure gauges - Google Patents

Abstract

HIGH PRESSURE ROD SEALING UNIT FOR
FLUID PRESSURE GAUGES
-DAN VINH TRAN AND AMBROSE SHIU KI CHUN-ABSTRACT
It is a common problem to devices which are used for segregating the working fluids, such for example as the drilling mud fluid using in drilling rig, from the pressure gauges, that the highly polished cylindrical surfaces for piston sealing are damaged by the solids which are carried by the working fluid. In this invention, a rod sealing mechanism is used to eliminate the above problem. In addition, the spare part which has to be replaced, if necessary, is far more economical, that is, to replace the rod itself instead of the internally-polished cylinder.

Description

~22~9 SPE CIEIC AqlO N

This invention relates to the utilization of rod se~ing in the hydraulically transmitting mechan~sm for f~id pressure measurement by pressure gauges.

In var~ous industries, it is deqira~Le to mea~ure pressure with a device which could segregate the working flllid from the contact of the pressure gauges. Th~s is due to the fact that, ~n many cases, the working f~i~s carry a large propQrtion c~ suspended scili~ls which easily contaminate the ~nternal parts of the p~e gauges and that results in malfunction or inaccuracy of the gauges. Currently, there are three types c~f these devices, namely, diaphragm type, metal disc type and piston type. The former two have similar characte~istic except the use ~ material, that is, the diaphragm type utilizes a rubber diaphragm while the metal disc a thin EI~d}ile me~iL disc. The pre~ure is detected by one side of the stationary diaphragm or metal d~sc and is transmitted to the cther side which con~dsts of usually clean hydraulic fluid~ However, the disadvantage af these types i5 that they are oliLy use~l at low pr~re range. The d~aphragm and metal disc usually fail under the high stress creat~d by high pressure.

The pist~n type was desLgned to s~Lve the above problem under high pre~;ure ap~ ation. ~t usually cor~ists cJE a pdst~n with seals which travbl inside a p~lished cy~inder. The pr~ure oE the working ~id ..~

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acts on one ~ide of the p~ston and ~s transmitted to the other ~ide by moving the paston in either direction. However, the disadvantage of this type of device ~ that -the s(ilids m the working f~l~ids are usually car~ed by the seals oE the piston and ~hus damaqe the internal highly p~ilished cylinder during the actuation, which render the structure moperative. Once the palished cylinder ~s damaged, the com~lete dev~ce becomes usel~ss for the fact that it cannot be repaired.

We have -found that the above problem in high pressure application can be sc~ved by u~}ing a rod sealing mechanism. Because the seals are not mova~e, the s~lids are hardly carried by the actuating p~ilished rod beyond the sealing area of the cylinder. This invention ena~s the device to be more r~liable, durable and economic~ ~:o re~ace spare parts. The oriLy pc~iLe damage occurs on the rod, which is compara~y inexpensive to r,o~ace than the cylinder in the cc nventional devices.

The invention is ill~strated in the accompanying drawing in which:
Fi~ure 1 is a uiew in elevation showing the app]ication o~ this invention to a measurement of press~re af a flow ]ine~
Figure 2 is the sectional view ~f the entire high pr~sure r~d sealing unit with which t~s invention is partic~y concerned.

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To measure the press~e o:E a ilow ]ine 10, it ~s normally connected with a T-Eitting 11 with which a pressure gauge 25 is connected by high pressure hose 24. Because oE the so~i~s in the fll~id may damage the pressure gauge 2S~ a device is interpo~d between the T-Eitting 11 and pressure gauge 25 to segregate the fluids. The application oE our invention in such device is i~l~strated by the r~d seaLing mechanism.

A threaded member 12 is connected to ~he top of the 'r~itting 11 at the end and to an union sub 16 at the other end 26. The union sub 16 is threaded externally, with a rubber seal 21 pLaced in a reces~ed groove 32. When the w~ion sub 16 is tightened by a wing nut 13, the rubber seaL 21 is squeezed by the end Eace oE the lower body 14 oE the high press~lre rod se,~ing unit, thus creating a sealing surfaces Eor high pressure application. In addition, the spherical sl~rEace 29 oE
the lower body 14 and the bevel 30 af the union sub 16 creates a metad~metaL seaL such that should the rubber seal 21 Eail, the high press~re is held by such metal~metal seal. The lower body 14 is a body with internal cylindrical bore. The bottom end clE it has a lip 28 which retains ~he .rod 17 from coming out. The seals 19 and 20 are instalLed in the grooves on the lower body 14. The highLy pc~ished rod 17 is instaJled from the top so that the seals 19, 20 and the rod 17 create the sealing mechanism. Any fluid w;ll be segregat~d from the top to the bottom o seals 19 and 20. The upper body 15 with a seal 18 inst~led in the groove is screwed tight on the threaded portion of the , '.. ~ , : ' , : ' ~3223~

bottom body 14. At the top wall of the upper body 14, there is a threaded port 31. A T~ittin~ 22 is threaded into the threaded ~Lement of the upper body 14. A check valve 23 ~s threaded to one outlet of the T-fitting 22 and a high pressure hose 24 is connected to the other outlet c~ the T~ tting 22. The other end of the hose 24 is connected to the high pressure gauge 25. A desirable incompres~i~e ~id fiUs the hose 24, the T~itting 22 and the space 27 of the upper body lS.
The check valve 23 enables the release of any gaseous components within the said vciLume. As the incompressible fluid is es~ished, the sealing rod 17 will be forced downward ur~til it reaches the ~i~ 28 of the lower body 14. At this stage, the rod sealing unit ~s set for operation.

As the p.ressure is forced through the i~Low line 10, it wi~l rise through the threaded member 12, the union sub 16 and to the bottom end c~E the sealing rod 17. At such a time, the pressure will force the sealing rod 17 upward and ~n turn force the incompre~ible f~id from space 27, through the threaded port 31 to the hose 24. This f~id will then be forced to the pr~isure f~d res~l-s~ve elements of the gauge 25 and thus indicating the pressure of the flow line 10.

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Claims (6)

1. In combination, a pressure rod sealing unit comprising:
an upper body;
a first threaded means inside the lower portion of the upper body;
first groove means located at the top portion of the first threaded means;
a lower body with a spherical surface lower portion;
a second threaded means outside the top portion of the lower body;
second and third groove means located at the inside top portion of the lower body;
first, second and third sealing means installed in the first, second and third groove means respectively for sealing a rod means;
whereby, the upper body and the lower body are connected by the first and second threaded means, and the rod means is moving inside the upper and the lower body through the second and the third sealing means for providing pressure.

2. The pressure rod sealing unit according to claim 1, wherein the spherical surface of the lower body is connected to a union sub by means of a wing nut.

3. The pressure rod sealing unit according to claim 2, wherein the union sub comprises a recessed groove at the upper portion of the union sub.

4. The pressure rod sealing unit according to claim 3, wherein a fourth sealing means is disposed between the spherical surface and the recessed groove of the union sub.

5. The pressure rod sealing unit according to claim 4, wherein said first, second and the third sealing means are o-rings.

6. The pressure rod sealing unit according to claim 4, wherein said first, second and the third sealing means are rubber seals.