Field of the Invention

The present invention relates to a vent/drain for a pressure transmitter. More specifically the present invention is directed to a vent/drain for draining fluid from a pressure transmitter so that it will not affect the reading of the pressure transmitter. Background of the Invention

Honeywell sells pressure transmitters, such as its ST3000 pressure transmitter. Pressure transmitters have a vent/drain valve for relieving excess built up fluid which can affect the measurement of the pressure transmitter. The prior art vent/drain valve has several drawbacks which make it almost impossible to collect the discharged fluids, so that they end up adding to the environmental pollution at the customer site. Because of the location of the prior art output port in the bushing of the prior art vent/drain valve, the output port must be oriented relative to the pressure transmitter meter body to prevent the discharge fluid, which can be hazardous or corrosive, towards the operator or the pressure transmitter. This was accomplished by positioning the bushing in the pressure head in such as manner that the vent plug, when in the drain position would be oriented in the desired manner. The prior art vent/drain valve also allowed fluid to flow up the threading between the vent and bushing so that a portion of the fluid discharged from between the vent and bushing, rather than through the output port, as desired.

What is needed is a vent/drain valve for a pressure transmitter which is designed to enable the discharge fluid to be collected and directed into a receptacle, which does not require orientation of the vent/drain valve relative to the transmitter meter body, and where all the discharged fluid is directed through the output port.

Summary of the Invention

Applicants have solved the problems discussed above by inventing a vent plug for use in combination with a pressure transmitter which has a lateral inlet near its conical seat end for allowing fluid under pressure access to an axial throughbore in the vent plug, which allows the fluid to exit axially out the axial outlet of the vent plug. The vent plug may include a fitting at its outer end to allow a flexible clear chemically inert hose to be attached to the vent plug to allow collection of the discharged fluid.

Brief Description of the Figures

Figure 1 shows a pressure transmitter;

Figure 2 shows a top view of the pressure transmitter of Figure 1 ;

Figure 3 is a cross-sectional view of a prior art vent/drain valve in the closed position;

Figure 4 is a cross-sectional view of a prior art vent/drain valve in the open position;

Figure 5 is a cross-sectional view of the inventive vent/drain valve in the closed position; Figure 6 is a cross-sectional view of the inventive vent/drain valve in the open position;

Figure 7 is a top view of the bushing portion of the inventive vent/drain valve;

Figure 8 is a cross-sectional view of the bushing portion of the inventive vent/drain valve taken along lines 7-7 of Figure 7;

Figure 9 is a top view of the vent plug portion of the inventive vent/drain valve;

Figure 10 is a side view of the vent plug portion of the inventive vent/drain valve; Figure 1 1 is a top view of a pressure transmitter showing an alternate embodiment of the inventive vent plug;

Figure 12 is a cross-sectional view of the alternate embodiment vent/drain valve in the closed position, and

Figure 13 is a cross-sectional view of the alternate embodiment vent/drain valve in the open position.

Detailed Description of the Invention

Figure 1 shows a simplified view of an ST3000 pressure transmitter, shown generally at 10, with high pressure (HP) head 12 and a low pressure (LP) head 14. The construction and operation of pressure transmitters is well known in the art and will not be discussed in further detail. Both the HP head 12 and the LP head 14 have vent/drain valves, shown generally at 16. Because the inventive vent plug 16 is identical, it will only be described in connection with the HP head 12.

Figure 2 is an top view of Figure 1 showing the inventive vent/drain valve 16, which consists of a bushing portion 18 and a vent plug portion 20. Fitting 21 connects the pressure head 12 to the process and such fittings are well known in the art. The process fluid passes through fitting 21 into the pressure head cavity 23, as is well known in the art. Over time, the fluid builds up in pressure head cavity 23 and must be drained so that the measurement made by pressure transmitter 10 is not affected by any liquid head build-up. The inventive vent/drain valve 16 is connected to pressure head cavity 23 to allow the pressure head cavity to be drained.

Figures 3 and 4 show the prior art vent/drain valve in the closed and open position, respectively. The vent plug 20 has an inner conical seat end 22 and an outer end 24. In the closed position as shown in Figure 3, the conical seat end mates with the bushing at 26 blocking the bushing inlet 28, and preventing fluid from entering the vent plug chamber 30. The vent plug 20 is threaded into the bushing, and the threading is shown schematically at 32. In the open position, when the vent plug is unthreaded, the bushing inlet 28 is unblocked allowing fluid under pressure from the pressure head cavity 23 to enter the vent plug chamber 30, and then discharge out lateral vent/drain outlet 34. Depending on the orientation of the pressure transmitter 10 as installed, the fluid may discharge in any direction, which is undesirable because the fluid may be corrosive or hazardous. In order to prevent harm to the operator or the pressure transmitter, the prior art vent/drain valve must be oriented relative to the pressure transmitter 10. With this design it has been found to be nearly impossible to collect the discharged fluid, which normally ends up simply adding to the environmental pollution at the customer site. It has also been observed that some fluid flows up the threading between the vent plug 20 and the bushing 18 and sprays out the top of the vent/drain 16, which is also undesirable.

These problems have been overcome in the design of the inventive vent/drain valve 16, shown in Figures 5 and 6, which show the inventive vent/drain valve 16 in the closed and open positions, respectively. Vent plug 20 has been provided with a lateral vent plug inlet 40 which is open on both sides (shown best in Figure 10), which communicates with a throughbore 42 which extends axially through vent plug 20 to an axial outlet 52 in the outer end 44 of the vent plug 20. The outer end 44 consists of the bolt head 46 and an extension 48 for attaching a flexible chemically inert clear

hose 49 to the vent plug 20 to collect the discharge and direct it to a receptacle (not shown). In the preferred embodiment, the hose 49 is made of Tygon®.

Referring now to Figures 7 and 8, the bushing 18 is shown in more detail. The bushing 18 is made of stainless steel or other corrosion resistant material, and communicates with the fluid to be discharged via bushing inlet 28 and which also communicates with vent plug chamber 30. The threading in the bushing is shown in dotted lines in Figure 8.

Referring now to Figures 9 and 10, the vent plug 20 is shown in more detail. The vent plug 20 is made of stainless steel or other corrosion resistant material and has a conical shaped inner seat end 22 and an outer end shown generally at 44, which consists of a bolt head 46 with an extension 48 for attachment to a hose. The threads on the vent plug are shown at 50. The vent plug lateral inlet is shown positioned near the conical seat 22 at 40. Vent plug lateral inlet 40 communicates with throughbore 42 (shown in dotted lines), which extends axially through the vent plug, bolt head 46 and extension 48, terminating in axial outlet 52.

Referring now to Figures 1 1-13, an alternate embodiment of the inventive drain plug 16 is shown in which the bushing 18 has been eliminated by machining the vent plug fitting directly into the pressure head 12 and 14. Because the inventive vent/drain plug 16 no longer needs to be oriented relative to the meter body, the vent plug can be threaded directly into the pressure head 12, and the discharge fluid will always exit along the axis of the vent plug into the flexible hose, for collection.

The above Examples and disclosure are intended to be illustrative and not exhaustive. These examples and description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.