GB2256472A - Condensate traps. - Google Patents

Abstract

A condensate trap comprises a valve (10) disposed within a casing (4), and a sensor unit (18) for monitoring the performance of the valve. The sensor unit comprises a downwardly directed passage (16) having an inlet (14) at its upper end, and a sensor element (26) at its lower region. An upper region of the passage (16) has an outlet port (30) which communicates with the valve (10). There is a square tube (34) fitted coaxially within the passage. The corners of the tube contact the wall of the passage, leaving flow passageways between the faces of the tube and the wall of the passage. These flow passageways communicate with the interior of the tube at both ends of the tube. When the valve (10) is open, condensate in the passage (16) can flow to the outlet around the bottom of the tube (34) and up the passageways between the tube (34) and the wall of the passage (16). When the valve (10) is closed, the pressures at the inlet (14) and the outlet post (30) can be equalised by flow through gaps between the top end of the tube (34) and the wall of the passage. If the valve does not close properly and a large leakage occurs, condensate will be forced out through the valve and the level will fall to expose the sensor which will react to provide an alarm signal. <IMAGE>

Description

CONDENSATE TRAPS This invention relates to condensate traps, and more particularly to the monitoring of the condition of a condensate trap.

Condensate traps are commonly used in steam systems (in which circumstances they are usually referred to as steam traps"). Their function is to discharge condensed water from the system, without allowing steam to escape. If steam is lost from the system, this represents a waste of energy. Steam traps thus commonly comprise a valve which is responsive to the presence of condensate or steam in the vicinity of the valve, so that the valve opens when condensate is present, and closes when steam is present.

Occasionally, however, a steam trap can fail to close, or can close only partially, which permits the continued leakage of steam after the valve should have closed. It is not always easy to detect this condition, and various monitoring arrangements have been devised so that an alarm is given if a steam trap malfunctions.

According to the present invention, there is provided a condensate trap comprising a valve for controlled discharge of condensate and a sensor unit for monitoring the performance of the valve, the sensor unit being disposed upstream of the valve, with respect to the flow direction through the trap during condensate discharge, and comprising a downwardly directed passage having an inlet at its upper end, a lower region of the passage containing a sensor element and an upper region of the passage having an outlet port, situated below the inlet, which port communicates with the valve, a tube being fitted coaxially within the passage, which tube surrounds the sensor element and extends upwardly beyond the outlet port, the outer periphery of the tube contacting the wall of the passage at positions around the tube, and being spaced from the wall of the passage at regions between those positions to provide flow passageways between the tube and the wall of the passage, the flow passageways communicating with the interior of the tube at both ends of the tube.

In a preferred embodiment in accordance with the present invention, the passage has a circular crosssection, and the tube has a polygonal cross-section.

The tube may, for example, have a square or triangular cross-section.

The passage may have a reduced cross-section at its upper region, against which the upper end of the tube abuts.

The passage may comprise a lower region, at which the outer periphery of the tube contacts the wall of the passage, and an upper region, in which the outlet port is situated, and in which the outer periphery of the tube is spaced from the wall of the passage all around the tube. Consequently, in this upper region, an annular chamber is provided around the outside of the tube. The lower region of the passage may be provided in a fitting which is secured within a bore defining the upper region of the passage.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a partially sectioned view of a steam trap; Figure 2 is a sectional view of the steam trap of Figure 1; and Figure 3 is an end view of a sub-assembly of the steam trap of Figures 1 and 2.

The steam trap shown in Figures 1 and 2 comprises a body 2 and a cap 4. The cap 4 is secured to the body 2 by bolts 6, and defines a valve chamber 8. A temperature-responsive valve assembly 10 is accommodated within the valve chamber 8 and is operable to open and close a valve controlling flow between the valve chamber 8 and an outlet 12 formed in the body 2.

The operation for the valve assembly 10 is known, and will not be described in detail.

The body 2 also has an inlet 14 which communicates with a downwardly extending bore 16. The lower part of the bore 16 is screw threaded, and receives a sensor unit 18. The sensor unit 18 comprises a hexagonal headed fitting 20 having a cylindrical bore 22. The lower end of the bore 22 is screw threaded, and receives a sensor 24 having a sensor element 26.

The bore 16 is cylindrical and has, at its upper end, a tapered transition 28. An outlet port 30 is provided in the bore 16, above the upper end of the fitting 20, and provides communication between the bore 16 and the valve chamber 8 through a passage 32.

A tube 34, of square cross-section, is situated within the bore 22 of the fitting 20, and extends through the bore 16 to engage the tapered region 28.

At its lower end, the tube 34 contacts a shoulder 36 of the sensor 34.

Because the tube 34 has a square cross-section, it contacts the bore 22 in the fitting 20 only at its corners, leaving segment-shaped passageways 38 between the sides of the tube 34 and the wall of the bore 22.

At the region of the tube 34 extending through the bore 16, the tube 34, except at its upper end, is spaced from the wall of the bore 16 around its entire periphery, to define an annular chamber 40, into which the outlet port 30 opens.

At its upper end, the tube 34 engages the tapered region 28 at its corners only, so defining segmentshaped apertures which provide communication between the inlet 14 and the annular chamber 40.

In use, the steam trap shown in Figures 1 and 2 will be fitted at a lower region in a pipe run of a steam system, with the inlet 14 connected to the pipe, and the outlet 12 to a return pipe work leading back to a steam generator. Condensed water forming within the steam system will drain to the inlet 14 and will enter the steam trap, eventually causing a reduction in temperature at the temperature-responsive valve assembly 10, so causing the valve to open. The condensed water will then be discharged through the outlet 12 under the internal pressure in the steam system. When most of the condensed water has been discharged, steam will be able to bubble past the water at the lower end of the tube 34, and so flow through the valve chamber 8. This raises the temperature of the valve assembly 10 causing the valve to close.

Further condensed water will then accumulate in the steam trap, causing the opening and closing cycle to begin again.

Even a small amount of condensate in the steam trap will, under normal conditions, cover the sensor element 26 when the steam trap is closed. Leakage past the valve assembly 10 from the valve chamber 8 to the outlet 12 will cause a drop in pressure in the valve chamber 8. A small amount of leakage is acceptable, and the corresponding small pressure drop in the valve 8 can be met by flow from the inlet 14 through the segment-shaped apertures at the top end of the tube 34 to the outlet port 30. This does not significantly affect the level of condensed water in the sensor unit 18, as indicated by the line 42 in Figure 2.However, if severe leakage occurs, the resulting relatively large pressure drop in the valve chamber 8 will require a flow rate greater than can be accepted by the segment-shaped apertures at the top end of the tube 34, and the pressure drop will therefore cause the level of condensate 42 to drop, displacing water from the lower end of the tube 34 through the passageways 38 to be chamber 40, and thence through the outlet port 30.

Eventually, the level of the water 42 will drop below the level of the sensor 26, and the sensor unit 24 will react to provide an alarm signal, indicating unacceptable leakage of steam.

The use of the square tube 34 provides a simple means of achieving the desired flow path in and around the sensor unit 18, without requiring any major machining operations on the tube 34, for example, the drilling of holes. The cooperation between the square tube 34 and the bore 22 provides adequate centring of the tube 34 within the sensor unit 18, by contact at the corners of the tube 34, while providing the passageways 38 between the sides of the tube 34 and the wall of the bore 22. Also, the cooperation between the top end of the tube 34 and the tapered region 28, and between the bottom end of the tube 34 and the shoulder 36, provides communication between the interior of the tube 34 and, respectively, the chamber 40 and the passageways 38.

In the embodiment described above with reference to the drawings, the tube 34 has a square crosssection. It will be appreciated that other polygonal cross-sections, for example, triangular, could also be used, depending on the relative flow cross-sections required between the interior of the tube 34 and the passageways 38. Similarly, the tube 34 need not have the shape of a regular polygon, provided that it cooperates with the passage defined by the bores 16 and 22 in such a way as to provide the desired flow characteristics.

Claims (7)

1. A condensate trap comprising a valve for controlled discharge of condensate and a sensor unit for monitoring the performance of the valve, the sensor unit being disposed upstream of the valve, with respect to the flow direction through the trap during condensate discharge, and comprising a downwardly directed passage having an inlet at its upper end, a lower region of the passage containing a sensor element and an upper region of the passage having an outlet port, situated below the inlet, which port communicates with the valve, a tube being fitted coaxially within the passage, which tube surrounds the sensor element and extends upwardly beyond the outlet port, the outer periphery of the tube contacting the wall of the passage at positions around the tube, and being spaced from the wall of the passage at regions between those positions to provide flow passageways between the tube and the wall of the passage, the flow passageways communicating with the interior of the tube at both ends of the tube.

2. A condensate trap as claimed in claim 1 in which the passage has a circular cross-section, and the tube has a polygonal cross-section.

3. A condensate trap as claimed in claim 2 in which the tube has a square cross-section.

4. A condensate trap as claimed in any preceding claim in which the passage comprises a lower region, at which the outer periphery of the tube contacts the wall of the passage, and an upper region, in which the outlet port is situated, and in which the outer periphery of the tube is spaced from the wall of the passage all around the tube.

5. A condensate trap as claimed in claim 4 in which the passage has a reduced cross-section at its upper region, against which the upper end of the tube abuts.

6. A condensate trap as claimed in claim 4 or 5 in which the lower region of the passage is provided in a fitting which is secured within a bore defining the upper region of the passage.

7. A condensate trap substantially as described herein, with reference to and as shown in the accompanying drawings.