GB2374145A

GB2374145A - Recording pressure of a gas

Info

Publication number: GB2374145A
Application number: GB0207692A
Authority: GB
Inventors: Michael Terrence Cashman
Original assignee: Lattice Intellectual Property Ltd
Current assignee: Lattice Intellectual Property Ltd
Priority date: 2001-04-06
Filing date: 2002-04-03
Publication date: 2002-10-09
Also published as: GB0108669D0; GB0207692D0

Abstract

A method and apparatus for monitoring and recording the pressure of a combustible gas is disclosed. The apparatus comprises a pressure gauge 30 and a pressure recorder 40 which has a mechanical movement to reduce the likelihood of sparking which could cause an explosion in the combustible gas. The apparatus may be connected to a source of gas using a flexible hose 50 with a releasable connection 51 .The mechanical movement may be a mechanical motor (41, fig.3) wound by a key (42).

Description

MONITORING AND RECORDING PRESSURE The present invention relates to monitoring and recording pressure, particularly the pressure of combustible gases such as fuel gas passing through pipes.

Pressure gauges to monitor pressure and chart recorders to record measured pressures are known. Chart recorders generally have a pointer which moves in a manner indicative of the current pressure being measured and are arranged to mark a roll of paper wound underneath the pointer to provide a record of the pressure during a particular period of time. The roll of paper is wound under the pointer using an electric motor to provide a constant rate of movement of the roll of paper. However, the use of an electric motor and its associated power source could cause sparks and an explosion when used to record the pressure of combustible gases such as fuel gas passing through the pipes.

According to the present invention, there is provided a method of monitoring and recording the pressure of a combustible gas, the method comprising monitoring pressure using a pressure gauge and recording pressure over time using a pressure recorder where the pressure recorder has a mechanical movement. The mechanical movement is preferably for moving a markable medium such as paper at a substantially constant rate relative to a marker for making a mark indicative of the pressure.

As the pressure recorder has a mechanical movement, there is a much reduced risk of explosion of the combustible gas, the pressure of which is being monitored and recorded.

The pressure recorder preferably has a movable pointer, the movement of which is dependent upon the pressure of the gas being measured, mechanical means for moving a markable medium such as paper at a substantially constant rate over time and the pointer being arranged to be provided with a marker such as a pen or pencil to make a mark indicative of the measured pressure on a markable medium moved underneath the marker.

The mechanical means for moving paper is preferably a wind-up motor. The mechanical means is preferably arranged to rotate a piece of paper such that the pressure indicated by a mark made on the piece of paper is dependent upon the distance of the mark from the point of rotation of the piece of paper.

The pressure gauge and recorder are preferably connectable to a source of gas, the pressure of which is to be measured, by a flexible hose. The flexible hose preferably has a fitting that enables the flexible hose to be quickly and easily connected and disconnected from a source of gas, the pressure of which is to be measured.

According to a second aspect of the present invention, there is provided an apparatus for monitoring and recording the pressure of a combustible gas, the apparatus comprising a pressure gauge and a pressure recorder with a mechanical movement. The mechanical movement is preferably arranged to move a markable medium such as paper at a substantially constant rate relative to a marker such as a pen or pencil.

The mechanical movement of the pressure recorder is preferably arranged to move a markable medium such as paper at a substantially constant rate over time and the pressure recorder preferably has a movable pointer, arranged to move in dependence upon the pressure being measured, and arranged to support a marker such as a pen or pencil to make a mark indicative of the measured pressure on a markable medium moved by the mechanical movement.

The various aspects of the invention may be embodied in many ways, but some specific embodiments will now be described by way of example with reference to the accompanying drawings, in which : Figure 1 shows an apparatus according to the invention being used to monitor and record the pressure of a live gas main; Figure 2 shows a front view of the apparatus in more detail; Figure 3 shows a rear view of the apparatus; and Figure 4 shows the pressure recorder in more detail.

Figure 1 shows a live gas main 10 with a mains pressure point 11 from which the pressure of gas within the live gas main 10 can be measured. A test apparatus 20 is provided with a pressure gauge 30 and a mechanically wound circular chart recorder 40 which are each connectable to the mains pressure point 11, in this example via a flexible high pressure hose 50 and internal conduits 60 within the test apparatus 20.

In this example, the internal conduits 60 are connected to an inlet 61 provided on the outside of the test apparatus 20 for connection to the flexible hose 50. The internal conduits 60 comprise a common conduit 62 extending from the inlet 61 and first 63 and second 64 conduits connecting from the common conduit 62 to the pressure gauge 30 and the chart recorder 40 respectively. Each of the first 63 and second 64 conduits may be provided with an isolation valve which can be closed when desired to isolate either or both of the pressure gauge 30 and chart recorder 40 to allow zero pressure checks to be performed. However, in the present example, a three port vent valve 65,66 is provided in each of the first 63 and second 64 conduits. The three port vent valves allow independent isolation of each of the pressure gauge 30 and chart recorder 40, and enable pressure to be vented prior to performing a pressure check to ensure that the gauge 30 and recorder 40 are exposed to atmospheric pressure and that no gas is trapped between the valve 65,66 and the gauge 30 or recorder 40 to ensure that false readings are not recorded.

In contrast to conventional pressure test devices which are permanently welded to a test point 11, in the present invention, the flexible hose 50 may be connectable to the mains pressure point 11 using any convenient releasable connector 51. In this example, the releasable connector 51 is a quick release snap on fitting as is well known in the art. The other end of the flexible hose 50 may be permanently connected to the inlet 61 of the test apparatus 20 or it may be connected by another releasable connector. The test apparatus 20 is provided with supports 21 to raise it off the ground to reduce the effects of the environment such as dampness, frost etc which may be encountered when used outside.

Figure 2 shows a front view of another example of the test apparatus which is provided with a closable door 22 which can be closed to protect the pressure gauge 30 and chart recorder 40 from the environment such as wind and rain which can damage the equipment. The door 22 is provided with a window of transparent material such as perspex through which the pressure gauge 30 can be viewed to monitor measured pressure. The apparatus 20 has a handle 24 to enable it to be easily transported to and from a test location. The outer casing of the test apparatus is strong, durable and relatively light for robustness to withstand prolonged outdoor use and for durability and ease of portability. The casing may contain a pocket 25 to store spare charts for the chart recorder, spare pens etc.

Figure 3 shows a rear view of the test apparatus 20 shown in Figure 2. A mechanical motor 41 which causes rotation of a chart upon which pressure recordings are made is shown. This mechanical motor 41 was supplied by Bristol Babcock Inc and is wound by a key 42. This particular mechanical motor 41 has a dual time movement and is switchable between rotation of a chart at a substantially constant rate of once every 24 hours or once every 7 days. However, a mechanical motor with any convenient rate of rotation can of course be used.

Figure 4 shows the pressure recorder 40 in more detail. A hub 43 which is rotatable by the mechanical motor 41 has a circular paper chart 44 with radial lines 45 indicative of various pressures mounted thereon. In this example, the pressure recorder 40 is arranged to record pressures between 0 and 4 Bar. The innermost radial line 45 of the circular paper chart 44 is indicative of a pressure of 0 Bar, the outermost radial line 45 of the circular paper chart 44 is indicative of a pressure of 4 Bar and radial lines therebetween are indicative of pressures between 0 Bar and 4 Bar. The pressure recorder 40 has a pointer 46 which is pivoted at 47 at the edge of the circular chart. The free end 48 of the pointer points towards the innermost radial line of the circular paper chart 44 when 0 Bar pressure is being measured and recorded and points to the appropriate diameter radial lines 45 as other pressures are measured and recorded. The free end 48 of the pointer is provided with a marker, in this case a chart recorder pen, to mark the recorded pressure as the paper chart 44 is rotated at a substantially constant rate, in this example, either once every 24 hours or once every 7 days.

Claims

CLAIMS 1. A method of monitoring and recording the pressure of a combustible gas, the method comprising monitoring pressure using a pressure gauge and recording pressure over time using a pressure recorder, wherein the pressure recorder has a mechanical movement.
2. A method according to claim 1, wherein the mechanical movement moves a markable medium such as paper at a substantially constant rate relative to a marker for making a mark indicative of a measured pressure.
3. A method according to claim 1 or claim 2, wherein the mechanical movement is provided by a mechanically powered motor for moving a markable medium such as paper at a substantially constant rate over time and the pressure recorder has a pointer, the movement of which is dependent upon the pressure of the gas being measured, and the pointer being arranged to be provided with a marker to make a mark on a markable medium
4. A method according to claim 3, wherein the mechanically powered motor is a wind-up motor.
5. A method according to any of the preceding claims, wherein the mechanical movement rotates a piece of paper upon which pressure indicative marks are made.
6. A method according to any of the preceding claims, in which the pressure gauge and pressure recorder are connected to the source of combustible gas, the pressure of which is to be measured, by a flexible hose.
7. A method according to claim 6, wherein the flexible hose is connected to the source of gas using a releasable connector.
8. A method according to any of the preceding claims, wherein the accuracy of the pressure gauge or pressure recorder is checked by isolating them from the pressure being monitored, venting any gas trapped between the isolation point and the pressure gauge or pressure recorder and comparing the measured pressure with atmospheric pressure.
9. A method substantially as hereinbefore described with reference to the accompanying drawings.
10. An apparatus for monitoring and recording the pressure of a combustible gas, the apparatus comprising a pressure gauge and a pressure recorder with a mechanical movement.
11. An apparatus according to claim 10, wherein the mechanical movement is arranged to move a markable medium at a substantially constant rate relative to a marker.
12. An apparatus according to claim 10 to claim 11, wherein a wind-up motor provides the mechanical movement.
13. An apparatus according to any of claims 10 to 12, wherein the mechanical movement of the pressure recorder is arranged to rotate a markable medium.
14. An apparatus according to any of claims 10 to 13, including a flexible hose for connection to a source of combustible gas, the pressure of which is to be measured and recorded.
15. An apparatus according to claim 14, including a releasable connector for connecting the flexible hose to a source of combustible gas.
16. An apparatus according to any of claims 10 to 15, wherein a three way vent valve is provided between the pressure gauge or the pressure recorder and the supply of gas to isolate the pressure gauge or the pressure recorder from the supply of gas and to vent any gas trapped between the pressure gauge or pressure recorder and the valve when the valve is closed.
17. An apparatus according to any of claims 10 to 16, wherein the apparatus is portable.
18. An apparatus substantially as hereinbefore described with reference to the accompanying drawings.