GB2519935A

GB2519935A - Bladder accumulator volume indicating device

Info

Publication number: GB2519935A
Application number: GB1315342.4A
Authority: GB
Inventors: Thomas Broadbent; Heath Stephenson
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 2012-08-29
Filing date: 2013-11-01
Publication date: 2015-05-13
Anticipated expiration: 2033-11-01
Also published as: US20150059889A1; GB201215375D0; GB2519935B; GB201315342D0; US9400055B2

Abstract

A mechanical seal support system comprises: a bladder accumulator 3; connections 7, 8 to the top and bottom of the accumulator; and means responsive to the pressures at each of the connections and for providing an output determined by the difference between the pressures. The system includes means 12,13 for displaying the output in a manner indicative of the volume of the fluid in the accumulator relative to a predetermined volume.

Description

Bladder accumulator volume indicating device

Field of the Invention

The invention relates to a method of determining the volumetric level of barrier fluid in a mechanical seal pressure vessel.

Background to the Invention

In an API (American Petroleum Institute) Plan 53B mechanical seal support system a bladder is pre-charged with nitrogen to a predetermined pressure. Once it has been pre-charged with gas it is filled with barrier fluid to the required pressure: 2barg greater than maximum product pressure. During operation, the accumulator is isolated from the gas and the barrier fluid source.

In normal operation it is anticipated that there will be leakage from the mechanical seal which will reduce the barrier fluid volume in the accumulator over time. As the fluid level in the accumulator drops, pressure will be lost. This can result in the contamination of the barrier fluid by the product and may lead to premature failure of the seal. In the worst case scenario, the product could escape and a fire could result from the overheating of the seal. If the leakage rate of the seal is known, it is possible to estimate when the barrier fluid will require refilling. It is a common industry standard that it can be expected for the barrier fluid to require refilling every 28 days or more although this may vary depending on the volume of barrier fluid, the seal leakage rate and the alarm strategy employed. Also, due to unforeseen variations in seal performance or environmental conditions, it is sometimes not possible to predict with accuracy when refilling will be required and so controls need to be implemented.

The existing controls come either in the form of pressure transmitters connected to the accumulator which highlight when the pressure of the barrier fluid has reduced to a particular level and the accumulator needs refilling, or a combination of pressure and temperature transmitters connected to the site distribution control system (DOS). The combination of a pressure and temperature transmitter is sometimes preferable due to changes in ambient temperature affecting the accuracy of the pressure readings. An algorithm in the site DOS system utilises the readings from both the transmitters to calculate the volume of barrier fluid left in the accumulator. If a DOS is not available it has been proposed that individual single loop controllers are used on each 53B system. Any control involving an electrical component will require ATEX approval with the result that these two solutions can be very expensive and difficult for the site to implement. It is therefore the purpose of this invention to provide an alternative means for fluid level detection.

Statements of the Invention

According to the present invention there is provided a mechanical seal support system comprising: a bladder accumulator; a connection to the top of the accumulator and a connection to the bottom of the accumulator; means responsive to the pressures at each of said connections and for providing an output determined by the difference between said pressures; and means for displaying said output in a manner indicative of the volume of the fluid in the accumulator relative to a predetermined volume.

Preferably, the display means is disposed outside the internal volume of the bladder accumulator.

Preferably, the display means is mounted directly adjacent the current stand of the API Plan 53B.

Preferably, at least one manifold connects ports of the accumulator to the pressure responsive means allowing for interference with said pressure responsive means without depressurising the system.

Preferably, there are two manifolds of which one allows pre-charging of the accumulator to be done at the maximum reach of a person in the fifth percentile.

Preferably, the system includes means for of determining the absolute pressure between the two connections.

Preferably, the display means includes means for displaying the compared pressure reading and the absolute pressure reading.

Preferably, the system includes means for transmitting the output to a receiver.

Preferably, the system includes means, responsive to said output, for providing additional fluid to said vessel.

Brief Description of the Drawings

The accompanying drawings are as follows: Figure 1 illustrates the API Plan 53B seal support system incorporating a first embodiment of the present invention; Figure 2 illustrates a more detailed view of the seal support system of Figure 1; Figure 3 illustrates in greater detail part of the seal support system of Figure 1; and.

Figure 4 illustrates part of a seal support system incorporating a second embodiment of the present invention.

Detailed Description of the Invention

The present invention will be described, by way of example only, with reference to the accompanying drawings.

Referring to Figure 1 of the accompanying drawings, there is illustrated an API Plan 53B seal support system 1 incorporating the present invention 2. The seal support system comprises a bladder accumulator 3 which connects to a pressure gauge and transmitter 4, and communicating with the mechanical seal loop using an arrangement of pipe work 5.

Referring to Figure 2 of the accompanying drawings, there is illustrated the present invention 2 connecting to the bladder accumulator 3 using only the existing brackets 6 of said bladder accumulator. A pipe 7, vertically extending from the top of said bladder accumulator, provides the present invention with the nitrogen connection from the bladder, while a second pipe 8 provides the present invention with the fluid connection from the bladder accumulator.

These two pipes attach to the accumulator and the present invention using a series of standard connections 9.

Referring to Figure 3 of the accompanying drawings, a panel 1) is mounted so that there is adequate spacing between the accumulator and said panel to accommodate pipework 11. A visual indication signalling feature 12 is mounted on the panel 10 and encases or includes indicating wand 13. A manifold 14 allows nitrogen isolation and ventilation of the system.

The positioning of manifold 14 lowers the pre-charge height so that pre-charging may be performed at an ergonomic level. A second manifold (15) allows for fluid isolation and ventilation of the system with the result that the gauge may be removed or repaired without depressurising the system.

Referring to Figure 4 of the accompanying drawings, a differential pressure transmitter 16 has high and low sides, 17 and 18 connected to a five valve manifold 19, the manifold 19 having connections such that oil piessure may be piped in through orifice 20 and gas pressure may be piped in through orifice 21. Additional to the five valve manifold 19 is a three way ball valve 22 which includes a port 23 through which gas may be used to pressurise the system and a drain point 24 where gas may be drained from the system.

With reference to maintenance, there is provided in the five valve manifold 19 valves 25 and 26 which may be used to isolate the differential pressure transmitter 16 from the loop and further valves 27 and 28 which may be used to drain off any excess gas or oil prior to the removal of the differential pressure transmitter 16.

Claims

Claims A mechanical seal support system comprising; a bladder accumulator; a connection to the top of the accumulator and a connection to the bottom of the accumulator; and means responsive to the pressures at each of said connections and for providing an output determined by the difference between said pressures; and means for displaying said output in a manner indicative of the volume of the fluid in the accumulator relative to a predetermined volume.1. A system according to Claim 1 wherein the display means is disposed outside of the internal volume of the bladder accumulator.
2. A system according to Claim 1 or Claim 2, wherein said display means is mounted directly adjacent the current stand of the API Plan 53B.
3. A system according to any of the preceding claims, wherein at least one manifold connects ports of the accumulator to the pressure responsive means allowing for interference with said pressure responsive means without depressurising the system.
4. A system according to Claim 4, wherein there are two manifolds of which one allows pre-charging of the accumulator to be done at the maximum reach of a person in the fifth percentile.
5. A system according to any of the preceding claims, wherein the system includes means for determining the absolute pressure between the two connections.
6. A system according to Claim 6, wherein is the display means includes means for displaying the compared pressure reading and the absolute pressure reading.
7. A system according to any of the preceding claims, wherein the system includes means for transmitting the output to a receiver.
8. A system according to any of the preceding claims; wherein the system includes means, responsive to said output, for providing additional fluid to said vessel.
9. A mechanical seal support system substantially as described herein with reference to Figures 1 and 3 or Figure 4 of the accompanying drawings.