Marston’s brewery is a producer of traditional English ales with six breweries on sites across the country. The brewery in Burton on Trent has been brewing beer since 1898, so updating the systems there is a regular occurrence.
Marston’s recently undertook a review of the fine ale room tank level indication system to address certain issues. These were listed as follows: some of the tanks have visual level indication in the form of a sight glass, some however do not. Where there are sight glasses, they are not the most accurate or visible. The sight glasses require cleaning and this proves to be difficult. There is no remote visibility for tank levels. On occasion, the tank can empty allowing gas to be introduced into the beer main, causing issues for bottling.
The proposed solution to overcome the issues was outlined as follows: Install instrumentation to enable accurate tank levels; enable remote visibility by using PLC’s & Scada; enable accurate local visibility by using a digital display, and remove existing sight glasses. It was also deemed necessary to interlock beer transfers using the level indication and use a level switch to prevent gassing the main.
In more detail, this would consist of wiring all of the instrumentation associated with a tank to a local communications module. Then an Ethernet redundant ring would be used to connect all the tanks together, ensuring the highest availability of the equipment. The sensors and associated equipment required would be two PI2796 pressure transducers and one LMT100 level switch per tank, connected to an AL1121 Ethernet field module in each case to communicate the control values to the PLC, and using an E30391 for local display.
When the plan was put into action, the order was placed with ifm for the instrumentation, and with other suppliers for mechanical and electrical installation work, while Marston’s planned to take care of the software side themselves.
The plan allowed for expected costs of around £25,000 and anticipated down time in the order of six days.
Project Review – Design Considerations
It is common practice to measure tank levels using pressure transducers, although in a pressurised vessel the transducer that measures the top pressure is usually located in the top of the tank. When looking at all of the tanks in the Internal Tank Farm, it was noticeable how little space there was at the top of the tanks and how inaccessible they are.
If an instrument fails or requires inspection, it should be easy to access and simple to change it. Marston’s wanted to ensure that the new project assisted the operators/engineers and not to overcomplicate it.
Marston’s decided to install the transducer in the pipe that supplies the top pressure on each tank not only proved to provide the same reading but eliminated the cost of internal scaffolding and has brought all of the instrumentation down to a working level.
Sometimes it can be difficult for engineers to set up instruments that they have not used before, also it is sometimes unknown how the previous instruments were set up before they failed. Utilising advancements in technology and the new products on the market, the system knows what configuration should be on that device then automatically configure the new device that is plugged into the cable.
The project was installed as described on six bright beer storage tanks. [bright beer : after fermentation has finished and the yeast or sediment has been filtered out, clear (bright) beer remains, ready to be served or bottled.] Each of these tanks holds 130 barrels of beer (one Imperial barrel equals almost 164 litres) or just over 210 hectolitres.
Project Review : on completion of the project it was noted that the actual costs had amounted to £23,838.86 instead of the £25,000 forecast, and the time taken was four instead of six days.
An additional benefit came from modifying the tanks. The tanks will shortly require a 10 year thorough test & inspection. As part of the insurance sign off Marstons fulfilled this requirement. Preliminary cuts were made to remove the old sight glasses, and they will be removed soon and tubes kept as spares if required.
Operator feedback so far seems pretty positive, and hopefully this idea will be rolled out to more of the tanks.