ENERGY EFFICIENCY FEATURE
SIGNED, SEALED, DELIVERED C
Tom Grove, of AESSEAL, explains how a pump seal energy audit can help companies meet sustainability targets as well as improving pump reliability and reducing operational costs
ompanies are increasingly making a commitment to energy efficiency by
appointing energy management or sustainability personnel, often at senior board level. Yet those same companies remain unaware that the potential for significant energy waste may be embedded in operational equipment and processes. On any one pump the power consumed
due to mechanical seal friction accounts for a tiny percentage of the total power consumption. It’s therefore easy to see how this key component of pumps and other rotating equipment can be overlooked by managers seeking to target energy losses and improve efficiency. However, there is a source of additional
energy consumption, and possible waste, in the mechanical seal support systems, or ‘piping plans’ which are a feature across almost all industries. The energy consumed by these piping plans is often overlooked, but it can be considerable. Piping plans supply a clean flush liquid
to seal faces to provide lubrication, prevent overheating and maximise seal reliability. They are central to creating the environment needed for reliable operation and longer seal life. Piping plans generally fall into two
main groups: • Flush, where clean, cool liquid is
injected into the seal chamber to improve the operating environment. • Barrier or buffer, where a secondary
fluid is fed into the space between two co-axial mechanical seals to prevent atmospheric contact with the pumped fluid, improve seal cooling, or to enhance safety.
mechanical seal on the plant. High energy use can be easily identified and reviewed to identify a potentially more efficient seal support configuration. An audit summary will provide the
company with a review of potential opportunities, the investment required to upgrade and the potential returns. It provides a ‘quick-win’ overview, highlighting low hanging opportunities which can deliver significant reductions in energy use for minimal outlay, while also improving the efficiency of seal and support systems and, consequently, pump reliability. A seal energy audit can also highlight
With hot processes, cool liquid from a
flush system is injected into the process stream, removing heat, which must in turn be reheated to compensate. Some piping plan configurations remove part of the process fluid and cool it in a heat exchanger before reintroducing it to the process stream, again requiring reheating. Evaporation may also be needed where cool liquid has been added to the process, leading to increased energy usage. So, while a mechanical seal may be
deemed insignificant as part of an overall energy saving strategy, the supporting piping plan can be crucial. It stands to reason therefore that companies across all industries which are looking to optimise efficiency and contribute to environmental sustainability would be wise to consider the energy consumption of their piping plans. A simple way of doing this is by conducting a periodic seal energy audit. Businesses proactively committing to
the International Standards Organisation ISO-50001 Standard for Energy Management Systems recognise that the mechanical seal is the ‘canary in the coalmine’ when looking to identify and reverse unnecessary power consumption caused by inefficient seal support systems. The seal energy audit focuses on
inspecting each mechanical seal, recording seal arrangement, support system configuration, process data and seal system parameters such as water flow and temperature. Existing plant data is collected and heat flow calculations performed, making it possible to calculate the amount of energy impact of each individual
/ ELECTRICALENGINEERING
significant potential for water conservation by indicating where seal support systems are causing excessive energy use. Companies have reaped huge reliability
and cost benefits by upgrading to environmentally friendly continuous loop seal support systems following an audit. These water management systems
Tom Grove, AESSEAL
employ an integral vessel to continuously recycle the flush water. This is circulated to and from the mechanical seal by thermosiphon, a method of passive heat exchange which also provides more efficient cooling. Because continuous loop systems are connected directly to the plant water line, which becomes the system’s fluid and pressure source, they protect the seal faces from harmful products, making them, and therefore the pump itself, more reliable. Industries which use high volumes of
flush water, such as pulp and paper, can achieve significant long-term savings. Take the example of a paper mill, where six litres of water per minute can be injected into pumps and systems to flush and cool them before being evaporated off. Investment in a continuous loop water management system could achieve reduced energy usage of over 50,000 mmBTU, leading to savings of over £400,000 and a ROI of 3-4 months, in addition to improved plant reliability and reduced maintenance times. In terms of environmental sustainability
alone, seal energy audits should be central to any responsible company’s maintenance plans. But this should be a particular no-brainer when the long- term reliability improvements and cost savings are also taken into account.
AESSEAL
aesseal.co.uk/en ELECTRICAL ENGINEERING | NOVEMBER 2018 19
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