Mechanical seal friction accounts for a tiny percentage of the total power consumption used on any one pump, so it’s easy to see how this key component can be overlooked by managers seeking to target energy losses and improve efficiency.

Yet the energy consumed indirectly through mechanical seal support systems can be considerable. These support systems or ‘piping plans’ supply a clean flush liquid to provide lubrication, prevent overheating and maximise a seal’s reliability. With the exception of gas-injecting seals, most mechanical seals across all industries will come with a piping plan. These 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 to the space between two co-axial mechanical seals to prevent atmospheric contact with the pumped fluid, improve seal cooling, or enhance safety.

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, which all requires reheating. Evaporation may also be required where cool liquid has been added to the process, again leading to increased energy usage.

The smart selection of piping plans is therefore of great relevance across all industries looking to optimise efficiency and reduce costs.

The International Standards Organisation recognises the importance of energy management in the ISO-50001 Standard for Energy Management Systems. Businesses proactively committing to this standard recognise the mechanical seal as the ‘canary in the coalmine’ when looking to identify and reverse unnecessary power consumption caused by inefficient seal support systems. 

A simple and low-cost way to identify this potential energy waste is by carrying out a periodic seal energy audit. This involves inspecting each piece of equipment, 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 energy impact of each individual mechanical seal on the plant, identify where energy use is high and review options for reducing it.

An audit report is then produced, providing the company with potential opportunities for a more efficient piping plan configuration, the investment required to upgrade and the potential returns. This also 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. 

Where flush piping plans are in place, energy conservation goes hand in hand with water conservation for those companies which elect to upgrade to the environmentally friendly ‘continuous loop’ seal support systems developed in recent years. These manage water sustainably by employing an integral vessel to store flushing water for continuous recycling. The barrier fluid is circulated to and from the mechanical seal by thermosiphon, a method of passive heat exchange which circulates the fluid, minimising wastage and providing more efficient cooling.

Because closed 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. 

Their financial impact can be significant. For industries such as pulp and paper – where a typical paper mill can pump 6 litres of water per minute into pumps and systems to flush and cool them before being evaporated off – investment in a continuous loop water management system can 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.

Seal energy audits can also provide an important communications bridge between the plant maintenance reliability personnel, who often make decisions about piping plans in isolation, and operational stakeholders responsible for energy consumption, who might have limited visibility of how seal piping plans impact on wider energy usage.

With the reliability, cost and environmental benefits a seal energy audit can bring, they should be central to the maintenance plans of companies with a focus on minimising operational costs and maintaining their reputation as a sustainability-focused organisation.