With the shortfall in freshwater supplies already reaching crisis level in some parts of the world, and the Environment Agency warning that the UK could run short within 25 years, water conservation is one of the major challenges facing companies across the industrial spectrum. But environmentally sustainable products are available that can help companies become part of the solution, says David Amory, of AESSEAL.
The water crisis is playing out on a global scale. The UK Environment Agency has warned that England is set to run short of this vital resource within 25 years, while at a global level a number of major cities have been at risk of hitting ‘Day Zero’ – when the taps run dry.
While rising domestic water demand has contributed significantly to water stress, and climate change and population growth cannot be ignored as significant factors in the crisis, the fact remains that agriculture and industry withdraw the overwhelming majority of the world’s freshwater.
Tackling water shortage must therefore involve collective and concerted action at every level.
Many organisations have made a commitment to reducing their environmental footprint by embedding sustainability targets in strategies and appointing sustainability personnel to senior positions. However, this is not always backed up by investment in operational changes to tackle excessive water consumption.
In its recent report Treading Water the CDP, the global organisation which drives action by companies and governments to safeguard water resources, presented some starkly contrasting facts: while the number of companies setting targets to reduce water withdrawals doubled between 2015 and 2018, in that same period there was an almost 50% rise in the number of companies reporting higher water withdrawals.
So, what might incentivise senior management to make the leap from ‘good intentions’ to a proactive, effective sustainability programme?
They could consider:
- Eliminating all water waste beyond the absolute minimum required for the efficient functioning of rotating equipment and the process
- Eradicating the leakage that leads to product dilution
- Improve reliability and put an end to unscheduled downtime
- Making significant energy savings
- Achieving swift return on investment and long term operational savings
This can be achieved through a simple upgrade to advanced dual mechanical seals and seal support systems on rotating equipment such as pumps. Retrofitting legacy equipment is not an issue. The only really difficult part is changing your mindset.
Traditional gland packing and single mechanical seals are common root causes of excessive water use in manufacturing. Both often require substantial quantities of clean, cool water to provide lubrication and prevent overheating, yet even in optimal environments they display serious operational flaws. Leakage is a standard feature, causing product loss and contamination. Maintenance is intensive and mean times between failure (MTBF) short. But their greatest drawback is the sheer volume of seal flush water that is often injected from an external source to provide this cooling lubrication, the vast bulk of which goes down the drain or is evaporated off at the end of the cycle.
In a typical application, where water is measured for one minute, around 6 to12 litres (1.6 to 3.17 gallons) of flush water is required. In continuous operation that amounts to roughly 3.2 to 6.3 million litres (0.8 to 1.6 million gallons) per year, for each seal (or pump).
Yet simply replacing gland packing or single mechanical seals with modern double mechanical seals and a water management support system will virtually eliminate leakage, improve pump reliability and reduce the amount of seal flush water required to virtually zero.
With dual mechanical seals, one of the two faces seals towards the process fluid and one to atmosphere, with a barrier space between the two. Like single seals, these require a constant, consistent flow of fluid (often water) to ensure the seal faces operate efficiently and dry-running does not lead to seal failure.
This is where the water management support system comes into play. Using a thermosiphon process, the support system supplies clean, cool water to the barrier space between the double seals at a pressure higher than the product pressure, ensuring a consistent, stable and clean fluid film keeps the seal faces cool and lubricated. This flush water is constantly recycled, flowing across the seal faces in a continuous loop and reducing leakage to the absolute minimum. Roughly one teaspoonful of water a day is lost, in the form of vapour.
Dual mechanical seals can meet the requirements of almost any application and can withstand extreme temperature and pressure fluctuations. There is virtually no industry for which this type of water saving sealing technology is not suitable.
Even companies with a strong commitment to the International Standards Organisation ISO-14001 Standard for environmental management systems and ISO-50001 Standard for energy management systems must keep a close eye on the bottom line.
But by installing the correct dual seal and support system, from an annual operational budget you could subtract:
- The cost of energy to heat, cool or evaporate external flush water
- Equipment costs for the frequent repair or replacement of gland packing, failed bearings (caused by water ingress as a result of seal leakage) and, in worst-case scenarios, pump shafts or sleeves damaged by the friction of gland packing
- Routine and unscheduled maintenance engineer costs – this sealing technology is almost maintenance-free and causes no damage to bearings or pump shafts
- Effluent charges for discarded water
These savings comprehensively refute the practice of continuing to fit the same old sealing technology simply because it was specified by the original equipment manufacturer (OEM). The reality is that some seal suppliers offer cheaper bulk sales to OEMs, but then make up for that loss leader by selling replacement seals to end-users at a much higher price, so any perceived saving is questionable in the long-term.
There are clear operational and financial benefits to upgrading to more environmentally sustainable sealing technology. Less easy to calculate is the enhanced reputation that comes from being able, not just to declare a commitment to water conservation, but to evidence it.