With the UK water and wastewater industry under continual pressure to contain maintenance and running costs, one of the easiest routes plant and operational managers often look to make savings is the readily identifiable area of replacement parts and spares.
Many companies in the industry use high flow, high pressure peristaltic pumps at some point in their treatment processes – as a result, there is no shortage of replacement hoses from manufacturers out to make a fast buck by exploiting the financial pressures they operate under. However, while it’s easy to understand why the low-cost offers – as much as 50% less are so attractive, the plain fact is that opting for non-standard replacement hoses for pumps is simply a false economy.
Failure to take into account the considerable additional expense incurred by less robust alternatives necessitating more frequent replacements – not to mention significant knock-on costs caused by loss of performance and associated failures at other points in the system, causing downtime – is costing the industry dearly. Once these additional side effects are taken into account, they often amplify the increased frequency of hose replacement costs by a factor of four or more. All this can far outweigh and negate the original savings made by low-cost purchases.
In the light of hard facts and figures, it’s difficult to understand how using non-standard parts can ever be viewed as a good business decision. Yet it causes ongoing problems in the industry – particularly in the context of negative impacts on pump performance and system failures, which almost inevitably necessitate additional costs. The lower efficiency levels, higher power requirements, greater wear, increased maintenance and greater risks of part/equipment failure, which invariably accompany cheaper, alternative offerings are overlooked in the face of significant savings.
Looking at just a few examples from the Watson-Marlow Bredel catalogue of ‘pirate hose horror stories’ gives some indication of the scale of the problems. At one installation where the operator had opted for the cheaper alternative, pumps were required to run faster and for longer periods, with a serious adverse effect on running costs and the overall efficiency of the sludge handling system. At a multi-pump site, where undetected bearing failure resulted in shafts falling into pump housings, the cost of replacement rotors, pressing shoes, shafts, bearings, front covers and bearing seals was between £3,000 and £4,000 per pump. Spread across several pumps, this dwarfed any theoretical savings achieved by using pirate hoses.
On another site using Watson-Marlow Bredel SPX100 (100mm bore) pumps, the result of using inferior hoses was two cracked pump housings, with replacement costs (excluding labour) amounting to £5,500. In particular, bearing failures due to uneven loading and/or overloading, and stemming directly from variations in hose wall thickness, can have serious consequences in terms of operating costs and downtime, especially on unmanned multi-pump installations, where failure may be undetected or detected too late to prevent serious damage.
So what are the defects that potential purchasers of pirate replacements need to consider before opting for the cheaper alternative?
1. Hose design As the only component in contact with the pumped media, the hose (or tube in the lower pressure designs) is the heart of any peristaltic pump. Dedicated hoses such as those produced by Watson-Marlow Bredel are essentially the end product of continuous research and development, allied to 50 years experience and based on many thousands of installations worldwide. Watson-Marlow Bredel hoses consist of a thick, resilient inner layer and an outer layer of natural rubber, reinforced internally with braided nylon. They are produced to close dimensional tolerances (between 0.25mm on larger hose bore sizes and 0.4mm on smaller hose bore sizes) and ground to the precise diameter. Wall thickness is the key factor in the hose construction – a hose could be 2mm larger on the diameter, but if the wall thickness is still the same, the unsuspecting purchaser would not notice problems. Recent measurements of a cheaper “pirate” hose found the bore to wall ratio to be out of concentricity by 1.5mm each side – for instance, on a compressed hose up to 3mm difference. The resulting changes in compression forces lead to premature bearing failure and even broken pump castings. On a SPX100 hose pump for example, the approximate 8,000N of load from this degree of over-occlusion would reduce bearing life by over 50%.
2. Hose life Figures for hose life are equally in favour of dedicated manufacturer’s hoses, notably on sewage sludge pumping and similar arduous waste handling applications. One example of this is at a site where two identical pumps are installed for the same duty, A maintenance contractor replaced the original Bredel hose with a cheaper ” pirate ” alternative on one of the pumps. Twelve months later, the original Watson-Marlow Bredel hose is still in service. The second pump, using the pirate is on its fourth hose fitting. In another comparable sludge pumping installation, “pirate” hoses last approximately 200 hours, equivalent to about one month’s service – a retrofitted Bredel hose is still in service after more than eight months.
3. Slow hose change Hoses that appear identical on visual inspection will not necessarily be comparable in performance. This is reflected both in hose life and the speed with which a hose change can be carried out. In one case, a maintenance contractor who customarily fits cheaper non-standard hoses, normally took a whole working day to carry out a hose change on a Bredel SPX80 peristaltic pump. In comparison, Watson-Marlow Bredel’s own engineers took under one hour to fit a dedicated 80mm Bredel hose. There have been instances of dimensionally inaccurate hoses becoming stuck half in and half out of the pump housing, eventually having to be cut into pieces before extraction was possible.
It is also important to take into account lack of provenance, non-compliance with standards, the reputation of often little known manufacturers and products with no real validation that the parts being purchased will perform at anything like the required levels – and no comeback if they fail to perform. Add in the complications of compromising original manufacturers warranties, with insurance implications where ‘pirate’ parts are used, and the seemingly significant savings on offer very quickly start to unravel.
The real answer is, of course, that only highly engineered, high performance, precisely fitting parts will provide the accurate flow rates, long-life and 24/7 reliability that water and wastewater treatment providers need. This is key to achieving low whole life costs and the very real problems that stem from using non-original spares are simply not worth the risk.
