FTL tailor approach to Industrial Water Challenge
Overcoming sewage challenges through custom sealing.
FTL Technology has worked closely with process equipment operators across a wide range of industries and applications, identifying areas where problems might occur, and advising solutions centred on better sealing. One such example of the impact of FTL Technology’s custom-engineered approach to sealing came with work undertaken on a primary settlement tank hydraulic ram pump.
This case study is based on recent work conducted for Severn Trent Water. As a result of this custom-engineered solution, the primary settlement tank at the facility benefitted from increased flow, making significant operational cost savings possible.
Primary settlement tanks, also known as sedimentation tanks, are designed to allow organic solids (sludge) to settle by reducing the flow speed of wastewater. A series of floor scrapers, boards and water jets help to remove the raw sludge and surface scum, but for the raw sludge which settles, most primary settlement tanks employ hydraulic ram pumps to continue the sludge treatment process.
Hydraulic ram pumps, or hydrams, are supplied with power from the force of moving water. A first valve permits water to reach maximum speed along a pipe, before closing and using the inertia of the water flow to open a second valve in the pump setup. This high pressure water flows through the second valve to the delivery pipe, which in turn reduces the water pressure on the first valve in the pump. This first valve reopens, and the cycle begins again.
With just a couple of moving parts and a relatively uncomplicated design, hydraulic ram pumps are not known as a particularly high maintenance piece of equipment when controlling fluid flow. Even so, the most straightforward of assemblies can develop sizeable problems which have the potential to impact the operation as a whole.
When hydraulic ram pumps suffer problems in terms of insufficient water delivery, there are a number of causes which need to be looked at; the waste valve may be improperly adjusted, or alternatively the pressure vessel may not have enough air. In rarer cases, a failure may simply be explained by the ram pump attempting to raise water to a level higher than it is capable.
In the case of this Severn Trent Water facility, engineers from FTL Technology diagnosed a significant sealing failure in the packing that was fitted on the hydraulic ram pumps. The problems were being reported in the winter months, with more severe problems experienced when the weather was coldest. On closer inspection by the FTL Technology team, the problem was isolated to a particular installation of rubber vee packing (chevron rings), which had been incorporated into the ram pump.
The rubber vee pack being used in this application had been impregnated with a particular lubricant comprising a number of additives, but mostly water. While this packing grade would perform to a good standard at most temperatures, at particular sub-zero temperatures the lubricant used in the packing would invariably freeze. This frozen lubricant in the ram pumps would result in near-instant seal failure, and therefore, a severe drop in the effectiveness of the pump. In order to restore the ram pump to a reliable working condition, an alternative packing solution to the flawed rubber vee packing would need to be identified.
One of the key challenges of this task was to identify the root cause, design a solution and fit this solution without having too significant an impact on the operational downtime of the pump. Sewage treatment is not a process which can be ‘switched off’ while work is carried out, leaving the need for diagnostics and other required works to be completed quickly.
One of the key strengths of FTL Technology is in the personal way in which their engineers go about finding an effective sealing solution. FTL Technology assembled a team of application and material engineers to carry out a detailed investigation of the ram pump problem, taking the necessary time to gain the clearest possible understanding of how and when the sealing problem manifested in this particular primary settlement tank application.
Taking a custom-engineered approach from the very first steps, FTL Technology is not restricted to off-the-shelf products when recommending solutions. In the case of this Severn Trent Water application, the engineers were able to develop a spring-loaded dry running packing solution for the hydraulic ram pump setup.
Spring-loaded compression packing is one of the most flexible products in use for fluid sealing, comprising individual scarf cut or spiral wound ring designs, either machined or moulded adapters and an engineered spring. Selecting the right braid for the application is critical, and with braid options ranging from flax through to pure graphite, there is a braid option to optimise a pump for any operating environment.
By installing a new packing system to the ram pump application which removed the need for lubrication, the potential for the application to freeze in low temperatures was eliminated, increasing the reliability of the ram pump substantially.
There were two clear benefits following the fitting of the new spring-loaded dry packing solution to the hydraulic ram pump application.
Primarily, the problem which was originally reported – the sealing failure in cold conditions – was rectified with the removal of the old lubricated rubber vee pack setup. Severn Trent Water confirmed no losses in productivity or operational efficiency as a result of the new dry packing, and moreover, there was an added cost-saving benefit associated with no longer requiring the purchase of lubricant for their pump assemblies.
The secondary benefit of this solution was that the hydraulic ram pump experienced a constant load on the suction stroke, resulting in an increased flow equating to one extra litre per second – or 86,400 litres over the course of a day.
In the time since the installation of the solution for Severn Trent Water’s original problem, the company has adopted dry running packing methods as best practice for their hydraulic ram pump applications. Furthermore, the company has suffered no recurrences of the pump freezing issue, delivering a permanent boost to the efficiency and reliability of the facility’s wastewater process capacity.
FTL Technology has applied packing, gasket and elastomer sealing expertise to pump and valve problems in industries beyond sewage and wastewater processing. Their sealing specialists have adapted pump and valve packing solutions for the specific needs of operators across oil, gas, food and pharmaceutical processing, as well as a broad range of other heavy industrial applications. Through clear identification of the correct packing setup for any given temperature, pressure or media, FTL Technology has demonstrated the ability to optimise the performance of virtually any pump or valve.