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Extending Packing Longevity for Road Marking Equipment
Road marking equipment undergoes constant pressure from multiple angles, leading to challenges for those tasked with its maintenance and care. A common issue is the lifespan of packing. Premature degradation occurs due to a combination of reasons:
- The corrosive nature of paint
- The pressures applied during use and application
- Extremes of temperature during deployment
- Over or under greasing
The following case study discusses a typical challenge and the products utilised to overcome the issues successfully.
A prolific manufacturer of road marking equipment experienced a dramatically shortened lifespan of the packing used on their machines. The currently used Kevlar with PTFE lubrication had a mean time between failure (MTBF) of a single day.
On examination, the key issues leading to this unacceptably short packing life were multiple.
- The medium used was particularly aggressive, being a liquid thermoplastic containing glass pearls, silica and titanium oxide.
- The temperature of the medium varied from 10 to 220 oC, with a screw run only at temperatures over 150oC
- Inadequate lubrication during use
To adequately address the problem required a multi-pronged approach. The first was to deal with the quality of the packing.
- The packing: The customer had chosen to use low-friction PTFE packaging over high friction Aramid packing. While this successfully lowered the risk of damage to the machinery’s shafts, the construction means that under pressure, they are prone to consolidate and extrude. When this happens, the medium then leaks. In this case scenario, the pressures and friction were so great that the packing could not withstand more than a single day of use.
We substituted the packing with the unique Chesterton DualPac® 2211, a patented solution that combines two complementary materials in a single packing. This unique product, applied with Solution 2 + 3 rings of DualPac® Packing Technology in combination with a lantern ring, provides the toughness of aramid with ePTFE’s kindness, resulting in a robust packing resistant to the rigours of severe applications, yet without shaft wear.
We then began the task of maintaining adequate lubrication in light of the varied and often elevated usage temperatures.
- Lubrication during use: Adequate lubrication of machinery is an age-old issue. This becomes even more relevant when there are extremes of temperature, such as with this particular equipment. Ensuring the correct timings and amount of lubrication is vital to the packaging’s lifespan and wear and tear on the equipment.
To ensure this took place, we added the Chesterton Lubri-Cup to the mix – a tool that automatically dispenses grease exactly when needed. This effectively removes the issue of over or under-lubrication, creating a precise science rather than the hit-and-miss approach so often used.
Due to the high temperatures involved, we combined the LubriCup with Chesterton 615 Grease, designed to withstand pressure capabilities, extremes of temperature, water-washout and corrosion. This was necessary as although, in theory, the screw cannot supply pressure, in practice, this is not the case, and quite high discharge pressures (approx. 20-30 bar) are applied.
Replacing the packing with Chesterton DualPac® 2211 and the combination of LubriCup and Chesterton High-Temperature Grease meant that the machinery could be operated with fewer gland adjustments and benefited from a dramatically extended lifespan: MTBF was increased from a single day to at least six months.
Chesterton specialises in the provision of innovative, effective solutions to address every aspect of rotating machinery use. Discover more at www.chestertonrotating.chesterton.com
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