Crosshead Sealing on Triplex Plunger Pumps
The client for this project was a UK manufacturer of high pressure plunger pumps for use in water jetting and various process pumping applications.
The customer reported the consistent underperformance of a wide range of proprietary sealing components, resulting in oil leakage when used on fast moving reciprocating shafts with zero pressure.
Failure reports indicated that only 50% of seal trials passed in-house testing procedures, and when in field, seals were not reaching the industry standard of 500 operational hours due to leakage and excessive wear. This caused visible oil leakage from the crankcase, with the potential to cause significant environmental damage as well as other hazardous effects.
Other issues included material compatibility and water from the fluid end was also passing the seal and mixing with oil in the crankcase.
FTL Technology collaborated closely with the customer's engineering department, to develop a bespoke high wear resisting seal which not only kept oil in the crankcase end, but also allowed for a hydrodynamic film of oil to enable constant lubrication of the seal at the high operational speeds of this application.
Where speeds exceed capabilities of elastomeric seals, or where oil types present compatibility issues, a specifically modified PTFE crosshead seal has also been developed by FTL Technology and successfully tested.
This engineered solution also significantly reduced the migration of media (namely water) from the fluid end into the oil-filled crankcase.
The key outcome from the custom FTL Technology solution was a crosshead seal system that surpassed the required 500 hours of reliable service in the field.
The crosshead sealing solution provided the optimum pressure drop between oil case and atmosphere to facilitate appropriate levels of lubrication when using an all-elastomer seal at elevated running speeds.
The custom design also prevented any further ingress of water from the fluid end mixing with crankcase oil.
Altogether, the design of the new sealing system delivered greater performance reliability at the same time as ensuring a cleaner and more environmentally friendly pumping assembly.