Each dynamic seal in a hydraulic cylinder serves specific purposes:
Piston seals act as pressure barriers, preventing fluid passage past the piston to control cylinder motion, maintain position, and support loads. Rod seals also serve as pressure barriers, containing operating fluid within the cylinder, regulating the fluid film along the piston rod surface to prevent corrosion and lubricating the rod and wiper seal, and reaccepting the lubrication film upon rod retraction. Buffer seals shield the rod seal from fluid pressure peaks exceeding system pressure, dampen pressure fluctuations to enhance rod seal performance, and internally exclude contaminants to safeguard the seal. Wiper seals prevent external contaminants from infiltrating the cylinder assembly and hydraulic system, while also reaccepting the lubrication film upon rod retraction.
In contrast, static seals secure components together without relative motion. Hydraulic cylinders employ static seals in various locations, notably between the piston and piston rod, and between the head and cylinder bore tube.
Criteria for Seal Selection The choice of Car Lift Repair Orlando hydraulic seal material and profile primarily hinges on application parameters. Considerations include:
Fluid pressure range, encompassing frequency and pressure peak severity. Temperature range of the fluid and cylinder assembly during operation and rest. Reciprocating piston rod speed. Fluid media properties, including type and viscosity. Hardware dimensions such as rod and bore diameters, seal groove dimensions, gaps, overall cylinder length and stroke, and surface finish specifications. Cylinder application specifics, including equipment type, operational conditions, installation, duty cycles, and environmental factors like temperature variations and contaminants.
Thermoplastic elastomers, exemplified by polyurethanes, offer exceptional durability against wear and pressure while retaining elasticity and flexibility.
Rubbers, like nitrile rubber (NBR), serve as prevalent dynamic seals in the fluid power sector. Their applicability spans a broad temperature spectrum and resistance to various Car Lift Repair Orlando hydraulic fluids depends on their chemical makeup.
Polytetrafluoroethylene (PTFE) stands out among plastics for its distinct composition and properties, boasting unparalleled chemical resistance and the lowest coefficient of friction. This attribute translates to superior startup behavior, minimized stick slip phenomena, and precise positioning of hydraulic cylinders. Often, PTFE is enhanced with organic and/or inorganic fillers to augment specific properties like wear or extrusion resistance.
Rigid thermoplastics and thermosets, including their composites, feature significantly greater hardness and stiffness, sacrificing elasticity compared to polyurethanes, rubbers, and PTFE. Consequently, they find suitability in applications prioritizing mechanical strength over flexibility, such as specialized piston seal arrangements for heavy duty use.
Moreover, Car Lift Repair Orlando advancements in materials have broadened the range of sealing technologies. For instance, bonding urethane to PTFE and other rigid plastics has showcased improved performance under high pressures, temperatures, and speeds. Similarly, bonding thermoset materials to PTFE and other plastics can enhance sealing efficacy and extend the seal’s operational lifespan.
Fluid compatibility stands as a crucial criterion. Car Lift Repair Orlando Hydraulic systems employ fluids with diverse chemical formulations and viscosity grades tailored to specific applications. While mineral oil based fluids with additives are common, alternative fluids, like biodegradable ones, are gaining traction. However, these alternatives may pose challenges, as they are more prone to entrained water, and conventional sealgrade urethanes may succumb to hydrolysis under elevated temperatures, water exposure, or high humidity. Addressing this, hydrolysis resistant urethanes have been developed to enhance performance and longevity.
Given the variability in fluid formulations, additives, and contaminant levels, meticulous attention must be paid to ensure compatibility between the fluid and all seal materials, factoring in temperature and mechanical loads. Testing seals in the actual fluid under operational conditions remains a best practice.
As Car Lift Repair Orlando technology advances and applications demand higher operating pressures, broader temperature ranges, harsher system fluids, and longer service lives, sealing technologies for fluid power applications will evolve accordingly. Innovative hydraulic seal solutions will emerge to meet these evolving demands.
A common argument against Car Lift Repair Orlando hydraulic systems revolves around the concern of leakage, a dreaded issue indeed. However, with effective sealing, leakage ceases to be a concern for your system. Sealing plays a pivotal role in ensuring the smooth operation of hydraulic applications. Leakage from the cylinder or around the piston, coupled with the infiltration of undesirable contaminants, not only diminishes the longevity of components but also undermines the efficiency of the entire application.
Choice of materials plays a crucial role and is dictated by the specific environment in which the seal operates. Different chemicals react diversely to various fluids, and certain materials have distinct limits concerning pressure and temperature. Additionally, they must withstand extrusion, making material selection highly tailored to the application at hand.
Polyurethane, an organic material characterized by numerous urethane groups in its chemical structure, belongs to the thermoplastic elastomers (TPE) family. It bridges the gap between thermoplastic and elastomeric materials in terms of hardness, deformation behavior, and consistency. Within defined temperature parameters, polyurethane exhibits rubberlike elastic properties alongside the benefits of a rigid plastic.
The composition of polyurethane comprises three primary components: polyol, diisocyanate, and a chain extender. The type and proportion of these constituents, along with reaction conditions, determine the resulting material’s properties. Generally, polyurethanes offer:
High mechanical tensile strength
Excellent abrasion resistance
Variable modulus of elasticity
Wide range of hardness options while maintaining elasticity
Good resistance to ozone and oxygen
Exceptional resistance to abrasion and tearing
Polyurethanes are usable within a temperature range of 30 to 80°C, with high performance variants (compounds) capable of withstanding temperatures up to 110°C in mineral oils over prolonged exposure periods.
AcrylonitrileButadieneRubber (NBR)
NBR is a polymer derived from butadiene and acrylonitrile.
NBR with a low ACN content exhibits excellent cold flexibility (down to approximately –45°C) and moderate resistance to oil and fuel. Conversely, a material with a high ACN content, offering optimal resistance to oil and fuels, may have reduced cold temperature flexibility, reaching only down to –3°C. As ACN content increases, elasticity and gas permeability decrease, while compression set worsens.
Car Lift Repair Orlando NBR offers:
Good resistance to swelling in aliphatic hydrocarbons, greases, and fire retardant hydraulic fluids of Groups HFA, HFB, and HFC
High resistance to hot water at temperatures up to 100°C (e.g., in sanitary fittings), as well as inorganic acids and bases at concentrations and temperatures within certain limits