Seal Engineering Advice on Pressure, Load, and Media

Seals have an incredible impact on equipment performance. When used correctly, they extend cylinder life, prevent leaks, improve actuator positioning accuracy, minimize friction, and prolong energy.

There are several factors that engineers should consider after seal creation to ensure productive performance. Although selecting and testing seals may seem daunting, reasonable experience helps engineers avoid common mistakes and replicate proven successes. Depending on the utilization, some are more suitable than others. Here is some advice on a just a few of the many factors engineers should consider when aiming for the best seal performance.

Seals require pressure to operate. Pressure can contort a seal and change the fluid film on what the seal runs. Engineers must consider these effects. Accelerated rising pressure can introduce possible blow-by (this occurs when fluid bypasses the seal.) Considering that a change in pressure could affect the fluid film is important as well as the film getting thinner at higher pressures. One must account for possible pressure spikes from valves, plumbing, and other sources as well as pressure in relation to the dynamic profile. Pressure statuses can powerfully alter among diverse motion sequences.

You should never underestimate pressure creating hardware ballooning or internal deformations. Mating hardware alterations can severely affect seal performance. Do not mistakenly assume the effect pressure can have on internal contamination. High pressures give contaminants more energetic force and accelerated wear/debris generation. Testing should be concentrated on pressure spikes, or high system pressure. Since pressure energizes seals, a sealing system may not energize properly at low pressure. Never assume that test pressure is exactly the same as application pressure.

The sealing system must consume loads and/or forces to properly guide the piston or rod. It is important to incorporate bearings or wear rings to handle the majority of the load and limit rod or piston deflection. Understand that for localized tests duplicating only a section of a machine, engineers may need to transform load to displacement. Isolated tests cannot affect the particular load applied to the wear ring due to the size difference between test rig and actual application. Scarf cuts on wear ring work better on the unloaded side of the bearing to ensure maximum material coverage and following load distribution by the wear ring. Never oversee impact since it can exert extremely high loads on wear surfaces and may be beyond the limits of some materials.

Media is both retained fluid and external contamination that the seal excludes. It is important to understand that fluid conflicts often lead to chemical attack on sealing units. This increases friction and excels wear. There are many potential sources of contamination. Examples include water ingression increasing hydrolysis (which greatly affects certain seal materials), excessive air intrusion (significantly could negatively affect performance.) Fluid cleanliness is incredibly important. Contamination increases wear, abrasion, and impact damage to seals and also affects the fluid film under the seal. Do not ignore the effect of energy density or size. Contaminants have more momentum and do more damage as energy density increases in some circuits. Fluid replenishment or replacement could also affect fluid properties. Tests are run using fluids different from those in the actual application often result in erroneous conclusions.

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About Colonial Seal Company

Founded in 1994, Colonial Seal Company is a registered Vietnam-Era, Veteran-Owned, ISO 9001:2008 certified company providing cost effective sealing solutions for over 20 years. Our products include customized applications and have been proven to reduce production downtime and keep maintenance costs low on machinery. Our seals have been used in windmills, mining machinery, food & beverage equipment, pharmaceutical applications, and many others!

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