Sealing and Impregnation Services

Sealing and impregnation services use uses vacuum, pressure, vacuum and pressure (VPI), and/or wicking-action techniques to drive resins or coating materials into parts and seal pores. There are many different types of impregnation and sealing services. Dry vacuum pressure (DVP) services and vacuum-only impregnation (VOI) services use a vacuum pressure chamber to coat the tiny pores on a part’s surface. Vacuum pressure impregnation (VPI) services also uses a vacuum pressure chamber, but force liquid penetrants into pores with pressure cycles up to 100 psi. Internal impregnation services place an impregnant inside a metal casting and apply hydraulic pressure, forcing the liquid through the leak paths in the casting wall. Wet vacuum (VW) impregnation services submerge parts in a liquid-penetrant bath and evacuate the air above the bath. Part surfaces are rinsed with water before heat is used to cure the material in the pores. With trickle impregnation services, surface-tension effects allow resins to be wicked or soaked up by the internal porosity of a part (like a sponge soaking up water). Other types of sealing and impregnation services are also available.

Most sealing and impregnation services use equipment that consists of a vacuum/pressure or vacuum-only chamber, vacuum pump assembly, impregnant reservoir, reservoir cooling assembly, agitator, transfer piping, and operator interface. Some impregnation systems include a false bottom, load plate, liner, or rotor shaft extension. Others provide a strainer or filter for the transfer line, a chart recorder, and a capacitance meter. Most sealing and impregnation services use integral software and/or data storage devices. In terms of performance, powdered metal impregnation services and metal casting impregnation services may offer specifications such as cubic feet of parts per hour. In general, wet vacuum (WV) impregnation services provide higher outputs than dry vacuum pressure (DVP) services. VPI services may carry additional specifications.
 
There are many different applications and approvals for sealing and impregnation services. Many DVP services, VOI services, and VPI services can seal electronic components against corrosion, or protect automotive parts such as power steering pumps against the ingress of gases or liquids. To meet U.S. military specifications (MIL-SPEC), sealing and impregnation services should be able to handle low-viscosity liquids that do not contain inert solvents or filterable solid materials in suspension. These impregnant properties enable capillary action to penetrate the tiniest openings and deepest cavities.

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