Mechanical Seals and Gasket Supply is our Specialty. American Seal and Packing is a leading manufacturer & distributor of mechanical seals, Grafoil, gasket material, cut gaskets and quality o-rings providing innovative solutions to mechanical seal problems. We're finding better ways to serve our customers all the time. In addition to our expanding line of industrial mechanical seals, we're updating and upgrading this web site to provide you more information about our company and our products.

By current terminology (API 682), a fluid between the two seals in a dual seal at higher pressure than process pressure is a barrier fluid. (A dual seal pressurized this way was formerly called a double seal.)  A barrier fluid completely isolates the pumped process fluid from the environment.  A buffer fluid is instead at lower pressure than pump process pressure. (Dual seals with buffer fluids were previously called tandem seals.)  The AST 80 is double-balanced, so it can be pressurized either way.  Neither barrier nor buffer fluids should be confused with a flush, which is injected directly into the pumpage through the seal gland or the pump's seal chamber.

A barrier or buffer fluid should be
--compatible with the process,
--compatible with the seal materials,
--a good lubricant and heat transfer medium for the seal faces,
--benign to the environment and the workers in the plant.

Some good choices for barrier and buffer fluids:

Water/Ethylene Glycol mixture: Almost as good as water for heat transfer; doesn't freeze in outdoor applications. 50/50 mix by volume is easiest to mix, and gives good freeze protection. Use corrosion-inhibited industrial grade.

Water: Cheap, safe, available, excellent heat transfer characteristics (high specific heat, low viscosity, high thermal conductivity). Don’t use in freezing conditions.

Water/Propylene Glycol mixture: Like water/ethylene glycol, but usable in food applications.

Kerosene or Diesel fuel: Good where an oil is required. Low enough viscosity to flow well and transfer heat, and a good lubricant. Vapor pressure low enough that emissions aren't a problem.

Light mineral and synthetic oils: Generally good. Within synthetics, polyalphaolefin (PAO) based fluids usually better than ester-based. Synthetic oils specifically formulated for use as mechanical seal barrier fluids are available, including grades accepted by FDA and USDA.

Some common, but bad, choices:

Automotive antifreeze: Based on ethylene glycol, but contains additives to prevent corrosion of automotive engine components and to stop small radiator leaks. These additives cause excessive seal face wear.

Uninhibited ethylene glycol: Without corrosion inhibitors, can attack seal parts, notably the nickel binder in tungsten carbide.

Automatic transmission fluid (ATF): Contains additives to increase friction in the bands and clutches in automatic transmissions. These also increase wear and friction in seal faces.

Silicone oils: Inert, but often form glassy particles that abrade and clog seals.

Our Select Manufacturers

  • Sepco
  • FMI-Spa
  • Flow Serve
  • AST

Our Select Manufacturers

  • Utex Industries
  • Graftech
  • Lamons
  • Vulcan


  • Call us at: 714-361-1435
  • Fax: 714-593-9701