Condensate Drain Traps

Liquid float drain traps

Automatic float style condensate traps provide a reliable method of automatically draining liquid from a pipe system without loss of any process gas. Float drain traps are typically installed at low points in the plumbing system where liquid accumulates from storage tanks, gas/liquid separators and at the bottom of vertical piping.

How Float Drain Traps Work

Liquid flows into the drain trap from above and fills the trap until the hollow stainless steel ball floats sufficiently high enough to open the valve attached to it. The system pressure acts upon the liquid and it passes through the valve to drain until the level within the trap drops sufficiently, causing the float to drop low enough to seal the drain orifice closed. A detailed article illustrating this style of drain trap, installation guidelines, maintenance and troubleshooting can be viewed online: “Float drain traps, how they work, applications and maintenance” (PDF).

Inside of a typical float style drain trap

Lower half of model 90/95-AC trap with float attached

Float extended to reveal valve orifice

Close-up view of valve plunger and seat

At all times there is a barrier of liquid within the trap, thus only the liquid drains from the trap and the steam, compressed air or other inert gas stays within the piping system. The lower plug is used for occasional blow down if particulate such as pipe scale are introduced into the trap. Installing a Y strainer to protect the trap from excessive scale found in older systems is a good idea. All of the serviceable components are attached to the drain trap cover for easy inspection and maintenance.

When installed in locations susceptible to freezing, we offer models that have an extra port in which a 50 watt heater can be installed; this keeps the trap reservoir from freezing.

Air Vent Trap

Some of our float drain traps can be used as a vent trap. Whereas float drain traps are used in low sections of piping to drain-out accumulated liquid, you can invert some drain traps and install within high sections of piping to eliminate accumulated air/steam/gas. The process is simply reverse; gravity ensures the discharge valve is open when not filled with liquid, thus allowing trapped gas to vent. Once liquid sufficiently floats the ball, the valve orifice is closed. These are commonly installed on high capacity water pump systems to assist with venting air entrapped within the pump head and piping during start-up priming.

Capacity Chart

The following chart provides the estimated flow rates for a given orifice size at various pressures. It is accepted practice to incorporate a 3:1 safety factor when selecting your drain orifice size; thus if your expected liquid load is 50 lbs/hr, use an orifice which can handle up to 150 lbs/hr. If your expected liquid load is greater than the flow rates below, or if your differential pressures are higher, contact us for information on additional designs.

You can calculate the approximate flow rate for other pressures using the formula provided where:

Q₁ and P₁ are the known flow rate and pressure
Q₂ is the resulting flow rate for the desired pressure P₂

Documentation

• Outline Drawing: Cast Iron model 90-AC
  • (Note: side inlet version was discontinued — see alternate Type S trap for a side inlet version equivalent to the 90-AC)
• Outline Drawing: Cast Steel model 95-AC
• Outline Drawing: Cast 316SS model 95-AC
• Installation, operation and maintenance manual for type 90 & 95 float drain traps
• Type 90-AC float drain trap parts list