Steam traps are essential components of any steam system. They are used to discharge condensate, air, or other non-condensable gases from a steam system while preventing the loss of steam.

This Blog covers both the 1/2″ trap (PRIMUS P/N 400694) and the 3/4″ trap (P/N 400510).

PRIMUS’ steam trap supplier, Watson McDaniel, headquartered in Pottstown, Pennsylvania, is an ISO 9001 Registered and ASME Qualified manufacturing company.

Theory of Operation

In a bellows-type thermostatic trap, the thermostatic element (bellows) is partially filled with a volatile liquid and hermetically sealed at the factory. This liquid vaporizes at a temperature slightly below the boiling point of water. When cool, the trap is wide open, permitting air to be rapidly removed from the system and steam to fill the heating space.

The trap remains open for the discharge of air and condensate. As condensate and steam warm the system, the liquid in the element vaporizes and expands, pushing the ball closer to the seat. When the temperature approaches that of steam, internal pressure in the element exceeds the external pressure in the trap body, causing the element to expand further and push the ball tightly into the seat.

Conversely, the accumulation of cool condensate in the trap causes the element fill to liquefy which contracts the element, opening the flow path through the trap and discharging the condensate and air.

TT125 Features

  • Excellent air handling capability
  • In-line repairable
  • Welded stainless steel thermal element
  • Stainless seat
  • High thermal efficiency
  • 0 – 125 psig operating pressure

Maintenance Steps

Trap maintenance should be performed during a periodic PM
when the sterilizer is cooled down, if possible.

Shut off the steam to the sterilizer

If possible, remove the trap from the sterilizer to provide easier maintenance, avoid damage to other piping when removing the cap (cover), and allow for an unblocked inspection of the seat.

Wait until the trap can be comfortably touched by hand before removing the cap. This will prevent over-expansion damage to the bellows. The thermostatic bellows is the only moving part of the trap.

At room temperature, the bellows should be contracted away from the seat. If
defective, the bellows usually remains slightly expanded at room
temperature and does not move when placed in boiling water.

Remove the cap. Ensure the spring does not fall out of the cap and set the two pieces aside for reinstallation

Remove the thermal element assembly and inspect the seating area of the valve and seat. If the seat area is worn, install a new trap repair kit (PRIMUS P/N 400695 (1/2″) or P/N 400509 (3/4″)). The repair kit includes a thermal element, seat, gasket and a spring. If the seat area is only dirty and not worn, clean the area with a fine (100 grain) emery cloth.

When replacing the trap seat, make sure the gasket is in place and the seat is
torqued down tightly.

Reinstall the thermal element, spring, and cap.

Once steam is turned on to the sterilizer, check for and fix any leaks.

Clean the work area of any remaining debris and dirt.

Steam Trap 3D Drawing and Component Materials

Body – Forged Brass, CA 377
Element – Welded Stainless Steel, AISI 302
Cap (Cover) – Forged Brass, CA 377
Spring – Stainless Steel, AISI 304
Seat – Stainless Steel, AISI 303
Gasket – Brass, ASTM B-21
Union Nipple – Brass, ASTM B-16
Union Nut – Brass, ASTM B-16

Have a question or having difficulties? Talk to Dave Schall, our PRIMUS sterilizer expert who is here to assist you anytime at 877.679.7800 extension 1212 or email at dschall@spire-is.com.

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