Armstrong SH-900 Series superheat steam traps operate by the effect that rising temperature has on the thermostatic bimetallic elements. At start-up, the valve is wide open, which allows a large volume of non-condensables and cold condensate to be removed from the system. When the system reaches steam temperature, the elements become sufficiently hot to pull on the trap’s valve stem, closing the valve. The valve remains closed until the bimetallic elements cool, thus allowing the valve to crack open, vent the condensate and non-condensables, and then close again when steam temperature is reached.

The SH-900 Series adjusts automatically to changing conditions. Hot elements in the valve generate forces to offset rises in pressure, ensuring reliable operation in superheat applications.

Features and Specifications

The SH-900 is a bimetallic style steam trap in stainless steel with an integral stainless steel strainer. It is inline repairable and capable of operation on low-load applications throughout its pressure/temperature range.

• Maximum allowable pressure (vessel design): 62 bar @ 482°C
• Maximum operating pressure: 62 bar
• Maximum back pressure: 99% of inlet pressure
• Suggested minimum operating pressure: 14 bar

The series is available in two main versions based on operating pressure:

• SH-900L: Low pressure from 14 - 44 barg
• SH-900H: High pressure from 41 - 62 barg

Materials

Component	Material
Body and Cap	ASTM A351 Gr. CF8M Stainless Steel
Valve and Seat	Titanium
Bimetallic Elements	Nickel-chrome and stainless steel
Strainer	Stainless Steel Screen

Dimensions and Weights

Model	SH-900
Pipe Connections (mm)	15 – 20 – 25
“B” Height (mm)	115
“C” Face-to-Face (screwed & SW) (mm)	158
“CC” Face-to-Face (flanged PN63) (mm)	233 – 240 – 278
“D” Φ to Top (mm)	95
“E” Width (mm)	95
Weight (screwed & SW) (kg)	4.4

Note: Standard flanges are in carbon steel, stainless steel flanges are optional. Other flange sizes, ratings, and face-to-face dimensions are available on request.

Capacity and Performance

Installation Guidelines

Proper installation is critical for the performance and maintenance of the steam trap.

Installation Recommendations

1. Ensure lines are clean before installing the trap. Blow down all strainers ahead of the trap.
2. Install the trap below the drain point and close to the vertical drip leg for easy inspection and repair.
3. The trap should be installed in a horizontal line with the cap facing upward.
4. Isolation valves should be installed upstream and downstream of the trap. Open isolation valves slowly when starting up a new trap.

In superheat, high pressure, or low load conditions, there is typically very little condensate generated. Therefore, proper piping and a correctly sized drip leg are essential for the proper operation of the bimetallic trap.

Maintenance and Repair

High-pressure condensate traps should be checked at least three times a year. The trap is inline repairable.

Safety Precaution

Superheated steam is invisible. Do not place any object directly in the trap discharge. Even though no steam is visible, a loud noise will be heard under straight-through conditions. Ensure the trap is isolated, depressurized, and cold before handling.

Replacement of Bimetallic Elements and Screen:

1. Isolate the trap and relieve internal pressure.
2. Unscrew the 4 bolts and lift the cap.
3. Unscrew and replace the bimetallic elements using a 25 mm (1") open-end wrench.
4. Critical Adjustment: The distance between the flat bimetallic elements and the seat should be 1.8 mm for SH-900L and 1.52 mm for SH-900H.
5. Clean or replace the screen.
6. Replace the gasket on the body seating surface.
7. Reinstall the bimetallic element to the bottom hex. Torque to 136-170 Nm (100-125 ft-lb).
8. Put the cap back on the body and tighten the 4 flange bolts in a crisscross pattern. Torque for SH-900 flange bolts is 122 Nm (90 ft-lb).

Troubleshooting

• Cold Trap (No Discharge): Check for plugged strainers, broken valves in the line, plugged piping, or closed isolation valves.
• Steam Loss: If the trap leaks or blows live steam, it may be due to the valve failing to seat, dirt in the orifice, or worn parts. Note: Do not confuse flash steam with live steam loss. High-temperature condensate will flash to steam when released to a lower pressure.
• Continuous Discharge: Under heavy loads, continuous discharge is normal. If the trap is not up to temperature, allow more time for start-up loads to clear.