Spirax Sarco MST21 Series Installation And Maintenance Instructions

INSTALLATION AND MAINTENANCE INSTRUCTIONS
IM-2-00021-US
MST21 Series Thermostatic Steam Trap
305 psig @572º F (21 barg @300º C)

Installation

1. Install strainer optional and isolation valve upstream of trap if draining to grade and both sides if
discharging into return system.
2. Never weld pipe connections to the trap, damage to the thermostatic capsule could result.
3. For freeze protection all drain lines must be pitched toward the trap for gravity flow. Trap must be
installed vertically discharging downward and discharge piping must be self-draining.
4. When used as a thermostatic air vent, the arrow pointed upwards. Locate at high point of main or
equipment, where air can collect and pipe discharge to a drain.
5. Always drain to a safe place.
Recommended for critical applications,
such as draining steam mains, tracing
lines, sterilizers and steam air venting.
Make sure trap is mounted in direction
of flow.

Spare Parts

• Complete internal set 3,4,5,6,7.
• Gasket Kit (set of 3) 7.
Note: Must choose either STD, NTS, or
Sub capsule.

Maximum Working Conditions

Maintenance

1. Make sure all steam is turned off and pressure has been
2. Remove cap (2) using a wrench.
3. Lift out the strainer screen (6), Spring (4), thermostat cap-
4. Replace with new internals in the correct order. Make sure
5. Fit a new gasket (7)
6. Refit the cap (2) using a little anti-seize compound on the

Recommended Tightening Torques

Size
1/4"
3/8"
1/2"
3/4"
1"
dissipated before doing any work.
sule (3), and spacer plate (5).
the conical spring (4) is positioned with the narrow end in
contact with the capsule.
threads and tighten to the recommended torque (see table).
Lbf ft
73-80
73-80
73-80
73-80
73-80
1
April 2014
Nm
100-110
100-110
100-110
100-110
100-110