Page 384 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Steam Turbines and Turboexpanders 363

Caution: Do not operate the turbine more than 2 percent above the
rated trip speed listed on the turbine nameplate. If the
overspeed trip does not operate within 2 percent of the
designated speed, shut the turbine down and make trip ad-
justments as described in the section, “Overspeed Trip
System.”
8. Latch the resetting lever and bring the turbine up to speed. Operate
the turbine for approximately one hour. Check the bearing tempera-
tures and turbine speed. Listen for unusual noises, rubbing or vi-
bration. After this period, the turbine can be shut down, doweled to
the mounting surface and coupled to the driven machine. If the
turbine is used with a speed reduction gear or other special equip-
ment, follow all instructions pertaining to those particular items.

Initial Startup, Condensing Turbines
I. Thoroughly drain the steam inlet line, turbine casing, steam chest,
and the exhaust line of any accumulated water. Close the drain
valves when all water is drained from the system.
2. Adjust the governor speed setting to minimum speed. If overload
hand valves (1, Figure 8-6) are furnished, they must be fully
opened.
3. Latch the resetting lever (11, Figure 8-4) open the turbine exhaust
valve and start the condensing equipment.
4. Open the steam inlet shut-off valve until the turbine speed reaches
approximately 500 rimin.

Caution: Steam should not be admitted to the turbine casing by
partially opening the inlet steam shut-off valve while the
rotor is stationary. This condition will cause uneven
heating of the turbine rotor and casing which may result
in a distorted casing, bowed rotor shaft, or other related
problems.

5. Adjust the sealing steam valve so that a slight amount of steam is
discharged from the leak-off drain lines.
Note: 3 to 5 psig (0.20 to 0.35 bar) is usually sufficient sealing
steam pressure. However, care must be taken to prevent
steam from blowing out of the packing cases and along the
turbine shaft.