Page 388 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Steam Turbines and Turboexpanders 367

8. Make necessary governor adjustments to attain desired speed as
load is applied.
9. Observe bearing temperatures and introduce sufficient cooling
water to the oil cooler to maintain bearing oil temperatures of
140°F to 190°F (60°C to 88°C).
10. Check the overall operation to determine all conditions to be satis-
factory.

Overload Hand Nozzle Valves
Optional hand valves (Figure 8-6) are sometimes used to control the
steam flow through an extra bank of nozzles. These valves can serve three
functions:
1. When closed, the valves will provide more efficient turbine opera-
tion at reduced load with normal steam conditions by reducing the
nozzle area and thereby reducing the steam flow.
2. In some applications, hand valves are used to develop the required
power by opening the valves when steam conditions are less than
normal (such as encountered during boiler startup).
3. Hand valves are sometimes used to develop increased power for
meeting overload requirements with normal steam conditions.

(See also the section on hand valve positioning versus turbine power,
speed, and operating steam conditions normally provided in the manufac-
turer’s operating and maintenance manuals.)

Note: Hand valve must be positioned either fully open or fully
closed. firning the valve counterclockwise approximately
11/2 turns will open the pilot valve. lkrning the valve ap-
proximately nine additional turns will fully open the main
valve disk. Open all hand valves during startups to ensure
even heating of casing and prevention of valves binding in
the casing.

Turbine Shutdown
1. Shut the turbine down by striking the top of the trip lever by hand.
2. Observe the action of the trip valve and linkage.
3. Close the inlet steam shutoff valve.

Note: Shutoff valves, located in the turbine inlet steam piping,
must be closed after the trip valve has closed. Do not use the
trip valve as a shutoff valve.