Page 99 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

PIPING 2.49

TABLE 2.6 Thermoplastic Materials and Valve Types

Valve design Materials Size range, in
Ball (union design) PVC, CPVC, PP, PVDF 1 / 4 −4
Ball (compact design) PVC, CPVC 1 / 2 −3
Ball, multiport PVC, CPVC, PP, PVDF 1 / 2 −3
Diaphragm PVC, CPVC, PP, PVDF 1 / 2 −10
1
Butterfly PVC, CPVC, PP, PVDF 1 / 2 −24
Globe PVC, CPVC, PP 1 / 2 −4
1
Gate PVC 1 / 2 −14
Ball check PVC, CPVC, PP, PVDF 1–4
Swing check PVC, PP, PVDF 3 / 4 −8
Labcock PVC 1 / 4
Foot PVC, CPVC, PVDF 1 / 2 −4
Pressure relief PVC, CPVC, PP 1 / 2 −4
Solenoid PVC, CPVC, PP 1 / 2 −1

VALVE ACTUATORS

Valve Categories

There are three operating methods for valve actuators: multiturn (used for gate, globe, and
diaphragm valves), quarter-turn (used for plug, ball, and butterfly valves), and linear (used
for gate, diaphragm, and globe valves). The valves can either operate manually or be power
actuated. There is no generally recognized code or standard for valve operators outside of
those concerned with specific, high-risk industries, for example, nuclear work.

Manual Operation
Manually operated valves are usually used when the valve is easily accessible, does not
require automatic operation, or is operated infrequently. Multiturn valves use hand wheels,
gears, or levers. The most common is the handwheel. If the operating effort is too high
for a handwheel, a gear box could be installed. A less common gear arrangement is the
impact gearbox. This consists of a free-wheeling handwheel for part of its rotation that
then imparts a hammer blow to the stem to break loose a stuck gate or globe valve. For the
torque necessary to open a gate valve against an unbalanced force, refer to Fig. 2.22. This
is generally referred to as “breakaway torque.”
Quarter-turn and linear valves use a lever.

Power Actuators
Power actuators are used where valves are remotely located, frequent operation is required,
or automatic operation is necessary due to system considerations.
Depending on the type of valve, the actuator will be required to deliver output for rotary
or linear motion. This may be for ON/OFF (fully opened to fully closed) service, or stroke
functions such as those required to keep a valve partially open, or a combination of both.
The power source must be capable of exceeding the torque requirements needed by the
actuator by an adequate safety factor. In the case of throttling, a detailed analysis may
be required. The worst case is in providing the breakaway torque. Valve-operating torque
is never constant, varying with closure member position. Typically, the peak torque is

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