operator. The following are some key things to
completely and stay in that position. This will be
look for:
indicated by the stem rising to the top of the sight
tube.
a. Positive signs of lubrication
3. Close globe valve A. The indicator stem should
b. Loose or improperly positioned hold down
drop, indicating that the hytrol valve is closed.
brackets
(The speed of this closure is controlled by the
c. Excessive bending in the cable or individual
size of the orifice in the strainer and orifice
universal joints
assembly. This small hole prevents excessively
fast closing.)
d. Improperly positioned packing gland or a
packing nut that is too tight on the deck or
4. Open globe valve B. The unloading valve should
bulkhead penetration fittings
resume automatic operation.
e. Rusted or corroded fittings
VALVE OPERATOR MECHANICAL LINK-
In testing and inspecting automatic control valves,
AGES. Valve operator mechanical linkages, as we
mechanical linkages, and their components, you may
previously stated, are used to connect a remotely
find that many of the problems will be obvious. In the
positioned valve with an operator (handwheel). In this
following paragraphs, we will discuss the more common
section, we will discuss the tests and inspections for the
problems and tell you how to determine the required
two types of mechanical linkages used on gas
repairs.
turbine-powered ships: (1) the rods and universal joint
type and (2) the cable type.
Maintenance and Repair Procedures
Rod-Type Linkage. In the design of the rod-type
linkage, a series of rods is connected together by
Most maintenance will be covered by the PMS or
universal joints. The number of rods is determined by
maintenance procedures described in an appropriate
the distance between the operator and the valve. The
manufacturer's technical manual. Therefore, we will
number of joints is determined by the number of rods
briefly discuss some preventative maintenance and
used and the number of bends that are less than 90
focus primarily on repair and component replacement.
degrees. If a bend of 90 degrees is needed, then a
Because they are the most important preventive
gearbox assembly should be used.
maintenance actions, we will start with cleaning and
lubrication procedures.
Cable-Type Linkage. In the design of the flexible
CLEANING AND LUBRICATION. T h e
cable type of linkage, a wire woven cable is housed in a
cleaning and lubrication of automatic control valves and
flexible metal tube. In this type of linkage, gearbox
mechanical linkages is extremely important. You may
assemblies should also be used when 90-degree bends
not realize how important it is until you are told to
are required.
operate a valve and you cannot get the valve to move
The methods you will use for testing and inspecting
(open or close). Valves and operators located in high
these two types of mechanical linkages are very similar.
moisture systems or in the bilge areas are extremely
These requirements are normally covered under the
susceptible to corrosion and will require more attention
PMS. When testing these operators, your primary
than any other propulsion plant valves. A key thing to
concern will be to check the freedom of movement. If
remember is all valves do not use the same lubricants or
difficulty in operation occurs, there are several areas you
solvents.
should inspect as possible causes of the problem. Use
High-pressure Air System Valves. High-pressure
the following sequence of steps:
(HP) air system valves require a nonpetroleum-based
1. Determine if the problem is the operator or the
lubricant. This type of lubricant must be used because
valve. To do this, disconnect the operator from
of the static electric charge that is developed as the air
the valve and retest the operator. If it is still hard
moves through the piping.
to operate the operator, then the problem is the
operator.
WARNING
2. Next, you must determine where the operator is
binding. The first and easiest method you can
Use of a petroleum-based lubricant can
create a very explosive condition.
use is to visually inspect the entire length of the
