functioning of the system and of the machinery and
Changes in direction of piping should be made by
pipe bends and offsets where space permits. Otherwise,
equipment served by the system.
straight lengths of pipe and the fittings specified for the
Components welded in a piping system must be
system should be used.
accessible for repair, reseating, and overhaul while in
place. Complex assemblies such as valves, strainers,
and traps in high-pressure drain systems must be
removable as a group if they require frequent
Do not pierce decks and bulkheads unless it is
overhauling and cannot be repaired in place.
absolutely necessary. This is particularly true of main
subdivision bulkheads. When piercing is necessary, try
Valves should be designed so that they can be
to do it close to boundaries of compartments and avoid
operated with a minimum amount of force and with
cutting bulkhead stiffeners, deck beams, and plating
maximum convenience. Sometimes you must stand on
butts and seams.
slippery deck plates to turn a valve handwheel, or you
must reach over your head or around a comer. In these
Piping under pressure should be routed around
situations, you cannot apply the same amount of torque
voids, cofferdams, and other nonvented spaces. Bypass
that you could if the handwheel was more conveniently
inner bottoms, ballast tanks, fuel tanks, freshwater
located. Therefore, the location of the handwheels is a
trunks, and voids except when it is necessary to service
very important design consideration. (When possible,
valves should be installed in the upright position.)
Some piping systems other than those serving a
Toggle mechanisms or other mechanical advantage
tank are permitted to pass through fuel oil or diesel oil
devices must be used where the amount of torque
tanks. This piping must be of schedule 80 thickness if
required to turn a handwheel is more than could
made of steel, and must have welded joints.
normally be applied by one person. Keep the
mechanical advantage devices well lubricated. If they
Combustible and flammable liquid piping is to be
do not produce easy operation of the valve, then a power
located at least 18 inches away from surfaces that have
operation must be used.
temperatures under their insulation greater than 450F.
This temperature limitation can be 650F for surfaces
Install locking devices if accidentally opening or
in the vicinity of lubricating oil piping.
closing a valve could endanger personnel or the ship.
Any locking device installed on a valve must allow ease
Do not install steam and liquid piping near
of operation and discourage unauthorized personnel
electrical equipment if at all possible. Any drips or
from tampering with the valve.
damage the equipment. If the system has to be installed
Globe valves may be installed so that the pressure
near electrical equipment, install adequate shielding to
is applied either from the top or the bottom of the disk.
protect the equipment. Any flanges or unions in the
The method used will depend on which one is best for
system are to be installed away from the electrical
operating, protecting, maintaining, and repairing the
machinery served by the system. When a continuous
flow is required and no harm will result if the disk of a
The amount of piping passing through messing and
globe valve becomes detached from the stem, the
berthing spaces should be kept to a minimum. The
pressure should be below the disk. Where damage is
piping in such spaces should be symmetrical, neatly
likely to occur if the disk becomes detached from the
arranged, inconspicuous, and should not interfere with
stem and leaves the valve wide open, the pressure
the efficient functioning of the system.
should be above the disk. Check valves must be
Try to keep piping out of medical and dental spaces
installed so that the disk will open when the fluid flows
except where it is necessary to service the equipment in
in the correct direction, and close if back flow occurs in
Flanged and union joints should be located where
JOINTS AND CONNECTIONS
they are least affected by pipe line forces caused by
thermal expansion or other causes.
Welded joints are currently used whenever possible
in carbon steel, alloy steel, and other weldable piping.
These welded systems will have several types of valves
with flanged connections to allow their removal for