Volume 6, Issue 1 - Naval Sea Systems Command - The US Navy

SEAFRAME
24
By
Martin
Cohen
Core equities
The Navy’s Environmental
and Natural Resources Program Manual
requires the fleet to meet a zero plastic
waste discharge requirement (unless ship
safety or the health and safety of the crew
are compromised). A U.S. Navy aircraft carrier generates
nearly 1,000 cubic feet (30 cubic yards) of plastic waste per
day. By comparison, smaller ships can generate nearly 50
cubic feet of plastic waste per day. While plastic waste can be
removed from ships during underway replenishments every
three to four weeks, the average aircraft carrier can generate
up to 30,000 cubic feet (1,000 cubic yards) of plastic waste
during that time, and the average surface combatant up to
1,500 cubic feet (more than 50 cubic yards).
Considering that ships cannot discharge plastic
waste overboard, it is easy to see the potential havoc that
this can wreak on operations during a deployment of a U.S.
Navy ship. Plastic waste processors (PWPs), also referred to
as compressed melt units (CMUs), were originally designed
and outfitted in the fleet from late 1995 through 1998,
and are used by the fleet to process shipboard generated
plastic waste into dense disks suitable for long-term storage
onboard prior to shore disposal. PWPs reduce the volume of
plastic waste by a 30:1 ratio. These processors allow ships
to retain their plastic waste onboard when at sea and comply
with zero-plastic waste discharge requirements, while
enabling them to operate unrestricted throughout the world.
Fleet operations have shown that the original
design PWPs required excessive man-hours to operate
PLASTIC WASTE
PROCESSOR
Improving the Ability of New Construction
Ships to Process Plastic
and had high corrective and preventative maintenance
costs. Additionally, PWP cleanliness issues related to the
processing of food contaminated plastics have impacted
the fleet. In FY 00, the Naval Sea Systems Command
(NAVSEA) directed Naval Surface Warfare Center,
Carderock Division’s (NSWCCD’s) Environmental Quality
Department to improve the PWP design. The initial goals
were to reduce operational and maintenance man-hours
associated with the equipment by 40 percent without
modifying the shipboard interfaces, and enhance the
cleanliness of the equipment.
Assessments were made on the failure rates of all
components, corrosion, and system complexity. High failure
rate components were removed or replaced. Materials
were changed to reduce corrosion issues, and the system
was greatly simplified to enhance reliability, and ease
maintenance and cleaning. Replacement components and
subsystems were designed, fabricated, and then tested for
reliability and ruggedness in the laboratory and in the field.
The modified plastics waste processor (MOD I PWP) has
34 percent fewer components and a processing rate 200 to
300 percent greater than the legacy PWP. Also, the electrical
and drive systems were revamped to enhance simplicity and
dependability, and support increased processing rates.
The lower frame of the unit was redesigned to
promote ease of cleaning, which is important due to the
processing of food contaminated plastic waste. The modified
unit incorporates self-cleaning nozzles that are connected
to the ship’s hot potable water service, greatly reducing