New Column: Insulation Finishes – This Month’s Topic: Polymeric (Plastic) Rolls or Sheets
Product Characteristics of Weather Barriers, Vapor Retarders, and Finishes
Polymeric (plastic) rolls or sheets are available at various
thicknesses. These materials are glued, solvent welded, or taped depending on
the polymer. Elbows and tees are also available for piping for some type of
polymers. Typical polymeric (plastic) jacketing materials are:
- Polyvinyl Chloride (PVC)
- Polyvinyliedene Chloride (PVDC)
- Polyethylene Terephthalate (PET)
- Polyvinyl Flouride (PVF)
jackets are made of a durable, attractive, and easy–to–clean material that is
typically field–applied over unfaced insulation and most factory–applied
jackets where additional protection is necessary. PVC jackets are covered by
ASTM Standard Practice C921–10, Types I and II, Grade 4.
jackets are available in several thicknesses and colors. Standard thicknesses
are 10, 15, 20, 30, and 40 mils, with 20 and 30 mils being the most common
thicknesses. Thicknesses of 30 mils are recommended for outdoor applications.
Jacketing meant for outdoor use should be UV stabilized. While PVC jacketing is
usually white, jackets are available in a variety of colors (colored jacketing
is normally not available with UV stabilization).
manufacturers and fabricators offer PVC “cut and curl” jacketing products.
Fitting covers are also available for covering elbows, tees, valves, flanges,
mechanical couplings, drain bodies, strainers, end caps, and other common
piping products. Accessory products (solvent adhesive, tapes, stainless steel
thumbtacks, etc.) are also available from manufacturers.
jacketing up to 30 mil thicknesses generally meet 25/50 flame–spread and
smoke–developed indexes. Jacketing temperatures should be kept below 150°F for
hot services. PVC jackets can be used in areas requiring frequent washdown and
are used extensively for applications requiring USDA and FDA approval. To
achieve USDA and FDA approval, PVC jackets should be installed with continuous
solvent welded joints and seams. PVC jackets and fittings, when applied over an
intermediate vapor retarder and properly sealed, can be used on cold systems.
is a flexible and tough vapor–retarder facing that is applied to the exterior
of pipe, vessel, and equipment insulation systems. This vapor retarder consists
of a biaxially oriented homogeneous opaque white polymer film. It can be
factory or field applied to the surface of the insulation and is available in 2
thicknesses, 4 and 6 mils, both at 35.5″ wide and more than 250 feet long. When
factory applied to insulation, the lap joint of the vapor retarder is sealed in
the field using a self–sealing lap (SSL). The PVDC tape is the same type of
homogeneous white film to which an adhesive backing which does not require
release paper, has been applied. The tape is available at 2 and 6 mil
thicknesses; widths of 1″, 2″, and 3″; and 150 feet length. PVDC films are not
intended for exterior applications unless protected by a suitable weather
Standard Specification C1136–10, Types VII and VIII covers this type of
vapor–retarder facing for use where insulation outer surface temperatures are
–20 to 150°F. This ASTM standard specification establishes requirements for
permeance, burst strength, tensile strength, dimensional stability, flame/smoke
performance, zero fungal growth, and lack of cracking or delamination.
Standard Practice C921–10, Type II, Grade 4 covers this type of film for use as
a vapor–retarding outer jacket on thermal insulation over mechanical equipment
such as tanks, pipe, and vessels. The 6 mil PVDC film meets the permeance
requirements of Class A, “Extremely low permeance” or 0.01 perms maximum. The 4
mil PVDC film meets the permeance requirements of Class B, “Very low permeance”
or 0.02 perms maximum.
applications for PVDC vapor retarder is in insulation systems for pipe,
equipment, tanks, and ducts—especially those operating at temperatures below
ambient such as food and beverage lines, refrigeration, ammonia refrigeration,
and liquid natural gas (LNG) pipe. PVDC film is applied to the insulation on
straight sections of pipe or to large surfaces like tank or duct walls. PVDC
tape is used to seal joints in the film, at vapor retarder butt joints on pipe
insulation, wrapped around complex insulation shapes such as fittings and
elbows, and can be used to repair physical damage to the vapor retarder film.