350
Fundamentals of Corrosion
PVC is unaffected by most acids and bases but it is affected by
some hydrocarbons and chlorinated solvents. Chemical resistance
charts should be checked for specific applications.
The PVC jacket service temperature limit is between −32 and
125°F.
It is a tough and flexible material that does not show dents. Because
of its low permeability, PVC can be used in wet environments if the
seams have been sealed properly. Because its flame spread is high,
PVC is not recommended for use in areas of fire risk.
PVC is available from manufacturers in a full range of accessories.
It is easy to apply in the field and can be cut for additional fitting
covers. It is recommended that the vendor precurl the rolls to avoid
extra cost in the field. Fiberglass fabric laminated to PVC is a relatively costly jacket alternative.
6. MAP: mastic asphaltic coating:
MAP is suitable for the vapor barrier coating of irregular-shaped
equipment and pipe fittings in cold and dual-temperature services.
It is resistant to dilute acids and alkali as well as abrasion. It must be
stored and applied at temperatures of 40ºF or higher. MAP material
is combustible.
7. LTM: low-temperature mastic (nonasphaltic):
LTM is suitable for vapor barrier coating on irregular-shaped
equipment and pipe fittings in cold and dual-temperature services,
including cyclic temperature service. It is recommended for additional protection against chemical environments.
11.3.2.4 Design Requirements for Various Services and Systems
1. Antisweat service:
For antisweat as well as cold services of piping and equipment,
it is necessary to keep the temperature of the insulation above the
highest possible dew point temperature of the condensation temperature of the environment. As an aid, the outer cover should have
a high emissivity.
For antisweat insulation thickness, vendors, tables can be used.
The normal conditions used to select thicknesses to prevent condensation on the insulation outer surface are as follows:
Cover emissivity 0.9
Dry bulb 90ºF
Relative humidity 80%
Fundamentals of Corrosion
PVC is unaffected by most acids and bases but it is affected by
some hydrocarbons and chlorinated solvents. Chemical resistance
charts should be checked for specific applications.
The PVC jacket service temperature limit is between −32 and
125°F.
It is a tough and flexible material that does not show dents. Because
of its low permeability, PVC can be used in wet environments if the
seams have been sealed properly. Because its flame spread is high,
PVC is not recommended for use in areas of fire risk.
PVC is available from manufacturers in a full range of accessories.
It is easy to apply in the field and can be cut for additional fitting
covers. It is recommended that the vendor precurl the rolls to avoid
extra cost in the field. Fiberglass fabric laminated to PVC is a relatively costly jacket alternative.
6. MAP: mastic asphaltic coating:
MAP is suitable for the vapor barrier coating of irregular-shaped
equipment and pipe fittings in cold and dual-temperature services.
It is resistant to dilute acids and alkali as well as abrasion. It must be
stored and applied at temperatures of 40ºF or higher. MAP material
is combustible.
7. LTM: low-temperature mastic (nonasphaltic):
LTM is suitable for vapor barrier coating on irregular-shaped
equipment and pipe fittings in cold and dual-temperature services,
including cyclic temperature service. It is recommended for additional protection against chemical environments.
11.3.2.4 Design Requirements for Various Services and Systems
1. Antisweat service:
For antisweat as well as cold services of piping and equipment,
it is necessary to keep the temperature of the insulation above the
highest possible dew point temperature of the condensation temperature of the environment. As an aid, the outer cover should have
a high emissivity.
For antisweat insulation thickness, vendors, tables can be used.
The normal conditions used to select thicknesses to prevent condensation on the insulation outer surface are as follows:
Cover emissivity 0.9
Dry bulb 90ºF
Relative humidity 80%