Est 1967
95 Second Street, Booysens Reserve, Johannesburg
South Africa
PO Box 38653, Booysens 2016
Tel 27-11-835 2127
Fax 27-11-496 1263
E-mail vm@netdial.co.za
Who are we?
Vedder & Moffat are a leading South African Thermal Insulation Contracting Company specializing in Hot and Cold Insulation since 1967.
In all our work we never compromise on quality and have a reputation for quality of workmanship. Insulation is the single most effective way to control energy expenditure at home and industrial applications.
GENERAL NOTES
Equipment or pipework with an operation temperature greater than 55°C in case of metallic surfaces and 65°C in the case of non-metallic surfaces should be insulated so that the surface temperature after insulation (cold surface temperature) does not exceed 55°C.
It is recognized that temperatures of 60°C or greater will result in extreme discomfort to personnel and therefore a maximum cold surface temperature of 55°C should be considered as prudent.
If the fluid inside the pipe or vessel is likely to remain static for long periods when the ambient temperature is below the freezing point of the fluid, it is important that this shall be stated. Also, the fluid in small diameter pipes may be especially susceptible to freezing, particularly if the rate of flow is intermittent or slow, it may be necessary to consider the use of supplementary means of heating, possibly only in local areas, like heat tracing.
SELECTION OF HOT INSULATION MATERIALS
The objective is to select a material, which will serve the insulation purpose at the lowest cost. This can be a complicated procedure.
In addition to the factors listed in section 2.2 careful consideration should be given to insulation thickness. On pipework an over-specification of thickness creates a needless increase in the cost of the outer protection.
When a multi-layer system of insulation is envisaged, the selection of materials is interdependent on the type of protection and the calculations as set out in Annex 2 para. 5.2. For example, an aluminium protection will result in a higher cold surface temperature and a lower heat. (Aluminium protection has a low emissivity and therefore radiates less heat).
Where constant load supports are involved, the mass of the insulation system becomes critical and must be kept within the tolerances of such constant load supports. Where used for internal linings of ventilation ductwork the thermal insulating material itself should be non-combustible as defined in BS 476: Part 4
HOT INSULATION MATERIALS
Common to all these materials, it is recommended that their use be limited to conditions of 90% of the manufacturer’s limiting temperatures in order to safeguard against temperature surge at start-up operations of plant.
Please note: Information provided in the following tables is generic information suitable for feasibility studies and cost estimates.
Actual figures may differ from manufacturer to manufacturer and must be confirmed with the individual manufacturer.
APPLICATION OF HOT INSULATION
Either pipe section, mattress or any flexible insulation may be used for pipework. However, practical reasons preclude the use of mattress or flexible insulation where the outside diameter of the pipe or the outside diameter of any previous layer of insulation is 200mm or less.
Where mattress or materials of low density are used and metal is the protection medium, supports should be provided for the metal at not more than 1-metre intervals where the pipework is horizontal or inclined up to 45°. Between 45° and the vertical the spacing of the supports is dependent on temperature and expansion requirements. (Refer BS 5970).
As a guide, the expansion allowances on pipework are generally 1mm per running meter per 100°C of temperature. In all applications of insulation the material must be well butted together and in the case of multi-layer applications all joints of each subsequent layer must be staggered from the previous layer. Weld pins or clips, binding wire and strapping are used for securing the insulation as a single or composite system dependent on the circumstances.
GENERAL NOTES
Cold insulation should be considered where operating temperatures are below ambient and where protection is required against heat gain, condensation or freezing.
In designing an insulation system where formulae and surface coefficients are used they should be to an appropriate international standard, for example, BS 5422 is recommended. In selection of material density, it should be considered whether insulation requires to be load bearing or not.
For whatever purpose cold insulation is required, the insulation system is only as good as its vapour barrier and the care with which it is installed. A vapour barrier is a membrane of very low permeance placed on the warm side of insulation to limit the flow of water vapour into the insulation. Table 7 of BS 5970 shows the water vapour permeance of various insulation materials.
Where there is a differential in temperature or humidity between the cold surface of the equipment and the ambient temperature a differential water vapour pressure occurs. The greater the temperature differential, the greater the differential water vapour pressure. Water vapour should not be confused with moisture. Water vapour is a transparent, tasteless and odourless gas capable of permeating through most materials depending on the pressure differential on either side of the insulation.
Permeability of water through a vapour barrier is expressed in Metric Perms in the metric system. A Metric Perm is the passage of 1 gram of water through a material with a surface area of 1m2 for 24 hours and a pressure difference of 1mm Hg.
Many materials, which are moisture-resistant, are not necessarily vapour-resistant. All insulation materials are susceptible to water vapour penetration to various degrees. If penetration is not prevented, the water vapour condenses to moisture or ice when its temperature reaches the dew point. This will, in time, saturate the insulation thereby rendering it useless. To prevent this from taking place, a vapour barrier is applied on the warm side of the insulation.
Even a pinhole through the vapour barrier can eventually render the insulation system useless; therefore the selection of a vapour barrier needs careful consideration. Foil or sheet usually have the better permeability rating but foil has poor resistance to mechanical damage and needs a protective cover or protective laminate. Sheetmetal has a good rating but requires great care in the sealing of joints and fastenings.
Water, solvent and mastic based vapour barriers tend to be resistant to mechanical damage. Their permeability rating varies from water based at the bottom of the scale to cured resins at the top. Most of these types, however, need to be suitably reinforced.
When using water-based formulations, they dry out, and in doing so leave minute pinholes. It is therefore essential that the manufacturer’s recommended thickness be considered as a minimum to prevent pinholes extending continuously through the coating and, as a further precaution, the application must consist of multiple coats.
In the case of solvent based vapour barriers the manufacturer’s application procedures must be carefully followed, as the danger of solvent entrapment exists due to premature over coating resulting in surface “bubbles”.
Resin-cured vapour barriers are excellent but again the manufacturer’s recommended thickness should be considered minimum. Adherence to the manufacturer’s mixing proportions is mandatory. The application must be multiple coats. Vapour barrier applications are only as good as the applicator. Where the insulation terminates, the vapour barrier must be returned to the cold equipment so as to totally encapsulate the insulation.
In selecting a vapour barrier, material comparisons should be made between the various permeability ratings as supplied by manufacturers as there may be vast differences between materials as reference to Table 7 of BS 5970 shows.
Care should be taken to ensure that the choice of vapour barriers does not affect the fire performance of the whole assembly of insulating and finishing materials (see 4.2).
The design of the cold insulation system should assume that at some time a breakdown of the vapour barrier may occur.
In such an event, and in the case of coldrooms, it is better that the water vapour has an unhindered path to the cold surface to enable it to be drawn off by the refrigeration equipment. In the case of pipework and vessels, it is preferable that the water vapour has free passage to the cold surface where the resultant water or ice will be encased by the insulation.
A break in the vapour barrier of the insulation system will eventually cause the system to fail but its effective life will have been prolonged by a design which permits the through transmission of water vapour.
Adhesives or mastics for the application of insulation should be used with care as vapour dams may be created which would negate the principle of the previous paragraph.
If one has limited experience, it is recommended that a member of TIASA be consulted before embarking on cold insulation. Whatever the primary reason for cold insulation, it should be designed to prevent condensation.
Condensation occurs when water vapour in the atmosphere comes in contact with a surface at a temperature of less or equal to the dew point. Therefore, if the surface temperature is less than the dew point, condensation will occur.
The presence of condensation on the warm side of the vapour barrier has no detrimental effect on the insulation but, nevertheless, it is a condition, which has to be avoided. To prevent condensation, the insulation thickness should be so designed that temperature on the warm side of the vapour barrier is above the dew point.
In calculating the thickness of insulation required to prevent condensation, it is prudent to know or assume conditions of high relative humidity. If the fluid inside the pipe or vessel is likely to remain static for long periods when the ambient temperature is below the freezing point of the fluid, it is important that this shall be stated. Also, the fluid in small diameter pipes may be especially susceptible to freezing, particularly if the rate of flow is intermittent or slow, it may be necessary to consider the use of supplementary means of heating, possibly only in local areas, like heat tracing.
VACUUM INSULATION PANELS
VACUUM INSULATION
Vacuum insulation is an advanced thermal insulation technology that significantly outperforms closed-cell foams, foam beads or fiber blankets. While these traditional systems attempt to trap gases to reduce the transfer of heat, vacuum insulation removes the gases within the insulating space. With the space evacuated or placed ‘under vacuum’, the molecular presence and movement needed to transfer heat is greatly reduced.
VACUUM INSULATION PANELS
Vacuum Insulation panels, or VIP’s, consist of a filler material called a ‘core’ that is encapsulated by a thin, super-barrier film, such as a metal foil or metallized film laminate. The encapsulated system is then evacuated to a vacuum between 0,13 and 1,30 Pa and sealed. The actual vacuum required depends on the specific core material used and the desired thermal resistance or ‘R-value’ of the finished panel. The core, when under vacuum, serves to interrupt the ‘mean free path’ of what few heat transmitting molecules remain in the panel, while also withstanding external pressures that can be as high as 101,3 kPa due to the forces exerted on the VIP from atmospheric pressure. Being nearly impervious to outside gases, the barrier film sustains the required vacuum level (and thus, R-value) for the desired life of the panel. To trap any molecules entering the panel or the modest ‘outgassing’ that may occur from the VIP component materials, water and/or gas adsorbing materials are also placed inside the panel to maintain the vacuum for the intended life of the VIP.
PRODUCT SUMMARY
The vacuum insulation ‘core’ is a 100 percent open-cell, micro cellular polystyrene foam used as a filler in VIP’s. When vacuum levels are held between 13 and 130 Pa, the insulating potential for VIP’s is three to seven times greater than conventional insulating systems. Therefore, where thinner or more reliable insulation is required, VIP’s can offer significant design flexibility and cost savings. The insulation core is available as gray board stock in various grades and thicknesses to meet the performance needs of the marketplace.
VACUUM INSULATION FOR CRYOGENIC PIPING AND VESSELS
This is a system, which utilizes an outer metal jacket, which is installed around the pipe or vessel containing the medium in such a way so as to achieve a cavity between the outside of the pipe/vessel and the jacket.
This cavity is then placed under a negative pressure and a vacuum sustained.
This insulating system is conventionally utilized for maintaining cryogenic products such as oxygen and nitrogen at temperatures of -196°C and -187°C respectively.
SELECTION COLD INSULATION OF MATERIALS
Closed-cell insulation is the most commonly specified material used for cold work because it possesses a degree of resistance to water vapour and because the thermal conductivity (k factor) of some of these materials is better than the fibrous alternative products.
Selection of insulation materials should be carefully considered where the possibility of steam purging of the equipment is required or for other reasons which may cause the temperature to be increased to a level which exceeds the maximum limiting temperature of the insulation materials, i.e., material then deteriorate.
Special precautions to prevent the possibility of combustion must be exercised when insulating piping, fittings or equipment containing oxygen, as the insulation system should then not contain any organics. It is therefore strongly recommended that the material suppliers are consulted prior selection of the insulation material. The fibrous materials referred to in section 3.3 may be used for cold insulation where conditions such as fire resistance so demand. However, because of their poor resistance to water vapour, extra care must be taken in the selection and application of the vapour barrier.
In case of fire, certain insulation systems may generate appreciable quantities of smoke and noxious and toxic fumes. Consideration should be given to the choice of materials, bearing in mind their location, for example, in enclosed areas or adjacent to air ducts through which smoke or fumes may spread as per the local requirement and specifications.
If there is a potential hazard from contamination by oil or other flammable chemicals, a suitably resistant finish, for example, metal sheet or appropriate non-absorbent coating, shall be applied over the vulnerable areas. The lapped joints of sheet finishes shall be arranged to shed contaminating fluids away from the insulating material.
PRODUCT SELECTION GUIDE – COLD INSULATION -
Please note: Information provided in the following tables is generic information suitable for feasibility studies and cost estimates.
Actual figures may differ from manufacturer to manufacturer and must be confirmed with the individual manufacturer.
APPLICATION OF COLD INSULATION
Generally on pipework, preformed pipe sections should be used or alternatively an in-situ or spray application could be considered. All insulation should fit snugly around piping and equipment. On low temperature insulation work all attachments to the piping or equipment and projecting through the insulation should also be insulated for a distance of four times the thickness of the basic insulation from the point where the projection is exposed.
All the insulation and the vapour barrier should be continuous at pipe supports. Where metal cradles preformed to the outside diameter of the insulation are provided at the pipe supports the cradle should be designed to prevent undue compression of the insulation due to the weight of the insulated pipe.
Higher density insulation preformed material often manufactured from PUR, PIC, phenolic foam or wood can be used between the support and the pipe to accommodate the weight if considered necessary.
Insulation contraction joints should be provided for Firebreaks should be provided at, for example, 20m maximum or where the insulated pipe passes from one building to another. Where total thickness of insulation exceeds 50mm it should be applied to multiple layers and all joints should be staggered to prevent direct heat paths to the cold face. The creation of cavities should be avoided.
JOINT SEALERS AND ADHESIVES
All materials intended for use for cryogenic insulation of pipes and vessels should be checked for their suitability at low temperatures and if, for example, no acceptable joint mastic is available for -196°C (liquid oxygen, nitrogen, etc) then only the joints on the outer layer on a multi-layer system should be sealed.
Joint sealers and adhesives should be completely compatible with the insulation, vapour barrier and the item being insulated (refer manufacturer’s recommendations).
When insulating low temperature pipework, it is advisable to create circumferential vapour dams extending from the bare pipe to the vapour seal on the warm side of the insulation. The longitudinal spacing of the dams is arbitrary and as a guide, 2m, for very low temperatures to 10m for, say chilled water, should be considered. The purpose of the dams is to prevent the failure of long sections of pipe insulation should the warm side vapour seal be ruptured in any way.
SUPPORTS FOR INSULATION
Insulation can be supported by the following:
- · Adhesive
- · Pins - plastic or nylon
- · Strapping bands for large cylindrical surfaces
- · Pressure-sensitive tape for small diameter surfaces
- · Pre-installed insulation support rings, normally used on large vertical vessels.
VAPOUR BARRIERS
The following tables provides a guideline for the required water vapour permeance for different plant cold surface temperatures:
Required water vapour permeance in relation to plant temperature at an ambient temperature of +10°C (dry bulb)
Temperature of plant (cold surface) Water vapour permeance of barrier
°C g/(sMN) Metric Perms
0 0,010 0,12
-5 0,004 0,046
-10 0,002 0,023
-15 0,0015 0,017
-20 to –40 0,001 0,012
Note: For temperatures lower than –40°C please consult a TIASA member. Refer matrix of members elsewhere in this publication.
SELECTION GUIDE FOR VAPOUR BARRIERS
TYPE PRODUCT
NAME TEMP
RANGE
°C REC
D.F.T
(mm) ** WET
FLAMABLE EXPOSURE
RESISTANCE NON-
SUITABLE
SUBSTRATE WATER
VAPOUR
PERMEANCE
g/s MN * METHOD
OF APPLICATION
Bituminous BE2 Bitumen
Emulsion -5/55 1,5 No Internal None 0,0083 Brush
BE Emulsion -5/55 1,5 No Internal None 0,0022 Trowel
570 Rubberized
Emulsion
-30/60
1,5
No
Internal
None
-
Brush
Epoxy 769 Epoxy Paint -10/8 0,3 Yes External EPS - Brush/Spray
304 Epoxy Coating -10/120 0,3 No External None - Brush
Abecote SF322 Dry 120 ±1,0 Flash 0°C 0,005 Brush
Flintoat 390 -10/50 ±0,5 Flash 0°C 0,058 Brush
Ivory 340 -10/90 0,8 No Internal None 0,003 Brush
1 C KL Film N/A Internal None 0,001 N/A
1 C KH Film N/A Internal None <0,001 N/A
1 C RH Film N/A Internal None Neg. N/a
Elastomeric Foster Monolar -30/120 0,76 Yes External EPS 0,006 Brush/spray trowel
Foster 95-44 -73/121 Seal’t Yes External EPS Trowel/glove
Foster 30-45 -60/149 Seal’t Yes External None Trowel/glove
800 Hypalon -40/120 0,3 Yes External EPS 0,000 Brush/spray
795 PU Coating -20/180 0,3 Yes External EPS 0,000 Brush/spray
696 Elastothane -30/120 1,0 No External None - Brush
153 FR Mastic -30/80 1,9 Yes External EPS N/A Trowel
625 Non-slump Mastic -40/120 Bead Yes External EPS N/A Gun
151 Oleo Mastic -70/150 Bead No Internal None N/A Gun/trowel
Synthetic Foster 30-36 -18/82 0,9 No Internal None 0,083 Brush/spray
Emulsions Foster 30-70 (lagtone) -46/82 0,4 No External None 0,180 Brush/spray
Foster 35-00 -29/93 1,0 No External None 0,090 Trowel/glove
2415 Plustex -20/120 0,45 No External None 0,057 Brush/trowel
2191 Plustex -20/80 0,45 No External None 0,072 Brush/trowel
249 Plustex -20/90 0,45 No External None 0,05 Brush/trowel
835 Acryl seal -20/80 0,5 No External None - Brush
147 Acryl Coat -20/80 0,2 No External None - Brush
158 Vapourseal -30/85 1,3 No External None - Brush/trowel
Other Foster 65-05 -29/93 2,0 Yes External EPS 0,007 Brush/spray
Foil-Mylar -70/100 Film N/A Internal None 0,001 N/A
* Tested in acceptance with ASTM E96 Desicant method.
** Recommended Dry Film Thickness
Note: It is recommended that the users contact the manufacturer for fore information.
STRUCTURAL BARRIERS
Often prefabricated to exact dimensions required and ready to install, these are rigid sheets of reinforced plastic, galvanized, aluminium or stainless steel jacketing - flat, corrugated or embossed.
MEMBRANE BARRIERS
Metal foils, laminated foils and treated papers, plastic films and sheets, and coated felts and paper - these are either part of the insulation as supplied or can be supplied separately.
COATING BARRIERS
In fluid form as a paint or mastic (or semi-fluid of the hot-melt variety) the material can be asphaltic, resinous or polymeric. These provide a seamless coating but require time to dry and are normally reinforced with a membrane sandwiched between layers.
Special attention must be given to vapour sealing of protrusions, joints or any other discontinuities such as glands, local to valve spindles or mechanical drives, etc. Refer to the following tables
PROTECTION OF INSULATION
Protection of the insulation may consist of metal cladding or a coating system.
Metal and non-metallic finishes should generally be as per the insulation guideline for hot insulation. However, care should be taken where piping and equipment is being clad; the cladding should be manufactured and installed so as to prevent the vapour barrier being punctured. Cushioning material applied between screws or rivets and vapour barrier, or other suitable means, would be a normal practice.
The Benefits of using Aerolite.
Aerolite is made from pure spun glass, bonded with an inert thermo-setting resin to form a strong, resilient, easy-to-handle blanket.
Because Aerolite forms a highly efficient thermal barrier, it excludes solar heat gain in summer and retains heat generated within a building in winter. It reduces heat flow by up to 87% and can lower the temperature in summer by up to 5 degrees C.
What's more, Aerolite's insulation efficiency is unaffected by its orientation to, or the direction of, heat flow.
Aerolite is the only insulation in South Africa that does not burn!
Aerolite is the only insulation which cannot burn, as it is made from fibreglass. This means it is the safest insulation you can buy.
Aerolite beats the winter blues!
Aerolite's effective insulation keeps you comfortable and warm during the chilly months because it retains the heat generated in your home.
When the going gets hot, Aerolite takes the heat!
Those sweltering hot summer days aren't a s problem when your house has Aerolite because it helps keep the heat out, leaving your home much cooler. And by keeping a more constant temperature all year round, it actually helps keep the kids healthy!
Energy savings puts money in your pocket!
Aerolite actually pays for itself in the long run, because you save money on electricity and other bills.
Aerolite's soundproofing qualities mean less noise!
Aerolite's insulating properties reduce outside sound transmission leaving your home much quieter.
A 30-year guarantee means you don't have to worry about a thing.
Aerolite is lightweight, won't rot and doesn't provide sustenance for vermin so, once you've had it installed, you just forget about it.
For more information on the Aerolite brand, click here
Vedder & Moffat specialize in the Supply and Application of Thermal Insulation to :-
Steam Pipes - Vessels - Boilers - Ducting - Chilled Water Pipes - Product Lines