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BS 5970:2012
29.2.7
BRITISH STANDARD
Insulating concrete
NOTE This type of material consists of an insulating aggregate bonded in situ with
either Portland cement or high alumina cement. The insulating aggregate can be an
expanded natural mineral or granular expanded clay brick.
29.2.7.1 For highly porous pre-fired brick aggregates, the aggregate should be
soaked in water for 12 hours and then quickly drained before being mixed with
the cement and the measured amount of water for use. Insulating concrete
should not be used where the impinging gas contains entrained solids due to
their abrasive action.
NOTE The chief use with pipes is to protect the metal from excessive temperature,
either as a lining for the conveyance of hot gas or over the outer surface when the
metal of the pipe is to be shielded from the impact of hot gas.
29.2.7.2 Linings for large pipes should be anchored by Y-studs or V-anchors
welded to the inner surface; for horizontal pipes, the upper curved surface
should have studs at a closer pitch than those over the lower surfaces. Externally
shielded pipes should have either plain or Y-type securing studs welded to the
surface. In both cases, the concrete should be reinforced additionally by
expanded metal or other metal mesh reinforcement secured to the studs at a
short distance from the surface to be shielded.
29.2.7.3 The concrete for lining pipes should be applied by hand trowelling,
spray-gun or, in certain specialized cases, by centrifugal spinning.
NOTE For exterior treatment the principal method is to apply the material by hand
trowel.
29.2.7.4 After application, the insulating concrete should be cured by
maintaining in a moist condition (e.g. by covering with wet sacks, spraying with
water) for 24 hours. The initial heating should be relatively slow (see
manufacturer’s instructions and also 29.3.9).
29.2.8
29.2.8.1
Pipes with trace heating
General
The following trace heating methods should be assessed and selected or rejected
accordingly:
29.2.8.2
a)
external pipe tracing, in which a small-bore heating pipe is placed close to
the main pipe;
b)
electrical tracing, in which an electrically heated tracing tape or cable is
wound around the outside of the pipe or clipped immediately below and in
contact with it;
c)
jacketing, in which the main pipe is fitted with a jacket through which
heating fluid is passed;
d)
lancing, in which a small-bore heating pipe is inserted inside the main pipe;
and
e)
extruded pipe that has its own integral heating pipe in its wall.
Application of insulation to pipework heated by external tracing pipe
Before application of insulation, the product pipe and tracer pipe should be
wrapped together with aluminium foil not less than 0.06 mm thick (see
Figure 31 and Figure 32).
NOTE 1 The principal mode of heat transfer between the external tracer pipe and
the heated pipe is by direct conduction.
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© The British Standards Institution 2012
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BRITISH STANDARD
BS 5970:2012
NOTE 2 The following methods may be used to increase the effectiveness of heat
transfer:
a)
maintaining a hot air space inside the insulation cover to increase the heat
transfer area;
b)
maintaining direct contact between the tracer pipe and the main pipe by wiring
or strapping at intervals; and
c)
using heat-conducting cement to increase the contact area between the tracer
and heated pipe.
When corrosive action between fluid and main pipe is liable to occur at local
hot spots, spacers of low conductivity should be fitted between tracer and
heated pipe to prevent direct contact between tracer and main pipe.
NOTE 3
This can decrease the effectiveness of heat transfer.
The tracer pipe itself should be looped out and jointed near the main pipe
flanges, e.g. by a compression fitting. The exposed length of tracer should be
insulated.
Leak testing should be satisfactorily completed before the application of thermal
insulation.
Figure 31
Typical method of insulating steam traced pipe
Key
1 Pipe section insulation
2 Main pipe
3 Aluminium foil >0.06 mm
4 Tracer
5 Finish as required
29.2.8.3
Electrical tracing
Electrical tracing should always be applied and insulated in accordance with the
tracing manufacturer’s instructions.
Mechanical damage should be avoided and the heater tape should be protected
from water or chemical spillage. Pre-formed insulation of the correct inner
diameter should be applied to fit over the tracing cable on the pipe. Where live
electric tracing cables are buried in the insulation, a warning notice should be
placed on the outside.
© The British Standards Institution 2012
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BS 5970:2012
BRITISH STANDARD
Compatibility of heat tracing material with the pipes should be ensured (refer to
Table 10 for further details of compatibility of materials).
Copper-sheathed insulated cable should not be installed in direct contact with
galvanized steel.
Figure 32
Typical method of insulating electrically traced pipe
a) End view – Section A
b) End view – Section B
Key
1 Insulation
2 Insulation grooved to accept tracers
3 Insulation (full thickness top half only)
4 Tracer lines
5 Void bottom half (may be filled with blanket insulation)
29.2.8.4
Application of insulation to pipework heated by jacketing, lancing or
integral heating
These systems require no special technique and should be insulated as normal
pipework. Leak testing should be satisfactorily completed before the application
of thermal insulation.
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