Question 1

Is thermal bedding sand washed?

Accepted Answer

No. Its fines are retained deliberately. A well-graded sand with fines packs densely with few air voids, which is what gives it low thermal resistivity. Washing removes the fines and increases resistivity.

Question 2

Why does thermal resistivity matter for buried cables?

Accepted Answer

A cable generates heat in service. If the material around it resists heat flow, the conductor runs hotter and the cable must be derated. Low-resistivity bedding lets the cable operate closer to its full current rating.

Question 3

Can ordinary washed sand be used as cable bedding?

Accepted Answer

Washed sand is suitable for mechanical protection of a cable but has higher thermal resistivity than a well-graded thermal sand, because washing removes the fines that allow dense compaction. Where a thermal specification applies, a thermal bedding sand should be used.

Question 4

What thermal resistivity does MRP thermal bedding sand achieve?

Accepted Answer

Thermal resistivity is established by laboratory testing of the material at the density and moisture condition specified for the project. Contact us with the specification to discuss.

Question 5

Where is thermal bedding sand used?

Accepted Answer

Underground HV and MV cable trenches, conduit bedding, substations and switchyards, wind and solar farm grid connections, data centre power reticulation, and transmission and distribution networks.

Question 6

How should it be placed?

Accepted Answer

In layers around the cable and compacted to the percentage of maximum dry density required by the project specification, so that the bed is dense and thermally stable.

Question 7

What is the difference between thermal bedding sand and pipe bedding sand?

Accepted Answer

Pipe bedding sand is chosen for mechanical support and drainage and is usually washed. Thermal bedding sand is chosen for heat conduction and is unwashed and well graded so it compacts densely. They are not interchangeable where a thermal specification applies.

Question 8

Does moisture affect thermal resistivity?

Accepted Answer

Yes. Moist sand conducts heat better than dry sand, which is why specifications state resistivity at a dry or defined moisture condition as the conservative case. Dense compaction is what keeps resistivity low as the ground dries.

Question 9

How is thermal sand ordered?

Accepted Answer

By tonnage, with the project specification for thermal resistivity and compaction. Contact us with the specification and delivery location.

Thermal Bedding Sands

About this product

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Specifications