Installing elastomeric foam tubing

Decide which tube type suits the job. For pipe sizes below 89 mm, tube is used rather than sheet material. Choose between closed tube (slit with a knife and glued with contact adhesive), tube with a factory-applied adhesive strip with protective paper film, or a combination of both — possibly supplemented with a 3 mm Armaflex tape over the joint.

Tape alone does not constitute an approved joint.

You will need: a cutting board with preset angles (including 11.25°, 15°, 22.5°, 45° and 67.5°), a caliper for measuring the pipe diameter, a sharp fillet knife for long, even cuts, a short-bristled brush for applying adhesive, and a set of hole punches in the relevant sizes (e.g. 28 mm) for punching holes for tees. Put on respiratory protection with a valid cold filter and safety glasses before working with adhesive and thinner.

Make the longitudinal cut with the fillet knife without cutting into the surface underneath. If the tube is slightly oval, the cut must be placed on the flat side — not in the small curve. If the cut is made in the curve, the tube will gape at the joint when it returns to its round shape, leaving an uncovered area. If, on the other hand, you cut on the flat side, the layers close from the bottom up and the joint becomes tight.

Always place the longitudinal cut on the flat side of an oval hose, never in the small curve.

Choose the bend type according to the radius of the pipe bend: 11.25°, 15°, 22.5° or 45°. The larger the angle per cut, the fewer the segments and the wider the throat. Measure the small radius (from the middle of the weld bend in to the pipe), subtract the insulation thickness, and multiply the new radius by π. Divide by the number of cuts for the bend type (e.g. 8 for 11.25°, 6 for 15°, 4 for 22.5°), and you get the width of the throat. The bend must always consist of two end pieces plus the calculated number of middle segments.

With threaded fittings, the tube material is taken right up to the edge of the thread before the bend is fitted. Use a suitable bend type — with a very small throat radius, a 45° bend (consisting of only a start and end segment) will often be more practical than a 22.5° bend, because the throat at fittings is too small to accommodate the larger number of segments.

Use the cutting board and cut the T-piece with a 45° cut at the bottom. Glue it together, then cut the opening for the T-piece by running the knife through the material. Always measure the T-piece's length from the centre of the main pipe out to the end. Cut the T-piece slightly longer than the calculated dimension, as the tube material can work itself shorter during fitting.

For an inclined 45° tee, the cutting template must have one cut at 67.5° and one at 22.5°. The four cuts (67.5° + 67.5° + 22.5° + 22.5°) add up to 180°, which is the requirement for a correct tee. Measure the short and the long outer length of the branch material on the fully installed insulation — never on the bare pipe — and transfer the measurements to the tube before you cut.

To avoid cutting unnecessarily into the main pipe's insulation, you can instead punch a hole with the correct pipe size (e.g. 28 mm). Measure the short (A) and the long (B) outer length on the fitted insulation. Mark A and B on the branch material, draw the outline and make a precise round cut that fits down into the hole in the main pipe's insulation.

A symmetrical reducer is cut with two cuts that divide around the same centre line. A one-sided reducer (straight on one side) is made with one cut. Find the width of the reducer cut by measuring and calculating the difference between the outer circumferences of the two tubes — use the caliper to measure the actual outer dimensions of the fitted insulation.

Make only a small hole in the foil seal on the adhesive tin so the brush can be pushed through, and put the lid back on between each brushstroke to minimise evaporation. Apply adhesive to both surfaces with strokes that only deposit adhesive on the inside of the tube's cut — never on the visible outside. Let the adhesive surfaces dry until fingernail-dry (the contact adhesive test: the nail does not stick and the surface is not tacky), and then press the surfaces together. At high temperature and humidity the adhesive dries faster — adjust your working pace.

Ordinary elastomeric foam is not UV-resistant and must not be used outdoors without protection. Either choose an approved acrylic paint (e.g. from Amazel): apply the first coat immediately after the insulation has been fitted and the second coat before 7 days have passed. Alternatively, fit sheet-metal cladding, possibly with a thin layer of mineral wool. Be aware that cladding moves the dew point out into the insulation, which can cause condensation problems with anti-condensation insulation.

Before the tubing is fitted, the pipe surface must be protected against corrosion with suitable paint — also on stainless steel pipes. The air inside the insulation at the time of installation contains more moisture than the air the pipe will contain in operation at lower temperatures. The excess moisture will condense inside the insulation and can cause corrosion over time if the pipe surface has not been properly treated.