Technical Notes

High Temperature Glovebags

High Temperature Glovebag Grayling
Therm-Equip Glovebag

As many of you will know, my connection to Glovebags goes back to the days of Bestobell, when they entered an agreement with a UK company to manufacture bags here in Australia. This wasn't a terribly successful venture due to the local manufacturing costs, limited market and a high royalty cost per bag

In the days of Bell Thermalag, this arrangement was cancelled and we started importing Glovebags from Grayling of Georgia, USA. This is an arrangement that I have continued to this day. Grayling offer a wider range of bags and the arrangement has proven far more succesful than the earlier arrangements. The Avail Glovebags, and decons have been very well received.

Grayling over the years have extensively added to their product range to meet market requirements. The QT range has a deeper neck, allowing for easier closing of the bags. These have now been added to our stocks locally.

Grayling have now also made available Therm-Equip High Temperature Application Glovebags.

The original GloveBags were developed to allow the removal of asbestos or mmmf insulation for pipes and services without the need for major isolation of surrounding areas. The Therm-Equip bags allow the removal of asbestos or mmmf insulation form pipes and services without shutting the service down, subject to temperature limitation.

The bags are supplied to suit three service ranges : 300°F/148°C, 400°F/204°C & 700°F/370°C.

The Therm-Equip bags are manufactured and imported against specific, non-cancellable orders and, although supplied at a cost premium against conventional Glovebags, the ability to remove insulation from in service lines will often make the choice of a Therm-Equip bag very economical. A "no-brainer", in fact.

Full details of these bags including product brochure & usage instructions can be downloaded from our web site in PDF format here.

Use of Rockwool Pipe Sections to Seal Pipe Penetrations at Firewalls

This is a matter which is the cause of much argument in the thermal insulation industry. The argument / disagreement centres around who is responsible to provide the fire seal where insulated pipes penetrate a firewall or slab.

A number of insulation contractors believe that their responsibility is limited to providing non-combustible insulation onto the pipe for the length of the pipe within the wall / slab and for a distance either side of the wall / slab. The provision of the fire / smoke seal to the gap between the non-combustible insulation and the wall / slab is then the responsibility of the FIRE PROTECTION CONTRACTOR.

As I said earlier this is the cause of much disagreement. The other arguable point is how far each side of the wall / slab the non-combustible insulation should continue.

We have added to our Rockwool data sheets (download) an opinion from CSIRO dated 30th July 2012 that details a system which will, if tested to AS1530.4-1990, provide a fire resistance rating of -/120/120 for a wall / slab penetration, providing the non-combustible material extends 250mm either side of the wall / slab.

Please note this system is limited to pipe sizes up to 203mm odp and that there may be other tested proprietary systems available that will meet the building code requirements.

N.B. this technical note is of a general nature and should not be relied on for specification purposes. Contractors, consultants and building owners should seek independent professional advice regarding any fire protection matter.

R-values of Pipe Insulation

This note is intended to clarify how the r-values for pipe insulation materials are determined.

The R-value of preformed pipe insulation can be calculated using the methods detailed in ASTM C335. There are overseas laboratories that can test to this standard, but I believe that this method is not available at any registered testing laboratory in Australia.

Here, all insulation materials are tested on a planar section of insulation of the same specification as that of the preformed pipe section. In other words, if your pipe sections are to be 125kg/M3 rockwool then the flat sheet must also be 125kg/M3 rockwool.

Once the k-factor of the material has been determined in the "planar mode", the k-factor, or factors if the material has been tested at multiple thicknesses, are used to determine the R-value of the pipe insulation.

The R-value of the pipe insulation is determined by using the formula detailed in AS/NZS 4859.1:2002 clause (new) "Alternative method for calculation of R-value for pipe insulation". It should be noted that the formula detailed in this clause (unless since corrected) is incorrect. The reference to log e should in fact be log n.

The R-value of pipe insulation utilising this formula, or if testing to ASTM C335, will always be higher than that of a flat sheet of identical construction.

This technical note is intended as a guide only and any information of a technical nature should be checked with a qualified engineer.

Off-gassing from Fibrous Insulation

We have had a number of queries recently over the fumes given off from both rockwool and fibreglass when exposed to "high" temperatures. Here is the explanation why this happens.

Fibreglass & rockwool blankets, slabs & sections all contain a resin binder. The amount of binder varies from product to product. Generally speaking, the more rigid the product, the more binder will be contained in the product. It does not matter which company produces the material, product for product, the amount of binder will be similar. The higher the operating temperature that the product is exposed to, the more burn-off of binder will occur. Burn-off of binder from rockwool commences when the insulation reaches a temperature around 300C. Burn-off of binder from fibreglass / glasswool occurs when the insulation reaches a temperature around 175C.

In outdoor applications, the fumes generated by burn-off of binder mostly go un-noted. However in indoor applications, the sudden appearance of smoke can cause a degree of panic, as recently happened on one project where rockwool blanket had been installed on a co-gen exhaust pipe in a Sydney CBD building. After much discussion, and temporary suspension of system commissioning, it was accepted by all concerned parties that this was a normal occurrence. Commissioning was recommenced and burn-off ceased after about four hours.

It is recommended that all contractor customers point out the likelihood of burn-off occurring to their customers prior to commissioning of systems. To minimise or eliminate this problem with rockwool products, either use a wired mat product (wired mat tends to have less binder) or use a needled product such our cal-sil-mag fibre which has no binder. One of our contractor customers advises that on exhaust systems located on multi-storey sites he silicone-seals all cladding joints from the generator to the riser so that gasses do not escape into the plant room. The emitted gasses are classed as "nuisance fumes" but can cause running eyes & shortage of breath, so please exercise caution particularly in enclosed areas.