Conserving energy with Loctite threadsealing
THE hissing of escaping compressed air is a familiar sound in many factories and workshops. It’s easy to get accustomed to it, and tempting to regard it as inevitable. Compressed air is an essential and convenient resource; but it is also expensive to produce, and can cost over ten times the equivalent quantity of electrical energy - so it should never be wasted.
That hissing sound means that leakage, often from threaded pipe joints, is costing a great deal of money.
For example a 1mm diameter hole in a system at 7 bar will lose about 1.2 litres per second, costing £100 per year; even a 0.5mm hole incurs an annual cost of around £25. The potential cost for a typical factory with hundreds of pipe joints could be very high - but, for the price of a bottle of sealant, it can be avoided.
More and more maintenance engineers are using threadsealing adhesives to repair such leaks, and are finding that they are more reliable than the traditional methods of pipe sealing. Also, as new and greater demands are placed on maintenance engineers for more dependable systems, those same adhesives are being specified at the design stage of an increasing number of projects.
Bob Orme, a senior technology specialist at Henkel, confirms that threadsealing adhesives overcome many of the problems associated with traditional ways of pipe sealing: ‘PTFE tape, for instance, is effective, but it does present some problems. If the tape shreds there is a danger that control valves can become clogged, and that could prove disastrous. Tape is also not very good at resisting high levels of vibration, and it is sometimes necessary to over-tighten the joint in order to align elbows and fittings. Sealants do away with all these difficulties. Pastes can creep and shrink; and while cone fittings and O-rings are very effective, they are costly to machine and are susceptible to damage.’
Threadsealing adhesives are anaerobic, ie they harden between metal surfaces in the absence of air. The product is applied to the threads to be sealed, and as the mating parts are screwed together, air is excluded from the joint and the curing process begins. Because the adhesive hardens to a tough plastic, it also locks the joint in place and withstands vigorous vibration.
As a test of instant sealing ability, Henkel conducted a laboratory trial in which a 1/4in BSP taper-to-parallel fitting was coated with Loctite 577, a popular threadsealer. The fitting was immediately plunged into water and tested for five minutes under a pneumatic pressure of 29bar; no leak was observed. The assembly was then allowed to cure under ambient conditions, and retested - again, there were no leaks.
In another test there were no leaks under hydraulic pressures of over 1200 bar. Orme says that in assembling stainless steel-to-stainless steel threaded fittings, galling can occur - but that Loctite 577 has a built-in lubricant that eliminates this and minimises damage potential.
A further advantage of a liquid adhesive is that all sizes of threads and fittings can be sealed using the same product. When cured, Loctite 577 will withstand temperatures from -50/+125°C. Of course, anaerobic threadsealers can be used for more than just systems carrying compressed air. Once they are cured, they resist water, most industrial liquids and gases.
Easy maintenance, ‘Not only does the adhesive completely seal the thread, but it also provides controlled strength that allows the system to be easily dismantled for routine maintenance jobs’ says Orme. ‘In addition, the complete seal prevents corrosion migrating into the joint, again making dismantling, when required, very easy - and there is no damage to the threads in the process.’ Loctite produces many other threadsealing adhesives for specific applications including for use with potable water, or in radiation environments. In addition, there’s a threadsealing ‘stick’.
It looks like a Pritt stick (another Henkel product), but the adhesive is similar chemically to threadsealant available in a bottle and just as reliable. The stick is small enough to carry in a pocket, and its thick consistency means it will not drip when applied to vertical or overhanging threads. There’s plenty of noise in most workshops and factories without having to endure the unnecessary sound of escaping air.
But, says Orme: ‘if you’ll pardon the expression - there is a solution, and it lies in a bottle of adhesive threadsealant.'
Henkel Loctite
