Taking the hiss out of factories
October 1st 2009

Escaping compressed air is easily remedied.Colin Chapman of Henkel,maker of Loctite products,explains how threadsealers work under pressure to save this unnecessary expense

Calculations have revealed that compressed air can cost more than ten times the equivalent quantity of electrical energy – so with that kind of price tag, this commodity shouldn't be wasted. Yet the hissing of escaping compressed air is a familiar sound in many factories and workshops. And that noise originating from threaded pipe joints is costing someone a great deal of money. It's good to know that for the price of a bottle of sealant or a container of sealing cord, those costs can be eliminated.

Why do you have a leak? Interestingly, it is some of the actual sealing 'solutions' that are responsible for leaks. For instance, among the long established options of sealing spiral leak paths of threaded joints is the use of pastes made from oil and fillers.

And while it is a fact they present the benefit of lubricating joints, they can squeeze out when subjected to high pressure – rendering them ineffective. Further, they don't work too well on parallel threads. In short, the possibility for problems.

Like pastes, solvent-drying pipe compounds provide useful lubrication, however they can shrink during the cure – action that can quickly produce a leak path.

A third traditional method of sealing involves the use of PTFE tape. Again, this medium acts as a lubricant, but this 'quality' can result in overtightening, adding stress or even causing breakage. Beyond that, if correct alignment of the parts is not achieved as they are tightened, dismantling will be necessary and the exercise repeated.

This operation could result in the tape shredding – with the possibility that control valves becoming contaminated. In addition, tape offers poor resistance to vibration.

Anaerobics are the answer With these drawbacks to traditional sealing practices in mind, many maintenance engineers are discovering a couple of alternatives that are proving to be far more reliable – and easier to use.

The first of those options is anaerobic threadsealing products. Here, the sealing compound is applied to the threads to be joined. It then cures between the metal surfaces in the absence of air, and hardens to a tough plastic that locks the joint in place.

In effect, both parts of the mating joint become as one as the cure is completed. So secure is this joint that it will withstand the most forceful vibration.

Despite this protection, the joint can be disassembled using normal hand tools.

That's because the filled threads stop the ingress of moisture or corrosive chemicals – reducing and, in many cases, eliminating the possibility of joint seizure.

Conclusive results To test the instant sealing capability of an adhesive, Henkel carried out a laboratory trial in which a 1/4" BSP taper to parallel fitting was treated with one of its most popular grades of threadsealer – Loctite 577.

The fitting was immediately plunged into water and tested for five minutes under a pneumatic pressure of 29 bar. No leak was found. The assembly was then allowed to cure fully under ambient conditions, and retested. Again, no leaks appeared. In a further test, hydraulic pressures in excess of 1200 bar were generated – and still no leaks.

Further benefits Under any circumstances, assembling stainless steel to stainless steel threaded fittings means that galling can occur.

However, threadsealers such as Loctite 577 incorporate a lubricant that removes this galling and significantly reduces the chance of damage. A further benefit is that all sizes of threads and fittings can be sealed using the same product.

It goes without saying that anaerobic threadsealers are effective on more than just systems carrying compressed air. Once cured, these sealants resist gases, water and most industrial liquids. This particular threadsealing adhesive will withstand temperatures in a range -50°C to +125°C.

Beyond all those advantages, anaerobic threadsealers also provide a threadlocking action that prevents the seal from working loose as a result of shock or vibration.

Confidence in cords The second alternative method of securing joints involves the use of sealing cords.

Indeed, this provides a ready transition from some of the previous processes of sealing to the technology of today. Sealing cords outdate pastes, hemp and tapes, while, at the same time, creating a clean and instant means of securing threads. The thin cord is simply wrapped around the male threads for the recommended number of turns and then cut using the sharp in-built cutter on the container. Hard to believe, maybe, but that's all that is needed.

If the fittings don't align, then the joint can be backed off without fear of leakage. These sealing cords can be used on cast iron, steel, brass, copper, chrome, nickel-plated and galvanised surfaces, stainless steel and plastic.

Further, the design of the yarn is such that it will not shred or tear and cause blockage. Of course, both sealing cords and anaerobic products can be used just as easily for both the initial installation and the repair of pipework.

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