Adhesives on the right track
August 1st 2009

Irish Rail has switched to Loctite for many of its adhesive tasks

Established nearly 160 years ago, the Inchicore Works, just outside of Dublin, is the headquarters for Mechanical Engineering and Rolling Stock maintenance for Iarnród Éireann – Irish Rail.

The site – with an area of 73 acres – is the largest engineering complex of its kind in Ireland.

Facilities on site at Inchicore include electro pneumatic lifting equipment, high tech CNC machines, under floor wheel reprofiling lathes, and paint shops.

The Mechanical Engineering department is responsible for the maintenance of rolling stock, including the overhaul and repair of diesel locomotives, diesel and electric multiple units, carriages, generator vans and freight wagons. It also manufactures rolling stock subassemblies and carries out a wide range of other servicing-related functions.

It is also responsible for many safety management activities associated with running the railway. And one of the most important safety areas involves the air braking systems on carriages. Obviously, it is crucial that any failure on such components be avoided.

To overcome any difficulties, the workshops have changed to using Loctite 572 pipe sealing adhesive for this all-important task. This sealant is recommended for all coarse metal threads where a slow cure is required for adjusting the alignment of valves and fittings. It can be used on threads up to 80mm and has a temperature resistance of +150°C.

Since engineers started to apply the adhesive to the adapters that are inserted into the castings of the brake cylinders repair time has improved immensely. The pressures in the systems vary from 3.5 to 7 Bar – but the pipe sealant can handle them all.

Loctite products are also used when the GM diesel powerplants which are used to drive locomotives are brought to Inchicore for overhaul. One of the most time consuming and difficult jobs is the removal of old gaskets which have become baked on to the face of the flanges they seal. To reduce time and labour, the company has switched to using Loctite 7200 Gasket Remover. This is spray applied and removes cured gasket sealants and traditional gaskets from most types of surfaces in just 10 to 15 minutes.

Engineers at Irish Rail tested the product and found it so effective that all engine faces being stripped are now coated with 7200.

They report that it replaces the very tedious job of scrapping and certainly saves a great deal of time and elbow grease.

Once old gaskets are removed, Loctite 574 Multi-gasket is used to seal the two flange faces on the coolant fan pump. This liquid gasket eliminates the need for a conventional paper type and being an anaerobic adhesive only cures when the two surfaces are brought into close contact and the air is removed from the joint.

The same product is used for the axle box bearing – a crucial part of the under carriage running gear. These bearings keep the wheels running – so it is vital that they remain well lubricated and free from any contaminants.

To achieve this result, the engineers in Carriage Shop II use the adhesive on the back plate to provide an air-tight seal around the coupling flange.

Another anaerobic is used on governor servos on the GM engine power delivery. In the past, locomotive drivers had noticed that the revolutions of the engines were not responding in tandem to the control inputs.

The fault was quickly traced to the governor units that were vibrating out of position and, as a result, were changing the predetermined settings.

The problem had been occurring on a fairly regular basis, and to make matters worse, the problem was happening in an oil area, so a solution to the difficulty was needed that would work in such an environment.

The answer was found in Loctite 243 threadlocking adhesive. By applying this medium strength adhesive to the threads, the problem was not only cured, but it also ensured that the servo units could be easily disassembled with normal hand tools for serving. Since the engineers switched to Loctite, there have had no problems.

Other applications in the wider rail industry include the bonding of silicone rubber which is a requirement for low smoke and toxicity regulations, the bonding of aluminium extrusions and panels to eliminate visible fasteners, the securing of fish plates to rails for insulated joints, sealing of hydraulic and vacuum suction pipes, bolt locking on switches and crossings, locking sliding door fittings and providing tamperproof protection on various vital pieces of signalling equipment.

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