Efficient sealing systems in fluid power applications

26 September, 2017

Even the smallest of leaks in hydraulic and pneumatic systems can cause appalling damage, so adequate protection against this potential problem is a top priority for fluid technology manufacturers. Here, high-performance adhesives and sealants are the key to success, offering a huge boost to efficiency and cost structure in the production of hydraulic and pneumatic components such as pumps, compressors, cylinders and valves.

Be it for thread-locking, thread-sealing, structural adhesion, retaining, cleaning or metal pre-treatment applications, fluid technology OEMs are able to access a broad plethora of solutions.

For instance, 100% leakage safety can be provided through high-performance anaerobic thread-locking, thread-sealing, retaining and gasketing. Similarly, lower cost is evidenced simply by comparing inexpensive liquid thread-lockers with mechanical fasteners, and liquid gaskets with O-rings. Another clear market need is for lighter and therefore more energy-efficient systems, where the use of structural adhesives can replace welds and deliver lightweight designs.

The benefits of such products in hydraulic and pneumatic applications are wide-ranging, and include not just locking and sealing functions, but compensation for relative movement and impact loads, corrosion protection, increased load transfer, structural integrity and uniform stress distribution.

Bonding and sealing also offers lower inventory versus mechanical fasteners and enhanced design freedom, while the potential for fully automatic dispensing makes for cost effective and fast production.

To provide an application example, consider a hydraulic pump. Here, can be found a number of thread-locking tasks on the centring and flange bolts (into the housing), as well as the use of retaining compounds for keyway to shaft and inner bearing ring to shaft applications. Fluid power OEMs can also benefit from the use of liquid gasketing on the rear flange to housing joint, bonding the radial shaft seal into the housing and thread-sealing of the outlet/inlet connections and plugs.

More potential applications

A hydraulic cylinder has perhaps even more potential applications for thread-sealing (oil inlet/outlet connections, barrel to cap end), retaining (oil impregnated bronze bushes), thread-locking (ball head to rod end, piston to piston rod, cap end head, rod end head), bonding (identification plate) and gasketing (cap end head, rod end head). There also exists the potential to take advantage of metal pre-treatment solutions for the rod end head, cap end head and rear spherical housing.

Further application examples include valve blocks, lock valves, flow control valves, directional valves, pneumatic screw compressors, hose connectors, sensors, oil filters, air dryers, water/oil drains, pressure vessels and pipes, to list but a few.

Among Henkel’s advanced product solutions are retaining compounds, which find favour in fluid technology applications for a number of reasons. For instance, they offer high load transfer and prevent fretting, corrosion and micro-movement. They are also vibration and impact resistant, and give the designer the opportunity to eliminate mechanical fasteners (thus saving costs), and use slip fits rather than interference fits.

An example of the benefits available can be seen when retaining a bearing into a typical housing found on hydraulic pumps and compressors. Here, the use of Loctite 603 can eliminate the need for a press fit, which sometimes lead to housing cracks and gearbox damage. As a result, it is possible to relax machining tolerances and deliver reliable lifetime operation.

When it comes to liquid gasketing, the advantages over conventional solid gaskets are plentiful. For instance, there is no gasket relaxation and creep, and no surface irregularities to worry about. In addition, there is no gasket displacement, and no flange bowing or deformation. Liquid gasketing provides 100% metal-to-metal contact, ensuring no leakage.

Cost reduction

In a comparison between O-rings and liquid gasketing, the cost reduction per unit (joining flanges in electric motors) is estimated at €6.80 when considering all machining, assembly and material costs. At a typical OEM producing 50,000 electric motors a year, this amounts to an impressive annual saving of €340,000.

In a case example, the use of Loctite 5188 replaced O-rings on a rear cover to pump housing application in Germany. The liquid gasket successfully withstood operational loads without leaks over the product’s lifetime and delivered numerous cost savings for the customer, including reductions in machining, O-ring inventory and assembly.

Thread-lockers are also proving increasingly popular in fluid technology applications. These adhesives fill all voids in a thread to prevent relative movement and loosening through vibration. They lock and seal at the same time, and prevent corrosion.

The use of Loctite 243 thread-locker on a family of quick connect couplings produced in Sweden helped lock and seal the coupling thread with maximum reliability, while still allowing engineers to open the coupling for service when required.

Dedicated thread-sealers provide a seal against fluids that are aggressive or supplied at high pressure. In a case example concerning hydraulic fittings, Loctite 577 came to the rescue of an injection moulding equipment manufacturer in Taiwan that was experiencing leaks as a result of using PTFE tape. A course thread-sealer was required to seal oil pressures of up to 10,000 psi (690 bar). With Loctite 577, a positive seal was obtained to prevent loosening through heat and/or vibration.

As well as adhesion and sealing, Henkel also offers solutions for cleaning, protecting and dosing in fluid technology. Highly-effective water-based and solvent-based Loctite cleaners ensure oils, greases, liquid lubricants and other impairing residues can be removed reliably before adhesives and sealants are applied.

Metal pre-treatment and conversion coating are just as important as thorough cleaning. The functional coatings under Henkel's Bonderite brand range increase corrosion resistance and help to make production processes more efficient and cost-effective.

In conclusion, be it more reliable, cleaner, more energy-efficient, quieter or less costly systems, Henkel’s portfolio allows fluid technology manufacturers to cater effectively to the growing requirements of the market.

www.loctite.co.uk