Composite DOT-certified push-to-connect fittings are manufactured with a polymer body and brass screw threads and holding mechanisms. They utilize a collet to grip tubing, plus an elastomeric sealing mechanism to complete the tube end seal, allowing for a relatively foolproof assembly with no additional tools other than a tube cutter.
Like their brass counterpart, Prestomatic (PMT), composite PTC fittings do not rust or corrode. The internal push-to-connect sealing mechanism affords a strong and dependable seal robust enough to meet all DOT parameters and to withstand high and low-temperature extremes.
Composite fittings are particularly notable for their lightweight and durable construction, which features the same sharp biting edge as Parker’s Prestomatic fittings. What’s more, the weight benefits provided by composite push-to-connect fittings over brass fittings are significant enough to affect fuel efficiency and payload potential.
Composite push-to-connect fittings weigh about 43% less than brass push-to-connect fittings. With approximately 60 to 100 DOT tube fittings used per truck, that equates to a weight savings of about seven to nine pounds per vehicle! When you consider that some fleets number in the thousands, the potential benefits of composite push-to-connect fittings are substantial and can be passed along to end users.
One major benefit of PTC technology is the time savings in assembly. Attached to tubing with a simple push, these fittings may reduce assembly time by as much as 90 percent over compression style fittings, averaging four seconds per connection. That means an assembler who used to assemble 90 compression fittings in one hour may be able to assemble as many as 900 connections with push-to-connect fittings. This also means one worker can potentially complete in one hour, the same number of fitting connections it would have taken 10 workers to complete.
Considering an hourly wage of about $25, the labor cost to assemble each compression fitting connection is around $0.27, compared with just under $0.03 for each push-to-connect connection. At that rate, by switching from compression fittings to push-to-connect fittings, a manufacturer could potentially reduce its assembly labor costs from $250 per hour to less than $50. The financial benefits are compounded when you consider that with faster assembly processes, OEMs may also be able to produce more vehicles per hour with push-to-connect fittings.
Since push-to-connect fittings don’t require manual assembly or counting turns of the wrench, truck and trailer OEMs may be able to increase the consistency of the quality of their assemblies. Another time-saving benefit of push-to-connect fittings is that they can be supplied with color coding on the tube ends of the fittings, helping to specify which sections of the air brake system the fittings are to be installed. This not only adds further time savings by categorizing fitting connections but also helps to prevent installation errors and rework.
They also add greater customization potential for truck OEMs, since they allow for the creation of uniquely shaped bodies produced by injection molding processes. With longer lead times and upfront tooling costs required, custom-made composite fittings make sense when higher quantities of the custom fittings are required. However, with proper mold design, suppliers may be able to offer jump-sized versions of a part at a fraction of the cost and lead time required for the original component.
Although the unit cost of composite push-to-connect fittings is higher than that of compression fittings, most truck OEMs find the significant labor savings and weight reduction of this product more than make up for higher unit costs. And, when installed properly, DOT-rated push-to-connect fittings are just as reliable as compression style fittings in virtually all applications.
Article contributed by Samantha Smith, marketing services manager, Fluid System Connectors Division.