Connectors might not always receive the attention they deserve. Often times the specification of fittings and tubing is secondary to the attention paid to larger components. Design engineers may not anticipate system leaks. Even if pneumatic fittings and tubing are the last components to be specified in typical food and beverage packaging equipment, they still merit close consideration. Improperly specified connectors contribute to early component deterioration causing leaky connections and even pressure drop. Properly specified fittings and tubing will help to ensure that food and beverage packaging systems perform at levels end-users expect.
In the food and beverage industry, there are a number of packaging processes driven by pneumatic power carried through tubing and fittings that connect pneumatic valves, actuators and FRLs (filters, regulators, lubricators). The components may power any number of processes, such as the filling and sealing of bags of tortilla chips; the folding, filling and sealing of milk cartons; or the packaging of hamburgers and steaks. Regardless of the application, when pneumatic connections aren’t specified correctly, systems can end up with untimely air leaks and pressure drops.
To reduce the chance of leaks and flow restrictions, here are some tips for specifying, plumbing and routing pneumatic connections in food and beverage packaging builds:
While most pneumatically controlled food and beverage processes use push-to-connect fittings over other styles, such as compression and flare, push-to-connect fittings also come in different materials for specific reasons. There are higher-end FDA-compliant fittings, such as Parker’s Prestolok PLM electroless nickel-plated brass fittings and Prestolok PLS stainless steel fittings, made for applications where the fittings may come in contact with foods and beverages.
For processes where foods and beverages don’t come in contact with fittings, such as secondary packaging operations, OEMs can opt for more economical push-to-connect fittings, such as Prestolok PLP metal fittings and Prestolok PLP composite fittings.
Fitting material type becomes important for applications that receive high heat or caustic washdowns, which could quickly compromise fitting integrity depending on the material.
Say the fittings will be installed throughout a dairy filling application where they will receive frequent and potentially caustic washdowns. In this case, all-stainless steel fittings are made to withstand these harsh conditions and keep processes leak-free and running. That’s in contrast to a tortilla chip packaging process, where the fittings might come in contact with foods, but don’t receive frequent caustic washdowns. Here, OEMs might choose Parker’s FDA-compliant PLM fittings. General industrial-purpose fittings, meanwhile, are likely to fit the bill for fittings mounted on automated box folding machines erecting outer packaging containers.
Fittings come in many configurations that allow for effective routing of pneumatic connections. In many food packaging applications, OEMs mount valve manifolds and actuators on machines and then determine what fitting configurations will work best for connecting those ports. It is the last piece of the puzzle and where a design engineer decides to use, for example, an elbow fitting instead of straight or tee fitting. It’s all dependent on where the line is going to be installed in relation to the pneumatic components.
Routing questions also arise in situations calling for tubing to take a tight bend, leading machinery designers to weigh the benefits of using fittings instead of tubing to accommodate the turns. Often a complex decision, this can depend on the tubing material too, as using tubing with a high bend radius can allow for more turns, but also might put side-load on fittings.
If tubing is bent too close to the fitting, it could pull the tubing away from the fitting seal, creating the potential for a leak.
Another factor is the tubing diameter tolerance, or how much its outer diameter could vary from one manufacturing run to another. Tubing manufactured to a looser tolerance level could cause fit issues allowing fittings to leak or to blow off of tubing.
Parker tubing and fittings are tested and designed to work together. Parker Parflex tubing holds the tubing to a certain tolerance range, which helps in terms of fitting performance because tubing tolerance is so critical to working well with a push-to-connect fitting.
Customers should reference Parker’s Tubing Compatibility Chart (found in Parker Hannifin catalog 3501E) to be sure they choose the proper tubing for each fitting type.
Finally, another problem area is extra fitting connections installed where they don’t belong. Every fitting is a potential leak point, so if the number of connections can be reduced so to can the chance of leaks. Each fitting in a pneumatic circuit also adds a flow restriction, as compressed air is forced to move through another orifice, which can hamper motive power.
One of the more common issues is using multiple fittings in place of one or two, as a way to adapt one fitting or tube type to another. It can happen when the OEM or end-user doesn’t have the proper fitting shape or type on hand to adapt to a certain thread system or port size required by the valve or cylinder. While the adaptation may function, it can also restrict airflow and add the potential for leakage.
OEMs can avoid the problem entirely by choosing the appropriate adapter. Parker offers hundreds of tube fittings and adaptors made to join different tube sizes and thread types, such as NPT to BSPT, BSPP or metric. Rather than trying to build a makeshift adapter out of two or three pneumatic fittings, using a single adapter fitting allows technicians or engineers to make the connection in one step, preventing unnecessary flow restrictions and reducing the risk of leakage.
With these suggestions, many connector issues like adapting to different sizes or standards, or accommodating system designs, need not lead to system slowdowns. With the right pneumatic fittings, adaptors and tubing materials, OEMs and end-users will be equipped to keep airlines flowing.
To learn more about specifying these components, locate a distributor near you.
This article was contributed by John Duba and Michael Nick, product sales managers, Parker Hannifin's Fluid System Connectors Division.