Fittings and Flanges in Hydraulic System Design

When a hydraulic system is designed, it still needs connection points that can be opened for service. Pumps, valves, cylinders, filters, hoses, tubing, and instruments may all need to be removed, inspected, or replaced during the life of the equipment. That is why most hydraulic layouts include removable fittings or flanges rather than treating the whole system as one permanent pipe assembly.

The design decision is not only where to put those connections. It is also which connection style fits the pressure, temperature, vibration, tube wall, port style, and maintenance access around that part of the machine.

Pipe threads and leak risk

All-metal pipe-thread connections can leak when threads are over-tightened, distorted, cracked, or exposed to temperature swings and vibration. Pipe threads may still be correct when the port and service conditions are intended for that style, but they should not be used as the default answer for every hydraulic connection. For tapered pipe-thread layouts, HGW's NPT pipe fittings category is the relevant product family to check.

JIC flare fittings

37 degree JIC fittings are common in hydraulic systems because the seal is made at the flare seat while the threads pull the joint together. They are compact, widely available, economical, and useful where thin to medium-wall tubing can be flared correctly. Thick-wall tubing is harder to flare, so the tube choice affects whether this connection style is practical.

JIC flare connections are often chosen because they:

• save space compared with some larger connection styles
• adapt readily to other fitting families when the correct adapter is used
• are easy to obtain for maintenance and repair work
• keep the connection serviceable without making the line permanent

Where flanges fit

Flanges are useful where pipe size, flow, port design, pressure, or service access makes a small threaded connection less practical. A bolted flange connection can be opened for maintenance and can support larger ports or heavier assemblies. For systems that use this style, HGW's flange adapters and plugs category is the natural starting point.

The same basic rule applies to fittings and flanges: choose a connection that can be serviced later while still matching the pressure, temperature, vibration, routing, and component layout of the hydraulic system.