This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC’s registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726. Hydraulic oil leaks are often considered to be an inherent characteristic of hydraulic machines. While this may have been true 30 years ago, advances in sealing technology and the development of reliable connection systems means that today, leak-free hydraulic plumbing is readily achievable.Reliable Connections Leak-free reliability begins at the design stage, when the type of hydraulic fitting is selected for port, tube-end and hose-end connections. Ports – Connectors that incorporate an elastomeric seal such as UN O-ring, BSPP and SAE 4-bolt flange offer the highest seal reliability. NPT and BSPT are the least reliable type of connector for high-pressure hydraulic systems because the tapered thread itself provides a leak path. The threads are deformed when tightened and as a result, any subsequent loosening or tightening increases the potential for leaks. In existing systems, tapered thread connections should be replaced with UN O-ring or BSPP ...