Hydraulic Fittings and Filtration
JIC 37-degree Flare Leakage
[from the Inside Hydraulics Newsletter - August 12, 2003]
Flaretite
Flared connections have gained widespread acceptance due to their simplicity and low cost. However, the metal-to-metal seal of the flare means that a permanent, leak-free joint is not always achieved, particularly in the case of tube-end connections.
Leaking flare joints can be eliminated using a purpose-built seal developed by Flaretite. The Flaretite seal is a stainless steel stamping shaped like a JIC nose, with concentric ribs that contain pre-applied Loctite sealant. When tightened, the ribs crush between the two faces of the joint, eliminating any misalignment and surface imperfections. The combination of the crush on the ribs and the Loctite ensure that a leak-free joint is achieved.
Incorrect Torque
A common cause of leaks from flare joints is incorrect torque. Insufficient torque results in inadequate seat contact, while excessive torque can result in damage to the tube and fitting through cold working. The following is a simple method to ensure flare joints are correctly torqued:
#Finger tighten the nut until it bottoms on the seat. #Using a permanent marker, draw a line lengthwise across the nut and fitting. #Wrench tighten the nut until it has been rotated the number of hex flats listed in the following table:
| Tube Dash Size | Hex Flats |
| 4 | 2.5 |
| 5 | 2.5 |
| 6 | 2.0 |
| 8 | 2.0 |
| 10 | 1.5-2.0 |
| 12 | 1.0 |
| 16 | 0.75-1.0 |
| 20 | 0.75-1.0 |
| 24 | 0.5-0.75 |
Suction Filtration
A paragraph from the Sauer Danfoss Applications Manual, page 10:
The suction filter is placed in the circuit between the reservoir and the inlet to the charge pump as shown in Figure 4-3. A non-bypass filter is recommended with a filter contamination monitor. A vacuum guage, located nearest the charge pump inlet, is suggested. Inlet vacuums up tp 6 in Hg (0.8 bar absolute) are accepatble during normal system operation. An indicator set at 10 in Hg (0.7 bar absolute) is recommended for a fliter change. Vacuums on the order of 20 in Hg (0.3 bar absolute) are acceptable during cold start or intermittant conditions. Exceeding these values may result in charge pump cavitation, aerated fluid, and life reduction of the hydraulic components.
- Hydraulic Supermarket
- Hydraulic-Supply.com
- HydraulicHoseFittings.com
- FittingsAndAdapters.com
- Flow Ezy Filters
- Hydraulic Multiplier valve
- Surplus Center - yup
- Youngs Surplus - industrial air, electric, hydraulic, etc
- Northern Tool - tools, hydraulics and tractoring supplies
- MSC - more than a machine shop supply house MSC has TONS of tools, supplies, steel stock etc.
- Thread Sizes and Adapters Chart
- Free online spec calculators courtesy of Baum Hydraulics
- Sauer-Danfoss pumps etc
- US Army Field Manual FM 5-499 Hydraulics (available from Amazon.com)
- free-ed.net offers a Basic Hydraulics course based on the FM 5-499 Field Manual
Tags: Supplies