Fittings And Fittings Assembly Instructions
- HMK
- Fittings And Fittings Assembly Instructions
O-Ring Face Seal Fittings
1. O-Ring Face Seal Fittings Instructions
1.1 The fitting has two types. The first type consists of a body,an O-Ring, a nut and the weld tube.The weld tube isbrazed with the system steel tube, see Fig.1.The second type consists of a body, an O-Ring,a nut and a sleeve.As shown in Fig.2.the tube is flanged to 90°.When used as Fig.1.the quality of weld is very important.
Fif. 1
Fif. 2
1.2 O-Ring face seal fittings are suit for high pressure system.Id the hardnessof O-Ring is N90.the sealing will better.and be good for preveting leakage.
1.3 The O-Ring face seal fitting has two connected thread: metric thread and ORFS thread.
1.4 As shown in Fig.3,Fig.4 and Fig.5, the O-Ring seal groove has three types. The advantage of type Fig.3. it is very convenience for installation, when put the groove adown O-Ring could be held in the groove and not drop; The O-Ring could not enter the hydraulic system when the pressure is negative. The type Fig.4 has only the later adavantage of the type Fig. 3. The tybe Fig. 5 has no above adavantage.
Fig. 3 Fig. 4 Fig. 5
1.5 For metric thread O-Ring groove JB standard is type Fing. 5, but we suggest that the type Fig. 3 should be chosen and make a annotation when order. If no annotation we produce as type Fig. 5 general. For ORFS O-Ring groove, we produce as type Fig. 3 only.
2. O-Ring Face Seal Fittings Assembly Instructions
2.1 Assembly
a) As shown in Fig. 1, the tube end is cut squarly(within±1°) before assemblied, deburr the O. D. and I. D. of the tube, remove all oil and oxide, weld after put the nut. As shown in Fig. 2, the tube is flanged to 90°with special equipment after cut, diameter D should fall between diameter D1 and D2, see Fig. 6.
Fig. 6
b) The fitting body should be installed O-Ring firstly.
c) As shown in Fig. 1 or Fig. 2, place tube assembly against the fitting body so that the face of the weld tube(or flanged steel tube) comes in full contact with the O-Ring. Tighten the nut onto the fitting body by hand .then tighten it to the recommended torque with a torque wrench.If torque wrenches are not available, tighen 1/4 to 1/2 turn with general wrench .
2.2 Reassembly
Because the sealing surf aces flat and perpendicular to the installtion force, the O-Ring may be distorted duri ng assembly. The O-Ring should be in spected at each disassembly and replaced when necessary.
2.3 Leakage reason
a) The O-Ring is installed in the face seal groove improperly.
b) The O-Ring is damaged.
c) The sealing surface, the weld tube or the flange are not flat, or have another fault affecting sealing.
d) The flange is too large or too small that the O-Ring can’t be compressed.
e) The O-Ring material is not suit for working temperature.
g) The O-Ring hardness is not enough.
h) The connected nut is loosen.
Bite Type Tube Fittings
1. Bite Type Tube Fittings Instructions
1.1 Bite tybe fitting consists of three parts: body, cutting ring and nut .When tightening nut, cutting ring is driven forward on the tube then bites the tube with the adge of cutting ring, this is how sealing is achieved and results in internal ridge inside the tube. see Fig. 7 .
Fig. 7
1.2 The tube connection side of fitting is manufactured in accordance with standard: DIN 3861
1.3 In general, body and nuts’ surface is plated zinc. Bite type fitting can be used in system with Max 63 MPa. The connection tube O. D. is Max. 42mm.
2. Bite Type Tube Fittings Assembly Instructions
2.1 Assembly
a) Cut the tube at right angle and de-burr inside and outside of tube end .Minimum straight length of tube from the starting point of tube bend to the tube bend to the tube end may be 3 times height of the nut.
b) Set a nut and cutting ring on the tube .Make sure the cutting ring and the nut are facing the fitting.
c) Lubricate the pre-assembly fitting body threads and cutting ring .insert tu be end into fitting body until it is firmly seated on bottom (fitting shoulder) and hand-tighten the nut.
d) Tighten nut until ferrule grips tube which is felt by a noticeab le increase in torque (in crease in force).
e) Tighten nut 1/2 of a turn after increase in force.
f) Disassembly the pre-assembly fitting body .Check penetration of cutting edge . A visible ring of material should fill the space in front of the profile ring end face. Profile ring may turn on tube .bur should not be capble of axial displacement.
g) Lubricate the fitting body to be subsequently installed .Tighten nut untila noticeable increase in force is required. Tighten nut by 1/2 of a turn beyond this point for final assembly.
2.2 Reassembly
ensure this, parts must be clean and free of defects.
a) Insert the tube into fitting body untilcutting ring seats firmly in the fitting and hand-tighten the nut.
b) Tighten the nut with a wrench by holding the fitting body with a backup wrench until a sharp rise in torque is felt.Further tighten the nut 1/4 to 1/2 turn.
2.3 Checking up the bite condition
All bite type fitting must be disassembled prior to service to check up if small ridge inside the tube is completely formed around front edge of cutting ring .Otherwise tighten slightly more to have it .Cutting ring may rotate on the tube that doesn’t mean wrong installation .The cutting ring shall be refitted once the nut is retightened.
2.4 Leakage reason
a) When the tube is not fully bottomed
b) When the nut is nut tightened enough
c) When the tube is of scratches or oval
d) When the tube is extremely hard.
Flared Tube Fittings
1. Flared Tube Fittings Instructions
1.1 As shown in Fig . 8, the fitting consists of three pieces: the body, sleeve and nut. The tube end is flared at a 37° angleand held between the fitting nose and the sleeve with the nut, providing a metal to metal seal between the fitting nose and the flare. The advantage of sleeve is reducing vibration and fatigue of tube, the stee; tube will not turn when tighten the nut.
Fig . 8
1.2 The flared tube fitting has two connected thread: metric thread and JIC thread
1.3 it is easy to assemble without weld. It is especially suited for low and medium pressure systems. As metal to metal seal, it allows wide operting temperature range.
2. Flared Tube Fittings Assembly Insturctions
2.1 Assembly
a) Cut tube reasonably square (within±1°),deburr the I. D. of the tube, remove the dirt. set a nut and sleeve on the tube, the tube is flared with special equipment, diameter D should fall between diameter D1 and D2, see Fig .9.
Fig . 9
b) Over half of the leakage with flared fittings is caused by impoper flaring or installation, when saaembled, the axis of the tube, the tube flare and the fitting nose should be concentric.
c) Screw the nut onto the fitting body by hand and tighten it to the recommended torque with a torque wrench. if torque wrenches are not available, tighten 1 to 2 turns with general wrench .In general, the smallfitting is tighten about 1 turn and the large fitting is tighten about 2 turns.
2.2 Reassembly
Fitting can be used many times. To ensure this, part must be clean and free of defects .no tube cracked.
2.3 Leakage reason
a) When assembled, the axis of the tube, the tube flare and the fitting nose are not concentric, force the tube to the station.
b) The tighten force is too large or too small.
c) The tube flare cracked.
d) The fitting body or the tube flare is collapsed.
e) The connected nut is loosen.
f) The sealing suface is damaged for longer torque or reassembly time after time.
g) The tube flare is too large or too small, so the seal between the fitting nose and the tube flare is not effective.
Taper Thread Fittings
1. Taper Thread Fittings Intructions
1.1 The connected thread has three types: NPT, NPTF and BSPT .
1.2 NPT、BSPT threads should be assembled with sealant. NPTF is metal to metal seal, but use sealant also. Sealants are available in various forms such as leflon tape, paste and anaerobic glue etc…
1.3 Teflon tape, paste etc..if applied improperly, they will pollute the oil the hydraulic system, even jam the system.
1.4 The seal of the small thread is better than the large. In general the seal of less than 3/4” are good.
1.5 The connect will compact when the taper thread for straight fitting, if for eblow or tee pr cross fittings, the assemble angle is diffcult to contron, so suggest that the adjustable stud end fittings should be used, for example ISO 6149, ISO 11926 etc..
2. Taper Thread Fittings Assembly Instructions
2.1 Assembly
a) Inspect port and connectors to ensure that threads on both are free of dirt, burrs and excessive nicks.
b) Apply sealant to male pipe threads .With any sealant, the first and second threads should be uncovered to avoid system contamination. If teflontape is used it should be wrapped 1-1/2 to 2 turns in clockwise direction when viewed from the pipe thread end.
c) First tighten the fitting with hand, then tighten with a wrench 1-1/2 to 3 turns. In general, the small fitting is tighten about 2.5 turns and the large fitting is tighten about 2 turns.
2.2 Reassembly
The taper thread fitting can be reassembled. When reassembled, check if sealant has worn thin.
2.3 Leakage Reason
a) There is no sealant used or sealant has worn thin.
b) Threads are galled.
c)Fitting screws in too far into the port.
d) Threads are severely nicked.
e) Threads are loosen.
Routing of tube lines
Routing of tube lines should pay attention to the following.
1. The length of tube should be short and tube O. D. should be suitable, the energy will loss if the velocity is too large.
2. The tube connection should avoid strain, it is good that have a bending part. see Fig. 1.
Fig . 1
3. The tube bending radius is large as possible. The min. bending radius is about 2.5 times of the O. D. The tube end should be straight and the spacing is above 2 times of the tube nut . see Fig .2
Rmin=2.5D H≥2h
Fig. 2
4. Fatigue failure due to mechanical vibration accounts for the majority of tube line failures. when the tube line is longer, we can use tube clamps to support the system. Proper clamping of the tube can reduce system noise. Recommended tube clamp spacing as shown in Fig. 3 and table 1.
Fig. 3
Table 3
（mm） TUBE O.D. | A（mm） CLAMP SPACING | B（mm） CLAMP SPACING | C（mm） CLAMP SPACING |
6-12.7 | 50 | 900 | 100 |
15.9-22.2 | 100 | 1200 | 200 |
25.4 | 100 | 1500 | 200 |
37.8-38.1 | 150 | 2100 | 300 |
48.3 | 150 | 2700 | 300 |
5. Get around obstructions without using excessive amount of 90°bends. Pressure drop due to one 90°bend is greater than that due to two 45°bends. See Fig. 4
Fig. 4
6. Keep tube lines away from components that require regular maintenance.
Fig. 5
7. Have a neat appearance and allow for easy trouble-shooting, maintenance and repair. See Fig. 
Fig. 6
