SAE J518 Code 61

QS Pipe Fitting: Zhangzhou Sae J518 Code 61

A Code 61 hydraulic flange connection to SAE J518 joining tube to port with an O-ring sealed, four bolt split flange.

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One-Minute Overview

A Code 61 hydraulic flange connection built to SAE J518.
Flat face sealed by an O-ring seated in the port groove.
Four bolt split flange clamps the tube or adapter to the port.
Size, pressure series and material are confirmed per inquiry.

SAE J518 Code 61 is the four bolt flange connection that hydraulic systems use to join a tube or hose assembly to a pump, valve or cylinder port. Instead of a threaded joint that can work loose under vibration, it clamps a flanged head against a flat port face with two split flange halves and four bolts, while an O-ring seated in a groove on the face does the sealing. The result is a compact, leak tight joint that is easy to assemble in a tight machine space and easy to break for service. Code 61 is the standard pressure series of the SAE J518 family, and it is a fixture on hydraulic power units, mobile equipment, presses and industrial fluid power lines.

Name: SAE J518 Code 61
Type: Four bolt hydraulic flange connection
Standard: SAE J518 Code 61
Sealing: O-ring in the port face groove
Connection: Split flange halves bolted to the port
Application: Hydraulic and fluid power piping
Feature: Compact, leak tight high pressure joint
Sizes in inches, wall schedules and end preparation are confirmed per inquiry, and a detailed specification sheet is available on request.

Start by confirming the series and the size. SAE J518 defines more than one pressure series, so check whether the duty calls for Code 61 or the heavier Code 62 pattern, because the bolt spacing and the flange head differ between them and they do not interchange. Match the tube outside diameter and the port pattern to the component drawing, then choose the flange material and the O-ring compound for the fluid and temperature: a carbon steel flange with a standard nitrile seal covers most mineral oil duties, while corrosive environments or fire resistant fluids call for other choices. Series, size and material are confirmed per inquiry against the port and line specification. Every size, wall schedule and end type is confirmed per inquiry against the spool drawing.

Assembly is simple but unforgiving of dirt. Clean the flat face and the O-ring groove, fit the correct O-ring without twisting it, and check that the groove is free of nicks before the flanged head is offered up. Set the two split flange halves square, bring the four bolts in evenly by hand, then tighten them in a cross pattern in stages to the recommended torque so the head sits flat and the seal compresses uniformly. Do not use the flange to pull a misaligned tube into place, support the line against vibration, and after the first pressure cycle inspect the joint for weeping and recheck the bolt torque.

FAQ

Q1. What is the difference between Code 61 and Code 62?

They are two pressure series within the same SAE J518 family. Code 61 is the standard series with a certain bolt pattern and flange head, while Code 62 is the heavier, higher pressure series with larger bolts and wider spacing. Because the drilling and the head differ, the two are not interchangeable on the same port. Confirm which series the pump or valve port is machined for before ordering, or the flange simply will not bolt up.

Q2. Where does the seal actually happen on this joint?

In the O-ring, not in the metal to metal contact. The flanged head carries an O-ring in a groove on the flat port face, and the four bolts squeeze that ring just enough to make the seal. The metal faces provide the clamp and stop the ring extruding, but if the groove is scored or the ring is nicked, twisted or the wrong compound, the joint will weep no matter how tight the bolts are. Most flange leaks trace back to the seal, not the torque.

Q3. Can I tighten just two bolts now and do the rest later?

Not if you want it to stay dry. Uneven tightening cocks the flanged head, so the O-ring compresses on one side and gapes on the other, and that is a leak waiting for the first pressure spike. Bring all four bolts up evenly in a cross pattern, in stages, to the recommended torque. It takes an extra minute and saves the cleanup, the top up and the embarrassed call to maintenance.

Q4. How long will production take?

Standard sizes are typically ready within 30 days, and in-stock items ship immediately. Larger or custom orders get a confirmed date per order, because the schedule depends on quantity, material, the bolt pattern you specify, and how busy production is at the moment you order.

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