General FAQs

Why are the O-rings used with Zero-Leak Gold Plugs smaller than the O-ring used in comparable size SAE and Metric Plugs?

The O-rings used with Zero-Leak Gold Plugs are all standard metric sizes and are available in Buna Nitrile 70 durometer as standard and in Viton, EP, etc. materials as special order.

The Zero-Leak Gold Plug O-ring is located under the head of the ZLGP in a recess that has a cross sectional area that is greater than the cross sectional area of the O-ring. The smaller ZLGP O-ring allows it to perform its secondary seal function with less than a 100% port squeeze fill rating while its SAE J514 counterpart requires more than 100%. The fact that their squeeze fill is greater than 100% is a contributing factor that is conducive to O-ring taper being forced into the interface of the threads of the port + plug.  Here it may become nibbled + damaged, or extruding onto the spot face where a leak path may occur, nibbling and extruding.

The convergence of the tapers of the SAE J514 and Metric Plug port and the ZLGP invoke maximum gap minimization and high unit loading at that point. This feature prevents the O-ring from passing between the ZLGP and the taper of the port. Should the metal-to-metal seal fail and therefore require the O-ring (back-up seal) to make the seal, the small diameter O-ring is sufficient to make the seal.

The fact that the ZLGP O-ring does not have any sealing pressure applied to it unless the primary metal-to-metal seal fails, allows the ZLGP O-ring to have a longer useful life than the SAE J514 and Metric plug O-ring, which is under constant pressure of the fluid it is attempting to contain. The ZLGP O-ring won’t take a set, be nibbled by the threads of either the ZLGP or port, nor will it be extruded. All of these problem conditions may exist with O-rings used with the old style, O-ring dependent SAE J514 and Metric plugs.

Are there magnetic Zero-Leak Gold Plugs?

Zero-Leak Gold socket and hex head plugs are excellent for use with Magnets installed. Magnetic plugs are designed to attract metallic particles for removal from fluid systems. The design of the ZLGP allows it to be removed and installed repeatedly without damaging the threads of either the plug or port. The recess under the head of the ZLGP prevents the O-ring, which rests there, from being nibbled by the threads of either the plug or port. This same recess, combined with the engagement of the tapers of the ZLGP and port, prevents the O-ring from being extruded. No chemical sealant of any kind is required with ZLGP. This feature makes installation trouble free and eliminates the possibility of system contamination that may be the result of plug removal and installation. The fact that the ZLGP have two independent seals with the metal-to-metal being the primary seal and the O-ring is the back-up seal, assures that a seal is still possible should the O-ring be lost or damaged when servicing the magnet. Since the ZLGP performance is based on two seals, a replacement O-ring must be installed promptly to insure the total sealing capability of the ZLGP. Typical applications would be truck transmissions, compressor drain / fill, hydraulic gear boxes, diesel engine oil drain / fill, etc.

What type of O-ring materials are available for use with Zero-Leak Gold Plugs?

The standard O-ring material supplied with Zero-Leak Gold Plugs is buna N 70 durometer. Viton Fluorocarbon, EP, etc. are available upon request. ZLGP use standard metric size O-rings which makes it possible for most commercially available O-ring material to be used with ZLGP.

What's the lead time to have Zero-Leak Gold Plugs shipped?

Mild steel Zero-Leak Gold SAE and Metric socket and hex style plugs with either buna N or Viton O-rings are, for the most part, stock shelf items and available for immediate shipment. In the event that an item is not in stock a shipment date will be determined.

An increasing number of stainless steel and aluminum socket head ZLGP sizes are becoming stock items.

The most commonly used SAE and Metric socket and hex head ZLG magnetic plugs are stock.

Custom configured ZLG components have inventory levels established to maintain the Kan Ban, cell manufacturing, etc. requirements of their users.

Rush, same day shipments can be made in most cases.

Contact an EPCO Applications Consultant for the current ZLGP availability status.

Is it possible to have the Zero-Leak Gold configuration on other products?

As long as the component has SAE J514 style threads and is used in the SAE J1926 port or metric style threads and is used in the ISO 6149 port, it is probable that the component could be produced with the Zero-Leak Gold design. It is recommended that a drawing be sent to EPCO for evaluation.

Are there metric size Zero-Leak Gold Plugs?

Yes. Complete information is at EPCO’s website under Plugs. The metric ZLGP have the individual metric sizes, ie., “10 x 1.5” engraved on the head of each ZLGP for easy and positive identification. The same is true for the SAE dash sizes being engraved on the heads of the SAE styles.

What has to be done to the ports that are in our products to use Zero-Leak Gold Plugs?

Zero-Leak Gold Plugs are interchangeable with SAE J514 style plugs that are used in SAE J1926 ports. In other words, nothing needs to be done other than take out the old style O-ring only SAE J514 plug and install the same Zero-Leak Gold Plug. The same applies to the metric Zero-Leak Gold Plugs with the straight thread metric plugs and ISO 6149 ports.

The two seals of the Zero-Leak Gold Plug (metal-to-metal primary and elastomeric back-up) are internal to the port and therefore it is not necessary to spot face the port in order for the ZLG plug to be fully functional.

The SAE J1926 and metric ISO 6149 port drawings may be found at EPCO’s website under Plugs.

Zero-Leak Gold Plugs are low torque...what are the installation torque values?

EPCO commissioned the Fluid Power Institute, located at the Milwaukee School of Engineering, to do tests to determine the Zero-Leak Gold Plug torque values necessary to successfully complete the rigorous fluid power industry standard tests.

The FPI test was conducted using both ductile iron and aluminum manifolds produced to industry use standards as specified by the FPI / MSOE. The text of the FPI / MSOE test is available in the Test Reports section under ‘Technical Info’ on the Zero-Leak Gold website.

It is important to note that the mild steel Zero-Leak Gold Plugs completed the entire one million cycles of the test without a failure! The aluminum Zero-Leak Gold Plugs did the same for two millions cycles!

The torque values developed by the tests are listed in the FPI / MSOE test report and at Torque Values & Tips under ‘Technical Info’ on the Zero-Leak Gold website.

Why don't Zero-Leak Gold Plugs leak?

Zero-Leak Gold Plugs provide both a metal-to-metal and elastomeric seal in their design. The metal-to-metal seal is accomplished by allowing the standard design geometry of the 12 or 15 degree taper that is present at the entry of the SAE J1926 port (see SAE port drawings at our site) to engage the corresponding taper located under the head of the Zero-Leak Gold Plug. As the ZLG Plug is engaged in the port the tapers converge and develop maximum gap minimization between the mating surfaces of the ZLG Plug and the port. This same contact point, by the very nature of the fact that only several thousandths of an inch of both the ZLG Plug and port come in contact, becomes the recipient of high unit loading which supports the metal-to-metal seal.

The O-ring acts as a back-up seal to the primary metal-to-metal seal. The back-up seal is made possible by the O-ring resting in a recess area under the head of the ZLG Plug that has a cross sectional area that is greater than the cross sectional area of the O-ring being retained. There is no pressure applied to the O-ring as long as the metal-to-metal seal is performing. If for some reason the metal-to-metal would fail, the O-ring acts as the back-up seal and prevents a leak.

The size relationship of the recess and the O-ring prevent the O-ring from being extruded at the spot face and/or nibbled when it may be forced into the interface of the threads of either the plug or the port as may be the case with standard SAE J514 or metric O-ring only style plugs.

The gap maximum minimization geometry of the metal-to-metal seal does not allow the O-ring to be extruded from the interface. The extrusion of the O-ring in standard SAE J514 and Metric style plugs is a common problem because vibration, pressure spikes, temperature changes can cause the SAE J514 and Metric plug to begin to back out. When the backing out begins this process is supported by the pressure being contained. At some point the plugs back out far enough for the O-ring to begin to extrude out of the interface with a leak path being established.

The same zero-leak performance applies to the metric O-ring straight thread plugs and ports.

Banjo Fittings FAQs

Why are there no crush washers used with the ZLG Banjo fitting?

The ZLG Banjo fitting utilizes a combination of metal to metal and elastomeric (O-ring) seals instead of relying on crush washers. See the answer to the next question below as well.

How do the metal to metal and elastomeric seals in the ZLG Banjo fitting maintain zero leak performance?

There are two metal-to-metal seals in every ZLG Banjo fitting assembly. The banjos are designed to utilize the taper that is part of the SAE J1926 and ISO 6149 port configurations. The first tapered metal-to-metal seal is located under the head of the ZLG Banjo bolt head. The angle of the taper engages with the taper in the port that is located on the top of the ZLG Banjo body.

The second tapered metal-to-metal seal is part of the bottom of the ZLG Banjo body through which the Banjo bolt will pass. The taper of this seal will engage with the taper in the port of the banjo host component. The taper at the top of the Banjo bolt and the taper at the bottom of the Banjo body engage in their respective ports and utilize the mechanical advantages of the tapers.

The metal-to-metal engagements minimize gaps that occur due to axial movement associated with internal pressurization. Each engagement is several thousandths of an inch. This generates high unit loading between mating components during application of assembly torque.

These design features combine to produce high integrity metal-to-metal interfaces.

Elastomeric seals (O-rings) act as “belt and suspenders” back ups for the metal-to-metal seals.

There are two O-rings in each ZLG Banjo fitting assembly. Both are positioned in machined recess whose cross sectional areas are greater than the cross sectional areas of the elastomers they contain.

The first O-ring is located immediately below the taper under the head of the banjo bolt. It is installed on the banjo bolt before the bolt is inserted in the banjo body.

The second O-ring is installed on the lower part of the banjo on the bolt after the bolt has been inserted through the banjo body. This O-ring is seated in a recess on the bolt, immediately below the taper on the bottom side of the banjo body.

The ZLG Banjo bolt and body assembly is held in place by swaging the skirt of the banjo body to form the lower taper. The tightening of the ZLG Banjo bolt into the host port engages both metal-to-metal seals and allows the two elastomeric seals to be in their proper positions, reacting dynamically to any pressure differential across the interface.

It is important to note that standard banjos have four leak-paths, one each side of the metallic crush washers used to seal them. The ZLG Banjo, however, only has two leak-paths, each sealed with metal-to-metal and elastomeric (O-ring) seals.

What assembly is required to use ZLG Banjo fittings?

See answer above.

What sizes of ZLG Banjo fittings are available?

The sizes that will accept the SAE J1926 and ISO 6149 port configurations.

What are the manufacturing and surface finish tolerance of the ZLG Banjo fittings?

Standard Machining Surface Finishes ± 1 – 0.005″.

What size O-rings are used with the ZLG Banjo?

Commercially available standard metric sizes.

What durometer and elastomeric material (Polymer) are used with the ZLG Banjo fitting?

70 durometer material is used because its relative flexibility allows it to respond to the pressures that may occur during operational service. The elastomer can move dynamically to fill the leak path.

Most material that is commercially available may be used with the ZLG Banjo fitting. The type of material to be used is determined by the end user and application parameters.

What type of port accepts the ZLG Banjo fitting?

SAE J1926 and ISO 6149. For the ZLG Banjo system to function, either the SAE J1926 or metric taper at the mouth of the port is a necessary feature.

What design options are there with the ZLG Banjo fitting body?

The body may be designed and machined to accommodate brazed components to form elbows, tees and crosses, and configured to accept hose or tube.

What materials may be used to produce ZLG Banjo fitting assemblies?

  1. Banjo bodies – Plated low carbon steel, stainless steel, brass or aluminium.
  2. Banjo bolts – Plated low carbon steel, stainless steel, brass or aluminium.
  3. Tube material – Stainless steel, low-carbon steel, aluminium.
  4. Port material – Cast steel, cast iron, low carbon steel, aluminum (cast or extruded).

Can the ZLG Banjo fitting be removed and reinstalled?

The ZLG Banjo fittings may removed and reinstalled repeatedly. The actual number of times may be determined by specific application testing.

What pressures can be applied to the ZLG Banjo fittings?

The standard range of banjos (SAE -4 to -10 and metric -6mm to -16mm) is designed to resist 6,000psi; however, assemblies can be specifically designed to meet customers’ specific pressure  requirements.

What about low pressure applications?

Low pressures can be as difficult as higher pressures to seal due to the effects of vibration and temperature variations. The ZLG Banjo fitting functions as effectively in these conditions as they do at higher pressures.

What are some typical applications for the ZLG Banjo fitting?

To replace the crushwasher style banjo fitting assemblies that may be leaking. Also to replace SAE J514 and ISO adjustable elbows, tees etc., where simple assembly and tight environments dictate a better answer. Typical applications include fuel rails, diesel fuel supply lines, hydraulic pump and valve assemblies, oil cooler lines, lubrication lines, air-conditioning systems, and brake assemblies (particularly at the caliper).

What effect does vibration have on the sealing ability of the ZLG Banjo fitting?

When the male tapers on each component engage with the tapers in their respective ports, they create a holding effect like the Morse taper. The tighter the engagement, the stronger the holding ability of the mating tapers, and the greater the resistance to separation. The data in the Fluid Power Institute reported the removal torque of ZLGP is greater than the insertion torque due to the mechanical advantage of taper, the same characteristic applies to the ZLG banjo. By using the elastic memory inherent in most metals, the ZLG Banjo offers exceptional resistance to vibration, pressure spikes, thermal transients and impact shock. By combining metal-to-metal seals with elastomeric (O-ring) back-up seals, the ZLG Banjo is the most robust banjo assembly available.