Duo Cone Mechanical Seals offer the following advantages:

• Simple, reliable design;
• High sealing effect against dirt, dust, water and abrasive media from outside and oil and grease from the inside;
• Cost Effective;
• Simple Installation;
• Long Service Life;
• Self centring to compensate for shaft eccentricity or misalignment.

There are two different types of Heavy Duty Seal. The most common type is PADO which is characterised by the use of an O-Ring (refer figure A). The other type of Heavy Duty Seal is PADF, which has a diamond shaped elastomer as the secondary sealing element instead of an O-Ring (refer figure B).

In seal type PADO, the rear seal surface is formed by a cone which is in contact with the O-Ring which is compressed both axially and radially. This generally requires the housing contour to be formed by a NC machine tool.

With seal type PADF the housing is of simple geometry, however this style is more expensive due to the special elastomer construction.

Method Of Operation
The elastomer rings hold the seal rings flexibly in the housing. They apply the axial pressure to the seal faces and form an effective seal in the housing. They also prevent the seal ring from turning with the shaft. The seals are installed so that one seal is stationary while the other rotates. The lapped sealing faces slide against each other on a thin film of lubricant. This prevents oil escaping from the system while preventing contaminants from entering.

The seal rings form a wedge shaped gap which allows sufficient lubricant to be supplied from the shaft. The pre-compression of the elastomer rings compensate for wear of the seal rings during service, maintaining seal effectiveness during it’s service life.

Applications
This type of seal is predominantly used for sealing the bearings in construction machinery or production plant operating under extremely arduous conditions and subject to severe wear.

• Crawler-mounted vehicles, such as excavators, bulldozers etc.
• Conveyor Systems
• Heavy Trucks
• Tunnel Heading Machines
• Mining Machines

Operating Pressure
The seals should not be subjected to maximum pressure.

The shaft seal is pressure free under normal operating conditions.

Pressure loading up to Max 0.3 Mpa (3 Bar) for shell moulded cast iron and 0.15 Mpa (1.5 Bar) for 100Cr6 material.

Operating Speed

Cast Iron:	10 m/sec with oil lubrication
	3 m/sec with grease lubrication
100Cr6:	4 m/sec with oil lubrication
	1.5 m/sec with grease lubrication

Media
The best results with regard to wear and service life are achieved with oil lubrication. It is sufficient if the oil level is 1/2 to 1/3 of the seal inside diameter. If unusual oil is to be used (such as "bio" environmentally compatible) testing the compatibility with the elastomer is recommended prior to installation.

Materials
Heavy Duty Seals are available in two material types. These are shell mould cast iron and 100Cr6 bearing steel. The standard material we offer is 100Cr6 for reasons of cost effectiveness. These seals are manufactured by copy turning followed by induction or salt bath hardening. The hardness is 58 to 63 HRC. The seal faces are then lapped and polished. The material specifications are listed below.

Material Chemical Composition	100Cr6 Bearing Steel (Material 1.3505)
C (Carbon)	0.90 - 1.05
Si (Silicon)	0.15 - 0.35
Mn (Manganese)	0.25 - 0.45
P (Phosphorous)	<0.03
S (Sulphur)	<0.025
Cr (Chromium)	1.40 - 1.65
Mo (Molybdenum)	-
Ni (Nickel)	<0.30
Fe (Iron)	balance

Design Instructions
The installation dimensions of the seal groups are shown in the following table. A template can be used to check the housing geometry for type PADO. The axial gap "S" in the housing is such that it meets the demands of the construction machinery industry.

Cross Section "d"	Gap "S"
<8.0 mm	4
<10.0 mm	5
<12.7 mm	6

Surfaces
Under pressure, elastomers adapt themselves to irregular surfaces. However for fluid tight conditions certain minimum requirements have to be made on the surface finish of the faces to be sealed. Scores, scratches, pores and concentric or spiral machining scores are not permissible. For the surface of the seal installation chamber we recommend a machining quality as follows:

	Shaft Finish
Ra	<3.2µm
Rz	<10.0µm
Rmax	<16.0µm

Installation Instructions
Heavy Duty Seals must be installed with great care. Damage to the precision lapped seal faces must be avoided at all costs. The installation location must be kept free from dust and dirt.

Installation should be carried out in the following steps:

• Remove the seal from its packing only when ready to install;
• Do not let the seal stand on the lapped surface under any circumstances;
• Coat the seal face with a thin film of clean oil using a lint free cloth e.g chamois leather;
• Fit the two seals into their respective housing;
• Check that the seal face is at right angles to the shaft axis. The O-Ring must not be twisted or crooked in the housing;
• Fit the two parts together, bringing the sliding surfaces carefully into contact;
• Adjust the gap "S" to the correct dimension;
• Fill the application with oil and bleed to the correct level if necessary.

Installation, particularly of large O-Rings, requires a great deal of force. We recommend that the O-Rings be coated with a lubricant such as soapy water to aid the installation process.