What is VMI?

(VMI) Vendor managed inventory is an inventory management process in which a Supplier of goods is responsible for the management and optimization of the inventory held by the customer or end-user.

What are the benefits of VMI?

There are several benefits of a Vendor Managed Inventory system (VMI)

  • Patriot Fluid Power dedicates its resources to managing your inventory, so you don’t have to
  • Detailed reports on number of inventory turns – Stocking level accuracy
  • Forecasting and cost analysis reports
  • Elimination of data entry errors through scanning of labels
  • Cost savings due to the elimination of factory minimums
  • Cost savings illustrated by the elimination of down time
  • Elimination of overnight shipping and expediting charges
  • Works with smart phone, no special equipment needed!

Most Common VMI system

One of the most widely used methods of VMI is a 2-bin, Kanban style system. Kanban is a workflow management process designed to help you maximize your efficiency. The primary goal is to reduce costs while creating more value for the customer. The Kanban system utilizes two physical bins with a min and max inventory level assigned by part number. It allows you to manage your inventory critical parts (such as O-rings, seals, custom seal kits, gaskets, etc…). The min and max levels are established by number of turns, the critical assignment and lead time. This is a relatively simple system because the parts are contained in two rotating bins. Parts are pulled which are used to fill orders or provide components to various workstations or departments.

For example, employees pull parts from one bin (front bin) until it is empty. Next, they rotate to the second bin (back bin). They scan the bin label with a phone or other scanning device. Thus, placing an order with Patriot Fluid Power to replenish the inventory in the first bin. This ensures that there is little to no risk of running low or out of stock due to normal usage.

What is Vendor Managed Inventory - by Patriot Fluid Power
Patriot Fluid Power Vendor Managed Inventory Label

Patriot VMI works!

We have developed VMI software that works on any smart phone!

Patriot can offer solutions for VMI tailored to your needs. First, Patriot will setup your facility by cataloging your parts. Next, we will recommend min and max levels based on usage analysis and create scannable code labels for easy reorder. In addition, we will help monitor your usage and recommend adjustments. Finally, Patriot can supply you scannable paperwork and labels so parts can be scanned into your ERP eliminating human data entry errors.

Please contact Patriot Fluid Power so we can recommend a Vendor Managed Inventory (VMI) system that would be right for you!



An O-ring, also known as a packing or a mechanical squeeze seal, is a torus or doughnut shaped ring with a round cross-section. They are generally molded form an elastomer such as a rubber compound, however, O-rings are also made from PTFE (Teflon®) and several other thermoplastics as well as metals.

O-rings are one of the most common hydraulic and pneumatic seals used in machinery design due to the fact they are easy to manufacture, are very inexpensive and have relatively simple mounting/installation requirements.


O-rings were first patented May 12, 1896 by Swedish inventor J.O. Lundberg. The US patent was filed by machinist, Niels Christensen in 1937. He used the O-ring as a component in a hydraulic braking system and described it as “a circular section ring . . . made of solid rubber or rubber composition”.

After migrating to the United States in 1891, Christensen patented an air brake system for streetcars. Later the US government commandeered the O-ring patent During World War II and classified it as a critical war-related item thus giving the right to manufacture to other organizations.


O-rings are used primarily for sealing but are also used as a lighter-duty mechanical belt drive. They can be used in static (motionless) as well as dynamic applications (motion between parts). O-rings have been tested in certain applications to seal up to 5000 psi. The maximum sealing pressure of an O-ring will depend on the seal durometer (hardness) and the diametrical clearance between the mating parts.

They have a temperature range between -50f up to +650f for rubber elastomers and as high as +1600f for O-rings manufactured using metal compounds.

O-Ring Applications - by Patriot Fluid Power

Some common applications for O-rings include hydraulic cylinders, pneumatic cylinders, pumps, motors, valves, hose fittings, fluid or gas sealing, vacuum sealing, and many other custom and standard applications.

If you have any questions about o-rings or seals you can contact Patriot Fluid Power anytime.


Hydraulic Seals and Pneumatic Seals

Many seals on the market are interchangeable between hydraulic and pneumatic applications, therefore it is the details of your application that will determine which seal to use. For example, you will need to know your media, pressure, temperature, and speed/velocity.

Hydraulic seals can be made from a variety of materials and durometers such as rubber, fabric reinforced rubber, polyurethane, PTFE, and PTFE blends. The type of material is determined by the specific operating conditions or limits of your system.

Pneumatic seals are predominantly made using a softer elastomer such as rubber. There have been many improvements in materials over the years with new technology creating internally lubricated elastomers for pneumatic applications with little to no system lubrication. Like the hydraulic seals, the type of material is determined by the specific operating conditions or limits of your system.

Two Basic Types of Seals

There are basically two different types of seals, pure lip seal and pure squeeze seal. There are also three basic shapes of seals, round, square and rectangular. Below is an illustration of a lip seal and a squeeze seal in their “free” state as they would appear outside the groove, and how the seal would appear when installed in the groove. Also, an illustration of the three basic seal shapes.

Pure Lip Seal Pure Squeeze Seal comparison brought to you by Patriot Fluid Power

Below is a continuum with pure lip seals on the left where there is low friction, wear and sealability. On the right is pure squeeze seals where friction, wear and sealability are high. The compromise seals in the middle will have varying amounts of friction, wear and sealability.

As we move from left to right on the continuum, we move from simply bending the seal lips to displacing increasing amounts of material. The more material displaced the more mechanical squeeze generated, the greater the sealability but also friction and wear increase. As friction and wear increases seal life decreases.

Seal Types Continuum brought to you by Patriot Fluid Power

In general, most pneumatic seals can be used as a hydraulic seal in applications of lower psi. Conversely, most hydraulic seals cannot be used as a substitute for pneumatic seals due to the hardness of the material. As stated earlier, your specific application will determine which seal is best for you.

If you have any questions about seals you can contact Patriot Fluid Power anytime.



The quick answer, as it relates to seals, is that durometer is the hardness of the seal material, however, there is much more information that is critical when selecting the correct seal for your application. Durometer is more commonly referred to as a Durometer Scale. Although there are several scales of durometer, the two most commonly used scales for measuring the hardness of polymers, elastomers and rubbers, are the ASTM D2240 type A and type D scales.


The Shore hardness standard refers to a measuring device that was developed in the 1920’s by an American metallurgist, Albert Ferdinand Shore. In the case of Shore, his was not the first to measure hardness or to be called durometer, but today the name usually refers to Shore Hardness. Furthermore, there are several other devices and scales used to measure hardness, for instance the Rockwell Scale.


“Durometer, like many other hardness tests, measures the depth of an indentation in the material created by a given force on a standardized presser foot. This depth is dependent on the hardness of the material, its viscoelastic properties, the shape of the presser foot, and the duration of the test. ASTM D2240 durometers allows for a measurement of the initial hardness, or the indentation hardness after a given period of time. The basic test requires applying the force in a consistent manner, without shock, and measuring the hardness (depth of the indentation). If a timed hardness is desired, force is applied for the required time and then read. The material under test should be a minimum of 6 mm (0.25 inches) thick” [1]
[1] “Rubber Hardness”. National Physical Laboratory, UK. 2006. Retrieved 2006-07-22.
Durometer hardness test Patriot Fluid Power
Durometer hardness test Patriot Fluid Power


The below Hardness scale illustrates a comparison between the Shore A, Shore D and Rockwell R scale and how some measurements overlap each other. For example, a measurement of 90 durometer Shore A is comparable to 40 durometer shore D.
Patriot Fluid Power hardness scale chart
Patriot Fluid Power hardness scale chart


The majority of sealing applications use an elastomeric seal (NBR/Buna, Viton, Silicone, EPDM) ranging in hardness between 70 and 90 Durometer-Shore A. There are several factors within the application that will dictate the durometer of the seal to be used. For example, pressure. Generally, lower durometer seals perform very well in low pressure applications as they produce less resistance to the surface of whatever is being sealed. On the other hand, the higher the pressure the higher the durometer or hardness of seal will be required. In high pressure applications the likelihood of extrusion through the clearance gap increases. (see chart below). Higher pressure combined with higher durometer seals will increase the friction at the sealing point of contact. Many factors must be considered when selecting the proper durometer and seal material. The graph below shows the relationship between pressure, durometer and diametrical clearance (the radial clearance if concentricity between the piston and cylinder is maintained)

Patriot Fluid Power rubber o-ring extrusion/diametrical clearance chart
Patriot Fluid Power rubber o-ring extrusion/diametrical clearance chart

If you have any questions about seals you can contact Patriot Fluid Power anytime.