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Pre-Grinder Cylinder: Hydraulic Sealing Case Study in the Philippines


Chesterton Asia Pacific case study APAC0001 – Chesterton products – Chesterton EPS Hydraulic Sealing




Thanks to a special seal-lip geometry, Chesterton’s entire operating range of hydraulic seals are designed to provide zero leakage. The sturdy static lip stabilizes the seal to prevent rolling, while the negative-rake design eases the installation process for a hassle-free experience.

Products featured in the case study:

Chesterton 22K

Chesterton 18K








Chesterton 21K

Chesterton 20K




In 2006, the original piston seal and rod seal of a Pre-Grinder Cylinder from a large Cement Company in the Philippines were made of Fabric Reinforced Neoprene Rubber.
This sealing material rags-out and produces fiber-like impurities that causes clogging and wear to the hydraulic valves. The clogging of the system results in the frequent shutdown of the system to fix the clogged valve.
In addition to this, the cylinder has no guard against side loading and metal-to-metal abrasion exists between the metallic piston and the barrel.

Root Cause
The material composition of the seal itself makes it prone to ragging-out into the fiber. The rod seal, piston seal and wiper are all made of the same fabric reinforced neoprene rubber, once the ragged-out fiber from the seals’ flow with the hydraulic oil, it can easily clog the valves.

Find a replacement for rod seals, piston seals, and wiper with different material composition. The material should not be prone to ragging-out and should be more resistant to abrasion. The new seal material should not rag-out and clog into the hydraulic valve. The new system should also have a guard against side loading and metal-to-metal wear.

Pre-Grinder Cylinder Position

Pre-Grinder Cylinder Position.

Valve where clogging occurs; ragged out fiber

Valve where clogging occurs; ragged out fiber.

Old piston sealing

Old piston sealing.


Chesterton® AWC800 22K Piston Seal, 22K Rod Seal, 21K Wiper and 20K Static D-ring are used in place of the Fabric-Reinforced Neoprene Rubber. AWC800 is a diamine-cured thermoset polyurethane which is a proven material to resistant ragging-out into fibers. Therefore, the valves will no longer be clogged, thereby preventing frequent shutdowns.

At the same time, AWC800 is abrasion-resistant, wear-resistant, extrusion-resistant, non-absorbent, and operates with low-friction because of its molybdenum disulphide lubrication. Also, to guard the cylinder against side loading and metal-to-metal abrasion on the adjacent metal surfaces (such as those on the piston/barrel interface and rod gland/rod interface), Chesterton® 18K GNF bearing bands are introduced both on the piston and rod gland.

Overall, aside from the prevention of clogging on the valve and prevention of wear between metallic parts, the main goal of the changes in the design is to lengthen the service life of the cylinder and ensuring leak-free service during operation.

Chesterton AWC 800 21K Wiper installed on Wiper Plate

Chesterton® AWC800 21K Wiper installed on Wiper Plate.  

Chesterton AWC 800 22K Rod Seal on Rod Gland

Chesterton® AWC800 22K Rod Seal on Rod Gland.

AWC 800 22K Piston Seal and 18K GNF Bearing Bands installed on the Piston

AWC800 22K Piston Seal and 18K GNF Bearing Bands
installed on the Piston.

Fully Refurbished Pre-Grinder Installed on Plant

Fully Refurbished Pre-Grinder Installed on Plant.


Client Reported
The clogging of the valve system is now prevented. According to the engineer in charge of the cement plant, they have a total of 11 shutdowns every year only to address the clogging brought about by the fibers produced by the ragging out of the seal. Thanks to the Chesterton product provided to the Customer, shutdowns are reduced to once every two years, for the replacement of the cylinder itself.
The use of thermoset polyurethane seal does not only solve the clogging but also lengthens the performance of the cylinder before leaking, from less than one year of service life, the pre-grinder cylinder now has about 2.5 years of service life. The customer started using Chesterton in 2006, and from this year onward, they have only had to recondition their pre-grinder cylinder once every 2 to 2.5 years.

Before changing into the Chesterton seal, the customers typical sealing cost is at Php. 80,000/year/cylinder. When they changed into Chesterton, their initial sealing cost is at Php. 120,000 however, since the seal life is now 2.5 years before the shutdown, their annual spend is only Php. 48,000 on the seal cost alone.
This results in a Php. 32,000 seal cost savings / year / cylinder. However, the original seal failure cost consequence meant substantial savings with the
change to the Chesterton solution:

  • Downtime Cost Savings per year = Php. 221,130.00 (Approx 6,500 AUD)
  • Labor Cost Savings per year = Php. 20,000.00 (Approx 600 AUD)
  • Spare Parts Cost Savings per year = Php. 140,000.00 (Approx 4,050 AUD)
  • Chrome Plating&Honing Cost Savings per year = Php. 220,000.00 (Approx 6,400 AUD)
  • HydraulicOil Cost Savings per year = Php. 20,000.00 (Approx 600 AUD)
  • Sealing Cost Savings per year = Php. 32,000.00 (Approx 900 AUD)

Total Maintenance Cost Savings per year = Php. 653,130.00 (Approx 19,000 AUD)

About us


Chesterton® is a world leader in helping process industry companies and manufacturers improve the reliability and efficiency of their rotating, stationary, and fluid power equipment platforms. Chesterton® is known across a wide range of industries for our award-winning pump and valve sealing solutions, applications expertise, equipment maintenance and wear-prevention products, and knowledgeable hands-on local service.​

visit https://chestertonfluidpower.chesterton.com/en-us/Products/Pages/HydraulicSeals.aspx

Mentioned in the case study:

Exclusive Distributor of Chesterton EPS in the Philippines. #5 Emerald St. Barangay Pasong Tamo, Quezon City, Philippines

Maker of Quality & Upgraded Hydraulic and Pneumatic Cylinders

® Registered trademark owned by A.W. Chesterton Company
Case Number APAC001 – Issued 07/20
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