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Blogs about hydraulic systems design

Hydraulic motor case flushing

Hydraulic motor case flushing

Hydraulic motor case temperature

At the latest my project I used hydraulic motor Rexroth A2FLM710 (710cc). The motor works at 1400 rpm and provides 590 HP to the consumer. Foe safe motor work I always try to keep the case temperature below 80*C. The easiest way to do this is a flushing flow adjustment.

In addition to the flow, you need to keep eyes on a case pressure and try balancing to prevent overpressure in the motor case (check in the motor manufacturer’s catalog the max available case pressure to make longer life of motor shaft seals).

The values I came are 21 GPM at 30 psi case pressure and in the worst-case scenario (max motor load, warmed hydraulic oil) case max temperature was around 80*C

Hydraulic motor case flushing

Hydraulic motor case flushing flow and case pressure

There no prescriptions or recomendations for valve or orifice size in motor catalogs for flushing flow, so the selection of flushing valves is a challenge.

Of course, you can find orifices (with different diameters) provided by the manufacturer with the motor in the motor’s catalog. But the flow and result case temperature will be different from application to application and the selection of correct orifice is an engineering responsibility without any help or advice from motor manufacturer.

Moreover, the manufacturer can’t provide all range of orifice diameters so the selection in the catalog is usually limited. And as you can see, sometimes values of flushing flow can be really huge and the only experience helps me to select the right flushing valve size at the beginning of the project.

I still believe, manufacturers can provide some diagrams/charts with correlation power-> flushing flow for approximate/preliminary estimation of the flushing valve size. Because I do not think everyone has a chance to make long tests during production and play with valves sizes…

What do you think?

Magnetic Filter Scrubber

Just impressed how efficient can be Magnetic Filter Scrubber. I use it at all applications and photos below can explain why.

Magnetic Filter Scrubber

Magnetic Filter Scrubber after 1 year unit work in the field

I mount these filters at the bottom of the tank downstream the butterfly shuttle valves (tank outlet ports). In case of service, these valves closing and checking/cleaning of scrubbers can be done without full oil drain from the tank. For that, each scrubber is provided with -04 orb port which lets to drain small qty of the hydraulic oil from the scrubber itself.

Magnetic Filter Scrubber

Magnetic Filter Scrubbers mounted to the tank

I’m not showing the brand of the scrubbers at the photo, this is not an advertisement of the specific brand, just wanna share the idea to use scrubbers, especially in the mobile applications, where the size of tanks usually not big enough to sedimentation of particles to the bottom of the tank.

How to select a hydraulic cooler

At this article, I show my vision on how to:

  • determine the value of the heat needs to be rejected from the system;
  • calculate and select the right cooler size.

…and will provide an example of cooler calculation and selection.

What is a cooler and what is a heat exchanger?

The hydraulic cooler is one of the heat exchangers type. But, what is a heat exchanger? The best definition of the heat exchanger is:

Heat exchanger is a device that transfers heat between two fluids.

The simple sentence but a very good description, because fluids can be either oil, air, water, etc., and because transferred heat can be for either cooling or heating target.

There are two most popular types of heat exchangers in hydraulic systems:

Plate heat exchangers

Plate heat exchanger

Plate heat exchanger

This type has the best value of efficiency/reliability and designed for both cooling and heating applications and a very good for low-viscosity fluids. Pairs of plates can be removed individually for maintenance, cleaning, or replacement. Another advantage of the plate is exchangers is their low initial cost, as well as easy and inexpensive operation.

Fan radiators (air-cooled)

Fan radiators (air-cooled)

Fan radiators (air-cooled)

This type is the only option where water is unavailable or expensive for a delivery. From benefits: low maintenance and operating costs and the only option for oil cooling in mobile applications.

Fluid Power Reference Handbook review

Fluid Power Reference Handbook

Fluid Power Reference Handbook

This weekend I have received the first edition of the Fluid Power Reference Handbook from Fluid Power Society and in this article I would like to share my first impression about (my potential) ref-book for $75 USD.

Yes, I have paid $74.95 USD + 27.75 USD for delivery to Canada. If you are not a member of IFPS, the price for this handbook to be $99.95 USD. But if be honest, even $75 is pretty expensive for me. But I was assumed this book will be my table book for everyday usage and decided to spend so much money.

The book was delivered in a simple soft paper envelope and was damaged in its way, thanks to USPS and Canada Post. Actually, IFPS could send this book in a safe envelope with bubbles, but they didn’t do that, unfortunately. So, pages were crumpled and the back cover is with a scratch (the book has a softcover binding).

Anyways, it is what it is. Let’s take a look at what is inside of the book. And I’m going to compare this issue with my existing “Lightning Reference Handbook” (Eight Edition, 2001) that I was gotten from the vendor for FREE 6 years ago.

Fluid Power Reference Handbook consists of 20 chapters, 360 pages. Each chapter has own color with bookmarks at the side and it is really comfortable to search a targeted chapter. The paper is of pretty good quality and thickness what is good for everyday usage: