FluidPower.Pro

Author Archive: Dzyanis

Hydraulic oil density and Specific Gravity

Hydraulic oil Density is the ratio of its mass to the volume of space it occupies:

## \rho=\frac{m}{V} ##

The accepted units of measurement for density according to ASTM are kilograms per cubic meter (kg/m3, SI unit) or grams per milliliter (g/mL).

Hydraulic oil Specific Gravity (or “Relative Density”) is the ratio of Hydraulic oil density to water density at the specific temperature:

## SG_{oil}=\frac{\rho_{oil}}{\rho_{water}} ##

Substance with SG <1 will float on water (like hydraulic oil); substance with SG >1 will sink in water (like honey).

Next, both hydraulic oil density and Specific Gravity vary with temperature and pressure.

Reference: [https://www.internetchemistry.com/chemical-data/water-density-table.php]
Reference: [https://webbook.nist.gov/chemistry/fluid/]

This is why the ASTM D1298-12b “Standard Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method” states that accurate determination of the API gravity, density or relative density (specific gravity) uses a standard temperature of 60 degrees F (15 degrees C).

Reference: [https://www.astm.org/d1298-12b.html]

You can find in the oil specification table of every hydraulic oil manufacture either Oil Specific Gravity or Oil Density at the specific temperature of 60°F or 15°C.

As a result, to calculate Specific Gravity or Hydraulic oil density at 15°C and, respectively, Hydraulic oil density or Specific Gravity at 15°C. By ASTM D1298-12b water density at 15°C is 0.999103 g/ml, therefore:

## SG_{oil}=\frac{\rho_{oil}}{0.999103} ##

## \rho_{oil}=\frac{SG_{oil}}{0.999103} ##

Parker’s Gold Cup pumps: External filtration

Have you ever dealt with Parker’s Gold Cup pumps? If yes, you probably noted in the product datasheet, this pump does not require to have filtration of internal charge (boost/replenishing) pumps flow. There is just a short recommendation “the auxiliary pump fluid be filtered to aid in maintaining acceptable cleanliness levels”:

The reason for that is because Parker thinks all close loop systems need to be designed to ensure “the oil tank is protected through filtration from any ingress contamination”. Later I shall show you Parker’s document where this statement is coming from (AS-0018). Actually, question to you: do you agree with this statement?

I do not. I use charge (boost/replenishing) flow filtration for every single close loop pump at every single project via an external filter connection. Moreover, both proportional and servo control systems require even more fine cleanliness level of the element for filtration, therefore for such systems I use two separate filters: for charge flow (usually 10 mkm element) and for servo control flow (usually 2 mkm element).

But there are a couple of problems with the Gold Cup pump external filtration. Although these pumps have ports for external filtration and even a short guide in the datasheet on how to make filtration (screenshot above) due to design of internal galleries is different for all three Gold Cup pump frame sizes, and, in addition, is different for specific side a control system is mounted on, you will not be able to provide a correct filtration and even can destroy the pump if connect external filter in the wrong way. And this problem is not explained and not resolved in the product catalogue.

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HAWE online product configurator

HAWE product configurator

It was always a challenge for us to configure HAWE proportional multi-section valves such as PSV, PSVF, etc. And I asked many times our vendor about something like an online configurator for HAWE products. You know, the best part of using tools like this is preventing errors, especially in so complicated configurations with a bunch of options. But the best what they suggested is to use HAWE CD with a very old configurator or just send requests to them. What actually is not a time-saving solution.

Here you can directly configure products, access product data, make a customer service request or program your machine control. You can also communicate directly with your contact person via the customer portal. We are looking forward to your feedback and requests in order to continuously optimize and expand our online service offer.
Your HAWE Team

So, what you need to start using product configurator is to make an account in HAWE Customer Portal first:

https://customerportal.hawe.com/

And now, almost for each product at their website you get a link to the “TypeMan+” platform, where you can configure the product. For example here is the link to PSV valve configurator:

https://typegen.hawe.com/?CLASS=C_PSV__110&LAN=en

In addition to the product configurator, you get a spare part catalogue, 3D catalogue and other benefits. Make your life easier!

How to Select, Design, and Install O-Ring Seals

Very good and interesting video about O-rings from Tarkka

Video description:

O-rings are the epitome of elegant engineering: The ring itself costs only a few cents, and the groove it goes in is simple and easy to manufacture. But despite this simplicity, the resulting seal is able to reliably hold many thousands of psi of pressure. O-rings are definitely a machine design component you’ll want to be familiar with, and in this video, we’re going to tell you all about how to design seals with them