FluidPower.Pro

Articles

Articles about hydraulic, pneumatic, lube, etc. systems design.
Feel free to post your article here!

Fluid Power world-wide pressure gauges

The company where I’m currently working manufactures and ships equipment around the world.
Although the SI unit for pressure is the Pascal (Pa), different countries use their own kind of “standards” for pressure measuring, and when designing the system I need to keep in mind what country our equipment is shipping to. Below are just my notes/recommendations, which I personally use in my practice in case if customer doesn’t have specific requirements for pressure gauges (brand/units). Since our equipment is designed and manufactured in Alberta and Texas, I use a primary scale that matches the region and “psi” scale as a secondary one.

Region Unit Gauge unit(s) scale Example
North America
South America
psi
(Pounds per Square Inch)
psi
Australia
China
kPa or MPa
(KiloPascal or MegaPascal)
Dual: psi/kPa
Western Europe
Arabic Countries
bar
(Bar)
Dual: psi/bar
India
South Korea
South Asia
kg/cm²
(Kilogram per square centimetres)
Dual: psi/kg/cm²

The unit converter you can find by this link.

Most popular pressure gauge scale ranges:


   30 psi =    207 kPa = 0.207 MPa = 2.068 bar
   60 psi =    413 kPa = 0.414 MPa =  4.14 bar
  160 psi =  1,103 kPa =   1.1 MPa = 11.03 bar
  200 psi =  1,379 kPa =  1.38 MPa = 13.79 bar
  600 psi =  4,136 kPa =   4.1 MPa =  41.4 bar
1,000 psi =  6,895 kPa =   6.9 MPa =    69 bar
2,000 psi = 13,789 kPa =  13.8 MPa =   138 bar
3,000 psi = 20,684 kPa =  20.7 MPa =   207 bar
5,000 psi = 34,474 kPa =  34.5 MPa =   345 bar

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.

Read more >>>

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!