Centrifugal force is the inertia force that arises in each rotating object. It is only required in a rotating reference frame – or, in other words, when we look at the system from the point of view of the object in motion.
F: the force
m: the mass of the object
v: the velocity
R: the radius
Standards organisations
IEC – International Electrotechnical Commission, publishes international standards for all electrical, electronic, and related technologies. www.iec.ch
NEMA – National Electrical Manufacturers Association, a U.S. trade association sets ratings for environmental sealing. www.nema.org
The IP Rating System describes the ‘degree of protection’ as defined by the International Electrotechnical Commission standard 60529 (IEC60529). IP stands for International Protection, frequently referred to as ‘Ingress Protection’. The degree of protection as defined by the IEC is used to describe:
The IP code designation consists of the letters IP followed by two numerals, and is sometimes followed by optional letters. The first number is a measure of how well the enclosure can prevent an invasion by solids. The second number indicates the degree of protection against liquids of various pressures, directions and volumes.
The IP rating system does not cover condensation, fungus and harmful vapour so assumptions should not be made that a highly rated switch will be protected.
NEMA considers numerous requirements including corrosion resistance, effects of icing, gasket aging and oil resistance and coolant effects. It is possible to say that a NEMA Type is equivalent to an IP rating but an IP rating is not equivalent to a NEMA Type. The IP code only address requirements for the protection of people, the ingress of solids and the ingress of water. The NEMA Types consider these and also numerous other requirements including:
IP69K
German standard DIN 40050-9 extends IEC 60529 with an additional rating for environmental sealing – IP69K, for high-pressure, high-temperature wash-down applications. Devices must not only be dust tight (IP6X), but also able to withstand high-pressure and steam cleaning. The test is very strict: 80°C water is sprayed through a nozzle at pressures of 8–10 MPa (80–100 bar) and a flow rate of 14–16 Litres/min. The nozzle must be held 10–15 cm from the tested device at angles of 0°, 30°, 60° and 90° for 30 seconds each. The test device sits on a turntable that rotates once every 12 seconds (5 rpm). The IP69K test specification was initially developed for road vehicles, especially construction vehicles and those that need regular intensive cleaning, but also finds use in other intensely hygienic applications (e.g. food industry).
NEMA
In the United States, the National Electrical Manufacturers Association sets the requirements for environmental sealing and its standards are widely used throughout North, Central and South America. The NEMA Standards Publication 250 – 2008 (previously 250 – 2003; 250 – 1997) “Enclosures for Electrical Equipment (1000 Volts Maximum)” defnes enclosures according to their type from 1 to 13. Detailed information on some of the types relevant to HMI components are shown in Table 3.
| Pipe Material | Absolute roughness k (mm) |
|---|---|
| Aluminum new | 0,001-0,002 |
| Brass | 0,015 |
| Brass new | 0,001-0,002 |
| Cast iron new | 0,25-0,8 |
| Cast iron slightly rusted | 1,5 |
| Cast iron very rusted | 3 |
| Cast iron with bitumen layer | 0,2 |
| Copper | 0,015 |
| Copper new | 0,001-0,002 |
| Epoxy, vinyl ester and isophthalic pipe | 0,005 |
| Flexible rubber tubing smooth | 0,006-0,07 |
| Glass | 0,015 |
| Lead | 0,015 |
| Lead new | 0,001-0,002 |
| Ordinary concrete | 0,3-1 |
| PVC and Plastic pipes | 0,0015-0,007 |
| Rough concrete | 0,3-5 |
| Sheet or asphalted cast iron | 0,01-0,015 |
| Smoothed cement | 0,3 |
| Stainless steel electropolished | 0,0001-0,0008 |
| Stainless steel turned | 0,0004-0,006 |
| Stainless steel, bead blasted | 0,001-0,006 |
| Steel pipe after longer use | 0,2 |
| Steel pipe galvanised | 0,15 |
| Steel pipe new | 0,04 |
| Steel pipe slightly rusted | 0,4 |
| Steel pipe very rusted | 3,35 |
| Stretched steel | 0,015 |
| Weld steel | 0,045 |
| Worn cast iron | 0,8-1,5 |
Absolute Roughness (k) is a measure of pipe wall irregularities. The absolute roughness has dimensions of length and is usually expressed in millimeter (mm) or feet (ft). Absolute Roughness is usually defined for a material and can be measured experimentally. Absolute roughness is important when calculating pressure drop particularly in the turbulent flow regime.
For each pipe material either a single pipe roughness value or a range of roughness values is normally provided by the manufacturer. The roughness value, usually denoted as e or k, is used in the calculating the relative roughness of a pipe against the size of its diameter.
The minimal Safety factor must be at least equal to:
7:1 for webbing and round slings
4:1 for accessories made of steel
5:1 for the remaining components
Recommendations of use:
The minimum length for the eyes is fixed by standard EN 1492-1 to 3 times the width of the sling for widths up to 150mm; 2,5 times for width above 150mm. These lengths have been fixed to respect an angle usage between 10° to 20° when using the slings. An excessive eye opening angle will open the sling and a small eye opening angle will generate a bending stress at the lifting axis.
The moment of inertia, otherwise known as the angular mass or rotational inertia, is a measure of an object’s resistance to change in rotation direction. Moment of Inertia has the same relationship to angular acceleration as mass has to linear acceleration.
For a point mass the Moment of Inertia is the mass times the square of perpendicular distance to the rotation reference axis and can be expressed as
I = m r2
Where
I = moment of inertia (kg m2)
m = mass (kg)
r = distance between axis and rotation mass (m)
| Material 1 | Material 2 | Static dry | Static lubricated | Dynamic dry | Dynamic lubricated |
|---|---|---|---|---|---|
| Steel | Steel | 0.5 | 0.1 | 0.4 | 0,1-0,05 |
| Steel | Cast iron | 0.2 | 0.1 | 0.18 | 0,1-0,05 |
| Steel | Cu-Sn alloy | 0.2 | 0.1 | 0.1 | 0,06-0,03 |
| Steel | Pb-Sn alloy | 0.15 | 0.1 | 0.1 | 0,05-0,03 |
| Steel | Polyamide | 0.3 | 0.15 | 0.3 | 0,12-0,03 |
| Steel | PTFE | 0.04 | 0.04 | 0.04 | 0.04 |
| Steel | friction lining | 0.6 | 0.3 | 0.55 | 0,3-0,2 |
| Steel | Wood | 0.55 | 0.1 | 0.35 | 0.05 |
| Wood | Wood | 0.5 | 0.2 | 0.3 | 0.1 |
| Cast iron | Cu-Sn alloy | 0.25 | 0.16 | 0.2 | 0.1 |
| Rubber | Cast iron | 0.5 | 0.45 | ||
| Rolling element | Steel | 0,003-0,001 | |||
| Aluminum | Aluminum | 1,05-1,35 | 0.3 | 1.4 | |
| Aluminum | Mild steel | 0.61 | 0.47 | ||
| Brass | Cast iron | 0.3 | |||
| Bronze | Cast iron | 0.22 | |||
| Cast iron | Cast iron | 1.1 | 0.15 | 0.07 | |
| Copper | Stainless steel (304) | 0.23 | 0.21 | ||
| Glass | Glass | 0,9-1 | 0,1-0,6 | 0.4 | 0,09-0,12 |
| Glass | Metal | 0,5-0,7 | 0,2-0,3 | ||
| Graphite | Graphite | 0.1 | 0.1 | ||
| Graphite | Steel | 0.1 | 0.1 | ||
| Nylon | Nylon | 0,15-0,25 | |||
| Polystyrene | Polystyrene | 0.5 | 0.5 | ||
| Polystyrene | Steel | 0,3-0,35 | 0,3-0,35 | ||
| Steel | Brass | 0.35 | 0.19 | ||
| Mild steel | Brass | 0.51 | 0.44 | ||
| Mild steel | Cast iron | 0.18 | 0.23 | 0.13 | |
| Teflon | Steel | 0.04 | 0.04 | 0.04 | |
| Titanium Alloy | Aluminium Alloy | 0.41 | 0.38 | ||
| Titanium Alloy | Titanium Alloy | 0.36 | 0.3 | ||
| Titanium Alloy | Bronze | 0.36 | 0.27 |
The friction coefficient depend on several factors: contact pressure, surface roughness, temperature, sliding velocity, type of lubricant and level of contamination.
Static coefficients of friction are higher than the dynamic or kinetic values.
DIN 76-1
For fine threads the dimension of the thread runout is chosen according to the pitch P.
1)As a general rule, apply if no other entries are given.
2)IApply if a shorter thread runout is necessary.
3)Apply if a longer thread runout is necessary.
DIN 6885
The length of the pipe is from the compressor to the farthest point.
– For a closed ring the diameter can be reduced by 29%.
– For pressed stainless steel pipe reduce the diameter by 6%
– For aluminum pipes reduce the diameter by 9%.
– Frequent loss of pressure 0.1-0.3 bar
– A maximum pressure loss of 0.1 bar is recommended.
A loss of pressure of 0.4 bar or higher is not profitable.
0.4 bar of pressure loss supposes an additional 3% of consumption.
Compressed Air Pipe Lines – Recommended Size Engineering Toolbox
TLV A steam specialist company
