Installations of Field Instruments

1. Temprature Transmitter
2. Massflowmeter
3. Control Valve
4. Conductivity Analyzer

IEC 60529, 2nd edition describes the ratings for enclosure Ingress Protection (IP) covering water, foreign objects and access to hazardous parts. The IP rating has been in use in Europe and other countries outside of North America for many years, and has just recently been added to the Canadian Electrical Code (for hazardous locations). They are similar in intent to the NEMA ratings but there is no direct relationship. These ratings are widely used on portions of enclosures and components, as well as complete enclosures.


In North America, the common practice has been to use NEMA enclosure ratings for both water and dust resistance. As the name suggests, these standards were originally developed and published by the National Electrical Manufacturer’s Association (NEMA) and have been adopted by UL, CSA and other standards bodies in North America. International Standards use the IEC IP ratings instead of the NEMA ratings.


For example, 61010-1 and 60950 uses these requirements for ‘Protection Against Liquids’. Typically these standards reference IP X0 where the ‘X’ indicates that there is no rating for entrance of objects or dust. The ‘0’ indicates that there is no protection against water.


The IP rating is written as IP followed by the 1st and 2nd characteristics optionally followed by letter qualifiers. The qualifiers are rarely used and are beyond the scope of this article. Typical markings with their meaning:


IPX0 – Protection against entry of objects and prevention of touch not rated, no protection against entry of water. This is the most common rating.


IP2X – Protection against solid objects up to 12.5mm and accidental touch by fingers, no rating for protection against water.


IPX5/IPX7 – Dual rating indicating protection against jetting water and temporary immersion.


Cross Reference to NEMA

There is no direct relationship to these ratings but some guidance can be gained from the following table.

NEMA Rating Equivalent IP ‘Water’ Rating

outdoor equipment is IP56. The ‘5’ for limited ingress of dust is not much of a problem but the ‘6’ requires a well gasketed enclosure. Remember that the jet of water is 12.5mm (1/2”) in dia. with sufficient volume to fill a 3.5 cu. ft. volume in one minute. It doesn’t sound like much but the stream of water at 3m distance has only dropped a few centimeters. Because of the pressure it will enter enclosures that will stay dry inside even when immersed in water!

For IP ratings concerning ‘Protection Against Solid Objects’ and ‘Protection of Persons’, any lower rating than the one obtained is considered to be covered. For example, if you have a rating of 5, all ratings from 1 to 4 are also covered without additional testing. For ingress protection against water, the jetting water ratings are separate from the immersion ratings. A rating of 6 will cover you for ratings 1 to 5 but ratings of 7 or 8 are separate.

We strongly recommend that you purchase a copy of IEC 60529 if you have any equipment that needs to meet ingress protection specifications. This is particularly true for the water ingress tests.

The table on the next page summarizes the important ratings and the basic tests required.

NEMA Rating Equivalent IP ‘Water’ Rating

1 0
2 2
3,3X 3
4,4x 6
6 7
6P 8
IP (1st)
Meaning for Protection of Equipment Against Solid Objects
Tested by

(See Note)
Meaning for Protection of Persons (Protected Against Access to Hazardous Parts)
IP (2nd)
Protection Against Water with Harmful Effects
Tested by
Meaning for Protection from water

0 No protection
None
No protection
0 No protection
None
None

1 Solid objects ³ 50mm
50mm dia. sphere applied with 50N force.
Accidental touch by back of hand
1 Vertically Dripping
Drip box for 10 min.
Falling drops of water, condensation

2 Solid objects ³ 12.5mm
12.5mm dia. sphere applied with 30N force.
Accidental touch by fingers
2 Dripping - 15° tilted
Drip box, 2.5 min. per side
Direct light streams of water, up to 15° from the vertical

3 Solid objects ³ 2.5mm
2.5mm dia. steel rod applied with 3N force.
Accidental touch by tool
3 Spraying
Oscillating tube ±60°, 10 min., 10l/min.
Direct sprays of water, up to 60° from the vertical

4 Solid objects ³ 1mm
1mm dia. steel wire applied with 1N force.
Accidental touch by small wire
4 Splashing
Oscillating tube ±180°, 10 min., 10l/min.
Water sprayed from all directions, limited ingress

5 Dust-protected (limited ingress, no harmful deposit)
Dust chamber with or without under-pressure.
Accidental touch by small wire
5 Jetting
6.3mm dia. nozzle from 2.5 to 3 metres distance,12.5l/min. for 3 min.
Low pressure water jets from all directions, limited ingress

6 Dust-tight (totally protected against dust)
Dust chamber with under-pressure.
Accidental touch by small wire
6 Powerful Jetting
12.5mm dia. nozzle from 2.5 to 3 metres distance,100l/min. for 3 min.
Strong jets of water, limited ingress


7 Temporary Immersion
Immersed in tank with water 0.15 m above top and 1 m above bottom. For 30 min.
Protected against the effects of temporary immersion in water

8 Continuous Immersion
Water-level and time as specified by manufacturer
Protected against the effects of continuous immersion in water

Note - For voltages not exceeding 1000Vac or 1500Vdc – no contact with hazardous parts. For higher voltages, must pass dielectric test specified for voltage.


Difference between dust tests for IP5X and IP6X


The dust test for IP5X and IP6X (dust rating of 5 and 6) is conducted in a dust chamber for 8 hours, with talcum powder (2kg per cubic metre of the test chamber) circulating, so it continually falls down onto the equipment under test. IP5X testing may be conducted either with or without underpressure - depending on the equipment category (see below). IP6X is tested with underpressure, regardless of the equipment category.


The following is a description of the two enclosure categories:


Category 1 Enclosures - Enclosures where the normal working cycle of the equipment causes reductions in the air pressure within the enclosure below that of the surrounding air, e.g. due to thermal cycling effects - if the equipment will or may be installed near a heater (or other heat source) which will cycle the temperature of the equipment.


Category 1 equipment must be tested with underpressure - which means that the enclosure will be maintained below the surrounding atmospheric pressure by a vacuum pump for the duration of the dust test.


Category 2 Enclosures- Enclosures where no pressure difference relative to the surrounding air is present.


For IP6X testing, the equipment is assumed to be Category 1- regardless of what it actually is. A pass for this test is only if NO dust is observed inside the equipment after the test.


IP5X testing can be conducted for either Category 1 or Category 2 type enclosures. A pass for this test (regardless of which category is used) is if the powder has not accumulated in a quantity or location such that it could interfere with the correct operation of the equipment or impair safety. IP (Extended Environment) Ratings for Equipment

What is a smart sensor?

One of the biggest advances in automation has been the development and spread of smart sensors. But what exactly is a "smart" sensor? Experts from six sensor manufacturers define this term.
A good working "smart sensor" definition comes from Tom Griffiths, product manager, Honeywell Industrial Measurement and Control. Smart sensors, he says, are "sensors and instrument packages that are microprocessor driven and include features such as communication capability and on-board diagnostics that provide information to a monitoring system and/or operator to increase operational efficiency and reduce maintenance costs."

No failure to communicate
"The benefit of the smart sensor," says Bill Black, controllers product manager at GE Fanuc Automation, "is the wealth of information that can be gathered from the process to reduce downtime and improve quality." David Edeal, Temposonics product manager, MTS Sensors, expands on that: "The basic premise of distributed intelligence," he says, is that "complete knowledge of a system, subsystem, or component's state at the right place and time enables the ability to make 'optimal' process control decisions."

Adds John Keating, product marketing manager for the Checker machine vision unit at Cognex, "For a [machine vision] sensor to really be 'smart,' it should not require the user to understand machine vision."
A smart sensor must communicate. "At the most basic level, an 'intelligent' sensor has the ability to communicate information beyond the basic feedback signals that are derived from its application." says Edeal. This can be a HART signal superimposed on a standard 4-20 mA process output, a bus system, or wireless arrangement. A growing factor in this area is IEEE 1451, a family of smart transducer interface standards intended to give plug-and-play functionality to sensors from different makers.

Smart sensors can self-monitor for any aspect of their operation, including "photo eye dirty, out of tolerance, or failed switch," says GE Fanuc's Black. Add to this, says Helge Hornis, intelligent systems manager, Pepperl+Fuchs, "coil monitoring functions, target out of range, or target too close." It may also compensate for changes in operating conditions. "A 'smart' sensor," says Dan Armentrout, strategic creative director, Omron Electronics LLC, "must monitor itself and its surroundings and then make a decision to compensate for the changes automatically or alert someone for needed attention."

Many smart sensors can be re-ranged in the field, offering "settable parameters that allow users to substitute several 'standard' sensors," says Hornis. "For example, typically sensors are ordered to be normally open (NO) or normally closed (NC). An intelligent sensor can be configured to be either one of these kinds."

Intelligent sensors have numerous advantages. As the cost of embedded computing power continues to decrease, "smart" devices will be used in more applications. Internal diagnostics alone can recover the investment quickly by helping avoid costly downtime.

Tutorial: Thermal mass flowmeters (insertion type) for gas applications

In our last issue, we began considering the problems of gas flow measurement, given the problems associated with its compressibility. Mass flow measurement approaches for gas are immune to this problem, and there are two main options: thermal and Coriolis. Thermal mass flowmeters are based on the understanding that a given mass of fluid will remove a known amount of heat from a given body. While some designs handle liquids as well as gasses, liquid applications are far less common for this sensor type.
Within the thermal mass flowmeter technology, there are two approaches: the in-line type and insertion type. We will consider the in-line type in a future issue. Insertion type sensors use a probe that is inserted through the pipe wall into the process gas line. The probe includes a heating element and multiple temperature sensors, typically RTDs. One sensor measures the temperature of the ambient gas stream. Another measures the temperature of the heating element.
A sensor uses one of two approaches. One feeds a specific amount of current into the heating element and calculates flow by measuring how much lower the actual temperature is than it should be for the amount of current. The other heats the element to a specific temperature, and calculates flow by measuring how much current it takes to maintain that temperature. The current levels and temperature differences provide the data to calculate mass flow. Most designs are relatively precise and offer accuracy in the ±2% or less range, along with wide turndown ratios. Since the sensor calculates a mass reading, the gas density must be known to convert to a volumetric reading.
This technology has some practical application considerations. (These are generalities, so discuss specifics with your supplier.)
--Since the design uses a heating element, it operates continuously (or at least with long on periods) at high power levels, so battery powering isn’t a practical option.
--Given the probe size, insertion designs are best with relatively large pipes and ducts.
--The nature of the measurement is for a small section of the gas stream. The normal practice is to place the sensing point in the center of the pipe and the final flow calculation is based on normal flow profiles for that size pipe. This means that the probe length has to be adjustable or fixed for a specific pipe size. It also means that turbulence has to be minimal, which calls for flow stabilizers or long sections of straight pipe up and downstream.
--Some probe designs depend on careful axial, or yaw, positioning. If the probe is twisted relative to the gas stream, the reading can be affected.
--For large ducts or where turbulence is unavoidable, some suppliers offer probes with multiple sensors. These take readings at a range of points across the flow profile and correct for poor gas distribution.
--Dirty and corrosive gas streams can leave deposits on critical surfaces and interfere with measurements or damage fragile sensing points. Some designs are more tolerant of these than others, so discuss these potential problems with your suppliers

ABB wins power order for world’s largest offshore wind farm

ABB, the leading power and automation technology group, has won an order worth more than $400 million from the German utility E.ON Netz GmbH to supply the power equipment that will connect the world’s largest offshore wind farm to the German grid.

ABB will connect the 400-megawatt (MW) Borkum-2 park using its innovative and environmentally friendly HVDC Light (high-voltage direct current) transmission technology, which gives utilities complete control over the power supply and increases grid stability. Located more than 100 kilometers off the German coast in the North Sea, it will be the most remote wind farm in the world.

“Linking renewable sources of power to the grid can be challenging due to environmental conditions and the distance involved,” said Peter Leupp, head of ABB’s Power Systems division. “This project highlights how renewable power sources can be integrated to help combat climate change.”

Scheduled to be operational in September 2009, the wind farm is expected to avoid CO2 emissions of 1.5 million tons per year by replacing fossil-fuel generation. Germany currently uses wind for about 7 percent of its electricity requirements and expects to double the share of wind energy by 2020.

ABB is responsible for system engineering including design, supply and installation of the offshore converter, sea and land cable systems and the onshore converter. Most of the transmission system provided by ABB will be laid underwater and underground, thus minimizing environmental impact.

HVDC Light offers numerous other environmental benefits, such as neutral electromagnetic fields, oil-free cables and compact converter stations, and is ideal for connecting remote wind farms to mainland networks without distance limitations or constraints on the grid.