Orifice plate flowmeters - Spirax Sarco International

1 Orifice plate flowmetersfor steam, liquids and gases2In many of today s industrial processes, it is essentialto measure accurately the rate of fluid flow within asystem as a whole or in part. This applies equally togases and liquids ( carbon dioxide, nitrogen, liquorsetc.) which are an integral part of the process, or tocompressed air, water or steam which are fundamentalto plant operation. The installation of any flowmetercan be justified in one of two ways:1. Process controlHere the flowmeter is used to measure the rate of fluidor energy flow to allow the process to be controlled andso ensure that the end product is of the requiredquality.

2 A common example of this would be in steaminjection systems for the animal feeds steam and the product will not littlesteam and the raw materials will not process and maydamage the production Cost allocationWhere energy is used to provide process or spaceheating, it is fundamental to know where the costsassociated with the energy are actually being allows energy costs to be allocated to aparticular product, department or other user this usuallyresulting in a significant reduction in total energy flow allows you to:-Improve process controlAllocate heating costsIdentify major energy usersMonitor the results of process changesCheck on steam boiler efficiencyIdentify energy patterns through the dayProvide management informationLord Kelvin once said: When you can measure what you are speaking aboutand express it in numbers, you know something aboutit; but when you cannot measure it, when you cannotexpress it in numbers, your knowledge is of a meagreand unsatisfactory kind.

3 In other words, you cannot manage what you cannotmeasure and nowhere is that more true than in themeasurement of handledorifice plateUpstreampressure tappingFlowRate of flow kg / hHours elapsedFlowrateCumulative errorActual systempressure012345 61 0008006004002000 Why measure flow?3 How do Orifice plates work ?An Orifice plate installed in a line creates a pressuredifferential as the fluid flows through it. This differentialpressure is measured via impulse lines by a differentialpressure transmitter which converts it into an analogueor digital signal which can be processed to provide adisplay of the instantaneous rate of flow.

4 Therelationship between the rate of flow and the differentialpressure produced is very well understood and is fullycovered by comprehensive national standards. Therelevant standards are BS 1042 and the equivalentISO 5167. One of the principle advantages of orificeplates manufactured and installed following thesestandards is that they do not require calibration. Thismeans that Orifice plates are very cost effective onlarger line use Orifice plates?hPCarrier plate forclamping betweenflangesDownstreampressure tappingOptionaldrain holeCumulative error kgPressure bar gDensity compensationWith liquid metering systems, the flowing density is usually fairly constant and relativelysimple processing of the output signal from the differential pressure transmitter is usuallyall that is , it is rare for the pressure in steam systems to remain absolutely this is taken into account, flow measurement errors will occur.

5 By using theautomatic density compensation capability of the Spirax Sarco M240G Steam FlowComputer, these errors are completely eliminated allowing accurate steam meteringwhatever the steam : A simple non compensated flowmeter is set for 6 bar g. The actual pressure inthe system varies through the day and unless this is allowed for, by the end of the day,very significant errors can arise. This is typical of many steam 5002 0001 5001 0005000 Orifice plates are still the most widely used type offlowmeter in the world today. They offer significant costbenefits over other types of flowmeter , especially inlarger line sizes, and have proved to be rugged, effectiveand reliable over many years.

6 Where a need exists for arugged, cost effective flowmeter which has a lowinstallation cost and a turndown of not more than 4:1,the Orifice plate continues to offer a very benefits All items available from a single Sarco Orifice plate flowmeters - the system M240 GSteam flowcomputerOutputsAlarms unitEL2271 TemperaturetransmitterFlowM610DP transmitterassemblyM410 Orifice plateassemblyEL2600 PressuretransmitterF50C IsolationvalveNote: Configuration shownhere is for steam. Gas andliquid installations will plates are amongst the most simple and easy to use type of flowmeter .

7 However, in order to get the verybest out of them, it is essential to ensure that the user specifies a complete system that meets his too often, factors such as the need for density compensation are not fully specified by the user with the resultthat the full potential of the Orifice plate primary element is not achieved. Frequently, it is necessary to sourceitems from several different manufacturers and hope that the components will be Sarco has completely eliminated this by introducing a range of Orifice plate based flowmetering systemssuitable for use on steam, liquids and gases.

8 One of these systems will be ideal for your application. Select thesystem that is best suited for your needs from the 14 options available then decide on the display for simple non compensated applications or the M240G steam flow computer for the ultimate insteam flow measurement capability. Spirax Sarco can advise, if necessary, which is the best system for anyapplication. Wide range of sizes from DN25 up to DN600. Available to suit most flange specifications. Spare plates available. All Orifice sizing calculations carried outby Spirax Sarco to BS 1042 / ISO 5167.

9 Systems available for steam, liquids and gases. A complete range of systems available for that makes it simpleStep 1 Choose the Orifice plate optionStep 3 Choose the pressure transmitter for applicationswhere the line pressure variesStep 2 Choose the differential pressure transmitterWhere pressure and / or temperature varies then it is necessary to compensate for density variations andthe following options should be considered:-M410 tab handled Orifice plateto BS 1042 / ISO 5167 completewith gaskets .. designed to beclamped between the user'sown flanges, this is thesimplest Orifice plate , gaskets.

10 Carrier ring with the addition oftwo F50C isolation valves toprovide primary pressure accuracy M610differential pressure transmitterfitted with a three-way manifoldfor isolation and 45678 9 10 11 12 13 141234567891011121314lllllllEL2271 temperaturetransmitter for linetemperatures up to 250 CEL2270 temperature sensorand separate EL2810temperature transmitter fortemperatures above 4 Choose the temperature transmitter for applicationswhere the line temperature variesllll5 6 7 8 9 10 111213 14llllllllllllllllllllll5 6 7 8 9 10 111213 14 Example: Option 7 would include 1 x M410, 1 x M610, 1 x EL2270 and 1 x all flowmeters need certain lengths of straight,uninterrupted pipe upstream and downstream of theflowmeter itself, and Orifice plates are no exception.