tag:blogger.com,1999:blog-39476353752426204612012-01-30T19:12:50.382+07:00Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-3947635375242620461.post-77510350227421961482010-12-18T08:04:00.002+07:002010-12-18T08:08:27.091+07:002010-12-18T08:08:27.091+07:00

Instrument engineer usually finds term ‘accuracy’ in some catalog and ‘inaccuracy’ in some others. To know whether there is a difference between both of them, try to understand the meaning of each.The accuracy of an instrument is a measure of how close the output reading of the instrument to the correct value. Inaccuracy does mean similar i.e. the degree to which a measurement might be error

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com0tag:blogger.com,1999:blog-3947635375242620461.post-54227315161558582252009-10-19T18:53:00.010+07:002009-10-19T19:36:04.282+07:002009-10-19T19:36:04.282+07:00

Orifice, combined with differential pressure transmitter, is the mostly used flow measurement device in oil & gas plant because of low cost and its ease of installation and maintenance. However, orifice only allows 3:1 rangeability to maintain accuracy. This means, if one wants to measure maximum flow of 10 MMscfd, then the minimum flow measurement that could be measured is only 3.3 MMscfd.

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com0tag:blogger.com,1999:blog-3947635375242620461.post-567897913944721432009-06-02T17:14:00.003+07:002009-06-03T13:11:21.195+07:002009-06-03T13:11:21.195+07:00

During designing an actuated valve, instrument engineer shall concern to valve safety factor which is a ratio between “torque produced by an actuator” to “torque required by a valve to actuate when changing position” (close to open or vice versa). Valve and actuator commonly obtained from different manufacturer, therefore it is a responsibility of instrument engineer to ensure that combination of

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com5tag:blogger.com,1999:blog-3947635375242620461.post-25707750818604200152008-10-04T10:45:00.004+07:002009-06-03T13:16:38.104+07:002009-06-03T13:16:38.104+07:00

Energized to safe mode works as contrary to that of de-energized to safe. In energized to safe mode, no electrical current flows through the instrument loop during plant normal condition. Loop will be energized during plant upset. For illustration, see below picture of a simple unit consisting push button (PB) and solenoid valve controlling a deluge valve (XV). During

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com4tag:blogger.com,1999:blog-3947635375242620461.post-27702512924588946792008-09-22T13:02:00.014+07:002011-08-02T06:03:00.541+07:002011-08-02T06:03:00.541+07:00

Electric based Instrument loop on plant operate in two modes: either energized to safe or de-energized to safe. De-energized to safe mode, also known as fail safe system means that during plant normal condition, there will be electrical current flows through the instrument loop. When trip/shutdown is required, the loop will be de-energized. See illustration on below picture of a simple unit

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com0tag:blogger.com,1999:blog-3947635375242620461.post-68333976309253044152008-09-17T16:19:00.001+07:002008-09-17T16:22:01.353+07:002008-09-17T16:22:01.353+07:00

Two most common temperature instruments used in process industry are RTD and thermocouple. To determine which one to use, the following should be considered:RTD is preferred if one of the following aspects becomes a concern in measurement: Accuracy, Stability, Sensitivity and Linearity.Thermocouple is preferred in application for high temperature measurement (more than 400 degC) or when exposed

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com0tag:blogger.com,1999:blog-3947635375242620461.post-68051185836638465632008-09-09T13:18:00.004+07:002008-09-19T14:44:59.783+07:002008-09-19T14:44:59.783+07:00

Sizing of instrument cable should be performed to ensure that instrument device such as solenoid valve and its cabling works properly. There are two factors that should be checked i.e. voltage drop and current carrying capacity.Voltage drop is calculated as follows:Vdrop = [Rio + (Rw x 2L) + Rins] x Inwhere:Rio = Input resistance of I/O Card (Ohm)Rw = Resistance of wire at specified temperature

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com1tag:blogger.com,1999:blog-3947635375242620461.post-41992319651593652352008-09-04T16:23:00.004+07:002010-06-08T06:53:01.882+07:002010-06-08T06:53:01.882+07:00

When solenoid valve is losing power (de-energized) due to shutdown or other reason, it will actuate to its normal position. On regular solenoid valve, it can be put back to operating condition by energizing the solenoid. While on solenoid valve with manual reset, it will not be so. After being energized, it should be manually resetted prior back into normal operation. So it works like a local

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com3tag:blogger.com,1999:blog-3947635375242620461.post-55091227128437087572008-08-26T15:45:00.015+07:002008-09-30T19:55:25.314+07:002008-09-30T19:55:25.314+07:00

There are two fails which are widely known in safety system. The first one is called a nuisance fail which does not put the plant system in danger. In fact some nuisance fails will result in spurious trip or unnecessary plant shutdown therefore they cost high as the production stops. The second one is fail danger which is undetected and does not cause a process shutdown. However, if there is an

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com2tag:blogger.com,1999:blog-3947635375242620461.post-34238505363269909372008-08-20T14:10:00.016+07:002009-01-09T14:21:17.630+07:002009-01-09T14:21:17.630+07:00

Actuated valve, also referred as shutdown valve, blowdown valve, on-off valve, mainly comprises of valve body and actuator. Here are several accessories that make actuated valve complete.1. Solenoid ValveComprises of a solenoid and a valve which form is usually a three-way valve. Solenoid converts electrical energy to mechanical energy resulting three-way valve changes its state.Here is one

Instrumentcontrolhttp://www.blogger.com/profile/17761828846501234355noreply@blogger.com9