References

References

Frequently used formula or conversion:

Celsius = 5 x (Fahrenheit-32) / 9
Fahrenheit = 32 + 1.8 Celsius

1 British thermal unit per hour (BTU/H) = 0.2931 watts
1 US refrigeration ton (USRT) = 3.517 kilowatts = 3,517 watts
1 USRT = 12,000 BTU/H
  
1 UK gallon = 4.546 liters
1 US gallon = 3.785 liters

1 bar = 100 kPa = 14.5 psi = 750 mmHg = 0.987 atm = 1.02 kgf per square cm

1 square cm per second = 1 stoke = 100 centistoke (cstoke)

Lag time calculation formula:

The sample must be transported from the sample tap to the analyzer, a distance that may vary from 1.5m to 120m, although 60m is usually the maximum desired length. Response time is a function of flow rate and internal volume of the system. Flow rate of the sample will depend on the differential pressure available, on the fluid gravity and viscosity and on the tubing size. Compressibility of gases must also be considered. For gas samples, the following equation can be used to determine the transport time in sample tubing (most designs employ flow rates between 2,000ml/min, or 60LPM (liter per minute):

t = [LV/F] x [(P+15)/15] x [530/(T+400)] = [530LV(P+15)] / [15F(T+400)]

Where: t = transport time (min), L = tubing length (ft), V = tubing volume (ml/ft), P = system average pressure (psig), F = flow rate (ml/min), T = system average temperature (deg F)

(Source: Bela G. Liptak & Kriszta Venczel, "Instrument Engineers' Handbook", P625)

Hazardous area guide:

Before using any electrical equipment in a hazardous area or potentially explosive atmosphere, it shall be fully tested and certified by an independent authority such as BASEEFA in the UK or UL in the USA (Source: http://www.medc.com/). More details are at a click remote thanks to MEDC.

Class I Flammable Gases:

Group A: acetylene

Group B: hydrogen

Group C: cyclopropane, ethyl-ether, ethylene,

Group D: acetone, alcohol, benzene, benzol, butane, gasoline, hexane, lacquer, naphtha, natural gas, propane, solvent

Process analyzer basics:

(Source: Andrew, W. G., "Applied Instrumentation in the Process Industries", Gulf Publishing Company)

1. What is a process analyzer? it is defined as an unattended instrument that continuously monitors a process stream for one or more chemical components.

2. What is the difference between lab and process analyzers? Most process analyzers operate on the same basic principles as their lab counterparts but with the addition of mechanism and circuitry to perform the required analysis unattended and to present resulting data as desired. In addition, process analyzers must be housed both to comply with electrical standards and for protection from weather and physical abuse.

3. How to classify the process analyzers? The process analyzers may be classified in various ways depending upon the purpose of the classification. Some classifications are made (a) by operating principle (infrared, ultraviolet, chromatographic, etc.), (b) by type of analysis (oxygen, carbon dioxide, etc.).