The Gas Constant, R, in Various Units

R is the gas constant in the ideal gas equation




pV = nRT



R is related to the Boltzmann constant, k, by



R = k _ NA



where k = 1.3806 x 10-23 J K-1, and NA = 6.022 x 1023 mol-1



R with different units



8.31451 J K-1 mol-1



8.20578 x 10-2 L atm K-1 mol-1



8.31451 x 10-2 L bar K-1 mol-1



8.31451 Pa m3 K-1 mol-1



62.364 L Torr K-1 mol-1



1.98722 cal K-1 mol-1



The Gas Constant, R, in Various Units

TYPES OF VALVES

Types of
Valve

Angle Valves: Metallic angle valves in
material such as stainless steel, bronze, brass are used for cryogenic
applications requiring extreme temperatures, ranging from 450º to -250ºC.

Types of Angle Valves

•   Manual

•  Pneumatically

•  Air to open/spring to close

• Motorized

Application of Angle Valves

Angle Valves are widely used in commercial and industrial applications
such as:

     • Hot and cold water

• HVAC

• Steam

• Compressed air

• Gas and other general utility services

Globe Valves

•  Angle valves are a type of globe valves, so

designed, that the inlet and outlet are perpendicular, for transferring flow
from vertical to horizontal. Y-design valves derive linear action from
the incline between the axis of the inlet and outlet ports. The inlet and
outlet are not of single piece construction. These valves offer precise
throttling and control and have high-pressure limits. They also offer a low
coefficient of flow and are however not good selections in applications
requiring cleanliness or sterility.

     •  Types of Globe Valves

These valves are available in three main body types, namely : Angle Design,
Y-design and Multi-piece Design

Ball Valves:

•   These are wide duty valves, enabling transfer of gases,

liquids and liquids with suspended solids (slurries).

• Common ball

valve are available in materials including brass, bronze, copper, cast iron,
ductile iron, stainless and other steel types, metal alloys and plastics
including PVC and CPVC.

•  In contrast to other types of valves, ball

valves provide superior ease of operation and can maintain and regulate high
volume, high pressure and high temperature flow and often offer rugged
construction providing for a long service life, and a comparably low cost.
These specialty valves are available in a variety of configurations for
positive leak tight shut-off and control and are used for both manual as well
as remote valve actuation.

•  The popular and standard configurations include:

• Miniature

• 2-way

• 3-way

• Swing-out

• Spring-loaded

Butterfly Valves

•   Butterfly valves are throttling valves used to control

flow through a circular disc by turning the valve’s main axis at ninety degree
or right angles towards the direction of flow in the pipe. These valves use an
inflatable seat to seal with air pressure, thus requiring less torque and a smaller
actuator, resulting in lower overall valve cost.

•  The demand for actuated butterfly valves is

growing because actuated butterfly valves can provide: precise, repeatable
control for industrial process, complex automatic sequencing for process
control. These important industrial fittings control the flow of gas or liquid
by means of a disk, which turns on a diametrical axis inside a pipe or by two
semicircular plates hinged on a common spindle, which permits flow in a single
direction. These compactly designed valves offer a rotary system movement of
less than 90 degree. The valves are manufactured in materials including
stainless steel, plastic, ceramic and PVC.

• Advantage of Butterfly Valves

These valves can be used in areas where space is limited, this is so, because
butterfly valves are available in small dimensions and are used in a variety of
chemical services.

Needle Valves:

• Needle valves are kind of throttle valves, similar in

operation and designing of globe valves. These valves have a slender, tapered
point at the end of the valve, which is lowered through the seat to block flow.
These valves are used to control flow into delicate gauges, which might be
damaged by sudden surge of fluid under high pressure and also to control the
end of a work cycle.

•  Needle valves are available in stainless steel,

bronze, cast iron etc depending on the kind of application and are designed with
a metallic needle in materials including brass, bronze, stainless
steel, along with seat generally made form PVC, CPVC, PTFE etc. Needle valves
are normally manually operated, but can be modified to act as a variable
restrictor. These valves are available in different types of end connections
including double ferrule type, NPT, BSPT and many other standard connections
and in various packing materials for different applications depending on
requirements, temperature and medium to be moved.

• Application of Needle Valves

•  Aerospace

• Zoological science

• Gas and liquid dispensation

• Instrumentation control

• Power generation

Gate Valves

•  Gate valves, also known as Slide or Knife Valves, are

named after a wedge-shaped internal plastic barrier, called a gate which rises
and falls inside the valve as a handle is turned. These are linear motion
valves in a which a flat closure element slides into
the flow stream to provide shut off and are designed to minimize pressure drop
across the valve in the fully opened position and stop the flow of fluid
completely.

• Knife valves effectively regulate flow rates

from zero to full flow, they work well with solids-laden water, and these
valves can be serviced in place. Knife Gate valves work well in applications involving
slurries as the ‘gates’ can cut through the slurry, also these valves are
advantageous in applications involving viscous liquids such as heavy oils,
varnish, molasses etc.

• Types of Gate Valves

• Parallel Gate Valves: These valves use a flat

disc gate between two parallel seats located upstream and downstream.

• Wedge-Shaped Gate Valves: These valves use two

inclines seats and a little mismatched inclined gate allowing tight shut-off.

• Application of Gate Valves

• Viscous liquids such as heavy oils, creams etc.

• Slurries

Check Valves:

• A check valve is a mechanical device used as an industrial/plumbing fitting, which normally allows fluid or gas to flow through it in uni-direction. A double check valve is often used to prevent back flow and to keep potentially contaminated water from siphoning back. Clapper valves, a type of check valve is used in or with firefighting, and has a hinged gate (often with a spring urging it shut) that only remains open in the outflowing direction.

• Types of Check Valves

• Single Disc Swing Valves : These valves can be mounted both vertically as ell as horizontally and are designed with a closure element attached to the top of the cap. This closure element can be pushed aside by the flow, but swings back into the close position upon flow reversal.

• Double Disc or Wafer Check Valves : These valves consist of two half-circle disks hinged together that fold together upon positive flow and retract to a full-circle to close against reverse flow.

• Lift-Check Valves : These valves can operate in either vertical or horizontal mounting.

• Silent valves : These valves are quite similar to lift check valves with a center guide extending from inlet to outlet ports.

• Ball-Check Valves : These valves are good for most services and can even handle fluids that produce gummy deposits. Since the disc is free to rotate, this all helps to keep the valve seats clean.

• Cone Check Valves : These valves use a free-floating or spring loaded cone resting in the seat ring as the closure element. Incase of a reverse flow, the cone is forced back into its seat preventing back flow.



Application of Check Valves

• Few types of irrigation sprinklers and drip irrigation emitters have small check valves built into them to keep the lines from draining when the system is shut off.

• Offshore Oil and Gas

• Civil Engineering

• Gas-Turbine Systems

Pressure Relief Valve:



• A pressure relief valve is a device mounted on a hot water heater or boiler and is designed to release any high steam pressure in the tank and thus prevent tank explosions.

• These specialty valves are used for systems that contain gases and liquids in a variety of pneumatic, hydraulic, and cryogenic applications to provide protection from over-pressure in steam, gas, air and liquid lines.

• The working involves letting off the steam when safe pressure level is exceeded and then closing of the valve after the pressure level drops to the preset level; Back pressure regulating valve helps to maintain upstream pressure at the desired level by allowing excess upstream pressure to flow downstream. These self-operating valves are installed to prevent over pressurization of the system.

• Application of Pressure Relief Valve

• Petrochemicals

• Pneumatic equipments

• Hydrocarbons

• Chemical Processing

Control Valves:



• A Control Valve is an important industrial fitting device used to modify and control the fluid flow rate in a process system. Also known as proportional valve, this power-operated device can be used to modify pressure rate in a process system.

• Available in choice of material including copper, brass, bronze, cast iron and stainless steel, and other plastic material such as PVC AND CPVC, these valves are the most used fittings.

• Types of Control Valves

Globe, Gate, Diaphragm, Needle, Butterfly, Ball and Plug Valves are all, kinds of control valves and are used for different applications in large number of industries

• Application of Control Valves

• Waterworks

• Fire Protection

• Irrigation

• Industrial

• Petroleum

• Aviation Fueling

Y-Strainer:



• Y-Strainer are special devices, used for mechanically removing solids from flowing liquids or gases by using a perforated or wire mesh straining element/equipment.

• These strainers are used in pipelines to protect equipment such as pumps, meters, control valves, steam traps and regulators.

• These strainers are generally used where the amount of material to be removed is small and when frequent straining is not needed.

• Y type strainer are widely used for handling steam, these compact and cylindrically shaped strainers are very strong and can handle high pressures.

• These strainers can be installed both horizontally as well as vertically. Cast iron, bronze, carbon steel, or stainless steel are the common materials used to manufactured these specialized strainers. Iron is most widely used because it costs the least.

LINE SIZING CRITERIA FOR VAPOR LINES

• Single-phase gas lines are normally designed based on the velocity criteria as specified in API 14E.
• The maximum recommended design velocity is 18 m/s,though higher velocities are also acceptable.
• Some  operating companies prefer to use (density*velocity^2) criteria.

          Operating pressure(gauge)                                                       (density*velocity^2) criteria
              P < 2000 kPa                                                                                   7,500 kg/m-s2

           2,000  < P < 5000 kPa                                                                        9,500  kg/m-s2

          5,000  < P < 8000 kPa                                                                        12,500 kg/m-s2

               P < 8000 kPa                                                                                 20,000 kg/m-s2

• COMPRESSOR DISCHARGE LINES                                                  VELOCITY
  

             P < 500 kPaG                                                                                    30 m/s

           500  < P < 1000 kPaG                                                                        30 m/s

          1,000  < P < 5,000 kPaG                                                                     30  m/s

               P < 5000 kPaG                                                                                30  m/s

•  COMPRESSOR SUCTION LINES   velocity is 20 m/s.    

• LINE SIZING CRITERIA FOR TWO-PHASE FLOW

 Maximum allowable velocity calculated for two phase-flow based on empirical relationship of erosion velocity.

                                       Erosion velocity=  C / density of two phase


 The value of empirical constant C is as follow:
      Type of service                                                                                    Value of 'C'

Continuous service                                                                                     122

Intermittent service                                                                                    152

For solid-free fluid where corrosion is not anticipated,or when corrosion is controlled by inhibitor , the value of C from 183 to 244 may be used for contentious flow, and value up to 305 can be used for intermittent service.

• RELIEF VALVE INLET LINE SIZING

           The inlet line to the relief valve is designed for a maximum pressure drop of 3 % of the relief valve set pressure.However the inlet line size should not be smaller then the inlet flange of the relief valve.

• RELIEF VALVE OUTLET LINE SIZING                                  
  

  The outlet line from the relief valve is designed based on the Mach number.Generally Mach number  in between 0.5 - 0.75 is maintained.However outlet line size should not be smaller then the outlet flange size of the relief valve. 
For calculating the velocity of sound at operating condition follow the link:

http://www.engineeringtoolbox.com/speed-sound-d_519.html

• LINE SIZING CRITERIA FOR GRAVITY FLOW LINES 

Normally, for gravity flow a slop of 1:100 is maintained ( 0.597degree) . For gravity flow, line with dimeter 200mm or less is designed for 50% liquid capacity and for a diameter more ten 200 mm, 75% capacity.
  

• DOWN PIPE SIZING

Down pipe sizing is an interesting  sizing requirement, particularly used to design distillation column internals.For distillation column the downpipes is designed in such a way that the pipes are self venting,i.e,while the liquid flows downward in the pipe, it disenggages the vapour which flow upward.
This type of downpipe is designed for a Froud number <0.3 .
  
If Froud number is < 0.3 , then the liquid flow will be self venting.
  
For  Froud number 0.3-2.0 ,the pipe will be full of liquid, with some possibility of vapor ingress at top of the pipe.
  
For Froud number > 2.0 , liquid will only flow through the pipe, and vapor diengagement sould occur before any liquid enters the downpipes. 

  Froud number = V/( ( g*D* (dl-dg)/dl)^0.5


where        g = 9.8 m/s
                  D= diameter of pipe,m
                 dl= density of liquid,kg/m3
                 dg= density of gas,kg/m3
                 V= velocity of fluid,m/s

or you can calculate the Froud number by following link:
http://www.engineeringtoolbox.com/froude-number-d_578.html





 

LINE SIZING VELOCITY CRITERIA

LINE SIZING CRITERIA FOR LIQUID( HYDROCARBON AND OTHER ORGANIC LIQUIDS) LINES( carbon steel):In the Pump suction line sizing the safe velocity is 0.3-0.9 m/sec.for non boiling liquids and 0.3-0.6 m/sec for boiling liquid.
pump dischrge side line sizing velocity 1.2-2.7 m/sec. if the discharge side line is short length, for long length velocity criteria is 0.6-0.9 m/sec.

LIQUID FROM CONDENSER : 0.9-1.8 m/s          
REFRIGERATION LINE    : 0.6-1.2 m/s
GRAVITY FLOW LINE     : 0.9-2.5 m/s
REBOILER INLET        : 0.3-1.2 m/s
LIQUID FEED TO TOWER  : 1.2-1.8 m/s

WATER                                
General service      :0.6-1.5 m/s     
Pump discharge        :0.6-4.9 m/s
Boiler feed           :2.5-4.5 m/s
Cooling water         :3.6-4.8 m/s
caustic solution      :1.2-1.6 m/s
Viscous Oil
Pump suction :0.2 m/s
Pump discharge :0.3-0.9m/s

For reference for above writeup follow the link :

http://books.google.co.in/books?id=LlBbRckWAeQC&lpg=PA137&ots=x4yEU5vZBB&dq=line%20sizing%20criteria&pg=PA136#v=onepage&q=line%20sizing%20criteria&f=false

Excel sheet for Entrainment check for Horizontal separator