Saturated steam is a vapor and it doesnt behave as a gas.

Superheated steam behaves like a gas

First law of thermodynamics: Energy cannot be created or destroyed but may be converted from one form to another.

Second: no machine actual or ideal, can both continuous and completely transform heat into mechanical energy. Nothing is 100% efficient.

Heat is energy caused by molecular activity.

Temperature is the degree or intensity of heat

Radiation: heat transfer by light waves without a material carrier. (warming up by a fire)

Convection: Heat transferred by currents in a fluid (boiling water in a pot)

Conduction: heat transferred molecule to molecule (like a metal rod in a fire)

F = (1.8 C) + 32

Rankine = degF + 460

Kelving = degC + 273

What is the density of steam @40 psia?

its the reciprocal of specific volume, the opposite.

you divide the specif volume by one.

British Thermal Unit

The amount of heat required to raise the temperature of 1lb of water 1degF.

The amount of heat required to raise the temperature of 1lb of any substance 1degF.

the specific heat of water is 1.0

this is why in generation industry, they use hydrogen as cooling for generators. Hydrogen has a higher specific heat

Mostly used on fuels, is the weight of any substance when compared to the weight of water.

the specific gravity of water is 1.0 at 39.2degF.

water = 8.33 lbs/g x .84

= 6.99 lbs/gal

you compare the specific gravity of the fluid to the specific gravity of water (1.0), 1 gallon of water = 8.33lbs

-Is the volume of any substance when compared to the volume of water.

-only applies to steam and water

-when water is heated its density decreases; when water is cooled its density increases.

Critical pressure =  3206.2 psia

At critical pressure, steam and water have the same density, latent heat = 0, so water becomes steam without any added heat

705.4degF

It is the max saturation temp. It is the hotterst you can get water.

-459.6degF

-At absolute zero temp., there is no molecular motion (no heat), a perfect gas has zero volume and entropy (how we measure the loss in any process) is equal to zero.

-Absolute zero pressure is a perfect vacuum, does not exist on earth (second law of thermodynamics, no system is 100%)

When the temp. is help constant (isothermal), the volume of a given weight of gas varies inversely as the absolute pressure.

P1V1 = P2V2

1- When the pressure of a given weight of gas is held constant, the volume will vary directly as the absolute temp.

constant pressure, vol. vary directly as temp.

V1/V2 = T1/T2

2- if the volume is held constant, the absolute pressure will vary directly as the absolute temperature.

constant volume, pressure vary directly as temp.

P1/P2 = T1/T2

all in absolute pressure, so add 460 to degF for degR

Equal volumes of all gases at the same pressure and temperature contain the same number of molecules.

This law was made to determine absolute 0.

491.6 below melting point of ice

Represents an ideal cycle, good starting point for actual cycle efficiency.

(T1 - T2) / T1

Proves that the use of steam for work results in losses due to the inability to utilize the latent heat.

Proves that superheat and reheat improve overall plant efficiency.

Er = (h1 - h2) / (h1 - h3)

h1 = initial condition (turbine inlet)

h2 = isentropic expansion (exhaust)

h3 = final liquid conditions (condesante)

Rankine gave the reality that steam turbines are only 25% effiecient.

-Condensing improves the heat drop thru the turbine.

-In a condensing steam turbine, all the loss is in the steam going to the condenser, so by adding steam extract points  for a feedwater heater for example, u can reduce this loss.

-superheat, air preheaters and economizers raise the initial steam temp.

-Reheat increases the initial steam temperature after the steam has performed work.

-Regenerative increase incoming feedwater temperature using extraction/bleed steam

The flow of steam from a higher pressure to a lower pressure is proportional to the higher absolute steam pressure as long as the lower pressure is less than 58% of the initial pressure.

W = (Pa) / 70

W = weight of steam

A = area of the orifice

P = absolute pressure

70 = constant

this is given in lb/seconds

W =51AP for lbs/hr

States that the vapor pressure in a container (vessel), the total vapor pressure is equal to the sum of the pressure of each gas.

How they found that a DA would work for removing non condensible gases

1- a body at rest remains at rest and a body in motion continuous to move at a constant velocity unless acted upon by an external force.

2- a force acting on a body gives accel. which is in the direction of the force and has a magnitude inversely proportional to the mass of the body. F = MA

3- whenever a body exerts a force on another body, the latter exerts a force of equal magnitude and opposite direction on the former.

The free expansion in a turbine nozzle and the expansion and contraction on a air compressor approaches adiabatic.

Any adiabatic process would be reversible and isentropic.

heat is not transferred to or from the working substance, work is done at the expense of the internal energy.

Enthalpy is the heat content or total heat h expressed in btu/hr

Hf = enthalpy of fluid

Hfg = enthalpy of latent heat (evaporation)

Hg = enthalpy of gas (vapor)

Hf + Hfg = Hg

The most common place for it to happen is in the Pressure Reducing Valve PRV.

A lb of steam in the low side of a PRV has the same enthalpy as the high pressure side.

steam with 3% moisture is equal to 97% quality.

Use:

Hf + (.97)Hfg = Hgw

Hgw is equal enthalpy of wet steam

16+144+180+970 = 1310 Btu

16 from ice at 0deg to ice at 32deg

144 from ice to water at 32deg

180 from water at 32 to water at 212

970 from water at 212 to steam at 212

It has two components:

1- Internal energy: the heat (energy) required to increase the rate and amplitude of vibration among the molecules of a substance. however no change in temp. We cannot calculate internal energy.

2- External work (energy): the heat required to change 1lb of water into 1lg of steam. The energy required to overcome surface tension.

144Apu

144 = latent heat of fusion

A = 0.00128 (1/778)

P = absolute pressure

U = change in specific volume

I cannot calculate internal work. But i can calculate external work.

Hfg - 144Apu = Ufg

properties of steam at definite conditions, given as temperature, absolute pressure or superheat.

3 main headings: specific volume, enthalpy and entropy.

3 conditions: liquid, latent heat and total heat

f = enthalpy of a fluid

fg = enthalpy of evaporation

g = enthalpy of a fluid

v = specific volume

h = enthalpy

 s = entropy

[(H_f(h) - H_f(l)) / H_fg] x 100

Hf(h) = enthalpy of liquid at higher pressure

Hf(l) = enthalpy of the liquid at lower pressure

Hfg = enthalpy of evaporation at lower pressure

There are two types of calorimeters:

1- Separating calorimeter: let steam from boiler into cal., steam w/ moisture is separated, water condenses going to the bottom, and you can calculate the weight of water. Steam goes to siphon and goes to a gauge. You can calc. how much steam goes by lbs/sec and calculate with the weight of the moisture.

2- Throttling calorimeter: When you let steam from a higher pressure, through an orifice to a lower pressure, it does so with constant enthalpy. Let steam out of the boiler, through orifice to ATM, read the temp. based on thermometer on well, it will have some superheated steam due to constant enthalpy. Read the Moillier chart, draw line to the left to boiler original condition.

Impeller (open/close)

Bearings

Seals (mechanical / packing)

lantern ring

wearing rings

couplings

balancing drums/discs (thrust)

Check open the suction valve

check close the discharge valve

Prime or vent the pump as needed

 Start the pump, allow it to come up to speed

Slowly open the discharge valve

When the source of the water is bellow the pump, priming is required.

When the source of the water is above the pump (positive head) we vent the pump.

-City water or service water available, you flood the casing and the suction the line to prime the pump.

-when the discharge has a vertical run there is a bypass around it, so u can open the bypass, flood the casing and start the pump.

-in some situations there is a dedicated priming pump.

33.9 feet.

Practical suction lift of a pump should be more than 15'

All the measurements for the pump are taking at the middle of the pump suction (datum)

7 steps

-check pump area clear

-open/check open suction valve

-close/check closed discharge valve

-vent/prime pump as needed 

-start pump

-allow pump to come up to speed

-slowly open discharge valve

For all feedpumps, should have a suctions valve, a discharge valve (they should be gate valves) and a check valve.

ASME code states that has to be a check valve between the pump and the boiler.

Also recommended to have a recirc line controlled with an arc valve

-on turbine side should be an exhaust valve and an isolation valve (they should be gate valve)

- need a globe valve to control the flow for roll up.

How do size an relief valve on the exhaust of a turbine driven auxiliary.

Centrifugal pump don't deliver constant efficiency.

As the discharge head decreases, flow increases.

At a certain discharge head (shut off head), the pump will sound normal but deliver no flow; u notice that when feedwater control valve is completely open but drum level still decrease.

Is the sudden formation and collapse of low pressure bubbles in water by mechanical forces. This action can damage impeller/casing (pitting)

Cavitation will happen, the idea is to not let happen for a long time.

The number is always provided by the pump manufacturer.

It is the minimum suction conditions required to prevent cavitation in a pump.

- For trash plants, shall have 2 means of supplying water to boiler.

- each feedwater source must be capable of supplying water to boiler at a pressure 3% above the highest set safety valve.

Always start a displacement pump with the discharge and suction valves open

types: duplex and gear pumps

If im going to inject something into a boiler, like quemicals, those pumps are called injectors.

If you are going to extract something, like air, they are ejectors. If its a way of pumping water is an eductor

a high pressure stream of fluid or steam is directed through a nozzle designed to produce high velocity. the resulting high velocity fluid creates a low pressure area in the mixing chamber causing the suction to flow into the chamber.

Isolate pump loto

center the piston

plumb the rocker arm

square valve over the ports

equalize the lost motion

move piston off center

Always given as:

AxBxC

a = steam piston diameter

b = fluid psiton diameter

c = length of stroke

given in the tag plate

Yes, since the steam piston is two to two and half times larger than the water piston.

Looking at the the area it would work. 

Pump slip is the difference between the design output of the pump and the actual output of the pump.

pump with 15% slip is 85% efficient

LANE / 231

L = length of stroke

A = area of piston

N = Number of stroke

E = efficiency (slip)

only useful for duplex pump

It will depend on the info given.

Theoretical HP = (Q x 8.33 x H x sp.gr) / 33,000

Q = capacity gpm

8.33 = to convert to lbs

H = Head, ft

sp.gr = specific gravity of fluid (1 for water)

Required HP

(Q x 8.33 x H x sp.gr) / (33,000 x Ep)

Ep = Efficiency of pump, slip 15% = .85

Kw input

(Q x 8.33 x H x sp.gr) / (33,000 x Ep x Em x 1.341)

Em = efficiency of motor

1.341HP = 1Kw

- The quantity (capacity) varies directly with the speed

-The discharge head varies as the square of the speed

- The power required varies as the cube of the speed

They control the exact amount of water returning to the boiler. basically, the same amount of water going out should be going in,

Three types of regulators:

- Single element: senses only the drum level

-double element senses drum level and steam flow

- tripe element senses drum level, steam flow and feedwater flow.

At Bpower since we are a once throw boiler, we sense the temperature of the HP ST entering steam, and adjust the feedpump to maintain the required temp of the superheated steam in the ST since we dont have a drum.

External treatments: done to water before it gets to the boiler.

Internal treatment: Added directly to the boiler via DA for example, or to the condensate like at Bp

To prevent sludge from depositing on boiler surface; to prevent scale from forming on boiler surface; to prevent corrosion of boiler metals and to prevent  carryover with the steam leaving the boiler.

Most common problems in our region are silica, calcium, magnisium and oxygen

Cations are positively charged and regen with acid.

calcium and magnesium

Anions are negatively charged and regen with caustic.

chlorine and carbonate

They are classified as dissolved solids (mineral salts; calcium, magnesium)

suspended solids (organic materials like mud and clay)

dissolved gasses (o2 removed on DA or in the condenser like at BP)

Is a measurement of the water acidity and alkalinity.

scaled 0 to 14 as 7 being neutral.

each number on the scale increases by a factor of 10.

boilers usually operate around 10.

How much more alkaline is water w/ ph of 9 than water with ph 7?

Clarifiers

filtration (sand filter)

dearation 

Removes the hard scale forming salts of calcium and magnesium ions and exchange them for sodium (ions) which are soluble in water.

Zeolite is the resin used in water softeners.

Four steps:

Service

Backwash

Regenerate

Rinse

Compounds of calcium and magnesium are the hard scale forming dissolved solids in make up water.

Hardness can be permanent or temporary.

Temporary hardness is caused by bicarbonates of calcium and magnesium.

Heating causes the bicarbonates to drop out of solution as a soft sludge.

Sulphates of calcium and magnesium cause permanent hardness (cannot be removed by heating up the water) need water softener or higher.

You get low conductivity, neutral PH and very very low silica.

Silica is a big problem since it can get carried away on the steam, and harden in the ST damaging it.

- Volatile chemicals are chemicals used in high pressure units where residual solids cannot be tolerated. Commonly hydrazine is used to scavenge oxygen, ammonia is used to control ph and amines are used for condensate corrosion.

- Non-volatile program (phosphates, caustic soda) are classified as dispersants or precipitation (sludge); used to remove waterside deposits or maintain water side surface.

At Berkshire Power, we use ammonia solution injection in the condensate leaving the hotwell. the make up water is treated on a demin train and its oxygen is scavenged in the condenser.

Loss of phosphate residual on load upswing. Residual recovery on downswing due to resolubilizing. 

Temporary upset in ability to neutralize caustic.

Requires stressed conditions (cracked plates, porous conditions)

free caustic in system (sodium hydroxide)

Sodium hydroxide becomes concentrated and leads to crystalline cracking of plates

AKA: stress corrosion cracking / caustic cracking

- Priming is the carry over of large slugs of water with the steam due to high water levels in the boiler and/or foaming.

It can be corrected by reducing the firing rate and restoring NOWL

- Carry-over is the carry-over of fine droplets of water and/or suspended/dissolved solids with the steam due to high water level and/or foaming.

It can be corrected by reducing the firing rate and restoring NOWL

-Foaming is a layer of foam on the surface of the water due to high alkalinity, high dissolved/suspended solids or the presence of oil or other colloidal solids.

Makes is difficult for steam to form due to surface tension on the water. Finding the true level can be difficult in this situation.

Correct the condition by reducing firing rate, increasing boiler blow down and bringing it back to NOWL. Make is sure the make up water is not the cause of the problem.

The preferred method is the wet method:

1- clean the fire side and the steam side

2- close up steam and water side (use new gaskets)

3- fill the boiler with warm, treated water until filled to the boiler vent

4- close the boiler vent

5- maintain a pressure in the boiler slightly above atm

If the boiler is going to be down for over 3 months use the dry method:

1- Clean the fire side and the water side

2- dry out boiler completely

3- close all valves on the boiler to prevent moisture from entering drums

4- lay trays of moisture absorbing chemicals in the boiler

5- close steam and water side

6- check moisture absorbing chemicals periodically, replace when needed.

Boiler layup is required for boilers that are not going to be in service, improper layup can result in damage by oxygen pitting. there are two method, Wet layup and dry layup. either way the water has to be completely cleaned on water side and fire side. all repairs have to be made.

the layup method is determined by the length of time that the boiler will be layup and if the boiler will be needed in short notice.

the dry method is for long period like 3mo and is not available in short notice.

Is the ration of boiler makeup water compared to steam evaporated plus boiler blowdown.

as a starting point it assumes that all steam leaving the boiler returns as condensate. so makeup = blowdown

reality is makeup = blowdown + losses

COC is the concentration of dissolved solids in the boiler water divided by the dissolved solids in the makeup water.

this indicates the number of times the water in the boiler has cycled up.

- Based on the OD of steam supply line:

Up to 1 3/4 = 9Hp

1 3/4 to 3 1/2 = 50Hp

3 1/2 to 5" = 150Hp

5" up = unlimited

- Steam flow formula

Hp = Ws(h1-h2)/4545

- manufacture data plate

- Non-condensing (backpressure): exhausts at a pressure higher than ATM

- Condensing turbine: exhausts to a vacuum

- Bleeder turbine: Has an extraction to a steam feedwater heater. Uncontrolled extractions

- Extraction turbine: Extraction provides steam to a process. Controlled extraction.

Diameter of blade is 48" turning at 400rpm. What is the relation of steam velocity to blade velocity on the assumption that steam had a velocity of 11,600fpm?

What type of turbine is it?

48" = 4 feet

4x3.14(Π) = 12.56 feet traveled per revolution

12.56 x 400 = 5,024fpm

11,600 / 5024 = 2.308

Steam velocity is 2.308 times blade velocity.

Based on the ide that a reaction turbine, steam velocity is equal to blade velocity, this turbine is an impulse turbine where steam velocity is 2x or more blade velocity.

Pressure, velocity and volume. In the Impulse turbine, there is a pressure drop in the nozzle, volume always mirrors the pressure, so whatever the pressure does the volume will do the opposite.

In the reaction principle, the steam 

In the Curtis stage there is one pressure drop on the stationary nozzle, as a result there is only one volume increase.

Velocity increase on nozzle, decrease on moving blades, stationary on redirecting blades and decrease on moving blades.

A curtis stage has a large pressure drop and a large temperature drop, what allows to reduce the size of the turbine.

The disadvantages are poor efficiency.

1- It extracts flammable or explosive vapors

2- It provides a slightly negative pressure in the reservoir to facilitate the return of the oil from the turbine

3- It removes moisture

1 - the supply temp to the bearings around 110deg

2- the return temp from the bearings around 135deg

Axial and radial clearance. Axial clearance maintained by thrust bearing and radial clearance maintained by Journal bearings.

Radial clearance is the distance between blades and casing

The axial clearance is held closer in the impulse section to reduce free expansion of the steam, when the steam leaves the nozzle it expands.

The thrust bearing maintains that axial clearance.

The reaction section has a pressure drop across every stage and it has more tendency for the steam to go over the blades. In reality what maintains that clearance is the lube oil, thats why temp control is so important.

The radial clearance is more important in the reaction side of the turbine.

Axial impulse / radial reaction

For thrust bearing that maintain axial clearance there is the Kingbury  and Tapered Land bearings.

Two types of seals are the Carbon seal and the water seals.

Normal vibration on ST is around 1-4mils, usually 5 mils is an alarm point and 10mils trip, or you should remove the turbine of service.

Common vibration causes are:

Oil whip, bowed rotor, misalignment, high eccentricity, biding, work bearings and imbalance.

The gland seal exhaust insures that the steam used in the gland seal doesn't seat on the turbine seal and condenses, the exhaust makes it sure that there is a constant flow of steam through the seal.

In some cases there is a gland seal steam condenser to turn that used steam into condensate and back into the hotwell.

There are two balls connected to a gear connected to the turbine and a linkage connected to the steam valve. as the turbine speed up, the balls spin crating a centrifugal force allowing the linkage to move and moving the steam valve.

the major problem here is that it hunts around speeds, ok for a fan for example but not for power generation.

Later they adapted a servo motor to dampen the hunting connecting also a speed changer, calling it the Mechanical Hydraulic Changer MHC