BOILER MOUNTINGS

1 GUAGE GLASSES :

1.1 Level guage glass :

Guage glass is an important mounting for the boiler. Drum wate plays a very important part in
controlling the boiler operations. Direct guage glass is mounted on the boiler drum which shows the
water level in the drum on site. But every time it is not possible to watch the level from local. So
some arrangement is to be incorporated to transmit this level in remote control room. For this the
connections of guage glass pipes are used or seperate provision is always made for tapping this type
of guage glass provision. The details of this type of guage glass is expnained below.

1.2 arway's remote level indicator :

This indicator combines two major components (1) a sensing element which responds to differential
pressure and (ii) an indicating system which presents a visualresponse as a true reading level. This
sensing elecent, or constant head chamber, measures and compares the variable head of the liquid
in the vessel to a constant head maintained within the sensing element. The indicating system is
located outside the pressure zone and receives its rotating force through a permanent magnet
coupling, thereby eliminating direct mechanical linkages and stuffing boxes. The permanent magnet
is positioned by a spring loaded stack diaphram which moves in response to differential pressure
changes.

In most installations the water level guage glass reading is the accepted standard or reference. To
assure indicating accurancy, the indication system is provided with suitable compensation to match
the pressure demands of the particular system. Three types of compensations are available, natural,
temperature, and pressure compensation.

1.2.1 Natural Compensation :

In a natural compensation system, the constant head chamber assures natural compensation by
reducing the density of the water in the indicator. In operation, steam from the boiler fills stream leg
piping and the constant head chamber, condensing and heating the water in this chamber and in the
upper portion of the constant head pipe running to the indicator. The side overflow, the variable leg,
is connected to this lower fitting on the pressure vessel. In addition to this natural compensation the
indicator is calibrated to the average guage glass water density.

1.2.2 Temperature Compensation :

On pressure above 52 Kg/cm2 density changes due to increasing temperature become sufficiently
pronounced to require the addition of a temperature-compensating jacket fastened around the
variable and constant head pipes of the constant head chamber. This permits reheating of the
constant head pipe by the stream within the variable head pipe, adjusting the density of the water
so that mid scale accuracy is guaranteed for all pressures. In addition, this compensation provides
full-scale accuracy at the specified operating pressure.

1.2.3 Pressure Compensation :

deactivation of high pressure boiler, pressure compensation used in conjection with When total, full
scale accuracy is necessary for all pressures, as during activation of pointer movement to
compensate for density of water at different pressure in the indicator. temperature compensation
can be added to the indicator, there by providing additional

The pressure compensated indicaor can be furnished to guage density or drum density as

specified.

1.3 Direct guage glass :

This guage glass is mounted on left and right side of the boiler drum, which

indicates the drum water level directly. There are 7 ports of the guage glass and ports are

having vision glasses to see the level. So by vision, the exact level in the drum can be

soen

2. SAFETY VALVES :

Following safety valves are provided for each boiler. Safety valves at differet locations are provided
as per boiler act and to safeguard the system at the time of excessive steam pressures of those
particular locations. All the safety valves are spring loaded type, One Safety valve is of
electromagnetic type, which operates on solenoid assistance, Safety valves on the duperheater main
steam line provided protection by assuring adequate flow through the steam lines if the steam
demand is suddenly and unexpectedly drops. Reheater safety valves, located on the hot and cold
reheat piping serve to protect the reheater steam flow if steam flow through the reheater is
suddenly interrupted.

3. STOP VALVES ;

Steam from final superheater, is taken to Turbine by two pipes one from left and one right side of
the Boiler. On these lines the valves are provided so that the steam line can be isolated when steam
flow to turbine is not required but the boiler is to be kept running for any important works on
turbine. These stop valves are of gate type and are manually electrically operated. Also for hydraulic
testing of the boiler these valves provide isolation of steam lines going to turbine.

4 STARTUP DEVICES :

a) This is provided on each boiler and is operated when the boiler is being lighted up and to gain or
achieve the required values of pressure and temperature and to stabilise the chemical values of
boiler water before charging the steam lines or HP/LP bypass even.

b) Safety valve of the boiler is supposed to close after certain pressure drop. If it is not closing at a
particular pressure, by opening startup vent valve, the pressure, can be dropped to lower the value
and safety valve closing is achieved. If the safety valve is allowed to continuously blow the seat of
the safety valve may get damaged and may create a problem in running the boiler. Startup vent is
operated from the control room. It is a puffing type valve

5. SAMPLING:

Before starting the boiler and while running also, the chemical values of drum water superheated
steam etc. are always maintained within the operating limits. So all these chemical values are to
checked periodically. To check these values the actual sample of the steam and wale is essential. As
the boiler is running with high pressure and temperature, the sample collection is difficult for this
certain specified sampling points arranged at the piping or equipments and are arranged and the
sample is thus taken through sampling points to the sampling coolers specially provided for the
purpose. Following samples are taken periodically

a. Feed water sample. This sampling point is taken after the H.P. heaters outlet

b. Saturated steam sample. This sampling point is taken from the pipes coming out from drum to
superheater No.1 There are five pipes coming out from drum to superheater No. 1, from all these
pipes a sampling line is taken out and of these five sampling lines one common line is taken to
sampling cooler.

c. Superheated steam (Final Steam) this sampling point is taken from outlet steam pipe of
superheater going to tubine before stop valve, generally from left hand side steam pipeline.

d. Drum water. This sampling point is taken from C.B.D. line before C.B.D. valves.

6.CHEMICAL DOSING :

A chemical dosing system consisting of

a. Phosphate dosing to boiler drum

b. Hydrazine dosing to booster feed pump suction

c. Morpholine / Ammonia dosing to condensate suction.

Each dosing scheme is provided with solution preparation facility, solution

measurement, dosing pumps and inter connecting piping to provide condensate to the

solution preparation tanks, suction piping and the discharge piping upto the point of the

application Phosphate dosing has been provided to maintain a maximum phosphate level of 10

PPm in the boiler drum to keep the scale in loose conditions and also to maintain the PH.

Hydrazine dosing has been provided to scavange the residual dissolved oxygen coming from the
deaerator outlet. Hydrazime dosing scheme has been designed to inject upto a maximum of
0.02PPm of Hydrazine.

Morpholine / Ammonia dosing has been provided to neutralise the corbondioxide in

the condensate. The system is suitable to handle both morphonine and ammonia any one of

the chemicals is used as per requirements.

7. CONTINUOUS BELOW DOWN :

As boiler is running with full load or partial load, the steam consumption varies as

per load and at all loads the chemical values are to be maintained. These values are

checked by chemist by taking samples from the sampling points. The chemical values of the

boiler drum are very important as if the values of the drum water disturb it carries the

impurities to steam an turbine blades may get damaged due to scale formation, on blades.

If the values are found abnormal during sampling, there must be some arrangement
to drain out the impure water so that fresh treated water can be fed to the boiler. For this,

the continuous blow down connection to the boiler drum is given which is at the bottom of

boiler drum so that any solids deposited in the drum can be drained while the boiler is

steaming. By adjusting the opening of this blowdown valve the draining and feeding rate of boiler is
maintained by maintaining the drum level to a normal level. During this process the

chemical dosing to the boiler drum can be increased by adjusting dosing (i.e. adding

concentrated dosing to boiler water) and the values of the boiler water can be increased to

the required values. This is a very important operation for running the boiler with safe

chemical limits. The C.B.D. is taken to C.B.D. tank and the tank and the tank is having to drain to
atomsphere.