analisa kegagalan pd boiler

8/10/2019 Analisa Kegagalan Pd Boiler

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BOILER


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Kegagalan yang sering terjadi padaindustri pembangkit tenaga yang sudah

berumur

1.Kegagalan akibat fatigue

2.Kegagalan akibat korosi

3.Kegagalan akibat creep4.Kegagalan akibat overheating

5.Kegagalan akibat erosi


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Boiler Safety


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KEMANAN pada BOILER

Pressure gauge & Test connection

Safety Valves (Drum & Super-heater)

Blow down valve

Drum Level Water Gauge Glasses

Stop Valve in Steam line

Stop & Check Valves in Feed Line


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Safety valve

Fungsi untuk mengantisipasi tekanan dari boiler dengan

mengeluarkan steam yang berlebih ledakanbisa dihindari

1 boiler harus memiliki 1 SV, tetapi untuk boiler yang memiliki

permukaan panas lebih dari 500 sq.ft dan power input lebih dari500 KW sebaiknya memiliki 2 atau lebih SV


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Capacity of Safety valve

In any case , SV capacity must be such as to discharge all thesteam the boiler can generate without allowing pressure to

rise more than 6 % above the highest pressure at which any

valve is set & in no case more than 6 % above the maximum

allowable working pressure.

All the Safety valves used on Steam boilers must be of Direct

Spring Loaded type.


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ASME markings required on

High Pressure Safety Valves:

Name or identifying trade mark of manufacturerManufacturers design or type number

Size in inches, Seat Diameter in inches( i.e the pipe size of

valve inlet )

Pressure in lbs/ sq.ftor Kg / sq.cm (Steam pressure at

which it is to blow)

Blow down in Kgs or lbs ( BD is the difference between the

opening & closing pressure )Capacity in lbs / hror kg / hr

Capacity lift in inches. It is the distance the valve disc rises

under the action of steam when the valve is blowing under a

pressure of 3 % above the set pressure.


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Number of Safety Valves requirement

Each Boiler requires at least one SV, but if the heating surface exceeds 500 Sq.ft, the

boiler must have two or more Safety relief valves.

When not more than two valves of different sizes are mounted singly on the boiler,the smaller valve must not be les than 50 % in relieving capacity of the larger valve.

Every super-heater attached to a boiler with no intervening valves between thesuper-heater & boiler requires one or more safety valves on the super-heater outletheader.With no intervening stop valves between the super-heater & boiler, thecapacity of the safety valves on the super-heater may be included in the totalrequired for the boiler, provided the safety valve capacity in the boiler is at least 75 %of the aggregate SV capacity required for the Boiler.

Ex- If a boilers steaming capacity is 100 tons, a minimum of two valves are required

on Boiler with a total relieving capacity of 75 % of (100 Tons) I.e 75 tons. The

super-heater would then require a SV with a capacity of (10075) tons

i.e 25 Tons.


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Important PointsHeating Surface :

That side of the boiler surface exposed to the products of combustion,exclusive of super-heating surface.The areas to be considered for this

purpose are tubes, fire-boxes, shells, tube sheets & the projected area

of the headers.

Sequence of Safety valves Blowing:

The super-heater safety valves should always be set at a lower

pressure than the drum safety valve ,so as to ensure steam flow

through the super-heater at all times. If the drum safety valve blowsfirst, the super-heater could be starved of cooling steam, leading to

possible super-heater tube overheating & rupture.


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Important Points

Re-heater Safety valves :

The capacity of re-heater safety valves can not be included in the total

safety valve capacity required for the boiler & super-heater.The

relieving capacity of re-heater safety valve must not be less than 15 %

of the required total on the header. The total capacity on the re-heatermust be at least equal to the maximum steam flow for which the re-

heater is designed . One SV must be on the re-heater outlet.

Installation of Safety valves:

Every safety valve shall be connected so as to stand in an up-right

position with spindle vertical.

analisa kegagalan pd boiler

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