Home > Instrumentation and Control System, Power Plant Technology > Steam Drum Level, 3 Element Control

Steam Drum Level, 3 Element Control

Setelah puas bicara masalah Photography dan Travelling, kita beralih ke pembahasan Power Plant Technology. Kali ini bahasanya saya sajikan in English aja yah, biar bisa di baca sama orang-orang bule.🙂

In my previous post “Where does the Steam come from?” we’ve understood that water is pumped from feedwater tank via boiler economizer to steam drum. Water is introduced to steam drum through perforated pipe from the bottom of steam drum along the length of the drum, and maintained to fill up a half volume of the drum.

The purpose of steam drum in boiler is to separate water and steam in water/steam natural circulation, where the saturated steam that separated from water/steam mixture will passes from steam drum then will be superheated in the superheater and finally convert to superheated steam as a final product of boiler. On the otherside the water will be circulated through heat transfer media via furnace wall tubes then flowing back to the steam drum as water/steam mixture that will continuously separated from saturated steam.

In steam drum, there is a phenomenon called “shrink and swell effect”. In case of boiler load increasing (steam flow), it will increase steam bubble volume, then steam drum will decreased and fuel firing (heat input) will increase. At this moment, drum level will indicate high, this is what we called swell effect. When drum level is indicated high, feed water will reduce the flow in response of drum level high. This is an appropriate control response, it should increase feed water flow during high load!! The result, boiler will be trip because of drum level alarm low.

In other case, due to a decrease in load (steam flow), it will decrease (shrinkage) in drum level due to a decrease in steam-bubble volume. Resulting increase in drum pressure and a decrease in heat input. Feed water flow response to this shrink effect with increasing feed water flow, then there will water carry over that can damage boiler tubes and turbine.

This process phenomenon can be overcome with more sophisticated control strategy, that called steam drum three element control. The three element control refer to three process variable in steam drum control:
1. Feed water flow
2. Drum level
3. Main Steam flow

The purpose of 3 element control strategy is not only maintaining mass balance of water input and steam output in steam drum but also to achieve boiler safety operation in “shrink and swell effect”. Configuration of this control strategy employs cascade control of drum level control (master) and feedwater flow control (slave), then configuring feedforward control, where total steam flow (main steam flow, sootblowing steam, etc) will be corrected by drum level control output as remote setpoint for slave. This configuration will result mass balance between feedwater and total steam flow, and also become a smooth control in shrink and swell condition.

In the next post, we will discuss about how to calculate differential pressure of steam drum as level indication.

Let’s share the ideas!

Tofan Azhar Hakim

  1. December 26, 2009 at 6:51 pm

    kejam lu pan
    pake bahasa indonesialah
    katanya orang indon

  2. bapake dina
    December 26, 2009 at 9:31 pm

    ono versi boso jawa-ne gak iki ?😀

    • December 27, 2009 at 5:40 am

      @ bapake dina: tolong ditranslate ke boso jowo nggih.🙂

  3. Fistek 2005
    December 29, 2009 at 2:52 pm

    oia modellingnya gmna mas..?? klo waktu kape saya juga berkutat yg 3 element itu.. dimana didasarkan pada 3 element. pressure,Flow, dan Level.. dmna levelnya sbgai master controlnya….

    • December 29, 2009 at 10:36 pm

      Kalo untuk simple modelling, yang pertama kali dilakukan adalah mengidentifikasi sistem, menentukan variable input dan output. Menurut saya untuk modelling yang realistis untuk steam drum, kita harus memperhatikan bahwa water dan steam density bervariasi tergantung dari pressure, yang mana pressure sendiri tergantung dari heat input dan juga feedwater tempearure, demikian juga dengan feedwater flow dan main steam flow. Terus terang saya juga belum pernah bikin modellingnya. Kalo mas pernah bikin pas KP, mungkin bisa dishare ke saya? karena menarik juga variable prosessnya pakai pressure, cz saya belum pernah ketemu yang pake pressure.

  4. bapake dina
    December 29, 2009 at 10:32 pm

    om topan ikut modelling juga kah? no agensinya brp? boleh dicontact bwt hunting neh,wkwkwkwkk…

    **o’on mode : on

  5. December 29, 2009 at 10:40 pm

    Walah, bapake dina sekarang dah cari2 model tho, mau model co ato ce? saya bisa sediakan. hehe
    **o’on mode juga ah..

  6. bapake dina
    January 7, 2010 at 1:14 am

    haha..

    btw,3element pake variable pressure to?

  7. muhammad sidiq ramadan
    March 24, 2010 at 6:43 pm

    mas, saya sedang mengerjakan tugas akhir yang menyangkut drum level control dan steam drum dalam bentuk simulasi…..kalau ada materi yang bersangkutan bisa saya minta??karena saya ingin cepat menyelesaikan tugas akhir saya secepatnya…..terima kasih…

    • ajunkz
      December 18, 2010 at 11:25 pm

      gmana mas sdh dapatpeodelan matematisnya blum

  8. Arshavin
    May 19, 2010 at 3:08 pm

    Apik tenan, singh tak waco tak copy yo mas…

  9. gandhi
    August 23, 2010 at 12:51 pm

    pemodelan sistem dinamiknya seperti apa ya? kalau dipasang secara horizontal, fungsi level terhadap volumenya seperti apa?
    terimakasih

  10. March 16, 2011 at 3:00 pm

    Mantap mas penjelasan tentang shrink dan swell effect di steam drum..

    Salam,

    M. Taufik

  11. salam
    July 2, 2011 at 2:57 pm

    mas topan,
    saya mau tanya nih
    kalo menghitung volume steam drum pada boiler (water tube) gimana cara nya???
    misalkan di ingin mencapai tekanan 2 bar, trus volume air dan temperatur nya yang optimal berapa y???
    terimakasih atas artikel nya
    jika anda tdak kbratan tLg di kirim jawabannya ke email saya
    mgs.abdussalam@yahoo.com
    jawaban saudara akan sangat membantu
    terimakasih

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