New technical problems at Medupi place South Africa at risk

January 7th, 2015, Published in Articles: EE Publishers, Articles: Energize

 

New technical problems arising during the commissioning of Unit 6, the first of six 800 MW generation units at Eskom’s Medupi power station, may be placing South Africa’s electricity supply at risk.

Medupi pic 1

These problems have made it impossible for Eskom to conduct blow-through testing of the first Hitachi boiler at Medupi at the steam speed, volume and turbulence factor required in the international VGB guidelines and contract specifications, in order to achieve the necessary levels of inlet steam cleanliness to the steam valve and turbine .

Steam blow-through is conducted after chemical cleaning to blow steam through the boiler and associated pipework to the atmosphere, in order to clean the plant of construction debris, particles, scale and other contaminants, and establish and prove the required steam inlet conditions before connecting the final piping to the steam valve and turbine.

Blow-through testing is intended to simulate full-load conditions in respect of steam speed, volume throughput and turbulence, for relatively short periods and at reduced steam power and temperature. The tests are conducted repeatedly over several weeks until the contractually specified levels of steam inlet cleanliness have been established at the specified conditions of steam speed, volume throughput and turbulence.

As a result of an inadequate design of the temporary piping that blows steam to the atmosphere, try as it might, Eskom has been unable to achieve blow-through at the specified steam conditions to achieve the required levels of steam cleanliness.

As a result, and despite earlier assurances that commissioning of Unit 6 at Medupi would proceed by the book, the Eskom technical team has now decided to abandon further blow-through testing and proceed with the connection of the final steam piping, and other commissioning such as testing of the boiler, turbine and generator protection systems.

In October 2014, Public Enterprises Minister Lynne Brown, Eskom CEO Tshediso Matona and Medupi Project Manager Roman Crookes committed Eskom to first synchronisation of Unit 6 at Medupi on 24 December 2014.

This was a year later than that previously committed to by former DPE Minister Malusi Gigaba and Eskom CEO Brian Dames, with the commercial operation date for the first unit some four years later than that initially committed to by the Eskom board when the project started.

However in November 2014 it became clear that the deadline of 24 December 2014 would not be met, and Eskom’s much publicised 100-day countdown to first synchronisation on Christmas Eve was abandoned. A revised date for first synchronisation was given as mid-January 2015.

The justification by the Eskom technical team for the further delay was that, after seven years of blood, sweat and tears, a self-imposed and largely symbolic project milestone date would not be allowed to place the boiler, turbine and generator, and indeed the whole project, at risk.

The Eskom technical team assured the media and the public that commissioning of Unit 6 would not be influenced by political, management and time pressures, but would proceed meticulously, strictly in accordance with international standards and contractual requirements, even if this meant a few weeks’ delay in first synchronisation.

This new decision by Eskom to deviate from international best practice raises the question as to why the utility does not simply replace the problematic temporary blow-through steam piping with correctly designed piping, in order to complete blow-through by the book. The answer given by Medupi Project Manager Roman Crookes is that this would cost millions, and would take six months to replace, thus delaying first synchronisation of Unit 6 still further.

Other questions arise in respect of Alstom’s guarantee, as the steam valve and turbine OEM and turbine works contractor at Medupi. It has been suggested that the steam valve and turbine could suffer serious damage if significant debris, that is said to be visible in the boiler, blows through to the turbine during full-load operation. Eskom denies that there is any significant risk, pointing to a strainer in the steam pipe that filters debris larger than 1,5 mm for the first six months of operation, and thereafter a strainer that filters debris larger than 5 mm.

Eskom also emphatically denies any possible safety risk resulting from its decision to abandon further blow-through testing, including possible damage to the steam valve, which is critical in shutting off steam to the turbine in cases of sudden load loss, to avoid over-speed conditions that could result in catastrophic destruction of the turbine and generator.

When questioned on the implications of its decision on the turbine and steam valve guarantee, Eskom indicated that while Alstom had not been part of the technical team that made the decision, Alstom accepted Eskom’s thinking at a technical level. However, Eskom then conceded that it had not yet engaged with Alstom to reach agreement on the commercial and contractual issues arising, including that of the steam valve and turbine guarantee.

Eskom also stresses that its decision to abandon further blow-through testing was purely a technical decision and deviation to address technical problems arising during commissioning, and was “taken with its eyes wide open after a thorough risk evaluation”, which indicated that not only was the risk very low, but also that any remaining risk could be adequately handled by Eskom.

The question however is whether, after so many broken commitments, the word of the utility is trusted.

  • Clynton de Fin

    Did,nt someone (was it Andrew Etzinger?) from Eskom promise to eat his hat if we did not have electricity from Medupi power station by xmas 2014?? Please can Andrew come forward publically and do the honours.

    • Doesn’t sound like Andrew. I know he is ever optimistic publicly, but don’t know if that world extend as far as eating his hat 🙂

      • Clynton de Fin

        Guess we will have to wait a bit longer to see the light ant the end of the tunnel.

      • Juvenis_J

        Well said, Chris!

  • D60377

    I’m no expert on steam turbines, but potential 1.499mm particle(s) travelling at speed in superheated steam doesn’t sound all that harmless. That’s apart from the flow restriction (read : reduced output) that such a filter must present, even if it’s perfectly clean. The minimum criteria for “effective” blow-through obviously exist for a reason!

    One wonders how the “millions” that proper temporary pipework will cost, stack up against the cumulative cost of reduced output over months (or years) ? To say nothing of the knock-on costs if something goes wrong. One can understand the urgency – or is it desperation? – but this seems to be a classic case of penny-wise, pound foolish.

    Also from a purely project-management perspective, this sounds like folly on Eskom’s part. Having not been involved in this huge decision, any good project manager at Alstom would (and should) jump at the chance to wash their hands of the potentially massive liability that the valve and turbine guarantee now represents.
    Guess who will now ultimately foot the bill if the dirt hits the turbine ?

    • My understanding from sources within Alstom is that the contractual guarantee will be voided, but that Alstom will make its full resources available to support Eskom, and maintain, service and repair the machines at Eskom’s cost.

      • D60377

        Oh my … what a lovely (and potentially lucrative) position for Alstom to be in 😉

  • PAT

    This is risky! The turbine blades are very sensitive and I can see in my head that Alstom is busy with their lawyers reviewing the entire contract to make sure they are covered or can honour their guarantee!!

    • My understanding from sources within Alstom is that the contractual guarantee will be voided, but that Alstom will make its full resources available to support Eskom, and maintain, service and repair the machines at Eskom’s cost.

      • PAT

        Just shows how desperate the situation is that they are prepared to take THIS chance!

    • A big risk is that Alstom will void their guarantee on the steam valve and turbine, and Eskom has not even addressed this yet! Good grief.

  • I was a control and instrumentation engineer for the main contractor during the construction of two major power stations, namely Matla and Lethabo. I was also fortunate enough to witness the steam blow-through procedures on numerous occasions during the initial commissioning of these boilers, and it is mind-boggling to see what size objects are actually blown into the atmosphere. These were usually left in the piping during the construction phase, either by accident, or maliciously by disgruntled laborers. I am sure nothing has changed since then, and Eskom (due to lack of experience of their current employees), is taking a huge risk here. And yes, guess who will pay for the damage when a shifting spanner or a welding rod hits the turbine blades? It is absolute madness. The biggest mistake I can see here is the combination of two contractors who are not communicating with each other properly, and hiding behind the ignorance and inexperience of Eskom engineers.

    • Interesting comments, thanks!

    • PAT

      And these boilers were built by real experts. Babcock.

      • Absolutely! And they sent me to Germany to sit with Siemens for six months to ensure the interfacing between boiler control, furnace control, turbine control and coal feeders operate and interact properly, before it is even attempted on site….

    • From what Eskom told me, this is not a boiler design problem but a problem with the design of the temporary pipework from the boiler to blow off steam to the atmosphere. Not sure it it is Eskom or Hitachi who has design responsibility for this, but I suspect it is Eskom.

      • I think I still have the drawings from 4 x different power stations we built successfully in the past – they can borrow it…..?
        It is a question of routing it to bypass the turbine I think?
        With a few PID -controlled valves…..hiehie .. 😉
        I’m sorry, but you have to see the humor in this situation, not?

  • I fear this suggests they couldn’t develop sufficient steam. Is it possible Hitachi, with their lack of familiarity with SA coal, has messed up the boiler design? Are we to pay for Chancellor House involvement in what should have been Eskom’s business?

    • From what Eskom told me, this is not a boiler design problem but a problem with the design of the temporary pipework from the boiler to blow off steam to the atmosphere. Not sure it it is Eskom or Hitachi who has design responsibility for this, but I suspect it is Eskom.

      • Eskom has now confirmed that the temporary pipework was Hitachi’s design. Now the problem comes as to whether the problem has been correctly identified. Was there too much pressure drop over the pipework to achieve the required 200m/s, or was there too little steam to reach more than 180m/s actually achieved? My original comment suggested that the problem might have been too little steam.

  • Robert Melaia

    The first reaction I had was along the lines of Hennie Visser’s post: Surely numerous “Blow-through” tests have been conducted over the years, and with cleanliness measurements / levels so important – the experienced technical people in this project must have done this many times before – KNOWING EXACTLY WHAT STEAM CLEANLINESS IS EXPECTED INTIALLY?
    If the cleanliness is bad – and the steam usually very dirty / contaminated during the first stage of the “blow-through” tests – they will be aware of this and bypassing the test will have been decided with this in mind.
    Even if not the case – without doubt there have to be numerous historic test results proving exactly how clean or dirty the initial steam is on other units in other power stations? Mepudi can’t just incidentally be so different to all previous stations?
    I would credit the TECHNICAL people at Eskom in this respect with my assumption that the above factors have been considered as carefully as they have indicated.

    My serious concern is that this decision is purely a forced result of extreme pressure from more senior (questionable) management – insisting that the “blow-through” test is bypassed – so that these members do not have to suffer any further pressure for lack of progress.
    We all know very well what happens when external financial and even political pressure force technical decisions. I just hope this isn’t the case here…

    • PAT

      Most of those involved initially with blow through tests in the past in Eskom are either retired or passed on I think.

    • Thanks for the comments.

  • Juvenis_J

    We all need to start insisting that the truth should be told. This is not a “technical” problem. It is a problem of pure incompetence and for this we have to thank those who say that Eskom problems are inherited from apartheid. The main culprit is “RSE”. Who’s that, I hear you say. Well tack the letters on the end of SA’s worst four letter word and you’ll see. If I lived in France, I guess I’d be in trouble!

  • Miss Roxy

    Not sure if its a typo but is the second strainer at 5mm or 0.5 mm?

    I have a feeling that a panic situation is starting to appear on the horizon. With the overall delay some 4 years and counting on just one unit is this now a do or die scenario. In my time I have come across damaged turbines just because of a temp drop causing a slight condensation. Reading comments below I can somehow see Koeberg’s nasty bolt issue paling into nothingness should the below comments come to fruition.

    • D60377

      I think it’s ‘subsequent’ in terms of operating time rather than flow direction; but you raise a valid question !
      One assumes the logic is that after some 6 months of operation, the 1.5mm strainer will have caught all the small detritus – as well as any big-ticket items, of course. Thereafter I gather a strainer with a larger aperture (5mm) will be fitted to permit better flow, whilst still guarding against errant bolts or other large objects that might ‘somehow’ find their way into the steam circuit.
      Given that the initial strainer is going to pick up all the small stuff left behind by the less-than-thorough blow-through regime, presumably it’s going to need fairly regular cleaning (and possibly panelbeating).
      Hmmm … I wonder if “planned maintenance” includes “calculated gambles” in the pie charts ?

    • VanillaDisgustard

      Jisou maar Tannie is slim!

    • After the initial 6 monts period the strainer size is increased to 5 mm.

  • John Whybrow

    When the specifications for the boilers and turbines were being drawn up in the early 80s for the Matimba and Kendal (and eventually Majuba) power stations, extensive discussions took place with the suppliers of boiler and turbine plant prior to the issue of the enquiry, to find out how they determine when the HP pipework can be deemed to be ‘clean’ after repeated blow-throughs. The outcome of these discussions resulted in a clause in both specifications which stated that the HP pipework up to the turbine stopvalve can be deemed to be ‘clean’ if the soft aluminium target plate placed obliquely in the discharge of the temporary pipework has no impact mark on its surface greater than 0.5mm in diameter. Any impact mark greater than 0.5mm would require another blow-through.
    I have no means of knowing if those same clauses were included in the Medupi and Kusile contracts. If they were, then surely the risk factor is small despite the VGB Guidelines, as the degree of cleanliness has been determined by older proven methods. If however those same clauses were not included in the two contracts and there has been no target plates available for inspection and acceptance, then the risk is considerably higher, and Eskom could be culpable which would add to its already considerable unbudgetted costs.

  • VanillaDisgustard

    En ons maak stoom, stoom stoom deur die pype,
    stoom, stoom deur die kleppe,
    stoom, stoom stoom deur turbines
    stoooooo-oooooooooo-oooooooom, laat dit bars!

    Stoom – Amandla Strydom.

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