HYDROELECTRIC FIELD MACHINING PROJECT - New Turbine Installation

Overview

Furmanite was recently hired to perform in situ machining on the new construction of a three turbine hydroelectric generation power plant installation on the Ohio River. The power plant houses three horizontal 29.3-MW bulb-type turbines, and generating units, with an estimated total rated capacity of 88 MW at a gross head of 25 feet. The Stay Cone flanges and associated mating parts were manufactured and machined in the OEM's workshop facilities and transported to the site. Due to the size, configuration, mechanical handling, transportation complexity, and installation limitations the final machined finishes required precise on-site machining to correctly align the enormous mating surfaces. With a proven history of performance, Furmanite's Integrated Mechanical Services Division, a worldwide leader in large dimension field machining, was hired for the in-situ field machining of the Stay Cone Vertical Flanges.   All three bulb turbine units were to be completed with the final required 3mm to 5mm of stock removal in the mating flange faces in which the massive flanges measured 17 feet inside diameter by 19 feet outside diameter.           Solution and Implementation Furmanite was hired by the general contractor for immediate assistance to resolve the misalignment issues which were creating significant assembly delays, and was having a major effect on the entire project delivery schedule. It was Furmanite's determination that with some engineering modifications to an existing large flange facing machine the customer's machining requirements could be completed accurately. Within a 10-day timeframe Furmanite engineered the modifications for the machine, manufactured the parts, and mobilized to the site.  Watch the video, here. Results   The machine was set to known datum points using laser tracker equipment. Machining was carefully undertaken with measurements taken frequently. All three unit Stay Cone Flanges were successfully machined and completed within a 21-day period. The tolerances achieved included perpendicularity over the full 19 feet Outside Diameter to within 0.2mm (0.0078"), and the overall flatness required was +/- 0.15mm (0.0059").

Leak Sealing - Shared Learning Opportunity

What happened?

During a leak sealing operation on 19 November 2013 in Belgium on a 16" MOV (Motor Operated Valve) a steam explosion occurred resulting in the death of the technicians performing the work. (Not Furmanite Employees)
 What went wrong?  
The incident occurred in Unit 72 (Continuous Catalytic Reforming) of the Antwerp Refinery. The line contained Boiler Feed Water operating at 70Bar/1,015 Psi and 280°C/536°F. While the workers were repumping the clamp/enclosure that was installed on the Bonnet of the valve, (the two workers were employed by an external contractor) all bonnet bolts suddenly failed. The valve bonnet was launched 25m/75ft into the production unit.

Background/Additional Information
 The clamp/enclosure was installed in 2011. This was the 7th (seventh) re-pump on the clamp/enclosure.

There is always a risk that when injecting at high pressures and temperatures, some of the older style compound ingredients or breakdown products in them may have previously been acting in a negative way on the internal parts of the system or the bolts.

There is a possibility that boiler feed water has chemicals in it that could have been acting in a negative way on the valve parts or bolts as well.

Furmanite has a policy that after 3 {three} repump’s, engineering has to be made aware of this and the job has to be given extra attention to evaluate any possible factors that could be causing the requirement for it to be re pumped again and to consider if there are any extra safety factors that we must be made aware of, or actions that should be taken.

Investigation Results

Immediate Causes
Apart from the actual rupturing of the bonnet bolts, the exact cause of this is still unknown and under investigation.

How do we prevent it from happening again?

In all cases when attempting to seal high pressure and high temperature leaks, extreme caution must be used at all times.

No matter what the type of job is, review the area and the situation and ensure that if something were to happen, you are not in the path of destruction, and have two easily accessible routes of escape.

Before re-pumping anything, always check the structural integrity and the tightness of the bolts on the clamps/enclosures, restraints. If there is any doubt as to their integrity, then do not proceed, consult engineering with your findings, and continue with a more complete review of the job.

As stated before, after the third re-pump engineering must be made aware of the situation so that a complete review can be made to determine if there is a requirement to change the sealant being used, change the procedure being used and for any new safety precautions that must now be put in place.

In light of this incident on a boiler feed water line and the nature of potential failure mechanisms and affects, we are mandating a new requirement to all Technicians.

Until further notice ALL Boiler Feedwater leak-sealing activities WILL need to be assessed by the appropriate Engineering Team before ANY work takes place on that system, item or component.

Please note this is for your safety and the safety of your fellow colleagues. Engineering will endeavor to cause as little disruption to your planned activities as is reasonable, but not at the cost of safety.
What actions do I take?
All Furmanite Techs to be issued with this Safety Alert. (SDC Managers Globally)

All workshop supervisors / SDC Managers to ensure that leak sealing techs have access to a complete set of safety information on the compounds / substances that they use in their day-to-day operations and that their employees have been given suitable and sufficient information and instruction on their safe use. (SDC Managers Globally)

All Leak Sealing Procedures / risk assessments to be altered to reflect this safety alert. (Process Integrity Service Line Leadership)

All leak sealing class rooms training or CBT to include reference to the third repump rule and its requirements. (Global Engineering Manager)

Engineering Teams providing Chemchecks and or engineering reviews are to make techs aware of the potential problems associated with working on Boiler Feedwater (with its chemical additives) and the effect it may have on the internal valve parts and associated bolting. (Engineering dept. manager)