Mumbai, one of the 10 largest megacities in the world, has an exponentially expanding population of 12 million people. The Hydraulic Engineer’s Department of the Municipal Corporation of Greater Mumbai supplies about 375 million litres of water per day to Mumbai’s 12 million citizens. The water supply network in Mumbai is fed through trunk mains, reservoirs & tunnels. There are thousands of daily-operated control valves installed in the system. Engineers are always apprehensive about these valves which are operated 4-5 times daily for controlling the distribution of water across the city. They are operated at an upstream pressure of 80 PSI and a downstream pressure of 0 PSI with no water in the downstream for more than 5 Km of pipeline. However, due to the fast growth of infrastructure, the demand for water is growing substantially.
In the year 1983, the 2400 mm > 1350 mm > 1200 mm Ø Bandra west outlet (Pipeline) was laid from Veravali Hill Reservoir - III, Andheri (East) to Bandra (West). The total length of this outlet is approximately 11 Km. To regulate the water supply to an area with a population of around 1 million (appx. 2 million today), a control valve for daily operation was decided to be installed near Andheri fly-over bridge. At that time, senior officers from the Hydraulic Engineers department of MCGM, discussed the issue and decided to install a 1350 mm Ø Butterfly Valve for daily operation. It was a specially designed butterfly valve with a mild steel fabricated valve body and a fibre glass reinforced plastic internal coating. It was a new thought to go for the butterfly valve, instead of a traditional sluice valve, for a number of reasons. The butterfly valve is physically smaller and is approximately the third of the height of a traditional sluice valve, with a shorter face-to-face. Due to the size of the sluice valves they can therefore be awkward to install and maintain.
So, in 1984 the DN1350 Ø butterfly valve with a gear box operator was installed near Andheri fly-over bridge. Considering the high velocity and the static head of 84 lbs/ Sq. In at the upstream of the valve, it was necessary to have a high-rated gear box. The gear box had a velocity ratio of nearly 2200:1 and it was reducing the torque from 120,000 Nm to 100 Nm. But during its first opening operation, a very high velocity of water was creating substantial as well as loud vibration in the body of the valve. It resulted in considerable wear and tear to the gear box as well as the EPDM seal of the valve. These persistent problems were leading to the failure of the gear box and the wearing of seals, despite the gear box’s impressive velocity ratio. Up until 2013, the gear box and even the entire valve not only went through numerous maintenance schedules but also was replaced six times. MCGM engineers learned the hard way that the butterfly valves are unsuitable for regulating the water in such high volumes and pressures of water.
Considering the immense vibrations and noise, along with the frequent failure (almost once every 2 months) which was causing interruption of water supply to residents, it was concluded that the existing butterfly valve was unsuitable for regulating the water supply. The irregular water supply to 2 million people residing in the western suburbs of Mumbai was a very serious issue to be ignored. The Executive Engineer of the Mumbai Corporation stated that the massive torque requirements of 150,000 Nm were the prime reason for these breakdowns.
After securing the tender on the basis of their best response, Blackhall Engineering Ltd. analysed the problems and proposed a permanent maintenance-free solution. Blackhall, after assessing the site parameters, offered a specially designed Larner-Johnson® flow control valve to suit the chronic conditions. The valve was installed in March 2014. The valve operates at 18,000 Nm torque (i.e. 12% of the original torque used by butterfly valve). As a result of this substantial reduction, the valve operates without any of the vibrations and noise experienced previously.
One cannot argue with Blackhall’s Larner- Johnson® flow control valve design and its incomparable life span. The innovative feature of the Larner- Johnson® valve is its pilot-operated design. This design permits the flow control valve to utilise the flow line pressure for moving the plunger on the internal guides, ultimately requiring substantially lower torques for achieving the seal. Since the plunger is moved very gradually and gently using the line pressure, it becomes possible to implement a stainless steel metal-to-metal seal which is highly resistant to wear and tear, thus promising an extraordinary life span of more than 50 years with minimal service or maintenance requirements.
As seen in the pictures, Blackhall's Larner-Johnson® Valve was successfully installed by onsite engineers and commissioned by our Service Director Mr. David Richmond. Feedback from MCGM after 4 years is that the valve is operating excellently with extremely low torque - causing no vibrations or noise. Executive Engineer at MCGM comments;
"Initially it was unbelievable for us to see a valve operating at such a reduced amount of torque. It has been 4 years now and we are impressed with the kind of reliability and durability the valve works. BLACKHALL Engineering Ltd has supplied an important asset to 2 million people in Mumbai who rely on this valve for their daily water requirements. Apart from this, I found it very cost effective - after assessing its life and maintenance costs. The cheapest price is not always the most economical price, as in some cases expensive valves can turn out to be the most economical solution if they have a long life cycle. That’s the category where we fit Blackhall's Larner Johnson® Valve. "
The corporation was highly satisfied with the project and assigned a certificate to Blackhall for supplying a very reliable, durable and robust valve.
