Application Story

Taking the Lead in Lead Monitoring

Moeller’s Easy enables Bury Pumps to control lead monitoring system

Monitoring the levels of lead found in the domestic water supply has become extremely important as health fears increase and an EC Directive is introduced. Bury Pumps Ltd, a leader in specialist pump applications, has developed a test rig enabling Anglian Water to accurately predict the levels of lead coming out of our taps.

Providing the precision needed to control the rig is Moeller Electric's innovative Easy control relay, a simple, easy-to-use solution that is extremely effective.

We all want the highest quality of drinking water. With the UK's large stock of old domestic lead pipes, lead content in water is a particular problem facing water companies striving to provide safe drinking water. It has been further exacerbated by recent research showing that unborn babies and infants are more sensitive to lead than originally thought, stimulating the EC to cut the current amount of lead allowed in drinking water by 80%. The new drinking water directive (98/83/EC) requires a reduction from the present limit for lead in water at 50µg/litre to 25µg/litre by December 2003 and to 10µg/litre by 2013.

Over the next five years, water companies predict expenditure of £500 million on drinking water quality improvements, with more than 60% of spending on meeting the lead standard alone. To control levels of lead, water companies dose water with orthophosphoric acid which reacts with lead piping to provide a protective barrier, preventing more lead dissolving into the water. The optimum amount of orthophosphoric acid needed depends on many variables and can only be achieved by constant monitoring , particularly testing the susceptibility of the final water to picking up lead in domestic pipes.

Bury Pumps, based in Bury St Edmunds, Suffolk, working with Anglian Water has developed a lead test rig that mimics the environment in the water supply's lead pipes, allowing companies to accurately predict the levels of lead in water coming out of domestic taps. The unit automatically tests the final water, allowing water companies to continually adjust the optimum level of orthophosphoric acid, thus providing a cost effective means of achieving the standards for lead in water.

The rig comprises a three-metre length of lead pipe of half the nominal bore, through which water flows via a non-return valve and a flow meter. The system operates in three stages: flushing, stagnation and sampling.

Flushing This is the first stage of the operation where a solenoid valve is opened by the Easy relay allowing the sample water to clear the system and flow directly to drain.
Stagnation This stage is usually set to 30 minutes duration and represents the conditions of water under mains pressure in domestic lead pipes. Both solenoid valves are closed and the system pressurised to equal typical mains pressure. During this stage the lead will dissolve into the water.
Sampling After a set period of stagnation the sampling valve is actuated and water in the pipe fills up a container ready to be removed for sampling and analysis.

Typically, the sampling sequence involves switching on at 7.00am and off at 6.00pm. A Moeller Easy 618-AC-RC control relay with 12 inputs, 6 relay outputs and a built-in 24-hour timer controls the timing and actuates the valves for each stage. At the end of the process some of the stagnated water is collected in a conical plastic receiver for lead sampling.

The whole cycle is then repeated until turned off by the 24-hour timer. The flush, stagnate and sample times can be programmed into the Easy by simply pressing a few buttons.

David Vickery, Bury Pump's Engineering Manager, said: "Easy is an economical method of control compared to a more complex PLC solution. Its push button programming and clear LCD screen enables users to set times of the sampling operation quickly and easily. A PLC would require operators to carry around a laptop to change the sampling timing sequence – very inconvenient."

Flexible and quick programming is at the core of the sampling rig. Vickery comments: "To program the Easy takes about two minutes compared to a conventional PLC solution which can take about 30 minutes. This frees the operator's time to do other more pressing work. Of course, this ultimately makes operations more cost effective."

A particularly useful feature is that the sampling rig's operating program is stored on the Easy's EPROM. This can be transferred to any other Easy saving reprogramming, enabling users to store a set of preprogrammed chips which can be slotted simply into new Easy controlled sampling rigs as they are acquired. The main operating program is password protected to prevent accidental corruption. However, it can be changed through the Easy's push buttons as and when required. Alternatively, the operating program can be prepared and held on a PC. "We developed the core program on a PC and then downloaded it on to the Easy's EPROM. This saved considerable development time", added Vickery.

The lead sampling rig also specifies: up to 16 on and 16 off switching commands, a self cancelling on and off override and battery backup of the clock for up to 17 hours.

Vickery emphasised: "Our remit was to develop a flexible lead sampling system that allows water companies to continually monitor the level of lead in their final water and control the amount of orthophosphoric acid doping. The Easy control relay is the ideal control system, offering a cost effective and reliable solution which is simple to use in demanding field applications."

This page last updated: 10 January 2002