Posted by Process Control Team on 25 Jul 2017
The quick, accurate, and inexpensive measurement of Trihalomethanes (THMs) creates numerous opportunities to improve the water treatment process. THM levels can be lowered throughout the distribution system and chemical usage can be optimized to save money. What’s more, quick process adjustments can be made to control THM formation when surface water Total Organic Carbon (TOC) characteristics alter due to seasonal or unusual weather conditions. Where before you might have had limited THM data, you can now greatly expand the sampling frequency and monitoring locations to help you better understand the THM formation characteristics of your water source, treatment process, and distribution system.Surface water supply matrix changes
Both human activities and seasonal changes can affect source water, altering the mineral characteristics of the water as well as the reactivity of its dissolved organic carbon. A water plant may observe no significant changes in the quantity of TOC due to seasonal events, but they may find their THM level has changed. Frequent measurements of THM can help operators better understand the reactivity changes of their source water.Coagulant evaluation test
A successful coagulation process depends on identifying the correct coagulant type and optimum dosage under suitable environmental conditions of pH and alkalinity such that the coagulant will remove the maximum TOC, UV254, and turbidity, and form easily settleable floc. However, without the ability to measure THM concentration of the finished water in real time, the plant operator will not know if the coagulation process has been optimized to also remove the maximum amount of THM precursors. With the ability to easily measure THM concentration in finished water, the plant operator can adjust the coagulation process to achieve minimal THM formation potential. Additionally, this allows the treatment plant to supply safe drinking water with the required level of disinfectant concentration while also maintaining lower DBP levels throughout the entire distribution system.Real-time monitoring of THM sampling locations
Trihalomethane formation in water distribution systems is a function of water travel time, temperature, and physiochemical and biological characteristics of pipe deposits within the distribution system. The real-time monitoring of THM at different sampling locations will help water distribution operators to identify problematic inorganic/organic pipe deposits that cause increased levels of THM formation.Water quality model evaluation/water quality trend
Hydraulic modeling of a water distribution system is an important tool for water quality management. In addition to basic hydraulic characteristics, modeling identifies water aging and predicts disinfectant decay and DBP formation. Incorporating new data from frequent THM analysis in combination with disinfectant level data will help plant operators build an improved hydraulic model for water quality trend analysis, providing critical information for more targeted and efficient water plant operation.Flushing program
Water quality levels throughout the distribution system are maintained by systematic flushing programs designed to reduce stationary water in dead end lines and increase flow volume to minimize water age. The distance of water from the water plant, dead ends in the pipe, and low water usage may cause water quality deterioration. Lower residual disinfectant levels indicate the need to flush, which can cause a significant water loss. By measuring THM concentration in addition to disinfectant levels, operators can better decide on the location and length of flushing to minimize treated water loss.Water age evaluation
Water age is emerging as an important issue due to increased THM formation in water distribution systems. Excessive contact time caused by dampened peak-hour demands, distribution piping configurations, areas of reduced water requirements, and fire protection storage can result in elevated THM concentration. Identifying and then reducing dead spaces and stagnation in water storage tanks and looping pipe configurations in water distribution systems will reduce water age. These actions can be triggered appropriately by monitoring THM levels in storage tanks and key locations in the distribution system.The Parker THM analyzers
Parker’s On-Line THM Analyzer and benchtop THM Analyzer are easy to operate, integrated Purge-and-Trap Gas Chromatographs (GC) that measure THM concentration at ppb levels in less than 30 minutes right at your own facility without tedious sample preparation.
This integrated system is a powerful tool that can help operators optimize water treatment at the plant and evaluate water age in the distribution system for improved control over the formation of THMs.
Pic. 1. Parker's On-Line THM Analyzer.
Pic. 2. Parker's benchtop THM Analyzer.
Article contributed by Kazi Hassan - technology development manager (water) at Parker Hannifin, Instrumentation Products Division.
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Since the NACE (National Association of Corrosion Engineers) MR0175 standard was updated to ISO status in December 2003, there has been an air of confusion on what and how products conform to NACE. Some manufacturers simply buried their heads and try to ignore the standard, some simply decided that they would not pursue NACE product related business, some only certify to old, out of date versions of the standard, and others simply used the wording of certain clauses within the standard as a way of supplying product from materials that do not actually meet the requirements of NACE MR0175.
Parker has taken NACE compliance very seriously and invested a lot of time to ensure that not only did we understand the consequences of the standard but what we actually put out to our customers in the market place was accurate and met the criteria of what the standard is advising the Oil and Gas Industry.
Engineers from Instrumentation Products Division Europe attended a conference organized by the authors of the NACE MR0175/ ISO 15156 document and arranged for one of the authors to visit our manufacturing facility at Barnstaple to discuss its implications and how we as a manufacturer of saleable goods should be certifying the materials we use for NACE compliant products.Declaration of Conformity
Managing emissions is a major challenge for many companies. In Europe alone, a typical refinery can lose between 600 and 10,000 tonnes of fugitive emissions every year; and the majority of those losses are estimated to be caused by plant equipment, such as process to instrument valves and small bore fluid system technologies.
Valve leakage is believed to account for around 50 per cent of emissions within the chemical and petrochemical industries. That can place a major financial burden on companies - not just due to potential plant inefficiency, but also the potential costs of repairing leaks, wasting energy and environmental fines.
Reducing emissions can help businesses to protect the environment, reduce waste and save valuable time and money in the process. Engineering, Procurement and Construction (EPC) and end users involved in commissioning may find it helpful to follow a series of checks - alongside any existing processes - to determine prospective supplier capability.Adherence to international Standard ISO 15848.
International standard ISO 15848 sets a requirement for zero emissions for processes involving hazardous fluids and volatile air pollutants. The standard is split into two parts:
ISO 15848 defines three leakage classifications that specify maximum leakage rates, with Class A being the most stringent.
Parker products have been compliant with ISO 15848 for some years now.
Pic.1. Lloyd’s Register verification for the Pro-Bloc® 15mm process to instrument valves dates back as far as July 2007.Verifications and third-party approvals.
Typical industry procurement practices require certificates of approval or third-party verifications as a condition of supply. Reputable valve manufacturers, including Parker, can provide signed and witnessed certificates - along with verification from industry-leading organisations and technical advisors such as Lloyds, TUV and DNV.
If verifications are provided by an unknown third party, engineers and procurement specialists may want to satisfy themselves with the quality and level of certification offered - ensuring that any named verifiers are trusted experts in their field. And it’s important that suppliers can provide access to any stated certification, as proof of capability and to ensure practices are up-to-date.
Experience supporting major companies and being on approved vendor lists can also be a useful indicator of supply quality. Manufacturers of process to instrument valves who are working with oil majors typically have to pass stringent pre-qualification checks and approval systems. For example, Shell’s robust enterprise framework agreement requires suppliers to:
Passing these tests is a strong indicator of supplier credentials. Parker is proud to have recently secured a five-year extension to its framework agreement with Shell following a recent factory audit and witness-tested Type Approval Test. The extension was secured due to Shell being satisfied with Parker products and service over the previous five years.
Pic.2. Parker’s MESC compliant Double Block and Bleed valve.Industry expertise and training.
In offshore applications, the implications of insufficient expertise or training can carry significant risk. It’s therefore imperative that any suppliers demonstrate their understanding of the business environment and relevant operations.
Asking suppliers for details of their testing practices and procedures, familiarity with legislation and adherence to industry standards will help to build a clear picture of suppliers’ relative experience and credentials.Suggested questions for potential suppliers.
EPC contract engineers and procurers commissioning process to instrument valves may find it helpful to consider the following areas when considering potential suppliers:
Article contributed by Jim Breeze - Flange Products Product Manager at Parker Hannifin, Instrumentation Products Division Europe.