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Do you know your fluid?

Do you know your fluid? Is it what you think it is? Is it from a known source?

Viscosity, varies with temperature. Is flow measurement going to be affected by viscosity change due to temperature anyway? Might be if the temperature range is large and it’s a Variable Area meter… Will the fluid be changed through the life of the system, introducing different viscosities; meter choice is important here.
Viscosity change over time. due to volatility of light compounds it’s likely, especially if exposed to the atmosphere, that viscosity will increase over time. Possibly if water is leaking into the flow stream or condensation in the process that the viscosity will decrease.
Viscosity changes due to pressure. These are known but fairly small changes compared with temperature effects. Viscosity can double between atmospheric pressure and 2,500bar.
Specific Gravity, Density. These are often quoted in Material Safety Data Sheets (MSDS). For some flowmeters it’s irrelevant, especially if the measurement principle is volumetric; for others, like VA it’s fundamental. And remember density changes with temperature. In general, if you want a mass flow rate or total then use a mass flowmeter (and vice versa).
Thixotropic? A shear sensitive liquid can be tricky for some measurement principles. To preserve the fluid at normal viscosity the rate may have to radically reduced. Typical thixotropic liquids encountered are paints. When stirred they change from a ‘gel’ to a more free flowing liquid.
Corrosion issues: chemical compatibility. Perhaps the first property that is investigated in meter selection is the chemical nature of the fluid being measured. Is it going to corrode any of the components or will it react with the materials and change some dimensions or shape? If a table found on the internet indicates that polypropylene is ‘compatible’ with fluid X will it be suitable for some close fitting parts where just a 1% expansion will stop the meter going round. 1% may indicate, to some people, that it is compatible.
Build up, formation. Slow or fast deposition on the inside of the pipe and other, more sensitive parts, inside a flowmeter may affect the internal diameter used for rate calculations on velocity based devices or the weight of a rotating part or simply stop a part meshing or rotating.
Solids content and solids size. Generally expressed as a percentage, the amount of particulate and the size of that particulate will govern the metering method. And it may not be obviously so. Some of the latest paints have small amounts of additive to give the paint a special quality. These will block a tightly toleranced PD meter or it’s bearings.
Filter size. Is it filtered? Is the filter mesh in the filter bowl or has it been removed because it keeps clogging up?! What level of filtration, NAS class, mesh size, is designed in and what level has been achieved. Is it well filtered but then stored in an open container?
Lubricity. This parameter is frequently ignored and frequently not known. It can have an effect on some flowmeters.
Homogeneous? It’s usually taken for granted that fluids are homogenous i.e. the same consistency at any point. A typical non-homogeneity is air entrainment, perhaps a few bubbles or a stream of bubbles. In extremis, this might be slugs of air passing through. Most flowmeters can’t cope with this phenomena but some make a decent estimation and more than a few will recover after the air passes.
Anodic acceleration of corrosion. This problem occurs when the fluid acts in concert with two dissimilar materials in the pipeline – for example, the flowmeter body and the pipework. The measured fluid acts as an electrolyte, depositing or removing material depending whether the materials act as anodes or cathodes. In some instances another wetted part may see accelerated corrosion.

All in all, consult the specialists. www.litremeter.com

Ten top tips for flowmeter selection.

Slim line customisation

Litre Meter’s ability to highly customise its meters has led to the company winning a significant order to supply meters to a company that produces hydraulic systems to the oil and gas industry. The fluid to be measured was Castrol Transaqua HT 2, with a viscosity of 3,95 cSt at 20 degree Celsius. The meters were bespoke slimline ones with a wide turn-down to allow for additional meters on a skid.

VFF positive displacement meters had to be made to operate at different pressures and flow ranges with different connections ranging from a VFF8 meter with a design pressure of 44 Bar, a scale of 0.3-30L/min with 25mm Female BSPP or equivalent size connections up to HP20 Flowmeters designed to work at a pressure of 950 Bar with a scale of 0.1-10L/min and 3/8” MP Autoclave connections.

All the flowmeters were located and certified for in Zone 2, Gas group IIB and Temperature class T3 so had to be EEx D or E. The minimum accuracy had to be within ±1.0% of full scale and the meters were constructed from 316SS quality stainless steel for all wetted parts.

The solutions provided were:

VFF8/690bar/AGPVD/V/9/16″AE MP

VFF8/1035Bar/AGPVD/V/9/16AE MP

HF20/207Bar/AGPDV/V/1″NPT all with

Fpod-RS-15-OC-I-H1-ATEX-V

Significantly we were able to offer measurement over the whole of the flow ranges required which competing flowmeter manufacturers were not able to deliver. In addition, the bespoke slimline VFF8 1035bar on drawing enabled the end user to get an additional meter on the skid without having to increase the available space.

Safety research highlighting key ‘drivers’

Results of our first survey into safety issue in the oil and gas industry have shown that concerns over risks to personnel and the environment are key drivers for the implementation of international safety standards for instrumentation.

It will be interesting to see how the results of that survey ? which concentrated on Safety Integrity Levels (SIL) ? compare with the results of the second (still current) survey which focuses on the Pressure Equipment Director (PED). You can take part in our PED survey until 5 September by going to http://tiny.cc/ped. One lucky participant will win a Kindle for taking part.

Our ‘SIL survey’ gathered the opinions of senior engineers worldwide with technical design and management roles within their organisations. It showed that when specifying flowmeters and other instruments, environmental safety (70 per cent) was cited as the main reason for safety standard compliance, followed by business-critical concerns including personnel safety (59 per cent) and maintaining process integrity (65 per cent).

Risks of injury to personnel (70 per cent), risk of explosion (65 per cent) and damage to the environment (50 per cent) were the chief concerns relating to the consequences of equipment failure. Business concerns including costs of shutdown (25 per cent) and damage to equipment (15 per cent) were of less significance.

While the majority of companies in the oil and gas sector comply with an international safety standard for instrument specification a significant number ? almost 40 per cent ? do not, the survey found. However, most of these stated that they will be seeking to comply with an international safety standard in the future where relevant.

One of the aims of the research was to find out to what extent engineers use SIL in specifying equipment and what reliance they place upon it.

Almost 40 per cent said that SIL level 1 was the minimum acceptable for instrumentation in their operations with 22 per cent citing level 2, 26 per cent stating level 3 and just 13 per cent saying that the highest level (level 4) is the minimum acceptable.

We wanted to make sure that our manufacturing focus is on safety in relation to both the environment and industry trends. These figures show that by complying with SIL we have a reliable benchmark for safety and reliability.

SIL was considered to be an effective measure of safety performance by 70 per cent of respondents but 54 per cent believed that a lack of consistency in applying SIL across all functional safety standards significantly affects trust in products designed to work in particular SIL level environments.

Now we are asking a similar range of questions about PED ?and with a similar purpose.

There has been increased focus on safety issues in the offshore sector over recent years. We want to make sure that our manufacturing focus is on safety in relation to both the environment and industry trends.

To take the PED survey visit http://tiny.cc/ped and spend just a few minutes answering the questions.

SIL is the degree of likelihood that a safety instrumented function will operate effectively when it is required to. Four SILs are defined within the European Functional Safety standards based on the IEC 61508 standard, SIL 4 being the most dependable and SIL 1 being the least, taking into account such things as the development process and safety life cycle management.

Chemical injection – from Africa to Arctic

Two articles in the current issue of Offshore magazine cover very different areas of the world ? West Africa and the Arctic.

They also cover very different scenarios. One is talking about ‘brownfield’ development – extending the life of existing fields and brining new reserves online through existing infrastructure. The other is focused on new technologies and challenges in safely exploiting hitherto unreachable reserves.

The common element is that both articles mention chemical injection as a key technology. This is, of course, an area in which Litre Meter has considerable experience.

Over the past year we have shipped a large number of meters to be used subsea, on a variety of chemicals, over a wide range of flows at high pressure and calibrated at specific viscosities. For example, Litre Meter rotary piston flow meters are part of systems used to control the amount of ‘antifreeze’ injected into pipelines at high pressure (430 bar) in subsea gas exploration on fields in the Caspian Sea and the North Sea.

‘Antifreeze’ fluids like methanol are used as thermodynamic inhibitors, which lower the freezing point of gas hydrate. They are injected into pipelines where there is a risk of hydrates (dew) forming then freezing at low temperature.

The antifreeze prevents gas hydrates solidifying as crystals and blocking pipelines – which can result in a costly shutdown and the risk of explosion or unintended release of hydrocarbons into the environment.

Litre Meter has also recently shipped flowmeters for use in chemical injection skids on a number of fields in the Gulf of Mexico and the Persian Gulf off Dubai. These meters are used in the flow measurement of wax dispersants and pour point depressants (PPD) to control their use to a very high tolerance.

Wax dispersants break apart and prevent the reformation of hydrocarbon sludge deposits and improve flow by reducing the viscosity of the fluid. PPDs are used to reduce the viscosity of oil and to maintain flow rate by preventing the build-up of wax crystals at low temperatures.

Sludge deposits are typically composed of varying concentrations of hydrocarbon, asphaltene, paraffin, water and inorganic materials. They are commonly found in storage tanks and vessels, production and transportation pipelines, process systems and hydrocarbon-producing formations where they have an adverse effect on the flow of crude oil from the well head.

Our expertise is nicely summarised in our new chemical injection brochure which highlights the enormous success of the VFF meter over the past few years in solving chemical injection measurement problems around the world.

With 3,000 VFFs in active use on chemical injection Litre Meter has demonstrated a depth of experience and knowledge that is unmatched in the low flow arena. The brochure provides further detail of the VFF range in one eight-page document.