Casella gets personal with pumps

5 Jan 2016

The UK offshore industry employs an estimated 33,664 people, according to 2014/15 statistics, who are exposed to a range of occupational health and respiratory risks including exposure to hazardous substances.

Monitoring of these hazardous substances uses personal sampling pumps and the recognised manufacturing standard for pumps, ISO13137, should ensure that all pumps operate to the same high level. With its vast experience in scientific instrumentation, dating back to the 18th century, Casella brings together its expertise in monitoring occupational dust levels to explain that not all air sampling pumps are the same. Therefore if you are in the market to purchase a new pump, here are the seven things you should keep in mind to make the right decision. 

A sampling pump’s size and weight are key and also its connectivity and ability to access data, much the same as a mobile phone, but in addition to that are considerations of flow rate stability, pulsation and back pressure capability.  Also important is the environment that you’re working in; the temperature, the barometric pressure and the relative humidity, and also the filter media chosen.  These factors impact upon the wearer, the occupational hygienist and most importantly upon the data set that’s produced.

1.       Battery life

Firstly, a personal sampling pump’s battery life must be able to maintain operation throughout a monitoring period. However, due to the variable nature of the offshore oil and gas environment, the sampling pump can be put under changeable amounts of operating stress during a single monitoring period. As the filter media becomes loaded with sample, the pump has to draw harder to overcome backpressure and this in turn draws more power from the battery.

 

As a result, Li-Ion batteries are now starting to be used in the latest personal sampling pumps. Li-Ion batteries have significant advantages over traditional NiMH and NiCd batteries; they have the highest energy density meaning that you need fewer cells and this means a smaller more lightweight pump.  Li-Ion batteries also do not suffer from the ‘memory effect’ (where only part of the battery charge is usable) or lose charge through storage to the same extent as the other types.  This means that you do not have to cycle the batteries regularly or implement a battery management procedure.

 

 

2.       Wearability

Of course, the wearability of a personal sampling pump is essential for making a monitoring regime as non-disruptive as possible to the worker. In the past, there have been instances where workers have removed the pump and put it in their locker until the end of the shift, so the latest generation of pumps include a motion sensor.   This ensures that the pump has been worn and that the sample is therefore valid. Choose a pump that can be worn comfortably by a variety of wearers; from large men to small women, for instance, to help in their engagement with the monitoring process.  Also consider your need for decontamination, how waterproof it is.  Latest designs are at IP65.  Additional protection in harsh environments is vital for the offshore oil and gas industry.

 

3.       Ignition and environment

The possibility for explosive situations in the oil and gas industry means it is vital that the pump must be intrinsically safe and not be a source of ignition. At the centre of the need for intrinsic safety is the part played by electronic design. The definition of this from the standard IEC79-11 is:

 

“A circuit in which any spark or thermal effect produced in the condition specified in this International Standard, which include normal operation and specified fault conditions, is not capable of causing ignition in a given explosive gas atmosphere.”

 

Manufacturers must incorporate protective components into their circuitry at the very earliest stages of design. This protection of course has an impact on the potential performance of the pump, for example, by limiting power to motor to ensure no spark and batteries are generally encapsulated, thus having an impact on size.  The latest designs of pumps include mechanisms in the circuitry to harness potential losses. Look out for the I.S. markings on your pump to ensure compliance.

 

4.       Back Pressure Capability

By far the biggest factor to consider in the operational capabilities of your personal sampling pump is the choice of filter media.  The smaller the diameter and the pore size of your filter and the greater the flow rate, the greater the back pressure exerted and the harder the motor needs to work.  Furthermore, as the media becomes loaded during the course of the sampling, back pressure increases still.

 

Membrane filters, as opposed to standard gravimetric GFA filters exert more back pressure and so if using these filters routinely, check the back pressure capabilities specified by your pump manufacturer.  Will it cope?

 

 

5.       Pulsation and air flow

The ISO13137:2013 standard requires that the pulsation of a personal sampling pump “shall not exceed 10% of the flow rate.” A pulsation measurement shows the difference in air flow between cycles; through every cycle as the pump draws air in and expels it simultaneously, this exchange process causes an uneven flow.  A large pulsation value means that if you are using a cyclone head for collecting respirable samples, the flow becomes interrupted. The flow for cyclone heads must be exactly controlled because this affects the size cut performance meaning less sample is collected and this obviously has an effect on your results.  Even when collecting the Inhalable fraction, pulsation has a serious effect with sample being deposited on the walls of the head instead of a filter.  To combat this effect, manufacturers include pulsation dampeners which are rubber diaphragms that act as extra reservoirs of air to smooth the flow.  Ensure that the pulsation values are within specification for your chosen pump.

 

In line with the standard and flow control, most pumps control the flow of air through the pump by means of a ‘Constant Flow’ mechanism.  As back pressure increases, the pump detects the change and alters the flow accordingly.  According to ISO13137 this should be within ±5% of the flow set.  A constant flow ensures that you can be confident in the volume data for your exposure calculations. 

 

6.       Constant Pressure Control

An additional method of control of flow is ‘Constant Pressure’ Control which is primarily used for low flow applications and gives the possibility of taking multiple samples. This method controls the flow rate by holding a constant pressure level in the tubing between the samplers and the pump. This means that if one of the samplers became blocked or shut off completely, the flow rate in the other samplers remains constant. If this were a ‘Constant Flow’ control system, the pump would sense the drop in total flow from one of the samplers and the motor would speed up to compensate. For many pumps, in order to do low flow measurement you would purchase a separate ‘Constant Pressure Controller’.  If you do a lot of low flow measurements it is worth investing in a pump which has this built in.

 

7.       Connectivity and Bluetooth®

Whichever pump you choose, in the wider world, the use of smartphones and mobile devices are commonplace and it is unsurprising that this trend filters down into monitoring equipment.  The use of Bluetooth® low energy technology means that it can be included in pump designs without draining the battery. This means that the occupational hygienist can remotely monitor, control and email data from the pump from their mobile phone without having to disturb the worker. The unique locations of offshore oil and gas sites make this remote technology an ideal investment for vital health and safety monitoring.

 

All of these seven factors are clearly a fine balancing act to achieve for product developers and it is important that these factors, alongside the broad and diverse environmental conditions in the oil and gas industry are at the forefront of the health and safety professional’s understanding. Casella’s extensive experience allows us to provide quality and highly suitable products to the industry, while also offering the knowledge and expertise that once made us the choice of Charles Darwin and now make us the choice of multiple industries worldwide.

Casella
Website
T: 01234 844100

Regent House
Wolseley Road
Kempston
MK42 8JY
Bedford, Bedfordshire
United Kingdom

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