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Within the medical arena there is increased pressure on budgets and financial accountability, with a significant trend for the sector to look again at how resources are used and where savings can be made.

One of the largest expenditures in most hospitals is the cost of purchasing or producing the various medical gases needed, such as Medical Air, Nitrogen, Oxygen and Nitrous Oxide. Often the usage and consumption of these gases is neither monitored nor measured or, whenever it is done, it is often a crude estimation, inaccurate and recorded only by pen and paper.

Most hospitals rely on the rate at which the cylinders (in which the gas is supplied) empty to determine the amount and rate of gas used. There are of course many issues associated with this method, such as:

  1. The amount of gas in a particular sized cylinder can vary greatly, even when directly delivered by the gas supplier
  2. Total gas consumption and peak times of consumption cannot be accurately determined
  3. Leaks can go undetected
  4. Specific point of use consumption is impossible to determine

This makes it very difficult to manage costs overall and to assign invoicing costs to individual departments and sections.

A company specialising in the design, installation and maintenance of gas systems was asked to install the medical gas network in a new hospital. An approach was made to Bronkhorst UK Ltd for the supply of gas meters which could then be communication-linked to the building maintenance system.

Thermal mass flow Instruments with integrated multi-functional displays were offered to fulfil both the accuracy and reliability requirements . As a result of their through-flow measurement (Constant Temperature Anemometry - CTA technology) the thermal mass flow instruments offered the additional benefits of no risk of clogging, no wear as there are no moving parts, minimal obstruction to the flow of the gas and hence ultra-low pressure drop, all based upon the fact that the instrument body is essentially a straight length of tube.

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In addition to the local integrated displays both 4…20 mA and RS232 output signals were available ensuring integration with the Building Management System (BMS). This gave the end user real time continuous data logging and remote alarming should the gas supply enter low- or high-flow status for any given event. As a double failsafe the instrument offers both on-board flow totalization and further hi/lo alarms.

The installation of the mass flow instruments for this hospital application provided the following benefits to the client:

1. On primary networks:

  • Separated invoicing for hospital/clinic/laboratory departments sharing the same source of medical gas
  • Monitoring and acquisition of consumption data
  • Leak detection within gas line, safety vent and medical gas source

2. On secondary networks:

  • Independent gas consumption invoicing between the health institution departments
  • Over-consumption detection
  • Monitoring and acquisition of consumption data
  • Leak detection within gas line

Subsequent installations across Europe have followed the trend of increased accountability by installing a Mass Flow Meter for the incoming bulk delivery, obtaining a totalized flow reading and cross matching this to the bulk invoice. This could be useful in the event of inadvertent errors or typos when a bulk delivery invoice is being raised.

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