© Drägerwerk AG & Co. KGaA 1

Planning a temporary refuge in the oil and gas industry raises a number of questions for safety engineers: How do you ensure that sufficient breathing air is available–even for extended periods and a large number of persons? Which system delivers the best and safest solution for the particular requi-rements? And what about cost-effectiveness? Our article provides basic information to reach a safe decision.

Ventilation of temporary refuges: filtration protection or isolation protection? D

-585

94-2

012

© Drägerwerk AG & Co. KGaA 2

Ventilation of temporary refuges

up to far beyond 10,000 ppm or more in the case of leakages or other incidents, it has to be ensured that the employees can find refuge at a place, where they are sealed off from the contaminated atmosphere in a reliable way and are also protected from exter-nal influences such as explosions or fire. “Clear recommendations exist for breathing apparatus solutions to be used outside on the plant. The question, which protection principle is the best solution for a temporary refuge during a specific scenario, on the other hand, usually needs to be answered by the planner alone”, says Frank Pietrowski. It is therefore important to develop a basic understan-ding of the different technical approaches and their advantages and disadvantages.

If an alarm is triggered on a production plant or refinery, employees should be able to escape quickly. But what if this is not possible? Rough terrain on the exterior, fenced-off areas or, in the case of offshore plants, simply the fact that the platform is surrounded by water and located many miles from the shore, can limit or prevent a safe escape from the danger area.

A temporary refuge is defined as “a place or places where personnel will be adequately protected from relevant hazards while they remain on an installation following a major incident, and from where they will have access to the communications, monitoring and control equip-ment necessary to ensure their personal safety, and from where, if necessary, safe and complete evacuation can be effected.”

The question, which requirements such “adequate temporary refu-ge” should meet and where it should be located always has to be answered on the basis of a plant-specific risk analysis. However, the various national or international regulations only give few statements on the specific implementation. In API 753, the American Petroleum Institute, for example, provides some information on the location of temporary refuges on plants–strictly speaking, however, these only apply to onshore process plants. “For the oil and gas industry, there is no standard that gives definite instructions on how to de-sign a temporary refuge with regard to gas protection”, says Frank Pietrowski, Business Development Manager at Dräger Engineered Solutions. “To date, safety engineers do not even find specific guide-lines for basic matters such as construction and equipment.” One of the questions regards the issue of how the persons in the temporary refuge will be protected from toxic gases in the external atmosphere and be supplied with breathing air for an extended period. Especially on acid gas and oil fields, where hydrogen sulphide gas can in some cases leak out in extremely high concentrations of several 100 ppm

Frank Pietrowski, Business Development Manager Petro and Chemical Industry at Dräger Engineered Solutions and Professional for Breathing Gas Systems

“

”

In the end that is a question concerning the philosophyon security that is prevalent on the individual plant.

© Drägerwerk AG & Co. KGaA 3

Ventilation of temporary refuges

Experiences with filter systems go back a long way: The first fore-runner for the ventilation of civil protection installations was develo-ped as early as the beginning of the 19th century. Today, filter systems for temporary refuges in the oil and gas indus-try are usually operated in connection with air conditioning systems (HVAC). The protection principle is based on the fact that overpres-sure is generated in the temporary refuge due to a ventilation solution, which ensures that external contamination remains on the outside. During this procedure, outside air is drawn in from an uncontaminated area of the plant, is cleaned as thoroughly as possible via a filter line and is then “pressed” into the inside of the temporary refuge. In the

case of H2S contamination, uncontaminated air is attempted to be drawn in from higher areas, for example via vertical air intakes.

For this procedure, a filter system adequate for the respective ha-zardous materials as well as a gas measurement system before and after the filter are required, in order to check the concentration and detect any filter damages early enough. A filtration protection sys-tem requires constant power supply in order to build up overpres-sure against toxic gases from the outside–during normal operation and especially in emergency mode. In some cases, this can cause problems, if the plant is located in an explosive atmosphere.

Filtration protection: a classic with complex requirements

Protection through filtration: depending on ambient air

Pover = positive pressurePI = internal pressurePN = normal pressure