OFFSHORE PLATFORM FIRE SAFETY SPRINKLER SYSTEM DEPENDS ON LIQUID FLOW ASSURANCE SWITCH
Offshore platforms around the globe are essential to the production of oil/gas and the global energy supply chain, but they represent a daily hazardous operating environment to the employees that work there 24-x-7. The potential dangers range from a mix of toxic and combustible gases, including, but not limited to, deadly hydrogen sulfi de (H2
methane (CH4), and other mixed hydrocarbon gases that are easily fl ammable.
For these reasons, offshore platform work environments are governed by a web of complex international health and safety standards that always include requirements for gas and fl ame detectors, as well as automated fi re sprinkler systems that rely on seawater to douse fl ames before they are out of control. Serious accidents due to fi re have occurred far from shore on oil/gas platforms with disastrous results that include the tragic loss of life, catastrophic damage to equipment and severe pollution of the fragile marine environment.
In response to global health and safety standards, the designers, operators and owners of offshore platforms are constantly seeking innovative solutions to improve the reliability of their automated fi re sprinkler systems in order to assure effectiveness and reduce false alarms or their downtime. Operators aboard a platform need to be informed immediately both when gas or fl ames are detected, and also, importantly, when the automated fi re sprinkling system initiates operation to ensure control of the event has started and staff are evacuated to safe areas while minimizing the impact of any fi re.
The Problem
Under normal conditions in a fi re sprinkler system for an offshore platform the pipe remains fi lled with seawater. In the event of a fi re, the sprinklers are opened and the water is discharged to extinguish the fi re immediately. A typical offshore platform sprinkler installation is built with a 76 or 102 mm (3 or 4 inch) main line with branching of multiple, smaller diameter pipes that feed the individual sprinkler nodes.
Each individual sprinkler is fed by a much smaller line size of 6.35 or 12.7 mm (0.25 or 0.5 inch), which makes it diffi cult for fl ow sensors to detect and measure a very low fl ow of seawater in the main line if, for example, only one or two sprinklers are activated. It’s very important for the operational integrity of the system to detect even these very low fl ow rate changes so an alarm is generated even when a single sprinkler has been activated to initiate a fi re alarm.
In addition to low fl ow rates, the fl ow instrument chosen must also be capable of withstanding a high fl ow rate in the event that all connected sprinklers are activated simultaneously should an explosion and large fi re occur. The fi re sprinkler system is tested once a year, and during the test it be ensured that the fl ow sensors are operational and fl ow alarms are generated correctly.
The Solution
The system design engineers at a large engineering consulting fi rm contacted Fluid Components International (FCI) regarding their need to assure sprinkler system water fl ow for offshore platforms. The fi rm designs fi re safety sprinkler systems for operators around the globe including Europe, the Middle East and Asia.
The design engineers told the FCI application team that their fi re suppression system requires the platform’s operators to be alerted if the seawater’s fl ow rate on the main lines is interrupted or changes. The challenge was to fi nd a highly sensitive fl ow sensing switch capable of detecting very low fl ows with a continuously reliable and rugged design to withstand harsh, corrosive seawater and with agency HazardEx approvals for installation in a potentially explosive gas environment.
The design fi rm team provided the applications team at FCI with the following specifi cation requirements:
• Pipe diameter: 76- or 102-mm (3- or 4-inch) Schedule 40 pipe • Media: seawater
• Flow alarm level/trip Point 1: low fl ow detection of 0,3 m/sec [1 ft/sec] • Relay status: Energized when fl ow above trip point • Flow Alarm Level/Trip Point 2: Empty pipe detection (wet/dry)
After reviewing these requirements, the FCI application team recommended the company’s rugged thermal FLT93S Switch. It is designed with a fail-safe, dual alarm (SPDT) control circuit and provides multiple fi eld-selectable parameters such as the monitoring and alarm of low fl ow liquid or air while also supplying a non-linear process temperature measurement. The switch has many factory or in-fi eld set point variations including; high fl ow alarm, low fl ow alarm, point level detection wet/dry with temperature output, three-phase (water/oil/air) level interface, or fail-safe fl ow, level, or temperature.
The FLT93S Switch met all the engineering fi rm’s requirements with its superior low-fl ow detection. It easily recognizes very low liquid fl ow rates from 0,3 m/sec [1 ft/sec] when installed on either the 3-or 4-inch (Schedule 40) piping. For example, the primary fl ow alarm level trip point was set at 0,3 m/sec (1 ft/sec) to signal low fl ow conditions that would indicate either an actual fi re or a leak in the main line piping. The second alarm was set in this application for dry running conditions indicating an empty pipe due to a major break in the line or other interruption to the seawater supply.
S) to explosive
WWW.PETRO-ONLINE.COM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
