Case Study: Tempered Water for Safety Wash Devices
Application to an industrial processing plant.
Introduction
This presentation demonstrates the methods and materials required for turnkey design and installation of equipment to provide tepid water for safety equipment in recognition of equipment location, system size, and frequency of use.
This presentation will cover:
OSHA first-aid requirements and ANSI Z358.1 standards regarding safety wash devices
Design considerations for three generalized applications
Equipment summary for each application
System verification and documentation description
Industry Safety Standards
OSHA Requirements
1910.151(c): Where the eyes or body of any person may be exposed to injurious corrosive materials, suitable facilities for quick drenching or flushing of the eyes and body shall be provided within the work area for immediate emergency use.
Safety wash devices are intended as the third line of defense following a well-designed workspace and proper protection equipment
OSHA does not provide specification of:
Drench or flush equipment
Water temperature, pressure or flow, which is dependent on the equipment chosen.
Placer Process customer mandated tempered water
Tempered water defined as 60-100°F
ANSI Z358.1-2004
Specifically defines equipment requirements and water flow, temperature and pressure
ANSI Z358.1-2004 Detail
Emergency safety wash equipment
Locate within 10 seconds of hazard (no obstruction)
Strong acids, caustics or highly reactive chemicals need adjacent equipment
Drainage should not create a hazard itself (puddle or freeze)
Tepid water is generally defined as 60-100°F
Warning: Increased temperature could increase a harmful chemical reaction rate. Therefore, research each hazard individually
Over 100°F can affect sensitive tissue (eyes), under 60°F can cause hypothermia
Equipment specifications
Minimum supply pressure to all equipment is 30 PSIG
Minimum volumetric flow for:
Emergency shower is 20 GPM
Eye/face-wash is 3 GPM
Drench hose or eyewash is 0.4 GPM
Laboratory Application
Sink-mounted handheld eyewashes or drench hoses
If domestic hot water is available, then a tempering valve for each location is sufficient
If no hot water is available, a thermostatically controlled tankless electric water heater is required for each location
A more robust system is required for emergency showers
Laboratory Equipment
Small tempering valve (up to 3 GPM):
Bi-metal mixing device
Hot and cold inlet manual shut-off with integrated strainers
Full cold bypass if manual temperature set-point is breached
Example: Guardian G3600
Tankless electric water heater (up to 3 GPM):
Thermostatic temperature control
Instantaneous tepid water
High amperage draw
Example: Eemax EX144T2
Laboratory Diagram
Small System Application
Few, close emergency devices (including showers), ideal for physically isolated locations
Choices for a common heated water source
120 gallon traditional water electric water heater
Industrial tankless electric water heater
Choices for water tempering valves
Centralized mixing valve to blend hot and cold water to 80°F, plumb a tepid water header pipe to each emergency device
Individual mixing valves at each location to blend hot and cold water to 80°F, requires plumbing a hot water header pipe to each emergency device and using the existing cold water supply
Small System Equipment
Tempering valve (up to 20 GPM):
Bi-metal mixing device
Hot and cold inlet manual shut-off with integrated strainers
Full cold bypass if manual temperature set-point is breached
Example: Guardian G3700
Tankless electric water heater (up to 20 GPM):
Thermostatic temperature control
Instantaneous tepid water
High amperage draw
Example: Eemax EX720T12
Small System Equipment
Electric water heater (120 gallon tank)
Sized to supply 8 GPM of 120°F water to mix valve for 15 minutes
Low wattage copper immersion heating element
Immersion thermostat
High temperature energy cut-off and temperature and pressure relief valve
Small footprint 30” x 24” (48” tall)
Example: Lochinvar HCA
Required accessories:
Solation valves and strainers
Temperature indicator
Pressure regulation, if necessary
Small System Diagram
Large System Application
Most systems are designed for single occurrence only, but each application is researched to confirm that assumption
Choices for a centralized source of tepid water:
Traditional electric water heaters with 120 gallon tank recommended
Includes a local tempering valve to blend hot and cold water
Implement a tepid water circulation header.
Minimize pipe length to individual emergency devices to prevent water stagnation
Small recirculation pump overcomes head loss through loop at a low flow rate (~5 GPM)
Provides near instantaneous tepid water supply
Large System Equipment
Tempering skid
120 gallon electric water heater with low wattage copper immersion heating element
Tempering valve with redundant cold water anti-scald bypass
Dual element thermostat with manual reset hi-limit protection
Integrated expansion tank (also has temperature and pressure relief valve)
4’ x 5’ skid with Schedule 40 galvanized piping with brass and stainless steel valves
Re-circulation accessories
Small circulation pump
Isolation and check valves
Pressure regulation, if necessary
Large System Diagram
Summary of Services
Placer Process Systems, Inc. provides turnkey design and installation of equipment to provide tepid water for safety equipment, which fulfills OSHA and customer standards.
Pre-construction verification achieved with a software flow model developed in AFT Fathom
Model is accurately designed to match site conditions (temperature, piping layout, existing emergency device type and location)
Provides reassurance that the desired pressure and flow requirements are met
Example included in appendix gives the worst-case scenario conditions with results from running the model
Emergency devices are audited for location, condition and performance before design to identify any compliance gaps
Tepid water system installation is fully documented with:
As-built P&ID’s and site layout drawings
AFT Fathom flow model verification results
Tempering system and relevant piping photographs
Complete installation and operation manuals with brochures attached for all new equipment
