A Comparison of Rate Compensated Heat Detector Test Methods
Overview of Rate Compensated Fire Detectors
Rate compensated heat detectors were first developed by Wilfred J. Turenne in the 1920s and have been mass-produced since the 1950s. These detectors are engineered to react to both a specific temperature and the rate of temperature increase, making them uniquely reliable for industrial use. Common models include Fenwal Detect-A-Fire (DAF) and Thermotech 302 Series detectors.
Testing Requirements & Industry Standards
Detector Testing and Calibration Guidelines
Rate compensated detectors must be tested regularly to ensure they function accurately without damage.
- NFPA (National Fire Protection Association)
Heat test shall be performed annually with a heat source per the manufacturer’s recommendations for response within 1 minute. A test method shall be used that is recommended by the manufacturer or other method shall be used that will not damage the…temperature element.
- Code of Federal Regulations
All fire- (flame, heat, or smoke) detection systems shall be tested for operation and recalibrated every 3 months provided that testing can be performed in a non-destructive manner. Open flame or devices operating at temperatures which could ignite a methane-air mixture shall not be used.
- Bureau of Ocean Energy Management, Regulation and Enforcement
(Formerly The Minerals Management Service MMS)
Potential Incident of Non-compliance – PINC P-177:
…ARE OPEN FLAME OR DEVICES OPERATING AT TEMPERATURES WHICH COULD IGNITE A METHANE-AIR MIXTURE NOT USED FOR TESTING?
Authority: 804(a)(9) Enforcement Action: C
INSPECTION PROCEDURE:
1. Review with operator the method used to test each fire-detection system.
2. Inspect device used in test for presence of open flame or temperature that exceeds 1100 F.
IF NONCOMPLIANCE EXISTS:
Issue a component shut-in (C) INC for the activity protected by each fire-detection system when the testing device uses an open flame or exceeds 1100 F.
Manufacturer Test Recommendations
Manufacturers stress the importance of non-destructive testing to prevent altering the detector’s set point. High-temperature tools like blowtorches or soldering irons are prohibited, and the test temperature should never exceed the set point by more than 100°F (55°C). Approved testing methods simulate factory conditions using aluminum blocks; alternative mediums like air, water, or sand baths are not allowed. If a detector has been exposed to fire or intense heat, replacement is recommended.
Side-by-Side Comparison of Test Methods
Test Method
Limitations / Risks
Heat Gun / Hair Dryer
- Only practical at low heights (most detectors are mounted on ceiling)
- Does not provide indication of actual trip point
- Power cords must be carried around to each area to be tested
- High surface temperature (burn hazard)
- High temperature (destructive, will permanently shift set point)
Friction
(Such as Rope Wrapped Around Detector)
- Only practical at low heights (most detectors are mounted on ceiling)
- Does not provide indication of actual trip point
- Damage to shell of detector
Boiling Water
- Only practical at low heights (most detectors are mounted on ceiling)
- Does not provide indication of actual trip point
- Damage to shell of detector
- Scalding burn hazard
Industrial Soldering Iron
(Large Iron Without Tip)
- Can be heated up and used for several minutes beforeit needs to be plugged in again
- Does not provide indication of actual trip point
- Temperature of iron exceeds 1000°F
- Will cause the sensors set point to permanently shift
- Extreme burn hazard
- Dangerous ignition source-(detector coated with oil splatter) in vicinity of potential gases
- Detector shell is often dented, bent, or otherwise distorted from rough contact with iron. This usually shifts the detector set point high, but goes un-noticed due to the high test temperature of the iron.
Exothermic
(Chemical Reaction)
- Messy/ inconvenient
- Does not work at high temp (over 190°F)
- Does not provide indication of detectors actual trip point
- Users must constantly buy more chemical
Aluminum Test Block
(Bench Test)
- Accurate calibration and function checking up to 600°F
- Sensitivity test- trip point verified
- Bench test unit, sensor must be physically removed for test
- Safety risk- Technician must climb ladders or scaffolding to R&R detector
- Expensive – Labor to R&R detector, cost of tool, replacement detectors
Why the HST Series Heat Detector Tester is the Preferred Method
The HST Series Heat Detector Tester combines portability, safety, and precision for field testing. It is ideal for use in safety-critical environments where destructive testing is not allowed. The HST enables technicians to perform reliable tests at ceiling height without disassembling detectors or climbing ladders. With multiple factory-set temperatures and a low surface heat profile, the HST Series ensures sensors are evaluated without compromising their calibration.
Designed specifically for rate-compensated probe-type heat detectors, the HST provides:
- Safe, low surface temperature
- Non-destructive, controlled test temperature will not damage sensors
- Test temperatures up to 950°F
- Multi-temperature , choose the exact temperature for sensor to be tested
- Portable tool - long life battery - tests sensors in place
- Simple & easy to use up to 30+ feet overhead
- Control unit monitors temperature and test progress and provides visual indication of temperature and test progress
- Sensitivity check- Verifies that sensor trips at temperature no higher than the manufacturers rated trip point
