Benjamin Ditch

Characterization of mist sprays using a phase-doppler particle analyzer and an iso-kinetic sampling probe

A method for quantifying droplet fluxes of a water mist spray uses different measuring apparatuses and compares the measurements of the two apparatuses with one another. One of the measuring apparatuses is an iso-kinetic sampling probe in which the air velocity of the portion of the water spray mist entering the probe is made equal to the air velocity of the water mist spray around the probe by connecting a source of vacuum to the probe. The drops of the spray entering the probe are prevented from passing out of the probe. The air velocity of the spray entering the probe is measured by an anemometer, the drops of the entering spray are collected in a reservoir, and the depth of water in the reservoir is measured by a differential pressure transducer. The output of the pressure transducer is sent to a computer that calculates the water collection rate based on the sectional area of the probe opening and the water collection rate in the reservoir.

The Skip-resistant Sprinkler Concept — An Experimental Evaluation

A sprinkler with a shield designed to mitigate drop impingement from nearby operating sprinklers is shown experimentally to reduce skipping as compared to the same sprinkler without a shield. As described in a companion article, a model for the response time of a shielded sprinkler has been developed and validated with a Plunge Tunnel apparatus. In this article, results from intermediate-scale spray fire tests employing Froude modeling principles with a 1 : 3 scale ratio are used to evaluate sprinkler performance both with and without the shield. By comparing the operation times of adjacent shielded and unshielded sprinklers, the intermediate-scale tests can identify test arrangements where the shielded sprinkler operates while the unshielded sprinkler does not operate. The identified arrangements are then used in a full-scale environment where a series of pan fire tests serve as a proof-of-concept that proper shielding of a sprinkler can reduce skipping in terms of both the sprinkler operation pattern and total number of sprinkler operations. This study successfully demonstrates that proper shielding of a sprinkler can significantly reduce skipping.

The fire hazard of an ethanol process facility

A large release of high purity ethanol has been shown to pose a significant hazard to the structure and sensitive equipment of an unprotected process facility. A new methodology was developed that provides a practical means of measuring the maximum heat flux from an unprotected fire and the relative effectiveness of various water‐based protection schemes. These results were combined with large‐scale testing, using a representative multilevel process structure, to evaluate the performance of several sprinkler and water spray systems designs common to the industry. Several of these protection systems were shown to be inadequate to reduce the hazard below an acceptable level. However, when designed properly, sprinkler systems were shown to provide acceptable protection of the process structure, though local area water spray was needed for protecting objects near the pool fire surface.

The Skip-resistant Sprinkler Concept — Theoretical Evaluation

This article presents a model for the response time of a sprinkler designed to reduce the skipping phenomenon experienced during large-scale fires. The model guides the design of a cylindrical shield intended to reduce drop impingement from nearby operating sprinklers. Several designs are experimentally tested and shown to reduce likely skipping when compared to the same sprinkler without a shield. The model is validated using a laboratory Plunge Tunnel apparatus to measure the effect of the shield on the thermal sensitivity of the sprinkler and its ability to intercept water drops. This work successfully demonstrates that shielding can decrease the response time of a sprinkler in drop-laden gas flow without causing a substantial increase in response time when exposed to a dry-gas flow. This is the first of two articles on the skip-resistant sprinkler concept. The following article evaluates the performance of the shield in actual fires.

Revisions to FM Global Property Loss Prevention Data Sheet 7-14, Fire Protection for Chemical Plants

For nearly two centuries, businesses around the world have relied on FM Global and its property loss prevention data sheets to reduce risk at their facilities. Data Sheet 7‐14, Fire Protection for Chemical Plants, addresses fire and explosion hazards at chemical manufacturing plants and similar processing facilities, particularly those associated with ignitable liquid, flammable gas, and liquefied flammable gas where a release could result in a fire of long duration. In 2014, FM Global assigned a team of engineers to update the data sheet, which had not undergone a major revision in over 15 years.