ACKNOWLEDGEMENT. IIAR expresses its deepest appreciation to these authors for their contributions for the betterment of the industry.

Transcription

1 t ACKNOWLEDGEMENT The success of the 15th Annual Meeting of the International Institute of Ammonia Refrigeration is due to the work of the authors whose technical papers appear in this book. IIAR expresses its deepest appreciation to these authors for their contributions for the betterment of the industry. --IIAR Board NOTICE The views expressed in the papers contained in this book are those of the individual authors. They do not constitute the official views of IIAR and are not endorsed by it Connecticut Avenue, N.W. Suite #700 Washington, D. C / FAX: 202/

2 ARTICLE 80 OF THE UNIFORM FIRE CODE: COMPLIANCE CASE STUDY FOR AMMONIA REFRIGERATION SYSTEMS By : Ellis Norton The Facility Group Atlanta, Georgia Presented at: IIAR 15th Annual Meeting March 21-24, 1993 Vancouver, British Columbia, Canada

3 - I. INTRODUCTION The hiform Fire Code (UFC) was initially deve,aped by the California Fire Chiefs Association and was first published by the Western Fire Chiefs Association (WFCA) and the International Conference of Building Officials (ICBO) in The Code is revised at 3-year intervals, and is currently sponsored by the International Fire Code Institute (IFCI). This code has been adopted in California and in most of the states west of the Mississippi River. Generally, the Uniform Building Code (UBC) and the Uniform Mechanical Code (UMC) are used in conjunction with the UFC. The 1988 revision of the UFC incorporated a complete re-write of Article 80, Hazardous Materials. Because ammonia is covered by the definition of hazardous materials in the UFC, ammonia refrigeration systems are subject to Article 80. Ammonia is considered by some fire officials as both a "toxic compressed gas" and a "corrosive" under Article 80. The author does not agree that ammonia refrigeration systems should be included in Article 80 which is a view shared by many in our industry. Ammonia refrigeration systems should be included in Article 63 of the UFC, under Mechanical Refrigeration. Article 63 needs to be revised to include appropriate requirements from ASHRAE and IIAR standards, and Article 80 should refer to Article 63 for coverage of refrigeration systems. IIAR has made significant progress towards instituting these changes. Until these changes are actually accomplished, and Ellis Norton is the Refrigeration Design Manager of The Facility Group in Smyrna, Georgia. 71

4 ammonia refrigeration systems are remosved from Article 80, we must comply with its requirements. This paper is offered as a guideline to help the members of our industry comply with the requirements of Article GENERAL DESIGN REQUIREMENTS Experience with Article 80 on recent projects has been that the following sections of the UFC are usually required by fire code officials and emphasized for ammonia refrigeration systems: Sec , General Storage Requirements - Division 111 Sec , Compressed Gases Sec , Corrosives Sec , General Dispensing, Use and Handling - Division IV Sec , Dispensing and Use Compliance with these sections impacts the refrigeration system design, and requires that we look at our system from a different standpoint than we have in the past. Some major design issues to consider are: 0 Minimize the refrigerant charge 0 Utilize the evaporative condenser as a scrubber for the engine room ventilation 0 Eliminate fugitive emissions from relief valves, control valves, and hand valves 0 Utilize the ammonia dilution tank (required by Article 63) to dilute ammonia concentration in the condenser pan Develop calculations that predict ammonia discharge (ppm) from the compressor room ventilatiodscrubber system In addition to refrigeration system design, the building design is also impacted. Generally, the owner will have a more expensive building as a result of Article 80. Some of the major building design issues to consider are: 0 0 A sprinkler system is required in the engine room A special occupancy rating is required in locations where ammonia is stored: fire walls are required and explosion venting may be required 72

5 0 0 0 Secondary containment requirements dictate special floor design and treatment in the engine room Electrical emergency power (generator or other source) is required for the scrubber, ventilation, control and alarm systems Smoke detectors are required in the compressor room In working with various fire departments in California, we have found that a similar attitude exists among most individuals, and they take similar approach to Article 80 enforcement. The typical attitudes encountered are: 0 Code enforcement personnel are concerned with the external impact of ammonia releases. What happens to the community as a result of a release is more important to them than the safety and protection of people inside. Generally, 0 OSHA is responsible for the safety of the workers inside the facility Code enforcement officials in general do not understand ammonia refrigeration systems, and they have no understanding of how compliance with the code impacts design, performance and safety 0 Interpretation of the code is not consistent, even among personnel in the same fire department. The reason being that no one has a back log of experience. 0 Department personnel in general do not (can not) offer suggestions on compliance. Their attitude is to wait for a submittal and then make a ruling on a specific submittal. In general, there is considerable turn-over of personnel within the code, and this creates problems due to inconsistent code interpretation. It is best to work with the same individual throughout a project so that this problem is minimized. Our projects were grocery distribution centers having ammonia refrigeration systems that contained approximately 10,000 lbs. of ammonia. The configuration for each system is a central machinery room containing the compressors, vessels, refrigerant pumps, and electrical equipment. One or more evaporative condensers are located on the roof above the compressor room. Piping and control valves are on the roof. A brine chiller located in the machinery room provides refrigeration for banana rooms in some instances. A computer control system was 73

6 installed in each case. The contractors who installed the system were local in each case, and in general they were familiar with Article 80, but in no case did they know exactly how to comply with all the provisions. The methods used to comply with Article 80 are not the only way that this can be done. There are better ways in many cases than these methods. However, the methods described have been approved by various jurisdictions, and the comments and descriptions are offered as a starting point for a system design STORAGE REOUIREMENTS-GENERAL (80.301) The General provision for storage requirements in Section must be adhered to if there is not a specific requirement in other (following) sections. Specific areas of interest are: 0 Spill Control, Drainage, and Containment (1). This is also required under Section , Corrosives, and the requirements will be discussed under that section. Ventilation (m). This is also required under Section (a)(6), and the requirements will be discussed in that section. Fire-extinguishing Systems (p). The machinery room must be protected by an automatic sprinkler system with a basis of design as Ordinary Hazard Group 3 under the UBC. Acceptable specifications for the system are described below: Type: Density : Remote area: Head Type: Head Spacing: Wet, Schedule 40 pipe.20 gpin per sq. ft. 3,000 sq. ft. Brass Upright; 17/32" orifice; 286 F 130 sq.ft. A sprinkler system in the machinery room presents some problems. Some things that 74

7 must be considered are: Protection of electrical equipment, such as the control panel and the motor control center. Accidental release during operation: water will be released at a rate of 1" every 3 minutes. 0 Explosion Venting or Suppression, (4). Explosion venting is u t required under Article 80. Insurance carriers have requested, however, this on some projects, with an assumption that ammonia is a flammable gas. These requests should be firmly resisted on the grounds that ammonia is not classified as flammable by DOT, and venting is not required by the code. 0 Standby Power, (s). Standby power is defined as "Legally Required Standby Systems" in the National Electric Code (NEC). It differs from "Emergency Power" as specified in Section (a)(7) of the UFC. The major difference between the two is that emergency power systems are essential for safety to human life, whereas standby systems are intended to provide power for fire fighting, rescue operations, control of health hazards, and similar operations. Both require an automatic transfer switch, but the emergency system must come on in 10 seconds, whereas the standby system must come on within 60 seconds. Generally, unless the express approval of the fire marshal1 is obtained, an emergency power system is required under Article 80 for operating the following equipment: 1. Machinery room ventilation fan 2. Ventilation air scrubber system 3. Ammonia detector 4. Emergency alarm system Emergency power can come from one of three sources: 75

8 1. Generator Set. Generator service, and as stated above, switch that operates within 10 be provided. system. The generator must have automatic start upon failure of normal it must be equipped with an automatic transfer seconds. Normally, a two-hour fuel supply must must be supplied with a self-contained cooling 2. Separate Service. This requires a completely separate supply, widely separated electrically and physically, and requires a separate transformer, in most instances. Most utilities will resist supplying this service, and will cite code requirements as a reason. However, the National Electric Code (NEC) allows this as an exception in the case of emergency power for legally required standby. It is best to get started on this service early, and to get the client active in discussions with the local utility. 3. Connection Ahead of Service Disconnecting Means. This connection cannot be within the confines of the main disconnect. In order to make the connection, main power must be shut off by the utility and the connection made at a location far enough away from the main so that any occurrence inside the building will not interrupt the emergency service. Source (3) is normally the most economical option for emergency power, and as above, it is best to get started on this service early and to get the client involved in discussions with the utility. - IV. COMPRESSED GASES (80.303) Section , covering compressed gases, is normally applied to ammonia, and is the main section governing ammonia refrigeration systems especially when fire officials consider ammonia to be a "toxic compressed gas." Important areas are: 0 Exempt Amounts, (a)(2) This section requires that any amount of ammonia (stored) in excess of 40 cubic feet at normal temperature and pressure (approximately 2 lbs.) be in a room conforming to H-7 occupancy under the Uniform Building Code (UBC). This requires a 4-hour rated fire wall between the machinery room and the rest of the plant in most instances. 76

9 0 Exhaust Ventilation, (a)(6). The exhaust ventilation system must be capable of absorbing or scrubbing ammonia vapors from the ventilation air in the event of a spill. Discharge from the scrubber must. be less than one-half the IDLH (Immediately Dangerous to Life and Health) value, or 250 ppm for ammonia. In all instances the evaporative condenser served as the scrubber. Calculations had to be submitted to show both the maximum release rate and the expected scrubber discharge in ammonia ppm. The exhaust fan must be sized in accordance with the Uniform Mechanical Code (UMC) for 12 air changes per hour (minimum). The exhaust air must be ducted to the condenser inlet so that it is captured by the entering air. The condenser drain must also be diverted automatically to a holding tank when the concentration of ammonia gets to a pre-determined level. At the same time, the drain pan must be diluted with fresh water on a rise in concentration. The water dilution tank (required by Article 63) can be used to collect the diverted drain water. Dilution water is furnished from the dilution tank or from water make-up. Controls must be such that an ammonia detector in the machinery room compels the exhaust fan and condenser fans and pumps to run, and a ph sensor in the condenser pan initiates the drain diverting and pan water dilution cycle. 0 Gas Detection, (a)(9). Although it is standard practice to provide ammonia detectors in the machinery room as a minimum, and in refrigerated rooms in most instances, Exception (2) in this section states that, "if the physiological warning properties for the gas are below the accepted 77

10 permissible exposure limit," for that gas, "a continuous gas detection system need not be provided." As we all know, ammonia, known as the self-alarming refrigerant, fits this requirement. However, a detector is required in the machinery room for the operation of the ventilation fan to qualify as a non-hazardous location under the National Electric Code (NEC). In one instance, detectors were required at each air unit to satisfy a B-2 occupancy requirement for the building under the UBC. Smoke Detection, (a)(10). A smoke detector is required in the machinery room, and it must be tied into a local alarm. - V. CORROSIVES, Section , covering corrosives, requires secondary containment for certain areas. The important part of this section is section (a)@), Containment, which states: I' Secondary containment shall be provided for the storage of corrosive liquids in accordance with the requirements of Section (1)(4). This requires secondary containment for the vessels in the machinery room. The machinery room floor can either be recessed or containment curbs can be constructed around the vessels to provide secondary containment. In either case, provisions must be made to seal the floor or curbs to make the containment liquid-tight. No drains are permitted unless they extend up far enough to stay clear of 20 minutes of fire sprinkler water plus the volume of the largest vessel. Provisions must be made to dispose of the ammoniawater solution. A sump pump can be used to transfer it to either the water dilution tank or to other approved areas. 78

11 - VI. DISPENSING, USE AND HANDLING-GENERAL (80.401) Section covers the General requirements for dispensing, use and handling. The section requires excess flow valves in pipes carrying ammonia liquid or gas at pressures over 15 psig. This is an area of serious concern because excess flow valves large enough to meet the requirements in this section are not available through traditional suppliers. Even if these valves could be located, the pressure drops are prohibitive in some instances. For these reasons, we must provide "alternative means and methods" to accomplish the intent of this section. One alternative that has been accepted is the installation of emergency solenoid valves in the main liquid supply and hot gas line(s), with controls to close automatically when ammonia is detected at valve groups or air units. The fact that solenoid valves close on power failure contributed to the acceptance of this alternative. This section also requires seismic protection. The details and guidelines found in the SMACNA publication, Seismic Restraint Manual: Guidelines for Mechanical Systems can be used for most piping supports. However, a review of vessel and machinery foundations must be made by a qualified structural engineer. VTI. DISPENSING AND USE (80.402) Section cwers dispensing and use, and requires secondary containment for roof-top piping. Because the Risk Management and Prevention Program (RMPP), required by the State of California, showed that a worst case release did not constitute a serious threat to life or safety at the nearest sensitive receptor, secondary containment was required only for valve groups, not 79

12 for the entire rooftop piping system. One arrangement that was approved is containment "boxes" that enclose the valve groups. The boxes are connected in series with 12" round duct, and air is continuously drawn through the system by a fan discharging into the condenser air inlet. An ammonia detector is mounted in this duct. The detector activates an alarm and initiates procedures such as closing solenoid valves. It also initiates the scrubber cycle in the condenser. An RMPP report is required on every large refrigeration project in California. In most instances it will show that ammonia releases do not constitute a serious hazard. It is to our advantage to have this report done early and to use the results in discussions with code officials. VIII. CONCLUSION IIAR and other refrigeration industy groups are working with ICBO and IFCI to remove ammonia refrigeration systems from Article 80. This will not happen immediately, however, and in the meantime we must comply. The methods presented in this discussion are designed to meet the requirements in Article 80 with a minimum impact on refrigeration system safety operation and cost. 80