OCEAN CITY, MD — New publications are very rarely considered sexy enough to be considered for a full-length article. This time, however, we need to make an exception.
In refrigeration systems, “Piping drives many problems.” That’s why the International Institute of Ammonia Refrigeration (IIAR) has published the Ammonia Refrigeration Piping Handbook, combining earlier published data with substantial input from contractor experts.
“Real expertise of piping lies with the contractor,” said co-author M. Kent Anderson. “A good refrigeration contractor knows piping well. Many things that go wrong with refrigeration systems can be traced back to the piping.”
The Ammonia Refrigeration Piping Handbook, introduced at the Refrigerating Engineers and Technicians Association’s (RETA’s) 91st-annual conference here, has close to 400 pages, 190-plus diagrams and drawings, 50-plus charts and tables, and 30-plus formulas (pressure drop, temperature drop, capacity, and more).
Coauthored by Anderson and Lane Bonebrake, it has been seven years in the making and contains a lifetime of refrigeration experience compiled from refrigeration contractors, sections of the ASHRAE Handbook and Standard 15, a long-used Vilter piping manual, and other sources. The Vilter manual is about 20 years old, the authors said. The ASHRAE Handbook has some piping information but not much, especially not for ammonia.
First of Its Kind
Up until now, there has been no comprehensive piping document, the authors said.
The resulting IIAR publication goes well beyond those source materials, especially in its use of contractor knowledge from the field, which is supported and enhanced by existing technological references; “taking what was published out there, and matching it up with real-world practices,” Anderson said.
The book includes:Pipe sizing;Pipe installation procedures;Evaporator and condenser piping, and components that include many valves and controls;Equipment room piping;Piping for pressure relief devices (sizing devices themselves and discharge lines, hydrostatic relief protection);Insulation for refrigeration systems;Welding procedures; andCodes and standards.
The depth of information in one location has made this one of the most exciting new publications in the refrigeration industry in years, evidenced by the interest of RETA member technicians attending the session on the publication.
One of the book’s more controversial sections may be the one on pipe sizing.
According to Anderson and Bonebrake, the new piping book’s development ran into some discord when the subject of pipe sizing was being tackled. In general, the publication leans toward larger pipe sizes than some refrigeration contractors may have been recommending for their customers.
“You can cram any tonnage in any size pipe,” commented Anderson. “The option is in between” piping that’s oversized and piping that is undersized, but which has a lower first cost.
The pipe sizing section includes:
Two methods for estimating pressure loss: the economic sizing method, which the association recommends, and the conventional method based on pressure and temperature drop.
According to Bonebrake and Anderson, the operating costs in the economic sizing method are controversial because this offers a basis of comparison: “Why is smaller pipe in my facility?” However, “As an industry, we need to look for an optimum performing plant. It’s a more expensive first cost on piping, but more value over the long run,” said Anderson.
Capacity tables “not found anywhere else,” Anderson said; all tables are extended up to 24-ft sizes.
Valve selection information;
Liquid and vapor flow formulas; and
A pocket-sized book with sizing information could be in the works, Bonebrake and Anderson said. “It’s taken seven to eight years to give birth to this publication,” said Anderson. “It will get updates. It will be a living document.”
For information on obtaining the book, contact IIAR at 1110 North Glebe Road, Suite 250, Arlington, VA 22201; 703-312-4200; 703-312-0065 (fax); email@example.com (e-mail); www.iiar.org (website).
Sidebar: Evaporator, Condenser Piping The evaporator section contains detailed piping recommendations for the installation of air-cooling units and liquid chillers; special-purpose evaporators; and piping and valve details (how it should be piped and valved to get the best performance).
The section also covers thermal expansion in liquid lock-up, and hydraulic shock, during which valves and headers can be fractured, pipes rupture, and more problems occur from the introduction of hot gas into a cold coil. The book describes how to deal with it, as well as the characteristics of flow.
“If pipes are clanging and banging, it isn’t working properly,” commented Anderson.
Also included is trapping and how to equalize flow between condensers.
Sidebar: Piping for Pressure Relief Devices
This section includes:
Vapor relief device sizing (including changes from ASHRAE Standard 15 committee and IIAR on dual relief valves and three-way manifold);
Discharge line sizing:
— Single relief valve;
— Combined flow for valves at different setpoints;
— Combined lines for nonsimultaneous releases;
— Simultaneous releases;
— Diameter of discharge lines; and
— Common line for two or more relief valves.
In short, this work contains “quite a lot of good information that isn’t found anywhere else.”
Discharging relief valves into the low side; this is increasingly common.
Replacement in kind;
Use of rupture discs with relief valves;
Vent lines for relief valves on compressors;
— ASME liquid relief valves;
— Hydrostatic relief valves;
— Liquid relief regulators; and
Dispersion to the atmosphere and water (alternative methods to determine discharge lines).
Refrigeration System Insulation
This section goes beyond “just thickness; it addresses how to get a good vapor barrier.” Topics include:
Fundamentals of insulation;
Insulation physical properties;
Effect of moisture on the insulation value to prevent condensation between insulation and pipe;
Insulation material selection;
Insulation system components;
Recommended practice for insulation applications;
Insulation installation guidelines; and
Insulation of vessels.
Welding Procedures ANSI welding codes and standards;
Jurisdictional acceptance of standards;
Definitions of terms;
Specifications for welding ammonia piping; and
Samples from contractors, including the welding procedure specification (WPS) and procedure qualification record (PQR).
Codes and Standards Pressure vessels;
Refrigeration safety code (ASHRAE Standard 15);
International Mechanical Code; and
Titles and sources (codes, standards, and guidelines).
Equipment Room Piping
This section includes:
Suction and discharge piping (how to pitch, trap if needed);
Oil pot piping;
Interstage cooling (gas and liquid); and
Manual emergency discharge (“fireman’s dump” systems).
Publication date: 11/13/2000