Tuesday, January 26, 2016

Valve Preparation For Oxygen or High Purity Service

Hazmat symbol for oxygen
Oxygen is used extensively throughout a wide range of industrial processes. Medical, deep-sea, metal cutting, welding, and metal hardening are a few examples. The steel industry uses oxygen to increase capacity and efficiency in furnaces. As a synthesis gas, oxygen is also used in the production of gasoline, methanol and ammonia.

Odorless and colorless, oxygen is concentrated in atmospheric air at approximately 21%. While O2, by itself, is non-flammable, it vigorously supports  combustion of other materials. Allowing oils or greases to contact high concentrations of oxygen can result in ignition and possibly explosion. Oxygen service preparation of an industrial valve calls for special cleaning processes or steps that remove all traces of oils and other contaminants from the valve to prepare for safe use with oxygen (O2). Aside from the reactive concerns surrounding oxygen, O2 preparation is also used for applications where high purity must be maintained and valves must be free of contaminants.

Gaseous oxygen is noncorrosive and may be used with a variety of metals. Stainless steel, bronze and brass are common. Liquid oxygen presents unique challenges due to cryogenic temperatures. In this case, valve bodies, stems, seals and packing must be carefully chosen.

Various types of valves are available for oxygen service, along with a wide array of connections, including screwed, socket weld, ANSI Class 150 and ANSI Class 300, DIN PN16 and DIN PN40 flanged ends. Body materials include 316 stainless steel, monel, bronze and brass. Ball and stem material is often 316 stainless steel or brass. PTFE or glass filled PTFE are inert in oxygen, serving as a common seat and seal material employed for O2 service.

Common procedures for O2 service are to carefully deburr metal parts, then meticulously clean to remove all traces of oil, grease and hydrocarbons before assembly. Valve assembly is performed in a clean area using special gloves to assure no grease or dust contaminates the valve. Lubricants compatible with oxygen must be used. Seating and leakage pressure tests are conducted in the clean area, using grease free nitrogen. Specially cleaned tools are used throughout the process. Once assembled, the valves are tested and left in the open position. A silicone desiccant pack is usually inserted in the open valve port, then the valve ports are capped. A warning label about the desiccant pack's location is included, with a second tag indicating the valve has been specially prepared for oxygen service. Finally, valves are individually sealed in polyethylene bags for shipment and storage. Different manufacturers may follow slightly differing protocols, but the basics are the same. The valve must be delivered scrupulously contaminant free.

The O2 preparation of valves is one of many special production variants available to accommodate your special application requirements. Share your valve requirements and challenges with a valve specialist to get the best solution recommendations.

Tuesday, January 19, 2016

Delta Cooling Towers - News Update

AHR Expo announcement for Delta Cooling Towers
Delta Cooling Towers
Exhibiting at AHR Expo 2016
Delta Cooling Towers manufactures corrosion resistant cooling towers for commercial and industrial applications where these product features are important:
  • Seamless double wall engineered plastic (HDPE) shell
  • Corrosion proof construction
  • Direct drive fan system
  • Totally enclosed VFD rated motors
  • Factory assembled for simple installation
  • 20 Year shell warranty
  • PVC water distribution system with non-clog large orifice removable nozzles
  • High efficiency PVC fill
  • Made in the USA
Mountain States Engineering and Controls (MSEC) represents the manufacturer in Colorado, Wyoming, and Montana You can visit the Delta Cooling Towers booth at AHR Expo January 25 - 27 in Orlando, Florida. 

Corrosion resistant cooling tower for HVAC or industrial cooling
HDPE Cooling Tower
Courtesy Delta Cooling Towers

Tuesday, January 12, 2016

Replacing Finned Tube Heat Exchangers...When There Is No Documentation

Refrigeration finned evaporator coil
Refrigeration evaporator coil, one of  many finned coil
and heat exchanger types
Heat is a common energy component of many industrial processes. Moving or transferring heat between two media is accomplished with a wide variety of heat exchangers, which are manufactured in forms to accommodate the specific performance requirements of each process, machine, or operation.

One type of heat exchanger is the finned tube, also called finned coil. It is commonly used when heating or cooling air, with the fins expanding the heat transfer surface of the tube for greater efficiency. Typical applications include:

  • Steam to air
  • Water to air
  • Refrigerant to air

Eventually, all heat exchangers need either major overhaul or replacement. The general practice with finned coils is to replace them. There are many circumstances that could lead to the unfortunate loss of the original design and construction information for the coil to be replaced. If faced with this dilemma, here are some of the information points you will need to have a replacement fabricated.
  • Mounting Form: How is the coil held in place within the equipment or process? Record locations and size of any mounting holes or other fixtures holding the assembly in place. If there is a frame or case for the coil, measurements and a sketch or drawing of the case will be helpful. 
  • Construction Materials: Make a schedule of all the parts of the existing assembly and the material from which each is fabricated.
  • Tubes: The outside diameter and wall thickness of the tube used in the assembly is important.
  • Media: What flows inside the tubes? What flows outside the tubes?
  • Inlet and Outlet Conditions: This is critical data that, if not already documented, will need to be determined in order to assure proper performance. The inlet and outlet (also referred to as "entering" and "leaving") conditions for both media define coil performance.
  • Connections: Size, type, and location of any media connections must be coordinated with existing conditions to make the new coil a true drop-in replacement.
  • Circuiting: Circuiting refers to the path, or paths, the media contained within the tubes will follow. This can be difficult to communicate in some cases, as the circuiting in some finned coils can be complex. Take the time to make a drawing of both ends of the existing coil, detailing the connections made by the U-shaped tubes or headers on each end. Additionally, if there are capillary or small branching tubes that extend from the main inlet connection to several circuits, detail those too. Take photos as part of your documentation.
  • Purpose and Application: Write out a description of what the heat exchanger is supposed to accomplish. Include as much detail as you know about the process media. This will be useful to the engineer attempting to process all the information you provide into a properly configured heat exchanger.
The replacing of a heat exchanger is also a good time to examine the performance delivered by the existing unit. Was it a limiting factor in the operation of the process? If so, perhaps this may be an opportunity to build in some headroom. Whatever the case, recognize that bringing in a product specialist with experience and knowledge will provide the beneficial leverage you need to get the job done right and finished on time.

Tuesday, January 5, 2016

Pressure Relief Valves - Safety Sentry

Gas fired industrial steam boilers
Industrial processes involve hazards. Thoughtful engineering
and design minimize risk and mitigate damage.
Danger and hazards are an integral part of industrial processes. The mitigation of these dangers and hazards, as well as reducing the probability of their occurrence, is the primary charge of industrial process engineering. Every product intended for use in a process control setting has safety and protection included in its design criteria. Pressure relief valves fall in that category of products designed and intended solely for safety purposes.

Manufacturers of what most generally refer to as pressure relief valves break the genre down into two distinct groups, relief valves and safety valves. One manufacturer, Kunkle (a Pentair brand), distinguishes the two valve types in their "Safety and Relief Products Technical Reference"...
Relief Valve: A spring-loaded pressure relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. A relief valve is used primarily with incompressible fluids (liquids).
Safety Valve: A spring-loaded pressure relief valve actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used with compressible fluids.
The difference between the two valve types is found in their response to an excessive pressure condition. The relief valve, according to the definition, responds proportionally to the pressure increase, whereas the safety valve provides a non-proportional rapid response. Note also that the relief valve is generally intended for use with liquids (incompressible) and safety valves are commonly applied to compressible fluids, which would include steam and air.

Pressure relief valves are found anywhere pressure is contained, be it a piping system, vessel, even a
Pressure relief valve spring loaded
Spring loaded pressure
relief valve
Courtesy Kunkle
household pressure cooker. The purpose of the relief or safety valve is to protect a pressurized system or vessel, should the system pressure exceed the maximum allowable working pressure. Simply put, keep it from breaking apart.

Because of the potentially catastrophic nature of a pressurized system failure, there is a high level of scrutiny, regulation, and testing focused on pressure relief and safety valves. The proper sizing and selection of the valves is also critical to providing proper function.

I have included a technical reference bulletin from Kunkle with this article. Browse through it. You are bound to discover something you did not know about safety and relief valves and their proper application. You can also contact the specialists at Mountain States Engineering for assistance in proper valve sizing and selection.