In industries that need chillers to operate in dangerous conditions, explosion-proof chillers are the solution. Petrochemical plants and laboratories are a couple of places that use these hard-working, rugged cooling units. But those are not the only industries that benefit from the added safety of an explosion-proof chilling unit. Because explosion-proof chiller manufacturers design these units to specifications based on the environment you install them in, knowing as much as you can about these chillers can aid in determining if one of these units is right for your situation.
What Is an Explosion-Proof Chiller?
Explosion-proof chillers have a reinforced design to protect the chiller’s components from ambient flammable materials that could cause an explosion. No standard chillers available for purchase for commercial use do not qualify as explosion-proof. The company must construct the chiller to adhere to specific regulations to protect against combustion.
Regulations for explosion-proof equipment are outlined by the National Fire Protection Agency, or NFPA, a fire safety group. Electrical requirements fall under the NFPA’s National Electric Code (NEC). This code describes the exact parameters chillers and other electric equipment must meet for installation in hazardous locations that require explosion proofing. The machinery must have sealed wiring to protect the air from stray sparks that could ignite any vapors or flammable gases. Adhering to these guidelines and fulfilling our customers’ needs require us to custom design many of our explosion-proof chillers.
Why Explosion-Proof Chillers Are So Important
To protect the safety of both employees and the facility, reducing the chances of an explosion becomes a prime objective for any business owner. Some worksites are more prone to danger than others. Reducing the risk that a spark from a chiller could ignite explosive or flammable materials is why explosion-proof chillers are a safety requirement for many industries. Though all explosion-proof equipment comes at a premium price, the cost is far below the cost of lost lives from an industrial accident caused by using the wrong machinery.
Aside from being a safety issue, explosion-proof chillers are required by law in many locations that have flammable material in the air. If volatile gases, vapors or aerated liquids are present through the typical use of machinery, the NFPA requires explosion-proof equipment in the area. Failure to comply could result in hefty fines in addition to the danger of igniting flammable materials.
How Does an Explosion-Proof Chiller Work?
With multiple types of explosion-proof chillers available, how each one works depends on the components used. For instance, there are both screw and scroll compressors and air-cooled and water-cooled condensers. The parts of a chiller system don’t make it explosion-proof. The design of the overall system does. But the components determine the final efficiency of the chiller and the temperatures it can reach. Use this information when selecting a chiller for your company.
Most chillers operate in the same way, by cycling refrigerant through the components to transfer heat away from the cooled area (or process fluid) to the outside. Depending on the cooling agent (refrigerant) used and the compressor type, the chillers could drop the temperature of the refrigerant to below zero degrees Fahrenheit. Our selection of chillers has a range of -40 degrees Fahrenheit to 20 degrees Fahrenheit. Ask us if you have any specific requirement for the cooling from your chiller unit.
Refrigerant starts the process in a mixture of a liquid and gas. The gas and liquid move into the evaporator, where heat transforms the refrigerant into a gas with low-pressure. This gas moves into the compressor, which uses one of several methods to compress the gas into a high-pressure state. This gas moves to the condenser, which may use water or air to cool the refrigerant. In the condenser, the coolant gives off its heat and condenses back into a liquid. This liquid is at a high-pressure when it passes through a regulating valve that controls how much of the cooled refrigerant passes into the evaporator to begin the cycle anew.
Types of Explosion-Proof Chillers
You can choose from numerous types of explosion-proof chillers, including:
- Scroll Chillers:Chiller units with scroll compressors have interlocking spirals in the compressors. As the hot, low-pressure refrigerant passes through these, the scrolls raise the pressure of the refrigerant, until it exits in the required high-pressure, heated state.
- Screw Chillers:The compressor in a screw chiller uses one or two screws to press the refrigerant down into a high-pressure state.
- Air-Cooled Chillers: These Air-cooled chillers pass the high-pressure, hot refrigerant through a condenser that blows air over the tubes inside. This air-cooling process is like the way a car radiator removes heat from engine coolant. After the air removes heat from the refrigerant, it passes on to the evaporator.
- Water-Cooled Chillers: Water removes heat from refrigerant in water-cooled condensers. Cold water passes into the condenser, where it absorbs heat from the refrigerant. After heating, it flows out of the condenser, and the cooled refrigerant moves on to the evaporator.
What sets explosion-proof cooling units apart from standard units is the protection of the components. Wires move through sealed conduit and motors have air-tight junction boxes. Seals further prevent flammable gas from entering into the system. By completely sealing the electrical components, chiller construction companies allow these units to be installed even in dangerous places. Some units also feature nitrogen purge systems (where allowed) which positively pressurizes the entire electrical control panel and conduit to prevent any outside air from entering.
Explosion-Proof Chiller Applications
Explosion-proof chillers are not just for use in factories. Cooling units designed for hazardous environments have several applications. Fire safety codes and the NEC will dictate whether your business needs explosion-proof equipment. Some of the companies that often need specially sealed chillers include:
- Refineries: Petrochemical refinement requires extreme caution with all material used. Refineries produce the flammable vapors that require Class 1 explosion-proof chillers. The space the refinery needs the chiller installed in will determine if Division 1 is needed or if Division 2 types will suffice.
- Sample or Process Analyzers: With sample or process analyzers, workers identify the chemical makeup of various substances. Because the contents have unknown compositions and could include dangerous materials, explosion protection in the sample analyzing areas could save lives.
- Granaries: Flour is extremely flammable. Ask anyone who has lived near a grain silo and heard stories about explosions. The fine dust in the air only needs a small spark to set it off. That’s why silos and granaries need explosion-proof equipment. Though article 506 of the NEC creates a separate category for areas with ignitable dust, restrictions on electric equipment remain to prevent combustion.
- Laboratories: Ventilation in labs is critical to the safety and health of the workers. Fire safety and explosion proofing where needed are also important. Anywhere volatile, flammable vapors or gases exist, you need particular electric parts to resist creating stray sparks that could ignite.
- Chemical Plants: Chemical plants may generate or store potentially flammable substances. Even in storage spaces, the facility will need explosion-proof equipment. Ask us about our chemical plant solutions or some of our previous chemical customers, such as Dow Chemical and Texas Petrochemicals.
- Petrochemical Plants: To distinguish a petrochemical plant from a refinery, the former creates substances from petroleum whereas the latter refines crude oil. Both handle hazardous materials. Part of what makes many petrochemicals, such as gasoline, desirable is their flammability. That same trait also puts petrochemical plants at risk of fire. The NEC requires explosion-proof equipment in many places at petrochemical facilities.
- Cooling Flammable Liquids: Flammable liquids often give off hazardous vapors. These vapors make explosion-proof chillers and other equipment in the space required. If the fluids remain sealed, the area would only need Class I, Division 2-approved units. For any space where workers transfer the liquids to another container or have the flammable liquids uncovered at any time, a Class I, Division 1-approved chiller will be required.
- UPS Battery Rooms: In the United States, specific requirements govern the cooling systems used in government buildings. These requirements from the U.S. General Services Administration dictate UPS battery rooms have only explosion-proof fans installed. The fan or cooling system must ventilate to the outside. This protects the backup power system for the building.
- Offshore Oil Rigs: In an offshore environment, the location makes everything more dangerous. Even if space may not require an explosion-proof cooling unit, the location in the middle of the water, far from fire departments, does. Additionally, oil rigs often have exposed oil, which could vaporize to produce a hazardous situation if anything creates a spark. Explosion-proof air conditioners keep the living and working quarters safe and comfortable for the workers on the rig.
This listing does not include all the uses for explosion-proof chillers. Anywhere code requires a specialty, ignition-resistant appliance, you can install an explosion-proof chiller. Check with us to see which NEC classification and division your space falls under so you have an approved chiller for the space.
Explosion-Proof Chiller NEC Classifications
The requirements for explosion-proof chillers depend on the environment in which they are installed. Class I locations are those where flammable vapors could produce an explosion hazard. The NEC further divides Class I into Division 1 and Division 2, based on the location’s proximity to the origin of the vapors. Within each division, the NEC designates groups based on the airborne materials. Section 500.7 of the NEC requires explosion-proof electrical equipment in all Class 1, Division 1 and 2 rooms.
NEC Hazardous Materials Divisions
The NEC divides each Class into Divisions. How close flammable materials or vapors are to the area dictate which division space falls into. Below divisions, groups further subdivide into each NEC Class based on the type of materials in the air and their likelihood of exploding. Chillers must conform to the specific class, division and group they will be used with. These are the two divisions:
- Division 1: According to the NEC, Class I, Division 1 locations are where combustible vapors may be produced with standard operation, during repairs or with faulty operation of equipment. Examples of Division 1 locations include spray painting booths, sites with open vats of volatile liquids and places where flammable compounds are transferred between containers.
- Division 2: Class 1, Division 2 locations pose a slightly lower risk of explosion than Division 1 sites. In Division 2 places, the flammable gases or liquids remain in sealed containers. Positive ventilation to keep volatile compounds in a room also creates a Division 2 site. Lastly, rooms adjacent to Division 1 locations classify as Division 2.
NEC Hazardous Material Groups
The NEC created groups based on the hazardous materials present. Grouped materials have similar clearance requirements between clamped joints and explosion pressures. Equipment rated for explosion-proof must align to the environment to meet these NEC standards:
- Group A: Group A only includes acetylene. Most often, acetylene is combined with oxygen to use as a fuel for welding. Its extreme instability in its natural form makes compounds containing acetylene more commonly used. Some may refer to this hydrocarbon as ethyne.
- Group B: An example of a Group B gas includes hydrogen. This was the gas that was used in the Hindenburg airship that horrifically exploded in New Jersey in 1937. Like other substances in this group, hydrogen has minimum igniting current, MIC, ratio of at most 0.40.
- Group C: Group C combustibles have an MIC ratio between 0.40 and 0.80. One example of this group is ethylene.
- Group D: Propane falls under Group D. Gases and other volatile substances in this group have an MIC ratio greater than 0.80.
- Intrinsically Safe: Intrinsically safe construction typically adheres to Class I Division 1 guidelines. The NEC approves electronics with intrinsically safe designs for use in most hazardous locations.
Per article 500.8(B) of the NEC, all equipment used in a Class I space must not have any surface exceed the ignition temperature of any substances in the room. If you have a Class I, Division 1-approved chiller, you can use it in a Division 2 space. But you cannot use a Class I, Division 2 chiller in Class I, Division 1 space. Look for information about the Class, Division and Group for the chiller, which the company that constructed the chiller should put on the side of the unit. The NEC requires this information to be clearly marked. We create chillers most often used for Class I, Division 1, Division 2, Group B, Group C and Group D.
Installing an Explosion-Proof Chiller
Installers of explosion-proof chillers must always comply with NEC installation requirements, as outlined under article 501. Electrical wires going to the unit must have conduits around them to protect them from sparks. Additionally, where installing the chiller may require flexible coverings, the code puts strict requirements on which coverings are permitted. Additionally, any fittings and boxes must have an approval label for the class and division they are used for. For instance, boxes used in Class I, Division 1 locations must be explosion-proof and explicitly labeled for those zones. In Division 2 areas, the NEC does not require explosion-proof boxes or fittings, however they are strongly recommended by manufacturers.
The NEC puts more restrictions on conduit seals depending on whether you install the chiller in a Division 1 or Division 2 location. Both locations require conduit seals around conduit entering the areas. But the seals used for both must fulfill the requirements of the NEC 501.15. A professional installer will follow these guidelines and others when putting an explosion-proof chiller into a Class I location. Just as using a chiller in the wrong location is dangerous, so is not having it installed to code. Both could cause dangerous situations or incur heavy fines on your business. Make sure you get the right chiller and have it professionally installed in your location.
Deciding on a Chiller
You know you need an explosion-proof chiller, but there are multiple options you will need to choose from. First, you’ll need to know the size of the chiller, though this does not refer to only the dimensions. The cooling capacity requires careful calculations to ensure you don’t waste money or choose an inefficient chiller. Additionally, you’ll need to know which category the chiller room falls into based on NEC specifications. Whoever you purchase from, make sure and do your research. Not all “explosion-proof” chillers are manufactured the same.
Sizing an Explosion-Proof Chiller
Chillers come in a variety of cooling capacities. Ours range from 3 to 600 nominal tons, depending on the type of chiller. To find the correct size of a chiller, you need to know the temperature decrease you need and the flow rate. The fluid temperature going into the chiller minus the chilled fluid temperature, measured in Fahrenheit, is the temperature decrease needed. For instance, if water/fluid starts at 72 degrees Fahrenheit, and you need a temperature of 50 degrees Fahrenheit. The temperature decrease would be 72 – 50 = 22.
Next, use the flow rate in gallons per minute and multiply it by 60 to find the number of gallons per hour. Take the gallons per hour and multiply it by 8.33 (converts GPH to LB/HR) and by the temperature decrease. This calculation will give you the BTUs per hour. For example, if your system has a flow rate of 40 gallons per minute, then the calculation would be 40 x 60 x 8.33 x 22 = 439,824 BTU per hour. NOTE: This 8.33 conversion factor only works for water. For other fluids, please contact the engineering team at Smart Family.
Using the BTUs per hour, divide the number by 12,000 to find the minimum tonnage you need. In the example, that would be 439,824 ÷ 12,000 = 36.652 tons.
Because this is a minimum, oversize it by 20 percent to account for future growth (and loss of efficiency from fouling), as recommended by industry publication Chiller & Cooling Best Practices. Multiply the tonnage by 1.2 to find the ideal size, including the 20 percent increase. For the example, that would be 36.652 x 1.2 = 43.9824 tons. A 45-ton unit would suffice for this example.
Ideally, you don’t want to select a chiller that is too small. Your system will constantly work and never shut off to attain a temperature it cannot reach. This overtaxes the system, shortening its life and increasing the need for repairs. Conversely, don’t oversize a unit too much. If you purchase a unit that is too large for your needs, you may have trouble fitting it into your space and pay too much for cooling you’ll never use. Size becomes an especially critical issue with explosion-proof chillers, which we often custom build. Know your ideal cooling capacity when ordering to make the process faster.
NEC Classification and Selecting a Chiller
To choose the right explosion-proof chiller for your situation, you will also need to know the NEC classification for your chiller in addition to the tonnage requirements. Learn the requirements for Class I, Division 1 and Division 2 environments. If you have doubts, consider intrinsically safe equipment or ask a cooling professional. Generally, if you have flammable materials with access to the same air the chiller uses, you have a Division 1 situation. If you place the chiller in a nearby room or if you keep the flammable gases sealed, the space is Division 2.
Find Out More About Explosion-Proof and Other Industrial Chillers
If you’d like a chiller installed, contact us at Smart Family of Cooling Products. We’ve been in the cooling business since 1991. Today, our catalog includes units from one to 1,500 tons in both standard and custom designs. Our customers include well-known companies such as Dow Chemical, Exxon, GE, Goodyear, Chevron, Shell, Nabisco, BP, Lockheed Martin and many others. If we have a chiller in stock, we can deliver it within 24 to 48 hours. But many of our clients require custom-built explosion-proof chillers. Our experienced staff can construct those to the needs of your company as well. We have a long history of satisfying the needs of businesses both large and small. Let us provide the explosion-proof chiller your business requires.