Volume 1 Number 3 - June 1999 - Will Your Pump Blow Up My Building?
Will Your Pump Blow Up My Building?
A: Maybe...
Perhaps the most common question we are asked about submersible pumps is if, for a particular application, it has to be "explosion proof". Our first response is that it is up to "the local authority having jurisdiction" (which is not a very helpful answer if you have to have your plans completed and submitted to Plan Check that afternoon).
The National Electrical Code (NEC) divides hazardous locations into several classifications based on the potential for explosion and fire due to the presence of flammable gasses, vapors, or finely pulverized dusts. Class I, Division 1 locations, for instance, are defined as areas that contain materials that will ignite under certain operating conditions (such as leakage or equipment failure). These materials are further classified by their ignition temperatures into Groups. Thus, a particular location may be designated (by the local authority having jurisdiction) as a Class I, Division 1, Group C hazardous location.
Q: Well, what does _____City usually require? And who is the local authority having jurisdiction for _______ City?
A: Usually the electrical division of a city or county Building and Safety department or the fire department will determine an areas classification. NOTE: Testing agencies such as UL and FM do NOT classify areas.
Q: Are certain areas always designated as hazardous locations?
A: No.
For example, many authorities throughout the country designate sewage wet wells as Class I, Division 1 locations due to the presence of methane gas in raw sewage. However, the City of Los Angeles is not one of them. Few jurisdictions classify sumps receiving water from emergency drains in parking structures as hazardous locations. The City of the Angels does. The possibility of an accidental spill of gasoline from a ruptured gas tank or siphoning attempt would seem to fit the definition of a Class I, Division 2 location, which is an area in which hazardous material is normally confined within closed containers or closed systems, and can only escape in the event of an mishap*. However, L.A. City argues that the gasoline vapors in a parking structure, which are heavier than air, will migrate into the low areas of the structure, and end up in the sump. So, to answer your question, there is little agreement as to whether an area is even hazardous, let alone Division 1 or 2.
Q: Now that the State of California is requiring drains in elevator shafts, many local authorities are in a quandary as to whether to classify that area as hazardous due to the potential of an hydraulic fluid leak.
A: A quick check of the data published by manufacturers of hydraulic oil does not give a definitive answer as to whether it is ignitable under circumstances that the NEC spells out (frequent "leakage" due to repairs, maintenance, faulty operation or breakdown of equipment comes under the Division 1 definition). On one hand, quoting Chevron Oil’s product description:
Special Note: Chevron Hydraulic Oils AW should not be used in high pressure systems in areas subject to fire hazard. Leaks or ruptures in high pressure systems using materials of this type can constitute a fire hazard when they are in the vicinity of ignition sources such as an open flame, pilot lights, sparks, or electric arcs.
They caution "DO NOT weld, heat or drill container. Residue may ignite with explosive violence if heated sufficiently."
On the other hand, they state the flash point (lowest temperature that the material must be heated for its vapors to ignite) is 399 deg.(F) (hardly likely to be encountered in an elevator shaft). Chevron’s Material Safety Data Sheet (MSDS) lists the NFPA Flammability Rating as 1 (4 is the highest), and the Department of Transportation (DOT) Hazard Class as "non-applicable".
So, do we have to worry about a pump igniting hydraulic fluid? The elevator code is only concerned with draining water out of the hoistway. Unfortunately, the pump control system cannot distinguish between water and oil - it will attempt to pump out whatever fills the sump (see What’s New #2).
Now consider the UL surface temperature requirements for explosion proof motors. They define the maximum frame temperature allowable "...under any condition of overload, under voltage, single phasing, etc. up to and including burnout" (emphasis added). In the case of Class I, Group D motors, the maximum allowable frame temperature is 280 deg. (C), 536 deg. (F). The NEC requires that "abnormal load conditions" be considered when evaluating explosion proof motors for Division 1 locations. Uh-oh.
Q: So let’s say I’m the cautious type, and figure that my application can get raw sewage, gasoline and even hydraulic oil. What type of equipment should I specify?
A: This answer is much easier!
Referring back to the NEC, "Class I equipment shall not have any exposed surface that operates at a temperature in excess of the ignition temperature of the specific gas or vapor". Further, equipment approved for Class I, Division 1 locations must be capable of withstanding an internal explosion without igniting the surrounding atmosphere. Gasses released from the enclosure must be cooled below the Group temperature classification. To comply with the NEC you MUST install "approved" equipment, appropriately marked and identified. Both Underwriters Laboratories and Factory Mutual Research Corp. list or approve electrical equipment suitable for Class I locations. We won’t get in to the UL versus FM requirements or standards, or whether one is more stringent than the other (feel free to request our opinion).
Explosion proof motors are only half the issue. All electrical equipment in the hazardous area must be incapable of causing ignition. Apparatus not listed as explosion proof is required to be intrinsically safe, "in which any spark or thermal effect produced either normally or in specified fault conditions is...incapable of causing ignition..." (see NFPA 493). Further, wiring of intrinsically safe circuits MUST BE PHYSICALLY SEPARATED FROM WIRING OF ALL (NON-INTRINSICALLY SAFE) CIRCUITS. This is not only a code requirement, but a practical one as well. Many intrinsically safe components are sensitive to high voltage circuits that can cause potentially damaging inductive currents. Always run high voltage wiring in a separate conduits.
Q: Are there any special requirements for control panels serving explosion proof pumps?
A: A standard UL508 listed control panel can automatically operate the pumps with a variety of liquid level controls. However, once it is established that the pumps and level controls are serving a Class I, Division 1 location certain features must be added. The panel enclosure must be rated NEMA 7 if it is also located in a hazardous area. Otherwise, it may be rated for the environment in which it will be installed e.g. NEMA 1 or 2 (indoor), NEMA 3 or 4 (outdoor), etc. Certain explosion proof motors require circuitry for moisture sensor or seal failure probes. Most also require connections for thermal sensors, imbedded in the motor windings, to shut down the motor in the event of overheating. Be sure to check with the pump manufacturer or representative.
Intrinsically safe circuits must conform to ANSI/UL 913 standards. Per the NEC (504-4): All intrinsically safe apparatus and associated apparatus shall be approved (emphasis added). If the control panel manufacturer does not have a UL913 approval (and cannot label his panels UL913) the specifier, installer and owner may have some exposure in the event of an event. Buyer beware.
Please take a look at some of the "links" we have on our web site to the various code authorities and organizations that deal with the issues we have attempted to address here. Your local pump salesman is not the final authority on these matters - the local building authority is the one to punch your ticket. But we’re always happy to help - use our online request form or call: 1-800-74PUMPS for a prompt reply.
*The code allows the use of general purpose equipment (not explosion proof) in a few specific Division 2 locations as long as the equipment will not cause ignition under normal operating conditions. A common example is an open dripproof three phase motor will be permitted in certain Division 2 areas, but not a single phase motor (due to "brushes, switching mechanisms, or similar arc-producing devices").
The Confidence You Can SpecifyK