For field testing you may use various types of auxiliary equipment to attach PEMS to a vehicle or engine and to power PEMS.
(a) When you use PEMS, you may route engine intake air or exhaust through a flow meter. Route the engine intake air or exhaust as follows:
(1) Flexible connections. Use short flexible connectors where necessary.
(i) You may use flexible connectors to enlarge or reduce the pipe diameters to match that of your test equipment.
(ii) We recommend that you use flexible connectors that do not exceed a length of three times their largest inside diameter.
(iii) We recommend that you use four-ply silicone-fiberglass fabric with a temperature rating of at least 315 °C for flexible connectors. You may use connectors with a spring-steel wire helix for support and you may use NomexTM coverings or linings for durability. You may also use any other nonreactive material with equivalent permeation-resistance and durability, as long as it seals tightly.
(iv) Use stainless-steel hose clamps to seal flexible connectors, or use clamps that seal equivalently.
(v) You may use additional flexible connectors to connect to flow meters.
(2) Tubing . We recommend using rigid 300 series stainless steel tubing to connect between flexible connectors. Tubing may be straight or bent to accommodate vehicle geometry. You may use “T” or “Y” fittings to join multiple connections, or you may cap or plug redundant flow paths if the engine manufacturer recommends it.
(3) Flow restriction. Use flow meters, connectors, and tubing that do not increase flow restriction so much that it exceeds the manufacturer's maximum specified value. You may verify this at the maximum exhaust flow rate by measuring pressure at the manufacturer-specified location with your system connected. You may also perform an engineering analysis to verify an acceptable configuration, taking into account the maximum exhaust flow rate expected, the field test system's flexible connectors, and the tubing's characteristics for pressure drops versus flow.
(b) For vehicles or other motive equipment, we recommend installing PEMS in the same location where a passenger might sit. Follow PEMS manufacturer instructions for installing PEMS in cargo spaces, engine spaces, or externally such that PEMS is directly exposed to the outside environment. We recommend locating PEMS where it will be subject to minimal sources of the following parameters:
(1) Ambient temperature changes.
(2) Ambient pressure changes.
(3) Electromagnetic radiation.
(4) Mechanical shock and vibration.
(5) Ambient hydrocarbons - if using a FID analyzer that uses ambient air as FID burner air.
(c) Use mounting hardware as required for securing flexible connectors, ambient sensors, and other equipment. Use structurally sound mounting points such as vehicle frames, trailer hitch receivers, walk spaces, and payload tie-down fittings. We recommend mounting hardware such as clamps, suction cups, and magnets that are specifically designed for your application. We also recommend considering mounting hardware such as commercially available bicycle racks, trailer hitches, and luggage racks where applicable.
(d) Field testing may require portable electrical power to run your test equipment. Power your equipment, as follows:
(1) You may use electrical power from the vehicle, equipment, or vessel, up to the highest power level, such that all the following are true:
(i) The power system is capable of safely supplying power, such that the power demand for testing does not overload the power system.
(ii) The engine emissions do not change significantly as a result of the power demand for testing.
(iii) The power demand for testing does not increase output from the engine by more than 1% of its maximum power.
(2) You may install your own portable power supply. For example, you may use batteries, fuel cells, a portable generator, or any other power supply to supplement or replace your use of vehicle power. You may connect an external power source directly to the vehicle's, vessel's, or equipment's power system; however, during a test interval (such as an NTE event) you must not supply power to the vehicle's power system in excess of 1% of the engine's maximum power.
[73 FR 37344, June 30, 2008, as amended at 75 FR 23058, Apr. 30, 2010; 86 FR 34575, June 29, 2021]