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Interpretation Response #PI-10-0001

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 11-18-2010
Company Name: B. Knight Natural Gas Services    Individual Name: Mr. Michael H. Kyle
Location state: VA    Country: US

View the Interpretation Document

Response text:

November 18, 2010

Mr. Michael H. Kyle
B. Knight Natural Gas Services
P.O. Box 5702
Midlothian, VA 23112

Dear Mr. Kyle:

In a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA) dated December 14, 2009, you requested an interpretation or opinion as to whether two specific installations of gas utilization equipment would meet the intent and requirements of  49 CFR § 192.197.

You provided two actual installations. In Installation 1, the value of outlet pressure could exceed 1 psig or 28-in water column (wc), and in Installation 2, the value of outlet pressure could approach 1psig (26-in wc). You stated your assumption is that the maximum operating inlet pressure allowed for most residential installations is limited to ½ psi (14-in wc) and that pressures in excess of 1 psi (28-in wc) are likely to cause damage to the appliance regulator.

First, you asked whether the bolded words in the following two subsections of § 192.197 have the same meaning: in § 192.197(a)(5), ". to prevent a pressure that would cause unsafe operation of any connected and properly adjusted gas utilization equipment" and in § 192.197(c)(3),". set to open so that the pressure of gas going to the customer does not exceed a maximum safe value."  The answer is that they do not have the exact same meaning.The phrase "unsafe operation" in § 192.197(a)(5) addresses both upper and lower pressure limits and means that the connection should regulate pressure so that it is neither so high as to create excessively high pilot light flames nor so low that the pilot light could extinguish and create the possibility of gas accumulation.The phrase "exceed a maximum safe value" in § 192.197(c)(3) addresses only the upper limit or high pressure.

Second, you asked what inlet pressure does § 192.197(a)(5) or § 192.197(c)(3) refer to?  Regarding the limit for inlet pressure, § 192.197 is a design requirement under Subpart D- Design of Pipeline Components. The design requirements under Subpart D apply to the design of pipeline system or components to operate under conditions that are known or reasonably foreseeable at the time of installation. Therefore, § 192.197 does not prescribe a specific value as long as the inlet pressure does not cause damage to the appliance's regulator.

Finally, you asked whether your recommendations in both installations are valid and meet the intent of § 192.197. Again, § 192.197 does not specify a specific value as long as the inlet pressure does not lead to unsafe conditions or cause damage to the gas utilization equipment or associated regulators.

I hope that this information is helpful to you. If I can be of further assistance, please contact me at 202-366-4046.


John A. Gale
Director, Office of Standards and Rulemaking

Regulation Sections

Section Subject
§ 192.197 Control of the pressure of gas delivered from high-pressure distribution systems