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Daily Average Send-Out
The total quantity of gas delivered for a period of time divided by the number of days in the period.
Damper
A valve, or plate, used to regulate the flow of air or other gases.
Darcy
A measure of permeability. A permeability of one darcy means that the material will pass a fluid of one centipoise viscosity through a section of one cubic centimeter at a rate of one cubic centimeter per second with a drop in pressure of one standard atmosphere.
Data Request
See DISCOVERY.
Deaerator
The apparatus used to separate the dissolved gases from the condensate.
Debentures
Certificates of indebtedness issued under an indenture agreement (administered by a trustee) representing long-term borrowings of capital funds, secured only by the general credit of the issuing corporation. Compare BONDS.
Debt Coverage Principle
A method to determine the cost of common equity component of return based on cost of the fixed components, debt and preferred stock.
Decommission
To remove (as a ship) from service.
Decontrol
The act of ending federal government control over the wellhead price of new natural gas sold in interstate commerce. Also termed "deregulation".
Dedicated Acreage
Acreage dedicated to a company by contract. More specifically, all gas produced from the dedicated acreage is dedicated to the purchasing company by contract.
Dedicated Gas Reserves
Gas reserves dedicated to a natural gas pipeline company by contract. For a pipeline it is the sum of all reserves dedicated to the company by contract.
Dedicated to Interstate Commerce
Gas reserves under contract to an interstate pipeline company and hence subject to the jurisdiction of the Commission and wellhead price controls under the NGA of 1938. The NGPA of 1978 extended the Commission's jurisdiction for wellhead pricing to essentially all gas but provided for phasing out wellhead price controls over time for certain gas.
Deep Gas
Gas found at depths greater than the average for a particular area; for FERC purposes, it is gas found at depths of more than 15,000 feet.
Deferred Credits
Accounts carried on the liability side of the balance sheet in which are recorded items being amortized as credits to income over a period of time (such as Unamortized Premium on Debt) and items held in suspense pending final transfer or disposition (such as Customer Advances for Construction, etc.)
Deferred Debits
Accounts carried on the asset side of the balance sheet in which are recorded items being amortized as charges against income over a period time (such as Unamortized Debt Discount and Expense) and items held in suspense pending final transfer or disposition (such as Extraordinary Property Losses, Clearing Accounts (Net Debit), etc.).
Deferred or Future Income Taxes
Amounts representing the tax effects of temporary differences in the recognition of revenue and expense items for income tax purposes and for financial reporting purposes such as the use of accelerated amortization and/or liberalized depreciation in income tax returns.
Deficiency Based GIC
See GAS INVENTORY CHARGE.
Deficiency Period
Used in association with the EQUITABLE SHARING MECHANISM. A period during which the current take-or-pay liabilities of the pipeline were incurred. A customer's cumulative deficiency in purchases during this period, in comparison to a BASE PERIOD, is compared to the system's total cumulative deficiencies to determine that customer's proportionate share of fixed take-or-pay charges. See BASE PERIOD, EQUITABLE SHARING MECHANISM and PURCHASE DEFICIENCY METHODOLOGY.
Deflection Temperature
The temperature at which a specimen will deflect a given distance at a given load under prescribed conditions of test. See ASTM D 648. Formerly called heat distortion.
Degradation
A deleterious change in the chemical structure, physical properties or appearance of a plastic.
Degree Day, Cooling
A measure of the need for air conditioning (cooling) based on temperature and humidity. Although cooling degree days are published for many weather stations, a specific procedure has not been generally accepted.
Degree Day, Heating
A measure of the coldness of the weather experienced, based on the extent to which the daily mean temperature falls below a reference temperature, usually 65 degrees F. For example, on a day when the mean outdoor dry-
Dehumidify
To reduce by any process the quantity of water vapor contained in a solid or gas.
Dehydration
The process of removing liquids and moisture content from gas or other matter.
Dekatherm
A unit of heating value equivalent to 10 therms or 1,000,000 Btu's.
Deliverability
The volume of gas a well, field, pipeline, or distribution system can supply in a given period of time. Also, the practical output from a storage reservoir. Compare CAPACITY, INSTALLED; STORAGE, UNDERGROUND.
Delivery by Non-Delivery
The delivery of gas through a meter where gas is currently being physically received. The delivery is accomplished by reducing physical receipts for the quantity delivered.
Delivery Point
Point at which gas leaves a transporter's system completing a sale or transportation service transaction between the pipeline company and a sale or trans-portation service customer.
Demand
The rate at which gas is delivered to or by a system, part of a system, or a piece of equipment, expressed in cubic feet or therms or multiples thereof, for a designated period of time called the demand interval. Compare LOAD.
Demand Based GIC
See GAS INVENTORY CHARGE.
Demand Charge
The portion of a rate for gas service which is billed to the customer whether they use the service or not. Depending on the rate design this charge is based on actual or estimated peak usage (1 or 3 days), annual needs or a combination of the two. Compare COMMODITY CHARGE.
Demand Costs (Rate)
That part of the total cost of service which must be recovered through use of a demand rate; i.e., a rate for each Mcf of gas representing the customer's demand on the Company's system.
Demand Day
That 24-hour period specified by a supplier-user contract for purposes of determining the purchaser's daily quantity of gas used (e.g., 8 AM to 8 AM, etc.). This term is primarily used in pipeline-distribution company agreements. It is similar to, and usually coincides with, the distribution company "sendout day".
Demand Diversity
The overall variation in the time at which individual demands occur. Compare DEMAND, COINCIDENT and DEMAND, NON-COINCIDENT.
Demand Interval
The period of time during which the flow is averaged in determining demand, such as 60-minute or 30-minute.
Demand Load
The rate of flow of gas required by a consumer or a group of consumers, often an average over a specified short time interval (cf/hr or Mcf/hr). Demand is the cause; load is the effect.
Demand Meters
A device which indicates or records the instantaneous, maximum or integrated (over a specified period) demand.
Demand Side Bidding
Process in which a utility issues a request for proposals to acquire DSM resources from energy service companies and customers, reviews proposals, and negotiates contracts with winning bidders for a specified amount of energy savings.
Demand Side Management (DSM)
Utility activities designed to influence the amount and timing of customer demand, producing changes to the
Demand Side Resource Portfolio
Comprehensive collection of DSM resources, both viable and non-viable, that are available, both currently and in the future to the utility.
Demand Side Resources
Resources obtained through the implementation of DSM that may be used as an alternative to traditional supply-side resources.
Demand, Average
The demand on a system or any of its parts over an interval of time, determined by dividing the total volume in therms by the number of units of time in the interval.
Demand, Billing
The demand upon which billing to a customer is based, as specified in a rate schedule or contract. It may be based on the contract year, a contract minimum, or a previous maximum and, therefore, does not necessarily coincide with the actual measured demand of the billing period.
Demand, Coincident
The sum of two or more demands which occur in the same demand interval.
Demand, Contract
The daily quantity of gas which the supplier agrees to furnish and for which the buyer agrees to pay, under a specific contract.
Demand, Integrated
The demand averaged over a specified period, usually determined by an integrating demand meter or by the integration of a load curve. It is the average of the instantaneous demands during a specified demand interval.
Demand, Maximum
The greatest of all the demands under consideration occurring during a specified period of time.
Demand, Minimum
The smallest of all the demands under consideration occurring during a specified period of time.
Demand, Non-Coincident
The sum of two or more individual maximum demands, regardless of time of occurrence, within a specified period.
Demonstration Scale Plant
A plant between pilot and commercial size built to demonstrate the commercial feasibility of a process.
Densitometer
An instrument used to determine the ratio of the density of a substance to the density of a given substance (as water or hydrogen) taken as a standard, when both densities are obtained by weighing in air.
Density
The weight of a unit of volume, usually expressed as pounds per cubic foot.
Density, Bulk
The weight per unit volume of a material including voids inherent in the material as tested.
Department of Energy (DOE)
The Department of Energy is the twelfth Cabinet Position, and it consists of the Office of the Secretary of Energy and the Federal Energy Regulatory Commission. It was created on August 4, 1977 as a result of the Department of Energy Organization Act of 1977. There are many subdivisions within the DOE, but the Economic Regulatory Administration and Energy Information Administration are two groups which have significant bearing on gas utility operations.
Depletion
As applied to natural gas producing land and land rights, means the loss in value incurred in connection with the exhaustion of a natural resource.
Depletion Allowance
A charge against income for the extraction of natural resources, commonly called "wasting assets" (i.e., gas, oil, coal, etc.).
Depreciable Plant
Usually tangible plant in service which is subject to depreciation, depletion, or amortization.
Depreciation
Return of investment through inclusion in cost of service (and rates) of a pro rata part of the cost of property, calculated to spread the total investment cost over a certain period of time or number of units that measure the useful life of the investment. Depreciation (in the Code of Federal Regulations) is to reimburse the company for "...the loss in service value not restored by current maintenance, incurred in connection with the consumption or prospective retirement of gas plant in the course of service from causes which are known to be in current operation and against which the utility is not protected by insurance. Among the causes to be given consideration are wear and tear, decay, action of the elements, inadequacy, obsolescence, changes in the art, changes in demand and requirements of public authorities, and, in the case of a natural gas company, the exhaustion of natural resources."
Depreciation Accounting
A system of accounting intended to distribute the cost of tangible capital assets, less salvage, (if any), over the estimated useful life of the unit in a systematic and rational manner.
Depreciation Expense
The cost of plant (less net salvage) recovered over the life of the plant through a reduction of income. This expense reflects the "using up" of plant (due to wear and tear, obsolescence, etc.) in the generation of income.
Depreciation Reserve
See ACCUMULATED PROVISION FOR DEPRECIATION AND AMORTIZATION.
Depreciation Reserve Ratio
The ratio of the accumulated depreciation to the recorded cost of surviving plant at any given date.
Depreciation, Accelerated
See DEPRECIATION, LIBERALIZED.
Depreciation, Asset Depreciation Range (ADR)
A system of tax depreciation which enables a corporation to choose any life falling within 20% of the designated class life for determining its annual depreciation charge. ADR requires an annual election and all depreciation records must be maintained by vintage year.
Depreciation, Declining Balance
One of the liberalized methods of computing depreciation (normally used for tax purposes). Under this method, the depreciation rate is stated as a fixed percentage per year and the annual charge is derived by applying the rate to the net plant balance, which is determined by subtracting the accumulated depreciation reserve.
Depreciation, Flow-Through
An accounting procedure under which current Net Income reflects decreases or increases in current taxes on income, arising from the use of liberalized depreciation or accelerated amortization for tax purposes instead of the straightline method. See DEPRECIATION, NORMALIZED.
Depreciation, Liberalized
This refers to certain approved methods of computing depreciation allowance for federal and/or state income tax purposes. These methods permit relatively larger depreciation charges during the earlier years, in contrast to the straight-line method, under which the annual charges are the same for each year. This is sometimes referred to as accelerated depreciation.
Depreciation, Normalized
An accounting method under which Net Income includes charges or credits equal to the decreases or increases in current taxes on income, arising from the use of liberalized depreciation or accelerated amortization for tax purposes instead of the straight-line method. The contra entries for such charges to Net Income are suspended in Balance Sheet accounts. In future years, there is a feedback of these suspended amounts to Net Income when increases in the then current taxes on income occur because liberalized depreciation or accelerated amortization was used for tax purposes in prior years. See DEPRECIATION, FLOW-THROUGH; RESERVE FOR DEFERRED OR FUTURE INCOME TAXES.
Depreciation, Straight-Line
A method of computing depreciation under which equal annual amounts are set aside for the ultimate retirement of the property at the end of its service life. For a property with an assumed 25-year life, the annual charge would be 4% per year, usually applied to the cost of the property less estimated net salvage.
Depreciation, Sum of the Years Digits (SYD)
One of the liberalized methods of computing depreciation, normally used for tax purposes. Under this method, the annual deduction is derived by multiplying the cost of the property less estimated net salvage, by the estimated number of years of service life remaining, and dividing the resultant product by the sum of all the digits would be 25+24+23+22+ etc. +5+4+3+2+1 or 325. A simple way to compute this figure would be to multiply the number of years by the number of years plus one and divide by 2, i.e., (25 X 26) : 2 = 325. The first year's full depreciation deduction would be 25/325ths; the second year's would be 24/325ths, etc., of the cost of the property.
Depreciation, Unit of Production
A method of depreciation whereby the asset is depreciated over an estimated life expressed in units of output rather than over an estimated life expressed as a period of time.
Deregulation
See DECONTROL.
Deriming
Adding heat to remove accumulated solid water or carbon dioxide constituents from low-temperature process equipment.
Desiccant
Any absorbent or adsorbent, liquid or solid, that will remove water or water vapor from a material. In a refrigeration circuit, the desiccant must be insoluble in the refrigerant.
Design Day
A 24-hour period of demand which is used as a basis for planning gas capacity requirements.
Design Day Availability
The amount of each type of gas arranged to be available on the design day and the maximum combination of such supplies. (In the case of purchased natural gas, the maximum day allocation, maximum day contract quantity, or FERC authorization).
Design Day Temperature
The mean temperature assumed for the Design Day.
Design Load
The maximum average rate of gas use by a group of appliances or customers over a specified short time period, usually 15 to 30 minutes.
Design Pressure
The maximum operating pressure permitted by various codes, as determined by the design procedures applicable to the material and location involved.
Desulfurization
The process by which sulfur and sulfur compounds are removed from gases or liquid hydrocarbon mixtures.
Detector, Holiday
See HOLIDAY DETECTOR.
Development
The drilling and related activities necessary to begin production after the initial discovery of oil or gas in a reservoir.
Development Well
See WELL, DEVELOPMENT.
Devonian Shale
Geological formations, typically hundreds of feet thick, that underlie much of the Appalachian Basin. It is known to contain much natural gas, but usually lacks sufficient natural permeability for ordinary production.
Diaphragm
A bellows inside a displacement type gas meter. Also, a membrane separating two different pressure areas within a control valve or regulator.
Die, Pipe Thread
The tool used for cutting external threads, usually at one passage. The essential distinctive feature of a die is its multiple cutting edges, while a chasing or threading tool usually has one, or at most, only a few cutting edges.
Dielectric Constant
The ratio of the capacity of a condenser with given dielectric and the capacity of the same condenser with a vacuum as a dielectric.
Dielectric Strength
The voltage that will rupture or puncture the material when placed between electrodes of a given size.
Differential Pressure
The pressure difference between two points in a system. For example, the difference in pressure between the upstream and downstream taps of an orifice plate, used to measure volume passing through the orifice.
Diffusion
The movement of a material, such as a gas or liquid, in the body of a plastic. If the gas or liquid is absorbed on one side of a piece of plastic and given off on the other side, the phenomenon is called permeability. Diffusion and permeability are not due to holes or pores in the plastic but are caused and controlled by chemical mechanisms.
Dig-in
When buried gas facilities are damaged by excavators.
Diluent
A neutral fluid added to another fluid to reduce the concentration of the second fluid in a mixture.
Dimension Ratio
The average specified diameter of a pipe divided by the minimum specified wall thickness. NOTE: Each pipe can have two dimension ratios depending on whether the outside or inside diameter is used. In practice, the outside diameter is used if the standard requirement and manufacturing control are based on this diameter. The inside diameter is used when this measure is the controlling one.
Direct Heating Equipment
See HEATER, INFRA-RED RADIANT.
Direct Installation Program
DSM program in which the utility directly installs DSM measures within customers homes or businesses.
Direct Sale
Contract sale of natural gas by producer to end user or local distribution company, usually for a term of a year or longer.
Direct Vent Appliance
Gas appliance designed so that all combustion air is derived directly from the outside, and all fuel gases are discharged to the outside through an exterior wall.
Direct-Fired
A heating unit in which the combustion products are mixed with the air or liquid being heated. Compare INDIRECT-FIRED.
Disabling Injury Illness Incidence
See INJURY/ILLNESS INCIDENCE RATE, DISABLING.
Discount on Capital Stock
The excess of par or stated value over the price paid to the company by the shareholders for original issue shares of its capital stock.
Discounted Cash Flow (DCF)
A method to determine the cost of common equity component of return using a discounted stream of future cash dividends.
Discovery
Part of the ratemaking process, after a rate or other filing and after suspension by the Commission which orders a hearing, where parties including the filing company can, through requests for data, obtain more information about the (rate) filing and the particular issues set for hearing.
Dispatchability of DSM
The ability of the utility to schedule and control, directly or indirectly, manually or automatically, the timing and volumes of DSM measures.
Dispatching
The control of product flow in a system involving the assignment of load to the various sources of supply to meet the desired objectives.
Dispersion
See RETIREMENT DISPERSION.
Displacement
Displacement transactions permit the lateral movement of gas through a transportation network. The configuration of many pipelines is such that it may not be apparent whether a given movement of gas is forward or backward from the point of receipt. It can be argued that all transportation service is performed by displacement as the physical delivery of the same molecules of gas is impossible. See BACKHAUL.
Dissolved (Solution) Gas
Natural gas originally in solution within the reservoir crude oil. As the reservoir pressure is reduced due to production, gas is released from solution in the oil, allowing it to migrate as free gas to a wellbore and be produced or to the crest of the reservoir where it can collect and form a secondary gas cap. In addition, gas is released from solution in the oil within the wellbore as the oil is produced. Thus, most oil wells, except stripper wells producing from reservoirs where the pressure and solution gas has been depleted, produce gas with the oil. Even oil fields with no free gas originally present can produce large volumes of gas since considerable gas can be present in solution in the oil.
Distillate, Natural Gas
See NATURAL GAS DISTILLATE.
Distribution
The act or process of distributing gas from the city gas or plant that portion of utility plant used for the purpose of delivering gas from the city gate or plant to the consumers, or to expenses relating to the operating and maintenance of distribution plant.
Distribution Company
Gas Company which obtains the major portion of its gas operating revenues from the operation of a retail gas distribution system, and which operates no transmission system other than incidental connections within its own system or to the system of another company. For purposes of A.G.A. statistics, a distribution company obtains at least 90 percent of its gas operating revenues from sales to ultimate customers, and classifies at least 90 percent of mains (other than service pipe) as distribution. Compare INTEGRATED COMPANY; TRANSMISSION COMPANY, GAS.
Distribution System, Gas
See SYSTEM TYPE.
Distrigas Method
A formula used to allocate overhead costs of a parent to its affiliates. This method deviates from the "Mass Formula" by replacing the gross revenue factor with a factor that is computed based on net operating revenues (operating income before interest and federal taxes). This modification to the "Mass Formula" was the result of the Commission's concern, that the gross revenue factor would be distorted when allocating costs from an unregulated entity because of the inclusion of purchase gas costs in gross revenue for regulated pipelines. See MASSACHUSETTS (MASS) FORMULA.
Diversity
A characteristic of the variety of gas loads whereby individual maximum demands usually occur at different times. Therefore, the maximum coincident load of a group of individual loads is less than the sum of the individual maximum loads. Diversity among customers' loads results in a diversity among the loads of distribution mains and regulators as well as between entire systems. Compare LOAD DIVERSITY.
Diversity Factor
The ratio of the sum of the non-coincident maximum demands of two or more loads to their coincident maximum demands for the same period. Compare COINCIDENCE FACTOR.
Diversity, Demand
See DEMAND DIVERSITY.
Diverter, Down Draft
See DRAFT HOOD.
Divertible Gas Supplies
Gas supplies that are free to be sold to the highest bidder. They must be uncommitted, or committed under contract to a buyer for no longer than some short period (such as one year). They may be totally uncommitted to any buyer. In addition, they must be available to a pipeline's customers at delivered city-gate prices that are competitive enough to prevent the pipeline from exercising market power. In GAS INVENTORY CHARGE proceedings, the Commission has stated that there must be sufficient divertible gas supplies, as well as COMPARABILITY OF SERVICE, in order to find that the pipeline is operating in a competitive environment.
Dividend Appropriations
Amounts declared payable out of unappropriated retained earnings as dividends on outstanding preferred or common stock.
Docket
A formal proceeding with the Federal Energy Regulatory Commission or local Public Utility Regulatory Commission for construction or abandonment of facilities, changes in rates and rulemaking.
Docket Number
At the time a document is filed with the Commission it is assigned a number. Docket numbers take different forms for different types of filings, i.e., RP89-147-000 : RP = Rate Proceeding, 89 = the year filed, 147 = the number assigned by the Commission, 000 = Subdocket number assigned sequentially by the Commission.
Dollar-Years
The aggregate years of service for plant dollars during the life of the plant. Expired dollar-years are the aggregate years of service realized as of any given date. Future dollar-years are the aggregate years of service remaining. The area under the survivor curve represents the total dollar-years of service.
Double Block and Bleed System
A valuing system wherein a full-flow vent valve is located on piping between two shut-off valves in series for the purpose of bleeding to atmosphere excess pressure between the valves.
Double Glazing
Two panes of glass, usually parallel, with an air space between, used to provide increased thermal and/or sound insulation.
Double Leverage
Concept used in developing a company's proper capital structure. It occurs when the company participates in a project financed joint venture through a wholly owned subsidiary. See CAPITAL STRUCTURE.
Double-Breasted Buying
A practice that pipelines are sometimes accused of employing-buying large packages of gas, and deciding later whether its marketing subsidiary bought it for system supply, or whether its marketing subsidiary bought it for resale on the spot market. Independent marketers complain that this practice gives pipelines an undue advantage in the marketplace. Pipelines counter that their pipeline sales and marketing departments are now completely separate functions.
Down Draft (Back Draft)
A flow of air down the chimney or flue because of adverse draft conditions.
Downstream
Any point in the direction of flow of a liquid or gas from the reference point. Compare UPSTREAM.
Downstream Pipeline
The pipeline receiving natural gas at a pipeline inter-connect point.
Draft
A difference of pressure which causes a flow of air and/or flue gases through the boiler, flue connector, breeching, flue, or chimney.
Draft Fan, Forced
A blower type fan used to force draft air to the furnace.
Draft Fan, Induced
An exhaust-type fan used to draw flue gases through the superheater, economizer, air heater and precipitator.
Draft Hood
A device built into an appliance, or made a part of the flue or vent connector from an appliance, which is designed to (a) assure the ready escape of the products of combustion from the combustion chamber in the event of no draft, back draft, or stoppage beyond the draft hood; (b) prevent a back draft from entering the combustion chamber of the appliance; and (c) neutralize the effect of stack action of the chimney or gas vent upon the operation of the appliance.
Draft Regulator (Draft Stabilizer)
A device which functions to maintain a desired draft in the appliance by automatically reducing the draft to the desired value.
Draft, Mechanical
Draft that is caused by mechanical means, such as a fan.
Draft, Natural
Draft that is caused by a thermal upset in which temperature differences change the weight (pressure) of air.
Drill Pipe
See PIPE, DRILL.
Drilling
See CABLE TOOL and ROTARY DRILLING.
Drip
A container or segment of piping placed at a low point in a system to collect condensate, dust, and foreign material, enabling their removal. Also known as Drip Leg and Drip Pot. Compare SERVICE DRIP.
Drip Box
A box around a drip, accessible at grade level, which protects the drip and pipe.
Drip Oil
The light oil or hydrocarbon liquids condensed in a piping system when the gas is cooled. Both natural and manufactured gas can be sources of condensates.
Drip Riser or Drip Stock
A small diameter pipe (with or without valve control) connecting drip with surface level.
Dry Gas
See GAS, NATURAL
Dry Hole
A well which does not yield gas and/or oil in quantity or condition to support commercial production.
DSM Costs, Administrative
Costs incurred by a utility for DSM program planning, design, marketing, implementation, and evaluation. Included are labor-related costs, office supplies and expenses, data processing, and other such costs. Excluded are costs of marketing materials and advertising, purchases of equipment for specific programs, and rebates or other incentives.
DSM Costs, Equipment
The price of all equipment that a utility directly purchases for a DSM program, whether for its own use or for distribution to program participants.
DSM Costs, Marketing
All DSM costs directly associated with the preparation and implementation of the strategies designed to encourage participation in a program.
DSM Costs, Monitoring and Evaluation
DSM expenditures associated with the collection and analysis of data used to assess program operation and effects.
DSM Costs, Non-Utility
DSM expenses incurred by customers and trade allies associated with participation in a DSM program that are not reimbursed by the utility.
DSM Costs, Participant
Costs associated with participation in a DSM program that are paid by the participating customer and not reimbursed by the utility.
DSM Costs, Planning
Any expenditures that are required for a DSM program prior to program implementation.
DSM Costs, Utility
All expenses incurred by a utility in a given year for operation of a DSM program, including administrative, equipment, marketing, and any others, regardless of whether the costs are capitalized or expensed.
DSM Potential
See ACHIEVABLE POTENTIAL, ECONOMIC POTENTIAL, MARKET POTENTIAL and TECHNICAL POTENTIAL.
Dual Fuel
An energy use for which there is an alternative fuel.
Dual-Fuel Capability
Ability of an energy-using facility to alternately use more than one kind of fuel.
Duct
A passageway made of sheet metal or other suitable material, not necessarily leak-tight, used for conveying air or other gas at low pressures.
Duct System
A series of ducts, elbows, and connectors to convey air, or other gas at low pressure, from one location to another.
Dutchman
A filler-piece used to close a gap between two pieces of pipe or between a pipe or fitting and a piece of equipment where the pipe is too short to effect the closure or where the pipe and equipment may be out of alignment.
Dye Penetrant Weld Examination
A method for inspecting for surface defects of welds by using a dye and developer applied to the weld.

 
 

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