Lessons Learned 

from Natural Gas STAR Partners 

Using Hot Taps For In Service Pipeline 

Connections 

Executive Summary 

Natural gas transmission and distribution companies need 

to make new connections to pipelines many times a year to

expand or modify their existing system. Historically, this

has necessitated shutting down a portion of the system

and purging the gas to the atmosphere to ensure a safe 

connection. This procedure, referred to as a shutdown

interconnect, results in methane emissions, loss of product

and sales, occasionally customer inconvenience, and costs

associated with evacuating the existing piping system. 

Hot tapping is an alternative procedure that makes a new 

pipeline connection while the pipeline remains in service,

flowing natural gas under pressure. The hot tap procedure

involves attaching a branch connection and valve on the 

outside of an operating pipeline, and then cutting out the

pipe-line wall within the branch and removing the wall 

section through the valve. Hot tapping avoids product 

loss, methane emissions, and disruption of service to 

customers. 

While hot tapping is not a new practice, recent design 

improvements have reduced the complications and 

uncertainty operators might have experienced in the past.

Several Natural Gas STAR transmission and distribution 

Partners report using hot tap procedures routinely—small 

jobs are performed almost daily while larger taps (greater

than 12 inches) are made two or three times per year. 

By performing hot taps, Natural Gas Star Partners have 

achieved methane emissions reductions and increased 

revenues. Gas savings are generally sufficient to justify 

making all new connections to operating lines by hot 

tapping. The payback period for utilizing hot tapping is

often immediate. 

Technology Background 

In natural gas transmission and distribution systems, it is 

frequently necessary to relocate or expand existing

pipelines, install new valves or repair old ones, install new

laterals, perform maintenance, or access lines during 

emergencies. Historically, it has been common practice to

shut down the portion of the system during the alteration,

vent the gas within the isolated segment, and purge the

pipeline with inert gas to ensure a safe connection. 

The procedure for performing the shutdown interconnect

differs slightly depending on system pressure. In highpressure systems, the surrounding valves are closed to

isolate the pipeline segment and additional stoppels 

(inserted plugs) are placed next to the valves to prevent

natural gas leakage and improve the safety conditions at

the interconnection site. In a low-pressure system, the 

length of pipeline that is shutdown is typically much 

shorter. Rather than shutting the surrounding valves, 

stoppels are used to isolate the portion of the pipeline

directly around the area of the tap. In both cases, the gas

in the isolated pipeline segment is vented and the line is 

purged. 

The impacts associated with performing a shutdown 

interconnect are both economic and environmental. Gas 

vented from the pipeline segment represents a loss of 

product and an increase in methane emissions. In 

Method for 

Reducing 

Natural Gas 

Losses 

Volume of 

Natural Gas 

Savings 

(Mcf) 

Value of Natural Gas Savings 

($) Other 

Savings 

($) 

Implementation 

Cost ($) 

Other 

Costs 

($) 

Payback (Months) 

$3 per 

Mcf 

$5 per 

Mcf 

$7 per 

Mcf 

$3 per 

Mcf 

$5 per 

Mcf 

$7 per 

Mcf 

Hot Tap 

Connectiona 

24,400 per 

year 

$73,200 

per year 

$122,000 

per year 

$170,800 

per year 

$13,680 per 

yearb $47,409 $62,222 per yearc 15 10 

General Assumptions: 

a Annual savings and costs are based on an average 320 hot taps (of various sizes) per year. b Other savings shown are for inert gas. 

c Other costs includes the O&M and contract services costs. 

7 

Economic and Environmental Benefits 

1 
 

 

 

 

 

 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

addition, removing a pipeline segment from service can

occasionally cause gas service interruptions to customers.

For example, a shutdown connection on a steel line can

require one to three or more days of pipeline outage and 

possible interruption of natural gas shipments in addition 

to the release of methane to the atmosphere. 

Hot tapping is an alternative technique that allows the 

connection to be made without shutting down the system 

and venting gas to the atmosphere. Hot tapping is also

referred to as line tapping, pressure tapping, pressure

cutting, and side cutting. The process involves attaching 

branch connections and cutting holes into the operating

pipeline without interruption of gas flow, and with no

release or loss of product. Hot taps permit new tie-ins to

existing systems, the insertion of devices into the flow 

stream, permanent or temporary bypasses, and is the 

preparatory stage for line plugging with inflatable, 

temporary balloon plugs (stoppels). 

Hot tapping equipment is available for almost any pipeline

size, pipe material, and pressure rating found in 

transmission and distribution systems. The primary

equipment for a typical hot tap application includes a 

drilling machine, a branch fitting, and a valve. Hot 

tapping equipment is described below and shown in 

Exhibit 1. 

Drilling machine. The drilling machine generally

consists of a mechanically driven telescoping boring

bar that controls a cutting tool. The cutting tool is 

used to bore a pilot hole into the pipeline wall in

order to center a hole saw that cuts out the “coupon,”

or curved section of pipeline wall. 

Fitting. Connection to the existing pipe is made

within a fitting, which can be a simple welded nipple 

for small (e.g., one inch) connection to a larger 

pipeline, or a full-encirclement split-sleeve tee for 

extra support when the branch is the same size as 

the parent pipeline. The tee wraps completely

around the pipeline, and when welded, provides 

mechanical reinforcement of the branch and carrier 

pipe. 

Valve. The valve on a hot tap connection can be

either a block valve or a control valve for the new 

connection, and must allow the coupon (section of 

pipeline wall cut out by the drilling machine) to be 

removed after the cutting operation. Suitable valves 

include a ball or gate valve, but not a plug or 

butterfly valve. 

Exhibit 1: Schematic of Hot Tapping 

Machine with Profile 

Exhibit 2 provides a general schematic of a hot tapping 

procedure. The basic steps to perform a hot tap are: 

1. Connect the fitting on the existing pipeline by welding 

(steel), bolting (cast iron), or bonding (plastic) and 

install the valve. 

2. Install the hot tap machine through the permanent

valve. 

3. Perform the hot tap by cutting the coupon from the 

pipeline through the open valve. A special device 

retains the “coupon” for removal after the hot tap 

operation. Withdraw the coupon through the valve

and close the valve. 

4. Remove the tapping machine and add the branch

pipeline. Purge oxygen, open the valve, and the new 

connection is put into service. 

Hot taps can be vertical, horizontal, or at any angle around 

the pipe as long as there is sufficient room to install the 

valve, fitting, and tapping machine. Current technology

allows for taps to be made on all types of pipelines, at all 

pressures, diameters, and compositions, even older pipes

merging with new. New, lightweight tapping machines 

2 
 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

Exhibit 2: Schematic of Hot Tapping Procedure 

are also available that allow a hot tap to be performed by a

single operator, without additional blocking or bracing. 

Safety manuals and procedural outlines are available from

the American Petroleum Institute (API), American Society

of Mechanical Engineers (ASME), and other organizations

for welding on in-service pipelines for all sizes, flow rates, 

and locations. These manuals provide information on 

what to consider during welding, including burn-through

prevention, flow in lines, metal thickness, fittings, post 

weld heat treatment, metal temperature, hot tap 

connection and welding design, and piping and equipment 

contents. 

Vendor manuals and equipment catalogues are also good

sources for determining which size and type of equipment

is most appropriate. Several vendors have published

comprehensive outlines and guides for performing hot tap 

procedures, including information on tapping on various

materials, job-site evaluation and preparation, selection 

and installation of fittings and other equipment, and 

safety precautions. Most importantly, because this is a 

hazardous procedure, each potential hot tap must be

evaluated on a case-by-case basis and a detailed, written

procedure should be prepared or reviewed before starting

each job to ensure that all steps are taken properly and 

safely. 

Economic and Environmental Benefits 

Key economic and environmental benefits of employing hot 

tapping procedures instead of shutdown connections 

include: 

Continuous system operation—shutdown and service 

interruptions are avoided. 

No gas released to the atmosphere. 

Avoided cutting, realignment and re-welding of 

pipeline sections. 

Reduction of costs associated with planning and 

coordination—meetings, schedules, paperwork, lost 

production, and direct manpower. 

Increased worker safety. 

Elimination of obligations to notify customers of gas 

outages. 

By ensuring that best practices are followed when 

performing a hot tap, the time required for the procedure, 

as well as the potential for failure, is reduced. 

Decision Process 

Operators can assess the economics of performing a hot tap

as an alternative to a shutdown connection by following 

the five steps below: 

Step 1: Determine physical conditions of the existing 

line. 

In preparation for a hot tap project, operators will need to

determine the maximum operating pressure (during the

hot tap), type of pipe material (steel, cast iron, plastic), and 

condition of the parent pipeline (internal/external 

corrosion, wall thickness) to assure a safe project. A hot 

tap connection can be made on a pipeline only where the

parent pipe material is in good condition. Other conditions 

to evaluate include the location of nearby valves for 

emergency isolation in the event of an accident, the desired 

Five Steps for Assessing Hot Tap Economics: 

1. Determine physical conditions of the existing line. 

2. Calculate cost of performing a shutdown interconnect. 

3. Calculate the cost of a hot tap procedure. 

4. Evaluate the gas savings benefits of hot tapping. 

5. Compare the options and determine the economics of hot tapping. 

3 
 

 

 

 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

The average methane content of natural gas varies by natural gas 

industry sector. The Natural Gas STAR Program assumes the 

following methane content of natural gas when estimating 

methane savings for Partner Reported Opportunities. 

Production 79 % 

Processing 87 % 

Transmission and Distribution 94 % 

Methane Content of Natural Gas 

tap diameter, working space around the connection, 

location of other pipeline welds, and imperfections or 

obstructions. Operators should also determine if the line

is “looped,” as many gas transmission companies avoid 

operational disruptions by shifting the load to a parallel 

line. It is advisable to develop and follow a written plan to

assure full and proper evaluation of a future connection. 

Step 2: Calculate cost of performing a shutdown 

interconnect. 

The cost of an actual project would include direct costs 

such as material and equipment, welding requirements, 

quality control, blowdown and purge costs, labor, and 

scheduling expenses. Additional indirect expenses or

“hidden” costs might include the cost of shut-off valves,

advertising if service is to be interrupted, relighting of

customer services, and excavating for stopples and purge 

connections. Operators would be advised to reference 

historical data to determine these costs. 

For the purposes of this scoping analysis, material and

labor costs for cutting out the line section and welding in a

tee connection in the shutdown method are assumed to be 

comparable to the cost of welding on the fitting and 

performing the hot tap when the branch connection is the

same size as the pipeline. However, the costs of the gas

lost through venting and inert gas purging are unique to

the shutdown interconnect. 

The formulas used to determine the cost of a shutdown 

interconnect are shown in Exhibit 3. For these 

calculations, low pressure is defined as less than 2 psig. 

For comparative purposes, calculating the cost of a 

shutdown interconnect should take into consideration a 

multiple-project scenario. This multiple-project

perspective allows for a more complete comparative cost 

analysis given the up-front capital costs of owning and 

operating a hot tap machine and the need to perform

several interconnections throughout a given year. Exhibit 

4 illustrates how the cost calculations in Exhibit 3 can be 

applied in a multiple connection scenario. The 

hypothetical situation presented includes several projects 

on pipelines of various sizes and pressures. Cost 

calculations, however, are only provided for the 4-inch

pipeline scenario and only cover direct costs. 

Again, individual operators will need to reference company 

records to determine the exact procedures and factors to 

use when performing shutdown interconnects. The 

procedures described above are general guidelines for 

preliminary economic assessment and can differ from 

company to company. Additional factors that are company 

specific include gas leakage past the pipeline valves on 

both ends of the shutdown, number of stoppers, tap holes 

for venting and purging, and type of purge gas. Leakage is

particularly important as large pipeline block valves can 

leak significant volumes of gas because they are used 

infrequently and the valve seat can accumulate debris that

inhibits a tight seal. The volume of leakage is highly

variable, dependent on valve type, age, pipeline pressure 

and service (dry gas causes much less corrosion and 

accumulation of debris than wet gas). If a Partner’s 

individual evaluation following this Lessons Learned 

results in marginal economic justification, then company

experience on pipeline valve leakage should be factored in 

to improve the economics. 

Step 3: Calculate the cost of a hot tap procedure. 

When comparing the up-front costs of hot tapping with

shutdown interconnects the only significant difference is 

the cost of the hot tap equipment. The tee fitting or full

encirclement sleeve, and the valve have nearly the same

cost for either method when the branch is essentially the 

Nelson Price Indexes 

In order to account for inflation in equipment and 

operating & maintenance costs, Nelson-Farrar 

Quarterly Cost Indexes (available in the first issue of 

each quarter in the Oil and Gas Journal) are used to 

update costs in the Lessons Learned documents. 

The “Refinery Operation Index” is used to revise

operating costs while the “Machinery: Oilfield Itemized 

Refining Cost Index” is used to update equipment 

costs. 

To use these indexes in the future, simply look up the 

most current Nelson-Farrar index number, divide by 

the February 2006 Nelson-Farrar index number, and, 

finally multiply by the appropriate costs in the Lessons 

Learned. 

4 
 

 

 

 

Using Hot Taps For In Service Pipeline Connections

(Cont’d) 

Exhibit 3: Calculating the Cost of Shutdown Interconnect 

Given: 

D = diameter of pipeline (inches) 

T = taphole diameter (inches) - for low pressure shutdown with tapholes for stoppers 

L = length of pipeline between tapholes (feet) - for high pressure shutdown 

P = line pressure (psia for low pressure, psig for high pressure) 

Ppgas = current purge gas market price ($/Mcf) - assumed $8/Mcf 

Pg = current gas market price ($/Mcf) - assumed $7/Mcf 

Ce = cost of extra excavation, use company records ($) 

Cp = cost of purge connections and excavation 

Cs = cost of hidden shutdown expenditures, see Appendix ($) 

Cf = cost of fittings, see Appendix ($) 

Time Taphole is open = from prior experience (minutes) 

1. Calculate A = area of pipeline (ft2

) = 

2. Calculate Vp = volume of pipeline (Mcf) = 

3. Calculate Vpgas = volume of purge gas = VP * 2.2 (shutdown + restore + 20% wasted) 

4. Calculate Cpgas = cost of nitrogen purge gas = Vpgas * Ppgas 

5. Calculate Vg = volume of gas lost in high pressure systems: Vg (Mcf) = 

Vg = volume of gas lost in low pressure systems: Vg (Mcf) = 

6. Calculate Cg = cost of gas lost ($) = Vg * Pg 

Calculate Indirect Costs: 

1. Calculate Ce = cost of extra excavation for tie-in ($) 

2. Calculate Cp = cost of purge connections ($) 

3. Calculate Cs = cost of hidden shutdown expenditures ($) 

4. Calculate Cf = cost of fittings ($) 

5. Calculate Ci = indirect costs ($) = Ce + Cp + Cs + Cf 

Calculate Total Costs: 

Calculate Ctotal = total cost ($) = Cg + Cpgas + Ci 

Calculate Direct Costs: 

1444 183

3 .14 2 

2 

22 D

in

ftD



 































  3 1,000 ft

McfLA

1,000 

*0.372 

1,000 

2 



 





 L PD

 

60 

. 2 PT No of Tapholes Time taphole is open 





min 

hr 





Source: Pipeline Rules of Thumb, p. 270 and p. 278 

5 
 

 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

Exhibit 4: Hypothetical Scenario and Example Calculation of Lost Gas 

and Purge Gas Costs for a Shutdown Interconnect 

Given: 

A pipeline company requires numerous shutdown or hot tap connections as follows: 

Pipeline Diameters, inches 4 8 10 18 

Pipeline Pressures, psig 350 100 1,000 200 

Pipeline Lengthsa

, milesb 2 1 3 2 

Annual Tapsc

, number 250 30 25 15 

(1) Calculate: Vs = Volume of Natural Gas Lost 

Vg (Mcf) = 

Vg = 

Vg = 22 Mcf 

(2) Calculate Vpgas = Volume of Purge Gasd 

Vpgas (Mcf) = 

Vpgas = 

Vpgas = 2 Mcf 

(3) Calculate: Value of Gas Lost by Shutdown Interconnects (Including Purge Gas) 

Cost = Cg + Cpgas = Vg * Pg + Vpgas * Ppgas 

Cost = (22 Mcf * $7/Mcf) + (2 Mcf * $8/Mcf) 

Cost 

a Isolation length between block valves or stoppers. 

b Formula requires length in feet (1 mile = 5,280 feet). 

c Scenario is based on Partner and vendor information. 

d Inert gas assumed to be nitrogen. 

= $170 for each of the 4-inch pipeline shutdown interconnects 

1,000 

0.372

1,000 

2 













  



 



  L PD

1,000 

0.372 

1,000 

5,2802 35042 













 



 



  

2.2

1,000 

183 

2 

















  LD

2.2 

1,000 

183 

5,280242 

















 

6 
 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

same size as the pipeline (information on fitting types and

costs is shown in the Appendix). The cost of welding a full

encirclement sleeve is nearly the same as the cost of 

welding a tee fitting in a line. Labor cost for cold cutting 

the pipeline and hot tap cutting out a coupon are 

sufficiently close for this type of feasibility evaluation. 

Maintenance costs apply only to hot tap equipment, such 

as drill sharpening and other equipment care and 

replacement. 

Tapping machines come in several sizes, and a single 

machine can perform hot taps from 3 to 12 inches. Less 

expensive machines can be purchased to perform small 

(e.g., 1 to 3 inch) taps. In general, capital costs for

purchasing the hot tap machines typically used by gas 

companies for the most common sized connections range 

from $17,287 to $30,122. 

Equipment cost is normally a one-time capital expenditure

and can be depreciated over the life of the equipment,

typically 15 to 20 years. Each company, however, should

calculate the depreciation in the same manner used for

other equipment purchases (e.g., amortized, over a fixed

period of time). This should be considered in conjunction

with how often the machine will be used in the future. To 

make this determination, operators should look at 

company records to determine the number of times similar

connections have been performed. 

Typically, a company that performs several hot taps a year

will find it economical to own the equipment, especially in

sizes up to 12 inches, and to maintain trained personnel to 

perform the service. These jobs are usually simpler and

require less specialized training than larger hot tap jobs. 

For larger and less frequent hot taps a company might 

consider it more cost effective to hire a contractor who will 

supply the equipment and trained personnel. Most hot tap

vendors will supply all necessary tapping equipment,

including the drilling machine, fittings, valves, cutters,

and repair services. The majority of vendors also offer

contract services for larger or infrequent jobs, or will rent

out the tapping equipment. Supplying support services, 

such as excavation, welding, and cranes, can reduce the 

costs of using an outside contractor. 

Other factors, such as the line material and thickness, 

system pressure, and temperature, should also be 

considered when determining the alternatives of 

purchasing hot tapping equipment or hiring contractors. A 

company should evaluate how often the tapping equipment

would be used and if they would realize savings by owning 

and maintaining the equipment and training operators. 

Exhibit 5: Hot Tap Expenses 

Connection 

Size 

Capital Cost ($) Contracting 

Service 

Machinea Material Cost ($) 

Equipment 

O&M Cost 

($/yr) 

Small Taps 

(<12”) 

17,287 -

30,122 - - 724 - 7,235 

Large Taps 

(>12”) 

130,963 -

261,927b 

2,619 -

11,944b 1,447 - 5,788 -

a

 Hot tap machines can last from 5 to 40 years. A company can perform 

as may as 400 small taps per year. 

b

 Most companies will find it more economical to contract out large hot 

tapping jobs, and would not therefore incur these costs. 

Note: Cost information provided by Hot Tap manufacturers and 

contractors. Prices are only provided for the most economic options. 

Exhibit 5 presents ranges of hot tapping costs for both 

equipment purchase and contracted services. The cost 

ranges shown include all materials; additional expenses

will result from labor and maintenance expenditures, as 

discussed above. Vendors state that the operations and 

maintenance (O&M) costs can vary greatly, depending on

the number of taps performed and equipment and 

procedural care. 

Exhibit 6 shows the equipment, O&M, and contractor 

services cost to perform the 320 taps per year in the 

hypothetical scenario first described in Exhibit 4. The 

assumption is made that the 4”, 8”, and 10” taps (a total of 

305 taps) would be performed by the company. Because 

few taps equal to or larger than 18 inches are performed 

Exhibit 6: Estimated Annual Hot Taps Costs 

for the Hypothetical Scenario 

Given: 

Equipment cost per machine = $23,704a 

Operations and maintenance (O&M) cost per machine = $3,979a 

Contract services cost per tap = $3,618a 

Number of hot tap machines = 2 

Number of contracted taps = 15 (all taps 12 inches and larger) 

Calculate: 

Total equipment cost = $23,704 * 2 = $47,409 

Total O&M cost = $3,979 * 2 = $7,959 

Contract services cost = $3,618 * 15 = $54,263 

a Average costs from ranges in Exhibit 5. 

7 
 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

each year, these taps (a total of 15 taps) would be 

contracted to vendors. The equipment cost includes the 

purchase cost of two small (<12”) tap machines. For the 

purpose of this Lessons Learned, the average value of the 

purchase, O&M, and contracting service costs listed in

Exhibit 5 are used to complete the cost analysis for the 

hypothetical scenario. Based on these assumptions the

total equipment cost is calculated at $47,409, the O&M 

cost at $7,959 and the contract services cost at $54,263. 

Step 4: Evaluate the gas savings benefits of hot 

tapping. 

Exhibit 7 presents the natural gas and purge gas savings 

associated with hot tapping on small and large diameter 

high-pressure pipelines in the hypothetical scenario of 320 

taps per year. The values are calculated using the

equations in Exhibit 3, multiplied by the number of annual

connections. Gas losses associated with shutdown 

interconnects are the primary savings when these 

connections are made by hot tapping. 

Step 5: Compare the options and determine the 

economics of hot tapping. 

The economic analysis shown in Exhibit 8 compares the

significant cost and benefit differences between hot 

tapping and shutdown interconnections for the 

hypothetical scenario of 320 taps per year. The significant

costs are the purchase, operation and maintenance of hot 

Exhibit 7: Estimated Annual Gas Savings for the 

Hypothetical Scenario 

Tap 

Scenario 1 Annual 

Taps 

Number 

Natural Gas 

Savings 

Total 

Gas 

Savingsc 

Pipelinesa 

Per 

Tap 

Mcf 

Annual 

Mcf 

Per 

Tap 

Mcf 

Annual 

Mcf $ 

Purge Gas 

Savingsb 

4” pipeline 

350 psig, 

2 mile line 

250 22 5,500 2 500 42,500 

8” pipeline 

100 psig, 

1 mile line 

30 13 390 4 120 3,690 

10” pipeline 

1,000 psig, 

3 mile line 

25 589 14,725 19 475 106,875 

18” pipeline 

200 psig, 

2 mile line 

15 255 3,825 41 615 31,695 

Total Annual 320 24,440 1,710 184,760 

a The sizes and number of taps from scenario given in Exhibit 4. 

b Example for 4-inch pipe interconnect shown in Exhibit 4. 

c Natural gas valued as $7 per Mcf, inert gas (nitrogen) valued at $8 per Mcf. 

tapping equipment and/or contracting for hot tapping

services. In this scenario, both costs are included: the 

purchase of two hot tapping machines for $47,409 for the 

smaller sizes and contracting the 15 large taps at $54,263 

per year. The purchased hot tap machines are operated

and maintained at $7,959 per year. All these costs are 

Exhibit 8: Economic Analysis of Hot Tap Versus Shutdown 

Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 

Capital Cost ($) (47,409) 0 0 0 0 0 

Contract Service Cost ($) 0 (54,263) (54,263) (54,263) (54,263) (54,263) 

O&M Cost ($) 0 (7,959) (7,959) (7,959) (7,959) (7,959) 

Total Cost ($) (47,409) (62,222) (62,222) (62,222) (62,222) (62,222) 

Natural Gas Savings ($) 171,080 171,080 171,080 171,080 171,080 

Inert Gas Savings ($) 13,680 13,680 13,680 13,680 13,680 

Net Benefit ($) (47,409) 122,538 122,538 122,538 122,538 122,538 

Payback (months) 

IRR 

NPVa 

5 

258% 

$417,107 

a Net Present Value (NPV) based on 10% discount rate for 5 years. 

8 
 

 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

calculated in Exhibit 6. Many expenses, including the cost

of fittings, valves and basic labor, are assumed to be

similar in both hot tap and shutdown procedures, and

therefore can be excluded in the comparative analysis. A 

more complete analysis can be done by evaluating and 

including the company specific “hidden” costs per Exhibit

3. 

The significant benefit differences are the reduction in 

natural gas loss by eliminating venting and the inert purge

gas used in the shutdown interconnect procedure. As 

summarized in Exhibit 7, annual natural gas savings total 

24,440 Mcf for the hypothetical hot tapping scenario,

worth $171,080 per year at $7 per Mcf gas price. The 

annual inert gas savings of 1,710 Mcf is worth $13,680 per

year at $8 per Mcf of nitrogen, for a total annual benefit of 

$184,760. Additional benefits from avoiding gas leakage 

through pipeline block valves during shutdown 

interconnect would further improve the hot tapping 

economics. 

When assessing options for making new pipeline

connections, natural gas price may influence the decision

making process. Exhibit 9 shows an economic analysis of 

the 320 new connections using hot taps scenario at

different natural gas prices. 

$3/Mcf $5/Mcf $7/Mcf $8/Mcf $10/Mcf 

Value of Gas 

Saved $73,320 $122,200 $171,080 $195,520 $244,400 

Payback 

(months) 23 8 5 4 3 

Internal Rate 

of Return 

(IRR) 

44% 154% 258% 310% 413% 

Net Present 

Value 

(i=10%) 

$46,520 $231,814 $417,107 $509,755 $695,048 

Exhibit 9: Gas Price Impact 

on Economic Analysis 

In conclusion, hot tapping has been found to be more cost

effective than shutdown interconnects. Even when the 

system must be taken out of service, hot tapping presents 

opportunities for both time and cost savings. While hot 

tapping is a practice that has historically been performed 

by companies for reasons other than the gas savings, 

consideration of the methane reduction benefits can often 

serve to justify hot tapping over the shutdown interconnect 

procedure in a variety of circumstances. 

Case Study: One Vendor’s Experience 

A vendor reports that, for a gas transmission client, one 

day of gas service in a 36” natural gas pipeline

operating at 1,000 psig is worth $365,000 in gross 

revenue. It would take approximately 4 days to 

perform a shut down connection at a cost of $1.5 

million, not including the cost of venting the pipeline

contents in order to perform the tie-in with shutdown. 

A hot tap connection would eliminate this loss of 

revenue by enabling uninterrupted service. 

Lessons Learned 

Pipelines typically undergo several transformations each 

year. Performing hot taps to make these connections and 

installations can reduce methane emissions from pipelines 

and increase savings and efficiency. The following are 

several lessons learned offered by Partners and hot tap 

vendors: 

Hot tapping has been performed by transmission and 

distribution companies for decades. By evaluating 

the gas savings associated with this practice, hot

tapping can be used in many situations where it 

would not ordinarily have been used. 

The site for the branch weld must be free of general 

corrosion, stress corrosion cracking, and laminations. 

Hot tap should not be performed immediately 

upstream of rotating equipment or automatic control 

valves, unless such equipment is protected from the 

cuttings by filters or traps. 

For tapping on steel pipes, fittings generally consist 

of a welded branch connection. However, when 

tapping into cast iron, asbestos cement, or concrete, 

the fitting cannot be welded onto the existing header.

Alternative fitting attachment techniques, such as a 

split cast iron compression sleeve or a mechanical 

joint saddle, must be employed. 

For plastic systems, the operator should ensure that 

the hot tapping fittings are compatible with the type 

of plastic pipe in the system and appropriate joining 

methods are used. Vendors can supply suitable

fittings and tools for almost every kind of plastic 

system. 

If hot tapping has not been performed in the past, a 

9 
Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

hot tapping procedure should be developed and 

personnel trained. Be sure to include instructions 

concerning possible burn through or hydrogen 

cracking during welding. 

All equipment must meet minimum industry and 

federal standards for pressure, temperature, and 

operating requirements. 

If conditions of temperature, pressure, pipe

composition, or tap diameter are encountered that 

are unusual for your system, be sure to consult the 

manufacturer of the tapping equipment or fittings. 

Industry and federal codes and standards should be 

consulted for more specific specifications (e.g., ASME

B31.8, API 2201, API 1104, API D12750, 49 CFR 

192). 

Record emissions reductions associated with using 

hot taps and submit them with your Natural Gas 

STAR Annual Report. 

References 

American Petroleum Institute. Procedures for Welding or Hot Tapping on 

Equipment in Service. API Recommended Practice 2201, Third and 

Fourth Editions, October 1985 and September 1995. 

American Petroleum Institute. Welding of Pipelines and Related Facilities, 

Publication No. 1104, 19th Edition, September 1999. 

American Society of Mechanical Engineers (ASME). ASME Code for 

Pressure Piping, B3I, ASME B31.8-1995 Edition. 

Bruce, William A. Edison Welding Institute. Personal contact. 

Burns, David. TransCanada Hot Taps. Personal contact. 

Chaput, James. Michigan Gas. Personal contact. 

Chila, Vern. International Piping Services Company. Personal contact. 

Davaney, Tom. Con Edison. Personal contact. 

Doig, Deanna. TransCanada Alberta System, TransCanada Pipelines. 

Personal contact. 

Hranicka, Anthony. Con Edison. Personal contact. 

Hydra-Stop, Inc. A Pressure Installation Primer: Basic Information and 

Procedures for Line Tapping and Linestopping. 

LaShoto, Paul. Bay State Gas. Personal contact. 

McAllister, E.W. Editor. Pipeline Rules of Thumb Handbook. Fourth Edition, 

Gulf Publishing Company. 

McElligott, John A., John Delanty, and Burke Delanty, “Use of Hot Taps for 

Gas Pipelines Can be Expanded,” Oil and Gas Journal, 11/30/98. 

McMicken, Mike and Brian Boucher. Team Industrial Services, Inc. 

Personal contact. 

Petolick, Don and Gary Vanderhye. Hydra-Stop, Inc. Personal contact. 

Rodgers, Erick. Topaz Inc. Personal contact. 

Smith, Sharlye. Mueller Co. Personal contact. 

Vandervort, Dal and T.D. Williamson. Inc. Personal contact. 

Venugopal, Shrikanth. TransCanada Transmission. Personal contact. 

Tingley, Kevin. EPA Natural Gas STAR Program. Personal contact. 

U.S. Code of Federal Regulations. Title 49, Part 192 (49 CFR 192), 

Subpart D, “Transportation of Natural and Other Gas by Pipeline: 

Minimum Federal Safety Standards; Design of Pipeline Components”. 

10 
 

 

Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

Appendix: Supplemental Information 

Valves. Valves used in hot tapping are typically full

opening ball or wedge gate valves. Pipe suppliers can 

usually supply prices for valves and fittings, if provided

with the scenario information including pipe size, outlet

size, and line content, pressure, and material. 

Tees/Fittings. There are several different types of 

mechanical and welded fittings applicable to hot tapping 

including weldolet, threadolet, scarfed nipple, tapping tee,

or full encirclement saddle. The most common tapping

fitting is a split cast iron sleeve. Fittings are typically

priced by size, flange (ANSI/pressure) rating, and any 

special characteristics. Typical vendor fitting costs are 

presented below. 

One of the possible hidden costs of a shutdown connection,

if gas cannot be supplied from alternate sources, can be the 

cost of relighting customers. This process would require 

two visits, one to shut down and the second to turn on and 

relight. Typically, a visit to a residential customer would 

take 15 to 30 minutes, and a visit to a commercial or 

industrial customer would take approximately 1 hour. 

According to the Bureau of Labor Statistics, an employee 

would be paid approximately $9.75 per hour for this work. 

Topaz - Full Encirclement Saddle Costs ($) 

Size (pipeline x outlet) Part 1 Part 2 

2” x 2” $227 $189 

4” x 4” $227 $189 

12” x 12” $645 $539 

20” x 20” N/A $1,306 

12” x 4” $594 $495 

20” x 8” $1,303 $1,076 

40” x 16” N/A $3,493 

Fittings are available for other sizes. 

TD Williamson - Full Split Tee Costs ($) 

Size (pipeline x outlet) 

16” x 16” $2,000 

18” x 18” $3,000 

20” x 20” $5,000 

24” x 24” $6,000 

30” x 30” $9,000 

40” x 16” $2,500 

60” x 16” $2,500 

Price estimates are for a 300# rating. 

Fittings are also available for 150#, 400#, 600#, 900#, and 1,500# flange ratings and sizes 1” x 1” to 

96” x 96”. 

Cost of Relighting = [(No. of residential customers) * (0.38 

hrs)] + [(No. of commercial/industrial customers) * (1 hr)] * 

$9.75/hr 

It might not be possible to perform a shutdown connection 

during optimal hours. Scheduling and additional planning

might have to be completed to arrange the construction 

and additional excavation necessary to shut down the line, 

pay employees overtime, and advertise the shutdown to

customers. These costs are variable and will depend on the

company and internal factors. 

Other additional costs exist, such as scheduling, labor,

overtime, and advertising, but are unique to each 

company, and beyond the scope of this study. These costs 

can be estimated based on past shutdown experience. An

operator should examine past records to determine what, if 

any, costs are being avoided by performing a hot tap

versus a shutdown connection. 

Topaz - Tapping Tee Costs ($) 

Size (pipeline 

x outlet) 

150# Flange 

Rating 

300# Flange 

Rating 

600# Flange 

Rating 

2” x 2” $386 $399 $443 

4” x 4” $407 $428 $481 

12” x 12” $1,394 $1,484 $1,624 

20” x 20” $3,645 $3,857 $4,290 

12” x 4” $1,248 $1,251 $1,347 

20” x 8” $1,428 $1,468 $1,521 

Fittings are available for other sizes. 

11 
Using Hot Taps For In Service Pipeline Connections 

(Cont’d) 

United States 

Environmental Protection Agency 

Air and Radiation (6202J) 

1200 Pennsylvania Ave., NW 

Washington, DC 20460 

October 2006 

EPA provides the suggested methane emissions estimating methods contained in this document as a tool to develop basic methane emissions estimates only. As 

regulatory reporting demands a higher-level of accuracy, the methane emission estimating methods and terminology contained in this document may not conform to 

the Greenhouse Gas Reporting Rule, 40 CFR Part 98, Subpart W methods or those in other EPA regulations. 

12