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Test Pressure, and Working Pressure Tests, Explained

 

API Spec 6A and 16A require manufacturers to conduct hydrostatic body tests of individual units of pressure containing and/or controlling equipment. This simply means that all equipment units that have designs which include a “body” portion with end connectors (perhaps with outlets and bonnet attachment points) shall experience a hydrostatic test to a specified pressure, for a specified hold period, for a specified number of cycles, at the time of original manufacture.

Passing this test requires the equipment retain the specified pressure for the specified time (hold period) and the specified number of cycles without pressure release or visible leakage.

Caution: Never confuse “Test Pressure” with “Working Pressure” (working pressure and rated pressure mean the same thing). Do not apply test pressure to any closure parts within equipment units, e.g. BOP rams, valve gates, choke needles and seats. Hydrostatic pressure applied to these closure parts should never exceed the equipment rated working pressure.

The following table provides a guide to test pressures for API Spec 6A and 16A equipment with specific working pressure ratings.

Table 1

Working Pressure Rating

Test Pressures for Equipment with Specific
End and Outlet Connections *

Nominal Size Flange

Line Pipe and Tubing Threads

Casing Threads
13-5/8"
and smaller		 16-3/4"
and larger		 4-1/2" to 10-3/4" 11-3/4" to 13-3/8" 16" to 20"

psi

 psi psi

psi

 psi psi psi

2,000

 4,000** 3,000 4,000 4,000 4,000 2,250

3,000

 6,000** 4,500 6,000 6,000 4,500 -

5,000

 7,500 7,500 7,500 7,500 - -

10,000

 15,000 15,000 15,000 - - -

15,000

 22,500 22,500 - - - -

20,000

 30,000 - - - - -

* The rated working pressure of any piece of pressure control equipment never exceeds the rating of its lowest pressure connector (except for cross-over connectors and chokes, see API Spec 6A for special instructions for these units of equipment).

** API Spec 16A specifies all test pressures for all sizes of equipment as 1.5 times working pressure including smaller sizes of 2000 psi and 3000 psi working pressure equipment. For information about the specific requirements for testing API Spec 16A clamps, Click Here.

Apply test pressure two times. The first application of pressure shall continue for a minimum of 3 minutes. The second application of pressure shall also continue for 3 minutes minimum, or for API Spec 6A, PSL 3 and PSL 4, and API Spec 16A equipment, the second test shall continue for a minimum of 15 minutes. For acceptance, equipment shall show no visible leakage under test pressure.

Exception: Leakage by the thread during the hydrostatic testing of a threaded wellhead member, when joined to a threaded test fixture, shall not void the test so long as the leak initiated above the rated working pressure of the thread and allowed the maintenance of the required pressure for the required hold period. See Table 2 below for the working pressure rating for API Internal threaded end or outlet connections.

The table below provides the working pressure rating for Internal threaded end and outlet connections on API Spec 6A equipment.

Table 2

Working pressure ratings for Internal threaded end or outlet connections *

Type of thread

Nominal pipe size
(inch)

Rated working pressure
(psi)
Line-pipe/NPT
(nominal sizes)		 1/2 10,000
3/4 to 2 5,000
2-1/2 to 6 3,000
Tubing
non-upset, and external upset round thread		 1.050 to 4-1/2 5,000
Casing
(8 round, buttress, and extreme line)		 4-1/2 to 10-3/4 5,000
11-3/4 to 13-3/8 3,000
16 to 20 2,000
*

See the text as part of Table 1 above to evaluate any leakage observed when testing these threaded connections to pressures higher than their working pressure ratings.

Test pressure requirements assure that the body of an equipment unit, with any connection thereon, has the capacity to hold and retain fluid at the rated working pressure, with a margin of safety.

Tests of equipment closure parts equal to rated working pressure demonstrate the functional reliability of the equipment to operate and control the flow, or stop the flow, of fluids passing through the equipment at pressures equal to or less than the rated working pressure.

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