Flowline
Pressure relief valves
A relief valve is the last line of defense against overpressure on a pump line: when pressure passes its set point, it opens to a bleed-off line and protects the iron, the pumps and the crew.
A pressure relief valve, often called a pop-off valve, protects a pump discharge line from overpressure: a spring holds the valve shut until line pressure exceeds the set point, then the valve opens and vents flow to a bleed-off line until pressure falls. We supply spring-set relief valves in 2 and 3 in with hammer union inlets for frac, cementing and well service lines, each set and tested to the pressure on your order.
Where relief valves go
A relief valve is fitted on the discharge side of each pump or on the treating line, between the pump and the first valve that could be closed against it. It protects iron rated, for example, 15,000 psi from a pump that can exceed that if a valve is shut or a line plugs with sand. The outlet runs through an anchored bleed-off line to a tank or pit.
Types of relief valve
| Type | How it works |
|---|---|
| Spring-set | A spring preloaded to the set pressure holds the valve shut; it reseats when pressure falls |
| Reset | Opens at the set point and stays open until it is reset by hand |
| Electronic or remote set | Set point and opening controlled from the data van |
We supply spring-set relief valves, the simplest of the three and the easiest to test and rebuild between jobs.
Set pressure and testing
The set pressure comes from your pressure control plan: below the rated working pressure of the weakest part of the line, above the highest treating pressure, with margin for spikes. Each valve is shell tested, then set and tested on a test stand to that pressure, and the set pressure is recorded on the test certificate and marked on the valve. Spring-set valves should be retested on the schedule your procedure sets and after every lift.
Run the outlet to a tank or pit through an anchored line at least as large as the valve outlet, with no valve in it that could be left shut. A relief valve that vents to open air near people is a hazard of its own.
Material and service
Bodies are forged alloy steel, heat treated for the rating; internals are hardened against the erosion of a high-velocity release. For hydrogen sulfide service, materials are chosen within the limits of NACE MR0175 / ISO 15156. Each valve is stamped with size, inlet figure, rating, set pressure and heat number.
We make these parts to the API 6A requirements your order calls up: material, dimensions, tests and marking as specified. We do not hold an API license, so the parts do not carry the API Monogram. If your specification requires monogrammed equipment, the quotation says so plainly.
Ordering
Pressure relief valve, spring-set, 2 in FIG 1502 female inlet, 2 in FIG 1502 male outlet, body rated 15,000 psi CWP, set pressure 13,500 psi, shell tested and set tested, EN 10204 3.1, 4 pcs
Frequently asked questions
What set pressure should a pump line relief valve have?
Below the rated working pressure of the weakest part of the line it protects, and above the highest pressure the job is designed to pump, with margin for pressure spikes. The set point belongs to your pressure control plan; tell us the value and we set and test the valve to it.
Where does the relief valve discharge?
Into a bleed-off line run to a tank or pit and anchored, never to open air near people. The discharge line should be at least the size of the valve outlet and free of valves that could be left shut.
How often should a relief valve be tested?
On the schedule your procedure sets, and after any event that made it lift. A set pressure check on a test stand shows whether the spring has relaxed or the seat has worn.
Do you supply electronic or remote-set relief valves?
No. We supply spring-set mechanical relief valves. Electronically controlled relief valves come from specialist makers.