The difference between a pressure regulator and pressure relief valve

What is the difference between a pressure regulator and a pressure relief valve? In this
blog, Fluid Controls outlines the purpose of each valve to help you decide whether
you need a pressure regulator or pressure relief valve for your application.

What is a pressure regulator?

A pressure regulator works to control the pressure within an application. By adapting

the inlet pressure levels, it maintains a steady outlet pressure. The regulator is reactive
to the pressure of the liquid or gas and alters as necessary.

What is a pressure relief valve?

The purpose of a pressure relief valve is simply to relieve the pressure levels in a
system when they reach a certain set point. The valve opens to ease the building
pressure by allowing it to escape, then the valve closes when it has returned to a stable
level. The main function of a pressure relief valve is to act as a safety device on a
system, to prevent accidents by opening and providing a point of release. Pressure
relief valves are often found on domestic boilers. Read our article to find out more
about boiler pressure relief valves.

The difference between a pressure regulator and pressure relief valve

The difference between a pressure regulator and a pressure relief valve is that relief
valve is a safety feature, used as a last stop measure to prevent any accidents.
Whereas, a pressure regular works within the system to maintain a steady pressure
level the entire time.

Taking this into consideration, there is still a similarity between them, as they both
work as a means of controlling the pressure levels. The regulator is a function
working continually to keep the pressure controlled, whilst the relief valve comes into
play when the pressure needs to be stabilised and pulled back to a normal level.
Pressure relief valves and pressure regulators from Fluid Controls

At Fluid Controls, we have a wide selection of pressure regulators available for an

array of applications. Whether you are looking for a filter, back pressure or
instrumentation regulator, our comprehensive range will cover it. For pressure relief
valves, we stock the Parker HPRV series relief valve, for its wide pressure range and
precision.

For guidance on whether you need a pressure regulator or pressure relief valve for
your application, talk to the team at Fluid Controls today. Call us on 0118 970 2060 or
email us at fluid@fluidcontrols.co.uk and we can help you understand the difference
between a pressure regulator and pressure relief valve.

Ref: ( Pressure regulator or pressure relief valve? (fluidcontrols.co.uk) )

Fire Pump Pressure Relief Valve - NFPA 20 Compliance - BERMAD

By
Wagner Ramiro
28 Nov 2017
Last updated: 31 May 2022
Water is the most efficient, cheapest and most readily available medium for
extinguishing fires of a general nature. It is used by the Fire Service in one form or
another in the majority of fire protection situations.

For fire water to do its job successfully, it must be supplied 

with the necessary pressure and flow. For this, a fire pump is required most of the
time. Many systems also call for pressure regulating equipment, including Pressure
Relief Valves and Pressure Control Valves. Standards such as NPFA 20 include
requirements concerning pumps and other pressure-related fire protection equipment.
Designing a fire protection system with Pressure Relief and Control Valves requires a
great deal of expertise. It is critical for designers to maintain rigid adherence to
stringent fire protection guidelines and regulations (including NFPA, government and
insurance requirements), in order to avoid mistakes such as using a relief valve to
control pressure in a fire protection header.
Let’s take a closer look at specific NFPA guidelines for these fire water pressure
regulation valves.

NFPA 20 Compliance for Pressure Relief Valves (PRV)

A Pressure Relief Valve is defined by NFPA 20 (3.3.67.5 Relief Valve) as “A device
that allows the diversion of liquid to limit excess pressure in a system.”
In general, a PRV is a safety device, designed to protect a pressurized system during
an overpressured event. An overpressured event refers to any condition which would
cause pressure in a system to increase beyond the specified design pressure or
maximum allowable working pressure. Since Pressure Relief Valves are safety
devices, there are many codes and standards written to control their design and
application.
For Centrifugal Pumps, the NFPA 20 (4.19.1.2) requires that “a Pressure Relief Valve
shall be installed. where a diesel engine fire pump is installed and where a total of 121
percent of the net rated shutoff (churn) pressure plus the maximum static suction
pressure, adjusted for elevation, exceeds the pressure for which the system
components are rated.”
A Pressure Relief Valve is required by the standard to be installed when the diesel
engine is turning faster than normal, because the pressure is proportional to the square
of the speed that the pump is turned. This is a relatively rare event; if pumps create
pressures less than the pressure rating of the fire protection system components
[typically 175 psi (12.1 bar)] at 110 percent of rated speed, a Pressure Relief Valve is
not required.
Figure 01 – Diesel Fire Pump 
 Figure 02 – Pressure Relief Valve from BERMAD

The standard specifically does not permit the use of a main pressure relief valve on an
electric fire pump, except where a variable speed driver is used. Variable speed
drivers are required to default to constant rated speed operation. In the event the
variable speed driver fails, the rated speed can result in system over-pressurization. In
this case a pressure relief valve is required.
When designing a fire pump, it is highly important that the designer match the pump
to the system demands, in order to avoid overpressurizing the system and then using
pressure regulating devices to compensate.
NFPA 20 Compliance for Pressure Control Valves (PCV)
Another important piece of equipment aimed to guarantee sufficient flow and pressure
water during a fire event is the Pressure Control Valve (PCV).
A Pressure Control Valve is defined by the NFPA 20 (3.3.67.3) [14,2013] as “a pilot-
operated pressure-reducing valve designed for the purpose of reducing the
downstream water pressure to a specific value under both flowing (residual) and non-
flowing (static) conditions.“
Suction Pressure Regulating Valves that are listed for fire pump service are permitted
for use in cases where the authority requires positive pressure to be maintained on the
suction piping. These valves should be installed according to manufacturers’
recommendations in the piping between the pump and the discharge check valve.

Other Fire Protection Compliance Standards for Pressure Regulating Valves

Other pressure control devices, including PCVs installed downstream of the discharge
isolation valve, are beyond the scope of NFPA 20. When permitted by the fire
protection authority, they should be installed in accordance with the appropriate
listing and installation standard, such as NFPA 13 or NFPA 14.
NFPA 14 specifies the condition for using pressure regulating valves, and defines the
maximum pressure at hose connection due to the different pressure limitations
established. Where the static pressure at a 2½ in. (65 mm) hose connection exceeds
175 psi (12.1 bar), an approved pressure-regulating device shall be provided, to limit
static and residual pressures at the outlet of the hose connection to 175 psi (12.1 bar)
(7.2.3.2*). It may be necessary to arrange piping so that separate pressure-regulating
devices can be provided on Class I and Class II hose connections.
The figure below demonstrates compliance with all requirements:
Need Fire Protection Design Assistance?
BERMAD engineers are available to provide you with expert guidance in fire
protection applications and systems. To learn more, click here to contact a BERMAD
representative in your region.
Ref: ( Fire Pump Pressure Relief Valve - NFPA 20 Compliance - BERMAD )