Pilot Operated

Pressure Relief Valves

(POPRV)
October 2020 Chief Inspectors Meeting
Prepared by: J. F. Ball

1
 Objectives

• Definition/ Manufacturers
• Basic Operation
• Flowing Pilot vs Non-Flowing Pilot
• Snap / Pop Action Pilot
• Modulating Pilot
• ASME Code Status
• Applications
• Features/Benefits (and Concerns)
• Code Updates
• Options
2
 Definition
(PTC-25)

• pilot-operated PRV: a pressure relief valve in

which the disk is held closed by system
pressure, and the holding pressure is
controlled by a pilot valve actuated by system
pressure.

3
 Manufacturers

Anderson Greenwood
Dresser
Farris
Target Rock (nuclear)
Mercer
Taylor Valve
Leser
Apparecchi
Weir Power

4
 Early Pilot Valve Usage

5
 Basic Operation

Pilot

The Pilot controls the Main

Valve action of:
- Opening Pressure
- Closing Pressure
Main Valve
- Style Of Action

6
 Basic Operation

Dome

Piston Seal

Seat

Piston
Below set pressure, force imbalance due to differential area
keeps main valve closed
7
 Basic Operation

PD
PD = ≤0.70P1

P1

Above set pressure with Main Valve open

8
 Standard Main Valve
(AG Valve Series 200, 400, 500 and 800)

Tube Fitting
Cap Cap Bolt

Dome Spring
Piston
Seal
Lock Pin

Piston Liner

Retainer Seat Retainer

Screw
Seat
Nozzle

Retainer
Body

Tube Fitting

Nozzle Seal
Red Indicates Leak Path
Pilot Tube
9
 Flowing vs. Non-Flowing Pilot

Flowing Pilot –
When the main
valve is open and
flowing, there is
system fluid
flowing through
the pilot.

Non-Flowing Pilot –
When the main valve is
open, there is no
system fluid flowing
through the pilot.
10
 Main Valve Action Based on Pilot Style
100% Lift
3%

Main Valve Piston Lift

Minimum
Pop Blowdown

Main Valve Fully

Open at Set
Pressure
Set
Pressure
100% Lift

Main Valve Piston Lift

Modulating
Main Valve Opens
According
to Relief Demand
Pressure
11
 Pop Action Pilot (Series 200)

• Pop Action Pilot (snap action)

• Gas or Mixed Phase Service
• Non flowing pilot design
(no hydrates formed)

Hydrates are solids that

contain water.

12
 Series 200
(Normally Closed Position)

Pilot
Dome Set Pressure
Pilot Adjustment
Discharge
Dome
Relief Seat

Blowdown
Seat

System

Blowdown
Adjustment

13
 Series 200
(Relieving Position)

Dome

0%

100% of
set
System

14
 Series 200
(Re-Closed Position)

Blowdown
Pressure
Dome
Relief Seat

Blowdown
Seat

Blowdown Pressure
System

Blowdown
Adjustment

15
 Series 200 POPRV (Pop Pilot)

Main Valve Dome Approximate

Volume Discharged Operating Time to
Through Vent Full Lift for Gas

Examples: 1F2, 0.0005 ft3 Examples: 1F2, 0.14 second

2J3, 0.0019 ft3 2J3, 0.19 second
4P6, 0.0145 ft3 4P6, 0.47 second
6R8, 0.0543 ft3 6R8, 0.77 second
8T10, 0.0973 ft3 8T10, 1.13 second

Less than 1/2 a shot

16
 Series 200 POPRV

3% Minimum
Down Force On Main Valve Piston

Blowdown
100% Lift

Main Valve Piston Lift

Opening
Closing
0 Set 0 Set
Pressure Pressure

17
 Series 200 POPRV
• Pop Action with Full Lift at Set Pressure
• For Gas and Mixed Phase Services
(Up to 1/3 Liquid by Volume)
• Set Pressures 25 to 10,000 psig [1.72 To 690 barg]
• Temperatures -423 to 550ºF [-252 to 287ºC]
• Main Valve Tight to Set Pressure
• Minimum Pilot Cracking Pressure:
100 psig [6.90 barg] and Above: 95% Of Set
Below 100 psig [6.90 barg]: 90% Of Set
• Range of Blowdown Adjustment: 3 To 15% Of Set Pressure
(Below 5% Only with Remote Sensing)
• Pilot Must Vent to Atmospheric Pressure
(Bug Screen or Tube to a Sump)
18
 Series 200 POPRV Benefits

• Allows Higher System Operating Pressure for Maximized

Process Output
• Non-Flowing Pilot Design Minimizes Flow Through the Pilot and
Ingress of Particulates
• Minimum Pilot Venting — Only the Main Valve Dome Volume
Example: 2J3 = 0.0019 ft3 [0.00005 m3]
• No Emissions While Valve Closed
• Safe, Externally Adjustable Blowdown
• Set Pressure and Lift Unaffected by Back Pressure
• Protection Against Resonant Chatter

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 Modulating Pilot (Series 400)

• Modulating Action
• Gas, Liquid, or Mixed Phase
• Non flowing pilot design

20
 Series 400 Pilots

Diaphragm Style
15 to 740 psig [1.03 To 51.03 barg]
(Check mfg. specifications)

Pressure
Sense
Diaphragm
Pressure
Sense
Piston Piston Style
100 to 1480 psig
[6.90 to 102 barg]
21
 Series 400 Pilots Advantages

Diaphragm Style Piston Style

Best Sensitivity More Rugged

Best Repeatability Better Able to

Tolerate Pressure
Pulsations and
Higher Pressures

Wider Selection
of Soft Goods

22
 Series 400 POSRV
(Normally Closed Position)

Set Pressure Inlet Seat

Adjustment

Sense Diaphragm Spool

Dome

Outlet Seat
Pilot Discharge Tubed
To Main Valve Outlet
Feedback Piston Balancing Seal
23
 Series 400 POSRV
(At or Slightly Above Set Pressure, Main Valve Modulating)

24
 Series 400 POPRV
(Above Set Pressure and at Full Lift)

25
 Series 400 POPRV
Down Force On Main Valve Piston

95% Set Pressure, 100% Lift

Minimum

Main Valve Piston Lift

≈ 93%

"Null"
Position

0 Set 0 Set
Pressure Pressure

26
 Series 400 POPRV

• Modulating Action, with the Main Valve Opening according to the

Relief Demand. Opens Only Enough to Keep the System at Set
Pressure - - - Similar to Back Pressure Regulator
• Consistent Operation Regardless of Process Phase State
• Set Pressures 15 to 1480 psig [1.03 To 102.1 barg]
• Temperatures -65 to 550ºF [-54 To 286ºC]
• Main Valve Tight to Set Pressure
• Minimum Pilot Cracking Pressure: 95% of Set
• Pilot Is Balanced Against Back Pressure. The Discharge Is Connected
to Main Valve Outlet as Standard
• Set Pressure and Lift Unaffected by Back Pressure

27
 Series 400 POPRV Benefits

• Less Wasted/Lost Product (+ $)

• No Emissions
• Minimized Releases and Pollution
• Less Noise
• Greater System Output by Being Able to Operate Nearer to Set
Pressure
• Set Pressure and Lift Unaffected by Back Pressure
• No PRV Chatter Due to Poor Inlet Piping
(Caution: Check valve capacity using flowing pressure)

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 Code Status

• Capacity certified
and available with
ASME Code
Designator for
Sections I, III, and
VIII.
• Certified fluids
include steam,
air/gas and
liquid.

29
 Code Status

• Two nameplates required

– one on pilot and one on
main valve with ASME
symbol
• Dual fluid certification
available for Section I
economizers using Code
Case 2446 (steam and
water)
• Pilot sensing line to be
protected from freezing
(PG-73.2.12)

30
 Code Status

• Initial capacity
tests may be done
using the main
valve only, along
with operational
tests to prove
function and lift

31
 Testing of Pilots

Dome Pressure Gauge

Pilot

Supply (System Pressure

Gauge)
Pilot Supply

Metering Valve

Nitrogen Or TD-1 Test Drum

Air Supply

Vent Valve

32
 Applications Considerations
There are several things you have to consider when
selecting a pilot operated relief valve:

Type of service:
Air, gas, vapor, liquid, steam, etc.

Temperature:
-420°F to 500°F (depending on type of pilot).

Set Pressure:
Low Pressure: inches of water to 50 psig,
diaphragm type main valve.
High Pressure: 20 psig to 6000 psig,
piston type main valve.

Compatibility
Elastomers, plastic seat, seals.

Available for NACE service

33
 Features/Benefits

1. Price: less expensive in larger valves

2 Size: 8″ x 10″ POPRV 32″ to 36″ tall

Spring Loaded PRV is 60” tall

3. Can be used dirty or wet service

4. Balanced for back pressure

5. Bubble tight up to 95% of set pressure

34
 Features/Benefits

6. Easy adjustment of set pressure and blowdown (reseat)

adjustment

7. Reduced maintenance costs, no lapping or machining

of parts (pilot can be replaced as a part)

8. Remote pressure pickup

9. Manual or remote blowdown

10. Field test connection

11. Pilot lift lever available

35
 POPRV
Options

36
 Field Test Connection
(Series 200 POSV)

37
 Field Test Procedure
(Series 200)

Block Valve "B"

Flexible Hose
Test Gauge
Field Test
Connection

Vent Valve "C"

Block Valve
"A"

N2

Gas Bottle

38
 Field Test Connection and Indicator
(Series 400 POSV)

Pilot Body

Plunger Seal

System
Pressure

Plunger Seat
Shuttle Seats
39
 Field Test Procedure
(Series 400 POSRV)

Field Test Connection

Gas Vent Flexible Hose

Test Gauge

Block Valve "A"

N2 Gas Bottle

Vent Valve "C"

40
 Back Pressure on POPRV

P1

AP
P2
AS
Piston

P2 P2

P1

41
 Series 200 POPRV
with Backflow Preventer
Pilot

Backflow
Preventer

P2 > P1 P2

Process Pressure

P1 Discharge Pressure
42
 Backflow Preventer
(Can Be Field Retrofitted)

43
 For Dirty Service

Auxiliary Filter
In Pilot Supply

44
 Pilot Supply Filter

In (From Pilot Tube Or

Remote Sense)

Out Element
(To Pilot Inlet) (11 in2) [71 cm2]
316 S.S.
53 Micron

45
 Remote Pressure Sensing Option for Dirty Service
and/or Excessive Inlet Losses
STANDARD
OPTIONAL

Integral
Pressure
Sensing
Remote
Pressure
Sensing

46
 Iso-Dome Series 400 POSRV
Set Pressure
Adjustment

Sense
Diaphragm

Regulator
(Supplied by AG/C,
Clean Gas Set, Sealed and
Mounted on PRV)
Supply Process Clean Gas
By Customer
47
 Pressure Spike Snubber
for Gas Service

48
 Positive Displacement Compressor
(PRV Relieves “Low”)

Set

Operating Gauge
Pressure Reading
Pressure

Pressure Pulsations
that the PRV Reacts to

49 Time
 AG/C POPRV
with Pressure Spike Snubber

Set
Pressure

Pressure at Pilot Inlet

Pressure at Main Valve Seat

Time

Pressure Spike
Snubber
50
 Pressure Spike Snubber

Outlet to
Series 200,
400, or 800 Pilot

Maximum Pressure
3705 psig [255.5 barg]

143 Micron, 316 S.S.

Filter

Inlet

51
 Packed Lift Lever

REF:
UG136 (A) (3)

52
 Manual Blowdown Valve

53
 Remote Unloader

Remotely
Actuated
Pneumatic
or
Solenoid Valve
(NC or NO)

Main Valve

54
Low Pressure
Variations:
Series 90 Pilot

55
Low Pressure
Variations:
Series 93

56
 Code Update
for 21 addenda

• Being added - UG-129(a)(9)

The pilot and main valve of a pilot operated
pressure relief valve shall each be marked with
the same unique identifier to establish
association of both components.
• Work on remote mounted pilots is ongoing

57
Thanks – questions?

Pictures courtesy of:

Anderson Greenwood
Consolidated Valve

58