Groth 1401E User Manual

Installation, Operation and Maintenance Manual for 1401E

PILOT VALVE	IOM 1401E.1	ISO 9001
	MAY 2006
	Groth Corporation 2006

IOM 1401E.1 REV. A 12541

TABLE OF CONTENTS

GENERAL INFORMATION
Pilot Valve Design and Function		2-3
SAFETY
General Instructions		3-4
INSTALLATION
Inspection and Installation		4
OPERATION AND MAINTENANCE
Modes of Operations		4-6
Equipment Options Operation		6-7
Troubleshooting Guide		8
Recommended Spare Parts		8
Maintenance		8
Disassembly		9
Assembly		9-10
Recommended Testing & Setting Procedure		11
Bill of Material		12
Model Identification		15
Product Limited Warranty		15
LIST OF FIGURES
1.	Tank Installation - Safety Equipment	2
2.	Pilot Valve Function-Shut off Condition	2
3.	Operation - Closed Position	5
4.	Operation - Open, Snap Action	5
5.	Operation - Open Modulating	5
6.	Operation - Reseat, Snap Action	6
7.	Operation - Reseat Modulation	6
8.	Options - Vent Piped to Discharge
	Header	6
9.	Options - Field Test Connection	7
10. Options - Manual/Remote Blowdown		7
11. Body Sub - Assembly		9
12. Stem Sub - Assembly		10
13. Test Apparatus		11
14. Exploded Assembly		13
15. Cross Sectional Assembly		14
LIST OF TABLES
1.	Pilot Valve Specifications	3
2.	Spring Table	5
3.	Recommended Spare Parts	8
4.	Recommended Bolt Torque	9
5.	Setting Specifications - Pilot Valve	11

INTRODUCTION

Pressure and/or vacuum relief valves are used on liquid storage tanks and other process vessels or systems to prevent structural damage due to excess internal pressure or vacuum.

Storage tanks are pressurized when liquid is pumped in, compressing the existing vapor or when increasing temperature causes increased evaporation or expansion of existing vapor. Conversely, vacuum may be created when pumping out or decreasing temperature. To prevent damage, vapor must be allowed to escape or enter the tank at a specified pressure or vacuum. The volume rate of venting depends upon the tank size, volatility of the contents, the pumping rate and the temperature. See API Standard 2000 for the procedure for determining venting requirements.

The pilot operated relief valve has two principal advantages over other types of relief valves:

1). It is bubble tight at 10% below set pressure. 2). It is fully open at 10% above set pressure.

These characteristics permit operating pressures nearer to the maximum allowable working pressure of the tank. High operating pressures reduce evaporation and total venting volume, thereby reducing product loss and cost of processing emissions. A tank may also have provisions for emergency pressure relief due to fire exposure and/or inert gas blanketing of the vapor space. A typical tank installation is shown in Figure 1 which includes a pilot operated pressure/vacuum relief valve, a gas blanketing regulator and an emergency pressure relief valve. The emergency valve may also be pilot operated. Groth Corporation manufactures all of these devices.

The pilot valve must be carefully maintained by a knowledgeable valve technician. It should only be assembled under clean conditions, preferably in a service shop environment. Carefully read and understand this manual before attempting to adjust set pressure or blowdown, or repair the pilot valve. Groth Corporation offers repair services for all products manufactured by The Tank Protection Division.

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Figure 1: Tank Installation - Safety Equipment

PILOT OPERATED
PRESSURE/VACUUM	BLANKET GAS REGULATOR
RELIEF VALVE
GROTH MODEL 1420	GROTH MODEL 3000
EMERGENCY RELIEF VALVE
GROTH MODEL 2400	BLANKET
GAUGE	GAS
	SUPPLY
	SENSE LINE

PILOT VALVE DESIGN AND FUNCTION

Note that throughout this manual, numbers in [ ] after the part descriptions are item numbers which refer to the drawings and bill of materials.

The function of the pilot valve is to control pressure to the actuator of a pressure relief valve. The pressure relief valve is designed so the effective area of the actuator (1) is significantly larger than the valve seat area (2). Therefore when tank pressure is applied to the actuator, the closing force is greater than the opening force so tight shut-off is achieved.

The pilot seat is held closed by the adjustable set pressure spring. Tank pressure is conveyed to the pilot valve by the pilot pickup tube (3), and directly applied to the booster diaphragm (4). Simultaneously pressure is applied through an adjustable orifice (6) to the space between the diaphragms and to the pressure relief valve actuator, closing the relief valve. The net force attempting to lift the pilot spool is the tank pressure acting on the effective area of the sense (smaller) diaphragm (5).

Fig. 2 Shut - Off Condition

5

4

		7
3	6	8

1

2

2

When the tank pressure reaches the set pressure of the pilot valve, force on the diaphragm overcomes the spring and vapors begin to flow to the atmosphere through the pilot seat (7) and exhaust port (8). As the actuator is evacuated to atmosphere, pressure is also reduced in the space between the diaphragms, and additional lifting force is provided by the booster (larger) diaphragm. The rate of evacuation of the actuator is controlled by the diameter of the adjustable orifice. As pressure on the actuator is relieved, tank pressure forces the relief valve seat (2) fully open.

As tank pressure decreases to the pilot valve setting, the valve closes and tank pressure again flows through the orifice to the relief valve actuator. As the actuator is filled, the pressure relief valve seat is forced closed. The size of the adjustable orifice determines the speed of filling the actuator.

The adjustable orifice, or "blowdown needle", affects both opening and closing of the pressure relief valve. Opening can be varied from rapid, "snap action", to incremental, "modulating". The pressure at which the valve closes, "blowdown pressure", can vary from set pressure to 7-10% below set pressure. These characteristics are discussed in detail in the operation section of this manual.

TABLE 1

PILOT VALVE SPECIFICATIONS

MODEL 1401E

Set pressure	2.0" WC to 15 PSIG
	5 to 1033 mbar (metric)
Blowdown	Zero to 10 %
Action	"Snap Action" to
	"Modulating"
Materials	Carbon Steel/SS Trim
	316 SS
Diaphragm	Fluoropolymer
Elastomers	Buna-N, FKM, FFKM

WARNING

The pilot valve will exhaust the actuator of the pressure relief valve as described in this manual. This function does NOT assure that the relief valve will open fully. The forces exerted by system pressure and vapor flow must be sufficient to support the weight of the pallet-support assembly to achieve full opening. Relief valves built with heavy components designed to withstand high pressure may NOT open at low pressure even though the actuator has been fully exhausted. Consult Groth Corporation or the specific relief valve operation

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manual when applying pilot operated pressure relief valves at low pressure settings.

Eight springs are used with the screw adjustment to obtain the required set pressure. For more detail see Table 2 on page 5.

This manual is intended to provide recommended procedures and practices for installation, operation, and maintenance of the Groth Series 1401E Pilot Valve. The pressure relief valve is covered by a separate manual. Any standard procedures and practices developed in a specific plant or process should supersede this manual. Although this manual cannot cover all possible contingencies, following these guidelines should provide safe, reliable pilot valve performance.

For information not contained in this manual, please contact:

Groth Corporation

13650 N. Promenade Blvd.

Stafford, Texas 77477 281-295-6800 (phone)

281-295-6995 (fax)

SAFETY GENERAL INSTRUCTIONS

This section is an overview of safety guidelines that should be followed during the installation, operation and maintenance of Groth series 1401 pilot valves. To understand the context of these instructions and warnings, read and understand this complete manual.

WARNING

The purpose of a pilot operated pressure relief valve is to prevent excessive pressure or vacuum in a tank or process system. The valve must be designed for the proper MAWP and flow requirements of the system. Consult API Standard 2000 for tank protection sizing procedures. An improperly specified or functioning relief valve may result in structural damage to the tank or system.

In the event of a diaphragm failure, the pilot valve will vent pressure to the atmosphere, causing the pressure relief valve to fail in the OPEN position. Pressure may be vented slowly, simulating the action of a modulating pilot. Under these conditions, somewhat greater overpressure may be required to produce the full flow capacity of the relief valve.

Pilot valve set pressure and blowdown are set at the factory per purchase specifications. The set pressure and range of adjustability are stamped on the nameplate. DO NOT attempt to readjust the set pressure beyond the limits specified on the nameplate and in Table 2.

The pilot sense line is 3/8" OD SS tubing. It must be kept open and unobstructed to ensure that the pilot "senses" actual tank pressure. For applications where tank vapors may condense or "polymerize" in the sense tube or pilot valve, a nitrogen purge may be required to prevent internal obstruction of the tube. Consult Groth Corporation for recommendations.

DO NOT attempt to remove the pilot valve from the pressure relief valve without removing or isolating the relief valve from the system. ALTERNATIVE MEANS OF PRESSURE RELIEF MUST BE PROVIDED WHEN THE VALVE IS OUT OF SERVICE. After isolating the relief valve, bleed all pressure from both relief and pilot valves before removing the pilot valve.

Both pilot and pressure relief valve are exposed to process vapors. Observe all plant procedures and Material Safety Data Sheets for the products in the system when inspecting, adjusting or servicing the valves. Vents on the body and spring bonnet of the pilot valve must be clean and unobstructed for proper and safe operation of the valve. These vents should be inspected periodically. Back out set pressure adjusting screw to relieve all spring pressure before removing the spring bonnet.

Blowdown needle chamber is exposed to system pressure. The screw may be adjusted from nearly contacting the seat (screw bottomed out) for snap action to partially retracted for maximum modulation. The screw is retained by the blowdown bushing. DO NOT remove the blowdown bushing while under pressure.

The tank pressure required to discharge the normal or emergency venting requirements of the tank will be increased by the amount of back pressure in the discharge header. Maximum possible discharge header pressure must be considered when sizing the pressure relief valve.

INSPECTION AND INSTALLATION

The pilot valve or pilot operated pressure relief valve is packaged and supported to prevent damage or contamination during shipping. It should be similarly protected during subsequent handling and storage. Always keep all ports plugged to prevent intrusion of foreign materials. Before installation, inspect the unit visually. If there are indications of physical damage or internal contamination, the valve must be disassembled, cleaned and inspected before installation. The spring adjustment cap and blowdown screw locknut must be secure. Report any shipping damage to your carrier.

The pilot valve is installed on the top port of the relief valve actuator with a 1/2" Sch. 40 pipe nipple of minimum length and material suitable for the tank contents. There should be no block valve or other restriction between the pilot valve and the actuator. Wrap all pipe threads with fluoropolymer tape or apply a suitable pipe thread sealant sparingly. Before connecting sense line, backflow compressed air through line and pick-up fitting in relief valve to assure that no obstruction exists. Connect sense line to relief valve and pilot valve with no in-line block valve or other restriction. If a check valve is used in the sense line for backflow prevention, make sure it is unrestricted and installed with the correct flow direction (Fig 8). The same procedures and precautions apply if a remote sense line is used.

Field test connection, manual/remote blowdown and pilot discharge connections, if applicable, must be connected according to the Fig. 8, 9 and 10. Set pressure and blowdown adjustment may be done on the test bench (following the procedure on page 11) or on the relief valve. The initial set pressure and spring range can be found on the pilot valve nameplate.

OPERATION

Both relief pressure and blowdown are set at the factory to comply with the specification on the purchase order. If blowdown is not specified, snap action with 7-10% blowdown will be furnished. The range of adjustment will depend on the spring installed and will be stamped on the nameplate. The pressure setting may be changed within the designed range either while on line or in a service shop. Observe the proper setting and testing procedure in this manual.

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