ARIELHead End Pneumatic

Fixed Volume ClearancePocket Unloader

(FVCP)TECHNICAL MANUAL

ARIEL CORPORATION35 BLACKJACK ROAD, MOUNT VERNON, OHIO 43050

TELEPHONE: 740-397-0311 FAX: 740-397-3856VISIT OUR WEB SITE: www.arielcorp.com REV: 2/01

CAUTIONTO PREVENT PERSONAL INJURY, ENSURE THAT COM-PRESSOR CRANKSHAFT CANNOT BE TURNED BY THEDRIVER OR COMPRESSOR CYLINDER GAS PRESSUREDURING MAINTENANCE: -- ON ENGINE-DRIVEN COMPRES-SORS, REMOVE THE CENTER COUPLING OR LOCK THEFLYWHEEL. -- ON ELECTRIC MOTOR-DRIVEN COMPRES-SORS, IF IT IS INCONVIENIENT TO DETACH THE DRIVERFROM THE COMPRESSOR, THE DRIVER SWITCH GEARMUST BE LOCKED OUT DURING MAINTENANCE.BEFORE STARTING ANY MAINTENANCE OR REMOVINGANY COMPONENTS, RELIEVE ALL PRESSURE FROM THECOMPRESSOR CYLINDERS. SEE PACKAGERS INSTRUC-TIONS FOR COMPLETELY VENTING THE SYSTEM.

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FOR: FVCPImportant Safety Information

CAUTIONSEVERE PERSONAL INJURY AND PROPERTY DAMAGECAN RESULT IF PRESSURE SYSTEM IS NOTCOMPLETELY VENTED BEFORE LOOSENING THE BOLTSON FLANGES OR FITTINGS TO PRESSURE CONTAININGAREAS. CONSULT ARIEL TECHNICAL MANUAL BEFOREPERFORMING ANY MAINTENANCE.

CAUTIONHOT GAS TEMPERATURES, ESPECIALLY THE GASDISCHARGE AREAS, HOT OIL AND HIGH FRICTIONAREAS CAN BE A SOURCE FOR BURNS. WEAR PROPERINSULATION WHEN WORKING AROUND THESE AREAS.SHUT DOWN UNIT AND ALLOW TO COOL BEFOREDOING MAINTENANCE IN THESE AREAS.

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FOR: FVCP FIGURE 1: FIXED VOLUME CLEARANCE POCKET (FVCP) HEAD END PNEUMATIC UNLOADER - TYPICAL

O-rings

O-ring

Actuator Cap

Stat-O-Seal Washer

Mechanical Indicator

Adapter Flange

Orange -Open Position(Unloaded)

Control Media Connection

Glyd Ring (with O-ring

Cylinder Head Fasteners

Vent to Safe Atmosphere

Crossbar

Actuator Cylinder

Actuator Piston

Gasket

Data Plate

Drake Locknut

Valve Guide

Valve

Breather Vent to Safe Atmosphere

StemPneumatic-Unloader Cylinder-Head

OPEN POSITION - UNLOADED

O-ring

U-Cup Seal Ring

Spring(if required)

Adapter Flange to Unloader Cylinder-Head Fasteners

Volume Filler (as required)PAGE 4 2/01

FOR: FVCP FIGURE 2: FVCP ACTUATOR CYLINDER DETAILS (OPEN POSITION - UNLOADED) - TYPICAL

OrangeOpen Position(Unloaded)

O-ring

Actuator Cap

Stat-O-Seal Washer

Mechanical Indicator

Control Media Connection

Actuator Cylinder

Breather Vent to Safe Atmosphere

U-Cup Seal Ring

Stem

Spring(if required)

1/2- 20 12 Point Capscrew

(6) 1/2- 20 Hex Head Capscrew

Actuator Piston2/01 PAGE 5

FOR: FVCP FIGURE 3: FVCP CLOSED POSITION - TYPICAL

Mechanical Indicator

1/8 inch NPT

1/8 inch NPT

1/2 inch NPT Oil drain at Shutdown/Blow-down (Not Shown)

(1) 1/2- 20 12 Point Capscrew

(4) 5/16- 18 Socket Head Capscrews Lockwire in Pairs

(6) 1/2- 20 Hex Head Capscrew

(1) 1/2- 20 Drake Locknut

(3) 1/2- 20 Typical Stud/Drake Locknut

Black - Closed Position

(4) 1/2- 13 12 point Capscrew

(3) 3/8- 16 Socket Head CapscrewPAGE 6 2/01

FOR: FVCP FIGURE 4: CROSSBAR

FIGURE 5: ALVE GUIDE2/01 PAGE 7

FOR: FVCP Description and OperationThe pneumatic or automatic fixed volume clearance pocket (FVCP) unloader is designed to add a fixed amount of volumetric clearance to a compressor cylinder. By adding clearance, the cylinder's throughput and power consumption are reduced, allowing the operator to uti-lize automated power and capacity control through a range of pressures. When the pocket is open, all of its internal volume is added to the cylinder's base clearance, reducing power consumption and throughput. When the pocket is closed, the cylinder is operating at base clearance, with maximum power consumption and throughput. There is no intermediate step with a FVCP - it's either open or closed.

ActuatorThe actuator assembly is attached to the unloader adapterflange, and is the outer most por-tion of the unloader. It consists of a cylinder, cap, piston, stem, bolt, return spring (in some cases), indicator, fasteners and seals. An actuating medium (typically compressed air or fuel gas) is supplied at the outboard end of the actuator, via a control valve. When pressure is applied, the actuator piston travels toward the crankshaft, forcing the unloader valve to close. When pressure is released, the compressor cylinder gas pressure (and return spring where applicable) force the piston away from the crankshaft, until the piston stops when it contacts the cap, opening the unloader valve. An indicator in the actuator cap indicates when the actuator piston is outboard, meaning that the pocket is open. Actuating gas pressure will be supplied via a control valve, which will allow compressed gas to enter the actuator and close the pocket, and which will allow this gas to leave the actuator and open the pocket. The actuator MAWP is 150 psig (10.3 bar), and actuating gas should be supplied at no more than 125 psig (8.62 bar). The minimum actuating pressure varies with cylinder design pressure, and will be stamped on a data plate, located on the unloader assembly, and will also be published in the unloader parts list.

Unloader ValveThe unloader valve is located inside the clearance pocket, and it is attached to the actuator stem via the crossbar. Gas pressure in the actuator cylinder causes the chamfered end of the valve to seal against the chamfered seat on the cylinder head. When the actuating gas pressure is released, the valve moves away from the seat, opening the pocket volume to the cylinder.

Sealing ElementsGas pressure in the actuating cylinder is contained by three sets of seals. The cap utilizes an o-ring face seal, the piston utilizes a u-cup style piston seal, and the mechanical indicator utilizes an o-ring/chamfer style seal. In addition, there is a Stat-o-seal between the actuator piston and the bolt that holds the piston to the stem. At the interface of the actuator cylinder PAGE 8 2/01

FOR: FVCP to the adapter flange, a fiber gasket contains any leaked process gas or actuating gas that may escape past primary seals.Inside the volume pocket, the unloader valve is sealed against the guide by a Glyd Ring. This is a relatively large diameter o-ring seal in the bottom of a groove, with a step-cut piston ring above it. An o-ring provides the seal between the adapter flange and the head, and pairs of o-rings seal between the adapter flange and the seal gland, and between the seal gland and the actuator stem.

Vents and DrainsThe following vent connections must be made by the packager, and all are critical to proper operation and durability of the unloader, as well as to safety of operation and maintenance personnel. All vents and drains must be installed in such a manner as to prevent the collec-tion of liquids that could cause the build up of either gas or liquid. When a heavier than air gas is involved, vent and drain design must be accommodating.A 1/8 inch NPT breather connection on the actuator cylinder outside diameter allows leak-age gas from the actuating cylinder and the volume pocket to be safely conducted to flare or a safe atmosphere. Additionally, this connection allows for the air trapped behind the actua-tor piston to escape when the valve closes, so that the actuating piston does not do the work of compressing this air.A 1/8 inch NPT connection on the adapter flange outside diameter allows leakage gas from the actuator stem seal to be safely conducted to flare or a safe atmosphere.A 1/2 inch NPT connection on the head flange outside diameter allows trapped cylinder lubricating oil to be drained whenever the unit is shut down and blown down for servicing. The pocket could conceivably retain oil to a depth reaching the unloader valve diameter, effectively decreasing the pocket volume by that amount. This oil should be drained at every opportunity in order to ensure proper compressor performance.It is critical, for the safe operation of the compressor, to ensure that all vents and drains are open, functional and, if necessary, tubed off of the skid or out of the building. Depending upon your climate and insect population it can be necessary to install screens over the vents and drains to ensure that they do not become blocked. This can be essential if the compres-sor is shutdown for a long period of time.

Disassembly and MaintenanceRoutine maintenance will include inspection of the sealing elements and sealing surfaces, and replacement of these items as required. Before attempting any maintenance on the unloader, all applicable safety precautions must be observed, including but not limited to: shut down the compressor and blow down the piping and cylinders to relieve all pressure; lock the unit to prevent the crankshaft from rolling. For any unloader maintenance, the recommended first step is to disconnect all vent and drain lines and the actuating gas line from the unloader, and to remove the unloader flange assembly from the head. Remove the adapter flange fasteners and separate the assembly 2/01 PAGE 9

FOR: FVCP from the head. Threaded holes are provided in the adapter flange (and cylinder-head) for toolbox eye bolts to assist lifting. The assembly is heavy and caution must be exercised to prevent injury. Using a crane is recommended. Inspect o-rings and replace as necessary.Remove the (six) 1/2 inch - 20TPI capscrews that hold the actuator cap and cylinder on the adapter flange. Remove the cap and inspect the o-ring face seal and sealing surfaces, and replace as necessary. If actuating gas leakage was detected at the mechanical indicator o-ring seal, remove indicator and replace o-ring. Reassemble and tighten indicator to 15 lb-ft (20 Nm) maximum.Remove the actuator cylinder by pulling it away from the flange, over the piston. Inspect the cylinder bore and the piston seal, and replace as necessary. Inspect the gasket in the groove on the flange, and replace as necessary.Cut and remove the lockwire from the (four) 5/16 inch - 18TPI socket head capscrews on the crossbar, and remove the capscrews. Remove the unloader valve by sliding it away from the crossbar, over the valve seal. Inspect the valve bore and chamfered sealing surface for wear or damage, and repair or replace if necessary. Take care not to damage the sealing end of the valve while handling or storing. Inspect the Glyd Ring (with its step cut sealing ring and o-ring back-up) for wear or damage, and replace if necessary. Also, inspect the chamfered sealing surface in the head for wear or damage. If damaged, it may be possible to rework this surface.Remove the drake locknut from the actuator stem, under the crossbar, and gently pull the piston and stem assembly away from the adapter flange. Inspect the entire stem and the locknut for wear or damage, and replace if necessary. If the piston and stem must be disas-sembled, replace the Stat-o-seal washer. Take care not to damage the stem during handling or storage.Remove the (four) 1/2 inch - 13TPI 12-point capscrews that fasten the unloader guide to the adapter flange. Remove the guide, inspect the o-rings and sealing surfaces, and replace o-rings as necessary.Remove the (three) 3/8 inch x 16TPI socket-head capscrews that fasten the stainless steel o-ring retainer to the adapter flange. Inspect the o-ring and sealing surfaces, and replace 0-ring if necessary.

AssemblyOil all o-rings and all moving parts prior to, during or after assembly. Insert the o-ring into the counterbore on the outside surface of the adapter flange, and install the o-ring into the groove in the stem bore, near the opposite face of the adapter flange. Install the stainless steel o-ring retainer, and fasten with the (three) 3/8 inch x 16TPI socket head capscrews. Tighten capscrews to 193 lb-in (22 Nm) torque.Install the o-rings on the gland outside diameter and in the adapter flange face groove, and install the guide. Be sure to align the crossbar opening so that the crossbar will be horizontal when the unloader assembly is installed in the head. This will prevent the valve assembly from rotating, which could allow the crossbar to rub on the valve guide during operation. Tighten the (four) 1/2 inch - 13TPI 12-point capscrews to 40 lb-ft (54 Nm) torque. PAGE 10 2/01

FOR: FVCP If the piston and stem were disassembled, reassemble them with a new stat-o-seal. Apply a lubricant to both sides of the stat-o-seal before assembly. Tighten the 1/2 inch - 20TPI 12-point capscrew to 46 lb-ft (62 Nm) torque. Use the 7/8 inch (22 mm) wrench flats on the stem behind the piston. If the piston u-cup seal ring is being replaced, be sure the u-cup faces the actuator cap.Install a new actuator cylinder gasket in the groove in the adapter flange if required. Oil the actuator cylinder bore and place it in position over the gasket. The cylinder vent connection should be oriented to be nearest to the adapter flange. Place the return spring (when pro-vided) in the cylinder, located around the (four) 1/2 inch 12-point capscrew heads. Spread lubricating oil on the actuator stem and insert it through the seal gland. Twist and wiggle the stem slightly as required to get it started through the o-rings in the seal gland. Push the pis-ton and stem assembly until you can engage the crossbar on the threaded end of the stem and install the lower half of the 1/2 inch - 20TPI Drake locknut. There will be some resis-tance from the return spring (when provided), but you should be able to overcome the spring by hand. The starting chamfer at the top of the actuating cylinder will properly compress the piston seal.Tighten the bottom half of the Drake locknut to 36 lb-ft (49 Nm) torque, with a 3/4 inch box wrench on the Drake nut and a torque wrench on the 12-point capscrew. This method requires a slight amount of torque to overcome the friction of the seal gland o-rings, but this friction is negligible. Install the top locking half of the Drake locknut and tighten it to 20 lb-ft (27 Nm) torque.

Replace the actuator cap o-ring and indicator o-ring as required. Install the cap on the actu-ator cylinder. Rotate the cylinder and actuator cap as required to properly align the control media connection with its line connection, relative to the vent connection in the adapter flange. Install and tighten the (six) 1/2 inch - 20 TPI hex head capscrews to 46 lb-ft (62 Nm) torque.Replace the Glyd Ring seal components (located on the valve guide) as necessary. Oil the valve bore and install over the end of the guide. Pinch the Glyd Ring as necessary to allow the valve chamfer to ride up onto the Glyd Ring. The ring is being squeezed by the valve, so there will be some amount of resistance to movement. Continue pushing the valve until it engages the crossbar, being careful not to damage the sealing surface of the valve.

FIGURE 6: DRAKE LOCKNUTBOTTOM HALF

TOP - LOCKING2/01 PAGE 11

FOR: FVCP Install the (four) 5/16 inch - 18TPI socket head capscrews and tighten to 108 lb-in (12 Nm) torque. Lockwire these capscrews in pairs. Use new 0.039 to 0.041 inch (1 mm) 302/304 stainless steel lockwire, made for this purpose. Match pairs of cap screws so that the holes in the heads are between 2 and 6 oclock to a line running thru the heads, see Figure 7:, Step #1. Insert wire thru first screw head, bend around the head and twist ends together in a clockwise direction, see Figure 7:, Step #2. Continue twisting wire ends together to the paired cap screw. Insert the top end of the wire into the screw head hole and bend the bot-tom end around the head. Twist ends together in a counter-clockwise direction, see Figure 7:, Step #3. Cut off excessive length and turn the twisted ends in along the screw head, leaving no sharp ends to avoid safely hazards, Figure 7:, step #4.

Install the unloader assembly in the head and align with the connection lines. Go slowly to ensure that the guide enters the unloader valve bore without damaging any components. Tighten the adapter flange to unloader-head fasteners as indicated in the compressor tech-nical manual or toolbox chart.Reconnect actuating gas line, vents and drains.

FIGURE 7: LOCKWIRING

STEP #1

STEP #2

STEP #3

STEP #4PAGE 12 2/01

FOR: FVCP Recommended Maintenance Intervals

Daily1. If shutdown and blown down, drain cylinder oil from the unloader.

Monthly (plus Daily)1. Check vents for blowing. If blowing, replace seals.2/01 PAGE 13

FOR: FVCP Ariel Telephone, Fax, E-Mail and Web Numbers

Ariel Response Center Technicians or Switchboard Operators will answer the tele-phones during Ariel business hours, Eastern time - USA or after hours by voice mail.

The after hours system works as follows:1. Follow automated instructions to Field Service Emergency Technical Assistance

or Spare Parts Emergency Service.2. Calls are answered by voice mail.3. Leave message: callers name, telephone number, serial number of equipment

in question (frame, cylinder, unloader) and brief description of emergency.4. Your voice mail message is routed to an on-call representative, who will respond

as soon as possible.

Users must order all parts through Authorized Distributors.

TABLE 7-1: NUMBERS FOR CONTACTING ARIELCONTACT TELEPHONE FAX E-MAIL

Ariel Response Center 888-397-7766(toll free USA & Canada) or740-397-3602 (International)

740-397-1060 arc@arielcorp.comSpare Parts 740-393-5054 spareparts@arielcorp.comOrder Entry 740-397-6450 ---

Ariel World Headquarters 740-397-0311 740-397-3856 info@arielcorp.comTechnical Field Service fieldservice@arielcorp.com

Web site: www.arielcorp.comPAGE 14 2/01

Important Safety InformationDescription and OperationActuatorUnloader ValveSealing ElementsVents and DrainsDisassembly and MaintenanceAssemblyRecommended Maintenance IntervalsDailyMonthly (plus Daily)

Ariel Telephone, Fax, E-Mail and Web Numbers