Reference_-_Filter_Ops_Manual_9_30_22_2f_3.pdf

Operation and Maintenance of Ohmsett Contract E17PC00014

Operating Procedures for the Ohmsett Filtration System

Prepared for:

Bureau of Safety and Environmental Enforcement (BSEE) Contracting Officer’s Representative (COR)

Frank Jurado BSEE Oil Spill Preparedness Division

45600 Woodland Road Sterling, VA 20166

Email: Frank.Jurado@bsee.gov Ph. 571-279-7896

Prepared by:

Applied Research Associates, Inc.

Operating Contractor

Ohmsett Facility Naval Weapons Station Earle (NWSE)

Waterfront Route 36 P.O. Box 150, Leonardo, NJ 07737

Date: September 30, 2022

Operation and Maintenance of Ohmsett Contract E17PC00014 i

TABLE OF CONTENTS

1. REQUIREMENT

2. APPROACH

2.1. DIATOMACEOUS EARTH FILTRATION

2.2. GENERAL SYSTEM DESCRIPTION

2.3. FILTRATION PROCESS OPERATIONS

2.3.1. Educt pre-coat

2.3.2. Fill

2.3.3. Pre-coat

2.3.4. On-line operation

2.3.5. Circulate/hold

2.3.6. Blowback

2.3.7. Sluice

2.3.8. Cycle off

3. SYSTEM CONTROL AND POWER

3.1. SYSTEM CONTROL

3.2. ELECTRICAL POWER

3.3. PNEUMATIC CONTROLS

4. PRE-COAT PREPARATION

4.1. PURPOSE OF THE PRE-COAT

4.2. DETERMINING PRE-COAT AND BODY FEED DOSAGES

5. OPERATIONAL PROCEDURES

5.1. EDUCT PRE-COAT FILL AND PRE-COAT

5.2. FILTER MODE

5.3. SLUICING

5.4. TEST BASIN WATER CLARITY AND CHLORINATION

6. OBERLIN BELT PRESS FILTER

6.1. GENERAL DESCRIPTION

6.2. SEQUENCE OF OPERATION OF OBERLIN FILTER

6.2.1. Oberlin Filter (Serial No. OPF04-553SD)

ii

6.2.2. Operation Sequence

6.2.3. Interface Signals

6.2.4. Manual Overrides

6.2.5. Shutdown Procedures

7. CHLOROPAC ELECTROLYTIC CHLORINATION SYSTEM

7.1. INTRODUCTION

7.2. CHLOROPAC MANUAL

TABLE OF FIGURES

Figure 1. Basic components of the Ohmsett filtration system

Figure 2. View of the Filter Programmable Logic Control (PLC)

Figure 3. Ohmsett Filtration System Showing Piping

Figure 4. Ohmsett Filter in Fill Operation

Figure 5. Ohmsett Filter in Pre-coat, Circulate, and Hold Operation

Figure 6. Ohmsett Filter in Filtration Mode

Figure 7. Ohmsett Filter in Sluice Operation

Figure 8. Ohmsett Filter Pneumatic Distribution Piping

Figure 9. Ohmsett Filtration Conduit Layout

Figure 10. Ohmsett Filter Operation: Turbidity versus Operation Day for One Season

Figure 11. Basic Oberlin Filter Components

1. REQUIREMENT

Contract E17PC00014, Task Order E17PD00117, Section 2.4.1.12.E Detailed Operations Manuals. These manuals detail required routine activities and are to be used as references by the Contractor in operating the systems described. These manuals also guide the routine operations and maintenance of the facility.

The Contractor shall update the manuals as needed when major changes occur.

2. APPROACH

2.1. DIATOMACEOUS EARTH FILTRATION

The Ohmsett test tank water quality must be maintained for clarity to enable underwater photography.

Like a swimming pool, Ohmsett uses a diatomaceous earth (DE) filter system that is scaled-up to maintain the 2.6 million gallons of seawater in the tank. The system is composed of a thin layer of DE that is used as a filter cake on a porous septum to filter the water. As feedwater from the test basin passes through the filter cake, suspended solids in the feedwater are trapped in the filter cake and septum. The total solids found in influent water can exist in a distribution of sizes, from individual ions up to visible particles.

There are four categories of solids and each category is defined by size: (1) Soluble solids are smaller than

0.001 microns (one micron is one-millionth of a meter); (2) Colloidal solids are 0.001–1 micron; (3) Supra-colloidal solids are 1–100 microns; and (4) Settling solids are larger than 100 microns. Suspended solids are equivalent to the combination of the supra-colloidal and settling fractions. DE filters are designed to remove particulates from water that are one (1) micron and larger.

The Ohmsett DE filtration process can remove suspended solids, but not colloidal matter, and a wide variety of DE grades are available for use. The coarser grades have greater permeability and solids-holding capacities than do the finer grades, which will generally produce a clearer effluent. Some grades of DE are pre-treated to change their characteristics for improved performance. If colloidal solids are present in the form of droplets, such as finely dispersed oil or dispersant, additional filter media (e.g., cellulous) are required to trap colloidal oil products.

2.2. GENERAL SYSTEM DESCRIPTION

The high clarity of the Ohmsett test basin water is achieved via filtration through a U.S. Filter Co. Autojet 1000 filter. The filter system underwent a complete replacement in 2004. This effort included replacing all the components, upgrading the control system to a Programmable Logic Control (PLC) system, replacing most of the internal steel piping with salt water corrosion-resistant fiberglass piping, installing new air compressors, chlorinator and filter pump, and constructing a climate-controlled steel housing around the filter equipment for greater longevity.

The Autojet 1000 has 28 five-foot-diameter porous septum disks that are covered with nylon cloth. The filter leaves are coated with finer layer of filter media, typically finer DE. A slurry of DE is introduced into the filter prior to each filtration cycle so that a uniform layer of DE is deposited on the leaves in a process call “pre-coat.” The pre-coat process takes about 15 minutes and each filtration (or “on-stream”) cycle generally lasts between 6 and 100 hours, depending upon water clarity.

Although the basic filtration process is simple (Figure 1), the larger-scale system is complex. The operator needs to understand the significance of each phase in the treatment system. The system is composed of five tanks, including the filter; two tanks are for mixing the DE as a pre-coat slurry. The sluice pit holds the used DE slurry from the filter, while another tank holds water that is removed from the spent slurry. The water recovered from the spent slurry is pumped back into the tank, just upstream of the filter intake, and recycled back through the filter.

A 2,000 gallon-per-minute (gpm) centrifugal pump with a 125-horsepower (HP) electric motor is used to circulate the tank water through the filter. Electrical power is distributed from a motor control center (MCC). Water flow is controlled by pneumatic-actuated valves that use compressed air to activate current to pressure (I/P) converters. A screw compressor and in-line receiver supply the compressed air. The position of the water valves are controlled by an Allen-Bradley PLC with a touch-screen human machine interface (HMI).

Figure 1. Basic components of the Ohmsett filtration system

2.3. FILTRATION PROCESS OPERATIONS

Below is a general overview of the eight phases in the operation of the filtration system. More information is provided in subsequent sections and figures of this manual. To begin a cycle, there must be power to all systems; the main pump must be on, and slurry must be mixed in the pre-coat tank.

2.3.1. Educt pre-coat

The DE slurry is withdrawn from the slurry tank through an eductor and fed into the filter. After a set amount of time (approximately six minutes) the valves to the eductor automatically close, stopping the eduction phase.

2.3.2. Fill

Once the pre-coat material is in the filter, the main filter inlet valve opens, and water from the circulation pump enters the filter to fill the filter chamber. Once water is detected at the filter’s air vent, the filling phase is complete. This usually takes two and half to three minutes.

2.3.3. Pre-coat

With the filter full, the pre-coat circulate valve opens, which allows the water in the filter chamber to recirculate. The DE slurry is circulated in the filter for six minutes to coat the leaves with the filter DE.

2.3.4. On-line operation

Once the DE has caked onto the leaves, the filter switches to operational mode and will remain online until the differential pressure across the filter leaf remains below threshold. As the filter operates and removes contaminants from the test basin water, the head loss pressure between the filter inlet and outlet increases, and water flow diminishes. If the differential pressure exceeds a preset value, typically 50 pounds per square inch (PSI), the filter operation stops. If the water is relatively clear, the filter could run continuously for up to 100 hours. This is a significant amount of time compared to vacuuming the tank, which can clog the filter in 30 minutes.

2.3.5. Circulate/hold

Once the pressure drop threshold is exceeded, the filter switches from the filtration mode to a back-flush operation. Water flow is reversed, and flow is from the interior of the filter through the leaves, releasing the DE cakes. The recirculation mode is one minute long and the “spent” DE waste is re-suspended as a slurry that is pushed out in the blowback phase.

2.3.6. Blowback

During blowback, the filter chamber is pressurized and the bulk of spent DE slurry is pushed out the bottom of the filter housing to the sluice pit, leaving residue on the interior surfaces that are rinsed off in the sluicing phase. This step takes six minutes.

2.3.7. Sluice

Using water spray, the residue DE on the leaves and interior of the vessel is rinsed off and the wash water is pushed to the sluice pit. The contents of the sluice pit are pumped through an Oberlin filter press that dewaters the slurry of spent DE. The dewatered DE from the Oberlin is discharged into a dumpster for off-site disposal. The recovered water is returned to the filter intake for filtering.

2.3.8. Cycle off

The cycle ends with completion of the sluice, at which time the system shuts down and must be manually restarted.

3. SYSTEM CONTROL AND POWER

3.1. SYSTEM CONTROL

The filter system is an electro-pneumatic control system with the operational limits determined by head loss through the filter. All operational valves are opened or closed by air pressure; the air is directed to the appropriate valve using I/P converters controlled by the PLC program. The position of the I/P that controls the water valve during the respective phases are listed in Sequence (Table 1).

3.2. ELECTRICAL POWER

The filtration system uses a 480VAC-400-amp sub-panel in the filter room that is powered from the main power distribution panel in Building R-26. Almost all the motors in the filter system and the step-down transformers are powered from a MCC in the filter room. The electrical components are shown as a flow diagram in Figure 2.

From the power cabinet, electrical wires connect to motors, solenoids, heat tracing, and electrical receptacles through a network of 15 conduits shown in Figure 3. The filter control cabinet is physically separate from the power cabinet, but is electrically connected with 43 wires. The valve actuator solenoids, motor starter relays, and auto dialer are controlled from the PLC in the control cabinet. Based on the input signals from the filter body pressure switch (PS44 in Figure 4), the differential pressure switch (P53, Figure

4. Ohmsett Filter in Fill Operation), and the PLC manages the operation of the filter using the sequence in Table 1.

3.3. PNEUMATIC CONTROLS

As described, the control system energizes the valve actuator solenoids. An electromagnetic coil pulls a pneumatic slide, thereby causing air to flow and change the state of the respective actuator. Each of the 10 air-actuated valves listed in Table 1 are controlled by the ladder logic program in the PLC.

The air is provided by a 25-cubic-foot per minute (CFM), 120-psi compressor. Before reaching any of the actuators, the air is filtered, dried, filtered a second time, and dried again (after cooling in the first of two receiving tanks.) Two types of air are required for the system; one goes to the actuators, the other to the control panel. The air that goes to the actuators passes through in-line oilers where small amounts of oil are picked up to lubricate the sliding valves. The control panel requires clean, oil-free, dry air. All the air-actuated control valves, except one, are either fully open or fully closed. The filter inlet valve is a modulating valve that regulates the volume of air to the filter (see Figure 4 through Figure 9).

Figure 2. View of the Filter Programmable Logic Control (PLC)

Table 1. Filter Operation Sequence

Sequence of Filter Operation Programmed into the PLC Sequence Educt

Pre-coat Fill Pre-coat Filtering Circulate Hold

Blow Back Sluice Off

Valve ID

Filter Inlet A X X X X

Filter Outlet B X

Filter Drain C X

Filter Sluice D X

Filter Vent E X X

Side Drain G X

Air Inlet H X

Pre-Coat Circulate J X X

Filtrate By-pass K X

Eductor Outlet L X

Filter Pre-coat Inlet N X

Pump P1 X X X X X X

Shaft Motor M1 X X= Energized I/P to open valve

Figure 3. Ohmsett Filtration System Showing Piping

Figure 4. Ohmsett Filter in Fill Operation

Figure 5. Ohmsett Filter in Pre-coat, Circulate, and Hold Operation

Figure 6. Ohmsett Filter in Filtration Mode

Figure 7. Ohmsett Filter in Sluice Operation

Figure 8. Ohmsett Filter Pneumatic Distribution Piping

Figure 9. Ohmsett Filtration Conduit Layout

4. PRE-COAT PREPARATION

4.1. PURPOSE OF THE PRE-COAT

A filter media (e.g., DE/cellulous) deposited on the filter septum provides a porous matrix during the pre-coat cycle, enabling the suspended solids to be trapped while allowing water to pass. The media adheres to the filter septum and bridges across the openings in the septum; suspended solids do not contact the septum. At the end of the filter cycle, the pre-coat (filter cake) is removed, leaving a clean septum ready for the next pre-coat. The filter's effectiveness depends on the formation of a firm pre-coat and the complete separation of spent filter cake from the septum at the end of the filter cycle.

There is a selection of filter media that are suitable for use at Ohmsett. They include DE of varying grades, cellulose, pearlite, and other silica-based powders; historically, the combination of cellulose and DE results in brilliant water clarity. Removing high levels of suspended solids is best achieved using coarse diatomaceous earth alone, although the effluent is not very clear. If the suspended solids consist of finely dispersed oil, cellulose/DE combination has been used effectively as a blend filter media to remove the particulates.

4.2. DETERMINING PRE-COAT AND BODY FEED DOSAGES

In general, the pre-coat on leaf filters is between 0.1 to 0.2 pounds per square foot (PSF) of septum. The Ohmsett Autojet filter has 1,000 square feet of septum and has been found to successfully operate with pre-coats of 150 pounds or 0.15 pounds PSF. The operator can confirm that the pre-coat is adequate by measuring the turbidity of the filter influent, effluent, and observing the filter's differential pressure.

Turbidity is the optical property in water that causes light to scatter rather than be transmitted. When a beam of light passes through water, particles in the water disperse the light giving the light a cloudy appearance. One way to measure turbidity is by measuring the intensity of light dispersed at right angles to a light beam and comparing that intensity to a standard. The filter operator uses an instrument called a turbidimeter that measures turbidity in nephelometric turbidity units (NTUs). Figure 10 graphically shows the turbidity of influent and effluent water samples taken from the Autojet during one season of tests.

Applying the proper amount of pre-coat is accomplished by mixing a slurry of pre-coat and adding the volume of slurry that contains the desired weight of pre-coat. An example of how this works at Ohmsett in preparing a 150-pound pre-coat starts with knowing the volume of the pre-coat tank.

The pre-coat tanks are vertical cylindrical tanks, 48 inches in diameter and 72 inches high, with a usable slurry depth of 66 inches. The most convenient way to measure the volume is by depth. If a slurry is prepared so that 22 inches of slurry contains the entire pre-coat (a typical cycle), the educt/pre-coat operation can be easily monitored. At Ohmsett, this is equivalent to 150 pounds (three 50-pound bags) per 22 inches of slurry.

Preparing a full tank of slurry, therefore, requires 450 pounds (nine bags) of DE, mixed with 66 inches (500 gallons) of water.

Figure 10. Ohmsett Filter Operation: Turbidity versus Operation Day for One Season

5. OPERATIONAL PROCEDURES

The pre-coat quantities, flow rates, pressures, running times, and differential pressure may vary from those described in the following sections to establish optimum performance in certain situations.

5.1. EDUCT PRE-COAT FILL AND PRE-COAT

• Fill the pre-coat tank with fresh water up to the fill line. This is equal to 500 gallons of water.

• With the pre-coat mixer running, add the required dry weight of pre-coat material. For DE, 450 pounds (nine bags) are added. Allow 5 to 10 minutes for the pre-coat to disperse.

• Begin the filtration cycle in manual mode. With the filter pump off, the filter vessel is filled using city water to educt 22 inches of slurry out of the pre-coat tank. This takes six minutes.

• City water is turned off, educt ends, the main filter pump turns on and pumps at 500 gpm to finish filling the tank using the test basin water.

• When sensors indicate the filter vessel is full, the system shifts into recirculate mode to coat the filter leaves with DE. The filter pump runs at 500 gpm for the first minute, and then runs at 1500 gpm for an additional five minutes (six minutes total).

5.2. FILTER MODE

• Once the pre-coat recirculate effluent is clear, the filtering operation begins.

• The system automatically switches from recirculate to water filtration with the circulation pump running at 1500 gpm. The filter discharge pressure should be between five and 10 pounds per square inch.

• The filter remains operational until the differential pressure between the effluent and shell pressure is 50 psi, or until the system runs continuously and “times-out” after 99.9 hours. When the system times-out, it will automatically switch to sluice mode.

5.3. SLUICING

• When the differential pressure reaches 50 psi, the recirculate/hold operation begins. Flow is limited to no more than 1500 gpm. This operation prepares the pre-coat (filter cake) to be washed from the filter septum.

• After one minute of recirculate/hold, the blowback operation starts. Compressed air enters the filter through a valve at the top of the filter shell. Water in the filter is pushed out through the side drains at the base of the shell.

• When the blowback operation stops (six minutes), the filter is empty of water and the sluice operation begins.

• The inside of the tank and the leaves are rinsed of any remaining filter media using spray nozzles operating at 55 psi and 500 gpm. The sluicing period is two minutes.

• The filter is empty of water, cleaned of spent filter media and is now ready for another cycle.

5.4. TEST BASIN WATER CLARITY AND CHLORINATION

The Ohmsett filtration system works in conjunction with the chlorination system to lower turbidity in the test basin water. The filter removes suspended solids (1 to 100 microns in diameter). Algae growth is controlled through chlorination by a Chloropac electrolytic hypochlorite generator. With proper chlorination and filter operation, visibility exceeds 100 feet. For details on the Ohmsett chlorination system, see Ohmsett Chlorination Manual.

Two underwater photo/video studies were conducted in the 1970s. The “Ohmsett Underwater” Video Study (Job Order 21) in 1975 and the “NAVFAC Water Clarity” tests in 1976 report poor visibility at as little as four feet with a turbidity of 3.4 NTU. Excellent visibility was shown in excess of 65 feet at mid-tank when filter influent turbidity was 0.2 NTU and effluent turbidity was 0.02 NTU.

6. OBERLIN BELT PRESS FILTER

6.1. GENERAL DESCRIPTION

The Oberlin pressure filter has two compartments: an upper compartment or filter platen and a lower compartment or filter chamber (Figure 11). The platen moves while the chamber is fixed in place; the filter media lies between these two compartments.

At the beginning of a filtering cycle, pneumatic air bag(s) lower the filter platen against the filter chamber.

Platen seals on the perimeter of the compartments form a liquid tight seal around the filter media. The slurry of spent filter media is pumped into the platen and forced by the pump pressure through the filter media; recovered liquid is collected in the lower compartment and drained out.

When the filter pressure reaches approximately 15 psig, pressurized air (approximately 80 psig) is fed into the platen forcing the liquid through the filter cake and media. After the cake is dewatered (determined by back pressure and time elapsed), the platen is lifted by an air cylinder. The cake is then automatically discharged by a conveyor with an endless filter belt. No hydraulics are used nor is there any mechanical squeezing.

As the conveyor advances, a conveyor limit switch monitors the distance the belt has moved. When the conveyor has moved enough to remove the cake from between the platens, the filter platen automatically descends and a new dewater cycle starts.

Figure 11. Basic Oberlin Filter Components

6.2. SEQUENCE OF OPERATION OF OBERLIN FILTER

6.2.1. Oberlin Filter (Serial No. OPF04-553SD)

Revision History

Rev # Date Description

0 04.Jan.2012 Preliminary Review Draft

1 12.Mar.2012 Checkout at Oberlin Filter Company

READ AND OBEY ALL OF THE SAFETY LABELS ON THE FILTER.

This document is meant to supplement the Oberlin Filter Company Operator & Maintenance Manual.

Prior to operating the filter, the operator should read and understand the manual. Before operating the filter ALL the sheet metal must be properly installed and fastened in place.

***** DANGER *****

Before performing service work in the areas of the platens, read, understand, and follow the safety instructions described in the Oberlin Filter Company Maintenance Manual.

***** NOTE *****

The electrical control panel has both discrete operators and an Allen-Bradley PanelView Operator Interface Terminal. Within this document, the PanelView unit will be referred to as HMI.

***** NOTE *****

The PLC has an integral Ethernet port. The I/P address information is:

I/P Address:100.100.100.010 Subnet Mask: 255.255.255.0 Gateway: xxx.xxx.xxx.xxx

6.2.2. Operation Sequence

6.2.2.1. AT THE FILTER

• The discharge dumpster does not need to be emptied.

• Verify that both end cover doors are closed.

• Verify that both chain lubricators are on. Once the lubricator has been started the dip switch settings must not be changed. If the lubrication canister (LC) is empty and needs to be replaced a red and green LED will be blinking. Refer to the lubricator manual before changing the LC.

• Open the plant water isolation valve, HV-11

• Partially open the drip pan flush throttling valve, HV-12. The valve adjusts the volume of water used to flush the drip pan during a discharge cycle.

• Partially open the external belt wash throttling valve, HV-13. The valve adjusts the volume of water used to wash debris off the belt during a discharge cycle.

6.2.2.2. AT THE PNEUMATIC RACK

• Open the plant air lockout isolation valve, HV-01.

• Check the cake dry regulator setting. The regulator setting should be equal to or five psig above the filter pressure stop feed/start dry set point. Do not exceed 40 psig.

• Partially open the cake dry throttling valve, HV-02, as needed to achieve the desired cake dryness, generally 50% open.

• Check the setting for the filter pump pressure regulator. It should be at least 80 psig.

• Use the needle valve to adjust the feed pump speed. The pump stroke rate will be higher at the start of the feed cycle, and then decrease as the feed cycle progresses. The speed will need to be adjusted when a feed cycle is enabled.

6.2.2.3. AT THE ELECTRICAL CONTROL PANEL

• Switch the main disconnect ON. Wait for the HMI to perform the start-up diagnostics and display the opening MAIN display.

• Make sure the EMERGENCY STOP push button is released by twisting the mushroom head clockwise.

• Press the MASTER START push button.

• The CONTROL POWER ON light should be lit.

• Switch the platen control switch to HOLD OPEN.

• Switch the conveyor control switch to AUTO.

• Press the AUTO SYSTEM START push button.

The filter will initially go to the cake discharge cycle. This is required to ensure that the filter belt is properly located under the upper platen. To begin automatic sequencing of the filter, turn the platen control selector switch to AUTO, and press the AUTO SYSTEM START push button.

Step Conditions to Start Step

Conditions to End Step

Notes

Airbag Required Set Point Conditions

When the filter is running the airbag pressure is monitored for the required pressure. The following conditions apply.

If the upper platen is not closed, or the upper platen is enabled to be opened the required airbag pressure is zero (0).

When the upper platen is closed, the equation for the calculated required airbag pressure set point is twice the filter pressure plus 10 psig.

Before the feed cycle starts, the required airbag pressure is the “ok” to start feed cycle set point.

During the feed cycle, the required airbag pressure is the calculated required set point.

When the feed cycle is done, and before the cake dry cycle starts, the required airbag pressure is the “ok” to start dry set point.

During the cake dry cycle, the required airbag pressure is the calculated required set point.

Step Conditions to Start Step

Conditions to End Step

Notes

Upper platen Closing

The previous discharge cycle is complete.

The platen control switch is in AUTO.

The upper platen closed position proximity switch is engaged.

When the cake discharge is complete, there is a two-second delay. Once the delay is done, the close platen control valve solenoid is energized to shift the platen control valve to the CLOSE position. The solenoid is de-energized after a time delay or when the upper platen is closed.

The upper platen will close, and the airbag(s) will start to inflate.

Airbag(s) Inflating to Start Feed Cycle

The airbag(s) continue to inflate from the upper platen closing step.

The airbag pressure reaches the airbag inflated; OK to start feed cycle pressure set point.

Compressed air fills the airbag(s) and air cylinder.

Start Step

Conditions to End Step

Notes

Feed Cycle The airbag(s) are inflated to the ok to start feed set point.

The feed cycle duration is controlled by time or filter pressure.

The feed cycle will end when one of the following are true:

• The filter pressure reaches the stop feed/start dry pressure set point.

• The feed limit time is done.

• Pressing the stop feed/start dry override, refer to Section 2 for details.

• A high filter pressure fault occurs.

• A shutdown is enabled; refer to Section 3 for details.

The open inlet valve solenoid is energized to open the inlet valve on the filter.

Once the inlet valve has been enabled open, the open filter pump air supply valve solenoid is energized.

The bleed off valve will remain open for a timed period. The purpose of the bleed off remaining open is to release air trapped in the upper platen. When the feed cycle venting timer is done, the close bleed off valve solenoid is energized to close the bleed off valve.

As the filter pressure increases, the calculated required airbag pressure will increase.

If the airbag pressure drops below the calculated required airbag pressure set point the inlet valve will close. The HMI will display that the feed cycle is pending. Closing the inlet valve is done to ensure that there is sufficient sealing pressure on the upper platen to prevent leaking. When the airbag pressure reaches the calculated required pressure set point, the feed cycle will resume.

Feed Cycle Ending

The conditions for the feed cycle to end are true.

The filter inlet valve is closed.

The filter pump is stopped by de-energizing the open filter pump air supply valve solenoid.

After a timed delay, the open inlet valve solenoid is de-energized to close the inlet valve.

Airbag(s) Inflating to Full Pressure/ Start Drying

The feed cycle is done.

The airbag pressure reaches the airbag inflated – Ok to Start Dry set point.

The plant air pressure supply to the filter must be greater than the OK to Start Dry set point.

Start Step

Conditions to End Step

Notes

Cake Dry Cycle General Conditions

Pressurized air will flow into the upper platen to dry the filter cake. The setting of the cake dry throttling valve controls the rate of air entering the upper platen. When air is flowing into the upper platen there will be an audible noise from the cake dry check valve.

If the airbag pressure falls below the calculated required airbag pressure set point, the cake dry valve will close and the cake dry pending becomes true.

This is to ensure that enough sealing pressure is on the upper platen to prevent leaking. When the airbag pressure reaches the required set point the cake dry cycle will resume.

The loss of airbag pressure does not reset the cake dry initial and bleed off timers. The loss of airbag pressure does reset the final dry timer.

Cake Dry:

Pending

The feed cycle is done. The airbag(s) pressure is verified- OK to start dry set point.

The cake dry pending timer is done.

The airbag pressure is checked to be at least equal to the airbag inflated ok to start dry pressure set point. After a timed delay, the open cake dry valve solenoid is energized to open the cake dry valve. The delay in opening the cake dry valve is to allow the airbag pressure to stabilize.

Cake Dry:

Initial

The cake dry pending timer is done.

The cake dry initial timer is done.

The cake dry valve is open.

The bleed off valve is closed.

The free liquid above the filter cake is forced through the filter cake.

Start Step

Conditions to End Step

Notes

Cake Dry:

Bleed off

The cake dry initial timer is done.

The cake dry bleed off timer is done.

The cake dry valve is open.

The bleed off valve is open.

When the bleed off valve is opened during a cake dry cycle, liquid and air will discharge from the valve.

NOTE: The bleed off part is not required for many applications. If this is the case the bleed off may be omitted by setting the bleed off time to zero (0).

Cake Dry:

Pre-Break Through/Final Dry Pending

The cake dry bleed off timer is done.

The filter pressure drops below the start final dry pressure switch setting.

The cake dry valve is open, and the bleed off valve is closed.

The cake dry continues until the filter pressure drops below the start final dry set point.

Cake Dry:

Final

The filter pressure drops below the start final dry pressure setting.

The cake dry final dry timer is done.

The cake dry valve is open.

The bleed off valve is closed.

When the filter pressure is less than or equal to the start final drying set point, the final drying timer will start. This portion will last until the timer is complete. The drop in filter pressure is an indication that the liquid is removed from the upper platen.

When the cake dry final dry timer is done, the cake dry valve is closed.

If the filter pressure increases above the start final dry set point, the final drying timer will reset.

6.2.3. Interface Signals

Signals to the Customer’s Equipment

There are no interface signals to the customer’s equipment.

Signals from the Customer’s Equipment

There are no interface signals from the customer’s equipment.

6.2.4. Manual Overrides

Open Upper Platen The upper platen can be opened by switching the pneumatic switch located on the pneumatic control rack from the NORMAL position to the OPEN position. The pneumatic valve sends a pneumatic signal to the platen control valve.

The system air to the filter MUST be on; the status of the electrical power has no effect.

The upper platen will open regardless of the operational status. This is required as an EMERGENCY SAFETY PROCEDURE.

Platen Hold Open The upper platen can be held open by switching the platen control selector switch on the control panel to the HOLD OPEN position. Following a cake discharge cycle, if the platen control switch is in the HOLD OPEN position the upper platen will not close and the filter will pause in standby mode.

Emergency Stop Pressing EMERGENCY STOP push button on the control panel can disable the master control relay.

Stop Feed/Start Dry The filter can be forced from a filter feed cycle to a cake dry cycle by pressing the STOP FEED/START DRY HMI function key located on the HMI Manual Overrides screen.

Stop Dry/Force Discharge

The filter can be forced from a cake dry cycle into a discharge cycle by pressing the STOP DRY/FORCE DISCHARGE HMI function key located on the HMI Manual Overrides screen.

There is a display to indicate if the abort dry is allowed or not allowed. The forced discharge is allowed when one of the following conditions is true:

The cake dry initial and bleed off timers are done.

A high filter pressure fault occurs.

A forced discharge sequence consists of the bleed off valve opening, and the cake dry valve remaining open. This operation is for a timed period. At the end of this period the cake dry cycle will end. The filter will sequence to the upper platen pre-open venting and continue normally. The filter cake may have more moisture than a normal cake dry.

Open Bleed Off When the bleed off valve is enabled to be closed, the operator can momentarily open the valve by pressing the OPEN BLEEDOFF VALVE function key located on the HMI Manual Overrides screen. There is a display to indicate if the bleed off valve is enabled open or closed.

Conveyor Jog The conveyor control selector switch is located on the control panel. The conveyor motor can be engaged by switching the conveyor control selector switch to the MANUAL position. When the switch is released it will spring back to the center OFF position.

For the conveyor to manually advance, the following must be true:

• The upper platen is opened.

• The platen control switch in HOLD OPEN.

• The filter in standby mode.

• The end cover safety relay is energized.

When the switch is moved from AUTO, the previous cake discharge complete is reset. For normal filter operation the conveyor control must be changed back to AUTO. If the upper platen is opened, switching the conveyor control back to AUTO will cause the filter belt to advance. This is required to properly position the filter belt for the next cycle.

6.2.5. Shutdown Procedures

CAUTION: The filter should not be shut down for extended periods with the airbag(s) pressurized. This can cause premature failure of the platen seals or belts.

6.2.5.1. AUTOMATIC

• Start the shutdown sequence by pressing the auto system stop push button on the control panel door.

• If active, the feed cycle will end.

• The cake drying cycle will sequence normally.

• The cake discharge cycle will discharge the filter. During the shutdown, all four sections of the conveyor belt are washed.

• Push in the EMERGENCY STOP push button to de-energize the MASTER CONTROL RELAY.

6.2.5.2. MANUAL

This procedure should only be used for short-term shutdowns.

• Put the platen control switch in the HOLD OPEN position.

• If the feed cycle is active, press stop feed/start dry push button on the HMI Filter Manual

Overrides screen.

• The cake dry cycle will sequence normally.

• The cake discharge cycle will discharge the filter.

• After the discharge cycle is complete, the FILTER STANDBY status will be active.

• Push the EMERGENCY STOP push button to de-energize the MASTER CONTROL RELAY.

THIS IS THE CORRECT METHOD TO MANUALLY SHUT DOWN THE FILTER.

7. CHLOROPAC ELECTROLYTIC CHLORINATION SYSTEM

7.1. INTRODUCTION

The Ohmsett main test basin is maintained at open ocean salinity and potential Hydrogan (pH). The water is skimmed, vacuumed, and filtered to maintain a clear, clean environment for testing, training, and research. The basin is located outside and exposed to natural solar and weather cycles, as well as natural biota in the local area. These factors create an ideal environment for the natural growth of algae and other microscopic flora and fauna. Unfortunately, this biological growth also causes fouling and reduces visibility during testing. Additionally, removal of suspended biological solids shortens filter cycles, and may create problems with some sensitive equipment and instrumentation.

To combat biological growth and reduce these associated problems, the Ohmsett facility adds sodium hypochlorite to inhibit this biological growth. It has been found that the consistent maintenance of low concentrations of sodium hypochlorite work quite well in these control efforts. Rather than handle and store large quantities of sodium hypochlorite solution, the Ohmsett facility uses a system that employs an electrolytic process to effectively oxidize chloride ion in the saltwater to hypochlorite through the production of nascent chlorine at the anode and dissociation of water at the cathode. This system is known as the Chloropac system manufactured by Electrocatalytic, Inc. The following section includes Sections II and III of the Chloropac system manual, describing the system and theory of operation, installation, operation, and maintenance.

7.2. CHLOROPAC MANUAL