KR PRESSURE REGULATOR: GUIDELINES, OPERATION AND TROUBLESHOOTING
System Integration Guidelines, Operation and Troubleshooting
The purpose of this document is to provide principles of integrating a KR pressure regulator into a hydraulic control system, explain how a KR operates, and discuss how to troubleshoot a KR installation given causes and recommended solutions.
System Integration Guidelines
1- System Start-up
Upon system start-up, there must be load on the pressure regulator piston to prevent hammering/shock that may damage the KR. The following information provides guidelines for setting each operator/actuator correctly prior system start-up. Refer to the installation drawings of the respective KR regulator specifications document for supplemental details.
For KR regulators with a manual operator, the top of the manual adjustment handle must be about 2-3/4 inches from the top of the adjustment head, as shown in Figure 1.
For KR regulators with failsafe air/hydraulic remote operators, the top of the manual adjustment handle must be about 4-1/4 inches from the top of the adjustment head, as shown in Figure 2.
For KR regulators with hydraulic pilot operators, there should be about 1500 psi (500 psi minimum) supplied to the pilot inlet.
2- Rated Regulated Outlet Pressure
The KR pressure regulators (KR) are rated to output a regulated pressure range that is tested and verified prior to shipment. Operating at a pressure outside of this range is possible, but may diminish as the KR wears during service. 0 psi can be achieved by completely unloading the pressure adjustment (decompressing spring to its free state). To match the supply pressure, the pressure adjustment must be completely loaded (compressing springs to solid), which allows the supply pressure to free-flow through the regulator.
NOTE: Although 0 psi is the output, DO NOT attempt to perform maintenance or disassemble any components downstream of the KR while in this state.
To maximize the regulated outlet pressure range, the hydraulic pilot operator is the best option. This operator regulates pressure down to 50 psi and up to the supply pressure.
3- Flow Capacity
Consideration must be given to the flow capacity of the interconnect piping between KR pressure regulators, hydraulic control manifold and the equipment being operated. Inadequate flow capacity may result in excessive back pressure, which can cause the KR to hammer or chatter (e.g. rapid opening and closing) as the KR seeks to shut off at set pressure. Excessive back pressure also will reduce the flow, as the KR may not be fully open, which will reduce the function time of the equipment being operated.
4- Deadband (DB)
Deadband is the difference between the set pressure and the outlet pressure that triggers the KR to open or vent and reset. DB is a function of the friction force between the seal rings and the flow plates. As the outlet pressure slowly changes, the device will not react to the pressure change until the friction has been overcome.
The fluctuation or change in outlet pressure may be caused by a downstream leak, temperature variation, wellbore packer compression or variation in wellbore pressure.
To decrease the DB, either one or all of the following must occur:
Increase the operator piston diameter.
Increase the viscosity/lubricity of the hydraulic fluid.
Decrease the differential between the inlet and the (regulated outlet) set pressure.
HYSTERESIS is observed after an open flow function has occurred. It is measured as the difference between the original set pressure before the KR opens to full flow and the pressure that it resets to when flow is shut off. This range is within ± 150 psi for all KR models.
5- Operating BOPs
It is possible for low deadband to compound an annular packing element failure under certain conditions. The annular packing element seals against the top of the piston, which maintains the well assist closing force in normal operation. When the packing element becomes worn on the bottom, this seal may be compromised and inadequate to maintain enough well assist to keep the element closed. The element will then push back against the piston and thus increase the closing pressure. If the pressure increase is greater than the DB, the regulator will vent to tank and the BOP will open under well bore pressure. This situation may call for a KR with higher DB.
6- Set Pressure Adjustment
When the set pressure on a spring operator is being changed or adjusted, the outlet needs to be briefly opened and closed a few times to allow the operator and pressure to stabilize. This can be achieved by operating a manifold control valve or installing a separate, much smaller valve directly on the outlet line near the KR. The control valve should be briefly opened and closed after the KR has been adjusted; this will stabilize the pressure reading. Once satisfied with the set pressure, tighten the locking handle down to the adjustment head.
In general, KR pressure regulators with manual operation are not a precision device. There are large friction forces from the ShearFlo® seals, which are balanced by the operator springs. These constant movements within the regulator translate into observed pressure fluctuations that will not stabilize unless a control valve (just downstream of the KR) is briefly opened and closed as stated above. See the Troubleshooting section if there is excessive pressure fluctuation.
7- Series Installation
It is NOT recommended that KRs be installed in series (e.g. do NOT connect the outlet of one KR to the inlet of another). Doing so may prevent set pressure stabilization.
8- Pressure Relieving Feature
The KRs are designed to self-relieve (vent) at an over-pressurization condition to maintain the regulated set pressure. Thus, the vent port must always be connected without any restrictions and not joined with any other common returns to the reservoir or tank at ambient pressure (i.e. solo low pressure hydraulic hose or tubing from KR to tank) to ensure proper safety and function.
In the event of a supply seal ring or flow plate failure, the supply pressure will leak into the KR body through the vent seal ring port and then be directed to the reservoir or tank.
Call our technical support team for the most effective application and installation strategies.
KR Regulator Operation (How It Works)
Regulator at Set Pressure and No Flow:
When the KR is at the set pressure, the internal pressure and “Operator Force” are at equilibrium and there is no flow from the “Outlet.”
The “Operator Force,” which is acting on the piston, is balanced by internal pressure.
The “Inlet/Supply” pressure (red) is blocked and contained by the seal rings (in the seal container) that are sealing on the flow plates.
The internal regulator pressure and the “Outlet” port/piping are at the set pressure (blue), which is less than the Inlet/Supply pressure.
The “Vent” port is blocked and sealed by the vent seal ring.
Regulator at Full Flow Condition:
When the downstream pressure is suddenly reduced, the KR will allow full flow from the Inlet/Supply to the Outlet until the set pressure is reached.
The Outlet port/piping is connected to a hydraulic control valve. When actuated, the internal regulator pressure drops below the set pressure.
This pressure drop causes the Operator Force to push the piston (connected to the seal container) into the regulator body. The seal rings change position to uncover the ports on the flow plate, thus causing the Inlet/Supply pressure (red) to flow through the regulator to the Outlet port/piping.
The Vent port in the flow plate remains blocked and sealed by the vent seal ring.
Venting to Reservoir:
Venting of the regulator is caused either by excessive back pressure on the Outlet port from another source or by decreasing the set Operator Force (e.g. resetting the regulator to a reduced pressure).
If the regulator’s internal pressure exceeds the set pressure, it will cause the seal container and piston to move upwards against the set Operator Force.
The vent seal ring will move off the flow plate’s vent port and allow the pressure to be vented from the regulator body to the reservoir.
The Inlet/Supply port remains sealed.
Venting continues until the internal pressure reduces to a point that balances with the set Operator Force. Namely, the seal container and piston travel down until the vent seal ring covers and seals off the flow plate’s vent port to block venting.
Observation – Pressure fluctuations
1. Internal leak in KR from seal rings and/or flow plates
1. Inspect seal rings and flow plates for deep scratches and replace with repair kit (see maintenance manual)
2. Leak downstream from the KR
2. Check for leaks in piping and all components downstream of KR
3. Temperature fluctuations
3. Remedy as required
4. Back pressure from downstream equipment, BOP wellbore packer compression and well pressure rise
4. Remedy as required
5. Deadband range is too high for application
5. Replace KR or convert to lower deadband model (call PacSeal Hydraulics)
Observation – Intermittent flow from vent port with slow increase in outlet pressure
1. Back pressure from downstream equipment
1. Remedy as required
2. Leak from supply seal ring and/or supply flow plate
2. Replace supply seal ring(s) and/or flow plate(s) (see maintenance manual)
Observation – Flow from vent port with outlet pressure drop
1. Vent seal ring and/or flow plate damage
1. Replace vent seal ring(s) and/or flow plate(s) (see maintenance manual)
Observation – Leaks from flange(s)
1. O-ring failure
1. Replace O-ring (see maintenance manual)
2. Damaged sealing surface of body
2. Replace body (see maintenance manual)
3. Damaged sealing surface of flange O-ring groove
3. Replace flange
Observation – Desired outlet pressure cannot be reached
1. Worn-out operator springs (manual or failsafe air/hydraulic)