Do you understand these pressure regulating valves KVP, KVR, KVL, KVC, and KVD?

Overview:

The KV type pressure regulating valve will control the low and high pressure sides of the system under various load conditions:

KVP is used as the evaporation pressure regulating valve and KVR is used as the condensing pressure regulating valve. KVL serves as crankcase pressure regulating valve. KVC is used as a capacity regulating valve. The NRD is used as a differential pressure regulating valve and receiver pressure regulating valve. KVD serves as receiver pressure regulating valve. CPCE acts as a capacity regulating valve.

1. KVP evaporation pressure regulating valve

The KVP evaporation pressure regulating valve is installed in the suction line after the evaporator and is used to regulate the evaporation pressure of a refrigeration system containing one or more evaporators and a compressor. In such refrigeration systems (operating at different evaporating pressures), the KVP is installed after the evaporator with the highest evaporating pressure. Each evaporator is activated by a solenoid valve in the liquid line. Each compressor is controlled by a pressure switch in the pumping function. The maximum pressure on the suction side corresponds to the lowest room temperature.

In refrigeration systems with parallel coupled evaporators and common compressors requiring the same evaporation pressure, the KVP must be installed in the common suction line.

The KVP evaporation pressure regulating valve has a pressure gauge connection that can be used when setting the evaporation pressure. KVP maintains a constant pressure in the evaporator. The KVP will open when the inlet pressure (evaporation pressure) increases.

2. KVR condensing pressure regulating valve KVR is usually installed between the air-cooled condenser and the liquid reservoir. KVR maintains constant pressure in air-cooled condensers. The KVR will open when the inlet pressure (condensing pressure) increases. KVR together with KVD or NRD ensures a sufficiently high hydraulic pressure in the reservoir under different operating conditions. The KVR condensing pressure regulator valve has a pressure gauge connection that can be used when setting the condensing pressure.

Restarting a refrigeration system after a long shutdown period can be difficult when both the air-cooled condenser and receiver are placed in a very cold outdoor environment. In this case, the KVR is installed in front of the air-cooled condenser with an NRD in the bypass line surrounding the condenser. NRV prevents backflow during startup.

KVR can also be used in heat recovery applications. In this application, the KVR is installed between the heat recovery duct and the condenser. An NRV needs to be installed between the condenser and receiver to prevent reverse condensation of the liquid in the condenser.

In refrigeration systems with automatic defrost function, KVR can be used as a pressure relief valve. Here, the KVR is installed between the evaporator outlet pipe and the receiver. Notice! KVR should never be used as a safety valve.

3. KVL crankcase pressure regulating valve If the suction pressure becomes too high, the KVL crankcase pressure regulating valve will limit the operation and starting of the compressor. It is installed in the refrigeration system suction line immediately before the compressor. KVL is commonly used in refrigeration systems with hermetic or semi-hermetic compressors designed for low temperature conditions. When the outlet pressure (suction pressure) decreases, the KVL will open.

4. KVC capacity regulating valve

KVC is used for capacity regulation in refrigeration systems where low load conditions occur and where low suction pressure and "compressor cycling" need to be avoided. Too low suction pressure will also create a vacuum in the refrigeration system, which will create a risk of moisture ingress in refrigeration systems using open-mouth compressors. The KVC is usually installed in the bypass line between the compressor discharge and suction lines. The KVC will open when the outlet pressure (suction pressure) decreases.

If higher regulation accuracy and lower suction pressure are required, or if there is a higher pressure drop between the CPCE outlet and the suction pressure, a CPCE capacity regulating valve can be used instead of the KVC.

The KVC can also be installed in the bypass line of the compressor discharge pipe, with the valve outlet connected to a point between the expansion valve and the evaporator. This arrangement can be used in chillers that use multiple parallel-coupled compressors and do not use a liquid distributor.

5. KVD receiver pressure regulating valve KVD is used to maintain a sufficiently high receiver pressure in refrigeration systems with or without heat recovery. KVD for use with KVR condensing pressure regulator valve. The KVD receiver pressure regulating valve has a pressure gauge connection that can be used when setting the receiver pressure. The KVD will open when the outlet pressure (receiver pressure) drops.

6. Understanding and Installation All KV pressure regulating valves are equipped with a label describing the function and type of the valve, such as CRANKCASE PRESS.REGULATOR type KVL. The label also indicates the valve's operating range and maximum allowable working pressure (PS/MWP). A double arrow ("+" and "-") is printed on the bottom of the label. The direction "+" (plus sign) indicates higher pressure and the direction "–" (minus sign) indicates lower pressure. KV pressure regulating valves can be used with all existing refrigerants except ammonia (NH3) as long as the valve pressure range is not exceeded; the valve body is stamped with the valve size, e.g. KVP 15, and an arrow indicating the direction of valve flow.

Installation: Make sure the piping around the KV valve is clean and secure. This prevents the valve from vibrating. All KV pressure regulating valves must always be installed so that fluid flows in the direction of the arrow. Furthermore, KV pressure regulating valves can be installed in any position, but they must not create an oil or hydraulic lock. Welding: During installation and welding, the valve must be wrapped with a damp cloth. Always point the gas flame away from the valve so that the valve is not exposed to direct heat. When welding, be careful not to leave solder in the valve as this will damage the function of the valve. Before welding the KV valve, make sure all pressure gauge inserts have been removed. Inert gas must always be used when welding KV valves.

7. Evacuation and setting During the evacuation process of the refrigeration system, all KV valves must be opened. The factory setting positions of the KV valve are as follows: KVP, closed KVR, closed KVL, open KVC, open KVD, open therefore the setting levers of KVP and KVR need to be rotated counterclockwise during system draining. In individual cases, it may be necessary to vent simultaneously from the discharge and low-pressure sides of the refrigeration system. It is not recommended to vent through the pressure gauge connections of KVP, KVR and KVD as the holes in these ports are very small.

When setting up the KV pressure regulator valve in your refrigeration system, it is a good idea to use the factory settings as a starting point. The factory settings for an individual pressure regulator valve can again be obtained by measuring the distance from the top of the valve to the setting screw. The table shows the pressure change per revolution of the screw for factory settings, distance "x" and all KV model settings.

8. How to adjust and set 7.1 KVP evaporation pressure regulating valve: The factory setting of KVP evaporating pressure regulating valve is 2 bar. Clockwise rotation will provide higher pressure, while counterclockwise rotation will provide lower pressure. After the system has been running normally for a period of time, fine-tuning is required. A pressure gauge should always be used when making fine adjustments. If the KVP is used for frost protection, fine adjustments must be made with the system running at minimum load. Remember that the protective cap on the setting screw must be replaced after final setting.

8.2 KVL crankcase pressure regulating valve: The factory setting of the KVL crankcase pressure regulating valve is 2 bar. Clockwise rotation will provide higher pressure, while counterclockwise rotation will provide lower pressure. The factory setting is the point at which the KVL starts to open or just closes. Since the compressor must be protected, KVL should be set to the maximum allowable suction pressure of the compressor. Compressor suction pressure gauge must be used for setting.

8.3 KVR + NRD Condensing Pressure Regulator Valve In refrigeration systems using KVR + NRD, the KVR setting must give a suitable receiver pressure. The pressure in the condenser is allowed to be 1.4 to 3.0 bar (pressure drop in NRD) higher than the pressure in the receiver. If not allowed, the layout of KVR + KVR must be used. It is best to set this up during winter operation.

8.4 KVR + KVD condensing pressure regulating valve In the refrigeration system using KVR + KVD, the condensing pressure of KVR must be set first when KVD is closed (set the screw counterclockwise to the maximum). The KVD must then be set to the receiver pressure, for example 1 bar lower than the condensing pressure. A pressure gauge must be used during setup, and it is best to do this during winter operation. If you are setting the condensing pressure during summer operation, you can choose one of the following two methods: 1) In a newly installed refrigeration system with the KVR/KVD starting point set to 10 bar, you can set the number of screw turns by counting to set up the system. 2) In existing refrigeration systems where the KVR/KVD settings are unknown, the starting point must be established first. Then you can count and set the number of turns of the screw.

9 Summary

KVP
Evaporation pressure regulating valve
When the pressure on the inlet side increases
0-55 bar
KVR
Condensing pressure regulating valve
When the pressure on the inlet side increases
5-17.5 bar
KV
crankcase pressure regulating valve
When the outlet side pressure drops
0.2-6 bar!
KVC
Capacity regulating valve
When the outlet side pressure drops
0.2-6 bar
CPCE
Capacity regulating valve
When the outlet side pressure drops
0-6 bar
NRD
Differential pressure regulating valve
The valve begins to open when the pressure drop is 1.4 bar.
Fully open when pressure drop is 3 bar.
3-20 bar
KVD
Receiver pressure regulating valve
When the outlet side pressure drops
3-20 bar